Use of Antimycotics, Modified Atmospheres, and Packaging to Affect Mold Spoilage in Dairy Products
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Growth of Penicillium roqueforti, Aspergillus niger, Geotrichum candidum and Neosartorya fischeri were evaluated in atmospheres of 0:30:70, 0.5:29.5:70, 1:29:70, 2:28:70, and 5:25:70, O2:CO2:N2 over a 5-day period. Spores were cultured on antibiotic-supplemented potato dextrose agar (pH 5.6, aw 0.95) and incubated at 25oC. All four molds germinated and grew at 0.5:29.5:70. Extent of mycelia growth diameter (mm) increased significantly (P<0.05) as oxygen concentration increased from 0.5% to 5%. All growth was inhibited at 0:30:70, but germination and growth occurred once cultures were exposed to 20.9% atmospheric O2, indicating that a modified atmosphere containing no residual O2 is fungistatic.
Yeast and mold growth was seen in ultra-pasteurized (UP) extended shelf-life fluid milk stored at (7.2oC). Ten half-pint, pint, quart and half gallon filled cartons were randomly selected from all UP products available. Samples, pulled at random on day 0, 15, 30, 45, and 60, were plated on Yeast and Mold PetrifilmTM. Forty-seven percent of the UP products stored for 45 days tested positive for mold. Fungal growth was apparent down the side and along the bottom of the 5th panel. Contamination was traced to the presence of yeast and mold spores in paperboard cartons. Pinholes were present in the polyethylene coating and wicking occurred at the unskived 5th panel. Fungi of similar origin and fatty acid profile were isolated from UP milk products and the paperboard cartons.
- Doctoral Dissertations