Meat Fats

of Better gives a characteristic pungent odor is responsible for most of the economic losses of fats and fatty foods. Oxidative rancidity in lard is par- Quality ticularly serious. Moreover, most proc- essing that is undertaken to improve Waldo C. Ault, other properties (such as odor and Roy W. Riemenschneider^ color) tends to reduce the stability of Steward G. Morris fats. It has been difficult, therefore, to apply the various processing techniques to lard. The edible meat fats^ lard and tal- Before satisfactory progress could low, are almost completely digestible. be made in understanding oxidative They are high-energy foods and con- rancidity and in producing fats of tain substances necessary for good nu- satisfactory stability, methods for pre- trition. They also are of great economic dicting stability and evaluating anti- importance. Our lard production alone oxidants were necessary. Reasonably amounts to 2/2 billion pounds a year— effective methods for accomplishing approximately equal to the combined those ends are available, but because production of soybean and cottonseed of the many factors involved none of oils. them gives perfectly clear-cut results. It seems strange, therefore, that The methods most widely used are they have received so little attention. the active-oxygen method, frequently Probably that is because they are by- referred to as the Swift stability test; products of the meat-packing industry, oxygen-absorption measurements; in- or because we regard the rapid expan- cuioation tests; and baking tests. sion in the production of soybean oil as The active-oxygen method involves more exciting. Be that as it may, the bubbling purified air or oxygen factors that affect the quality and ac- through the melted fat under stand- ceptance of these fats deserve careful ardized conditions, usually at 210^ F. consideration. The time in hours requiied to develop The properties open to improvement rancid odor or a peroxide content indi- are keeping quality, or stability, physi- cative of rancidity is noted. To an ex- cal characteristics—such as plastic perienced technologist, this tim.e is of range, consistency, and the creaming value as a basis for comparison in pre- power—odor, flavor, color, and smoke dicting the life of a fat or in estimating point (temperature at which a fat or the worth of an antioxidant that may oil begins to smoke). have been added to the fat under test. Stability is the main one. Without By use of suitable equipment, the better keeping quality, the application time a sample of fat requires to reach a of other techniques would have little level of oxygen uptake preestablished value, because the best shortening is as the rancid point may be determined unfit for use if it has a strong odor or under standardized and comparable flavor—if it is rancid. The chief causes conditions. In this instance also, the are atmospheric oxidation, absorption time is of value in predicting the of odors, and the action of enzymes storage life of a fat or in estimating the and micro-organisms. Rancidity that is m.erit of an antioxidant. Workers at the caused by atmospheric oxidation and Eastern Regional Research Laboratory

90:2722°--51 44 671 672 19 5 0-1051 YEARBOOK OF AGRICULTURE reported that results obtained by the bility of the meat fats by feeding an method usually lead to the same con- antioxidant substance to an animal clusions as those of the acti\'e-oxygen before slaughter. The investigators miethod, but because of manipulation reported that of a wdde variety fed, difficulties it is not so generally used. tocopherol was the only antioxidant Keeping quality may also be de- deposited in the adipose tissue to a termined by merely incubating samples significant extent. of fat in open beakers or jars in an In attempting to produce a meat fat oven at a temperature usually of 145° of good stability, it is therefore im- F., although occasionally higher tem- portant to conduct the ]:>rocessing op- peratures are used. A comparison of erations in such a manner as to min- the time required for rancidity to de- imize destruction of any antioxidant velop in each sample is a measure of substances present. That means the their stability. The rancid point may be avoidance of unnecessary exposure of detected by sense of smell or by chem- the fat to fight, air, or high tempera- ical determination of peroxide content. tures. The fat must not be held at high When an effective antioxidant is temperatures while exposed to air for added to a fat, the keeping time of the long periods. It is also important to fat before developnrient of rancidity keep metal contamination as low^ as may be increased fivefold to tenfold. possible. Some metals, in the form of The test methods we have described their salts or oxides, are know^n to have provide an approximate measure of a pro-oxiclant efí'ect; that is, they re- the increase in stability of the fat. duce the stability of fats markedly. However, only a few of the antioxi- That is particularly true of iron and dants that are capable of protecting copper. In fact, copper is such a pow^ cr- the bulk fat wall continue to stabilize ful pro-oxidant that its addition to the the fat after it has been used in baked extent of a few tenths of one part per products. In other w^ords, most anti- million makes lard rancid in about 20 oxidants do not have ^'carry over" into minutes at temperatures of boiling baked goods. Consequently, standard- water. ized baking tests have become neces- Copper or copper-bearing alloys, sary in evaluating antioxidants for therefore, should not come into con- edible fats. In such baking