Abstract
The purpose of this paper is to compare the viscoelastic properties between breast and thigh meat in the chickens of different ages by means of stress relaxation test, and to investigate the effect of dietary fat levels on their meat. The chickens used were Cornish×White Rock raised in individual wire cages. The number of chickens used was 52 in total, and they were all females. They were divided into 3 groups, and fed with the experimental diet containing 0%, 5% and 10% soybean oil, respectively. The experimental periods were 10, 20 and 34 weeks from day-old. Just after slaughter, the breast meat (M. pectoralis profundus) and the thigh meat (M. iliotibialis) were removed. They were immediately put into polyethylene bag, and were kept at -17°C at least for 24 hours. Several pieces (50mm in length, 20mm in width and 2-4mm in thickness) were taken from each chicken meat by a microtome in such a way that long axis of each piece was parallel to the direction of muscle fibers. Then, these pieces were stamped out with a dumbell-shaped apparatus. The stress relaxation measurement of these samples was carried out with a chainomatic balance Food Rheometer (Tabai Co., Ltd.). These samples were stretched 13.5mm at a speed 2.8mm/sec and were kept for 5min in a chamber with 50±5% of relative humidity at 30±1°C. The parameters obtained from stress relaxation test were Fmax (gw), τ (sec), and S/f0(%). The following imformations were obtained. 1) Fmax value was larger in thigh meat than in breast meat in each group (P<0.01), therefore, thigh meat seemed to be stronger than breast meat as to Koshi (Body). 2) τ value of chicken fed with soybean oil free diet was larger in thigh meat than in breast meat (P<0.05), the thigh meat seemed to be more elastic than the breast meat. 3) In the age of 34 weeks old, S/f0 value of chicken fed with soybean oil free diet was larger in thigh meat than in breast meat (P<0.05), therefore, the structure of the thigh meat seemed to be firmer than that of the breast meat. 4) The result of this experiment suggested that the viscoelastic properties of raw breast and thigh meat of chickens were not affected directly by the dietary fat levels. The role of intramuscular fat on chicken meat tenderness seemed to serve as secondary factor.
