Meat products proteins

In the United States, more than 16.3 x 10 kg of human-inedible raw materials are available each year, and the rendering industry is a valuable asset in diverting these into valuable ingredients for use primarily in animal foods (4). The three largest meat packers are responsible for nearly four-fifths of aU red meat production (5) and enormous amounts of rendered meat meal and animal fat. Three broiler producers account for about 40% of the total broiler production. American Proteins, Inc. (RosweU, Georgia), the world s largest processor of poultry by-products, produces more than 450,000 t of poultry meal, feather meal, and poultry fat each year. It also produces more than 100,000 t of fish meal, fish oil, and fish products each year. Pish meal production worldwide in 1986 was estimated at 6.23 x 10 t, which with the 125 x 10 t of meat and bone meal plus 6.67 x 10 t of feather meal and poultry by-product meal (6) is the primary source of animal proteins used by the pet food industry. 

Vegetable proteins other than that from soy have potential appHcability in food products. Functional characteristics of vegetable protein products are important factors in determining their uses in food products. Concentrates or isolates of proteins from cotton (qv) seed (116), peanuts (117), rape seed (canola) (118,119), sunflower (120), safflower (121), oats (122), lupin (123), okra (124), and com germ (125,126) have been evaluated for functional characteristics, and for utility in protein components of baked products (127), meat products (128), and milk-type beverages (129) (see Dairy substitutes). 

The sacroplasmic proteins myoglobin and hemoglobin are responsible for much of the color in meat. Species vary tremendously in the amount of sacroplasmic proteins within skeletal muscle with catde, sheep, pigs, and poultry Hsted in declining order of sarcoplasmic protein content. Fat is also an important component of meat products. The amount of fat in a portion of meat varies depending on the species, anatomy, and state of nutrition of the animal. The properties of processed meat products are greatiy dependent on the properties of the fat included. Certain species, such as sheep, have a relatively higher proportion of saturated fat, whereas other species, such as poultry, have a relatively lower proportion of saturated fat. It is well known that the characteristic davors of meat from different species are in part determined by their fat composition. 

Protein-Based Substitutes. Several plant and animal-based proteins have been used in processed meat products to increase yields, reduce reformulation costs, enhance specific functional properties, and decrease fat content. Examples of these protein additives are wheat flour, wheat gluten, soy flour, soy protein concentrate, soy protein isolate, textured soy protein, cottonseed flour, oat flour, com germ meal, nonfat dry milk, caseinates, whey proteins, surimi, blood plasma, and egg proteins. Most of these protein ingredients can be included in cooked sausages with a maximum level allowed up to 3.5% of the formulation, except soy protein isolate and caseinates are restricted to 2% (44). 

Free glutamates exist in certain cheeses (such as parmesan), in tomato products, and in soy sauce. These products are often used to enhance the flavor of meat dishes. Proteins can be hydrolyzed by heat, releasing free glutamates. Cooked meats, especially grilled meats, get some of their taste from free glutamates. 

Meat products have to be stabilised in some cases, as meat lipids contain no natural antioxidants or only traces of tocopherols. Most muscle foods contain, however, an efficient multi-component antioxidant defence system based on enzymes, but the balance changes adversely on storage. The denaturation of muscle proteins is the main cause of the inbalance as iron may be released from its complexes, catalysing the lipid oxidation. Salting contributes to the negative effects of storage, as it enhances oxidation. Using encapsulated salt eliminates the deleterious effect of sodium chloride. 

In fact, as will be indicated later in this manuscript, the proteins of meat are the major constituent with which nitrite reacts and explain the largest proportion of the nitrite lost from analytical detection during curing. While considerable discussion has occurred about this so called protein bound nitrite, little has been substantiated about identification and quantitation of the reaction products. Protein bound nitrite has been of concern in analysis for free nitrite because depending on conditions of analysis, some portion of it may be released and measured. 

Finally, NMR relaxometry has also been used in the determination of composition of meat and meat products. Correlations between relaxation parameters and fat content in minced meat and meat emulsions,115 117 protein content in fresh meat115,118 and moisture content in sausages119 have been demonstrated results from fat determinations are summarised in Table 3. 

