Changes in aroma volatile compounds and ethylene production during "Hujingmilu" peach (Prunus persica L.) fruit...

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.