Determination of Antioxidant Activity and Total Anthocyanin Content of Frozen and Thawed Strawberries under Different Conditions

Strawberries are among the summer fruits popularly consumed by consumers. High antioxidant activity, anticancer, anti-inflammatory effect and high bioactive substance content are also beneficial to human health. However, their shelf life is short due to their high water content and active metabolismThey can be kept frozen and processed in order to be consumable in all seasons. During freezing, when the water in the contents turns into ice crystals, the expansion occurs. For this reason, frozen and thawed fruit is generally softer than fresh fruit. These effects can vary with different types of freezing condition. In addition, freezing and thawing conditions can affect the stability of phenolic compounds, anthocyanins and antioxidant activity. In this study, fresh strawberries were frozen at different temperatures; -18 °C, -86 °C, and individually quick frozen (IQF) as freezing methods. Frozen strawberries were thawed at 24 °C at room condition, +4 °C in the refrigerator and microwave oven with thawing mode. Total phenolic compounds, total flavonoid and total anthocyanins content, and total antioxidant activity were performed to examine the effect of freezing and thawing on biocompatibility. According to the results, the total phenolic compounds in the range of 0.77-2.76 mg gallic acid equivalent/g, flavonoid content 0.32-0.90 mg catechin equivalent/g, total anthocyanin content 0.02-0.16 mg/g and total antioxidant capacity 49.06 and 55.64% were found in strawberries. According to these results, it was determined that the loss of bioactive components was minimized by frozen with IQF and thawing in the microwave oven. In addition, the shortness of the thawing time in this process provides an extra advantage.