Gamma Irradiation and High Hydrostatic Pressure Applied to Hamburger Conservation

Human nutrition is an essential process, since it provides the essential nutrients for their development. Animal source foods are rich in protein, amino acids, vita-mins, and minerals. And they are subject to contaminants from the raw material to the final consumption. To avoid microbial contamination and deterioration, various technologies are used to ensure their innocuity. These include gamma irradiation and high hydrostatic pressure (HHP), which are nonthermal treatments. Such treatments may reduce the known adverse effects that occur during thermal processing. In meat products, these technologies may induce lipid oxidation, and to limit this process, the addition of synthetic or natural food antioxidants or both are used. This chapter discusses the use of gamma irradiation, high hydrostatic pressure, and application of natural antioxidants in beef hamburger to ensure their quality.


Introduction
The nutrition is an essential process for humans as they provide the essential nutrients. Meat and meat products have a prominent position among foods in the human diet, since it is rich in high-quality protein, essential amino acids, B vitamins, minerals, and other nutrients [1,2] . These nutrients are important in the formation of enzymes, hormones, antibodies, structural proteins, and transporters as well as in the construction and maintenance of tissues [3].
Meats are defined as muscle tissues, without or not include their bone base, and can come from different animal species as long as they are fit for consumption. Meat products are those obtained from meat, edible parts of different animal species in which the properties of the raw materials are modified by means of physical, chemical, or biological treatment techniques or a combination of these methods [4]. These techniques in general may involve the addition of ingredients or co-adjuvants of technology for the production of industrialized meat.
The nutritional composition of meat and meat products favors the possibility microorganism's proliferation [5]. Contamination of meat products may occur during processing and handling of food such as slaughtering, deboning, cutting,

Nonthermal treatments
A discussion of the most representative nonthermal treatments is shown in this section. Further to the application of natural antioxidants among nonthermal treatments, irradiation and HHP are the ones that offer practical application possibilities in meats and derivatives for industrial production [9]. Despite the efficiency of these nonthermal treatments in food conservation, they may favor lipid oxidation of meat products. To avoid this, there is a tendency to combine these treatments Gamma Irradiation and High Hydrostatic Pressure Applied to Hamburger Conservation DOI: http://dx.doi.org /10.5772/intechopen.88874 with the use of natural antioxidants to reduce the sensory changes that are caused by oxidation [17].

