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Processing- Options for Improving the Nutritional Value of Animal Products ROBERT E. RUST The issue of altering meat products to fit residual. It has been my experience that dietary requirements must address these 125 ppmnitriteincurecibaconwillproduce points: 1. Elect on product safety; 2. Effect on economics of manufacture; 3. Effect on storage life; 4. Effect on sensory characteristics such as flavor, texture, and color; ant] 5. Product identity for example, a mor tadelIa without dices of fat is no longer a mortadelIa. NITRATES AND NITRITES Let us examine some of the areas where dietary concerns have been expressed. Ni trates and nitrites are one. About a decade ago we agonized over the potential hazard presented by these processing ingredients. Nitrates largely passed out of the picture once their mechanism of action was under stood. Nitrites, in most products, have been voluntarily reduced by processors. The cur rent use level is 156 ppm, except for pumped bacon, where it is 120 ppm. In most cured meats, sausages, and lunch eon meats, the addition of 156 ppm nitrite will generally yield around 30 to 50 ppm 278 125 ppm - - -I -- 1- - - - - residuals of less than 15 ppm, and probably more like 10 to 12 ppm. Are these significant from a dietary standpoint? Most likely not, since most reliable estimates indicate that nitrite intake from processed meats equals only 3 to 5 percent of total dietary nitrite intake. Current U. S. Department of Agriculture (USDA)-Food Safety Inspection Service (FSIS) regulations (318.7) permit nitrite to be used at the levels given in Table 1. It might be wise for the USDA to bring these regulations further into line with current good manufacturing practice. SALT Salt (sodium chioricle) is a processing adjunct about which I feel no definite con- clusion can be reached that would justify a recommendation to impose limits. To a certain extent, the use of salt is self-limiting, depending on consumer tastes. The general trend toward lower salt levels in food has forced the meat industry to reduce its in- going levels. Although no general survey
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PROCESSING OPTIONS TABLE 1 Levels of Curing Agents for Products Other Than Bacon 279 Curing Agent Dry Cure/ 100 lb of Meat (oz) Sausage/ 100 lb of Meat (oz) Curing Pickle/ 100 gal, 10 percent Pump (lb) Sodium nitrate Potassium nitrate Sodium nitrite Potassium nitrite 3.5 3.5 .0 .0 2.75 2.75 0.25 0.25 2 2 NOTE: In all cases, residuals shall not exceed 200 ppm calculated as sodium nitrite. data are available, it has been my experience that sodium levels in cooked sausage have declined by perhaps 20 percent over the past 10 years. Sodium chloride performs three major functions in a meat product: It helps pre- serve it, it adds flavor, and it develops the binding properties of the proteins. From a preservation standpoint, the role of salt is still critical in ciry cured meats such as hams as well as in dry sausage. Salt also plays a small role in shelf-life extension of cooked sausages. Levels in these products are com- monly 2 to 2.75 percent of the meat block* used in formulation. In Europe, a 2 percent salt addition is customary, but distribution chains are much shorter and shelf-life expectations much less than in the Uniter] States. Through goof! manufacturing practices, the United States can, I believe, achieve adequate shelf-life. However, there are those who would argue that this is the low end of the safety limit. It must be kept in mind that there are certain interactions between salt and nitrite * The notion of meat block is illustrated in the following example. Say that in producing a batch of frankfurters, you start with 100 pounds of meat. All the adjuncts are calculated based on a percentage of this 100 pounds. Thus, if you add 2.5 percent salt, 3.5 percent extender, 0.5 percent sugar, and 10 percent water, you will end up with 116.5 pounds of finished product. The actual salt level in the finished product would therefore be 2.15 percent. (The curing ingre- dients were deliberately omitted from this example.) . , ~ in the inhibition of Clostridium botuZinum that are significant from a public health standpoint. Some research indicates an in- creased clanger of toxin formation as salt levels decrease; however, no clear-cut rec- ommendations for minimum salt levels have been proposed to date. Most other patho- gens of major public health concern, such as Staphylococcus species, are salt-tolerant in the ranges being (liscussed, so salt re- duction probably would have no significant impact on their prevalence (still, the evi- dence here is less than conclusive). In terms of flavor, the preference for sodium is an acquired taste that can be mollified by total (lietary intake. As con- sumers have reclucec! their sodium intake, the meat industry has been obligates] to follow suit. Proposals to substitute other chiori~les (it is the chloride ion that is significant) have encountered flavor prob- lems. Potassium chloride, for instance, could] perhaps partially substitute for sodium chIo- ride but the bitter flavor is undesirable. Furthermore, there is still the question of whether adde(1 dietary potassium would have any significant impact on health. The effect of reclucec] sodium on flavor can be somewhat compensated for by other flavor- ings such as spices and spice extracts. There are no hard-and-fast recommendations that can be made here, since flavorings are a highly variable consideration. The role of salt in developing the binding properties of proteins is critical. Actually, this is twofold. First, sodium chloride ex
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280 tracts the salt-soluble myofibrillar proteins, which, in turn, encapsulate the fat particles as: to form a stable "emulsion" or meat batter. Second, it promotes the swelling of these proteins to allow for exposure of more bond ing sites for water binding. This is crucial for the production of a stable sausage. In practical terms, salt levels of much less than 1.5 percent of the meat block are not functional. Even then, optimum technology must be exercised to make this level oper ational. There are some significant interac tions between sodium chloride and the alkaline phosphates that improve the func tioning of low sodium chloride. For the most part, however, these alkaline phos phates are mostly the sodium salts; hence, actual sodium reduction is minimal. The alkaline potassium phosphates currently al lowed under USDA-FSIS regulations are dipotassium phosphate, monopotassium phosphate, potassium tripolyphosphate, and potassium pyrophosphate. These are not commonly used, though, because of solu bility problems, flavor problems, and the fact that they function somewhat less effec tively than JO their sodium counterparts. In dry cured products, particularly dry and semi-dry sausage, the salt levels needed for preservation become much more signif icant. It appears that a level of 3 Dercent ingoing, which translates to 4.25 to 5 percent salt in the finished product, is optimum. Only recently did the USDA recognize levels less than 3.3 percent ingoing for trichina inactivation. This recognition pro vides a sliding scale of extended drying times in proportion to ingoing salt levels. However, it would be far better to exercise trichina control through an identification program or raw material control rather than through processing treatment. In addition to controlling trichina, it is necessary to achieve a sufficiently high brine concentration to inhibit microbial growth, including the more salt-tolerant molds and yeasts. A brine concentration of 12 percent is generally considered necessary for shelf APPENDIX stability. Percent concentration is calculated Percent salt x 100. Percent salt + Percent water FAT Reduction of caloric intake from fats, particularly the saturatect tatty acids, is an- other major area of concern. This discussion does not focus on mollification of animal fat depots by dietary or other means. Never- theless, such modification must be looked at in light of its effect on the manufacturing characteristics of the meat raw materials, such as flavor, texture, color, and suscep- tibility