Assessment of volatile and non-volatile organic compounds in the liquid endosperm of young 'Nam Hom' coconut (Cocos nucifera L.) at two stages of maturity

摘要

Young coconut (Cocos nucifera L.) fruit collected 6 8 months after anthesis (MAA) contain a high volume of water [20% (w/w)] and can provide a refreshing drink. The present study investigated volatile organic compounds (VOCs), as aroma components, and physico-chemical changes in the liquid endosperm of young 'Nam Hom' coconut at two stages of maturity: the one-layer stage (6 MAA) and the two-layer stage (7.0 - 7.5 MAA) of the flesh. The liquid endosperm of coconut fruit becomes sweeter and more turbid late during maturation. Lauric acid (C-12:0) and myristic acid (C-14:0) were the main free fatty acids in the liquid endosperm of coconut. Short-chain fatty acid (C-10 - C-12) concentrations increased slightly, and longer-chain fatty acid (C-14 - C-18) concentrations declined when fruit matured from the one- to the two-layer stage of flesh. Solvent extractions showed a 1.4-fold increase in the total concentration of VOCs in the liquid endosperm during fruit development. This was related to a major increase in squalene and sterols, to 21.7% (w/w) of the total VOC and non-volatile organic compounds, whereas the concentrations of terpenes and esters remained stable. Although a series of alkanes existed in the liquid endosperm of coconut, the main aroma components were 2-methyl-1-butyl acetate and terpenes such as D-limonene, a-pinene, and 3-carene. We conclude that, when coconut fruit developed from the one- to the two-layered flesh stage, the liquid endosperm not only became sweeter and contained higher concentrations of aroma volatile and non-volatile components, but also became oily and less translucent.