Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Proceedings
Publication Acceptance Date: 8/30/2007
Publication Date: 3/20/2008
Citation: Rattanapanone, N., Plotto, A., Baldwin, E.A. 2007. Effect of edible coatings and other surface treatments on pericarp color of thai lychee cultivars. Proceedings of Florida State Horticultural Society. 120: 222-227. Interpretive Summary: Lychee is a non-climacteric subtropical to tropical fruit of high commercial value on the international trade market. This fruit, however, is highly perishable due to rapid loss of bright red peel color which turns brown within 24 to 28 h after harvest. This paper represents ongoing research aimed at testing methods to preserve the red color of lychee fruit peel to replace using sulfur dioxide treatments due to consumer health concerns. Acidic treatments using natural fruit acids or vitamin C were tested with and without edible food grade coatings. Some acidified coating treatments or powders were successful at delaying loss of red color, while preserving the vitamin C content of the fruit and maintaining freshness.
Technical Abstract: Lychee fruit (Litchi chinensis Sonn.) have a brilliant red pericarp upon harvest that turns brown during shipping and storage. 'Hong Huay' and 'Juckapat' lychee fruit were harvested at the commercial stage (90-100% red pericarp) in Thailand. In five separate experiments, fruit with pedicels were dipped for 30 s in various treatment solutions including: no dip and water as controls, ascorbic acid, citric acid, acetic acid, chitosan, HCl, and two Semperfresh products, in an effort to retard browning of the percarp. Fruit were air-dried, and stored at 2 or 10 °C with 90% relative humidity for 1-3 weeks. Total soluble solids (TSS), tritratable acidity (TA), weight loss, total ascorbic acid (TAA) and color (hue angle and chroma) were measured over the storage period. During storage, TSS generally increased while TA and TAA generally decreased (except for those treatments that were treated with ascorbate). Most treatments reduced weight loss compared to untreated fruit. Treatment of lychee fruit with acidified coatings including Semperfresh, acidified Semperfresh (with 2% citric acid), Semperfresh Lychee Treatment Power (LTP) + citric acid and chitosan + HCl sometimes resulted in brighter, redder color than control fruit, as evidenced by lower hue angle or higher chroma values.