T H E FLAVOR O F MEAT AND MEAT PRODUCTS’

PAUL E. HOWE AND NICHOLAS G. BARBELLA United States Department of Agriculture, Bureau of Aiiimal Industry,

Washington, D. C.

(Received for publication, May 22, 1937)

Meat flavors may be defined as those qualities in meat that affect the taste. They are the result of the action of stimuli, chemical in nature, on the various taste buds of the tongue. Depending on the concentration and intensity of the various stimuli a greater or fewer number of the taste buds will be acted upon, hence the general response obtained from different substances will vary. I n meat there are several flavoring substances that may be recognized with the added possibility of new compounds formed during cooking.

The United States Department of Agriculture, in cooperation with various state experiment stations, has been engaged for over ten years in a study of the quality of meat and the factors that modify it. The complex problem of flavor has been considered in a subjective man- ner ; little has been accomplished objectively. I t is necessary, there- fore, to t ry to bring toget.her facts that have been developed by obser- vation and a few experimental results.

VARIOUS QUALITIES CONTRIBUTING TO FLAVOR

Before discussing the factors affecting flavor in meat, reference should be made to certain other factors often considered as con- tributing to flavor, although they may not belong strictly under such a heading. Two such factors are (‘smoothness,” or the lubrica- tion of the lipids, which contributes to a quality that might be desig- nated as “richness” of the meat and to the quantity of juice. I t is possible that some persons associate tenderness, or the degree of resistance to pressure by the mouth and teeth, and texture of meat as factors in flavor. The appearance of meat also influences its flavor for some persons. It is obvious, then, that the flavor of meat should be recognized as a combination of a number of variable factors which undoubtedly leave different impressions with different persons but which each recognizes as a meat flavor.

Meat flavor, however, in its truest sense, consists of the stimuli given to the taste buds by the inherent organic and inorganic sub- stances, such as water soluble extractives, lipids, small amounts of

‘Read before a symposium on Flavors in Foods at the Chapel Hill, North Carolina, meeting of the American Chemical Society, April 12 t o 15, 1937.

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198 P A U L E. H O W E A N D NICHOLAS G. BARBELLA

carbohydrates and salts, o r compounds produced from these products and proteins by cooking, by enzyme action, or by both.

DETERMINING I N H E R E N T DIFFERENCES I N FLAVOR

In planning studies to determine the inherent differences in the flavor of fa t and lean-the differences owing to factors of breed, feed, o r management-care must be taken to avoid or standardize the effects of cooking or enzymes or other factors on meat flavor and to include samples of meat that are as similar as possible.

The development of meat flavors has been described by Grindley and Emmett (1905)' as due very largely to cleavage of extractive bodies in the meat juice and to cleavage of the fa t under the influence of heat. Rare cooked meat has been found least affected by heat. The flavors, therefore, consist of the natural unchanged or slightly changed flavor of the fats and extractives. In beef, the meat most often cooked only to the rare stage, there is an acid taste probably from lactic acid, phosphates, etc. Such acidity is most often observed in beef from young cattle. This observation does not agree, however, with the alkaline taste described by Grindley and Emmett from meat juice heated to 65"C.(149"F.). At 65"C., according to Grindley and Em- mett, an unpleasant alkaline flavor develops in the juice, which is not modified by continued cooking at 65 to 100°C. (149 to 212°F.). Changes produced in the dried juice or soluble par t of the meat by temperatures over 100°C. are in a large measure responsible for the flavor of meat cooked by dry heat. A characteristic flavor is produced in fa t ty tissue which becomes more pronounced at higher temperatures, especially where browning occurs. These changes in fa t and other substances are apparently due to cleavage produced by heat. Beyond these gen- eral facts little is known of the nature of the chemical compounds formed.

