The copolymerization of ε -caprolactone (CL) with its structural isomer , δ -hexalactone (HL), or trimethylene carbonate (TMC) catalysed by diphenyl phosphate was investigated. Copolymers with molar fraction of CL units ranging from 54% to 95% were obtained. Molecular characterization exhibited random distribution of the two monomeric units (CL/HL or CL/TMC), owing to the extensive occurrence of transesterification scrambling reactions at high temperature. Compared with poly( ε -caprolactone) (PCL), the copolymers showed reduced crystallinity and enhanced enzymatic degradability as revealed by the analysis with differential scanning calorimetry and quartz crystal microbalance with dissipation, respectively. Interestingly, the incorporation of HL units showed a more profound impact than TMC. It is therefore considered that organocatalytic copolymerization with HL, a bio-renewable lactone, can serve as an effective method to regulate the properties of PCL.
To deepen the understanding of peach aroma, we investigated the changes of volatile organic compound (VOC) profiles during fruit development in three fresh peach cultivars: ‘Jiucui (JC)’, ‘Zhongyoupan No. 9 (ZYP9)’ and ‘Zhongyou No. 8 (ZY8)’. The classes and contents of VOCs changed significantly during fruit ripening. The representative VOC changes were categorized into three developmental stages, with the lowest volatile content observed during the middle stage. At maturity, ester-related volatiles increased significantly, dominating the VOC profiles and accounting for 78 %, 82 % and 88 % in JC, ZYP9 and ZY8, respectively, while alcohols decreased dramatically. Multivariate analysis identified 23, 21 and 20 potential volatile markers in JC, ZYP9 and ZY8, respectively, with 9 shared markers distinguishing the different developmental stages. Odor activity values (OAVs) and olfactometry analysis highlighted 36, 29, and 26 aroma-active compounds (OAV > 1) across the cultivars, with key contributors to the mature peach aroma including hexyl acetate (OAV 860–2896), ( E )-2-hexenyl acetate, ( Z )-3-hexenyl acetate, ( E )-3-hexenyl acetate, linalool, and γ -decalactone. The fruity aroma intensified as ripening progressed, with ZY8, a cultivar with a longer maturation cycle, exhibiting the highest odor intensity. This study offers insights into the dynamic changes in VOC profiles during peach development, highlighting key aroma-active compounds and their stage-specific variations.
The changes in volatiles during postharvest storage of three peach cultivars (JC, ZYP9 and ZY8) were tracked under two temperature conditions (25 °C and 4 °C). Overall volatile content significantly decreased during storage over time, specifically with a marked decrease in ester levels, while the relative proportions of alcohols, aldehydes, and ketones increased during cold storage. These changes in volatile composition revealed three distinct storage stages across the cultivars, with the middle stage marking a critical turning point in volatile flavor quality. Among the cultivars, ZYP9 and ZY8 exhibited better adaptability to cold storage than JC. The reduction in key esters, coupled with the increase in alcohols and aldehydes, led to altered aroma profiles and the development of off-flavors in cold-stored peaches. Overall, this study provides valuable insights into the dynamic changes in flavor volatiles during postharvest storage and contribute to a deeper understanding of aroma quality in stored peaches.
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