Influence of freeze-drying parameters on the content of polyphenols and anthocyanins in strawberries

Strawberry berries are a valuable product rich in vitamins, anthocyanins, and polyphenolic compounds that have antioxidant effects on human health. However, due to the deterioration and seasonal availability, the issue of their long-term storage is highly relevant. Freeze-drying, a modern preservation method, preserves their properties during storage. Since the drying process can affect the appearance, nutrient content, and antioxidant activity of berries, the purpose of this study was to investigate the effects of freeze-drying parameters on the content of anthocyanins and polyphenols in Albion variety strawberries. The heating temperatures of the freeze-drying were 35°C, 40°C, 45°C, and 50°C, and the sublimation process times were 18, 20, and 22 hours. Optimal conditions were found: a shelf temperature of 45°C and 18 hours of drying. These conditions preserved both the strawberries' initial qualities and their high anthocyanin content, with only an 8.4% decrease. Similarly, polyphenol content decreased by 3.9%, while the strawberries maintained strong antioxidant activity.