Studies on the quality of meat have been planned by the U. S. Department of Agriculture especially to determine whether or not there are differences in the inherent flavor of the lean and fat. The method of handling meat and the length of preliminary storage o r ripening period of dressed meat have been carefully standardized. Cooking, also, has been largely restricted to the medium rare stage. I n carving, care is taken that the sample to be judged is not con- taminated by the developed flavor from the browned outer surface or extra fat. The lean and f a t samples are taken from the interior of the roast.

'Grindley, H. S., and Emmett, A. D., 1905. Studies on the influence of cook- ing upon the nutritive value of meats a t the University of Illinois, 1903-1904. U. S. Dept, Agr., Office of Experiment Stations, Bul. 162.

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The palatability studies are conducted by a trained group of judges who pass on both desirability and intensity of flavor in addition to other characteristics of meat. Both fa t and lean are judged warm and unsalted. Odors are considered briefly under the terms of intensity and desirability of aroma. Roasted or broiled meats have two zones of flavor-the outer portion that has been subjected to high heat and the inner portion that has been heated slowly and chiefly by conduc- tion. Inner flavors are considered to be due to the salts, lactic acid, etc.; outer flavors are those due to the cleavage products produced by roasting o r cooking.

During roasting, boiling, or cooking by other methods very small losses of nitrogen and other non-nitrogenous compounds take place into the air. Part of the water and the solids lost from cooked meat appear in the gravy. The housewife makes use of this rich supply of flavoring agents and applies additional heat for desirable developed flavor in the preparation of brown gravies. The material used is the browned meat juices that have exuded from the meat during cooking. Negative evidence of the effect of heat is found in the gravy from meat. cooked a t low oven temperatures which does not have as strong a meat flavor as that from meats cooked a t higher temperatures. These developed flavors of meat are supplemented by the dextriiiization of the added starch.

It is often said, but not confirmed, that the addition of salt to meat develops the flavor. No work has been reported on the subject. d few experiments have been done by the U. S. Department of Agriculture in adding salt to the samples of meat to be judged in the regular way. It is our opinion that the addition of salt does not increase the inher- ent meat flavor but sets u p new stimuli owing to the salt. This new combination is the result of the enhanced salty flavor. After working with unsalted meat for a period of time the addition of salt often ceases to be necessary for complete satisfaction in eating meat.

An interesting observation mas made in some preliminary tests on different kinds of meat by people -rho were blindfolded. Of the better known meats used in these tests it was found that beef and pork were more intense in flavor and more often correctly identified than chicken, veal, lamb, o r rabbit. While there may be some question about the ability of blindfolded judges to distinguish between lean portions of different kinds of meat that had not been exposed to high heat, the outer portions with the modified extractives and fa t were more easily distinguished. In this case it is probable that the charac- teristics lie chiefly i n a specific constituent of the kind of fat.

200 PAUL E. HOWE AND NICHOLAS G. BARBELLB

FLAVOR DEVELOPED BY AGING OF MEAT

An interesting example of developed flavor is the southern ham. After the ham has been cured and smoked, it is allowed to age for varying lengths of time u p to a year or more. During this time i t be- comes partially dry. The characteristics of such hams are a sharp, cheesy flavor in the lean and a modification of the fat so that it has a slightly rancid taste. This change in flavor is accompanied by a clear- ing of the fa t so that it becomes semitransparent. Clusters of tyrosine crystals are often found in the lean meat. The University of Mary- land has been able to produce certain of the characteristic flavors in ham in a relatively short time, six to ten weeks, by incubating cured and smoked hams at 42 to 52"C.(107.6 to 125.6"F.). Hams cooked after eight weeks of aging did not show as pronounced a cheesy or spicy aroma as those cooked a t the end of ten weeks. In- tensity of aroma increased with aging. The flavor of incubator hams was more pleasing than the strikingly different freshly smoked com- mercial hams.

The chemical study of "quick aging" of hams shows the following changes in the meat:

( a ) Increase in the free fatty acids of both meat fa t and adipose tissue fat. ( b ) Hydrolysis of the protein, resulting in au increase in total soluble amino nitrogen. (c ) Loss of moisture from the lean tissues. The changes are characteristic of the aging process occnrring in hams.

