Prediction of physiological maturity and role of heat, calcium chloride and potassium permanganate on storage life of 'Golden Delicious' apples in cold storage

Apple is a climacteric fruit that can ripen if harvested mature. To store fruits successfully they must be harvested at the correct physiological maturity. In the present study the Smith method (Smith, 1985) was used to predict time of maturity and then compared with the starch test. According to the Smith method, harvesting times in 1999 and 2000 were predicted to be 136 and 142 days after full bloom (DAFB) and according to the starch test 137 and 141 DAFB, respectively. After determining maturity, fruit were harvested and vacuum infiltrated (250 mm Hg) for 30 sec. with 0, 4, or 6% CaCl(2) solutions followed by heat treatment for 0, 48 or 72h at 38 degrees C. Treated fruit were stored at 0 degrees C with RH of 85-90% for 2.5 and 5 months, followed by 1 week at 20 degrees C. Fruit treated with 4 and 6% CaCl(2) had significantly enhanced calcium content of after 2.5 and 5 months at 0 degrees C compared to controls. The correlation between calcium concentration and calcium content of fruits was highly significant (r(2) = 098(star star)). There was a positive correlation between fruit firmness and calcium content of fruit and regression coefficients after 2.5 and 5 months storage at 0 degrees C were 0.77 and 0.83, respectively. Heat treatments for 48 and 72h at 38 degrees C increased fruit firmness. Calcium chloride at 4 and 6%, plus heat treatment increased fruit firmness of those fruit held 1 week at 20 degrees C after removal from cold storage. Calcium chloride plus heat treatment had no significant effect on total soluble solids. Treatment with CaCl(2) decreased internal breakdown. Vacuum infiltrated fruits with 4 and 6% solution of CaCl(2) plus potassium permanganate (0, 10, or 20 g/bag) had no significant effect on fruit firmness but potassium permanganate alone significantly increased fruit firmness.