D. PILAND, L. R. Howard, and C. R. Brownmiller. Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704
Blueberries are a rich source of phenolics, which have numerous purported health benefits. Unfortunately, compositional data on phenolics in different blueberry genotypes as well as the effect of growing season on phenolic composition is lacking.
Our objective was to quantify phenolic compounds in ten genotypes of blueberries over two growing seasons. We also determined the relationships between phenolic classes and antioxidant capacity.
Fully mature fruit from eight advanced breeding selections and two commercial varieties of blueberries were harvested in 2002 and 2003. Phenolics extracted with 60:37:3 (methanol, water, formic acid) were quantified by HPLC at 280, 320, 360, and 520 nm. Phenolic acids (PHA), hydroxycinnamic acids (HCA) and flavonols (FLA) were quantified as gallic acid, chlorogenic acid, and rutin equivalents, respectively. Individual anthocyanins (ACY) were quantified as delphinidin (Dpd), cyanidin (Cyd), petunidin (Ptd), peonidin (Pnd), and malvidin (Mvd) equivalents. Antioxidant capacity was measured using the oxygen radical absorbing capacity (ORAC) assay.
Levels of all phenolic compounds and ORAC values were affected by genotype, growing season, and the interaction between genotype and growing season, but genotype was the predominant factor. Total phenolic content of the genotypes over both growing seasons ranged from 150.8-675 mg/100g FW. Total ACY accounted for 59-88%, HCA (6-22%), FLA (3-16%), and PHA (1-3%) of total phenolics over both growing seasons. The distribution of individual anthocyanins in the genotypes over both growing seasons expressed as % of total ACY were: Dpd (26-40), Mvd (25-37), Cyd (11-30), Ptd (2-26) and Pnd (1-13). ORAC values ranged from 53.5-134.3 mmol TE/g FW. ORAC correlated well with total ACY (r=0.71) and total phenolics (r=0.71) over both growing seasons.
Our results demonstrate that genotype and growing season influenced phenolic content and ORAC of blueberries. Anthocyanins were the predominant phenolics, and they contributed significantly to ORAC.
Session 33F, Nutraceuticals & Functional Foods: Antioxidants and phytochemical analysis