Characterization of phenolics and antioxidant capacity in blueberries: Effects of genotype, maturation and breeding

Phenolic content and antioxidant capacity of blueberries were significantly affected by genotype and growing season. Phenolic and anthocyanin contents were more affected by genotype than growing season, whereas ORACFL values were more affected by growing season. With the exception of flavonol content, levels of all phenolic parameters analyzed increased from 2002 to 2003. There were wide variations in all phenolic parameters evaluated. Anthocyanins were the predominant phenolic compound in blueberries and they contributed significantly to ORACFL values. Blueberry maturity levels significantly affected all phenolic parameters evaluated. During ripening, there appeared to be a shift in phenolic synthesis towards anthocyanin production and a general decline in other phenolic components. Effects of maturation on phenolic content and composition varied according to genotype and total phenolic values were shown to be more indicative of ORACFL values than total anthocyanin values. It was determined that the vast majority of phenolics, anthocyanins and antioxidant capacity were present in the blueberry skin. Whole fruit total phenolic content was approximately 2.5 times higher than in the pulp/seeds and skin phenolic values were 10-15 times higher than pulp/seeds values. Parents and seedlings examined for phenolic content and antioxidant capacity exhibited variation due to genetic expression. Most seedlings produced lower phenolic and antioxidant capacity values than their parents. However there was one seedling from each group with substantially higher values than its parents and other seedlings. An inverse relationship between phenolic values and average berry weight was quite evident. The effect of harvest date on berry weight, phenolic parameters and antioxidant capacity was genotype dependent. Breeding selection phenolic and antioxidant values were higher than those for commercial genotypes. The breeding selections maintained similar anthocyanin levels, phenolic levels, and antioxidant capacities regardless of harvest date or variations in average berry weight. The commercial cultivars contained highest anthocyanin levels at peak berry weight and showed significant changes in ORACFL values across harvest dates. Information from this research may assist plant breeders and scientists in developing commercially acceptable blueberries and blueberry products with desirable phenolic profiles and antioxidant capacities.