Influence of pre-harvest sprays of calcium nitrate on storability and quality attributes of plum fruits

The effects of pre-harvest applications of calcium nitrate at different concentrations were investigated on storability and quality attributes of plum fruits under low temperature storage. Uniform and healthy trees of plum cv. Satluj Purple were sprayed with calcium nitrate (1.0%, 1.5% and 2.0%) in 2nd and 3rd week of April and control trees were water sprayed only. Fruits from treated and control trees were harvested at colour break stage, and then stored at low temperature conditions (0–1 °C and 90–95% RH) for 35 days. Evaluation of physico-chemical parameters and enzymatic activities were made on the day of harvest and after 7, 14, 21, 28 and 35 days of storage. The colour of the fruits with respect to a* and b* values (green–red and blue–yellow spectrum, respectively) improved progressively up to 35 days of storage, whereas, fruit firmness decreased. Total sugars and pectin methylesterase (PME) and cellulase activities increased up to 28 days of storage before showing a declining trend. Two superimposed sprays of calcium nitrate (2.0%) enhanced the storage life of plum fruits up to 28 days by reducing physiological loss in weight (PLW), PME and cellulase activities, delaying development of fruit colour & anthocyanin and retaining sensory quality, firmness and total sugars in plum fruits.