tests, the fat tact with the fat during the handling (with or without added antioxidant) is and rendering processes. It is hardly baked in a pastry or cracker recipe and possible to eliminate au iron from the the stability of the products is noted. equipment, but elimination of rust, The methods for determining the especially following shut-down periods, stability of fats can also be used in helps. Increased stability can be ob- studies aimed at minimizing destruc- tained by equipping the processing and tion of the natural antioxidants in fats rendering departments with aluminum, during processing. stainless-steel, and glass- or plastic- The meat fats have a much lower lined tanks, pipes, and pumps. content of the more elTective natural A process for removing contaminat- antioxidants than do most vegetable ing metals from fats has been de- fats. The naturally occurring antioxi- scribed. The fat is treated with tannic dants include lecithin, or cephalinlikc acid and subsequently filtered. The substances, and tocopherols. Many in- filtration apparently removes the vestigators believe that tocopherols, the metals and the excess tannic acid. efi'ectivc antioxidant of most vegetable If metal contamination is not too oils, are also present in traces in lard great, the metal may be deactivated if they are not destroyed by processing. % adding a compound that unites with Rather extensive experiments at the the metallic ion. Such bound metal has University of Minnesota ofTer little no pro-oxidant properties. Citric acid, hope for increasing the oxidative sta- esters of phosphoric acid, ascorbic acid. iVIEAT FATS OF BETTER QUALITY and esters of ascorbic acid and isoas- less expensive than most of the anti- corbic acids arc examples of edible oxidants. Therefore, their use usually compounds that are metal deactivators results in important economics. Con- in fats. sequently, most of the lard on the mar- The use of such precautions during ket today that has improved stability processing will result in the production contains syncrgistic antioxidant mix- of meat fats with increased stability. tures. The low content of natural aiitioxidant An ideal antioxidant for use in foods substances, however, probably pre- should have the following qualifi- cludes the preparation of meat fats that cations : have stabilities such as are usually Effective stabilizing action under found in the hydrogenated vegetable- conditions of use. oil shortenings unless some substance No harmful physiological effect, that will delay oxidative degradation even in quantities considerably greater is added. Besides the natural anti- than those likely to be used and even oxidants, synthetic compounds that when ingested over long periods of will do this are known. Such substances time. generally contain or consist of com- At least sufficient solubility in fats pounds having quinol, phenol, amino, to facilitate its use; greater solubility or Sulfide groupings. is usually advantageous. The mechanism by which antioxi- Freedom from objectionable odor, dants perform their function is still not color, or flavor even after storage. clear, but an eíTective antioxidant is Stability to whatever processing is always capable of being oxidized in the necessary after it is incorporated in the medium and under the conditions fat. found in the oxidizing substrate. Usu- Protective action which carries over ally the antioxidant will be nearly gone into baked goods. before peroxides develop in appreci- Economy in use and availability in able amounts and before rancidity can amounts needed. be observed. Despite this list of requirements, sev- A large number of compounds bring eral substances have been declared ac- about a marked enhancement of the ceptable as antioxidants for use in lard stability when they are added to fats in federally inspected plants subject to that contain phenolic antioxidants. provisions governing the concentration They are ineíTective, however, in sub- and statements on the label. The sub- strates devoid of natural or added stances include gum guaiac, tocopherol phenolic antioxidants. The compounds concentrates that contain at least 30 are generally referred to as antioxidant percent tocopherol, nordihydroguaia- synergists, or simply synergists. The retic acid (NDGA), propyl gállate, substances most frequently considered butylated hydroxyanisolc, thiodipropi- acceptable synergists for edible pur- onic acid and lauryl thiodipropionate, poses are those already enumerated as corn oil, lecithin, citric acid, and phos- effective metal deactivators, such as phoric acid. The last three are gener- citric acid and ascorbic acid. On that ally considered to have their greatest basis, it would seem that syncrgistic value when used as synergists. If not action could be explained as merely already, certainly in the near future, metal deactivation. In many instances, satisfactory antioxidants wdll be avail- that is undoubtedly true. This single able at low cost. In fact, the cost of mechanism cannot explain the com- some already approved permits sig- plete role of synergists, however, for nificant improvements in stability at a somie compounds are known to exert cost of 10 cents or less for 100 pounds syncrgistic effect wdth antioxidants, of lard. even when no metals are in the fat. An inexpensive and simple process Syncrgistic compounds are relatively for improving the keeping quality of 674 1950-1951 YEARBOOK OF AGRICULTURE home-rendered lard has been devel- erties, and consistency and to elimi- oped at the Eastern Regional Research nate odor, color, and free acidity. Laboratory. The process, which is A fat, such