Role of arginine in the development of secondary microflora in Swiss-type cheese

Abstract

Abstract Microbial growth, lactose fermentation and casein breakdown in Swiss-type cheese was studied in 48 industrial trials. During cheese ripening, the average number of non-starter lactic acid bacteria (NSLAB) increased from 2.2×10 2 up to 1.4×10 7 cfu g −1 . The growth of bacteria was accompanied by the decrease of arginine concentration and formation of ornithine, NH 3 and citrulline. The average ornithine concentration in 3-month-old cheeses was 7.8±1.4 μmol g −1 . As ornithine is not a constituent of casein and some strains of NSLAB are able to convert arginine to ornithine, it was supposed that arginine could be one of the main energy sources for NSLAB in ripening cheese. According to our calculations, ATP available from arginine conversion to ornithine was theoretically sufficient to support the growth of up to 10 8 cfu NSLAB g −1 . This number higher than the maximum NSLAB numbers found in cheese suggested that sufficient amount of arginine was available in cheese. The experimental cfu numbers of NSLAB remained lower obviously due to the competition for available arginine with starter bacteria and the local unavailability of substrates and water. The pH-auxostat studies with the pure culture of Lactobacillus paracasei showed that the growth yield of lactobacilli was not significantly affected at typical cheese ripening temperatures T =7–12°C compared to optimal temperatures.