Spoilage in desiccated coconut resulting from growth of xerophilic fungi

Effect of water activity, modified atmosphere packaging and storage temperature on spore germination of moulds isolated from prunes

The combined effect of medium water activity (aw) modified atmosphere packaging (MAP) on the conidial germination of Aspergillus niger, Eurotium amstelodami, Penicillium chrysogenum and Fusarium oxysporum was studied by applying response surface methodology (RSM) for 45 days incubation at 20, 30 and 40 degrees C. Oxytetracycline glucose yeast extract (OGYE) agar media were prepared over a wide range of aw (0.80-0.95), controlled by glucose. The headspace atmosphere composition varied from 0-20% for O2 and from 0-80% for CO2 with N2 as balance in the ratio medium/gas mixture of 1/3 (v/v). The results of this experiment were confirmed by repeating some combinations (aw-MAP) in the zone where the inhibition was effective. In contrast to A. niger which germinated and grew better at 30 and 40 degrees C, P. chrysogenum and F. oxysporum were capable of germinating and growing at 20 degrees C but not at 40 degrees C. E. amstelodami was less influenced by the incubation temperature than were the other species. Under anaerobic atmospheres, germination and growth of all tested species were completely inhibited at low aw, while at high aw because of residual O2, conidia germinated but failed to grow. At any aw value between 0.88 and 0.92, conidia failed to germinate when 100% CO2 was applied. Similar results were obtained for E. amstelodami and F. oxysporum in 80% CO2-20% N2 and 60% CO2-40%N2. Under aerobic conditions, at 5% O2 germination and growth occurred only at high aw, while 10 or 20% O2 combined with either 80 or 60% CO2 conidial germination and mould growth were only delayed comparing to the control (air).

Ethanol production in table jelly by two species of Chrysosporium

Different commercial brands of tablet jelly were stored in sealed containers for 12 weeks at an initial water activity of 0.90. The surface of those containing real fruit juice became covered with a dense white mould identified as Chrysosporium inops. That of those without fruit juice did not. This type of spoilage has been observed in commercially stored samples. When spores of this fungus and the closely related species, C. xerophilum, were added to commercial tablet jelly, the fungi grew only on samples containing real fruit juice. It is suggested that the fruit juice may provide some essential nutrient required for growth of these nutritionally fastidious species as well as the fungal spores themselves. Ethanol was detected in the headspace gas of stored samples of mouldy jelly. The production of ethanol by the two Chrysosporium species was confirmed by fermentation of glucose in liquid batch culture: approximately 2% ethanol was formed in 14 d. The ability of C. xerophilum and C. inops to utilize the Embden-Meyerhof-Parnas pathway may explain why these slow-growing xerophilic moulds become dominant after storage at low oxygen tension.