Elsevier

Food Chemistry

Volume 88, Issue 3, December 2004, Pages 443-446
Food Chemistry

Advances in understanding of enzymatic browning in harvested litchi fruit

https://doi.org/10.1016/j.foodchem.2004.02.004Get rights and content

Abstract

Litchi (Litchi chinensis Sonn.) is a subtropical to tropical fruit of high commercial value in international trade. However, harvested litchi fruit rapidly lose their bright red skin colour. Peel browning of harvested litchi fruit has largely been attributed to rapid degradation of red anthocyanin pigments. This process is associated with enzymatic oxidation of phenolics by polyphenol oxidase (PPO) and/or peroxidase (POD). PPO and POD from litchi pericarp cannot directly oxidize anthocyanins. Moreover, PPO substrates in the pericarp are not well characterised. Consequently, the roles of PPO and POD in litchi browning require further investigation. Recently, an anthocyanase catalysing the hydrolysis of sugar moieties from anthocyanin to anthocyanidin has been identified in litchi peel for the first time. Thus, litchi enzymatic browning may involve an anthocyanase–anthocyanin–phenolic–PPO reaction. Current research focus is on characterising the properties of the anthocyanase involved in anthocyanin degradation. Associated emphasis is on maintenance of membrane functions in relation to loss of compartmentation between litchi peel oxidase enzymes and their substrates.

Introduction

Litchi (Litchi chinensis Sonn.) is a subtropical to tropical fruit of high commercial value in international trade. The fruit typically has a bright red peel colour and is sweet, acidic, juicy and soft but with crisp pulp (Nakasone & Paull, 1998). Harvested litchi fruit are highly perishable. They can rapidly lose their bright red skin colour and turn brown within 1–2 days at ambient temperatures (Huang & Scott, 1985; Jiang & Fu, 1998a; Zhang & Quantick, 1997). Post-harvest browning of litchi fruit has been attributed mainly to degradation of red pigments in association with oxidation of phenolics by polyphenol oxidase (PPO) and/or peroxidase (POD) enzymes (Huang, Hart, Lee, & Wicker, 1990; Zauberman et al., 1991; Zhang & Quantick, 1997). Li and Yan (1963) first discerned the relationship between PPO activity and litchi peel browning. Significant progress in purification and characterisation of PPO and its substrates in litchi pericarp tissue has since been made. Nonetheless, enzymatic browning is still the major practical limitation to litchi fruit storage (Jiang, Yao, Lichter, & Li, 2003). This paper reviews enzymatic browning of litchi fruit after harvest, with an emphasis on recent advances.

Section snippets

Polyphenol oxidase

Litchi pericarp tissue browning is mainly due to the oxidation of phenolics and degradation of red pigments by polyphenol oxidase. This oxidase is also referred to as catechol oxidase, tyrosinase, catecholase or o-diphenol oxygen oxidoreductase. PPO has been isolated and purified from litchi fruit peel. Its pH and temperature optima are 6.5 and 70 °C, respectively (Jiang, Zauberman, & Fuchs, 1997b; Jiang, Zauberman, Fuchs, & Fu, 1999). The enzyme can be inhibited by antioxidants, such as

Pigments and browning substrates

Compared with the literature on PPO and POD enzymes, there are very few publications relating to the role of anthocyanins in litchi pericarp browning. Prasad and Jha (1978) and Rivera-Lopez, Ordorica-Falomir, and Wesche-Ebeling (1999) identified anthocyanins as the red pigments present in litchi pericarp. Lee and Wicker (1991) subsequently reported that litchi pericarp contains seven types of anthocyanins (cyanidin-3-rutinoside, cyanidin-3-glucoside, cyanidin-3-galactoside,

Peroxidative activity and membrane lipids

Oxidative enzymes and their substrates are in different subcellular compartments in red intact litchi fruit pericarp (Liu, Jiang, Chen, Zhang, & Li, 1991). Accordingly, compartmentation limits mixing that results in enzymatic browning (Liu et al., 1991). Peroxide content and malondialdehyde (i.e. a product from peroxidated membrane lipids) concentrations increase in aging litchi fruit. Conversely, superoxide dismutase activity, associated with the anti-oxidant capacity of litchi pericarp

Concluding remarks

Impetus for research on litchi fruit deterioration in China and elsewhere has come in conjunction with increased production and demand around the world. The major producer, China, seeks to identify domestic and international markets for this unique and popular fruit. Post-harvest browning of litchi fruit skin is the main limitation to market acceptance. The biochemistry of enzymatic browning has not yet been fully elaborated (Jiang et al., 2003; Peng, 1998). However, it is proposed that

Acknowledgements

This work was supported by the International Foundation for Science (Grant No. E2265/3F) and the National Science Foundation of China (Grant No. 39900102).

References (37)

  • Y.Z. Chen et al.

    A study on peroxidase in litchi pericarp

    Acta Botanica Austro Sinica

    (1989)
  • Q.Q. Gong et al.

    Partial characterization of soluble peroxidase in pericarp of litchi fruit

    Progress in Biochemistry and Biophysics

    (2002)
  • P.Y. Huang et al.

    Enzymatic and color changes during postharvest storage of lychee fruit

    Journal of Food Science

    (1990)
  • P.Y. Huang et al.

    Control of rotting and browning of litchi fruit after harvest at ambient temperatures in China

    Tropical Agriculture

    (1985)
  • Y.M. Jiang

    Role of anthocyanins, polyphenol oxidase and phenols in lychee pericarp browning

    Journal of the Science of Food and Agriculture

    (2000)
  • Y.M. Jiang et al.

    Effect of spermidine on regulation of senescence of litchi fruit and its relation to ethylene

    Chinese Journal of Botany

    (1995)
  • Y.M. Jiang et al.

    Effect of postharvest treatment with 6-BA on quality of litchi fruit

    Tropical Science

    (1998)
  • Y.M. Jiang et al.

    Biochemical and physiological changes involved in browning of litchi fruit caused by water

    Journal of Horticultural Science and Biotechnology

    (1999)
  • Cited by (311)

    View all citing articles on Scopus
    View full text