不同类型桃果实采后糖酸代谢的差异性分析

为了探讨不同类型桃果实糖酸代谢的差异性及采后风味劣变的机理,从而为适宜采收成熟度的选择奠定理论基础,以不同成熟度的‘沪油018’油桃、‘湖景蜜露’水蜜桃和‘玉露’蟠桃为试材,对其果实在采后糖酸代谢的规律和差异性进行了研究。结果表明:1采收时,七、八、九成熟的‘沪油018’其果实中的蔗糖含量间无显著性差异,八成熟‘湖景蜜露’水蜜桃果实中的蔗糖含量显著高于其七成熟果实,七成熟‘玉露’蟠桃果实中的蔗糖和山梨醇含量均显著高于其八成熟果实;‘玉露’蟠桃果实中的蔗糖含量(82.8~91.49 mg·g~(-1))显著‘湖景蜜露’水蜜桃(77~87 mg·g~(-1))‘沪油018’(55~60 mg·g~(-1));七、八成熟‘沪油018’和‘湖景蜜露’水蜜桃果实中的苹果酸和总酸含量间的差异均不显著,七成熟‘玉露’蟠桃果实中各游离酸和总酸含量均显著高于(P≤0.05)其八成熟果实;‘玉露’蟠桃和‘沪油018’果实中的苹果酸含量均显著高于‘湖景蜜露’水蜜桃。2室温贮藏期间,3种类型桃果实中蔗糖和总糖含量的变化均较缓和;七、八成熟‘玉露’蟠桃和‘沪油018’果实中的苹果酸和总酸含量均呈上升趋势,七成熟‘湖景蜜露’水蜜桃果实中的奎宁酸和苹果酸含量均呈急剧下降的趋势。3低温冷藏下,七、八成熟果实中糖的合成速率均低于室温贮藏的果实,九成熟果实中的果糖和葡萄糖含量均已呈降解趋势,其甜度也有一定程度的降低;七、八成熟‘湖景蜜露’果实中各游离酸和总酸含量均呈急剧下降趋势,而‘沪油018’和‘玉露’蟠桃的变化均较缓和。综合分析结果表明:不同类型桃果实的糖酸组分及其代谢存在一定的差异,‘湖景蜜露’水蜜桃风味劣变快于其他两个品种;室温和低温贮藏期间,其果糖组分及含量的变化均缓和,而其果酸组分及含量的变化却均剧烈。文中因此建议,以酸代谢为果实低温冷藏研究的主要方向,以酸降解峰点来界定果实的安全贮藏期。

Difference analysis on postharvest sugar and acid metabolism in different types of peach fruits

In order to discuss the difference of sugar and acid metabolic in different types of peach fruits and postharvest flavor deterioration mechanism, ant to provide theoretical basis for selection of appropriate maturity grades during harvest, using ‘huyou 018’, ‘Hujingmilu’ honey peach, and ‘Yulu’ flat peach as experiment materials, the rules and differences of postharvest sugar metabolic acid composition in peach were studied. The results showed that when harvesting, the sucrose contents had no significant differences between ‘Huyou018’ fruits at the seventh, eighth, ninth maturity grades, the sucrose content in ‘Hujingmilu’ honey peach at the eighth maturity grade was significantly higher than that at the seventh maturity grade, Both the sucrose content and the sorbitol content in ‘Yulu’ flat peach at the seventh maturity grade was significantly higher than that at the eighth maturity grade. The sucrose content in ‘Yulu’ flat peach (82.8-91.49 mg?g - 1) were higher than those in ‘Hujingmilu’ honey peach (77-87 mg?g - 1) and ‘Huyou018’ (55-60 mg?g - 1). The malic acid and total acid contents in both ‘Huyou018’ and ‘Hujingmilu’ honey peach at the seventh and the eighth maturity grades had no significant differences. The free acid and total acid contents in ‘Yulu’ flat peach at the seventh maturity grade was significantly higher than those at the eighth maturity grade. The malic acid contents in‘Yulu’ flat peach and ‘Huyou018’ were higher than that in ‘Hujingmilu’ honey peach. The sucrose and total sugar contents in three types of peaches had no significant changes during storage at room-temperature. The malic acid and total acid contents in ‘Yulu’ flat peach and ‘Huyou018’ at the seventh and the eighth maturity grades was in the upward trends, and the quinic acid and malic acid contents in ‘Hujingmilu’ honey peach at the seventh maturity grade were decreased sharply. During storage at low-temperature, the synthesis speeds of sugar in the fruits at the seventh and eighth maturity grades were lower than that in the fruits stored at room-temperature, the fructose and glucose contents in the fruits at the ninth maturity grades was degraded, and sweetness was decreased at a certain degree. Both the free acid and total acid contents in ‘Hujingmilu’ honey peach at the seventh and the eighth maturity grades were decreased sharply, and changes of the indexes in ‘Yulu’ flat peach and ‘Huyou018’ were not significant. The results of comprehensive analysis showed that, there were certain differences of sugar and acid metabolism during different types of peaches, and deterioration of‘Hujingmilu’ honey peach was faster than that of the other two varieties. Under room-temperature and low-temperature, there were no significant changes of fructose content, and acid content changed dramatically. It was proposed that inhibiting acid metabolism should be the main direction for the research on storage at low temperature, and The safe storage period of fruit should be defined by the acid degradation peak.