Enzyme activities and polyphenols related to mesocarp discolouration of avocado fruit

Abstract

Avocado fruit showing severe symptoms of the mesocarp discolouration disorder exhibited significantly higher extractable activities of soluble polyphenol oxidase and peroxidase, as well as higher levels of total phenols, hydroxycinnamic acids and proanthocyanidins, when compared to healthy fruit. However, l-phenylalanine ammonia-lyase activity was very variable, and no significant differences were observed between healthy and affected fruit. Extraction of healthy, but not severely affected, fruit in the presence of 0.1 % SDS resulted in increased polyphenol oxidase activity reflecting the release of bound and/or latent enzyme. Qualitative differences between healthy and affected fruit included different patterns of polyphenol oxidase multiple forms and different polyphenol profiles. The pattern of polyphenol oxidase multiple forms from SDS-extracted healthy fruit was similar to that from mildly affected fruit not extracted with detergent.