to oxidation. Reduction of fat in a processed meat product is not as simple as it sounds. A notable success in this area is the commer- cial production of"95 percent fat free', hams. This probably represents the ultimate in fat reduction, since a muscle with all the visible intermuscular fat removed still contains at least 5 percent fat in the form of intramus- cular fat and extractable intra- and inter- cellular lipids. In cooked sausage, such as a frankfurter, the common accepted fat levels of 25 to 30 percent defy significant reduction without sacrificing textural and other sensory prop- erties. A few commercial attempts at straightforward fat reduction have, in gen- eral, resulted in a product with a distinct rubbery texture ant! reduced consumer cle- mand. If the reduction in textural charac- teristics is to be overcome, other compo- nents will have to be mo(lifiecl. For example, the addition of water will offset the fat reduction by softening the texture of the product. Here, however, we encounter USDA regulations that restrict water levels in a product. Right now, the USDA does not permit substitution of water for fat. These interacting regulations need careful examination. I would suggest regulating product composition based on minimum
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PROCESSING OPTIONS protein rather than the current fat/water maximums. Another textural modification involves the substitution of a nonbinding protein gen- erally originating from a by-product source for some of the fat. There has been success in substituting 10 percent cooked pork skins for 10 percent pork fat in dry sausage. However, this has run afoul of regulatory restrictions in labeling requirements. The inclusion of mechanically separated meat (MSM) has generally been shown to reduce textural firmness, but, again, its labeling is in fact restrictive to the point that most processors assume that consumers will be driven away from products containing MSM. In its quest for truth in labeling, the USDA may have erected barriers to intelligent dietary modification of meat products. Clearly, the whole area needs examination. Regulatory tradition should not be allowed to interfere with efforts at dietary modifi- cation of meat products when such modifi- cation is based on sound scientific data. One promising area in the modification of fat in processes] meat products is the substitution of fats and oils of vegetable origin for the animal fat. Through a tech- nique common in Europe, that of pree- mulsifying the fat with milk proteins such as sodium caseinate or its calcium counter- part, two-thirds of the animal fat has been replaced with preemulsified vegetable oil in a slicing bologna without any practical reduction in sensory properties. Preemul- sions are usually made up of eight parts oil, eight parts water, and one part milk protein, which in effect gives a finished emulsion with approximately 48 percent fat. It is likely that somewhat similar results can be obtained with soy or blood plasma proteins. Once again, though, USDA reg- ulations restrict the inclusion of vegetable fats and oils in meat products. Also, calcium caseinate, despite its widespread use in nonmeat products, is not on the Generally Recognized As Safe list (as is sodium cas- einate), and the USDA is reluctant to extend 281 approval for use until there is greater clar- ification from the Food and Drug Admin- istration. Inclusion of stabilized preemulsions that can effectively reduce fat content of the "show fat" appears to be another area worth pursuing. Again, the question of labeling must be considered. A fat/water/protein emulsion diced and incorporated as show fat in a meat product would trigger labeling problems under current regulations. Ob- viously, labeling requirements are a signif- icant stumbling block. What is needed, above all, is a thorough scientific review of labeling regulations and policies totally di- vorced from emotion, tradition, and the like. LABELING A few more words should be said on the subject of labeling. I view the policies (or lack thereof regarding such fanciful labels as Lean and Lite as a regulatory quagmire that is totally out of hand. There needs to be a firm, definitive policy established that would clarify these promotional labels, which currently are being exploited to the confu- sion of the consumer, despite the USDA's recent attempts to clarify them. Another labeling issue that comes to mind is the USDA grades for beef and lamb. These still place an unwarranted emphasis on fat. Even though most responsible sci- entists agree that only about 10 to 15 percent of the palatability differences are explained by the factors considered in USDA grades for beef, this system is still in use. Clearly, it is an emotionally charged issue that has been debated extensively, but can't it be resolved rationally? Personally, I wonder if USDA grades of beef serve any useful pur- pose, and I challenge this committee to reach a consensus on this system, particu- larly insofar as it hinders the consumer in making wise decisions on selecting meat and meat products. The application of pres- ent USDA grade standards, particularly yield
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282 grades, may be the major limitation to processing developments such as immediate postslaughter fat removal. There appears to be very little that can be done under current regulatory con- straints to achieve mollification of meat products through the inclusion of various nutrients (that is, vitamins, minerals, and the like). If I react current regulations cor- rectly, the clirect inclusion of, say, thiamine to a sausage product would not be approved. At the very least it would trigger nutritional labeling, an activity that is cumbersome and often beyond the capabilities of the small processor, since present USDA policy re- quires a Partial Quality Control program as a minimum. Even calcium, one of the nu- trients whose inclusion appears to be a "plus," is in fact restricted when it appears as a component in mechanically separated meat. Does this make sense, if, indeed, additional calcium is an asset to our diets? The United States is the only major de- veloped country to restrict the incorporation of blood in meat products. I can find no sound scientific reason for this restriction. Incleed, it makes little sense considering that blood provides an excellent source of such nutrients as iron and protein. Are we, because of purely esthetic considerations, ignoring some potential good sources of nutrients? It woulc! seem so. CONCLUSIONS Our regulatory bodies too often base their decisions on unsupported opinion an(1 es- thetic considerations rather than scientific fact. Are regulations in elect hampering positive dietary mortification of meat and meat products, especially insofar as proc- essing adjuncts are concerned? This is a APPENDIX question that must be addressed. Following is a list of specific considerations that must be examined, as well as areas important for research. Considerations 1. Regulate composition of meat products on the basis of a minimum protein standard, thus allowing interchange of water/fat for textural purposes. 2. Remove esthetic considerations from labeling requirements (that is, flagging of "variety meats," mechanically separates] meats, and so on). 3. Change fat labeling to allow separation and recombination of fats in manufactured products. 4. Develop simplified procedures for nu- tritional labeling to enable small processors to apply nutritional labeling. 5. Set definitive standar(ls for such fan- ciful labels as Lean and Lite or recommenc! their elimination. 6. Define the roles of beef and lamb grades. Are they a marketing too} or a label for consumer information? 7. Should consideration be given to con- trol of pathogenic microorganisms such as Staphylococcus and SalmoneZZa species as part of dietary considerations? Areas for Research 1. Salt/nitrite/phosphate interactions and their elect on pathogens; 2. Nutritional contributions of meat by- products and processing adjuncts after in- clusion in a processes! meat product; and 3. Mollification of current beef ant] lamb gracles to a system similar to that used for pork (quantitative and age).