Soy proteins are used extensively in meat and meat products by the military, the school lunch program and consumers to save money. Their ultimate acceptability is equally dependent upon the nutritional, chemical, sensory and shelf life changes which occur when they are added. Soy proteins in meat products such as ground beef inhibit rancidity, improve tenderness, increase moisture retention, decrease cooking shrink, fat dispersion during cooking and have no important effect on microbiological condition. Concomittantly, inordinate amounts of added soy protein may cause the meat product to be too soft, exhibit an undesirable flavor and may lead to a decreased PER and a deficiency in B-vitamins and trace minerals. In emulsified meat products, soy protein effectively binds water but does not emulsify fat as well as salt soluble muscle protein. Prudent incorporation of plant proteins can result in an improvement of the quality of the meat product with inconsequential adverse effects. 

Some of the uses of soy proteins to augment meat proteins are summarized in Table III. Textured soy flour, though not included in that table, can be used in the same meat systems, where soy grit or coarse soy protein concentrate are used. Besides the economics associated with the use of soy protein, they are utilized in such meat products because of their functional and nutritional properties. 

An evaluation of the composition of the cooking juices, as presented in Table IV, demonstrates, by difference, that fat is retained to a greater extent by the soy concentrate meat product than by the soy flour meat product or the ground beef. The meat product containing soy flour lost more fat during cooking than did the all-beef (Table IV). Similar results were reported by Anderson and Lind ( ). When soy protein concentrates are used in canned meat products like chili, the fat islands within the chopped meat products and the fat cap are eliminated (10). When 4% soy concentrate was added to a minced pork product, cook out of fat and moisture was reduced 31% for pasteurized product and 34% for sterilized product. 

Use of soy protein products in brine injected or absorbed whole muscle meat products such as beef, poultry, and seafood is reviewed. The importance of functionality on brine performance and within muscle tissue is stressed. Major considerations are selection of the proper soy protein, accompanying functionalities such as water-binding, gelling and viscosity, the specific meat system and requirements pertaining to nutrition, processing and marketing. 

Textured Soy Proteins. Textured vegetable proteins, primarily textured flours and concentrates (50% protein and 70% protein, dry basis, respectfully) are widely used in the processed meat industry to provide meat-like structure and reduce ingredient costs (3-6, 9-10). Available in a variety of sizes, shapes, colored or uncolored, flavored or unflavored, fortified or unfortified, textured soy proteins can resemble any basic meat ingredient. Beef, pork, seafood and poultry applications are possible 03, 4-7, 15, 19) Proper protein selection and hydration is critical to achieving superior finished product quality. Textured proteins have virtually no solubility and, thus, no ability to penetrate into whole muscle tissue Therefore, textured soy proteins are inherently restricted to coarse ground (e.g. sausage) or fine emulsion (e.g. weiners and bologna) products, and comminuted and reformed (i.e. restructured) meat products. None are used in whole muscle absorption or injection applications (2-4, 6, 11). 

Soy Protein Concentrates. Both non-functional (low or no solubility) and functional (good solubility, emulsification capacity, and dispersibility) soy protein concentrates (70% protein, dry basis) are commercially available for use in meat products (2-4, 6, j), 15) Normally, a highly functional product with no harsh or bitter flavors is desirable. When used to replace lean meat, non-hydrated concentrate can be used at levels up to 6-7% in finished nonspecific emulsion meats Higher replacement levels or formulas with specific cost/nutrition requirements may use soy protein concentrate with a judicious amount of textured soy protein (6). Excellent yields, cost savings, texture, flavor and nutrient profiles are possible. However, most soy protein concentrates lack sufficient solubility or sufficiently low viscosities to be used in brines for absorption or injection into whole muscle tissue. When legal standards for protein content exist (13), more concentrate must be used to achieve legal minimums. Brine viscosities increase and uniform distribution of brine components throughout the specific whole muscle piece is restricted. Finished product appearance and flavor are easily compromised. Thus, use of soy protein concentrates in whole muscle applications is limited. 

The increasing interest in nutritional and functional properties of soybean protein has promoted their use in the manufacturing of foods for human consumption. Soybean products (particularly infant formulas and soybean dairy-like) may also represent an interesting substitute for infants and people allergic to milk proteins. On the other hand, due to their technological properties and low cost, soybean proteins are increasingly employed as ingredients in milk, bakery, and meat products, in which their addition is forbidden or allowed up to a certain limit. 

Concerning food peptides, most of the HPLC applications deal with food characterization (based on peptide profile), peptide separation, and identification [172,173] and detection of frauds in milk-based products, meat, and protein hydrolysates [115],... 

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