Evaluation of the effects of various storage conditions on bioactive compounds in berries.
Background: Many diseases are strongly associated with oxidative stress caused by free radicals. Naturally occurring antioxidant consumption is strongly encouraged. The aim of this study was to evaluate samples of blueberries and raspberries and determine the optimum storage condition to retain their high bioactive compound concentrations. The storage conditions evaluated consisted of fresh, frozen and overripe groups additionally blended groups of each of these storage condition. Methods: The total antioxidant capacity was measured using the ferric reducing antioxidant power (FRAP) assay. The total phenolic concentration was estimated using the Folin-Ciocalteu colorimetric method. Analysis of chlorophyll A, B and total carotenoid concentrations was carried out. Total anthocyanin content was determined and as its stability is pH dependant, pH was tested for each group. Results: Among the fruits tested, raspberries presented with the highest total antioxidant value under the storage condition of frozen (4.421mM FSE/100g). This represented a 3-fold increase in comparison to the blueberries in the same condition (1.511mM FSE/100g). Total phenolic concentration was expressed on a fresh weight based sample on Gallic acid equivalent (GAE/100g). Significant differences were seen in many groups when comparing the blueberries and raspberries with t-tests analysis between the storage conditions; fresh (p=0.02), frozen B (p=0.002), overripe (p=0.003) and overripe B (p=0.03). Blueberry content of anthocyanins show fluctuations between the storage conditions from 0.54 mg C3G/g to 0.93 mg C3G/g. However, when a T-test analysis was performed no statical significance was exhibited between the blueberry conditions although a visible elevation was seen in the blended groups compared to the unblended. The pH evaluation of the fruits under these conditions resulted in the raspberries presenting with more acidic results (average pH of 3.12) in comparison to blueberries. Conclusion: Although significant differences were calculated between the fruits there is no obvious storage condition which does not alter all the BAC. Although the blending of fruits to create a smoothie consistency does appear to be of greater benefit in exposing the BAC. Keywords: antioxidants, phenolic acid, storage conditions, raspberries, blueberries, bioactive compounds.