Functionality of Food Additives

Abstract

Food incorporates a diverse array of nutrients, some of which are deliberately added for functional purposes, while others occur naturally in certain food items. When these compounds are present in processed foods, they are categorized as “food additives.” Regulatory oversight stipulates that each food additive must demonstrate a beneficial and justifiable function to validate its inclusion. Food additives are commonly utilized to achieve desirable objectives, including improved food preservation, elevated nutritional value, augmentation of functional attributes, facilitation of processing, and heightened consumer appeal. Regulatory frameworks strictly prohibit the use of food additives to deceive consumers or conceal food damage or deterioration. Moreover, the application of food additives is proscribed in circumstances where cost-effective, high-quality production methods can yield equivalent outcomes. Furthermore, the burgeoning awareness of the health benefits offered by specific dietary constituents has led to the commercial introduction of a wide spectrum of innovative food additives. Notably, many food additives have natural counterparts, and the commercial production of novel compounds utilizing natural resources continues to expand. This chapter furnishes an integrated perspective on the functionalities of food additives, centering on an exploration of their function and chemical properties within the realm of food.

1. Introduction

Since ancient times, human endeavors have centered on the optimization of sustenance. This pursuit has encompassed the refinement of hunting methodologies, the domestication of fauna and flora, the implementation of preservation techniques, and the introduction of food additives aimed at enhancing flavor and extending shelf life [1, 2]. During the 1800s, food additives were deliberately utilized to contaminate food supplies. The proliferation of this practice was influenced by the advent of analytical chemistry, centralization of food production, erosion of individual accountability, and inadequate governmental oversight [3]. The proliferation of unregulated food tampering posed a significant global challenge, as apprehensions regarding food quality steadily mounted. The advent of proficient food analysis methodologies and regulatory interventions served to diminish the salience of this issue by approximately 1920. Simultaneously, processed foods assumed a more substantial role in human nutrition during the mid-twentieth century [4]. As a result, legal chemical additives started to appear more frequently in these foods, leading to strict regulation that is still debatable because there have been many studies on food additives that have produced contradicting findings and different government interpretations. More than 2500 additives are purposefully added to food now in order to maintain specific qualities or increase shelf life, while many more have been outlawed over time—some worldwide, some solely in particular nations. Food additives are a well-established aspect of the food industry, with a definition that has evolved over time [5]. Nowadays, food additives refer to substances that are not typically consumed on their own or used as ingredients in food but are intentionally added to enhance the taste, texture, or appearance of food. These substances are used throughout the manufacturing, preparation, processing, treatment, packaging, transportation, and storage of food. As a result, food additives can become part of the food itself or affect its characteristics in various ways. The majority of food consumers are unable to consume food right away after it is created. A lot of food needs to be carried and kept. When preparing food, several food additives are employed to maintain the food’s quality. To improve the nutritional content of the food or to replenish nutrients lost during manufacturing, further additives are added. Foods are sold at marketplaces when some additives are added to improve the food’s look and sway the buyer [6, 7, 8].

Food additives are essential to modern humanity; in fact, the industrialized world could not have existed without them. It is rare for members of industrialized cultures to participate in the planting, gathering, and processing of the food they consume. This means that in order for processed food to reach customers, it must be carried across great distances [9]. Special precautions must be taken to guarantee that the food arrives at its destination in excellent shape, primarily to avoid contamination and spoiling. These specifications cover proper packaging, environmental factors, and the use of additives to maintain or improve certain properties [10, 11, 12]. While the body of knowledge on food additives, their effects on behavior and health, and how to identify them is expanding rapidly, there is still a great deal of conjecture, contradiction, dispute, and unanswered questions regarding health dangers. This is further reinforced by the increasing demand for novel and more potent chemicals, which is tightening laws to identify adulterations and overuse of certain compounds as soon as feasible. According to estimates from the US Centers for Disease Control and Prevention (CDC) from 2001, there are around 76 million foodborne disease cases and 5000 foodborne illness fatalities in the United States alone per year. It is estimated that the related costs of foodborne diseases caused by certain strains of bacteria range from 6.5 to 34.9 billion dollars. Authorities think the 100,000 instances that were documented in England and Wales during the same year are not correct, as many incidences went unreported [13].

The Council for Responsible Nutrition, which compares the FDA’s approval of new dietary ingredients to that of food additives—which undergo testing to a higher standard than the reasonable expectation of safety mandated by Congress—has accused the agency of developing an extremely stringent and unachievable draft guidance. After a review of the FDA’s exposure assessment procedures in 2011, it was determined that the organization needed to create a framework grounded in science to prioritize and re-evaluate earlier safety determinations, as well as carry out more thorough post-market monitoring and engage in stakeholder communication and scientific information exchange. Throughout 2008, the EFSA organized a scientific meeting to bring together experts throughout Europe to discuss topics related to food safety. According to the authority, consumer confidence has increased since the year 2002 when it was established when it was at a low point because of food-related problems in the 1990s [7, 8, 9, 13]. Food additives were seen as beneficial in that forum because of the role they played, yet occasionally they may be harmful to one’s health. The European Commission Regulation and EFSA have been conducting a program to reassess all currently authorized food additives since 2010 [14, 15].

Premarket testing of additives could not be sufficient to determine their safety for human use, leading to follow-up research and, if required, eventual prohibition when toxicity is established. The debate over some chemicals that are permitted in some nations but limited or outlawed in others, as well as public outcry over the use of animals in toxicological testing, all contribute to this. These and other causes lead to a mistrust of additives among certain consumers, which puts pressure on manufacturers to find natural alternatives to chemical additives—despite the fact that natural chemicals should, in theory, be treated the same as chemical ones [10, 15]. The general public’s ignorance about food additives has an impact on whether or not they are accepted.

There are numerous types of food additives, which can be classified into different groups such as preservatives, antimicrobials, antioxidants, minerals, vitamins, fibers, phytochemicals, probiotics, postbiotics, bioactive extracts from animals, and processing aids. These categories are discussed in detail in the present chapter, and include sequestrants or chelating agents, humectants, enzymes, and coating agents.

2. Overview of chemistry of food additives

2.1 Definition and regulation

The definition of a food additive may vary across jurisdictions, but it generally pertains to substances intentionally incorporated into food products to fulfill specific technological functions. Most jurisdictions maintain a publicly accessible list of permitted food additives that are deemed safe for human consumption under specified conditions. If a food additive is not included in the permitted list or its usage is restricted for a specific food item, individuals or entities seeking to use the additive must submit an application to the relevant regulatory agency for approval, adhering to the prescribed conditions and requirements [16].

It is essential to recognize that there exists no differentiation between naturally occurring compounds and synthetically derived compounds concerning global food additive regulations and safety evaluation requisites. Despite the prevailing belief in the inherent safety of natural compounds, empirical evidence does not substantiate this notion. Indeed, certain naturally transpiring compounds, such as ricin from the seeds of the castor oil plant, are among the most toxic known substances. The presence of naturally occurring toxins in food presents noteworthy food safety concerns for both human and animal consumption. Consequently, it is imperative that novel food additives originating from natural sources undergo rigorous safety assessments equivalent to those applied to synthetic compounds [17, 18].

In the United States, substances proposed for incorporation into food are subject to premarket approval, except when they qualify for specified exemptions. The 1958 Food Additive Amendments of the Federal Food, Drug and Cosmetic Act (FFDCA) necessitated the demonstration of the safety of food additives, while also providing exemptions for “grandfathered” ingredients. These encompassed food additives previously authorized for use in foods and those recognized as “generally recognized as safe” (GRAS) for use in food. Consequently, a new food additive is not necessitated to undergo premarket approval if it is deemed to be GRAS. This determination is made by experts possessing scientific training and experience who assess its safety under the intended conditions of use, through scientific procedures, or based on historical use prior to 1958. The criterion of “general recognition” of safety is frequently satisfied through peer-reviewed publications of pivotal safety data, although alternative methods are permissible. It is imperative to underscore that the GRAS determination of a compound is contingent upon its intended use and levels of use in specific foods, which ascertain the projected consumer exposure and safety. As a result, the specified use, and not the substance in general, is established as GRAS, whereas other uses are not [17, 18, 19, 20].

