Growth inhibition of tomato-rot fungi by phenolic acids and essential oil extracts of pepperfruit (Dennetia tripetala)

Phenolic and essential oil extracts of pepperfruit (Dennetia tripetala) showed antifungal activity against Saccharomyces cerevisiae, Saccharomyces sp., Candida tropicalis, Candida sp., Cryptococcus sp., Geotrichum sp., Rhizopus stolonifer, Aspergillus niger and Fusarium sp. isolated from spoilt tomato fruits and cultured on agar plates. Antifungal activity of phenolic and essential oil extracts was observed at inhibitory concentrations (IC) in the range of 2.5-6.5 and 1.5-3.0 mg/ml tomato/glucose medium respectively. Combination of phenolic and essential oil extracts at concentrations below IC values significantly retarded growth of fungi resident in blended freshly harvested and open market tomato fruits. These fungi were not detected in the tomato after 1 month storage when mild heat (80 degrees C for 1 min) and NaCl (10 mg/g) were combined with the phenolic and essential oil extracts as preservative hurdles. The population of challenge fungi in blended tomato treated with the same low concentration of the extracts and salt but without heat hurdle, steadily declined till none was detected after 3 months. Being an edible fruit, pepperfruit extracts may prove a useful natural preservative in food processing. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.