Effects of Bagging on Volatiles and Polyphenols in "Wanmi" Peaches during Endocarp Hardening and Final Fruit Rapid Growth Stages

Fruits of the late-ripening peach cultivar "Wanmi" were bagged at the early period of fruit endocarp hardening, and the bags were removed 1 wk before maturity harvest. The effects of bagging on volatile compounds and polyphenols were studied. Total volatiles and the sum of C-6 compounds, esters from bagged fruits were significantly lower than from nonbagged fruits from the beginning of the final rapid fruit growth stage to maturity. As the most dominant compounds of C-6 compounds and esters, the lower contents of hexanal, trans-2-hexenal, hexyl acetate, cis-3-hexenyl acetate, and trans-2-hexenyl acetate attributed to the lower content of C-6 compounds and esters in bagged fruit. gamma-Hexalactone and delta-decalactone were produced earlier in bagged fruits than in nonbagged ones, suggesting that bagging accelerates fruit maturity. Level of. gamma-decalactone in bagged fruits was significantly lower than in nonbagged fruits at 159 days after full blossom (DAFB), so did delta-decalactone at 166 DAFB. Bagging did not affect chlorogenic acid and catechol contents of either fruit peel or flesh, nor did it affect contents of keracyanin or quercetin-3-rutinoside in fruit flesh during fruit development. However, keracyanin and quercetin-3-rutinoside levels were significantly reduced in bagged fruit peels before ripening compared to nonbagged fruit peels. Considering the large changes in volatiles and polyphenols, the key stage for "Wanmi" fruit maturity was between 126 DAFB and 147 DAFB, about 1 mo ahead of maturity.