The absence of a comprehensive positive food additive list in the United States is attributed to the voluntary nature of FDA notification for GRAS determinations. Currently, no publicly available list exists for substances that have been “self-determined” to be GRAS without FDA notification. This lack of transparency gives rise to concerns regarding the number of food additives introduced into the US food supply through the self-determined GRAS process. Despite recommendations put forth in 2010 to address this matter, their full implementation has not materialized, thereby perpetuating deficiencies in the US FDA oversight of food additive safety and a lack of a complete positive list of food additives utilized within this jurisdiction [16, 21].

In Argentina and Brazil, the regulation of food additives falls under Mercosur standards (GMC 11/06, 34/10, and 35/10). Applicants seeking approval for new food additives are required to submit their applications to the Comisión Nacional de Alimentos (CONAL) or the Agência Nacional de Vigilância Sanitária, for Argentina and Brazil respectively. The aforementioned agencies are responsible for forwarding the applications to Mercosur’s Sub Work Group #3 for further processing. In Canada, any new food additives or modifications to the approved uses of existing additives under the Division of the Food and Drug Regulations must undergo a premarket assessment that primarily focuses on safety. Similarly, both Japan and China conduct safety assessments on all currently permitted food additives. The European Union has established guidelines for the evaluation of food additives by the European Food Safety Authority (EFSA) and for decision-making by the Commission. These guidelines are outlined in Regulation (EC) No. 1331/2008, which was adopted on December 16, 2010. This regulation sets forth a common authorization procedure for food additives, food enzymes, and food flavorings, aiming to enhance consistency in the procedural aspects of food additive approval across the EU [16, 18, 22].

For functional reasons, a variety of chemicals are added to food, and frequently, these components are also found in some foods naturally. Nevertheless, these substances are referred to be food additives when they are utilized in processed meals. Food additives, according to the FDA, are compounds that are added to food in order to achieve certain technical or physical effects. While they cannot be used to cover up low quality, they can help with processing and preservation or enhance the qualities of texture, flavor, appearance, and nutritional value [23].

Depending on how they are used in food, food additives in the EU are categorized into 26 functional classes: “preservatives,” colorants, sweeteners, acids, acidity regulators, carriers, antioxidants, anticaking agents, bulking agents, humectants, emulsifying salts, emulsifiers, firming agents, foaming agents, gelling agents, flavor enhancers, glazing agents, stabilizers, packing gases, thickeners, modified starches, propellants, sequestrants, raising agents, and flour treatment agents. The American method of handling food additives reduces the number of classifications and permits the mention of additives in two or more of them. According to the FDA, over 3000 food additives are permitted in the United States and are categorized into 6 groups: preservatives, nutritional additives, flavoring agents, coloring agents, texturizing agents, and miscellaneous agents [24].

Since many additives serve a variety of purposes and fall under many “functional” categories, it is necessary to identify the primary usage of the addition. Additionally, a negative list of chemicals that have been shown to be poisonous or to have bad impacts on human health has been produced; using any of the compounds on this list is strictly forbidden [25].

Food additives are categorized into functional groups according to the claimed technical function as stated in Regulation (EC) No 1333/2008, as was previously noted. In general, food additives’ roles may be summed up in four main categories:

• Food protection: antioxidants and antimicrobials

• Dyes: recovery or enhancement of natural colors; achievement of special colors

• Sugar substitution (intense sweeteners)

• Structure and technology: gelling agents, thickeners, and stabilizers.

3. Functions and safety considerations of food additives

Figure 1 provides an overview of different food additives by functional classes in terms of relative percentage. An additive is categorized according to its function in food. It is not uncommon for an add-on to be used for several purposes. It is difficult to enumerate every additive that is utilized worldwide due to its wide variety (Figure 2). Consequently, this chapter discusses the most widely utilized ones that are frequently employed as food additives.

Figure 1.

Different food additives used in food industries.

Figure 2.

Relative percentage of each type of food additives used in food industries. Reprinted from Ref. [8] with permission.

3.1 Antimicrobial agents

Food can change significantly, either in form or quality, if it is not eaten right away after processing. The majority of the time, internal enzymatic development, oxygen, or bacteria are the main causes of quality degradation. Foods can be preserved via refrigeration, cooling, freezing, heating, drying, airtight packing, and fermentation to maintain their shape and quality for a certain amount of time during storage and transportation (Figure 3) [27, 28]. But occasionally, these methods are insufficient, and chemicals must be added in order to preserve the food. Chemicals are frequently applied to enhance the preservation that comes from a certain treatment. Preservatives are used to stop microorganisms including yeast, fungus, molds, bacteria, and others from causing spoiling [29]. Natural preservatives are rapidly replacing artificial preservatives, which are widely used yet may be carcinogenic. Ancient people were aware that preserving food may be achieved by adding sugar and salt. Since microbes cannot survive without adequate water to exist, they work as preservatives by killing bacteria and many other organisms by decreasing the amount of water in the food. Nonetheless, the meal has to have a lot of salt or sugar in order to be preserved over time. When food is prepared using a lot of salt or sugar, it takes on a different shape called salted or preserved food. Therefore, salt and sugar are not thought of as preservatives but rather as important elements in this meal form. Wood smoke is another preservative. In addition to fuming, the smoke leaves behind a number of preservative-acting compounds on the food. It would be more reasonable to refer to wood smoke as food processing instead of preservation when discussing fuming [30]. Foods are nutrient-rich materials that draw a wide range of microbes, which infiltrate and then consume the meal. A particular preservation ingredient may be effective against a narrow range of food pathogens. It is hard to identify a single substance that can eradicate every microbe or prevent it from feasting on the meal, though. The gross impact of an antibiotic in a preservative is selected based on a number of parameters, including cost, ease of application, pH range of maximum effectiveness, and solubility in water [31].

Figure 3.

Perceptual relationship of each class of antimicrobial agents as food additives for use in food industries. Reprinted from Ref. [26] with permission.

Antimicrobial agents are used in food for two reasons: (1) to prevent or minimize contamination by microorganisms, especially pathogenic ones (which represent a risk to food safety) and/or (2) to manage natural food decomposition. In food with quantum satis status, potassium acetate (E261), acetic acid (E260), calcium acetate (E263), carbon dioxide (E209), lactic acid (E270), and malic acid (E296) are the primary chemical antimicrobials utilized. Sorbic acid and sorbates (E200-E209; ADI 25 mg/kg bw), benzoic acid and benzoates (E210-E219; ADI 5 mg/kg bw), nitrites (potassium nitrite E249; ADI 0.07 mg/kg bw, sodium nitrite E250; ADI 0.1 mg/kg bw), propionic acid and propionates (E280-E289; quantum satis), parabens (E214-E219; ADI 10 mg/kg bw), and nitrates (sodium nitrate E251 and potassium nitrate E252; both with ADI 3.7 mg/kg bw) are the antimicrobial additives with restricted uses [5].

Preservatives and other antimicrobial additions have been shown to affect the mechanisms of nutrition transport in bacteria as well as their cell walls, membranes, DNA, and enzyme function [32]. On some occasions, the combined actions of these systems may cause harmful organisms and spoilage to completely disappear from food. Aside from their direct bactericidal effect, several additives inhibit the development of microorganisms by decreasing water activity, changing the pH of the solution, or blocking food from getting oxygen [33]. However, the dose-effect interaction alone affects how effective preservatives are. As a result, a workable food preservation system must include sufficient preservatives. It is also critical to remember that not all pathogenic organisms and spoiling agents can be effectively combated by preservatives. Furthermore, a number of food-related parameters, such as water activity, pH, solubility, food components, and substrate redox potential, affect a preservative’s antimicrobial potency [34, 35].

3.2 Antioxidants

The term “antioxidant” has two different meanings: strict chemistry, which defines it as any material that interacts with an oxidant when it is a reductant, or more loose definitions, such as the one provided by the Britannica Encyclopedia: Antioxidants are any of a wide range of chemical compounds that are added to some foods, gasoline, rubbers, both natural and manufactured and other substances to slow down the process of autoxidation, which is the reaction of these substances with oxygen in the air at room temperature [36, 37, 38]. Delaying autoxidation prevents the emergence of undesired properties including gum development in gasoline, elasticity loss in rubber, and rancidity in food [39]. The most widely utilized organic antioxidants include phenols, aminophenols, and aromatic amines. In the former case, the labels “oxidant” and “antioxidant” are relative, since a given chemical might be either depending on which molecule is the “other” one that is interacting. This does not imply that any material involved in a reduction-oxidation (REDOX) reaction possesses the calculable standard reduction potential (ε0). In conclusion, preservatives are employed in the food business to stop food from spoiling, and antioxidants stop chemical reactions that cause bad taste and/or odor [40]. Figure 4 shows the mechanisms of antioxidant action and free radicals and the relationship between antioxidants.

