挥发性香气物质和乙烯生产在"湖景蜜露"桃果实发育过程中的变化

以"湖景蜜露"水蜜桃(Prunus persica L.)为试材,检测了果实从未成熟到成熟发育过程中乙烯生成、呼吸速率及挥发性香气性物质的变化;同时对果实大小、果皮色泽、果肉硬度、可溶性固形物、可滴定酸进行了测定;对与果实乙烯产生密切相关的1-氨基环丙烷-1-羧酸(ACC)含量、ACC合成酶活性、ACC氧化酶活性也进行了测定.结果表明,随果实成熟度的增加,果实大小、果皮L*值、可溶性固形物含量增加,而果实硬度、果皮h°值、可滴定酸含量减少.在未成熟的果实中,C6的醛类(反式-2-己烯醛)和醇类(顺式-3-己烯醇)是主要的成分;乙烯生成量很低;呼吸速率较高.到跃变阶段C6～C12的内酯类物质明显增加,尤其是γ和δ-内酯类成为果实主要的香气挥发性物质.推测果实乙烯、呼吸作用等基本的生理变化可能调节着内酯类物质的生成.在乙烯跃变上升时果肉中ACC氧化酶的活性下降,ACC含量和ACC合成酶活力的变化与乙烯生成量变化的趋势一致.根据以上结果可以认为桃果实主要的香气挥发性物质的形成与乙烯、呼吸跃变的开始密切相关.香气物质形成速率动态变化可能是桃果实发育过程中成熟度的另一个生理学指标.

Changes in Aroma Volatile Compounds and Ethylene Production During "Hujingmilu" Peach (Prunus persica L.) Fruit Development

Changes in ethylene production rate, respiration rate, and aroma volatile composition was determined from the immature to mature stage in "Hujingmilu" peach (Prunus presica) fruit. Flesh firmness, fruit size, ground color of skin, and total soluble solids (TSS), titratable acidity (TA) in juice were analyzed, and ACC, ACC synthase and ACC oxidase activities were measured. With the increase of fruit maturity, fruit size, L* value, and TSS and major reducing sugar contents increased, whereas fruit firmness, skin hue angle (h degrees ), and juice TA and organic acid contents decreased. In immature fruits, a C(6)-aldehydes (trans-2-hexenal) and C(6)-alcohols (cis-3-hexenol) were the major components, corresponding to the low ethylene production and high respiration rates. With increasing of fruit maturity, the C(6)-C(12) lactonic compounds, particularly gamma- and delta-lactones became the dominant volatile constituents, which increased significantly at the climacteric stage. These facts suggest that ethylene production may be involved in the regulation of lactones production in maturing peach fruit. The activity of ACC synthase in the mesocarp declined during the climacteric rise of ethylene. ACC level and ACC oxidase activity in mesocarp were consistent with the onset of ethylene production in fruit. Major aroma volatiles are thought to form in conjunction with the initiation of climacteric rises in respiration and ethylene production. Detection of changes in aroma volatile compound synthesis rate in peach may be useful as index of maturity reflecting the current physiological stage of peach fruit development.