Functional Properties of Snack Bars

Nowadays, people spend more time and effort to gain greater control over their health by exploring alternative or herbal medicines and natural health products to prevent disease or for a healthier life. It is known that people who consume a diet rich in natural foods, such as fruits, vegetables, nuts, whole grains, and fish, tend to lead a life free of diseases. Recent studies suggest that regular or increased consumption of fruits and vegetables can reduce the risk of chronic diseases, and these health benefits are believed to be primarily due to their natural antioxidants and dietary fiber content. At present, consumers prefer foods with health benefits and, at the same time, convenient for consumption, storage, and handling. In this sense, ready-to-eat nutritious products, such as snack bars, are highly appreciated for their convenience. Snack bars are versatile products often made, with cereals, fruits, and nuts being an ideal food format to deliver healthy nutrients, bioactive compounds, and dietary fiber to the consumers.


Introduction
Globally, a relatively substantial number of terms were used to define the natural health-developed food products. For this purpose, the names of functional foods, nutraceutical foods, pharmaceutical foods, designer foods, farmafoods, vitafoods, foodaceutical, etc. were used [1]. Other terms, often grouped separately, may be included in the same regulations: medical foods, dietary supplements, fortified foods, and botanicals.
There are definitions around the world for functional foods, but there is no official or accepted definition; the functional foods are more of a concept than a defined food product group. Therefore, a functional food can be a natural food, a food in which a component has been added or has been removed, a food in which the nature of one or more components has been altered, or any combination of these possibilities [2]. Functional foods can be those foods made up of distinct, fortified, and enriched elements that provide health benefits apart from the supply of essential nutrients (e.g., vitamins and minerals) when consumed at effective levels within a varied diet [3]. A food may be functional for all individuals or for certain population groups, which can be defined, for example, by age or genetic constitution.
Moreover, the functional food, besides its basic nutritional effect, has also beneficial effects on human body functions (improving the general physical state, decreasing the risk of disease evolution, etc.) [1,[4][5][6]. The main roles of functional foods in regulating processes in the body are presented in Figure 1.
For several years now, there has been a substantial interest in fast food and snack food production, due to changes on people's lifestyles. Consumers have the tendency to look for easily prepared food, such as snacks, which are defined as alternatives to quick meals with or without substantial nutritional value. According to Bower and Whitten [7], numerous products are classified as "snacks," and in this category, mini-pizzas, cakes, popcorn, cereals, and cereal-based bars can be included.
Generally, snack bars are not recognized as functional foods, mainly due to their nutrient-poor composition. In the last years, there is an interest in making new types of snack bars with functional components. Therefore, snack bars can also be included in the functional product category and to consider consumer's acceptable and suitable ready-to-eat products.

Snack bar types
According to a report regarding the snack food consumption in the USA [8], the snack, cereal, and nutrition bars may be classified in three main categories: health and wellness snack, organic snack bars, and energy and nutrition bars. A complex classification of functional bars is difficult to obtain, and the focus has generally been on consumption. Therefore, snack bars can be consumed as a meal part (as part of breakfast, lunch, or dinner or as a snack between meals), as a dessert (after lunch or dinner), or as a meal replacement (breakfast, lunch, or dinner).  The consumption of the snack bars is usually influenced by the age, gender, and the nutritional knowledge of the consumers. According to the International Markets Bureau market indicator [8], the consumption of the snack bars is also influenced by the following aspects: satisfying the need for sweets; saving time; using as an energy source; using for weight loss; and using for the protein, fiber, vitamin contents, etc.

Snack bar production process
The simplified flowcharts of snack bar production processes are shown in Figure 2. For the baked bar products, dry and wet raw materials are mixed together. This mixture is portioned and subjected to baking.
The baking parameters (time and temperature) differ according to the specific characteristics of the finished product. For cold-formed bar production, the ingredients are also mixed together, and the resulting mixture is portioned in the desired shape without a baking step. For both types of snacks, there may also be additional operations, e.g., filling, coating with various glazes, drying bars, etc. Despite the bar type obtained, the final operation in the technological chart is packing.

