Variation in the content of total phenolics, anthocyanins and antimicrobial effects in two fractions of blueberries different cultivars

Abstract

Abstract Two fractions (pomace and juice) of blueberries of seven commercial cultivars growing in the same plantation were analysed for the content of total phenolics (TPC), total anthocyanins (TAC) and effects on food pathogens over different harvesting years. TPC in pomace did not differ significantly between years only in ‘Gretha’ and ‘Northblue’ cultivars; they accumulated stable content of phenolics. The variation in TAC in pomace across seasons was 2–5 times higher than that in TPC. The variations in TPC and TAC in juice across harvesting years were lower than in pomace, but both TPC and TAC in this fraction also differed significantly (p < 0.05) between years in all studied cultivars. The activity of juice and pomace of cultivars against food pathogens was mostly stable and did not show significant differences between harvesting years; the significant correlations were not established between antimicrobial activity of both berries fractions and TPC and TAC in all investigated cultivars. Bacteria were the most susceptible to blueberry juice with Micrococcus spp., Bacillus macerans and Escherichia coli being the most sensitive species. The evaluation of antifungal effect shows that only P. chrysogenum was sensitive to the juice of blueberries, while Aspergillus niger, Cladosporium sphaerosphermum and Penicillium chrysogenum showed resistance to the tested blueberries juice and pomace extracts.