Postharvest Biopreservation of Fresh Blueberries by Propolis-Containing Edible Coatings Under Refrigerated Conditions

Abstract

Propolis is a complex honey bee product known for its antioxidant potential and antimicrobial activity, widely used as a food biopreservative and food additive. The object of the current research was to investigate the effects of carboxymethyl cellulose (CMC) edible coatings applied alone and in combination with a propolis extract on the quality parameters and storage life of fresh blueberries during refrigerated storage for 20 days. For this purpose, three experimental groups were prepared: blueberries without coating (control group), blueberries with 1% CMC coatings and blueberries with 1% CMC coatings + 1% propolis extract (CMC+P). During the storage, the physicochemical and microbiological parameters of the experimental groups were evaluated. The use of CMC and CMC+P coatings reduced the weight loss by 1.13% and 1.67% in comparison with the control group on the 20-th day of storage. A significant decrease in decay percentage was found, which was in the great extent in the CMC+P coated fruit compared to the CMC coatings and the control fruit. The CMC and CMC+P edible coatings did not affect the TSS levels, the decreasing TA and increasing pH values. The application of CMC and CMC+P coatings did not cause a protective effect on the lowering values of total phenolic and anthocyanin contents in both treatments, but exhibited a positive influence on the antioxidant activity in the coated blueberries. During the entire storage period, propolis containing edible coatings (CMC+P) reduced the bacterial, yeasts and fungal counts, visibly expressed by a reduction in decay incidence in comparison with the uncoated and CMC-treated fruit. Therefore, the application of propolis in the composition of edible coatings can be considered as an effective approach for improving the postharvest quality and prolonging the storage life of fresh blueberries.