Gregory K. Zerfiridis

Production of Aflatoxins on Inoculated Teleme Cheese

Teleme cheese blocks inoculated with Aspergillus parasiticus were placed in plastic screw-cap containers and held at 5, 16 and 25°C. Three variables were examined at each temperature: (a) cheese without brine, (b) cheese partially immersed in 6% brine and (c) cheese completely immersed in 6% brine. No mold growth appeared at 5°C and no aflatoxins were produced when cheese was kept completely immersed in brine. Aflatoxin was lower in amount at 16 than 25°C and also lower in cheese partially immersed in brine than in cheese without brine. Aflatoxins B1 and G1 appeared to increase during all the incubation time of 7 weeks at 16°C, while at 25°C they reached a maximum in 3 weeks and decreased thereafter. Aflatoxins decreased in the order of G1, B1, G2, B2. After the first week of mold growth, a yellow color appeared in the cheese under mycelium, which color diffused into both the cheese and brine. However, aflatoxins diffused only into the cheese to a depth of not more than 2 cm and the amount decreased as the distance from the surface increased. Although mold growth and yellow color render the cheese unacceptable to the consumer, the best safeguard is to keep the cheese at 5°C or completely immersed in brine.

Contents of Nitrates and Nitrites in some Greek and Imported Cheeses

Fifty-four samples of various types of Greek cheese and 69 samples of imported cheese were analyzed for nitrates and nitrites. Domestic Gruyére from cows milk and processed cheese contained 1-10 and 35-104 mg of NO3- per kg, respectively. All other domestic cheeses were either free of or contained nitrates less than 1 mg/kg. Imported cheese contained nitrates as follows: Edam 1-11, Gouda 1-24, Teleme 13-81. Goudasana 27, processed cheese 0-8, cheese spread 19-30. bacon cheese 24-508 and others <4 mg/kg. All types of domestic and imported cheese were either negative for nitrites or contained <1 mg/kg.

Extracellular protein profile of Bacillus cereus strains

Extracellular protein production by 16 pathogenic and nonpathogenic strains of Bacillus cereus was determined by ion exchange chromatography, isoelectric focusing, and HPLC through a DEAE column. Most of the bands obtained by electrofocusing appeared at pI from 4.70 to 5.30. The profiles could not be related to pathogenicity. With HPLC, 81% of the strains showed three major proteins at retention time between 2.51 and 4.40 min. This feature is speculated to relate the strains to each other and their pathogenicity.