"Cooperative Meat Investigations," uses seven numbers and terms to designate the tenderness of the sample. They are: very tender, tender, moderately tender, slightly tough, tough, very tough, and extremely tough. Each judge forms his own standards from the basis of his experience. If the judge has had a complete range of qualities on which to base his standards and is consistent in adhering to them, he may become very proficient in judging comparative tenderness.

Numerous mechanical devices have been devised for estimating the tenderness of meat. The ones most commonly used at present are: (1) the shearing apparatus, which registers the number of pounds required to shear a piece of meat of a given diameter; (2) the penetrometer, with which a specially constructed needle may be used; and (3) a puncturing gage.

Results of tenderness tests. There has been considerable discussion as to whether raw meat is tenderer or tougher than the same meat when cooked, which to date has not been settled. Moran and Smith, after studying the effect of ripening on tenderness of beef, say: "It is a matter of general experience amongst those accustomed to raw meat that cooked meat is tougher than raw meat." They also quote Stefansson from "The Friendly Arctic" as follows: "Cooking increases the toughness and brings out the stringiness. I have never eaten any raw meat that was noticeably tough or stringy."

Black, Warner, and Wilson have reported that cooked samples were more tender than raw samples from good and medium-grade three-year-old grass-fed steers and steers fed both grain and grass. The number of steers in each lot was eight, the number of tests for raw and cooked meat was 12 and 4, respectively. Their results are given in Table 28.

Shearing Strength of Right and Left Raw Twelfth-Rib Samples and Left Cooked Eleventh-Rib Samples (Black, Warner, and Wilson)

Lot designation

Shearing strength raw muscle

1bs.

Shearing strength cooked muscle

1bs.

Good grade, grain on grass.........................................

72. 9

32. 7

Good grade, grass alone.............................................

72. 6

39. 0

Medium grade. grain on grass...................................

71. 7

34. 9

Medium grade, grass alone.................

78 .3

38. 8

Noble, Halliday, and Klaas found beef more tender, as tested by a penetrometer, when heated to 61 °C. than to 75°C.

Lowe compared the penetrometer and shearing apparatus by using both tests to measure the tenderness of the longissimus dorsi of raw and cooked beef rib roasts. The roasts were used in pairs, one roast being cooked, the other left raw. Both methods indicated raw meat to be the tenderest, the rare intermediate, and the well-done the least tender. But penetration tests appear to be influenced by the density of the meat, the meat with the greatest cooking losses, i.e., the well-done, being firmest. Thus penetration tests indicated no difference in meat from different animals when there was little difference in firmness but where both the shearing tests and grading score indicated a range in tenderness. The penetration depth was greater in soft raw meat than in firm cooked meat, the differences being highly significant. Shearing tests showed significant difference in the tenderness of the longissimus dorsi from animals of varying grade and the values obtained were in agreement with the grading score. None of the correlations between penetration and shearing tests were significant, from which it was concluded that shearing was the better method for measuring the tenderness of meat.

Means of increasing tenderness. The possible ways of increasing the tenderness of meat may be classed as follows: (1) mechanical, (2) enzyme action, and (3) by peptization and increased solubility of the proteins. The first is a physical, the last two would bring about chemical changes.

Meat is ground to break the fibers and connective tissue, which, because it lessens the need for chewing, increases the tenderness. For very tough cuts this is probably the most satisfactory procedure. In tests that have been made, it was found that meat, ground fine and several times as for Swedish Meat Balls, is more juicy and palatable than meat ground medium or coarse and only once.

Investigators have sought for suitable enzymatic and chemical means of increasing tenderness of meat for years. The proteolytic enzymes found in the meat increase the tenderness but considerable time at low storage temperatures is required. Hence, if a proteolytic enzyme that would speed up the breakdown of the proteins and which would give satisfactory results were found the tenderness of meat could be increased in a shorter storage period. Papain has been tried. The author's results to date with this enzyme have not been satisfactory. When it was applied to the surface of the meat some time was required for the enzyme to act and then only a thin, powdery surface layer Was formed. When it was applied just prior to cooking the heat destroyed the enzyme, so that its application was of little or no value. No satisfactory methods of injecting this enzyme have been reported. Investigations that have been reported in connection with flour proteins suggest that it is possible that meat may contain substances that tend to inhibit the action of the proteinases of the meat and if some salt that would counteract this inhibition through oxidation or other means could be injected that the meat would become tender more rapidly.

The changing of collagen of the connective tissues or structural proteins to gelatin during cooking is one means of increasing the tenderness of these proteins, but the solubility of the protoplasmic proteins decreases when they are coagulated by heat.

Another method of increasing the tenderness of meat would be through the use of substances that would peptize both or either the connective or protoplasmic meat proteins, thus increasing their solubility and the tenderness of the meat. Means of bringing about peptization have been discussed in Chapter I (The Relation Of Cookery To Colloid Chemistry). Sugar peptizes some proteins. Many electrolytes also bring about peptization, particularly if mixed intimately with the substance to be peptized. Anions of acids such as tartrate, citrate, and acetate may bring about a greater or lesser degree of peptization. A practical peptizer, if such could be found and used, would be a salt that could be injected and have slight effect at low temperatures but bring about peptization fairly rapidly when heated during cooking of the meat.

Smith states: "It is of interest to note that, in cases where the primary aim of cooking is to make the meat more tender (as, for instance, in stewing), the required degree of tenderness can be reached more quickly by addition of phosphate, or what amounts to the same thing, since the meat itself contains phosphate, of concentrated stock from a previous boiling. The concentration of phosphate which gives the greatest effect is about 0.2M, but a quarter of this will have quite an appreciable effect. A suitable mixture of mono- and di-hydrogen phosphates to give a pH between 6 and 7 was employed."

Meat is sometimes placed in a pickle of equal parts of vinegar and water and is used for Sauerbraten or similar dishes. Soaking in the acid is supposed to increase the tenderness as well as develop a particular flavor of the meat. If the vinegar contains tannins, the meat should not be cooked in an iron utensil, for a dark color will develop from the tannins combining with the iron. The effect of the acid on the meat, which will probably depend upon the amount of acid added and the resulting pH of the meat and whether this pH is at, above, or below the isoelectric point of its proteins, may cause the connective tissue to swell and hydrolyze the collagen to gelatin more rapidly when the meat is heated. Tomatoes or sour cream are also added to Swiss steak and tomatoes to stews. Sometimes the acid appears to increase the tenderness; but often a paired cut without the acid is as tender or more tender than the one to which acid is added.

Baker states that the lactic acid developed in the meat may be responsible for improvement in tenderness. He says that Walsh investigated the development of acidity in lean beef and claims that its formation is important in the preparation of canned meats. Properly matured meat, after canning, "melts in the mouth," the muscle fibers are softened, slicability is enhanced, and the pink color is more vivid. But in maturing or ripening changes are also brought about by enzymes and other means.