Formulation and physicochemical evaluation of snack bar ingredients
The bars are often made using a base of cereals such as oats, rice, corn, or proteins (milk dairy proteins, soy, or whey) and fortified with vitamins, minerals, and other nutrient-or energy-rich ingredients [9,10]. Snack bars are not just popular for their portability but also for the health implications associated with their consumption. Trends in health and wellness in food and beverages have increased more and more in recent years, as consumers are turning to less processed and more natural alternatives than regular products. Furthermore, nutritional snacks are suitable products that can provide energy and micronutrients to both healthy people and people from areas affected by famine of the world [10].
Cereal bars are very adaptable products made from processed cereals mixed with a variety of ingredients depending on the target population group [7]. Wheat and/or soy snack bars were designed as nutritional bars to provide the nutrients to consumers on the run [10]. Walnuts were successfully used in the manufacture of snack bars with good nutritional (significant amount of raw fibers and lipids) and sensory quality [11].
In recent years, the demand for high-protein snack bars has grown significantly by the people engaged in sports activities and dieting and as meal substitutes. These snack bars provide a healthy alternative to conventional snacks due to its high content of protein (15-35%, w/w) and other nutritionally beneficial ingredients [12]. In Table 1, different formulations for snack bars are shown.
The tendency to eat more nutritious foods instead of sweet products has led to the development of different snack bar types. Since cereal consumption extends beyond breakfast at any time of the day, these products have become an excellent vehicle for delivering ingredients to functional foods on the market. Cereals have an increasingly important role in modern lifestyle due to the convenient forms they can use such as ready-to-eat food products, snack bars, and energy bars [14].
People who are interested in getting healthier foods and maintaining good body fitness have changed their eating habits, which have promoted growth in the cereal bar market of 20% per year [18]. Therefore, snack bars can be considered as a reliable source of high-quality proteins, fibers, vitamins, and minerals. The nutritive composition of selected snack bars is presented in Table 2.
From the data presented in Table 2, the chemical composition of the snack bars varies greatly depending on their destination. The variation of snack bar composition gives the consumers the possibility to select the proper bar to purchase. Therefore, corn flake crust with fruit breakfast bar is a good source of vitamin A, thiamine, riboflavin, niacin, and vitamin B6, while formulated bar (power bar with chocolate) is a good source of protein, vitamin E (alpha-tocopherol), calcium (covers 50% of the recommended daily dose), iron, magnesium, phosphorus, zinc, and copper. Moreover, the power bar is a very good source of vitamin C (covers 154% of the recommended daily dose), thiamine (covers 537% of the recommended daily value), riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, and manganese [19].
Also, formulated bar, marathon protein performance bar and caramel nut rush, is a good source of protein (covers 50% of the recommended daily dose), calcium, iron, magnesium, zinc, copper, and manganese and a very good source of vitamin C, vitamin E (alpha-tocopherol), thiamine, riboflavin, niacin, vitamin B6, folate, vitamin B12, and pantothenic acid [19], while snack bar with soy can be considered as a good source of high-quality proteins, fibers, and B-complex vitamins [10].
Researchers reported that snack bars with a high ratio of protein/carbohydrate can improve post meal and diurnal glucose profiles in patients with type 2 diabetes and insulin resistance [20]. In addition, proteins can have a very positive effect on the human body, helping to control blood pressure, and the effect has been dependent on the type of protein [18]. Champ et al. [21] reported that the demand to increase dietary fiber content in the daily diet is justified by the positive role of fibers in health and disease prevention, especially in digestive health, energy balance, cancer, and heart and diabetes problems. According to the data presented in Table 2 vitamins. Micronutrients are necessary compounds for a proper physiological state of the body that can be administered orally in the diet, and it is necessary to maintain an adequate balance [21,22]. Minerals must be supplied from foods because they cannot be synthesized, and given the global deficiencies in different minerals, it is worthy to offer convenient food with sufficient amounts of minerals [23].

Functional properties of snack bar compounds
From the compounds present in snack food, only a few, through their specific action, are essential to life and are usually known as biologically active compounds.  Proteins, polyunsaturated fatty acids, vitamins, and minerals as well as food fibers or probiotics may be included in this category.

