A comparative experimental study of thawing of frozen pork legs of different weights in air, water and vacuum steam heat systems has been made with respect to thawing time, weight loss and appearance, and a mathematical model and computer programme have been developed which enable accurate prediction of thawing time for any weight of leg under any thawing condition. Very good agreement has been obtained between computed figures and experimental results.Thawing in water is faster than in air at any given temperature but vacuum thawing is not appreciably faster than water thawing. The pork legs increased in weight by 1 2 0.3% under all conditions except high velocity air and highei vacuum thawing temperatures when losses of up to 1 % were recorded. The appearance of legs thawed in air was superior to those from water and vacuum systems. Satisfactory microbiological results were obtained at a thawing temperature of 10 "C in all systems.

Eight groups of six pigs were obtained, two sources of supply x meal-fed and swill-fed x ''light'' (37 to 35 kg) and "heavy" (66 to 88 kg). The pigs were slaughtered, weighed, graded, chilled, split and the sides wrapped in stockinet and polyethylene, frozen in a room at below -30 "C and stored commercially at below -20 "C.Corresponding sides were withdrawn after four and nine months, weight losses were measured and samples cooked and submitted to a panel for appraisal of any differences in flavour. Samples of the fat of each side were also investigated chemically for extent of oxidation of the fat.There were no significant differences in flavour attributable to weight range, with either meal-or swill-feeding nor any chemical indication of oxidative rancidity.

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