Off or foreign odors and flavors in meat may occur from several causes. They may be noticeable when the animals have eaten cod-liver oil, fenugreek, mint, wild celery, anise oil, o r certain chemicals; also xhen meat is stored in a refrigerator in close contact with certain foods and fruits it often absorbs foreign odors. Occasionally the meat from very old animals, such as bulls, cows, or rams, develops an ex- tremely unpleasant odor during cooking, often characterized as am- moniacal. Sexual odors in tissues are usually associated with boars and with stags that have been slaughtered soon after castration. Little or none of this kind of meat is found in commercial channels. Off- flavors are found occasionally in the meat from apparently normal animals. No explanation for this condition has been discovered.

MEAT EXTRACTS USED TO IMPART FLAVOR

Meat flavors are often extended o r added to other foods through the use of commercially made extracts or juices. These products are

Hunt, W. E., May, 1935. Secret of old ham. The Country Gentleman 105, 18.

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made by separating the nitrogenous extractives from fresh meat with water, removing the fat , and concentrating the liquid portion by evaporation.

Such an extract contains not less than 73 per cent of total solids, of which not oyer 27 per cent is ash, not over 12 per cent is NaC1, not over .6 per cent is fat , and not less than 8 per cent is nitrogen. The nitrogenous compounds contain not less than 40 per cent of meat bases and not less than 10 per cent of creatine and creatinine.

Meat estracts are also prepared rrhich are concentrated a t a lower temperature than the extract of Liebig type, such as that produced by Valentine. Such extracts have less of the developed flavor and are distinctly acid. They contain between 50 and 75 per cent solids. I n this case a large proportion of the creatine is removed.

Yeast extracts and vegetable protein digests are used in flavoring agents to be employed as substitutes fo r meat flavors. Yeast extracts contain no creatine or creatinine. The distribution of the various santhine bases is different in meat and yeast extracts. I n meat es- tracts santhine and hypoxanthine predominate, whereas in yeast extracts adenine and guanine predominate.

The Orientals have established an extensive literature o n hydro- lyzed proteins. mostly of iregetable and fish sources. It is their belief that the glntamic acid, vhich is an important constituent of these hydrolyzed proteins. is the constituent responsible for meat flavor. Moiiosodium glutamate is also recommended by them f o r use as a meat substitute. This conclusion has not been our experience. Several commercial products used as meat flavoring substitutes have been purified and recrystallized many times. This recrystallized material has been offered to judges iii solutions.of high molarity and also in dry form, and meat flavor has not been associated with them. It is our belief that this alleged meat flavor, if present in the original com- pound, must be due to the impurities present rather than to glutamic acid or its non-sodium salt.

SVMMART

There is little concrete evidence as t o the chemical characteristics of meat flavor. The responsible constituents, as ordinarily recog- nized, appear to consist of a composite of salts, acids, and a group of products resulting from heating extractives, possibly disintegration products of proteins, and lipids. The quantity and quality of these products are related to the extent and duration of heating. There are certain inherent flavors in the fat of meat, that are characteristic of species, which become evident when the fa t is heated. Fats con- tribute body, richness, o r smoothness to meat juices or gravies which.

202 PAUL E. HOWE AND NICHOLAS G . BARBELLA

although chiefly mechanical in effect, have much t o do with the desirability of meat. Age of the animal also has an important influ- ence on flavor of the meat, such as baby beef in contrast to beef from more mature cattle and lamb in contrast t o mutton.

Ripening of meat results in an increase in soluble protein products which, when heated, play an important part in the flavor of such meats. New flavors are developed by aging of cured meats, charac- terized by the southern ham. The new flavors are apparently disin- tegration products of protein and fat characterized by such terms as cheesy, pungent, and spicy.