Figure 4.

Understanding mechanisms of antioxidant action (a), free radicals and antioxidants relationship (b).

An antioxidant’s ability to trap free radicals allows it to scavenge peroxy radicals, interact with oxygen singlets, and quench photosensitive chemicals. The majority of chronic illnesses, including diabetes, cancer, heart disease, and autoimmune diseases, are linked to the existence of free radicals. Microbial pigments have demonstrated potential beneficial effects when added to food goods as possible antioxidants [41]. Because of their biological roles, carotenoids, napthaquinone, and violacein have all shown antioxidant qualities. Similarly, by preventing photodynamic lipid peroxidation in liposomes, the microbial pigment xanthomonadin has antioxidant properties.

The antioxidant pigments lutein, zeaxanthin, and xanthophylls, which are present in maize, kale, and spinach, are essential in preventing age-related macular degeneration (AMRD), the primary cause of blindness in the human retina. Because of its extremely high level of antioxidants, astaxanthin helps prevent cataracts, boosts immunity, and is bioactive against Helicobacter pylori [42]. Cardiovascular disorders (CVD) have been prevented by using carotenoids, which also strengthen the immune system, protect against sunburns, and slow the growth of some tumors. According to a recent study, a carotenoid that was separated from M. roseus and M. luteus for the first time showed potential for antioxidant, antibacterial, and UV protection [43]. In a similar vein, lycopene protects heart illnesses and arteriosclerosis by assisting in the oxidation of low-density lipoprotein (LDL) cholesterol. One significant anticancer microbial pigment is prodigiosin [44].

Whereas benzoic acid (or benzoate salts) and sorbic acid (or sorbate salts) are pure preservatives, ascorbic acid (vitamin C) is a pure antioxidant. Why sodium sulfite is regarded as a preservative and propyl gallate as an antioxidant is not entirely evident, though. Both sulfites and bisulfites, which are also listed as preservatives, can be thought of as in vivo antioxidants since they oxidize to sulfates and bisulfates, respectively. Stated differently, they function similarly to antioxidants in the context of food preservation. It is true that sulfites may have other functions, such as preventing undesirable enzymatic reactions in food and drink. It is interesting to talk about toxicity statistics at this time. In this regard, we contend that while dosage matters and that some antioxidants are safe at certain concentrations, food additives are generally harmless. This view based on evidence may undoubtedly be extended to food preservatives [45, 46].

Since many years ago, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) have been used extensively as antioxidants to maintain and stabilize the flavor, color, freshness, and nutritional content of food and animal feed products. It is stated that BHT is approved for usage as a direct or indirect food ingredient in about 40 countries. As food additives, BHA and BHT are now approved by the US Food and Drug Administration (FDA). On BHA and BHT, several experimental investigations have been published. After evaluating BHA, the International Agency for Research on Cancer (IARC) discovered enough evidence of the chemical’s carcinogenicity in experimental animals but no information for people. The assessment of BHT came to the conclusion that there was no data about BHT’s carcinogenicity in humans and very weak evidence in experimental animals. BHA has been shown to cause forestomach squamous cell carcinomas in mice at high dosages above 3000 ppm, but not glandular cell or other forms of neoplasms in the glandular stomach. Since BHA is not DNA-reactive, tumor promotion appears to be a part of the epigenetic process underlying the creation of tumors [5, 47]. The idea that BHA consumed in diets at levels higher than 3000 parts per million results in cellular damage and proliferation in the stomach, two important processes that underlie the development of cancer, is supported by experimental research. Moreover, BHA prevents communication between cells. Since humans lack a forestomach, it is anticipated that their sensitivity to the effects of BHA will be far lower than that of rats. Furthermore, human doses are far lower than those in rats that cause epigenetic consequences like cell proliferation. Therefore, we draw the conclusion that BHA is a rodent carcinogen that, for all intents and purposes, is unique to rodents and unrelated to humans. Furthermore, the lowest impact threshold for hyperplasia in rats, 230 mg/kg/day, is far below human doses (<0.1 mg/kg/day), which is the most sensitive effect linked to forestomach cancer. This validates the judgments made by the authorities that examined the evidence and suggested that BHA be used indefinitely, even though the International Agency for Research on Cancer concluded that BHA may cause cancer in people. Moreover, BHA has anticarcinogenic qualities at doses as low as 125 ppm, which is closer to levels seen in food additives [48]. Consequently, we draw the conclusion that, at the levels of food additives currently used, BHA and BHT pose no cancer risk and may even be preventing cancer in humans [48]. Antioxidants include sodium salts of citric, ascorbic, and erythorbic acids. They are all soluble in water. The isomer of ascorbic acid is erythorbic acid, also referred to as isoascorbic acid. It is favored in situations when the meal does not require active vitamins since it is less costly [47]. By chelating trace metals, citric acid prevents the catalytic autoxidation degradation of those metals. Oxygen is scavenged by ascorbic and erythorbic acids. These salts and acids are used in beer, wine, fruits, vegetables, seafood, fresh meats, dairy, and dairy products to stop trimethylamine from oxidizing or developing and changing the color or developing a bad odor. These acids speed up the process of curing meat with nitrite. Shrimp are also treated with ascorbic acid to prevent blackening. Oil-soluble ascorbyl palmitate is a component of vitamin-rich products [7, 45, 46, 49].

3.3 Acids, bases, buffer systems, and salts

Almost all fruits naturally contain acids, which add to their tartness and acidity. Acids increase appetite by influencing the olfactory nerve, which makes one want to eat more. Therefore, it takes the sophisticated ability to formulate a food product such that the optimum acid and quantity are chosen to get the intended physiological and psychological effects. The acids that are most frequently utilized in the food sector are phosphoric, tartaric, citric, malic, and lactic. All citrus fruit products pair well with citric acid; colas benefit from the addition of tartaric acid to give them a grape flavor; and malic acid is typically used to improve flavor. It is required to add acids to a broad range of foods, such as drinks, preserves, jams, jellies, bakery goods, candies, chewing gum, and dairy products, in order to enhance the activity of the natural acid components or to alter pH for optimal flavor. One way to buffer an acidic pH is to add a matching salt, most often sodium [8, 50, 51, 52, 53, 54, 55].

Lactic acid has been utilized since the beginning of human history and is frequently found in nature, particularly in milk and fermented foods. The acid is present in both D- and L-stereoisomers since it is a viscous liquid, although the food sector often employs the DL racemic combination. Spanish olive packaging, dairy goods, wine, and frozen desserts all include lactic acid, a somewhat acidic ingredient [5, 56].

The human body, as well as plants and animals, contain citric acid, which serves as a mediator in the respiration and energy metabolism processes. For more than a century, food processing has employed it. Approximately 60% of the global market contains it. Tribasic citric acid is mostly utilized in fruit juices, concentrates, syrups, cordials, and citrus-type drinks, particularly carbonated orange, lemon, and lime drinks. Citric acid is a need for candies, chewing gum, sweets, ice creams, jams, and jellies. It is also useful for cottage cheese, mayonnaise, cheese, and meat curing. Sodium citrate and citric acid are frequently combined to buffer pH levels. The primary fermentation process that yields citric acid involves maize sugars or molasses. It can also be produced by fermenting the yeast Yarrowia lipolytica to produce raw glycerol [5, 57].

Many fruits and vegetables, including apples, contain malic acid. Its acidulating qualities are similar to those of citric acid but gradually acquire that tart flavor. Usually, malic acid is combined with citric acid to lessen the astringent flavor of food and make it taste more smooth and organic [3].

Natural sources of tartaric acid include grapes, limes, currants, gooseberries, raspberries, and many other fruits. When coupled with citric acid, tartaric acid enhances the flavor of fruit drinks, preserves, jellies, sherbet, and cakes. In the baking business, monopotassium bitartrate, sometimes marketed as a cream of tartar, is a potassium salt that is frequently used as a leavening agent. The crushed cake of unfermented grape juice created throughout the wine-making process is where the majority of tartaric acid is generated [3, 58].

