兩段著色香蕉之後熟生理及催熟技術

Abstract

台灣4-6月採收之香蕉，在乙烯催熟處理後，部份香蕉發生轉色（褪綠轉黃）困難之所謂兩段著色香蕉或青丹蕉之問題經常發生，造成香蕉催熟加工業者相當之困擾。據研究顯示，兩段著色香蕉與正常香蕉在乙烯（1000ppm）催熟處理後之後熟行為有相當大之差異；兩段著色香蕉除了果皮葉綠素分解較慢，轉色較困難外，果實軟化及可溶性固形物含量（°Brix）之增加，亦明顯較慢，且後熟果過程之呼吸率及乙烯產生量亦均較低，但果肉ACC含量在乙烯處理第3天後，明顯遠超過正常香蕉，且一直到後熟後期仍繼續增加中，推測可能與果肉缺O2有關。從果皮組織之細胞結構上觀之，亦顯示兩段著色香蕉之果皮組織細胞較小，且排列緊密，可能影響果實內外之氣體交換。此外，兩段著色香蕉在乙烯處理後之果實內部O2濃度亦快速降至5％左右，明顯較正常之香蕉為低。以上資料可相互佐證，兩段著色香蕉由於果皮細胞結構之差異，造成果實內外氣體交換能力之減低，進而影響香蕉之後熟與轉色。 克服香蕉在乙烯催熟後發生兩段著色之問題，利用提高乙烯用量或提高乙烯處理時或轉色時之溫度，對改善兩段著色問題均無效或效果不彰。但提高大氣中O2濃度（40%)，則可顯著改善香蕉發生兩段著色之問題，且可提高兩段著色香蕉之可溶性固形物含量及風味，但在高溫下（20-32℃）銷售，會明顯縮短香蕉之櫥架壽命“因此，利用提高催熟時大氣中O2濃度之催熟技術，來克服香蕉發生兩段著色之問題時，香蕉在移出催熟室後不宜在高於15℃之環境下銷售，以免顯著縮短香蕉之櫥架壽命。 In Taiwan, some of the banans harvested during March to June fail to turn yellow, i.e., degreen at an extremely slow rate after ethylene treatment. The affected bananas are locally called “Two-Zone Color bananas” or “Uneven coloring bananas” and pose unusual problems for postharvest physiology and ripening agencies. After ethylene treatment, the Two-Zone Color bananas showed a lower rate of chlorophyll degradation, degreening of peel color, softness and total soluble solids increasing than those of normal bananas. The respiration rate and ethylene production of Two-Zone Color bananas were also lower than those of normal fruits after ethylene treatment. However, the pulp ACC content of Two-Zone Color bananas showed continuously increase following fruit ripening and its content higher than those of normal ones. From microscopic observation, the cell of peel tissue of Two-Zone Color bananas showed smaller and closer than those of normal fruits. It seemed affecting the gas exchange through peel tissue. The internal oxygen content of Two-Zone Color bananas decreased quickly after ethylene treatment, and then remained at low level (5%) during ripening period. However, the gas content of normal bananas decreased slowly and had a higher oxygen content. To improve the degreening of Two-Zone Color bananas during artificial ripening, increasing ethylene dosage and treatment temperture had no positive effects on degreening. However, the degreening rate can he improved by increasing the atmospheric oxygen concentration from 21% to 40% during ripening processes. The total soluble solids and flavor were also increased by enhanc ing oxygen concentration while the shelf life was reduced, especially at higher temperature(20-32 ℃) after bananas moved out of ripening room. Therefore, to overcome the uneven coloring propblem of Two-Zone Color bananas during ripening by using high atmospheric oxygen (40 %) technigue, the temperature of bananas, after moved out of ripening room, will be no higher than 15℃ to avoid significant reducing the shelf life of bananas.