Stability of ellagitannins in unclarified juices and purees of raspberry and blackberry fruit during one-year storage period

The paper presents the stability of ellagitannins (ETs), ellagic acid and conjugates (EAC) in unclarified juices and purees obtained from raspberries and blackberries. The innovation was to compare 2 different products with a variable composition in quantity and quality ETs coming from two different fruits. The preserves were stored for 12 months at three temperatures: −20, 4 and 20 °C (±2 °C). Analysis was performed every 3 months, using HPLC-DAD and LC-MS. In the presented research the degree of degradation of the overall of ETs + EAC was determined and the transformation of individual ETs was described. The ratio of monomeric, dimeric, trimeric and tetrameric compounds with respect to the sum of ETs and EAC and changes in their concentration over time were also determined. Additionally, the influence of time and temperature on the stability of ETs + EAC of different molecular weights was investigated using the Spearman correlation. Moreover, the stability of the oligomers characteristic of raspberries and blackberries was determined.

Purees were characterized by 5–6 times higher content of ETs + EAC, however, these compounds were decreased much faster compared to juices. In purees, the decrease of individual high-molecular ETs was much faster than in juices and was dependent on temperature and storage time. A difference in the decrease rate of the oligomers lambertianin C (LC) and sanguiin H-6 (SH-6) was observed. The highest degree of decrease was recorded at the highest temperature; after a year, in blackberry puree, 36% of SH-6 and over 60% of LC were decrease, in raspberry puree - 29% SH-6 and 50% LC.