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Integrated Nutrition, Genetics, and Growth Management Programs for Lean Beef Production F. M. BYERS, H. R. CROSS, and G. T. SCHELLING We have evolved into a"lean-conscious society," where fats has become a four- letter word and a high priority is placed on getting and staying trim. In no area is this more evident than in our selection of and desire for leaner beef products. Efficient production of palatable lean beef must be a primary objective of the beef cattle industry if it is to compete in the long term. Current yearly production of the 5 billion pouncis of waste ant] trim fat must be reducer! as rapidly as possible. Although beef fat is trimmed extensively at slaughter and by the consumer, which results in a reasonably lean beef product, only the pre- vention of this excessive fat deposition where it occurs will correct the image of beef as a fat, high-calorie product. A diversity of beef products are needed, all of which must be separated from the current image of fat cattle and fat beef. Industry must focus on producing and ef- fectively marketing lean beef and work to associate beef with active life-styles and healthful living. Products must be engi- neered to coincide with consumer needs and to acIdress consumer fears, both per- ceived and real. Since it is easier to create 283 new attitudes than to change olc] ones, the industry must use innovative marketing strategies to reposition beef products with a new identity. Unique challenges face the beef industry to clesign and clevelop new technologies that will allow production of lean beef rather than beef that must be extensively trimmed to make it lean. This will require greater lean tissue deposition throughout the life cycle ant] extensive redirection of feed en- ergy from fat to protein deposition through all phases of growth. This can only be accomplished if all segments of the industry target on the same goal and integrate avail- able technology to effectively manage growth. INDUSTRY PERSPECTIVE The beef cattle industry has evolved from production of extremely lean beef, based largely on Longhorn-type cattle in extensive grazing systems in the nineteenth century, to production of very fat beef from small- size English breeds in the mid-twentieth century. During the second half of the twentieth century, the trend has shifted back toward leaner beef, with selection of
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284 large-framecI, later-maturing, large mature size exotic types of cattle. Recent consumer pressure for leaner beef has accelerated this change and encouraged consideration of many new cattle breeds not formerly part of the U.S. beef cattle industry. The current beef cattle population in- cludes cattle of all types and sizes. They are fed a wide variety of feedstuffs, both grazed and harvested, ranging from poor-quality mature range grasses to high-energy feedIot rations, with most combinations in between. They are managed in systems including wintering, backgrounding, summer grazing, growing, forage finishing, and high-grain feediot programs. The traditional end prod- uct of these diverse cattle-resource combi- nations is Choice grade beef with 30 to 35 percent carcass fat. Consumer preference for a leaner beef product indicates the need to devise systems to economically produce this kind of beef. MECHANISMS TO PRODUCE LEAN BEEF The traditional method user! to increase the production of lean beef is to feed larger mature size cattle. However, an increase in mature size means a larger cow that has greater requirements per unit of weight and greatly increaser! levels of maintenance en- ergy committed to beef production. For example, Chianina cattle produce large, lean carcasses, but because of their size they require more maintenance feed energy. Therefore, a more effective approach for producing lean beef is to modify the patterns of growth in cattle to produce more lean beef from all cattle. While this is the even- tual target of genetic engineering initiatives, systems using these concepts are not likely to surface any time soon. An understanding of growth and its regulation is required to effectively use growth management strate- gies to produce leaner beef products. An outline of options ant! factors involved in APPENDIX regulation through genetics, nutrition, and growth follows: Genetics Establishes upper limit of growth Determines base patterns of growth Sets priorities for growth of tissues At any rate of growth During intervals of growth Targets composition at any weight Sets physiological maturity at points of growth Nutrition: Energy Schedule versus phase of growth Growing versus later stages Current versus earlier nutritional his- tory Deferred versus advanced systems Level and source Forage versus grain Quantity/day versus limits for lean tis- sue growth Rate and composition of growth Substrates for tissue growth Nutrition and function Optimize lean tissue growth Feedback on lean tissue priorities Storage an :1 retrieval of tissues Nutrition en cl physiological limits Growth management: Synchronizing nu trients and needs Endogenous regulation Bulls, steers, heifers Patterns during growth Exogenous regulation Repartitioning agents Estrogens Zerano} Growth hormone Beta-aclrenergic agonists Mechanisms of regulation Priorities for protein versus fat Redirection of nutrients Tissue mobilization Limits for daily deposition Other effects
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GROWTH MANAGEMENT PROGRAMS Role of Genetics in the Production of Leaner Beef Mature size ant] genetics establish the limits (both dally and cumulative), base patterns, priorities, and type of growth predominating through phases of growth. In addition, the genetic directives provide general targets for body ant] carcass com- position and degree of physiological matu- rity over time and weight intervals through growth. However, other factors really de- termine the extent to which these theoret- ical limits will actually be reached, or how patterns and priorities for growth will be followed or translated into and realized as growth. Some general principles that are usually associated with genetic regulation may be useful as a reference point. In general, cattle of larger mature size have greater limits for daily protein growth and have accumulated more protein than smaller cattle at any point during growth and when mature size is reached (Byers and Rompala, 1980; Byers et al., 1986~. Large mature size cattle are typically physiologically younger at any point during growth than smaller mature size cattle. They also place a higher priority on protein growth and deposit a greater fraction of protein at any rate of growth, but espe- cially at lower rates. However, many cattle types violate these notions. For instance, all smalI-size cattle are not early maturing; Longhorn or Scottish HighIanclers, for ex- ample, are small and late maturing. Also, limits for daily protein growth do not au- tomatically follow potential cumulative stor- age. While both Simmental and Limousin accumulate large quantities of protein, rates of protein growth in Limousin may be no greater than in Red or Black Angus, while Simmental have the potential to deposit protein more rapidly. However, both Sim- mental and Limousin are leaner at most weights through growth than Angus. In Simmental this occurs because of rapid 285 protein growth, while in Limousin it is primarily a reflection of Tower energy intake and lower rates of fat deposition. It becomes immediately evident that rate and compo- sition of growth are directly related and not independent of each other. Available energy translates genetic directives through tissue regulation into patterns of growth. Role of Nutrition in Growth Nutrition is directly linked to rate and composition of growth in several ways (Byers, 1982~. Available energy is used to meet the needs for maintenance, protein growth, and fat deposition, primarily in that order. Thus, composition of growth reflects levels of available substrates prowled relative to maintenance and limits for protein growth, with additional energy usually deposited as fat. In general, rates of protein deposition increase at decreasing rates and rates of fat deposition increase at increasing rates with rate of growth. Consequently, percentage protein in growth decreases while percent- age fat in growth increases with rate of growth. Empty body and carcass composi- tion reflects these patterns of tissue growth, and cattle growing rapidly through higher levels of nutrition are fatter at subsequent points in growth and at slaughter. The magnitude of nutritionally regulated changes in body composition at a given weight reflect animal priorities, rates of growth, and length of time that animals are growing at respec- tive rates. Slower (deferred) growth for extended periods of time invariably results in leaner carcasses at any selected weight. However, most cattle deposit some fat, even at slow rates of growth, and the priorities for protein versus fat deposition at any rate of growth are established through genetic directives that are implemented through physiological mechanisms. Physiological mechanisms exist to allow retrieval of fat to provide energy for protein growth if suffi- cient stored fat is available from a previous