Proteins
The importance of dietary protein, as a bioactive factor, is determined deficit terms, by decreasing of metabolic capacity, reduction of energy metabolism, inhibition of biosynthesis processes, diminution of immunity, and the body resistance to external agent's actions. Proteins are necessary to support growth, tissue repair, and protection [24]. Usually, the protein necessary is influenced by the gender, age, activity level, body health, or physiological states [25,26]. The conventional protein sources are plants and animals, e.g., meat, milk, whey egg, fish, soy, etc. [26]. In general, protein-based snack bars contain the following proportion of ingredients: soy or dairy proteins (20-40%), carbohydrates as sugar syrups (10-50%), and fats (10-15%) [27,28]. Protein bars in addition to basic ingredients may contain other components such as flavors and stabilizers [29].

Fat and fatty acids
In addition to their role as a source of high calories, as a biomembrane construction material, or as a vehicle of fat-soluble vitamins, lipids are important by their intake in polyunsaturated fatty acids, phosphatide, and substances physiologically active, such as prostaglandin, prostacyclin, etc. [30]. The omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids are essential for human health and are obtained exclusively from the nutrition [31]. In recent years, emphasis has been placed on obtaining functional foods supplemented with n − 3 fatty acids. At present, there is a wide range of omega-3-enriched food products such as bakery products, dairy products, juices and soft drinks, meat products, etc. [32]. Usually, the natural sources of n-3 fatty acids are seed and fish oils [31,33]. Snack bars with a high content of essential fatty acids are generally those that contain crop seeds and vegetable oils (canola, soybeans, corn, and sunflower oils); these are the major sources of linoleic acid (LA, C18: 2) but with a low proportion of α-linolenic acid (ALA, C18: 3) [34]. ALA sources are chia and flaxseed [34,35]. The flaxseeds have a high antioxidant potential and omega-3 α-linolenic acid content [36,37]. The addition of milled flaxseed in snack products, such as bars, is explained by their preventive and functional properties, such as vascular function improvement [38], anti-arrhythmic, anti-atherogenic, and anti-inflammatory functions [38][39][40].

Minerals
Mineral elements have a biological key role because they participate in all the vital processes of the body. Mineral substances can have different roles in vitamins and enzyme functionality, having either an activating role (calcium, magnesium, etc.) or an inhibitor (copper), and can be a part of enzyme structure as specific (sulfur, iron, copper, zinc, etc.) or unspecific (magnesium, zinc, cobalt, etc.) elements [41]. The commercial snack bars usually contain the following minerals in different intakes ( Table 2): calcium, iron, magnesium, phosphorus, potassium, sodium, and zinc.

