DETERMINATION OF DIFFERENCES IN FREE AND BOUND WATER CONTENTS OF BEEFMUSCLE BY DSC UNDER VARIOUS FREEZING COMBINATIONS

The differences in bound water content of beef semimembranous muscle s amples obtained from previously chilled (24 h at +4 degrees C) middle- aged beef carcasses were determined by the use of DSC. Initially, samp les obtained from fresh, unprocessed meat were frozen at -40, -50 or - 65 degrees C to determine their melting peaks for freezable water (fre e water) content with the use of DSC. The samples were then subjected to an environment with an ambient temperature of -30, -35, -40 or -45 degrees C, with no air circulation, or with an air circulation speed o f 2 m s(-1), until a thermal core temperature of -18 degrees C was att ained; this was followed by thawing the samples until a thermal core t emperature of 0 degrees C was reached. This process was followed by su bjecting the samples to the ambient temperatures mentioned above, to a ccomplish complete freezing and thawing of the samples, with DSC, and thereby determination of the freezable water contents, which were then used to determine the peaks of melting. The calculated peak areas wer e divided by the latent heat of melting for pure water, to determine t he freezable water contents of the samples. The percentage freezable w ater content of each sample was determined by dividing its freezable w ater content by its total water content; and the bound water content o f each sample was determined by subtracting the percentage free water content from the total. In view of the fact that the free water conten t of a sample is completely in the frozen phase at temperatures of -40 degrees C and below, the calculations of free and bound water content s of the samples were based on the averages of values obtained at thre e different temperatures.