| Summary: | 碩士 === 國立中興大學 === 畜產學系 === 88 === Study on Quality of Frozen Taiwan Country Chicken
Tze-ren Feng
ABSTRACT
In this study, the experiments were divided into three parts. In trial I, the differences of carcass characteristics and the carcass appearance during freezing at -20℃ between Taiwan country chickens and broilers were determined. The carcass characteristics included the concentration assay of whole blood hemoglobin, the blood color CIE L values (lightness), a values (redness), and b values (yellowness), fat content and pigment analysis of the muscle, and approximate compositions, thickness and total collagen contents of skin were determined. In trial II, the chickens were stunned by ether for treatments and then bleeding rate, muscle pigments concentration, carcass color CIE L.a.b were observed to find out the effection of unconscious stunning on carcass color during freezing at -20℃. It could be realize that the stunning method was concerned with Taiwan country chicken carcasses occurred hemorrhage-like phenomena during freezing storage. In trial III, the study was investigated the improvement of the carcass appearances of Taiwan country chickens immersed by cool 0.85% NaCl solution and 1.5% lactic acid during freezing storage.
In trial I, in the concentration of whole blood hemoglobin, Taiwan country chickens were significantly higher than broilers (P<0.05). And the male Taiwan country chickens were higher than the female ones, but there were no significant difference in sex of broilers (P<0.05). In blood color, Taiwan country chickens had a higher a value,lower L and b value than broilers (P<0.05). In fat contents of muscle and skin, broilers were higher than Taiwan country chickens. Besides, the female chicken was higher than the male ones. In skin thickness, Taiwan country chickens also showed a thinner thickness than broilers, and the male chickens were thinner than the female ones. And thighs were much thinner than breast and back regions. In total collagen contents of skin, Taiwan country chickens were higher than broilers; comparison of regions on skin thickness, the thighs were thinner than backs and breasts. In muscle pigment analysis, Taiwan country chickens were higher than broilers in total pigments and myoglobin concentration (P<0.05), and the male chickens were significantly higher than the female ones (P<0.05), and in regions, thighs were higher than breasts and backs. Male Taiwan country chickens had lower b value and higher a value than the female ones and broilers in male and female during frozen storage. However, the female Taiwan country chickens appeared a similar a and b value to broilers. In regions, thigh were reddest than other regions.
In trial II, the ether stunning treatment had a higher bleeding rate than the control. In muscle pigment analysis, the ether stunning treatment was significantly lower than the control in total pigments and the concentration of myohemoglobin (P<0.05). In carcass color, ether stunning treatment was similar to control in redness after slaughter, but ether stunning treatment had a lower red value than control during freezen storage at -20℃.
In trial III, carcasses color of cool 0.85% NaCl solution and dister water (control treatment) immersion were determined after immersed for 60 minutes. The results showed that the cold NaCl immersion treatment were significantly increased L value, but decreased a and b values (P<0.05). Cold NaCl immersion treatment also caused a lower a value and higher L value than the control (P<0.05) during frozen storage at -20℃. In carcass color after immersed with 1.5% lactic acid and dist. water (control treatment) for 10 minutes, the lactic acid treatment significantly increased a and b value, but decreased L value. However, lactic acid immersion treatment showed a lower a value than the control during frozen storage at -20℃. In muscle pigment assay, both cold NaCl solution and lactic acid immersion decreased a value than the control. Comparing to the regions, it showed that the discolored ability of breasts and backs were more effective than thighs.
Key words: Taiwan country chicken, frozen, quality.
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