The sole inorganic acid utilized in the food business is phosphoric acid, which is also perhaps the least expensive acidulant that can give food the necessary acidity. It is mostly used at a concentration of a few hundred parts per million in carbonated drinks, especially colas, root beer, and sarsaparilla. Additionally, some dairy products like cheese include it. The acid is made by reacting sulfuric acid with phosphorus-containing rock to generate elemental phosphorus, which is then reduced to phosphorus pentoxide. This compound is then hydrated to make 75–85% phosphoric acid, and the acid is then purified to a commercial grade of 75, 80, or 85% [24, 59].

Acetic acid, fumaric acid, adipic acid, tannic acid, and glucono delta-lactone (GDL) are some other acids. Although vinegar, which has acetic acid as a key constituent, is frequently added to food, acetic acid is not utilized directly in food. Although it is uncommon, bakers occasionally utilize adipic acid in place of tartaric acid to prolong the taste notes. Since fumaric acid is more “tart” than citric acid and is a structural isomer of maleic acid, it can be used in place of tartaric acid. Bean curd (tofu) and various cheeses are made using GDL, which is the inner ester of gluconic acid and is created when glucose oxidizes [23].

Mechanisms of Resistance Several foodborne bacteria have inherent and adaptive resistance mechanisms to acid stress encountered during food preparation, despite their susceptibility to organic acids. For instance, the ability to withstand acidity is essential for the survival of enterohemorrhagic Escherichia coli (EHEC), a common foodborne pathogen that can survive in a variety of foods including the digestive system of cows. There are three different systems that exist in the acidic environment caused by low pH. In oxidatively metabolizing bacterial cells, acid tolerance at a pH of 2.5 requires the sigma factor S (σS) and the global regulatory protein known as the cAMP receptor protein. However, unless the medium is supplemented with either glutamate (glutamate-dependent acid resistance) or arginine (arginine-dependent acid resistance), cells grown on minimal media containing glucose cannot survive when exposed to pH 2.5. A variety of amino acid decarboxylase and antiporter enzymes regulate the final two systems [7, 60].

3.4 Chelating agents

Through the formation of coordinating bonds, sequestrants and chelating agents inhibit the activities of other materials in solution, often metals. Sodium hexametaphosphate (SHMP) and ethylene diamine tetra-acetic acid and its salts (EDTA) are the usual agents. To prevent the formation of metallic salts in liquid foods like salad dressings and canned goods, EDTA chelates copper and iron. The formula for SHMP, a long-chain polyphosphate salt, is (NaPO4)6. Because potassium compounds are tetrahedra, they organize geometrically in solution so that three phosphate groups are near one metal ion to create a complex. To prevent the formation of metallic salts in liquid foods like salad dressings and canned goods, EDTA chelates copper and iron. The formula for SHMP, a long-chain polyphosphate salt, is (NaPO4)6. Because potassium compounds are tetrahedra, they organize geometrically in solution so that three phosphate groups are near one metal ion to create a complex. Sequestrants include a wide range of acids and their salts [5, 61, 62]. The efficacy of malic, citric, tartaric, and lactic acids to stop precipitation in fish sauce from sand lance was studied; it was discovered that citric acid worked best in this regard. To increase the solubility of mineral elements in oat flakes, the effects of six possible chelating agents (citric, lactic, malic, and ascorbic acids, glucose, and xylitol) were examined; the most effective chelating agent was found to be citric acid [8, 63].

Free metal ions in food systems can precipitate, discolor, rancidify, or degrade food components by catalyzing the formation of insoluble or colored compounds or by causing food components to break down. Chelating agents work by combining with free metal ions to generate stable, generally water-soluble complexes that reduce these unwanted effects. The complexes that result from this process are known as chelates, and the impact is known as chelation. The regulated release of metal ions for dietary purposes or for the purpose of controlling the gelation of thickeners is another use of chelating agents. The stability constant K indicates the ratio of chelated to unchelated metal ions. The stability constant will increase with the chelating agent’s affinity for a given metal ion. The majority of EDTA dosages are the highest that the FDA has approved. Certain chelating agents are not permitted to be used in all nations [64, 65].

3.5 Stabilizers and thickeners

Several natural raw material sources, such as terrestrial and marine plants, microbes, and animal connective tissues, are used to make stabilizers and thickeners. These popular hydrocolloids come from various sources and are traditionally used as food thickening agents: animal derived (gelatin, chitosan, and isinglass); fermentation produced (xanthan, curdlan, and gellan); plant fragments (pectin, cellulose); seaweed extracts (carrageenan, agar, and alginate); seed flours (guar gum, locust bean gum (LBG), tara, and Cassia tora); and tree exudates (GA, tragacanth, karaya). The main food additives that greatly affect how different food items have a given texture are thickening and stabilizing agents. They give food items shape, flow, stability, and eating characteristics in addition to controlling moisture [66, 67]. The concentration of the active compound, temperature, degree of dispersion, dissolution, electrical charge, prior thermal and mechanical treatment, presence or absence of other lyophilic colloids, and the presence of electrolytes and non-electrolytes are some of the variables that affect the rheological properties of thickeners in any given solution [68, 69]. The molecular interactions among macromolecules inside the organized matrix have an impact on them. Due to growing concerns about the quality of life, consumers are increasingly becoming more interested in natural goods that have health-promoting properties. The food industry has seized this chance to offer items with useful qualities to a broad market. There have been encouraging studies published about the potential of hydrocolloids to reduce blood cholesterol, improve immunological function, and reduce the risk of cardiovascular disease. Food thickeners and stabilizers are complex materials with varying compositions and structures that can display a broad spectrum of rheological characteristics depending on the circumstances and concentrations. In the food industry, stabilizers, emulsifiers, thickeners, and gelling agents are more commonly referred to as food hydrocolloids. These biopolymers are soluble in water and comprise polysaccharides with greater molecular weight [70, 71, 72].

In chemical terms, hydrocolloids are simple polysaccharides (such as gelatin) or proteins (such as GA, guar gum, carboxy-methylcellulose, carrageenan, starch, and pectin) that when hydrated, may form viscous liquids. One of the most popular food thickeners in culinary applications is hydrocolloids. The creation of sauces, creams, toppings, gravies, soups, and salad dressings are among the widely used culinary applications [73]. All hydrocolloids have this characteristic of thickening water, which is the main use for them. The majority of commercial thickeners on the market are polysaccharides, and even at very low concentrations, the thickening qualities come from the way these high-molecular-weight molecules swell in solution. These long-chain polysaccharide molecules are typically seen in solution as conformationally disordered “random coils” whose shapes are constantly changing due to Brownian motion. The random, uncontrollable motion of molecules in a fluid due to constant molecular collisions is known as Brownian motion. However, the exact dimensions of the coil—that is, how compact or expansive it is—depend on the polymer chain’s monosaccharide composition and, more precisely, the kinds of links that connect the chain’s residues. Furthermore, there are four ways in which thickeners function in emulsions: (A) stabilizing an emulsion with a high volume percentage of the internal phase; (B) raising the external phase’s viscosity; (C) creating an elastic network within the external phase; and (D) removing a portion of the external phase. Mayonnaise serves as an illustration of how to stabilize an emulsion; the egg yolk lipoprotein in the sauce maintains the oil-in-water emulsion, which makes up more than 70% of the overall volume [61, 74]. The high viscosity and texture of the finished product are caused by a decrease in the amount of mobile exterior phase (free water, in a non-thermodynamic sense) and an increase in the relative amount of immobilized water surrounding the surface as the particle size of the oil droplets decreases. Some gums have the ability to create very viscous aqueous solutions; when these solutions are used in lieu of water in food formulations, the end product’s viscosity corresponds with the gum solution’s viscosity. For instance, increasing the viscosity in the aqueous phase of salad dressing compositions slows down the pace at which the oil droplets created during shaking float and stabilizes the emulsion. Commercial batters for cake, cake donut, and fish breading need a certain viscosity to perform at their best. Gums may be used to add and regulate viscosity to batters [75, 76].

Food thickeners come from a variety of natural raw material sources, such as connective tissues from animals, microbes, marine plants, and land plants. They fall into four major categories: plant-based, microbe-based, gum-based, and protein-based (Figure 5).

Figure 5.

Different types of food thickeners come from a variety of natural raw material sources.

