Nectarine Maturation, Fatty Acid Composition and Volatile Substances of Peaches and Nectarines
|Keywords||Peach nectarine fruit maturation color fatty acids volatiles e-nose|
The variations of fatty acids and volatiles in fruit of39peach and nectarine varieties were investigated, and the physical and chemical changes during nectarine (cv.Hu018) maturation were investigated in this paper. The main results were as follows:Firmness values of nectarine ascended from4to6WAB, and descended from6WAB until ripening. Anthocyanins in peel ascended from8WAB to12WAB. Anthocyanins of red and green peel during fruit maturation were identified as abundant cyanidin3-glucoside and tiny cyanidin3-rutinoside by HPLC. Anthocyanins contents were positively correlated with data of PAL, POD, A*, MDA and O2·-, and inversely correlated with L*and B*values. Red and green peel during maturation could be separated by HCA of the tested data. Values of A*, anthocyanin, O2·-, MDA, PAL, PPO and POD in red peel were higher than those in green peel, while values of L*, B*and chroma in red peel were lower than those in green peel through fruit maturation.A FOX4000electronic nose was used to distinguish fruit volatile substances, the response values of LY2/LG, LY2/AA, LY2/GH, LY2/gCT1and LY2/gCT sensors were negative, while those of the other13sensors were positive. Discriminant factor analysis (DFA) and statistical quality control (SQC) provided better separation information than principal component analysis (PCA).The contents of palmitic (16:0), stearic (18:0), monounsaturated (18:1), linoleic (18:2), linolenic (18:3) and arachidic (20:0) acids were identified in pulp of39peach and nectarine varieties in which palmitic (16:0) and linoleic (18:2) acids were abundant. Concentration variations of16:0,18:0,20:0and18:2fatty acids were lower than those of18:1and18:3fatty acids in pulp of the tested varieties. Positive correlations were showed between the data of16:0and both18:1and18:3fatty acids. HCA, PCA and C18:1versus C18:3fatty acids plots of the tested varieties based on fatty acid data demonstrated low genetic diversity.An electronic nose was applied to evaluate pulp volatiles of39peach and nectarine varieties in this study. Based on pulp volatiles measured by the e-nose, eleven cultivars harvested in June,12cultivars harvested in July and16cultivars harvested in both August and September could be clustered into three distinguished groups in the DFA plots. Sixteen cultivars of low (<12%) TSS concentration could be dis-tinguished clearly from 13cultivars of high (>16%) one, and ten cultivars of medium (12%<TSS>16%) one were overlapped with cultivars of low (<12%) or high (>16%) one in the DFA plots. Fourteen cultivars of low (<35) TSS/TA ratio could be distinguished clearly from13cultivars of high (>45) one, and12cultivars of medium (35<TSS/TA<45) one were overlapped with cultivars of low (<35) or high (>45) one in the DFA plots.According to the concentrations of16:0,18:0,18:1(n-9),18:1(n-7),18:1,18:2,18:3,20:0, saturated, unsaturated, polyunsaturated and total fatty acids in pulp of39cultivars, three individual cultivar groups were divided based on the individual low, medium and high fatty acid concentration classifacations. Based on pulp volatiles measured by the e-nose, cultivars of low (<5μM100g-1FW)18:1(n-7) fatty acid could be distinguished from cultivars of high (>8μM100g-1FW) one, cultivars of low(<10μM100g-1FW)18:1fatty acid could be distinguished from cultivars of high (>15μM100g-1FW) one in the DFA plot of39cultivars.