4-hexylresorcinol and sodium metabisulphite-based edible coatings for avocado shelf-life extension

The short shelf-life of avocados poses problems in the food supply chain, including economic losses due to food waste. This study aimed at developing a new active packaging with antioxidant potential to extend the shelf life of Hass avocados. The fruits were immersed in the solutions of 4-hexylresorcinol (4-HR, 250 and 500 mg/L) and sodium metabisulphite (SMBS, 1250 and 2500 mg/L), labelled as additive-only samples. Another set of samples was prepared by coating the fruits with sodium alginate films (10 g/L) containing the additives (alginate-coated samples). The samples were stored for 10 days at 25 ± 1 °C and 60% RH. Weight loss, total soluble solids (TSS) content, pH, firmness and bioyield point (BYP), internal and external colour and appearance, and microbial load of the samples were investigated on days 1, 5 and 10. Alginate-coated samples had lower weight loss and less increase in the total soluble solids (TSS) and pH values during storage. Firmness values remained similar for all samples from day 1 to 10, regardless of the coating used. Additive-only samples retained the bioyield point (BYP) values, whilst there was a decrease in the alginate-coated samples over 10 days. No differences were observed in the colour parameters (L*, a* and b*) between the additive-only and alginate-coated samples; the latter had a better internal and external appearance. Colour stability was slightly higher when 4-HR was added to alginate coatings than 4-HR as a standalone additive treatment. The microbial enumeration and visual appearance showed that the presence of alginate in the coating had an antimicrobial impact (no surface microbial growth). Alginate-based coatings can be a promising sustainable alternative for maintaining avocado quality during storage