Starch iodine test for determining maturation of apple fruit | 淀粉-碘染色法确定苹果成熟度

Chinese. 建立一种可靠、易于推广的科学判断苹果成熟度的方法，用于指导苹果规范采收。以“嘎拉”、“秦冠”和“富士”苹果为试材，于其成熟期内每周采样1次，测定果实生理指标，并将果实横切后用碘液染色，选取有代表性的苹果染色切面照相。随着果实的成熟，其硬度下降，可溶性固形物含量（SSC）升高，可滴定酸含量（TA）呈下降趋势，着色率和淀粉指数（SI）升高，后期发生乙烯跃变。根据果实切面淀粉染色程度由深至浅分为8级，制作了3个苹果品种的淀粉染色图谱，依照该图谱，“嘎拉”、“秦冠”和“富士”苹果分别在淀粉指数为4.5，6.0和7.7时，达到园艺成熟度，此时为适宜的采收期。苹果果实的淀粉指数与其品质和成熟期显著相关(P＜0.05），因此它可以客观地反映苹果的成熟度，所制作的图谱可以在“嘎拉”、“秦冠”和“富士”苹果的商业采收中推广应用。

English. A reliable and practicable method to determine the optimum harvest date for apple fruit was studied to provide instruction to apple commercial harvest. Apple fruit cultivar “Gala”, “Qinguan”, and “Fuji” were harvested at 7 d intervals during different maturing stages. Physiological indices were measured at the harvest date. Typical stained apple transverse sections were selected to take pictures. Fruit firmness decreased, while soluble solids content (SSC), coloring ratio, and starch index (SI) increased during apple maturing. Titratable acidity (TA) decreased or did not change significantly. Ethylene climacteric happened at the end of apple maturing. Starch test guide for three apple cultivars were created. According to the guides, apple should be harvested for the long-term storage when the starch index reached 4.5, 6.0, and 7.7 for “Gala”, “Qinguan”, and “Fuji” apples respectively. SI was significantly correlated with fruit quality indices (P＜0.05), which also reflected the maturing stage of apple fruit. The starch test guide created in this study can be applied to apple commercial production.