3.6 Sweeteners

The food business seeks out novel methods to entice people to consume its goods in a profit-driven environment, with minimal consideration given to the possible health consequences of consuming many food items over the course of a day. Since it has long been recognized that consuming too much sugar may have negative effects on people, sweeteners first came into being in the 1800s as a way to cut back on sugar intake [77]. Sweeteners have evolved significantly since their invention. Although at one point they were considered among the food industry’s greatest successes, a number of disputes, contradictory rules, and legal actions have led to the perception that sweeteners are unreliable substances that are added to food to increase its sweetness. Sweeteners are widely used in food products due to the rising incidence of disorders linked to sugar intake [78]. Their effects on sweetening potential, health, economics, and social studies are being extensively studied. The sweetness of sweeteners is by far the most significant factor; it is assessed in proportion to sucrose, the standard sugar. Therefore, at 20°C, a solution containing 30 g/L has a sweetening power of 1, and the lowest concentration required to detect sugar is 1–4 mM. The chemical must dissolve in saliva and come into touch with the tongue’s receptors for the strength of the sweet flavor to be detected. The presence of various chemicals that can affect receptors, pH, temperature of perception, and sugar structure—which shows a drop in intensity as the amount of monosaccharides increases—all have an impact on the sweetness of the flavor [3, 79].

By their inherent qualities or place of origin, sweeteners can be categorized as both permissible food additives and non-additives. The three most popular categories are based on provenance, nutritional content, and sweetening ability. As a result, they may be separated into two categories: natural and synthetic origin, as well as intense and nutritious sweeteners. The distinction between natural and synthetic food additives is based only on the sweetener’s place of origin, even though regulatory authorities such as the European Food Safety Authority of the European Union (EFSA) employ the former categorization [80, 81, 82].

The most common table sugar, sometimes referred to as sugar or sucrose, is a disaccharide and the most widely used sweetener worldwide. It is made up of a glucose molecule with an aldehyde carbon attached to a fructose ketone one, creating a b (1,2) bond that prevents any reducing characteristics and forms a sufficient structure to connect to taste bud receptors, giving it the characteristically sweet flavor. Since this sugar serves as a substrate for bacteria like Streptococcus mutans and S. sanguis, which use it to convert it to pyruvic, acetic, and lactic acid, which dissolve tooth enamel and promote bacterial colonization, the link between its consumption and dental decay has long been known. Moreover, certain diabetic individuals run the risk of developing hormonal issues due to the rapid absorption of sugar, which can cause glycemic spikes. Sugar intake is also linked to other illnesses and conditions, such as type II diabetes, insulin resistance, hypertriglyceridemia, metabolic syndrome, breast and colon cancer, obesity, pediatric obesity, hypertension, and renal problems [57, 83].

Sucrose, sometimes known as sugar, is a common sweetener that can be found in practically all foods. Glucose, the life force, is produced when sucrose is digested in the stomach after it is absorbed. Regrettably, excessive sugar or glucose consumption can lead to major chronic illnesses including obesity and diabetes mellitus. The main cause of dental caries is thought to be Streptococcus mutans, which also greatly increases the virulence of dental plaque, particularly when sugar is present. Sugar alternatives prevent Streptococcus mutans from forming biofilms. Therefore, substituting other sweeteners for sugar in food is a significant problem in the food manufacturing process. Sugar is used in food composition not only for bulking but also for sweetening. Important additional factors in food preparation include controlling humidity and viscosity. Both polyols and artificial or natural strong sweeteners have particular functions when used in place of sugar. First, an appropriate bulking substance (polyols are an excellent alternative) needs to be chosen to replace the volume of sugar. Next, an artificial or natural strong sweetener is selected to give the necessary sweetness because polyols are not as sweet as sugar. It is also advised to add a tiny quantity of hydrocolloids to modify the viscosity and moisture [57, 61, 82, 84].

Polyols are a class of low-calorie, easily digested carbohydrates that resemble sugar. Aldehydes are replaced with hydroxyl groups found in polyols. They are created by certain algae, fungi, yeasts, and bacteria and can be found naturally in fruits and vegetables. Although they are made in the food business by catalytically hydrogenating natural sugars, lactic acid bacteria (LAB) generation in biotechnology has been studied as a potential substitute [85, 86].

The U.S. FDA has only allowed a few handful of highly concentrated artificial sweeteners—acesulfame potassium, aspartame, neotame, saccharin, and sucralose—for use as industrial alternatives for sucrose. Relative sweetness (RS), or the isosweetness concentration of these sweeteners relative to sucrose, varies depending on the kind of meal that contains them. In an analysis of a chocolate formulation, the isosweetness of neotame, sucralose, and natural rebaudioside (from stevia) were found to be 8600, 570, and 200, respectively. These values are comparable to those of other foods [57, 82].

The chemicals obtained from monk fruit and the South American plant Stevia rebaudiana are becoming increasingly common since they are natural products. A variety of diterpene glycosides known as steviosides are found in stevia plant leaves, with rebaudioside A being the sweetener of commercial importance. Rebaudioside A has an RS that varies from 30 to 45. Despite having a slight bitter aftertaste, it tastes clean. Mogroside, a triterpene glycoside that is isolated from the monk fruit Siraitia grosvenorii, is becoming more and more well-liked. Luo han guo is another name for monk fruit, which is a popular Chinese herb [83, 87].

The assessment of the sweeteners’ safety has been conducted in compliance with globally recognized guidelines for evaluating food additive safety. In 1987, JECFA released guidelines for evaluating food additive safety. In 1980, the SCF released its first set of guidelines for evaluating the safety of food additives, and it was amended in 2001. The AFC Panel and its successor, the ANS Panel, under the EFSA officially approved the 2001 SCF guidelines. Nonetheless, the ANS Panel has since created a new set of guidelines. The guideline paper offers recommendations on what information is required to assess a chemical’s safety before it is used as a food additive [88, 89].

3.7 Texturizers

Hydrocolloids are food texturizing agents, just like starches. They do, however, have different behavior and functions and are utilized in far lesser quantities. Food safety and palatability depend on texture, and hydrocolloids are key players in texture regulation. In actuality, starches and hydrocolloids work well together when combined, however, the amylose concentration of the starch influences pasting, paste, and gel qualities more so than the hydrocolloid that is added. Another name for hydrocolloids is gums. They have a significant water-binding property and are dispersible in water. When a gum ball is submerged in water, it instantly changes its rheology by either gelling or becoming more viscous [90, 91]. A high aqueous viscosity in food enhances volume, inhibits the formation of ice crystals, and promotes water or moisture retention, particle suspension, emulsion, and foam stability. The resulting gel stabilizes the freeze-thaw cycle and regulates the motion of water molecules. Similar to starches, hydrocolloids are polysaccharides; however, unlike starch in AGU, the complex monosaccharides glucose, mannose, galactose, arabinose, and rhamnose make up the chemical makeup of different gums. Certain monosaccharides have either a positive or negative charge associated with them [92, 93]. Every monosaccharide has distinct qualities that affect how well it works and is applied in food texturization. Hydrocolloids are derived from a variety of plant materials, including fruits, seeds, tubers, seaweeds, tree exudates, and microbes. Some hydrocolloids are also produced by chemically modifying wood pulp. Hydrocolloids are found in nearly every food type that contains water; but, because they do not contain enough water to operate, they cannot be found in chocolate, chewing gum, or edible oil. Due to their potent ability to bind water, hydrocolloids are often added to food in very tiny amounts—between 0.05 and 0.2%. Hydrocolloids are frequently found in dairy products like yogurt, cheese, ice cream, whipping cream, pudding, and water gel; desserts like water gel and smoothies; sauces and dressings; frozen foods; snacks; and meat products and their analogs. They are also frequently found in bakery products like dough conditioners, glazes, and pie filling. Gums are one of the most widely used agents that are used as hydrocolloid compounds and participate in texturizers in food [94, 95].

Gum Arabic (GA) is another name for gum acacia. It is taken from the actual exudates of the Sudanese shrub Acacia senegal. GA got its name because Arabs traded the gum throughout the Middle Ages. Glycoproteins and the polysaccharides arabinose, galactose, rhamnose, and glucuronic acid combine to form gum acacia. Its remarkable adhesive capabilities make it helpful in gum drop-type sweets, and its extraordinarily low aqueous viscosity makes it useable in high-protein beverages. Gum acacia is used as an emulsifier in citrus drinks that contain citrus oil [96, 97, 98].

