Hot water treatments improve 'Hass' avocado fruit quality after cold disinfestation

The potential for hot water treatment (HWT) to improve quality of 'Hass' avocado following cold disinfestation for fruit flies, was investigated. Avocado fruit were placed in water at 38-42degreesC for 20-60 min, disinfested for 16 days at 1degreesC, then ripened at 20degreesC. In the following season, fruit from another orchard were treated with hot water at 39-42degreesC for 20-30 min, disinfested as above, then ripened at 16degreesC. In both seasons, HWT significantly reduced skin damage caused by cold disinfestation, with 40degreesC for 30 min, 41degreesC for 20-30 min and 42degreesC for 2-30 min giving the greatest reduction. Hot water treatments also reduced body rots in ripe fruit, with 40 and 41degreesC for 30 min being consistently the most effective. Treatment at 42degreesC increased body rots compared to the other HWTs in one season, and them was no benefit of HWT times longer than 30 nun. The severity of vascular browning (VB) and mesocarp discolouration (MD) in ripe fruit was generally low, and increased following cold disinfestation. Hot water treatments reduced VB severity but had no effect on MD. Treatment at 41degreesC for 25-30 min and 42degreesC for 25 min increased the percentage of externally acceptable fruit (less than 5% of the skin area with defects) from 0 to about 80% 3 days after removal from disinfestation. The same treatment also increased the percentage of ripe fruit with acceptable flesh quality (less than 5% of the flesh with rots or disorders) from 0 to 16-20%, due mainly to reduced body rots. These results indicate the commercial potential of HWTs of about 41degreesC for 25-30 min, or 42degreesC for 25 min to improve avocado external and internal fruit quality following cold disinfestation. (C) 2002 Elsevier Science B.V. All rights reserved.