(+)-catechin and (-)-epicatechin levels of concentrated and ready-to-drink grape juices through storage

Commercial concentrated Concord (CCJ) and Isabel (CIJ) grapes juices were stored at 4-5 degrees C while pasteurised ready-to-drink juices of the same grape cultivars (PCJ and PIJ) were kept at 20-25 degrees C under indirect light for 10 months, simulating industrial storage conditions. (+)-catechin preservation during storage ranged between 63% (PCJ) and 52% (PIJ); (-)-epicatechin retention was of 32% (CCJ) and 15% (CIJ). Total phenols retention ranged from 93% (CCJ) to 84% (PCJ) and radical scavenging activity (RSA) from 87% (PIJ) to 85% (CCJ and PCJ). Concentrated juices showed higher monomeric flavan-3-ols amounts and CCJ depicted superior phenolic contents. PIJ yielded the highest RSA during storage per phenolic unit. Process and storage impacted flavan-3-ols and not total phenolics and RSA during 10-month ageing.