Anthocyanins from mulberry (Morus rubra) fruits as potential natural colour additives in yoghurt

Abstract

Colouring potential of anthocyanins from whole fruit juice of mulberry (Morus rubra) was studied in yoghurt. Whole fruit juice from M. rubra rich in non-acylated anthocyanins was incorporated into plain yoghurt (100 g) at increasing concentration levels of the juice; 10, 20, 25, 30, 40 and 50 mg cyanidin-3-glucopyranoside equivalents (cy-3-glu eqv) and stored under refrigerated condition (< 8°C) for two weeks. Colour properties, pigment and colour stability and degradation kinetics were studied using a UV-Vis spectrophotometer (UV-1700 CE Shimadzu, Japan).Yoghurt coloured with mulberry anthocyanins between 25 to 40 mg cy-3-glu eqv concentration levels of anthocyanins produced a colour which was very much comparable to commercial brand strawberry yoghurt coloured with 20 mg FD & C red No. 3 in 100 g of yoghurt. Pigment and colour stabilities of the anthocyanins increased with increasing concentration of anthocyanins added to yoghurt. The tendency to polymerise decreased with increasing concentration of the pigments added to yoghurt. The degradation of the anthocyanins was fitted to first-order reaction kinetics. Moderate concentration levels (25 to 40 mg cy-3-glu eqv in 100 g of yoghurt) of mulberry anthocyanins were found to be ideal to colour yoghurt. Key words: Mulberries, anthocyanins, cyanidin-3-glucopyranoside (cy-3-glu), natural colourants, colour stability, yoghurt.