Effects of Juice Matrix and Pasteurization on Stability of Black Currant Anthocyanins during Storage

The effects of juice matrix and pasteurization on the stability of total phenols and especially total and individual anthocyanins were examined in black currant (BC) juice and mixtures with apple, persimmon, and peach juices at 4 degrees C and 20 degrees C. Total phenol content decreased in all juices at both temperatures but there was a trend to lower levels in unpasteurized over pasteurized juices. Differences in the decline of total anthocyanins between pasteurized and unpasteurized juices varied according to the juice type and the storage temperature. At 4 degrees C storage, anthocyanins declined in all juices according to pseudo 1st-order kinetics and there were only small differences in the rates between pasteurized and unpasteurized juices. However, at 20 degrees C, although pasteurized and unpasteurized BC juices and pasteurized mixed juices followed pseudo 1st-order kinetics, there was a different pattern in unpasteurized mixed juices; a rapid initial decline was followed by a slowing down. The effect of the added juice on anthocyanin decline was also different at either temperature. At 4 degrees C, the anthocyanins decreased faster in mixed juices than BC juice alone, but at 20 degrees C, at least in pasteurized mixed juices, the decline was similar or even slower than in BC juice; there were only small differences among the 3 mixed juices. At 20 degrees C, in pasteurized and unpasteurized BC juices, the rate of decrease was essentially the same for all 4 individual anthocyanins but in the mixed juices the 2 glucosides decreased significantly faster than the 2 rutinosides. Practical Application In juices containing mixtures of black currant juice (containing healthy anthocyanins) with other juices (apple, persimmon or peach), substantial losses of anthocyanins occurred during storage in the fridge so that after 4 wk 1/3rd was lost, and at room temperature half the anthocyanins were lost after 1 wk. Pasteurization caused about 1/5th of the anthocyanins to disappear. During storage in the fridge, anthocyanins degraded at similar rates in pasteurized and unpasteurized juices but at room temperature, there was a rapid fall in anthocyanins in unpasteurized juices after 1 wk so that levels were comparable to those in pasteurized juices.