as lard or shortening, at nothing more than the addition of a casual glance, looks like a soft, but about 5 percent of a hydrogenated more or less homogeneous, solid. But vegetable shortening, owes its success at ordinary temperatures it really con- to the high content of tocopherols in sists of a suspension of solid fat par- most vegetable oils. The period during ticles in a liquid matrix. This physical which the lard will remain free from condition is brought about by the rancidity is nearly doubled. Hydroge- presence of a large number of different nated vegetable shortening can be glycerides, which have widely varying bought in any grocery. softening points, so that at any given The addition of antioxidants to lard temperature a part is solid but another must not be considered as a cure for all part is liquid. The plasticity or work- the ills of the industry. ability of a fat depends somewhat on its relative proportions of liquid and THE USE OF BETTER PACKAGING of- solid. fers great possibilities for improving Other factors, not so obvious, that the keeping quality and increasing ac- influence the plasticity of a shortening ceptance by those who use this im- include the size of the solid particles portant commodity. A large percentage and their tendency to form aggre- of the lard sold on the retail market gates—in that respect, the meat fats now is packaged in cardboard cartons, are quite unlike hydrogenated vege- chiefly in the 1-pound size. The pack- table shortenings. Lard particularly age permits ready passage of air to has the peculiar property of solidifying the contents. The paper used in the in such a way that large crystals fre- past to make the cartons and their quently are formed to give a grainy liners often had absorbent properties appearance. The housewife dislikes and took up the liquid part of the lard, this; besides, it indicates a rather nar- somewhat like a wick. Such wicking row temperature range of workability, action separated the liquid part of the which the commercial baker dislikes. fat, which was most susceptible to The lard producer chills the ren- rancidity, in a way that enormously in- dered fat as rapidly as possible by creased its exposure to the deleterious mechanical means so that the crystals action of air. More recently, lining will be small. Fine crystals extend the papers have been developed which are plastic range of the product, give it a much better in that respect. They are smooth appearance, and make a prod- not very convenient, however, and uct of the maximum degree of firm- many users do not like such packages. ness. Lard and hydrogenated lard that A completely satisfactory package cer- have large crystals are afl'ected by vari- tainly should be easy to open and close. ations in temperature. Consequently, Packages more acceptable to con- their plasticity in storage and commer- sumers can be made most readily from cial handling is unpredictable. rigid, nonabsorbent materials, such as Chemical methods for modifying metal or glass. Such packages can be lard to eliminate or minimize graini- evacuated or flushed with inert gas and ness have been proposed. The methods sealed and protect the contents better. are designed to alter the glyceride Suitable antioxidants for protection structure by modifying the characteris- of the fat during processing as well as tic manner in which the fatty acids are during subsequent storage make pos- combined with glycerol to form the fat. sible the application of technological This is accomplished by heating the processes for improving it in other fat in the presence of a small excess of ways. The processes can be used to glycerol or in the presence of a cata- modify the texture, creaming prop- lyst, such as sodium ethylate. Such MEAT FATS OF BETTER QUALITY 675 glycoride modification or rearrange- and odor, the fat tissues must not come ment tends to bring the consistency and into contact with dirty and inedible m.elting point of fat to more definite parts of the carcass. Care must be taken and reproducible values. Such methods to exclude blood, muscle tissue, de- for modifying lard require suitable tached skin, and large blood vessels equipment and considerable scientific from the rendering kettle. Prompt control. chilling of the tissue also will minimize Simpler methods arc available^ for- the formation of free fatty acid, which tunately, for increasing the firmness of results from enzymatic and hydrolytic lard, but they may not offer all the action. Only prompt chilling and ren- advantages of the techniques we de- dering of a fat will give products hav^- scribed. Lard stéarine or hydrogenated ing the desirable low content of free lard is often added for the purpose. fatty acid. Too much fatty acid causes Lard stéarine, the more solid portion a high smoke point. of lard, is obtained as a byproduct dur- Often the color of a lard can be im- ing the manufacture of edible lard oil. proved by treating the fat with an ad- Hydrogenated lard is made by the cata- sorptive agent like carbon or bleaching lytic hydrogénation of lard and subse- clays. Such a refining treatment is quent deodorization. Some experience combined with the rendering opera- is necessary to get the best results, be- tion in the so-called drip-rendering cause both of the agents frequently process. In it, the fat is charged into a vary in their hardening powers, and rendering tank v/ith a false bottom, the consistency of the lard changes through which the lard drains away as from time to time. soon as it separates from the tissues. In A degree of firmness also can be got this way, the time of contact between by a uniform