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286 phase of growth. Important components of nutrition include the stage of growth versus nutritional schedule, level and source that is, forage versus grain and level relative to growth process priorities. Nutrition is normally considered relative to phase of growth such as preweaning, stocker, or finishing, ant] ranges of nutri- tional levels are implied in each phase. However, the general relationship of rate to composition of Growth applies to all ~O phases of growth; only the relative priorities for protein versus fat deposition change with stage of growth. Commonly used beef cattle feeding and management systems include a range of nutritional programs where periods of rapid and deferred growth are included. All periods of deferrer! growth where pro- tein growth is allowed result in restriction of fat deposition such that the animal is older and has hack more time to deposit protein and thus has accumulated more lean tissue. Animals that have been managed in (referred feeding programs wait be leaner at any slaughter weight and will be heavier when typical slaughter end points are reached. Common systems of deferred feeding in- clucle growing feeder calves after weaning in winter grazing or backgrounding pro- grams to yearling weight before placement on high-energy feecIlot finishing rations that maximize rate of growth. Cattle managed in this system will be more than 150 pounds heavier at slaughter when similar in com- position to cattle placed on feedlot rations at weaning (Byers, 1980~. It follows that they will be leaner at any slaughter weight than cattle fed to grow rapidly immediately after weaning. While this deferrer] system allows smaller mature size cattle to produce larger and more acceptable carcasses when slaughter end points are reached, large mature size cattle will yield unacceptably large carcasses weighing in excess of 1,000 pouncis. This provides the basis for genotype by nutrition interactions, indicating the util- ity of deferred feeding programs for smaller APPENDIX mature size cattle and high-energy feecilot programs for large mature size cattle as soon as feasible after weaning. Some of the great- est real opportunities for growth manage- ment exist within cattle types ant! involve mollifying an animal's inherent priorities for growth. Integrated Growth Management The objective of growth management is to regulate growth and synchronize nutrient sunDlies with nutrient needs to support the desired type of growth. This can be accom- plishe(1 through both endogenous mecha- nisms inherent to an animal (that is, castra- tion) or through exogenous mechanisms such as estrogenic repartitioning agents (Byers, 1982; Lemieux et al., 1983b). The mecha- nisms involvecl in redirection of growth include modification of (1) priorities for nutrient use for protein versus fat cleposi- tion, (2) tissue turnover (Roeder et al., 1984), (3) daily tissue (1eposition limits, ant! (4) nutrient supply. Eventually, growth hor- mone, releasing factors for growth hormone, beta-adrenergic agonists, or immunization strategies to remove negative feedback on growth (that is, somatostatin) may provide additional ways to regulate growth. They may work with or in place of current growth regulation technology. These alternatives are in the early stages of development and probably will not be available any time soon. In the interim, elective systems of growth regulation must be implemented to allow more lean tissue ant] less fat deposition in production of carcass beef. Anabolic estro- genic implants are elective repartitioning agents that modify growth by shifting nu- trients from fat to protein accretion, result- ing in priorities for growth more analogous to those for bulls (Byers et al., 1985a, 1985c; Lemieux et al., 1985a). In a(lclition, they usually enhance rate of growth, serving to further increase lean tissue production (Byers et al., 1985b). Rate and efficiency of lean tissue growth are critical to enhancing lean
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GROWTH MANAGEMENT PROGRAMS beef production through conventional cattle feeding and management systems. In ad- dition to more efficient production, anabolic implants provide the opportunity to regulate growth so as to tailor beef production to meet consumer demand for leaner beef products. While implants have been used for several decacles, the basis for their growth regulator functions have only recently be- gun to be understood (Lawrence et al., 1985~. This is important for the development of growth regulation systems that allow programmer! growth of cattle. Rationale for Anabolic Implant Response Recent research has provided new in- sights into mechanisms by which growth- promoting implants modify growth in beef cattle. Protein growth is a daily function, and cellular mechanisms establish the max- imum rates for daily protein synthesis. Cel- lular limits for protein growth are not often reached because of physiological factors, such as hormonal en c] nutritional mecha- nisms, that set priorities for and limits to protein deposition. Cattle of cli~erent types have different priorities for protein depo- sition at different rates of growth, ant] larger mature size cattle direct more energy to- ward protein growth at any rate of growth. Priorities for protein growth are enhancer! by anabolic implants, which redirect nu- trients from fat to protein in a"daily double play"-increasing lean growth at the ex- pense of fat, especially at rapid rates of gain. The effectiveness of repartitioning im- plants increases with rate of growth (Byers, 1982), with maximal redirection of nutrients from fat to protein at the most rapid! rates of gain (Lemieux et al., 1983b). The effec- tiveness of anabolic regulators is predicated on inherent rates of fat deposition providing the opportunity for repartitioning of nu- trients from fat to protein accretion. Estra- diol-17-beta and zeranol are currently avail- able compounds that occur naturally and 287 are very effective repartitioning agents, en- hancing rates of protein ant! lean tissue production whenever present at effective levels in cattle depositing fat. In recent studies, implants consistently increaser] overall rates of carcass and total protein accretion and yield! of lean retail product. Just as we are what we eat, cattle are what they accrete, with carcass beef reflect- ing cumulative growth from birth to slaugh- ter. Consequently, use of anabolic implants from birth to slaughter provides lifetime growth regulation and provides the maximal redirection of nutrients from fat to protein and lean tissue production. The longer an- abolic agents are proviclec! in efficacious closes, the greater is the increase in total beef lean with a simultaneous reduction in fat. PRODUCING MARKETABLE LEANER BEEF The leaner beef product must be accept- able and, hopefully, even desirable in the marketplace. Thus, the impact of strategies to produce leaner beef on product accept- ability must be included in an assessment of production options. Effects of Breed Type on Acceptability The following general observations can be made after evaluating 29 separate re- search studies: 1. Carcasses from English-type cattle ranked first in the U. S. Department of Agriculture (USDA) quality grade and mar- bling ratings. Continental breeds were in- termediate, while Zebu and dairy purebreds ranked last. 2. Flavor and juiciness appeared not to be affected by breed or breed type. 3. Meat from Zebu and their crosses were rated less tender than the English, dairy, or continental breeds or crosses. These low ratings were supported by significantly higher Warner-Bratzler shear force values.
