Short Period Storage Impact on Bioactive Constituents from Bilberries and Blueberries

Objectives: The aim of this study was to assess storage effects on anthocyanin and total polyphenol content in different bilberry and blueberry extracts and to evaluate the antioxidant and antibacterial activity of these extracts.
Materials and methods: Total phenolic content, total monomeric anthocyanin content and antioxidant activity were determined in the first month and after three months storage of berries at either -20 °C or -50 °C. Two different solvents were used (methanol and 50% ethanol). Antibacterial activity was determined for the 3 months stored fruits using a microdilution method and was expressed as the minimum inhibitory concentration.
Results: There were significant differences between the concentration in the first month and after three months storage in both types of fruit extracts. Regarding the extracting solvent, we noticed that total phenols were better extracted with 50% ethanol, while the total monomeric anthocyanin content was higher in the methanolic extracts. No significant or slightly significant differences were observed between the fruits stored at -20 °C or -50 °C. Ethanolic extracts showed the highest scavenging activity. Good antibacterial activity was observed on gram-positive bacteria.
Conclusions: Storage conditions are an important factor that can influence chemical composition of fruits. Although freezing is a good option for preservation, our study showed a high decrease in the concentration of total phenols and anthocyanins after only three months. The fruits have shown a high antioxidant activity and a good antibacterial effect. Further studies are needed for better understanding the changes that can appear during the storage.