LYCHEE PERICARP BROWNING CAUSED BY HEAT INJURY

Mature lychee (Litchi chinennis Sonn.) fruit were heat-treated at 60C for 10 min to study heat-induced pericarp browning. Polyphenol oxidase (EC 1.10.3.2) activity of the pericarp increased immediately, corresp onding with rapid anthocyanin degradation. Tissue browning was observe d 2 min after heating, with pigmentation distributed uniformly through out the pericarp. The distribution of brown pigments was different tha n the highly localized browning observed under ambient desiccation. Al though both ambient and heat-induced pericarp browning are visually si milar, the anatomical distribution of brown pigmentation is quite dist inct. The distribution of brown pigmentation was not consistent with a nthocyanin localization. Following ambient desiccation, the mesocarp b ecame colorless even though this represented the greatest concentratio n of pigment. Browning caused by heating may result from nonselective degradation of a range of compounds, including anthocyanin.