Stability of ellagitannins in processing products of selected Fragaria fruit during 12 months of storage

The aim of the study was to determine the stability of ellagitannins (ETs), ellagic acid, and conjugates (EAC) in unclarified juices and purees produced from two selected berries of the Rosaceae family, genus Fragaria. A total of 16 ellagitannins have been identified in the products. Stability studies were carried out for 1 year in three temperature variants: -20, 4, and 20°C (±2°C). The quantitative and qualitative determinations of ETs + EAC were performed every 3 months using the HPLC-DAD and LC-MS techniques. An important element of the research was also the determination of ETs transformations that occur in juices and purees during storage. The stability of ETs + EAC is primarily determined by the temperature and storage time as well as the matrix. After 1 year of storage at -20°C, the sum of ETs and EAC did not decrease in strawberry juice. On the other hand, the decrease was shown at the level of 30 and 20% at temperatures of 4 and 20°C, respectively. In strawberry purees, a decrease in ETs + EAC of 15-28% was recorded during storage in all three temperature variants. After 1 year, in wild strawberry juice, 20-50% of ellagitannin decreased, in puree the decrease in ETs + EAC concentration was 40-54%. With increasing temperature, the percentage of compounds with lower molecular weight increased-from 10 to 14% at temperatures of 4 and 20°C, respectively. At the temperature of -20°C, the proportion of low- and high-molecular-weight compounds remained stable in each case.