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.