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Effect of water activity, modified atmosphere packaging and storage temperature on spore germination of moulds
1Department of Food Science, Ecole Nationale d'Agriculture, Meknes, Morocco.
Abstract:
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).
Insights
Modified atmosphere packaging (MAP) and water activity (aw) effectively inhibit mold growth. High carbon dioxide levels and low water activity are key factors in preventing fungal germination and growth.
Area of Science:
- Food Science
- Microbiology
- Mycology
Background:
- Fungal contamination poses a significant challenge to food preservation.
- Understanding the combined effects of environmental factors on fungal growth is crucial for developing effective control strategies.
Purpose of the Study:
- To investigate the synergistic effects of modified atmosphere packaging (MAP) and water activity (aw) on the germination and growth of key food spoilage fungi.
- To determine optimal conditions for inhibiting Aspergillus niger, Eurotium amstelodami, Penicillium chrysogenum, and Fusarium oxysporum.
Main Methods:
- Response surface methodology (RSM) was employed to study fungal responses.
- Experiments were conducted over 45 days at varying temperatures (20, 30, 40°C).
- Media with controlled water activity (0.80-0.95) and modified atmospheres (0-20% O2, 0-80% CO2, N2 balance) were used.
Main Results:
- Complete inhibition of fungal germination and growth occurred at low aw under anaerobic conditions.
- High CO2 concentrations (100% or 80% CO2) effectively inhibited germination across a range of aw values.
- Aerobic conditions with 5% O2 allowed growth only at high aw, while higher O2 levels with CO2 only delayed growth.
Conclusions:
- Combined MAP and controlled aw are highly effective in controlling fungal spoilage.
- Specific gas compositions and water activity levels can be tailored to inhibit target fungal species.
- This research provides valuable insights for extending the shelf-life of food products through optimized packaging strategies.