PREDICTING MARKET QUALITY OF GRAPEFRUIT AFTER HOT-AIR QUARANTINE TREATMENT

Early, mid-, and late-season grapefruit (Citrus paradisi Macf.) were treated with hot air at 46, 48, and 50C for 3, 5, or 7 hours to determine the effects of time and temperature on market quality. Early and late-season fruit were more easily damaged by the higher temperatures than midseason fruit. Increased times at the lower temperatures had less of a deleterious effect on weight loss, loss of firmness and color, and susceptibility to scalding injury and fungal decay than did shorter times at the higher temperatures. Nevertheless, regression equations predicted that 3 hours at 48C or 2 hours at 49C would not adversely affect market quality of early and midseason fruit. The suitability of these equations was verified through taste tests of juice. It may not be possible, however, to raise the treatment temperature for late-season fruit above 47.5C without damaging the quality of juice from these fruit.