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288 APPENDIX In conclusion, with the exception of the In summary, forage-fed animals produce Zebu influence, breed appears to have little carcasses that are borderline in acceptability practical influence on muscle quality (Cross et al., 1984; McKeith et al., 1985~. Forage- Versus Grain-Fed Beef A consiclerable amount of data has been published on the effect of forage versus grain feeding on carcass traits (Byers, 1980; Lemieux et al., 1983a, 1985b) and muscle quality (Bidner et al., 1986; Crouse et al., 19841. Animals from forage-fed systems pro duce carcasses that have less marbling, darker lean color, softer lean, coarser-tex tured lean, and lower USDA quality grades than grain-fed animals. Grain-fed animals averaged two-thirds of a quality grade ad vantage over forage-fed animals. The quality grade difference was significant in 12 of 29 comparisons. When the difference was not significant, the trend was almost always in favor of the grain-fed animals. Forage-fed beef, because of its darker and softer lean, will not have the retail shelf-life of grain fed beef. This presents a serious problem from the consumer acceptance standpoint. Grain-fed animals produced carcasses that were significantly more tender than forage fed animals in more than 41 percent of the comparisons. Perhaps even more important, 62 percent of the flavor desirability ratings favored grain-fed beef. The flavor-intensity ratings were almost always higher in meat from forage-fed animals. These intensity ratings were likely related to "oh' flavors rather than to desirable flavors. Limited data are available on taste ac ceptance of forage-fed versus grain-fed beef as evaluated by consumer panels. Gener ally, the differences were either very small or in favor of the grain-fee] beef. Obviously, differences in the literature with regard to quality traits of forage- versus grain-fed beef vary considerably, partly because of the variability in quality of forage, age of the animal, and amount of grain supplemented to the diet. in terms of color, firmness, and retail shelf- life. Meat from these carcasses is borderline in taste acceptability. To date, the U. S. beef industry has not been willing to risk losing its "taste" image by moving to a total forage production system. Such a system would be impractical for other reasons, too, such as retained ownership because of the time required to reach acceptable market weights and the inability to supply the marketplace on a consistent basis. Bulls Versus Steers Castration of meat-producing animals has long been practicer] in the United States. It is intended to produce an animal more acceptable to current management systems and to provide a more desirable carcass for marketing. During the past four decades, a number of research studies have been con- ductec! to assess the performance and meat characteristics of castrates versus noncas- trates (Griffin et al., 1985; Sei(leman et al., 1982~. In general, the results have indicated that bulls grow more rapidly, utilize feed more efficiently, and produce leaner car- casses. Increased production efficiency ob- taine(1 through the use of intact males has often been offset by management problems, particularly with animal behavior. Meat pro- duction from young bulls has met with strong resistance from meat packers, in part because of carcass size variability, difficulty of hide removal, and inability to obtain an acceptable USDA quality grade. Retailers have resisted using meat from young bulls because their meat has been labeled as less tender and less clesirable in color and tex- ture. The obvious advantages of using the young bull for meat production are efficiency of growth, leanness, and muscling. The dis- advantages are in the area of carcass traits and tenderness. Some of the problems as- sociated with tenderness can be corrected
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IMPROVING NUTRITIONAL VALUE OF POULTRY MEAT AND EGG PRODUCTS 321 quality protein. Beef blood, for example, contains 18 percent protein and is rich in lysine, valine, tryptophan, phenylalanine, ant] leucine. However, blood proteins are very low in isoleucine, which can result in an amino acid imbalance (Olson, 19704. The plasma component of blood contains about 70 percent protein and the cellular fraction (rec! ant! white celIs) about 94 percent pro- tein (Stevenson and Lloyd, 1979~. Young et al. (1973) demonstrates! that the protein efficiency ratio of a diet containing dried bovine plasma could be increaser] from -1.05 to 2.88 by adding 1.2 percent Dk- isoleucine to the diet. The composition of dried poultry blood is 80 percent protein, 8 percent moisture, 1 percent fat, and 11 percent fiber or ash (Mountney, 1976~. Broiler chickens contain about 7.5 per- cent of their body weight in blood, 45 percent of which is collectible during slaugh- ter operations (Kotula and Helbacka, 1966~. In 1985, more than 23 billion pounds of poultry were inspected! in the United States (U.S. Department of Agriculture, 1986~. Therefore, some 800 million pouncis of blood could have been collected. Efficient processes for hygienic blood col- lection from large animals using hollow knives and sodium citrate (to prevent co- agulation) have been reporter] by Stevenson and Lloyd (1979) and Wismer-Peclersen (1979~. Systems for collecting blood] have also been constructed and commercially tested in poultry-processing plants (Childs et al., 1976~. These systems were effective ant] reliable in handling the blood and also reduced the pollution entering the plant effluent. However, they were not designed for collecting blood for use in human food. Although a sanitary system for blood col- lection may be technologically possible, the economic aspects of protein recovery from blood remain a problem. Satterlee (1981) stated that the "problem is the cost of recovering protein from dilute solutions and resulting energy needler! to dry the whole solution, to concentrate and preserve the protein." New energy-efficient recovery processes are required to make such recov- ery feasible. Increased Use of Giblets Poultry giblets heart, gizzard, and liver are not fully used in the Uniter! States. In some processing plants, especially those slaughtering bircis for use in further proc- essing, it has become economically infeasi- ble to harvest, clean, and package giblets. These three foods are high in protein, iron, and niacin. In addition, liver is high in vitamins A and C. The undesirable texture of gizzard and heart tissue has been a factor in the underuse of these foods. In acldition, the functional properties of the proteins in these tissues are not as acceptable as those in the skeletal muscle of poultry. A number of studies have demonstrated that protein modification can improve the functional properties of various tissues: beef (DuBois et al., 1972~; fish (Spinelli et al., 1972~; beef heart (Smith and Brekke, 1984~; and mechanically deponed fowl (Smith and Brekke, 1985a,b). Accord- ing to Franzen (1977), mollification refers to the intentional alteration of the physio- chemical properties of proteins by chemical, enzymatic, or physical agents to improve functional properties. According to Brekke and Eisele (1981), acylation reactions, involving the direct ad- dition of chemical groups to functional groups of amino acid side chains via substitution, have the most potential for chemically mod- ifying food proteins. The anhydrides of acetic and succinic acids are usually the acylating agents, since they are easy to use, safe, ant] inexpensive and produce acylated deriva- tives that are functionally important. When a protein is reacted with acetic anhy(lride, the acylation reaction is termed acetylation; when succinic anhydride is used, the reac- tion is referred to as succinylation. Succinylation affects the physical char- acter of proteins by increasing the net neg
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322 ative charge, changing conformation, and increasing the propensity of proteins to dissociate into subunits, breaking up protein aggregates, and increasing protein solubility (Franzen, 19771. For acylated proteins to be incorporated into foods, they will need to be safe, diges- tible, and probably approved by the Food and Drug Administration en c] USDA as food ingredients since the protein has been mod- ified. Groninger and Miller (1979) indicated that the influence of acylation on protein utilization and nutritional quality clepends on the type of protein, the amount of protein mollification, and the acylating agent used. Similar techniques may also be useful in improving the functional properties of poul- try giblets, thereby making these products, with good nutritional properties, more us- able by the poultry further-processing in- dustry. Hot-Deboning and Hot-Stripping Hot-cleboning is the removal of meat from the eviscerated carcass before the onset of rigor mortis. Hot-stripping is a modification of hot-cleboning in that the muscle is re- moved from a nonevisceratec3 bird. As much as 1 percent of the total solids in poultry meat may be lost cluring water chilling of the carcass. These losses, al- though minor, do occur with water-soluble components such as vitamins ant] minerals. Air chilling or hot cleboning alleviates this loss, since the carcass is not in contact with water for a prolonged period. Of probably greater importance than this 1 percent loss in solids content, however, is the potential economic advantage of hot eboning or hot-stripping. The economic savings that could be expected with these techniques include energy savings through a decrease in cooling costs, decreases! water consumption, lowered equipment