Galactomannans belong to the family of seed gums. Commercially, they are manufactured in Canada, the Mediterranean region, South America, and South Asia, and they include fenugreek gum, guar gum, tara gum, and LBG. The backbone of all gums is polymannose, which is formed by α-1,4 bonds. The side chain of galactopyranose, which is α-1,6, links to mannose in varying ratios. Gums from seeds have different qualities. LBG dissolves in hot water, while fenugreek and tara gums dissolve in cold water. While tara gum and LBG react with xanthan, carrageenan, and konjac to generate gels of varying strengths, fenugreek and guar gums are unable to form a gel. Guar gum is used to give sauces and gravies a higher viscosity. Guar and xanthan viscosities complement each other so well that they are utilized in gluten-free flour to fortify the air cells inside the flour matrix. LBG is helpful in jelly, either by itself or in conjunction with xanthan, because of its antisyneresis characteristic. When guar gum and LBG are scarce, tara gum might be used in their stead. Fenugreek gum is usually used in herbal beverages because it contains amino acids that make the body more sensitive to insulin [99, 100, 101].

Pectin is another compound that can be used as a texturizer in various foods. Pectin is derived from apple pomace and the peel albedo and lamella of citrus fruits, primarily lemon and lime. This hydrocolloid has a molecular weight of 20,000–40,000 and is made up of partial methyl esters of polygalacturonic acids with galactose, xylose, and arabinose as side chains. After being extracted, it is considered high-methoxyl pectin (HMP) as it is 70–75% esterified. Acid hydrolysis leads to de-esterification [102, 103]. Reduced esterification (less than 50%) results in low-methoxyl pectin (LMP). Alkaline hydrolysis may be performed at low temperatures. Certain ester groups are changed into acid amide groups when ammonia is present, and the pectin is then classified as amidated (AM). When heated to a high temperature, HMP dissolves in hot water and solidifies into gels with a sugar content of 65 brix. They go into fruity jellies, marmalades, and jams. Humans are sensitive to concentrations as low as a few parts per million of pectin; HMP in food provides a feeling of fullness in terms of mouthfeel. It is also utilized in yogurt, where the milk protein does not coagulate when the acidity of the lactic acid bacterial culture drops below its isoelectric point due to the positive charges in the pectin [96, 97, 104].

3.8 Emulsifiers

Emulsions are defined by the way the aqueous (water) and oil phases are distributed in space once they have formed. The other liquid is referred to as the continuous phase, and the scattered liquid as the dispersion phase. The dispersion of fat droplets in a water continuous phase, such as mayonnaise or milk, is referred to as an oil-in-water emulsion. On the other hand, fat and water combine to produce a water-in-oil emulsion, which is what happens in butter and vinaigrettes [68, 105]. Ultimately, multilayer emulsions come in two varieties. In contrast to an oil-water-oil emulsion, which represents an oil continuous phase with a water-dispersed phase having an oil core, a water-oil-water emulsion explains a water continuous phase and an oil-dispersed phase, but the oil additionally contains another water phase in its core. With the added benefit of increased stability, these multilayer emulsions are made by treating the liquids to obtain tiny particle sizes [106, 107]. According to Codex Alimentarius, food additive emulsifiers are substances added to food that create or preserve a consistent emulsion of two or more phases. Emulsifiers for food additives possess both hydrophilic and hydrophobic moieties, which lower the interfacial tension between the water and oil phases and stop the processes from happening to suspended droplets in the emulsion. Emulsifiers for food additives come in a wide variety and have different chemical structures (Table 1). Although emulsifier types and structures are not widely recognized, some have loosely divided them into three classes: (1) small-molecule surfactants, also known as low-molecular-weight emulsifiers; (2) amphiphilic biopolymers; and (3) solid or colloidal particles [47, 108].

Emulsifier	Common name	HLB
Phospholipids	PL	6–10
Monoglycerides 2–	MG	5
Acetic acid esters of MG	ACETEM	7–8
Lactic acid ester of MG	LACTEM	7–8
Acetylated Monoglycerides	AMG	3–4
Lactylated Monoglycerides	LMG	10–12
Citric acid ester of Monoglycerides	CMG	2–4
Diacetyl tartaric acid ester of Monoglycerides	DATEM
Polyglycerol ester of MG	PGE	5–7
Sodium stearoyl lactylate	SSL	10–15
Calcium stearoyl lactylate	CSL	5
Polyglycerol polyricinoleate	PGPR	3–6
Sorbitan monostearate	SMS	4–5
Polysorbate 60	PS60	15
Lecithin	LC	4–14
Sucrose Esters of Fatty Acids	SE	1–16
Sorbitan Ester	SOE	1–16
Enzyme Digested/Treated Lecithin	EDL or ETL	Varying HLB values depending on the specific treatment process and conditions

Table 1.

Food emulsifiers utilized in food systems.

Oil and water spontaneously split into two stages; they cannot be combined. But they can combine with the help of an emulsifier to create an emulsion. A two-phase system is called an emulsion, in which the continuous phase is characterized by finite globules from the first phase. The two phases are typically aqueous and lipid [109, 110]. In humans, emulsifiers are essential substances that include saponins, cholesterol, and bile salts, to name a few. Foods such as milk, margarine, peanut butter, coffee creamer, sauces, citrus oil-containing drinks, and animal items have a variety of emulsion systems. An emulsifier needs both lipophilic and hydrophilic groups in order to work correctly. It needs to dissolve in one or both stages. In order to create micelles that divide the phases, the groups arrange themselves in one direction along the phase boundary and in one layer. In this way, the surface tension at the phase boundary is decreased, stabilizing the system [109, 111]. Water-in-oil (w/o) and oil-in-water (o/w) are the two systems. After emulsification with an emulsifier that has a greater hydrophilic group, the o/w system is more stable, whereas the w/o system is the opposite. An emulsion system’s hydrophilic and lipophilic balance (HLB) value determines whether or not an emulsifier is appropriate for usage. Based on the emulsifier’s propensity to dissolve in either oil or water, the HLB value varies from 2 to 18; a low HLB value (2–4) suggests that the emulsifier is more oil-soluble, while a high HLB value (14–18) indicates that it is more water-soluble [112, 113].

The two main components of amphiphilic biopolymers are proteins and polysaccharides. Proteins with emulsifying and foaming qualities, such as casein and whey, are often amphiphilic. In contrast, polysaccharides with thickening qualities and potential nonpolar lipid or protein moieties that aid in emulsification include GA, pectins, xanthan gum, and guar gum. By increasing viscosity, thickening agents stabilize emulsions by reducing emulsion droplet movement and, consequently, separation. It is debatable if nonsurface-active amphiphilic biopolymers qualify as emulsifying agents. Certain amphiphilic biopolymers, such as methylcellulose and hydroxypropylmethylcellulose, can emulsify, although their higher molecular weight may make them less effective than emulsifiers with lower molecular weights [114]. Because certain polysaccharides, including xanthan gum and guar gum, are contaminated with proteins that assist adsorption to the oil-water interface, it was formerly thought that these polymers might aid in emulsification. Nonetheless, the emulsifying capacity of certain gums persists even after purification to remove contaminating proteins, indicating that some polysaccharides’ emulsifying qualities are unaffected by protein contamination. Regarding which food additives are categorized as emulsifiers, there are differences between various regulatory agencies and nations. 261 additives are listed in Codex Alimentarius under the functional class “emulsifier,” sometimes known as “emulsifying salt.” However, many of the additives listed by Codex are not recognized for use in the EU, thus the FSA includes just 63 compounds as emulsifiers, stabilizers, gelling agents, and thickeners that are allowed in the EU8 [115, 116].

