Experimental cookery

Storage of meat in the home. Proper storage of meat in the home is often a problem. Halves and quarters of dressed animals have a natural protective skin covering. But when wholesale cuts are divided into smaller parts, the surface area for contamination and the contamination both in- crease from these cut surfaces coming in contact with meat blocks, hands, wrapping paper, and kitchen and refrigerator utensils. In general, unless frozen, meat should not be stored long in the home. Low temperatures and 214 MEAT dry circulating air increase the storage life of meat. Burnett found roasts keep best, steaks and chops next, and ground meat most poorly. Rigor. During rigor meat is less tender than after the passage of rigor, so that rigor is of interest in meat cookery. Cause. The exact cause for the development of rigor is not known. Hardy has suggested that two reversible reactions occurring in living muscle, namely, glycogen ^ lactic acid and phosphagen ^ phosphoric acid and creatine, are no longer reversible and after death proceed in one direc- tion with the accumulation of lactic acid and creatine in the tissues. Lactic acid has some role in the development of rigor, as rigor is usually accompanied by or preceded by increase in lactic acid. But, Moran states, under certain conditions, i.e., if an animal has been treated with insulin or iodoacetic, rigor develops without the production of lactic acid. He also adds that there are a number of chemical reactions which take place at death that have not been defined and among them will be found the cause or stimulus leading to the changes in the state of the proteins. Time of onset of rigor. At ordinary temperatures rigor is usually com- plete in 10 to 12 hours. Rigor is supposed to develop more slowly at lower and more rapidly at higher temperatures. But Smith found the effect of temperature on the rate of onset of rigor to be variable. Only skeletal muscles develop rigor. The proportion of soluble protein is sometimes given as an explanation of why some muscles develop a greater degree of rigor than others. Skeletal muscles contain a higher percentage of soluble proteins than smooth muscles. The carcass of the pig generally does not develop rigor, but occasionally one does. It is therefore interesting to surmise whether this is due to a small proportion of soluble protein or to other causes. H there is more lactic acid than usual in the muscle of the animal when killed, as happens when an animal is hunted or a chicken is chased before killing, rigor sets in more quickly. Benson has reported that rigor sets in more rapidly in fatigued fish muscle (trawl-caught) than in the muscle of fish taken from a pen. Changes occurring during rigor. In addition to the development of turgidity, other changes occur simultaneously, for enzyme action does not cease at the time of slaughter. There is evolution of heat known as the heat of rigor. The glycogen practically disappears from the tissues and this glycogen loss parallels the lactic acid increase. Moran states that for mammalian muscle the lactic acid reaches a value of approximately 0.8 per cent. The pH of the muscle falls from pH 7.2 or 7.4 to about pK 5.6 or 5.8, sometimes as low as />H 5.3. Because of various factors, such as amount of glycogen to form lactic acid, the p\l reached during rigor varies somewhat.