Postharvest characteristics and handling of litchi fruit — an overview

Abstract

Litchi (Litchi chinensis Sonn.) is a tropical to subtropical crop that originated in South-East Asia. Litchi fruit are prized on the world market for their flavour, semi-translucent white aril and attractive red skin. Litchi is now grown commercially in many countries and production in Australia, China, Israel, South Africa and Thailand has expanded markedly in recent years. Increased production has made significant contributions to economic development in these countries, especially those in South-East Asia. Non-climacteric litchi fruit are harvested at their visual and organoleptic optimum. They are highly perishable and, consequently, have a short life that limits marketability and potential expansion of demand. Pericarp browning and pathological decay are common and important defects of harvested litchi fruit. Postharvest technologies have been developed to reduce these defects. These technologies involve cooling and heating the fruit, use of various packages and packaging materials and the application of fungicides and other chemicals. Through the use of fungicides and refrigeration, litchi fruit have a storage life of about 30 days. However, when they are removed from storage, their shelf life at ambient temperature is very short due to pericarp browning and fruit rotting. Low temperature acclimation or use of chitsoan as a coating can extend the shelf life. Sulfur dioxide fumigation effectively reduces pericarp browning, but approval from Europe, Australia and Japan for this chemical is likely to be withdrawn due to concerns over sulfur residues in fumigated fruit. Thus, sulfur-free postharvest treatments that maintain fruit skin colour are increasingly important. Alternatives to SO2 fumigation for control of pericarp browning and fruit rotting are pre-storage pathogen management, anoxia treatment, and dipping in 2% hydrogen chloride solution for 6−8 min following storage at 0°C. Insect disinfestation has become increasingly important for the expansion of export markets because of quarantine issues associated with some fruit fly species. Thus, effective disinfestation protocols need to be developed. Heat treatment has shown promise as a quarantine technology, but it injures pericarp tissue and results in skin browning. However, heat treatment can be combined with an acid dip treatment that inhibits browning. Therefore, the primary aim of postharvest litchi research remains the achievement of highly coloured fruit which is free of pests and disease. Future research should focus on disease control before harvest, combined acid and heat treatments after harvest and careful temperature management during storage and transport.

Effect of pH and temperature on peroxidase and polyphenoloxidase activities of litchi pericarp

“…Significant progress in purification and characterization of PO and PPO and its substrates in litchi pericarp tissue has since been made. Nonetheless, enzymatic browning is still the major practical limitation of litchi fruit storage (Jiang et al, 2003). The purpose of this study was to investigate the influence of pH and temperature on peroxidase and polyphenoloxidase activity and the enzyme inactivation by pH and heat.…”

An Intracellular Laccase is Responsible for the Epicatechin Mediated Anthocyanin Degradation in Litchi Fruit Pericarp

“…The white translucent aril and attractive red color due to high content of anthocyanins in the pericarp contribute significantly to their value. However, litchi pericarp coloration changes after harvest from red to brown due to a 50% decrease in anthocyanin concentration, indicating pigment degradation (Fuchs et al, 1993;Holcroft and Mitcham, 1996;Zhang et al, 2001;Jiang et al, 2006;Mayer, 2006). Revealing the anthocyanin degradation pathway during pericarp browning may help preserve the original red coloration of the fruit pericarp.…”

Lipofuscin-Like Substance Involved in Pericarp Browning of Postharvest Litchi Fruit During Storage

“…In this study, browning index of litchi fruit after 72 h of storage increased rapidly (Table 1), which associated with the obvious accumulation of lipofuscin-like substance. As loss of compartmentalization of (-)-epicatechin and anthocyanins with polyphenol oxidase (PPO) or peroxidase (POD) initiates the enzyme-catalyzed oxidation in the presence of oxygen, the oxidative products can further react with proteins or lipids and then form the brown-colored by-products [20]. Moreover, the formation of browning color of tea exhibited a similar reaction of quinines with proteins and lipids [21,22].…”