expend- itures, recluced labor and time, and im- proved yields. APPENDIX For hot-stripping to be used, changes in USDA inspection regulations are necessary, since muscle tissue is remover! from car- casses prior to the inspection of the viscera. Removal of the Abdominal Fat Pad Consumers do not like to buy chicken containing the abdominal fat pad. Most remove it themselves before preparing the chicken. Several large poultry companies are currently removing this fat at the proc- essing plant in an effort to sell a product that is lower in total fat than their compet- itor's chicken. The average abclominal fat pad weighs about 40 grams, which consti- tutes 2.5 percent of the total weight of the carcass ant! 10 percent of the total body fat (F. E. Pfaff, personal communication, 19861. These values are basec] on whole carcass composition determinations and not on spe- cific cuts of boneless meat. Reduction in Sodium Content of Further-Processed Products In recent years, considerable attention has been focused on sodium and its potential impact on public health. Although the value of Tow-sodium diets is questioned by some scientists (Kolata, 1982), there is sufficient concern within the scientific community (Putnam and Reilly, 1981) ant! by many consumers to warrant production of food products containing less sodium. Poultry meat itself is not high in sodium content; cooke(l breast meat contains 63 mg of sodium/100 grams of meat, and cooker] thigh meat contains 75 mg/100 grams. How- ever, during the further processing of poul- try meat into products, the sodium content may increase dramatically as sodium chlo- ride and various sodium phosphates are added to the product. Sodium chloride is generally used in fur- ther-processed products such as frankfurters at levels of 1.5 to 2.5 percent. Salt influences the flavor, may affect the shelf-life, and
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IMPROVING NUTRITIONAL VALUE OF POULTRY MEAT AND EGG PRODUCTS affects the functional properties of the my- ofibrilIar proteins. One option for lowering sodium content is to use substitutes for all or part of the sodium chloride, such as calcium chloride, magnesium chloride, and potassium chlo- ride (Hand et al., 1982; Maurer, 1983~. Hand et al. (1982) reported that replacing 100 percent of the sodium chloride with magnesium chloride or potassium chloride was detrimental to the flavor of the frank- furters prepared from mechanically de- boned turkey. The authors suggested that 35 percent of the sodium chloride could be successfully replaced with potassium chlo- ride; magnesium chloride caused offflavors, even at the 35 percent level. Smith and Brekke (1985b) varied the sodium chloride content of frankfurters pre- parec] from enzyme-moclified, mechanically clebonec! fowl. They found that 0.5 percent salt was the least amount that could be added and still produce a satisfactory frank- furter from which the casing could be easily removed. Brekke ant! Eisele (1981) had earlier reported that enzymatic modification also has potential as a partial substitute for salt in processed meat products. The low- salt (0.5 percent) frankfurters were rated as having less chicken frankfurter flavor than products prepared with 2 percent salt. The authors states] that if low-salt franldurters are to gain consumer acceptance, appropri- ate spice formulations will need to be de- veloped to compensate for the salty flavor. Barbut et al. (1986) reported that turkey frankfurters with 1.5 percent salt combined with phosphate were as acceptable as "ref- erence" frankfurters, which contained 2.5 percent salt. The sodium chloride in poultry frank- furters could be reduced to at least 1.5 percent (590 mg of sodium/100 grams of meat) without detracting from the flavor and to as low as 0.5 percent (197 mg of sodium/ 100 grams of meat) if additional spices can be found to improve the flavor. 323 Reduction of Fat Content in Poultry Frankfurters Chicken and/or turkey frankfurters tra- clitionally contain 18 to 22 percent fat, compared to pork and/or beef franks, which usually contain 25 to 30 percent fat. Some producers of poultry franks have lowered the fat content of their product to 13 to 16 percent by using mechanically debonec! meat from portions of the poultry such as the front quarter, breast cage, or skinless necks, which contain less fat than backs or legs. According to a study in Consumer Reports (Anonymous, 1986b), poultry frankfurters ranged in caloric content from 180 to 300 keal/100 grams of meat; the mean was 243 kcal/100 grams. From a sensory standpoint, fat is an important component in increasing the pal- atability in a food such as frankfurters. If the fat content is too low, the resulting product tends to be rubbery and tough. Therefore, although consumers may think they want a much leaner frankfurter, such a product may not be acceptable to them. Reduction in Fat Content of Fried Poultry Products Batter/brea(led, deep-frie(1 poultry pro(l- ucts have been a mainstay of the further- processed and fast-food industry for many years. The current emphasis is toward bone- less products, such as nuggets and patties. According to Przybyla (1985), the single fastest growing area within the processed chicken category is frozen, boneless, breaded chicken, partly because of increased sales of chicken-based finger foods in fast-food outlets. Retail sales of such items increased 71 percent from 1982 to 1984. There is also more interest in producing a product that is lower in fat and therefore lower in calories. Baker et al. (1986) recently evaluated four cooking methods for battered and breadecl broiler parts: FF (full frying in 177°C oil),
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324 FSF (fry, steam, fry: brief fry, followed by longer steam cook plus additional short fry), WC (water cook: thoroughly cooked in hot water followed by 45 seconds of frying), and FOC (fry, oven cook: fries! for 2.5 minutes followed by thorough heating in a 218°C oven). The three most commonly used methods for commercial preparation of retail frozen, fully cooker! and browned, battered and breacled chicken are WC, FF, and FOC, respectively. Baker et al. (1986) found that the fat content was slightly higher in breasts cooked by FF and FSF compared with breasts cooker! by WC ant] FOC, but the differences were not significant; for thighs, there was very little difference in fat content due to cooking treatments. Gen- erally, there were no differences in the flavor or acceptability of parts heated by any ofthe four methods; yields were highest for pieces cooker] by FSF, followed by FOC. Staclelman (1985) illustrated that breaded chicken products can be producer] with reduced caloric content by using hot air cooking instead of deep-fat frying, which resulted in a 23 to 31 percent decrease in fat content of parts and a 13 to 15 percent decrease in calories, ant] by removing the skin before breading an(l hot air cooking, which resulted in a 42 to 65 percent decrease in calories (see Table 1~. According to Stadelman (1985), when TABLE 1 Analyses of Chicken Parts APPENDIX breaded, fried chicken contains 20 percent fat, as it frequently does with open kettle frying, 60 percent of the calories come from the fat. By removing the skin and cooking in hot air, a chicken breast or drumstick can be prepared with only 27 percent of the calories coming from the fat. Cooking systems such as the one men- tioned above and/or broiling will become more commonplace in the future as the demand for poultry products with less fat and fewer calories increases. Increased Utilization of Proteins Recovered from Bone Residue of Mechanically Deboned Poultry Bones from slaughtered animals, espe- cially larger animals such as beef and swine, are usually used for animal feed, gelatin, and glue. However, they could be used as ingredients in certain processed products; they are high in protein and provide a dietary source of minerals such as calcium. Bone products are used as food ingredients in some European countries. Some coun- tries consider bone-derived protein added to a meat product to be meat; others con- sicler it to be a nonmeat ingredient. In the Unitecl States, bone-(lerived protein is not currently permitted in food products (Calvi et al., 1984b). Breast Thigh Drumstick Percent Kcal/ Percent Kcal/ Percent Kcal/ Source Fat 100 g Fat 100 g Fat 100 g USDAa 13.2 260 16.2 275 15.8 268 Lab friedb 15.7 275 16.9 279 14.0 244 Lab modified 10.8 233 13.0 243 9.9 209 Lab ultimates 5.7 186 9.8 218 4.9 166 aData from U.S. Department of Agriculture. 1979. Composition of Foods Poultry Products. Agricultural Handbook No. 8-5. Washington, D.C.: U. S. Department of Agriculture. bPressure deep fat fried, commercial equipment. CPieces with skin; hot air, no frying. Pieces without skin; hot air, no frying. SOURCE: W. J. Stadelman. 1985. This chicken product breaks "grease barrier." Broiler Ind. 48:46.
