DETERIORATION OF ANTHOCYANINS IN LITCHI 'KOM' FRUIT STORED UNDER DIFFERENT RELATIVE HUMIDITY LEVELS

Abstract

The effects of relative humidity (RH) on litchi fruit quality have not yet been fully defined. The aim of this study was to detail the changes in physiology, non-structural carbohydrates (NSCs), and individual anthocyanin concentrations in imported litchi fruit held at various RH levels. Litchi 'Kom' fruit, imported from Thailand, was stored at 80, 85, 90, 95 or 100% RH using different concentrations of glycerol in deionised water, at 13°C for 9 days. Fruits (n=90) were individually measured for weight loss (%), hue (h°) and lightness (L*) values. Freeze-dried aril and pericarp tissue were individually extracted and analysed for NSCs and anthocyanins, respectively. Disease, mainly caused by Penicillium spp., was observed after 6 days storage which increased disease severity. Weight loss of fruit stored at 80% RH was significantly higher than at other RH levels, whilst 90% RH-stored fruit had a significantly higher h° over 9 days. The main NSCs in aril tissue were fructose (345.73 mg g -1 dry weight (DW)), glucose (329.08 mg g -1 DW) and sucrose (31.17 mg g -1 DW). There were no significant differences in NSCs concentration according to RH treatment. Generally, fructose and glucose concentrations increased during 9 days storage, whereas sucrose levels declined. The principal anthocyanins in pericarp tissue were cyanidin 3 rutinoside (1635.52 μg g -1 DW), cyanidin 3 glucoside (19.91 μg g -1 DW) and malvidin 3 glucoside (15.03 μg g -1 DW). All anthocyanins concentrations decreased after 9 days storage except fruit stored at 100% RH when anthocyanins increased. Anthocyanin levels from 80% RH-treated fruit were significantly lower than litchi held under higher RH conditions.