blend of the fat of inter- hot fat and tissue is minimized. The nal organs and the outer parts of the melted fat is then mixed wáth carbon carcass, the cutting fat, which is less in the lower part of the tank. firm than the former. Several new methods for rendering Closely associated with the physical fatty tissues are undergoing evaluation properties of a fat is its creaming and development. Special emphasis is power—meaning its ability to retain a being given to quick rendering and large percentage of air incorporated in simultaneous removal of fat and water a dough or batter in which it is being from the raw tissues without the long used. The creaming power seems to be heating at high temperatures used in associated with the power of the fat to the older methods. Fine grinding of the take up and form stable emulsions with fat tissues, use of proteolytic enzymes, water. Generally speaking, lard does dilute caustic solutions, centrifugation, not cream well. It lacks high emulsify- and solvent extraction have been ing ]3ow(}rs. Both properties may be claimed by various investigators to fa- substantially improved by limited hy- cilitate the rendering. In general, lard drogénation of the lard or by the addi- made by these quick-rendering meth- tion of a small percentage of hydro- ods has somewhat greater stability, genated lard. It is also possible to better color, and is more bland than improve the creaming properties of fats lard made by the older procedures. by adding emulsifying agents, of which It is hardly to be expected that treat- the monoglycerides are the outstanding ment with adsorbents or modifications example. Monoglycerides may be made of the rendering process will produce from lard by reacting it with an excess lard as free from odor and flavor as of glycerol. that obtained by vigorous steam de- Several processes are available for odorization under vacuum, which is reducing or eliminating undesirable the only commercial process now^ feas- color, odor, and free acidity. To pre- ible for ])roducing the bland products vent development of excessive color that the modern housewife apparently 676 1950-lOcl YEARBOOK OF AGRICULTURE wants. Equipment is available for de- factory methods for use by the farmer odorizing lard in cither a batch or con- in improving home-rendered lard. tinuous manner. In general^ the treat- ment consists in subjecting the hot fat WALDO C. AULT was educated at to the action of steam under a high Ohio State University. After 7 years of vacuum. The exact time varies from a experience Í7i industrial research, he few minutes to a few hours, depending joined the staff of the Northern Re- on the type and cfTiciency of the equip- gional Research Laboratory and, later, ment. Because the fatty acids are some- the Eastern Regional Research Labo- what volatile under the conditions ratory, where he now is head of the oil used in deodorization, a significant re- and fat division. duction in free fatty acids may be ROY W. RIEMEN SCHNEIDER was effected during the operation. This trained at Illinois College, University raises the smoke point to the highest of Illinois, and. University of Maryland. possible level, a desirable quality in a He joined the Department of Agri- fat used for frying. culture in 1930. Since 1941 he has been Because lard has reasonably satis- in charge of the composition and qual- factory properties, producers have ity section of the oil and fat division at tended to consider it a finished prod- the Lastern Laboratory. uct. Lard, though, has been losing STEWARD G. MORRIS entered the ground in the competitive race with Department of Agriculture in 1936 and hydrogenated vegetable shortenings, has been with the Eastern Laboratory which once were substitutes but are since 1940. He has been engaged in now generally considered to be setting synthesizing new antioxidants and in the pace. Recently lard has begun to testing antioxidants and metal-deacti- receive more technological and scien- vating compounds in lard. He has a tific attention; the results are the mar- doctor's degree from Columbia Uni- keting of improved products and satis- versity.

WHOLE EGG is about 73 percent water. The solid material is principally pro- tein and fat. The solids, w^hich are responsible for the unique properties of eggs, are approximately 50 percent protein, 40 percent fat, and 10 percent other substances, including dextrose, salts, and carotenoids. Egg w^hite contributes about 32 percent of the whole-egg solids and about 60 percent of the Q,^g protein. Its solids are mainly proteins, eight of which have been identified and six of which have been isolated and characterized. The proteins and their approximate percentages of egg-white solids are: Ovalbumin, 50-60; ovomucoid, 10-12; conalbumin, 10-12; ovomucin, 2.5; lysozyme, 2.5; and avidin, 0.1. Egg yolk contributes about 6S percent of the w^holc-egg solids and nearly all of the fat. Its solids consist of more than 50 percent uncombined fat and about 37 percent proteins. Part of these proteins are combined with fats (lipoproteins). A dozen medium eggs (about 1,4 pounds) are approximately equivalent in protein value to 1 pound of beef and in fat value to 0.2 pound of butter or margarine. On an equal-weight basis, eggs are equivalent to beef as a source of thiamine (vitamin Bi) and iron, and are twice as good a source of riboflavin (vitamin B,). They are about one-third as good a source of vitamin A as butter. Beef contains no vitamin A; eggs contain no vitamin C. In nutritional value, the egg is second only to milk.—Hans Lineweaver and Robert E. Feeney, Western Regional Research Laboratory,