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Heating of meat causes certain physical chemical changes in muscle proteins which affect the quality of cooked meat and meat products. Changes in protein solubility, in the adenosinetriphosphatase activity of myosin, or in the contractibility of the muscle fiber have been used by others to determine the extent of denaturation of meat proteins. In this study the changes in the hydration of muscle were studied because this factor is more directly correlated with the quality of meat (28,31, 66, 67). It is known that heating releases juice, that the amount of juice depends on the temperature, and that this loss of water influences juiciness and texture of meat (4,28,36, 43, 66, 68). In this study we have investigated in some detail the influence of different temperatures on the hydration of beef muscle.An investigation of the influence of temperature on the pH-dependence of water-holding capacity will give information concerning changes in meat quality and also the mechanism of denaturation. This is because changes in protein net charge and in steric conditions affect meat hydration in a pH range from pH 3.0 to 7.5 (34).In addition we have determined the acidic and basic groups in muscle and the solubility of the globular and structural muscle protein after heating at different temperature. METHODSUtility cows from 4 to 6 years of age were used. Two to 3 lb of the longissimus dovsi muscle were cut from the carcass 5-6 days after slaughter. Connective tissue and fat were removed as far as possible. The muscle was ground twice in a cooled meat grinder.Influence of pH on the water-holding capacity of meat after heating at different temperatures.One hundred g of ground meat at 20" C was minced in a homogenizer with 30 ml ice water at high speed for 30 sec. During mincing the metal homogenizer vessel was cooled by ice.For heating meat, the covered metal vessel of a homogenizer, filled with 110 g of ground meat, was placed in a water bath of the desired temperature.The meat was heated with occasional stirring until it was at the temperature of the water bath and was kept there for 30 min. [Other authors have shown that after 30 min heating at 70-90" C protein hydration changed very little (43, 6011. Then the vessel with meat was put in ice for about 15 min. Thirty-three ml ice water was added to bring the added water to 30%. The mixture was minced in an ice-cooled homogenizer in the same way as the fresh meat. It was considered that the different texture of heated muscle has an influence on the extent of mincing and, therefore, oh the water-holding capacity; however, we found that this effect has no influence on the relative difference of hydration produced by heating.

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