荔枝果實收穫後保鮮效果之研究

Studies on Postharvest Quality Preservation of Lychee (Litchi chinensis Sonn) Fruit

荔枝果實構造特殊，果皮與果肉間幾無輸導組織連擊，果皮大部由琉鬆的海線組織構成，輸導組織亦不發達，保水能力極弱。當果皮不份蒸散時，因果肉水分未能有效矛以補充，以致果皮幹枯而褐化變硬，此時果皮的海綿組織收縮，細胞間隙大量減少；細胞間相互擠壓變形，果皮表面形成緊密結實之膠質狀物質，全面覆蓋對閉整個果實表面，可能因而造成果肉組織在缺氧環境下生無氧呼吸而變味，使風味減低，迅速變壞。本試驗證明荔枝果實一日變色，二日變味之現象，與果皮失水有極為密切之相關。故保持高溫狀態的貯運環境是決定荔枝貯運壽命最重要的因素之一。在低溫高溫的環境下，若保持果實不病原菌感染，經貯藏42天仍具極高之商品品質。果皮之褐變時間是在果皮水份損失殆盡後，或是發生病原菌感染發霉前才發生褐變，但病原菌感染所引起之褐變，在發生時間上，遠比失水所發生之褐變為遲。果實經貯藏後之病原菌感染種類，經分離觀察結果，為害果皮這之閏原菌達12種，為害果肉這病原菌達11種。

The connection between the peel and the pulp of a lychee fruit is very loose. The peel consists primarily spongy parenchyma cells with large intercellular spaces. It lost water readily. Water lost from the peel can not be replenished easily from the pulp, thus rapid transpiration could causes excessive desiccation and browning of the peel. As soon as the spongy parenchyma tissue shriveled, cells became malformed and a cutinized substance covering on the peel surface was found. The cutinized substance might result in oxygen deficiency of the inner part of the fruit, thus causing anaerobic respiration and off-flavor in the pulp. Quick cooling and holding the harvested fruit in high humidity were the two most important methods to preserve the color and freshness of the fruits. Lychee was successfully stored for 42 days at 3±1℃ with high humidity when rot-causing microorganisms were absent. Eleven and 12 species of microbes were isolated from the pulp and the peel respectively in some fruits after storage.