香蕉PE套袋藍色深淺對果實日燒、色澤及後熟之影響

Effect of PE Bunch Covers with Different Blue Colour Gradings on Sunburning, Appearance, and Ripening of Banana Fruit

瞭解香蕉套袋之藍色深淺對果實日燒發生、色澤及後熟之影響，以及在不同季節套袋之差異，進而評估目前使用之深PE藍色套袋，其藍色色母用量是否可以減少，以降低套袋成本（蓋藍色色母價格約為PE原料之3倍），乃將藍色色母／PE原料用量比為1／1 0（現行深藍色套袋所用製造比例）、1／20、1／30、1／50及透明不含色母等五種套袋，就10月下旬至翌年4月底終花之高屏區香蕉進行套袋試驗。結果顯示，香蕉日燒之發生及程度，除套袋顏色之有、無（藍色或透明）及藍色之深淺有差異外，在不同月別終花套袋之香蕉間，亦有極大之差異。一般香蕉採收期愈處高溫季節，果實日燒機會愈大且愈嚴重。在較低溫季節，日燒不發生或極經微。不同套袋處理間，在2～4月套袋之香蕉，以透明套袋日燒率最高，達18～32%左右（包括紅頭而尚未焦黑及已焦黑者），其次為色母用量比1／50者，日燒率為8～13%左右，而色母用量比1／10、1／20及1／30立套袋，則日燒率顯著降低，三者間並無顯著差異。就果實外觀顏色而言，一般在較低溫季節採收者，套袋處理間差異不明顯，果實呈綠色～深綠色；然在高溫季節採收者，透明套袋香蕉，顏色則呈淡黃綠色，1／50者呈淡綠色， 而1／10、1／20及1／30者呈綠色～深綠色，且三者差異不明顯。又香蕉彩收後，經乙烯處理（20°C，1000 ppm）之轉色黃化及櫥架壽命，在不同套袋處理之香蕉間，並無顯著差異。因此，從果實日燒及色澤之觀點，透明套袋及極淺藍色套袋（色母用量1／50）顯不適於高屏蕉圍之果房套袋，特別是套袋香蕉在高溫採收者，從降低套袋成本之觀點，現行使用之藍色PE套袋，其色母／PE用量比，應可由現行之1／10降至1／20或1／30，而並不顯著影響果實日燒及色澤。文中並就果實日燒之發生，從溫度、光強度及果齡之觀點加以討論。

This trial was conducted in Kao-Ping plantations to investigate the effect of PE bunch covers with various blue color gradings on sunburn, appearance, and ripening of banana fruit on different covering months (Oc t. -Apr.) during 1979~80. There were five color bunch cover treatments including A). The blue master batch/PE granule ratio at 1/10, -the present covers' ratio, B). at 1/20. C). at 1/30, D). at 1/50, and E). clear covers without color. Results showed that the percentage and severity of sunburn were not only different in bunch covers treatments, but also on covering months. Usually, sunburn occurred in hot weather. Among treatments, the percentage of sunburn on Feb. to Apr. emerged fruit was highest in treatment E, about 18~32%, including brown tip and black fruit; with follows in treatment D, about 8~13%. The sunburn were significantly lower in treatment A, Band C than that of D and E, and there were no significant difference within these three treatments. From fruit appearance point of view, where bananas harvested before hot season, there were no differences among treatments, all fruit shown green-dark green color. Nevertheless, for hot season-harvested bananas, the clear cover-treated fruits (treat. E) shown pale green with trace yellow color, and treat. D in light green color, while treat. A, B and C shown green-dark green color. There were no difference in color yellowing and shelf life span after ethylene treatment (1,000 ppm, at 20°C) among the treatments. Based on sunburn and appearance, it appeared that the clear bunch covers and light blue color covers with the master batch/PE granule ratio at 1/50 were not suitable to bunch covering in Kao-Ping area, especially in February-emerged fruit. Since the price of blue master batch is triple higher than PE granule in terms of the cost of PE bunch covers, the blue master batch/PE granule ratio of the present-used dark blue covers could be reduced from 1/10 to 1/20 or 1/30. In this report the sunburning of banana fruit was also discussed in points of temperature, light intensity, and maturity of fruit.