Accumulation of all-trans-beta-carotene and its 9-cis and 13-cis stereoisomers during postharvest ripening of nine Thai mango cultivars

Accumulation of beta-carotene during postharvest ripening of nine Thai mango cultivars was assessed after verifying extraction and high-performance liquid chromatographic quantification of the beta-carotene stereoisomers for this sample matrix. No relevant trans-cis isomerization was induced by the analytical procedure. The vitamin A potential of mangoes was evaluated at different ripening stages unequivocally defined by a ripening index (RPIWB). Being rather stable throughout postharvest ripening, the cultivar-specific proportion of cis-beta-carotene isomers ranged from 14 to 40% of the total beta-carotene content. Subjected to the same postharvest ripening conditions, only the cultivars Kaew, Maha Chanok, Chok Anan, and Nam Dokmai #4 developed a bright yellow-orange mesocarp coloration at their fully ripe stage (RPIWB = 1.5-1.8, sugar-acid ratio approximately 50), resulting in total beta-carotene contents of 6544-11249 microg/100 g mesocarp dry weight (DW) and vitamin A values of 892-1573 retinol equivalents (RE)/100 g DW. Contrarily, poor-colored cultivars Mon Duen Gao, Rad, Kiew Sawoei, Okrong Kiew, and Okrong Thong reached total beta-carotene contents of 1019-2195 microg/100 g DW and vitamin A values of 136-298 RE/100 g DW at comparable sugar-acid ratios. Exponential development of mesocarp color (hue angle, H degrees ) and all-trans-beta-carotene levels, respectively, with RPIWB was described for each cultivar, allowing good prediction of mesocarp color and vitamin A value at consumption ripeness.