猕猴桃多酚在羊肉反复冻融过程中的改善肉质和延缓氧化作用

反复冻融会造成羊肉品质下降，为明确猕猴桃疏果多酚在羊肉反复冻融中的作用，从而达到保持羊肉品质、延缓羊肉氧化、延长冻融羊肉货架期的目的。本研究用猕猴桃疏果多酚、表儿茶素、叔丁基对苯二酚（tert-butyl hydroquinone，TBHQ）对羊肉浸泡，进行1、3、5 次冻融处理，测定羊肉汁液流失率、显微结构、物性指标、pH值、色泽及肌红蛋白氧化状态、硫代巴比妥酸反应物（thiobarbituric acid reactive substances，TBARS）值、挥发性盐基氮（total volatile base nitrogen，TVB-N）值及羊肉脂肪酸相对含量。结果发现，随着冻融次数的增加汁液流失值呈增加趋势，在冻融结束时，疏果多酚组的汁液流失率较表儿茶素、TBHQ及空白组分别降低了17.57%、16.83%和40.10%（P＜0.05）；在冻融期间，羊肉在疏果多酚处理下有利于维持其肌纤维结构的完整性，可以减缓冻融羊肉硬度过度降低（P＜0.05）；pH值随冻融次数的增加而降低，冻融5 次结束后，疏果多酚组的pH值最高且比表儿茶素组显著升高了4.55%（P＜0.05）；羊肉的a*值和氧合肌红蛋白相对含量均随着冻融次数增加而降低，而高铁肌红蛋白相对含量呈先下降后上升的趋势，在冻融结束时，疏果多酚组的高铁肌红蛋白相对含量最低为34.01%（P＜0.05）；随着冻融次数的增加，TBARS值呈上升趋势，在冻融5 次时，疏果多酚组的TBARS值比表儿茶素组、TBHQ组及空白组显著降低了11.92%、16.12%和28.21%（P＜0.05）；随着冻融次数的增加，羊肉中饱和脂肪酸相对含量呈下降趋势，单不饱和脂肪酸（monounsaturated fatty acids，MUFA）相对含量呈上升趋势，多不饱和脂肪酸相对含量保持稳定，疏果多酚组的MUFA相对含量在冻融3 次达到最高值为56.59%；4 组羊肉的TVB-N值随着冻融次数的增加而增加，在冻融期间，疏果多酚组的TVB-N值都显著低于其余3 组（P＜0.05）。因此，猕猴桃疏果多酚能改善羊肉的品质，延缓氧化，同时有利于猕猴桃疏果资源的综合利用。

Polyphenols from Thinned Young Kiwifruits Improved Meat Quality and Delayed Lipid Oxidation in Goat Meat under Repeated Freeze-Thaw Treatments

Repeated freezing and thawing can cause the deterioration of goat meat quality. This study was designed to investigate the effect of thinned kiwifruit polyphenols in delaying lipid oxidation and improving the quality of goat meat. Goat meat was soaked in separate aqueous solutions of thinned kiwifruit polyphenols, epicatechin and tert-butyl hydroquinone (TBHQ), and then was frozen-thawed once, three or five times. The drip loss, microstructure, physical properties, pH, color, myoglobin oxidation state, thiobarbituric acid reactive substances (TBARS) value, total volatile base nitrogen (TVB-N) and fatty acid contents of goat meat were determined. The results showed that the drip loss rate increased with increasing number of freeze-thaw cycles, and the drip loss rate of the thinned kiwifruit polyphenol group was significantly reduced by 17.57%, 16.83% and 40.10% respectively compared with the epicatechin, TBHQ and blank groups (P < 0.05) after five freeze-thaw cycles. During freeze-thaw cycles, thinned kiwifruit polyphenols could maintain the integrity of the muscle fiber structure and slow down the excessive decrease in the hardness of goat meat (P < 0.05). The pH decreased with the number of freeze-thaw cycles, and the pH of the thinned kiwifruit polyphenol group was significantly 4.55% higher than that of the epicatechin group (P < 0.05). The a* value and the xymyoglobin content decreased with increasing freeze-thaw cycles, while the relative content of metmyoglobin decreased first and then increased. After five freeze-thaw cycles, the thinned kiwifruit polyphenol group showed the lowest metmyoglobin level (34.01%). The TBARS value showed an upward trend with increasing freeze-thaw cycles. The TBARS value of the thinned kiwifruit polyphenol group was significantly 11.92%, 16.12% and 28.21% lower than the epicatechin, TBHQ and blank groups (P < 0.05) after five freeze-thaw cycles, respectively (P < 0.05). As the number of freeze-thaw cycles increased, the relative content of saturated fatty acids (SFA) decreased; the relative content of monounsaturated fatty acids (MUFA) showed an upward trend, while the relative content of polyunsaturated fatty acids (PUFA) remained stable. The relative content of MUFA in the fruit thinned polyphenol group reached the highest value (56.59%) after three freeze-thaw cycles. The TVB-N value of goat meat in the four groups increased with increasing freeze-thaw cycles. During the freeze-thaw period, the TVB-N value of the thinned kiwifruit polyphenol group was significantly lower than that of the other three groups (P < 0.05). It can conclude that thinned kiwifruit polyphenols can improve the quality of goat meat and delay lipid oxidation.