Gamma irradiation
Irradiation is a physical treatment in which the food is exposed to a defined ionizing radiation dose. The purpose of this treatment is to control insect infestation, reduce the number of pathogenic microorganisms or deterioration, delay, or eliminate natural biological processes (ripening, germination, or sprouting in fresh foods) [18].
According to [19], irradiated foods were evaluated by several surveys and tests over several years, thus ensuring a safe food for consumption, in relation to nutritional adequacy and toxicological and microbiological safety.
Before 1997, the use of irradiation was limited. However, after Food and Drug Administration (FDA) was approved of the use of irradiation in refrigerated or frozen meats and derivatives to control food-borne pathogens, the consumers began to check the benefits of irradiated food [20,21].
Irradiation can be applied to any kind food. The Codex Alimentarius Commission [22] regulates that the maximum safe dosage for food in general is 10 kGy, where the minimum dosage absorbed by the food must be sufficient to achieve the technological purpose and the maximum dosage absorbed must not compromise the consumer's health or cause the food to be disposed of [22].
According to Codex Alimentarius Commission [22], there is no minimum dosage to be used in meats, but the corresponding maximum dosages of 4.5 kGy for refrigerated beefs, 7 kGy for frozen meats, and 3 kGy for poultry meats have been defined. In Brazilian legislation [23], it is defined for any food that the minimum dose should be sufficient to achieve the purpose, and the maximum should be lower than that which would compromise the functional and sensorial characteristics of the food.
According to Codex Alimentarius Commission [22] for irradiated foods, the radiation sources that can be used are gamma rays, the radionuclides 60 Co, or 137 Cs; X-rays generated with a maximum level of 5 MeV; and electrons generated with a maximum level of 10 MeV. These sources have high energy that changes the position of the electrons of the atoms and molecules, converting them into electrically charged particles (ions). It should be noted that these energies are not capable of inducing radioactivity in any material [18].
Irradiation is considered one of the best emerging technologies to guarantee microbiological safety, in which any food can be irradiated, including meats and derivatives [18]. It is effective in eliminating or reducing pathogenic microorganisms, such as Listeria monocytogenes, Salmonella spp., Escherichia coli, and Staphylococcus aureus [24].
Although the numerous advantages of the use of the irradiation in the foods, the use this process in the meat products may favor physicochemical and biochemical alterations, as for example the lipid oxidation increase. This oxidation is characterized by the formation of free radicals, that is, it is initiated in the unsaturated fraction of fatty acids by the uptake of a hydrogen atom and propagated as a radicalmediated chain reaction. This process depends on the chemical composition of the meat and access to light, oxygen, and storage temperature. As it causes the increase of oxidation, there are changes in taste, aroma, and nutritional value changes that affect the quality of the food [25][26][27]. The addition of antioxidants may contribute to the reduction of this process [28].
Regarding the label of the irradiated food, according to the Codex, food that goes through the irradiation process must include on the label a statement indicating that the treatment has taken place and may optionally use the international symbol available [29]. However, under US law, the symbol must be used and must be declared: "Treated with radiation" or "Treated by irradiation." The Brazilian regulation should include in the main panel the words "FOOD TREATED BY IRRADIATION PROCESS" [23]. Table 1 shows data from the study by Kume et al. [30] that reported the quantity of meat and fish products that were irradiated in the listed countries.
In a research conducted by Chirinos et al. [31], samples of industrialized hamburger inoculated with Escherichia coli O157: H7 were subjected to the irradiation process. It was found that at low doses (1.08 kGy), it was sufficient to reduce the microorganism, without rejection by the trained tasters.
It was evaluated by Moura [32], the oxidation of cholesterol in beef burgers and chicken burgers submitted to irradiation and stored under freezing conditions. It was found that there was an 11% increase in cholesterol oxide levels in frozen burgers.
Frozen chicken hamburger was inoculated with Salmonella sp. and irradiated in a study conducted by Vieira [33], and it was found that dosages of 5 and 7 kGy would be sufficient to reduce the population of Salmonella sp. Sensory evaluation did not change significantly, and shelf life was 120 days the same as the conventional product.

High hydrostatic pressure
The effect of high hydrostatic pressure (HHP) processing was first reported in 1899 by Hite [34]. This process uses an isostatic pressure at room temperature between 100 and 600 MPa. The pressure in the closed and degassed chamber is transmitted by pumps through a liquid (usually uses water) uniformly and instantaneously, which causes the molecular volume to change. The physical effect of the process occurs in the molecules, in which bonds that are weaker, such as those of hydrogen and hydrophobic, are modified [9].
The behavior of food under pressure is determined by three principles: Le Chatelier principle (any reaction that is accompanied by the decrease in volume and increased by pressure); principle of microscopic ordering (increasing pressure increases the order of molecules at constant temperature); and isostatic principle (foods are subjected to uniform pressure from all directions and return to their original shape after release of pressure) [35].
High hydrostatic pressure processing has been used in the industries for the processing and preservation of meats and meat products. Its application can inactivate

