The Effect of Freezing as a Storage Method on Anthocyanin Concentration in Blueberries

Blueberries are rich in a water-soluble class of pigments known as anthocyanins which are known antioxidants. Antioxidants help prevent many diseases by stabilizing free radicals, but are prone to losses in food during storage. The goal of this study was to test the effect of freezing as a storage method on anthocyanin concentration and antioxidant activity over time. Blueberries from Canada and Argentina were frozen for up to 5 months and periodically tested for anthocyanin concentration and antioxidant activity. Anthocyanins were extracted using a mixture of methanol, acetic acid, and water, and evaporation under vacuum. They were separated using column chromatography. The concentration was determined by absorbance at 538 nm and the Beer-Lambert law, and antioxidant activity was measured using absorbance at 515 nm and DPPH free radical. Anthocyanin concentration ranged from 3.32 ± 0.40 mg/g in fresh berries to 8.89 ± 3.56 mg/g in berries frozen for 133 days. Concentration directly correlated with the antioxidant activity of anthocyanin on DPPH free radical in that 55.37 and 39.07% DPPH remained after 2 hours of antioxidant/DPPH reaction for the fresh and 133 day samples, respectively. Country of origin did not appear to impact anthocyanin concentration but did play a role in how the anthocyanin reacted with the free radical. Freezing appears to be an acceptable form of storing blueberries for up to 66 days (about 2 months) depending on ice crystal formation.https://openprairie.sdstate.edu/honors_isp/1006/thumbnail.jp