Abstract
The bright red pericarp of lychee (Litchi chinensis Sonn.) fruit quickly turns brown after harvest due to peel dehydration, anthocyanin degradation, and fungal growth on the fruit surface. Lychee fruit, cv. 'Brewster' and 'Mauritius' in Florida, and 'Juckapat' in Thailand, were dipped in acidic treatments (2-2.5% citric acid, 2% ascorbic acid, 2% acetic acid, 1% isoascorbic acid), antioxidants (0.5% acetylcysteine, 0.02% hexylresorcinol), antimicrobial treatments (peroxyacetic acid [Storox], 5 or 20% ethanol) and various coatings (carrageenan, hydroxypropylcellulose [HPC], sucrose fatty acid esters [Semperfresh], pectin oligomers, and a carnauba wax emulsion), alone or in combination. Combinations of acid solutions with antioxidants gave better results than acid solutions alone. In particular, the mixture of isoascorbic acid with acetylcysteine and hexylresorcinol gave higher chroma readings with the L*a*b* color measuring system, indicating higher color intensity. This treatment also had better decay control and reduced browning. Ascorbic acid, isoascorbic acid, and acetylcysteine alone resulted in higher chroma in one experiment. Visual quality was higher for these treatments after 15 and 21 days storage at 5C, as well as for the sucrose fatty acid ester. HPC performed well on the Thai fruit, but not on the Floridian fruit. Finally, among the antimicrobial treatments, ethanol at 5% had lower browning and better decay control, and resulted in higher visual quality of 'Mauritius' lychee after 2 weeks. Future efforts will also aim at reducing pathogen pressure in the field, as well as after harvest.
