اثر تيمارهاي پس از برداشت كلسيم و گرما بر انگيزش مقاومت به سرما و كيفيت ميوه ليموي ليسبون

EFFECT OF POSTHARVEST CALCIUM AND HEAT TREATMENTS ON THE INDUCTION OF COLD TOLERANCE AND QUALITY OF ʹLISBONʹ LEMON FRUIT.

ʹLisbonʹ lemons {Citrus limon L. Burm.) were treated with CaCl2 solutions up to 7.5% (w/v) by methods of normal dip (ND, 15 °C, 25 min), hot dip (HD, 53 °C, 3 min), normal vacuum infiltration (NVI, 15 °C, -33 kpa, 10 min), and hot vacuum infiltration (HVI, 45 °C, -33 kpa, 10 min) before storage at 1.5 °C and 85% RH for 6 and 12 weeks and 1 additional week at 20 °C. The correlation coefficient between Ca content of peel and CaCl2 concentration showed that Ca uptake was raised slightly and affected by application method, concentration of CaCl2 and temperature. Storage for 6 weeks resulted in comparatively minor chilling injury (CI), so that treatments gave little additional benefit. After 12 weeks, for all application methods, the different treatments of CaCl2 only affected CI and weight loss of fruit, but did not alter other parameters. Normal dip at 3% CaCl2, NVI at 1.5% CaCl2, hot water dip alone and hot water infiltration alone were the most effective methods and reduced the severity of CI by 58.89, 53.25, 67.5, and 19.29 %, respectively. Hot CaCl2 solutions (HD and HVI) had no advantage compared with hot water alone, and at high concentrations increased CI and weight loss. CI, weight loss, ion leakage and internal quality of fruits were significantly affected by application methods of CaCl2 and by storage period. Fruits treated by ND and NVI, HD, and HVI methods showed significantly minimum, moderate and severe CI, respectively. A significant correlation was also found between CI and each of the other parameters. As CI increased, weight loss and ion leakage increased, and conversely vitamin C and acidity levels decreased. Similar trends were observed as the storage time advanced and CI increased.