Edible coating of blueberries enriched with New Zealand native plant leaf extracts: A novel application : A Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

Edible coatings with functional active ingredients could be a promising approach to the shelf-life of fresh blueberries, while preserving the fruit post-harvest quality, texture and nutritional content. Fruit appearance, texture and flavour are important quality traits that affect consumer choice. Kawakawa and horopito are two native plants in Aotearoa New Zealand, of significant cultural importance and have gained popularity for their traditional medicinal properties, and recently, culinary applications. This study investigated antimicrobial and physiochemical properties of blueberries coated with carboxymethylcellulose-based edible coating containing 0.2% concentration of kawakawa, horopito and kawakawa-horopito leaf extracts during a 10-day shelf-life study. The physiochemical post-harvest properties were evaluated, including fruit weight loss, colorimetric analysis, firmness, and total soluble solids concentration. The microbiological activity was analysed through counting the colony forming units for yeast and mould, Gram-negative bacteria and aerobic mesophiles. The coated blueberries significantly (p ≤ 0.05) preserved the physiochemical properties compared to uncoated blueberries, but there was no significant difference (p ≥ 0.05) among treatments of kawakawa, horopito and kawakawa-horopito leaf extracts. There was no antimicrobial activity detected by the coated bluberries. Overall, this study indicates the potential for leaf extracts from New Zealand native plants and their role in active edible coatings of fruits that are highly perishable. Future work investigating the quantification of piperine and polygodial, present in kawakawa and horopito, respectively, would provide useful insights in understanding the functionality of the leaf extracts in the edible coatings.