Country Irradiated meat and fish (tons)
The United States 8000 pathogenic microorganisms and enzymes, increase shelf life, and maintain sensory quality [8,35]. When compared to thermal treatments, the main advantage of this process is the maintenance of the sensorial and nutritional characteristics of the treated foods. With the wide application of this process, it is possible to develop value-added foods with better quality and shelf life compared to those produced in a conventional way [35]. Some of the important achievements in the treatment of meat product as chicken, pork, and beef processed by using HHP were presented in the works of [36][37][38], respectively.
The work of [36] applied HHP with control parameters 300 MPa for 5 min, at 20°C on fresh chicken breast fillets, and indicated that modified atmosphere packaging maintained their sensory attributes, color, tenderness, and microbiological quality. High hydrostatic pressure processing applied by Grossi et al. [37] indicated that treatment with 600 MPa for 6 min in pork affected the myofibrillar protein degradation pattern due to the increase of cathepsin activity. It was reported by Sanchez-Basurto et al. [38] that the HHP preserved raw meat over a longer-time period without significant difference of texture, tenderness, and color using the control parameters 172-620 MPa and 1-5 min in treatment.
In general, nonthermal technologies are not stand-alone techniques, and in order to improve the inactivation rates, several authors have proposed that HHP treatments are applied in combination with natural bioactive compounds, of which many originate from distinct natural sources [17].
In the work of Kalchayanand et al. [39], HHP treatment was used in roast beef samples inoculated with a mixture of clostridial spores that could be stored for 42 days at 4°C. It was observed that combined treatment of HHP and vacteriocin controlled the growth clostridium spores and extended the shelf life of roast beef for 84 days and can be stored at the same condition.
Different conditions for cooked ham were considered in the works of [40][41][42]. These studies compare samples submitted only to HHP treatment and in combination with some antimicrobials. The results reported by the authors generally show control of pathogen growth and increased shelf life.
A wide range of studies have been conducted to determine and enhance the efficacy in the combination of antimicrobial compounds with HHP treatments in the inactivation induced by pressure of pathogenic microorganisms. More details of the main recent results can be found in the work of [17].

Natural antioxidants
Lipid oxidation is the main cause for loss of sensory quality in meat products [28]. It is a chemical process that generates unpleasant odors, deterioration of the color, texture, and nutritive value of meat and meat products, which diminishes consumer acceptance, since the main attribute for evaluation of the food by the consumer is their appearance [1].
Meat proteins are also susceptible to oxidative reactions during heating and storage, and these reactions damage membranes and cellular functions, altering water retention, color, and reducing essential amino acids [1,2].
To avoid the development of oxidative reactions, the industries use synthetic and natural antioxidants. Antioxidants have the functions of delaying or preventing oxidation processes, for example, in the elimination of free radicals. In this way, it will increase the shelf life and maintenance of food quality and safety [26,43].
There are laws that regulate the use of antioxidants in food products. Sodium isocyanurate, butylhydroxyanisole (BHA), and butylhydroxytoluene (BHT) have been used in meat products. There are studies that show that synthetic antioxidants have the potential to cause toxicological effects, so it may be desirable to replace conventional antioxidants with natural antioxidants [25,27,43,44].
These natural antioxidants are extracted in the form of extracts from different sources such as fruits (grapes and pomegranate), vegetables (broccoli and potatoes), herbs, and spices (tea, rosemary, oregano, cinnamon, sage, thyme, mint, ginger, and clove) [27]. The antioxidant, antimicrobial, and antifungal properties of these spices and extracts are mainly related to their bioactive components, such as phenolic compounds, flavonoids, vitamins, minerals, carotenoids, and phytoestrogens [1,25]. Table 2 lists some studies that used natural extracts in meat and meat products. In meat and poultry products, rosemary extract (Rosmarinus officinalis) is one of the most studied natural antioxidants, and its efficiency in turkey meat, ground beef, and pork has been reported [43].
The antioxidant activity of rosemary extract has been associated with the presence of several phenolics, such as carnosic acid, carnosol, rosmanol, and rosmaridiphenol, which has the function of breaking free-radical chains by electron and metal ion donation [25]. However, rosemary extract can be extracted from leaves and branches [27].
The use of synthetic and natural antioxidants helps to preserve the desirable characteristics of food. It is important to emphasize that when using a natural antioxidant, it is important to evaluate its impact on the sensorial analysis and quality of the final product [2,43].

Conclusions
Consumers want to purchase quality meat products that are safe, nutritious, and natural, with appropriate appearance and flavor. To ensure the innocuity of products to consumers, various technologies and treatments can be used to achieve this result, such as nonthermal treatments, which ensure a safe and better quality product. In addition to these, treatments can use natural antioxidants to ensure a food with its natural characteristics. However, further studies are necessary to

Frozen beef hamburgers
Red color stability during storage [50] Irradiated frozen beef hamburgers Reduced lipid oxidation [25] Oregano Irradiated frozen beef hamburgers Decreased lipid oxidation, but not as efficient when compared to rosemary extract [25]