3.8.1 Lecithin

According to EU Regulation (EC) No 1333/2008 on food additives, lecithins (E 322) are permitted food additives. They were previously assessed by the SCF in 1982 and the JECFA in 1973. All of the body’s cells use the cytidine-5-diphosphate-choline pathway to hydrolyze phosphatidylcholine, one of the lecithins, into choline. A revised conceptual framework for risk assessment of certain food additives was applied by the Panel following the re-evaluation of the Commission Regulation (EU) No 257/2010. As a result of the refined exposure assessment for lecithins (E 322) as a food additive, the panel concluded that a numerical ADI was not required for lecithins (E 322). Moreover, the Panel concluded that choline from lecithins (E 322) as a food additive poses no safety concerns [97, 117, 118]. The best emulsifier for food production is lecithin, which is a phospholipid with a polar head and an apolar tail. This type of molecule is capable of acting as an emulsifier, a stabilizer, an anticaking agent, and a dietary supplement. Furthermore, they increase choline and acetylcholine levels in the blood and the brain, preventing fatty liver. The first emulsifier discovered was lecithin, in egg yolks, in 1846. A large majority of living cells contain this substance naturally. Soybean oil is the most common source of lecithin today. There are four different phosphatidyl (PP) lipids in lecithin: PP-choline, PP-ethanolamide, PP-inositol, and PP-phosphates. The de-oiled lecithin is granular, whereas the majority of lecithin comes in flakes, rich in polyunsaturated fats, and cholesterol-free. It is a popular emulsifier in w/o and o/w emulsions, possessing a broad HLB range of 3.5–6.5 [68, 119, 120, 121].

3.8.2 Fatty acid esters

Glycerol monostearate (GMS) belongs to the mono and diglyceride class and is the most often used emulsifier. With a 70% market share, GMS was the first emulsifier to be added to food (margarine), and it is mostly used in bakeries. Glycerol is added to fat or oil to create GMS, which is a combination of monoglyceride and diglyceride [122]. The minimal monoglyceride content of one emulsifier is 40%, whereas the minimum monoglyceride content of another is 52%. When making w/o emulsion, a GMS that came from distillation and had a monoglyceride concentration of more than 90% is useful. GMSs come in a variety of forms, including powder, flakes, beads, liquid, semiliquid, and soft plastic. GMS is mostly used to postpone the retrogradation of flour or starch in baked items that are prepared with yeast. Mono- and diglycerides can have their chemical structures changed to those of ester derivatives that are soluble in water by interacting with acids. In baking, lactic acid ester and diallyctyl tartaric acid ester of monoglycerides (DATEM) are frequently used for aerating cakes, frostings, and toppings. The greatest results for baking quality, including loaf volume and staling prevention, were obtained when DATEM (0.75%) with hydrocolloids was added to both hard and soft wheat flours, according to a study on frozen bread dough [50, 53].

Propylene glycol monoesters (PGME), sorbitol-derived sorbitan esters (also known as the “Span range”), and polysorbate fatty acid esters (also known as the “Tween” or “polysorbate” range)—which are created when sorbitan esters react with ethylene oxide—are examples of further emulsifiers. Tween 60, 65, and 80 are polyoxyethylene sorbitan monostearate, tristearate, and mono-oleate, respectively. Span 60 and 65 are sorbitan monostearate and tristearate, respectively. In order to investigate the impact of Span 60 on the microstructure, partial coalescence of fat, apparent viscosity, and overrun of this emulsion, it was introduced to whipping cream. Improvements in overrun and organoleptic qualities were seen in the trial. The use of Span 60 may provide the heat-stable confectionery fat blends that are needed. Conventional beef sausages were more stable during cooking and storage when Tween 80 was combined with a hydrocolloid (such as xanthan, guar, alginate, carrageenan) [123, 124, 125].

Calcium stearoyl lactylate (CSL) and sodium stearoyl lactylate (SSL) are the two most widely used lactic acid esters, also known as lactated esters, in the emulsifier range. The additional SSL interacts with gluten during baking and reduces the amount of gliadin absorbed into the polymer gluten network, hence influencing the extent and pace of gluten polymerization in wheat flour dough. Numerous emulsifier types are utilized in combinations of two or more, ideally in conjunction with GMS. The individual emulsifiers’ HLB values work in concert to enhance the flour grain and generate softer dough. Emulsifiers are used to improve product structure, greater volume, anti-staling properties, denser but finer air cells, longer shelf life, and better product structure [126, 127, 128].

3.8.3 Hydrocolloids

The structural variations, biological origins, and polymeric structure development of hydrocolloids as food additives are varied. As a result, every hydrocolloid exhibits unique reactions and roles as a food additive. In addition, the majority of hydrocolloids possess unique qualities and inherent qualities. Hydrocolloids do, however, have important drawbacks that prevent them from being used in some food systems [129, 130]. Generally speaking, these restrictions can be addressed by selective chemical modification and the creation of natural hydrocolloids. Food hydrocolloids like proteins and polysaccharides are crucial to the composition, stability, and functionality of many processed meals. The functional characteristics of meals where proteins are the main element, such as processed meat and fish products, are determined by the interactions between proteins and carbohydrates. Various hydrocolloids have been suggested to enhance the functional and mechanical characteristics of surimi and reconstituted fish gels. Seawater and salt-soluble fish proteins combine to produce a continuous matrix. Certain additives have the ability to become enmeshed in this matrix, filling it up and influencing the formation of the continuous surimi gel matrix during heat-induced gelation; modifying the liquid phase’s viscosity, mobility, and other properties; and influencing the gel’s texture and appearance, including particle size, textural properties, distribution, and relative volume fraction [131, 132, 133].

Propylene glycol alginate (PGA) and gum acacia, sometimes known as GA, are both superior emulsifiers. The arabinogalactan protein complex (AGP) found in gum acacia is made up of both lipophilic and hydrophilic groups. Citrus oil is emulsified in a sugar solution to provide flavors for fizzy drinks that are stable. By reacting propylene oxide with alginic acid, PGA is produced. It enhances acid stability and prevents precipitation by calcium and other polyvalent metal ions in meals high in oil. It is a component in mayonnaise and salad dressings [134, 135, 136].

3.9 Fat replacers

“An ingredient that can be used to provide some or all of the functions of fat, yielding fewer calories than fat” is how the American Dietetic Association (ADA) defines fat replacers (FRs). The food business utilizes fat substitutes in a broad range of items, some of which include baked goods, dairy products, and meat. To help lead the creation of healthier alternative goods, product developers and food technologists should have a thorough understanding of how various FRs affect the sensory and physical qualities of snacks [137, 138]. By trapping air cells during the creaming process, fat, for instance, can help promote leavening, softness, and a finer crumb in cakes. Then, as a result of the starch gelatinization and egg protein coagulation during baking, this structure is established. In biscuits, fat is usually used to coat and lubricate the flour granules to stop them from absorbing water, as well as to promote the growth of starch and gluten to create a fine crumb (crumbly texture) and a soft, delicate feeling. Other crucial roles that fat plays in cakes, biscuits, and crackers include flavor delivery and shelf life, which are accomplished by delaying the starch granules’ absorption of water [139, 140, 141]. Figure 6 shows some examples of fat replacers used in the food industry.

Figure 6.

Some examples of different types of fat replacers used in food industries.

Protein or carbohydrate components that mimic the mouthfeel, texture, and organoleptic characteristics of actual fats are known as fat mimetics. The components of plant-based and cereal-based carbohydrate-based fat substitutes contain both indigestible and digestible complex carbs. They consist of fiber- and starch-based fat mimics. Maltodextrins and modified starches are among the former, whereas gums, pectins, hydrocolloid gums, polydextrose, microcrystalline cellulose, and methylcellulose are among the latter. With only one-third of the calories in fat, protein-based FRs like microparticulated whey protein offer structure, viscosity, creaminess, and opacity along with a pure flavor basis. Most fat-based fat substitutes are lipid analogs or emulsifiers [142, 143]. They supply far fewer calories since they are not absorbed or digested by the body in the same way as regular fat. There have been several discussions over the use of fat substitutes. Targeted food commodities in this regard are bakery goods (pound cakes, cookies), meat products (beef burgers, sausages similar to frankfurters), dairy products (cheeses, yogurt, and ice cream), and other goods (mayonnaise, low-calorie structured lipids, and human milk fat substitute) [144, 145].

The functions of FRs include texture provision, stabilization, emulsification, gelling, and thickening. Because fat functionality varies greatly depending on the kind of food and the formulation, it is important to choose the right sort of fat replacer. Research indicates that cutting back on fat consumption can help manage body weight and lower the risk of conditions including type 2 diabetes, high blood pressure, and heart disease. It is important not to mislead customers into thinking that meals low in fat and calories may be consumed forever. The best results from fat replacements come from supporting calorie restriction and encouraging the intake of meals that are high in vital nutrients [146, 147, 148].

