Ellagitannin and Anthocyanin Retention in Osmotically Dehydrated Blackberries

Abstract

The objective of the work was to examine changes in the content of ellagitannins and anthocyanins, which are the main polyphenolic fractions of blackberries, during osmotic dehydration of the fruit in 50 – 65°Bx sucrose solutions. Frozen blackberries were found to be readily dehydrated under mild temperature conditions (30°C), with dry matter content more than doubling after 1 h, and reaching 48% after 3 h in 65°Bx solution. Total ellagitannin retention after 1 h of processing amounted to at least 80%, while after 3 h it ranged from 63.6% to 82.4%. The concentrations of the two main ellagitannins, lambertianin C (a trimer) and sanguiin H-6 (a dimer), revealed similar patterns of variation. The greatest losses, reaching up to 50% after 1 h of dehydration, were recorded for ellagic acid. After the same treatment time, the decrease in anthocyanin concentration was approx. 30 – 40%. The loss of polyphenolic compounds from fruit was attributable to their migration to the syrup. After 3 h of osmotic dehydration, ellagitannin concentration in the syrup amounted to 13.6 – 22.1 mg/100 mL, and that of anthocyanins was 6.7 – 11.2 mg/100 mL.