Postharvest antimicrobial treatments with organic acids to improve the shelf life of fresh blueberries

Fresh highbush blueberries (Vaccinium corymbosum L.) are one of the most popular soft fruits characterized by attractive sensorial attributes and high antioxidant potential. They are highly perishable as they are susceptible to various microbial infections, both pre- and postharvest. The present research was conducted to investigate the effects of postharvest treatments with citric (2%), benzoic (0.2%) and sorbic (0.2%) acids on physicochemical, biochemical and microbiological evolution of fresh blueberries under cold storage conditions. Samples were evaluated initially and at 7-day interval for dry matter, total soluble solids, titratable acidity, total phenolic content, total flavonoid content, antioxidant activity and surface microbial load for six weeks storage time. Chemical treatments significantly reduced the microbial growth on the fruit surface throughout the storage period as compared to the control samples, but they caused a significant increase in moisture loss (sorbic acid > benzoic acid > citric acid > water), probably due to the partial damage of the natural cuticular wax layer covering the fruit. Antimicrobial effects of chemical treatments were more noticeable than their biochemical effects. Total phenolic, total flavonoid content and antioxidant activity showed similar variation pattern during storage in treated and control samples. However, at the end of the storage period, antioxidant activity was significantly higher in samples treated with citric acid and benzoic acid as compared with control samples.