Abstract
Two experiments with Emperor and one with Thompson Seedless grapes were made to test the relation of decay and bleaching injury to storage air velocity and relative humidity and to the initial and storage doses of SO2. Air velocities from 12 to 160 feet per minute had no significant effect on either rate of spread of decay or amount of bleaching injury. Storage relative humidities (RH) of 75, 85, and 95% had no significant effect on the decay of Emperor grapes if the dose of SO2 was adjusted to provide the same sustained concentration around the grapes at each RH level. This adjustment, to compensate for absorption, necessitated increasing the dose for each SO2 concentration by about 19% for each 10% increase in RH. At the same time the dose of SO2 at each RH needed to be increased by about 80% to raise the concentration from 0.025% concentration to 0.05% concentration, by about 65% from 0.05% to 0.1% concentration, and by about 50% from 0.1 to 0.2% concentration of SO2.
Decay in Thompson Seedless grapes increased significantly with RH, indicating that the SO2 dose adjustment used for Emperor grapes was not adequate for Thompson Seedless. Concentrations of 0.5 and 0.25% SO2 used in the initial treatment and 0.2 to 0.025% in weekly storage treatments had a highly significant effect on the rate of spread of decay and amount of bleaching injury of Emperor grapes, and on decay of Thompson Seedless grapes.
- Copyright 1964 by the American Society for Enology and Viticulture
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