Staphylococcus aureus and Listeria monocytogenes in Norwegian raw milk cheese production

Staphylococcus aureus: Characterisation and Quantitative Growth Description in Milk and Artisanal Raw Milk Cheese Production

“…In raw milk cheeses collected by Jakobsen et al [80], a significant decline in pH values was observed after 5-6 h of fermentation and pH lower than 5.5 was achieved in all samples after 24 h. The highest S. aureus contamination was reached in 5-6 h old samples, in some samples higher than 4 log counts. Nevertheless, none of the sample exceeded counts higher than 5 logs and so it was concluded that S. aureus did not produce enterotoxins.…”

“…An increase in microbial counts in the first 24 h is a normal process in cheese making. This is partly due to the physical retention of microorganisms in the coagulum and also due to the microbial multiplication during coagulation and whey drainage [7,80,81]. In contrast to cheese without the addition Fresco starter, the S. aureus increase in number was about 2.9 log counts and its maximal counts exceeded 6 log CFU/g.…”

“…The variation in the responses of S. aureus to pH value and its dynamic during cheese making process may be attributed to the variations in each dairy farm management of hygiene practices, environmental and personal diversities, process of manufacturing, herd characteristics, multiple sources of S. aureus contamination and geographical distribution of S. aureus strains [20,48,80]. Similarly, many factors are known to influence the SEs production, e.g.…”

“…Besides this, pasteurization eliminates also enzymes and indigenous microflora, which are partly responsible for the development of the typical raw milk cheese flavour and texture [80]. Moreover, the raw milk contains a heat-labile lactoperoxidase system which has inhibitory effect to the growth of some pathogens [79].…”

“…The postpasteurization addition of a starter culture may lead to losses in the unique organoleptic properties of the raw milk cheeses and to end products with uniform sensorial features [81,85,87]. Hence, there is today a renewed interest in traditionally produced raw milk cheeses due to consumer demands for increased varieties of cheese flavours and textures [80]. Consequently, as regards the safety of raw milk cheeses, potential pathogens associated with milk or milk products including Staphylococcus aureus, should still be of interest.…”