Separation of Absorption Coefficients from Ripeness-related Fruit Pigments in Stored Mango
2010
Pflanz, Michael | Mudau, Nixwell | Zude, Manuela
Breakdown and synthesis rates of green and yellow fruit pigments are well correlated with ripeness of tropical fruits and can be analysed precisely and cost-efficiently by spectrophotometry. In the present study postharvest observations of mango fruits (Mangifera indica L. ‘Kent') and their varying maturity and quality related contents of chlorophylls, carotenoids and xanthophylls have been used to evaluate a new method for analysing spectral data by an iterative multiple regression algorithm (iMLR). The main objective was to establish this method as a laboratory application analysing fruit extracts in organic solvents and, furthermore, for non-destructive quality tests on fruit and vegetables. It is shown that varying contents of chlorophyll a and b as well as beta-carotene and violaxanthin could be calculated in a nonpolar solution of mango pigments using iMLR. As a mixture of mango pigments were determined using sets of linear equations, the error was higher compared to results of iMLR. The content of violaxanthin in overripe fruit exocarp was computed with 18.04 µg/g DW and thus significant higher than the content in unripe fruit exocarp (8.63 µg/g DW). The content of ß-carotene did not change during the time of storage. For analysing non-destructively recorded fruit spectra iMLR is applicable within limits. In diffusive tissue, corrections regarding the varying optical sample properties are needed. The measuring uncertainty was low for chorophyll, but high for single carotenoids.
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