Studies on the Degradation of Testa of Cocoa (Theobroma Cacao L.) by Aspergillus, Species Isolated from Mouldy Cocoa Beans

Abstract

Cocoa beans at the Toma Warehouses were found to be conta minated with a total number of 21 fungus species, the predominant species belonging to the genus Aspergillus. The annual average contamination was 4,9 per centi Infection in the main crop was lower (39 per cent) than in the minor crop (6 4 percent ) . The higher the bean moisture content the greater the fungal infection . Extracts of testa of fermenting cocoa beans depressed vegetative growth in Aspergi l lu s f la vus≫ Aspergillus fumjgatus, Aspergillus niger, Aspergil lu s t amari i and Sclerotium r o l f s i i* iS, r o l f s i i was more inhibited than the AspergiTlua species Extracts of testa of beans already fermented and being dried had no e f fe c t on growth of mycelium of the Aspergillus species but stimulated that o f S. r o l f s A. fumjgatus grew best in Sabouraud's broth medium while A. tamari grew best in Czapek Dox broth medium* Cotyledons and testa of cocoa beans possessed phenolic compounds; free phenols, orthodihydric phenols, f lavonols and anthooyanins, The quantities of these compounds changed in different ways during curing of the beansc Free phenols content in both cotyledons and testa decreased during fermentation and drying of the beans, Orthodihydric phenol lev e ls in both cotyledons and testa , on the other hand, increased during fermentation and decreased during drying of the beans„ Flavonol content in the cotyledons increased during fermentation and decreased during drying, while it decreased in the testa during both fermentation and drying. The anthocyanin content of the cotyledons decreased with curing but increased s ign if ican t ly in the testa . Some of the phenolic compounds inhibited germination of conidia and germ tube growth in A. f la vu s . li. fumigairus. And A tamarii and germination o f s c le r o t ia of rolfsi i to varying degrees. Others, however, stimulated germination. The compounds in either case were not identified* Fungal contamination of cocoa beans was observed in unfermented fresh cocoa beans and in beans at various stages of fermentation and dryingt Invsuling fungi occupied mainly the micropylar and stylar regions of the beans, The composition of the flora- changed as fermentation and drying of the beans progressed.