Sequential changes in starch, sugars, organic acids, and headspace volatiles were determined on single soursop fruits from harvest to fruit breakdown. Sucrose increased 4-fold; maximum concentration occurred 3 days after harvest, then declined to 40% of the peak value. Fructose and glucose increased slowly to a peak 5 days after harvest. The ratio of sucrose, glucose, and fructose, respectively, at the edible ripe stage was 4.3:3.0:3.2. There was a 7-fold increase in malic acid and a 3-fold increase in citric acid. Both acids peaked 3 to 4 days after harvest, then declined. About half of the organic acids were present as salts. Headspace volatile production paralleled ethylene evolution. Volatile production began to increase 3 days after harvest and peaked 2 days later. This peak corresponded with the peaks in total sugars, organic acids, and the edible ripe stage when individual fruit results were compared on the basis of the start of the climacteric respiratory increase. After the peak in volatile production, there was a dramatic drop over the next 3 days in major fruity esters produced, with a gradual increase in volatiles, which probably imparted the off-odor of the overripe fruit. The activities of amylase, polygalacturonase, and cellulase increased during ripening. Starch breakdown leading to sugar and organic acid production occurred before any rise in ethylene production. This breakdown of starch may be an important initiating event in the ripening of soursop fruit.
Physiological changes accompanying anthurium flower (Anthurium andraenum Andre) senescence were monitored. Silver pulse treatment of flower stems was used to modify the senescence process. Florets on the spadix continued to open for 5-10 days after harvest. In both treated and untreated flowers, respiration rate was low until senescence began 8 days after harvest. The rate of increase in respiration of silver treated flowers was half that of the controls. Ethylene production remained low throughout the postharvest life of the flowers. Ten days from harvest spathe color began to change from red to blue with no significant changes in the ratios of the anthocyanins. There was a simultaneous change in tissue pH, from 5.2 to 5.6. Tissue organic acids remained constant during senescence. There was a significant increase in spathe tissue ammonium ion due, apparently, to protein breakdown which probably caused the increase in tissue pH. The concentration of tissue phenolics increased during senescence and could have intensified the color change by copigmentation. Flower senescence apparently was not due to a shortage of carbohydrates, though tissue starch levels did decline by about 25%. The ratio of free sugars in the stem, spathe and spadix remained constant with a slight decline in concentration during postharvest life. Senescence probably was caused by water stress due to stem plugging of undetermined nature. Silver-pulsing of the stem reduced the amount of plugging and therefore reduced the rate of change of all the senescence processes.
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