Vitamins
Vitamins are biologically active compounds of organic nature, with variable and complex structure. Vitamins are needed in very small quantities for the normal Functional Foods development of many metabolic processes, including assimilation and the use of nutrients brought by food, growth, and tissue restoration.
Vitamin B1 is found in the outer layers and germ of cereals, nuts, whole grains, brewer's yeast, etc. Vitamin B1 exhibits several functions within the body, such as essential for maintaining appetite and normal digestion and necessary for growth, fertility, and lactation [42], as well as for the normal functioning of the nervous tissue [43]. According to the nutrition data [19], the bars with the highest content in thiamine are formulated bar, power bar, chocolate (8 mg/100 g), and formulated bar, marathon types: honey nut oat bar; energy bar, all flavors; chewy chocolate peanut bar; and multigrain crunch bar (~3 mg/100 g), with high daily values for adults between 197 and 537%.
Vitamin B2 is widely found in food products. Sources rich in B2 are beer and bakery yeast, meat, eggs, fish, and dairy products. In the body, vitamin B2 fulfills certain metabolic functions, as phosphorus esters are part of the flavin enzyme structure involved in biological oxidation-reduction reactions [44]and together with pyridoxine is involved in the conversion of tryptophan to nicotinic acid.
Vitamin B5, in the form of coenzyme A, is vital in the metabolism of lipids, carbohydrates, and nitrogen compounds [44]. Sources rich in pantothenic acid that are used in snack bar composition are wheat germ, mushrooms, broccoli, cauliflower, oats, dried peas, soybean, etc.
Vitamin B6 is found in large quantities in beer and bakery yeast and raw cereals. Fruits and vegetables have a lower content of vitamin B6. Pyridoxal phosphate and pyridoxamine phosphate are coenzymes involved in transamination, decarboxylation, deamination, etc. [45].
In the body, folic acid as a coenzyme is involved in accepting and transferring one carbon, from a metabolite to another [46], interfering with the synthesis of purines and pyrimidines necessary for nucleic acid formation [47]. Folic acid is mainly found in green leaves, whole grains, soybeans, wheat germ, soybeans, oranges, avocado, etc. [47,48].
Vitamins E performs several functions in the body such as Krebs cycle regulator, a regulator of nucleic acid metabolism with implications for cell maturation and differentiation, a regulator of porphyrin and heme biosynthesis, a regulator of protein and amino acid metabolism, etc. The main nutritional function is a biological antioxidant for oxidizable vitamins and lipids [44]. Tocopherols are found in almost all foods, the richest sources usually used for bar production being vegetable oils (corn germ oil, wheat germ oil), cereal products, and eggs.
Vitamin C is acting as biochemical antioxidant and as enzyme cosubstrate [44], interfering with numerous processes, including formation of stromal proteins (collagen, elastin), maintaining capillary integrity, etc. Sources rich in vitamin C are rosehips, white sea buckthorn, citrus fruits, tomatoes and tomato juice, cabbage, parsley, nettle, spinach, cauliflower, red and green pepper, red cabbage, eggplant, broccoli, strawberries, etc. [45,49]. In a study conducted by Sung et al. [50], a cereal bar with welsh onion extracts was obtained, rich in vitamins C, B2, B3, and B9 and with high-protein content. The study also demonstrated the nutraceutical potential of the bars for the obesity and metabolic disorder's control. DOI: http://dx.doi.org /10.5772/intechopen.81020 USDA Food Composition Databases [51] provides the selection of snack bars according to deficiency in one or more vitamins or any nutrient that must be reintroduced into the diet. As an example, a selection of the snack bar products according to the content of thiamine, riboflavin, and vitamin C is shown in Table 3.

Food fiber
In the food industry, fiber plays a significant role in preventing obesity, diabetes, and cardiovascular disease [52]. Fiber is incorporated into different foods for both nutritional benefits and functional properties, as well as low-cost and noncaloric partial replacements for fat and/or sugar flour [52,53]. Cereals contain quantities of insoluble fiber, except for oats, whereas fruit and, in particular, citrus fruit and apples contain substantial amounts of soluble fiber. Lentils are also used in snack bar development, especially for their dietary fiber and the essential amino acid contents and for the folic acid and iron addition [54].
Lately, emphasis has been placed on the use of resistant starch (RS) in products as a potential functional ingredient. RS may increase the dietary fiber content [55] and promote the probiotic bacteria activity [56]. Aigster et al. [57] studied the addition of RS in granola and cereal bars, to determine the RS health significance and also the consumer acceptability. The study concluded the increasing of dietary fiber intake by the addition of RS.

Conclusions
In recent years, consumers are constantly changing their eating habits, wanting to improve their diet with nutritious and safe food products that are easy to  Table 3.
Classification of snack bars according to the content of thiamine, riboflavin and vitamin C [51].
© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Author details
Oana Emilia Constantin and Daniela Ionela Istrati* Department of Food Science, Food Engineering, Biotechnology and Aquaculture, Faculty of Food Science and Engineering, "Dunarea de Jos" University, Galati, Romania *Address all correspondence to: daniela.istrati@ugal.ro consume but, at the same time, improving health and well-being. Therefore, food industry specialists have continuously changed formulations and ingredients, and thus, new technologies to produce foods with increasing nutritional value and safety that fully meet consumers' requirements. Due to their versatility, snack bars can be used by wide categories of individuals: athletes, people dieting or with nutritional problems, or irregular meals. Snack bars allow the consumers to get necessary energy and the nutritional benefits (high-quality proteins, polyunsaturated fatty acids, minerals, vitamins, and fibers) in one convenient and easy to store package.

Conflict of interest
The authors declare no conflict of interest.