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IMPROVING NUTRZTIONAL VALUE OF POULTRY MEAT AND EGG PRODUCTS 325 Recent estimates indicate that 300 million pounds of mechanically deponed poultry are produced annually in the United States. This represents yields of about 60 to 70 percent mechanically cleboned poultry de- pencling on the type of machine used. On the basis of these estimates, 150 million pounces of bone residue (BR) are produced annually, most of which is used in fertilizer, pet food, or animal feeds. Bone residue is the material remaining when mechanically cleboned poultry is prepared. Bone residue has characteristics that make it a valuable potential source of human food. It contains 20 percent protein, which represents an additional 30 million pouncis of protein avail- able annually for human use, assuming all protein could be extracted. Bone residue contains approximately 18.9 percent protein, 7.7 percent fat, 11.7 per- cent ash, and 60.0 percent moisture (Mast and Opiacha, 1987; Opiacha et al., 1986~. The two methods that have been developed to extract protein from BR are use of sodium chloride solutions (Kijowski ant] Niewiarow- icz, 1985; Young, 1976) and use of mild alkali solutions Jelen et al., 1982; Opiacha et al., 1986~. Freeze-clriecl protein isolates from BR using sodium chloride, prepared by Young (1976), contained 60 to 65 percent lipid, 5 to 10 percent ash, and 4 to 6 percent moisture. The freeze-cTried protein extract obtained by Opiacha et al. (1986), using alkali, container] 45 percent protein, 47 percent fat, ant] 14 percent ash. Yields of dried extract represented! 7 percent of the original BR. Limiter] information is available on the nutritional quality of protein from BR. Law- rence and lelen (1982) state that severe alkali treatments of protein may cause ra- cemization or destruction of certain amino acids; in abolition, unusual new amino acids may be produced, such as lysinoalanine, lanthionine, and ornithinoalanine. These authors concluded that the alkali extraction methods, as usually conducted with BR, should not produce material such as lysi- noalanine that could pose health hazards for consumers. Protein extracts from BR have relatively good functional properties (water-holding capacity, emulsifying capacity, solubility) and could serve as ingredients in other poultry proteins. The poultry industry should be encouraged to explore the economic feasibility of using this protein source, which is currently underutilized or cliscarded. Reduction of Cholesterol Content of Much research has focused on reducing the cholesterol content of chicken eggs by altering the diet or through genetic selec- tion. These approaches have met with vary- ing degrees of success. Another alternative is to modify the egg yolk after the egg is laid. Since this disrupts the shell, albumin, and yolk, only processed eggs (currently about 15 percent of all eggs consumed) are available for this procedure. Approaches used to date include dilution of whole liquid egg with egg white, thereby reducing the cholesterol content of the final product; removal of portions of the yolk lipids and cholesterol with various "sol- vents," thereby producing a product lower in cholesterol; and complete removal of the yolk and formulation of a substitute "yolk" from vegetable oils and other ingredients, thereby producing a product that is choles- terol-free. Numerous U.S. patents have been ob- tained to accomplish the above goals. A few are discussed below. Metnick (1971g, U.S. Patent 3,563,765: Egg yolk solids were treated with nonpolar solvents (for example, hexane) at '160°F (71°C) to extract 50 to 90 percent of the fat and 70 to 98 percent of the cholesterol. The author indicated that n-hexane caused "lit- tle, if any, damage to the functional prop- erties of the remaining protein."
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326 Melaick et al. (1971g, U. S. Patent 3,594,183: A specific objective of this patent was to provide an egg yolk product high in polyunsaturates, low in saturates, and low in cholesterol. Egg yolk solicis, from which most of the fat and cholesterol have been extracted with n-hexane, were mixed with vegetable oil, salt, emulsifiers, and coloring compounds. After emulsifying, pasteuriz- ing, and drying, "refatted egg yolk solids" were obtained. These can be used as a replacement for conventional egg yolk sol- ids. Seeley (1974), U.S. Patent3,843,811: A frozen egg product was prepared that con- tained 0 to 1.1 percent fat, 8 to 18 percent protein, and <0.05 percent cholesterol. The product contained-92 percent egg white and '8 percent egg yolk. Other ingredients added were 2 to 2.6 percent potato flour, 0.1 to 0.2 percent carboxymethy! cellulose, 1.4 to 1.8 percent nonfat milk solids, and citric acid. Glasser and Matos (1976), U.S. Patent 3,941,892: This patent differed from others in that a frozen "sunny-sicle up" egg product was cleveloped; the mold used to form the shape was also used as the package. The "yolk" portion was synthesized with 20 to 45 percent dried egg white, 5 to 35 percent oil (with a polyunsaturated/saturated tP/S] fatty acid ratio > 0.6), ciry milk protein, vegetable gum, colors, flavorings, and emul- sifiers. Seeley et al. (1976J and Seeley and Seeley (1980), U. S. Patents 3,987,212 and 4,200,663, respectively: A frozen egg product that con- tains no cholesterol or egg fats was producecl that was suitable for making scrambled eggs, omelets, and so on. The product was pre- pared by blending egg whites and small amounts of nonfat milk solids, vegetable gums, and flavor enhancers. Fioriti et al. (1978), U. S. Patent 4,103,040: The goal of these authors was to produce wet egg yolks and egg products that were low in cholesterol ant! had a P/S ratio > 1, while maintaining the functional properties APPENDIX of natural eggs. Wet egg yolks were pre- pared using a high-energy, higher shear mixer for a short time. During mixing, cholesterol was extracted from the yolk by the oil. At the same time, the P/S ratio increased. The wet yolk was then separated (centrifuged) from the oil. Egg yolk products were produced in which > 70 percent of the cholesterol was removed and the P/S ratio was > 1.3. BoZ(lt (1981), U. S. Patent 4,296,134: A 99 percent cholesterol-free egg blend was prepared that was low in fat (1. 25 percent) and calories (80 kcal/100 grams). The blend contained 60 to 96 percent liquid egg white, 0 to 18 percent water, 2 to 10.5 percent protein replacement (nonfat dried milk solids, powdered egg albumin, and soy protein), stabilizers, flavoring, and coloring. Tan et al. (1982), U. S. Patent 4,360,537: These authors developed a "lipoprotein emulsion system composed of protein, edi- ble oil, and other selected food ingredients" that could be used to replace egg yolk. Their primary objective was to improve the com- position ant! processes for preparing a pro(l- uct with good functional properties. The nutritional quality of one egg substi- tute has been compared to whole eggs by several investigators. Navidi and Kumme- row (1974) reporter! that raw egg substitute caused severe nutritional deficiencies in weanling rats ant! that all animals died within 4 weeks of weaning. Francis (1975) reported 100 percent mortality of chicks within 12 days when fed egg substitute as their only foocl. Since eggs are not usually the only food in a diet, Ryan and Kienholz (1979) prepared diets for chicks in which egg substitute or whole eggs constituted only 40 percent of the diet. These authors concluded that when cooked and fell in a palatable form, egg substitute is a satisfac- tory source of protein to support chick growth. Chicks fed whole-egg diets weighed 787 grams after 28 days, whereas chicks fed
