Response of bananas to postharvest acid treatments

SummaryWhen the effects of pressure infiltrated (1.03 X 105 Pa, for 2 min) dilute acetic acid on the shelf-life of banana (Musa AAB ‘Embul’) were examined, a 0.2% acetic acid (pH 3) treatment showed a significantly low disease score. Of other acids at pH 3 (0.05% citric acid or 0.1% ascorbic acid), tested separately, citric acid significantly reduced disease incidence. A 0.12% benomyl (as ‘Benlate’) dip was the most effective. A three-factor combination of citric acid, acetic acid and `Benlate’, all at half strength showed the lowest disease score. The results indicate that ‘Benlate’ application could be reduced by half when applied concurrently with both citric acid and acetic acid. Firmness was higher in bananas treated with any one of the three acids and the effect was significant using citric acid and acetic acid. Ethylene ripening did not negate this firmness increase. Peel pH was only slightly lower in the acid treated bananas. Anthracnose lesions caused by Colletotrichum musae inoculated into fruits 24.h after treatment, were fewer when given the three-factor combination described above, indicating that postharvest acid treatment may increase fruit resistance to anthracnose, and the direct effect of acids on the pathogen is not the main cause of reducing disease. The acetic acid treatment slightly but consistantly delayed peel colour development in all experiments.