The effect of a protective culture and exclusion of nitrate on the survival of enterohemorrhagic E. coli and Listeria in Edam cheese made from Finnish organic milk

This study compared the chemical composition and hygienic quality of Finnish organic and conventional milk. The composition and quality of milk from 126 Finnish organic and conventional farms from January 2000 to November 2001 were investigated. Finnish organic milk contained significantly less fat, and protein, and had a lower total bacterial count than conventional milk. Organic milk contained significantly more lactose and had a similar, or higher, somatic cell count and a similar, or lower, urea content than conventional milk. Although the differences between organic and conventional milk are rather small, they are of economical significance in large-scale cheese manufacture.This study also determined the effects of the exclusion of nitrate and the introduction of a protective culture on the microbiological safety and the counts of Listeria and non-pathogenic enterohemorrhagic Escherichia coli (EHEC) in organic Edam cheese. Nitrate failed to inhibit the growth of EHEC and Listeria. Thus, compared to Edam cheese from conventional milk, Edam cheese from organic milk without added KNO₃ poses no additional health risk with respect to Listeria and EHEC. The use of a protective culture containing Lactobacillus rhamnosus LC705, however, inhibited the growth of Listeria in Edam cheeses from organic milk.