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IMPROVING NUTRITIONAL VALUE OF POULTRY MEAT AND EGG PRODUCTS 327 egg substitute averaged 687 grams (about 13 percent less). Baker and Darner (1977) ant] Baker ancI Bruce (1986) prepared egg blends by varying the yolk to white ratio from 1:1 to 1:10. Liquid egg with a 1:3 ratio of yolk to white pro~lucecl scrambler! eggs and omelets com- parable to those made with whole eggs but contained only 50 percent as much choles- tero! and 30 percent fewer calories. In the 1977 study, the authors found that egg blencis containing as little as one-fourth the normal amount of egg yolk, with protein and lipid raised to the content of normal egg by the addition of ciried albumin and corn oil, made egg products that were as acceptable as those made with whole eggs. The patents and research studies re- viewed have focused on cholesterol elimi- nation or reduction in egg yolk products. Larsen and Froning (1981) suggested that fractionating egg yolk into its lipid, protein, and aqueous components may also lead to entities with new properties that could then be used in food systems. After trying several solvent systems, they reported that either hexane-isopropyl alcohol or hexane-ethyl alcohol was the most efficient for separating the egg oil fraction. If a protein isolate is desirecl, ethyl alcohol or isopropyl alcohol is the appropriate solvent; the use of hexane altered the integrity of the protein so that it was no longer an effective emulsifier. Tokarska and Clandinin (1985) described a method for the preparation of egg yolk oil that did not cause decomposition of unstable polyunsaturated fatty acids. They obtained optimal extraction of lipid from egg yolk with ethanol/hexane/water. They reduced the cholesterol content of the egg yolk oil by 80 percent by washing with 90 percent ethanol; the cholesterol content of the prod- uct was 7 mg/gram of oil. Solvent extraction procedures do not se- lectively remove cholesterol and can impair the functional properties of certain compo- nents. An alternative to solvent extraction is supercritical fluid extraction (SFE); the lipid components need not be extracted and functional properties are not clestroyed. A supercritical fluid is produced when the temperature of a gas is raised above the critical point and is then subjected! to high pressure. As pressure is applied to a gas above critical temperature, the density of the gas will increase and may approach that of a liquid, while the viscosity of the gas is virtually unchanged. This combination of high density ant! low viscosity allows it to be an excellent extracting agent. The su- percritical fluid has the ability to readily diffuse in and out of the food, thereby increasing extraction efficiency. By varying the density of the fluid through pressure changes, the solubflity of the fluid] can be adjuster! to preferentially extract certain components. For egg products, the goal is to selectively extract cholesterol without removing the polar lipids responsible for functional and sensory properties of the resulting product (G. W. Froning, personal communication, 1986~. The food industry is currently using SFE to decaffeinate coffee; other applications may be extraction of spices; removal of oil Tom snack foods; extraction of of} from cottonseecl, corn, and soybeans; an(l extraction of flavors from foods. To ~late, no one has used SFE with eggs or egg products; however, scientists at the University of Nebraska have initiated research to extract egg yolk with supercritical carbon dioxicle at various pressures and tem- peratures to obtain extraction of cholesterol. SFE is further discussed by Hettinga in this volume. Incorporation of Eggs To Increase Nutritional Value of Foods The consumption of shell eggs is rapidly declining in the United States. One ap- proach to curbing an overall (that is, shell plus processed) decline in egg consumption is to increase efforts for developing new products made entirely or partly from yolk, albumin, or whole eggs.
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328 SUMMARY From a nutritional point of view, poultry and egg products are good because they contain high-quality protein and provide many other essential nutrients. Even with their excellent nutritional quality, however, these products are not the "perfect" food- nor should they be. No one foot! can be expected to provide all the nutrients we require; a balanced diet of many different foods is essential for well-being. Nutrient loss during primary or further processing of poultry is minimal. Aspects of processing that may further enhance the nutritional value of poultry are increasing the utilization of blood, giblets, and bone residue protein; hot-cleboning; removal of the abdominal fat pad in ready-to-cook car- casses; and reduction of fat en c] sodium content in further-processec! products. The primary negative aspect of egg nu- trition is the high amount of cholesterol in the yolk. Numerous methods have been proposed to reduce or remove cholesterol from processed egg products. The industry needs to look at these approaches as it develops much-needed, new, egg-based products. REFERENCES Alexander, H. D., E. J. Day, H. E. Sauberlich, and W. D. Salmon. 1956. Radiation effects on water soluble vitamins in raw beef. Fed. Am. Soc. Exp. Biol. Fed. Proc. 15:921. Ang, C. Y. W., and D. Hamm. 1983. Comparison of commercial processing methods vs. hot deboning of fresh broilers on nutrient content of breast meat. J. Food Sci. 48: 1543, 1544, 1565. Ang, C. Y. W., D. Hamm, and G. K. Searcy. 1982. Changes in nutrient content during chill-holding of ice-packed and deep-chilled broilers. J. Food Sci. 47:1763. Anonymous. 1986a. Inside stuff. Meat Ind. 32(7~: 118. Anonymous. 1986b. Hot dogs. Consumer Reports June, 364. Baker, R. C., and C. Bruce. 1986. Development of a low cholesterol and low calorie egg blend. Poultry Sci. 65(Suppl. 1):8. Baker, R. C., and J. M. Darner. 1977. Functional and organoleptic evaluation of low cholesterol egg blends. Poultry Sci. 56:181. APPENDIX Baker, R. C., D. Scott-Kline, J. Jutchison, A. Good- man, and J. Charvat. 1986. A pilot plant study of the effect of four cooking methods on acceptability and yields of prebrowned battered and breaded broiler parts. Poultry Sci. 65:1322. Barbut, S., A. J. Maurer, and R. C. Lindsay. 1986. Effects of reduced sodium chloride and added phos- phates on sensory and physical properties of turkey frankfurters. Poultry Sci. 65(Suppl. 1):10. Bender, A. E. 1978. Food Processing and Nutrition. New York: Academic Press. Boldt, W. A. 1981 (October 20). Liquid egg blend. U. S. Patent 4,296,134. Bowers, J. A., and B. A. Fryer. 1972. Thiamine and riboflavin in cooked and frozen, reheated turkey. J. Am. Diet. Assoc. 60:399. Brasch, A., and W. Huber. 1948. Reduction of un- desirable by-effects in products treated by radiation. Science 108:536. Brekke, C. J., and T. A. Eisele. 1981. The role of modified proteins in the processing of muscle foods. Food Technol. 35(5):231. Calloway, D. H., E. R. Cole, and H. Spector. 1957. Nutritive value of irradiated turkey. J. Am. Diet. Assoc. 33:1027. Calvi, B., G. Kasaoka, A. Jarboe, and G. Kuester. 1984a. Animal blood protein as a food ingredient. Memorandum of Screening and Surveillance 3(1):5. Washington, D. C.: U. S. Department of Agriculture. Calvi, B., G. Kasaoka, A. Jarboe, G. Kuester, and C. Spenser. 1984b. Edible bone protein. Memorandum of Screening and Surveillance 3~3):25. Washington, D. C.: U. S. Department of Agriculture. Campbell, C. L., T. Y. Lin, and B. E. Proctor. 1958. Microwave vs. conventional chicken. J. Am. Diet. Assoc. 34:365. Causey, K., M. E. Hausrath, P. E. Ramstad, and I. Fenton. 1950. Effect ofthawing and cooking methods on the palatability and nutritive value of frozen ground meat. 2. Beef Food Res. 15:249. Chang, I. C., and B. M. Watts. 1952. The fatty acid content of meat and poultry before and after cooking. J. Am. Oil Chem. Soc. 29:334. Cheldelin, V. H., A. M. Woods, and R. J. Williams. 1943. Losses of B vitamins due to cooking of foods. J. Nutr. 26:477. Childs, R. E., W. K. Whitehead, and E. J. Lloyd. 1976. Automated Blood and Lung Collecting and Handling Systems for Poultry Processing Plants. Marketing Research Report No. 1062. Washington, D. C.: U. S. Department of Agriculture. Cook, B. B., A. F. Morgan, and M. B. Smith. 1948. Thiamine, riboflavin, and niacin content of turkey tissues as affected by storage and cooking. Food Res. 14:449. Cotterill, O. J. 1981. A Scientist Speaks about Egg Products. American Egg Board Report No. 1460. Park Ridge, Ill.: American Egg Board.
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Representative terms from entire chapter: