Effect of ascorbic acid treatment on some quality parameters of frozen strawberry and raspberry fruits

Strawberry (Red Dream and Camarosa varieties) and raspberry (Nova and Killarney varieties) fruits were harvested in the middle summer in eastern part of Georgia. After harvesting average samples were immediately dipped into 0%, 1% or 2% ascorbic acid solution at 20 ± 1 °C temperature with exposure time of 2.5 min. Then, the samples were frozen at −40 °C and stored in plastic containers at −20 °C for 6 months. After 3 months storage period Total soluble solids (TSS) of strawberry and raspberry fruits decreased by 10-14% in both treated and untreated samples. TSS changes in the next three months were not statistically significant. pH values of the samples also decreased by 10-13% after 3 months regardless treatment with ascorbic acid. In the next three months pH values continued decreasing approximately with the same rate for all the samples. Due to the treatment of the fruit samples by 1% and 2% ascorbic acid, content of the last one in fruits after three months storage was increased approximately by 30% and 100% respectively and was kept practically at the same level for the next six months. In the untreated fruits of Red Dream and Camarosa of strawberry varieties during the first three months storage Total phenolic compounds (TPC) reduced by 20%. In both untreated varieties of raspberry TPC reduced by 14%. Ascorbic acid treatment increased polyphenol retaining in all frozen samples of strawberry and raspberry fruits. For Camarosa treated with 2% ascorbic acid this effect was the highest - 15%; for Red Dream the effect was the lowest - 5%. The next three months storage practically did not affect TPC in Red Dream variety of strawberry fruits neither untreated nor treated ones. In the rest varieties of berries TPC decreased maximum by 29% (Camarosa 2% treated) and minimum by 9% (Nova untreated). Antioxidant potential of the fruits was in good correlation (R2 = 0.93) with TPC for all six months of storage.