依樹上結果部位選採較高品質椪柑之簡易方法

Abstract

本研究將四株椪柑之樹冠依方向及果實直接曝晒日光與否分成樹頂曝日、東北曝日、西南曝日、東北遮蔭、西南遮蔭等五區採果。曝日區果實著生於樹冠外圍或接近外圍，在白天至少有部分可照到陽光。而遮蔭區果實位於樹冠內部，幾乎整日沒有直接照到陽光。果實採收後個別套以PE 袋，置15℃貯藏1 個月後分析比較其品質。試驗連續做三年。結果採自三個曝日區的果實比採自2 個遮蔭區的果實具有較濃橙色(較高a*值與較小色相角)的果皮及較高可溶性固形物(°Brix)的果汁。至於三個曝日區之間或二個遮蔭區之間並無明顯的差異。但採自曝日區的果實有搾汁率略低於採自遮蔭區的果實之趨勢。若以可溶性固形物°Brix 乘以搾汁率之積視為果實總可溶性固形物含量來做比較，在所調查的三年之中採自西南曝日區之果實每年都最高而採自東北遮蔭區之果實每年都最低。採果時如將曝日的果實與嚴重遮蔭的果實分開，即可獲得品質較高且較一致的果品；而若單選西南曝日區的果實，則可獲最高品質的果品。 Each of the four selected mature ‘Ponkan’ mandarin (Citrus reticulata Blanco) trees were devided into five sections: top exposed, northeast (NE) exposed, southwest (SW) exposed, NE shaded, and SW shaded. Fruits on the exposed position were either on or near the surface of the tree canopy and were at least partially sunlit during the day while those on shaded position were located inside of the canopy and received practically no direct sunlight. Fruits were spot-picked from the five sections, individually wrapped in PE plastic bags, and stored at 15℃for 30 days before quality analysis. The experiment was repeated for three consecutive years. The fruits harvested from three exposed sections had more orange color, higher SIELAB a*, and smaller hue angle in the peel and had higher soluble solids in the juice than those harvested from two shaded sections. There were little differences in fruit color and soluble solids among the three exposed sections or between the two shaded sections. Exposed fruits tended to have slightly lower juice content than shaded fruits, however. When a comparison was made on the product of soluble solids and juice content, the fruits harvested from SW exposed section were always the highest and those from NE shaded section were always the lowest among the five sections in the three years of study. More uniform and higher quality ‘Ponkan’ mandarins with deeper orange-color and higher soluble solids can be obtained by simply spot-picking exposed fruits and excluding shaded fruits. The highest quality fruits can be spot-picked from the SW exposed position of the tree canopy.