Folate, ascorbic acid, anthocyanin and colour changes in strawberry (Fragaria × annanasa) during refrigerated storage

Abstract

Colour and the composition of folate, ascorbic acid and anthocyanin of strawberry cv. Camarosa was monitored during refrigerated storage at 4 °C each day for 6 days. Folate, anthocyanin and ascorbic acid compositions were determined using High Performance Liquid Chromatography (HPLC) with UV-Vis detector. Five forms of folate: 5 methyl-tetrahydrofolate (THF) [65%], 10 formyl-folic acid (28%), 5 methylene-THF (4%), 5 formyl-THF (2%), and THF (<1%) and two forms of anthocyanins: pelargonidin 3-O-glucoside (97%) and cyanidin 3-O-rutinoside (3%) were identified in the fresh strawberries. The total folate content of the fresh strawberries determined using HPLC method was lower than that using microbiological assay. The ascorbic acid content in fresh strawberry was 57 ± 11 mg/100 g of fruit. The colour of the external skin of strawberries was measured using a Hunter colorimeter and showed fluctuation only for L* values (lightness), but a* (redness) and b* (yellowness) values remained constant during the refrigerated storage. There was no positive correlation between a* values and anthocyanin content. Strawberries should be consumed within a day or two after harvest since the reduction of these three bioactive compounds occurred even after a day of refrigerated storage.