Impact of edible coatings on chemical content, microbiological contamination and physical properties of blueberries

Abstract

The research was carried out at Aleksandras Stulginskis University the Faculty of Agronomy in the Institute of Agricultural and Food Science in 2017-2018. The objective of this study was to determine the possibilities to prolong shelf-life and avoid microbiological contamination of blueberries using chitosan based edible coatings with peppermint essential oil. Blueberries of cv. 'Bluecrop' and 'Patriot' were immersed in prepared chitosan edible coating for 15 min, let to dry in the air for 4 hours and stored at 4 °C temperature for 27 days. Standard methods were used to determine the amount of dry matter, soluble solids, pH, titratable acidity, texture and colour. There were counted colonies forming units of micromycetes by dilution plating (a surface-spread method) in blueberries after the storage. The amount of soluble solids at the end of the storage increases and the highest increase was observed in non - treated with chitosan coating blueberries. There was no statistically significant difference in the changes of berries pH during the storage. Despite that edible coatings provide a barrier to oxygen, reduce the metabolism and oxidation reaction rates, the amount of vitamin C decreased independently of the cultivar and the treatment. Appearance and firmness are the most critical quality attributes influencing consumer choice of products. The value of blueberries in the market depends on the colour of a product. The combination of chitosan and peppermint essential oil lead to more intensive colour retention to dark than in untreated and chitosan coated berries. The least number of colony forming units of fungi was detected in both cultivars of blueberries covered with chitosan coating with essential oil of peppermint. [...]