3.10 Food colors

Food coloring plays a crucial role in the production of food and beverages. It brings life and visual appeal to the products we consume. Food colorants are an essential part of the chemical makeup used in food technology to maintain the desired appearance of food items. They enhance the sensory characteristics of food, which may be lost during processing or storage [36, 37, 149]. Whether you are a professional food manufacturer or a home cook, food colorants are an indispensable ingredient that can elevate the overall esthetic of your food and beverages. In the modern world, the appearance of food products holds immense sway over consumer choices, with color being a pivotal factor [11, 12, 150, 151]. Synthetic food colors have become more prevalent as additives in recent times, as they are capable of imparting desirable characteristics such as enhanced visual appeal, vivid hues, greater stability, and consistency. These additives are a vital component in ensuring that food and drink items are eye-catching on store shelves, and attract customers accordingly. It is worth noting that some food manufacturers use synthetic food colors, which are derived from coal tar, due to their low cost, resistance to light and pH, and high color stability [3, 21]. However, it is concerning that many food products on the market contain non-permitted synthetic colors or excessive amounts of permitted synthetic colors, which can result in food poisoning and severe health issues. Even permitted colors can be harmful if used randomly or in excessive amounts. This can have an adverse impact on both humans and animals. It is essential to develop accurate and sensitive analytical methods to measure food colorants precisely. By taking action against the use of synthetic food colors, we can ensure our health and well-being [152, 153]. Figure 7 shows the types of natural and synthetic food colors used in the food industry.

Figure 7.

Different types of natural and synthetic food colorants used in food industries.

There are three types of synthetic food colors, with primary food colors being the first. These colors are incredibly useful and water-soluble, producing a coloring powder when dissolved that adds vibrancy and enhances the visual appeal of any product. They are composed of (CH2)2CHNH2-COOH, (CH2)2OH, and CH2NHCOCH3, to name a few [93].

Quinoline yellow is a green-hued brilliant yellow dye. It is made with premium components and contains NH-O-Na(SO3)x, NaO3S, and COONa-N-OH, among other things [22].

Tartrazine, a synthetic lemon yellow azo-dye, is widely used as a food coloring agent in various food products, including desserts, candies, soft drinks, condiments, and breakfast cereals. Its chemical composition is represented by the formula C16H9N4Na3O9S2. The dependable and high-quality nature of Tartrazine makes it an appropriate choice for those seeking to enhance the visual appeal of their products. Its versatile use and compatibility with various food products make it a popular choice for food manufacturers [20].

Blended food colors are derived from a combination of primary and secondary colors, either separately or in conjunction with one another. These colors possess a distinct chemical composition of CH2OH-NH2 and are distinguished by their unique color properties. Careful blending of these colors can create an extensive range of hues and shades that can be used to enhance the visual appeal of food. Blended food colors are an essential tool for culinary professionals who wish to produce exceptional and visually pleasing dishes. The use of blended food colors is an effective way to elevate the overall dining experience and impress guests with the appearance of the food [20, 150]. Blended food colors are achieved by the combination of primary and secondary colors, either independently or in a mixture. The unique physical properties of these colors are derived from their chemical composition, which is CH2OH-NH2. The chemical structure of the blended food colorants is responsible for their color properties, which are distinct and diverse [20, 91]. The blending of primary and secondary colors is an important step in the production of food coloring. The colorants produced have a complex chemical composition that influences their performance and properties. The CH2OH-NH2 chemical structure is responsible for the distinctive and diverse color properties of these blended food colors. In conclusion, blended food colors are a crucial component of food processing and are obtained through the combination of primary and secondary colors with one another. These colors possess unique chemical and physical properties that make them ideal for use in the food industry.

4. Conclusion and future trends

Food additives are a part of our daily lives, whether we realize it or not. As consumers, we trust that official institutions around the world are doing everything they can to ensure that these substances are safe and healthy for us to consume. These institutions meticulously evaluate the additives, their impact on our health, and the ADI to guarantee that we can trust the food we eat. Although most of us have confidence in the work of these institutions, some may question the laws or practices in place to protect our health. We can take comfort in knowing that these official commissions are constantly working to protect our well-being, even if we do not always see the complexity of the work they do.

The global delivery of food is highly competitive, and food additives play an integral role in ensuring success. The changing lifestyles of modern society have led to an increase in the consumption of processed foods, making the importance of food additives even more pronounced. Despite recent improvements in the production of safer additives and legislation, several unresolved issues have led to rising controversy and an unyielding demand for better alternatives.

The discrepancies in the use of additives between the European Union and the United States are a cause for concern. The adoption of natural additives, which are safer and healthier, is a necessary and prudent step in the right direction. Natural extracts have multiple beneficial effects such as antimicrobial, antioxidant, and other positive health outcomes, which make them attractive alternatives to chemical additives.

The evolution of natural additives has progressed significantly, transitioning from antiquated substances to pivotal agents for food preservation. The contentious nature and ambiguity surrounding chemical additives, coupled with sporadic alerts, have contributed to the burgeoning interest and financial backing for natural additives. Presently, consumer preference overwhelmingly favors natural additives over synthetic counterparts, presenting a distinct prospect for the food industry to explore novel, more effective natural alternatives while endeavoring to curtail overall additive usage and produce minimally processed goods. The myriad benefits of natural additives, characterized by their synergy and potency, represent a substantial advancement over synthetic additives, which typically yield singular effects on food. Although the production methods for natural additives may vary, they generally offer a safer alternative to synthetically produced additives. Nevertheless, meticulous attention to potential toxicity is imperative. Comprehensive toxicological, carcinogenic, and safety assessments must be conducted to ensure the integrity and safety of these additives and to mitigate potential concerns.

The utilization of natural additives continues to be encumbered by several limitations. While certain constraints are analogous to those associated with synthetic additives, others are intrinsic to natural sources. Primarily, the pricing of natural additives must be competitive within the global market, relative to their synthetic counterparts. Furthermore, the efficacy of natural additives is a critical consideration, particularly in light of the requisite quantity for achieving the desired effect. Substantial quantities may unduly impact the sensory attributes of food products. Additionally, certain natural additives necessitate higher dosages than their synthetic counterparts, posing challenges in terms of cost-effectiveness and viability. Moreover, the absence of distinct legislative frameworks for natural additives, which are often regulated on par with their synthetic counterparts, introduces complexity and ambiguity for consumers. Lastly, the approval process for new additives, whether natural or synthetic, is impeded by the extensive testing essential to ascertain safe dosage levels, identify potential interactions, allergens, and hypersensitivities, and establish acceptable daily intake levels.

The yet unexplored potential of unfamiliar natural compounds, along with their synergistic interactions with other compounds, presents extensive opportunities for the development of novel additives. However, rigorous studies are imperative to preempt potential controversies. A phased transition from chemical additives to natural counterparts, leveraging emerging technologies to replicate analogous effects, is a prudent course of action. Adhering to the paramount importance of safeguarding consumers’ well-being and the environment over pecuniary interests is pivotal. The incorporation of natural additives not only serves to attenuate the impact on the economy and public health but also contributes to the cultivation of a safer and healthier global milieu.

Abbreviations

ADI	acceptable daily intake
AMRD	age-related macular degeneration
ADA	American Dietetic Association
AGP	arabinogalactan protein complex
BHA	butylated hydroxyanisole
BHT	butylated hydroxytoluene
CSL	calcium stearoyl lactylate
CVD	cardiovascular disorders
CDC	centers for disease control and prevention
DATEM	diallyctyl tartaric acid ester of monoglycerides
EHEC	enterohemorrhagic Escherichia coli
EDTA	ethylenediaminetetraacetic acid
EU	European Commission
EFSA	European Food Safety Authority
FRs	fat replacers
FDA	food and drug administration
GMS	glycerol monostearate
GA	gum arabic
HMP	high-methoxyl pectin
HLB	hydrophilic and lipophilic balance
IARC	International Agency for Research on Cancer
JECFA	Joint FAO/WHO expert committee on food additives
LBG	locust bean gum
LDL	low-density lipoprotein
LMP	low-methoxyl pectin
o/w	oil-in-water
PP	phosphatidyl
PGA	propylene glycol alginate
PGME	propylene glycol monoesters
REDOX	reduction-oxidation
RS	relative sweetness
SHMP	sodium hexametaphosphate
SSL	sodium stearoyl lactylate
w/o	water-in-oil