Non-starter lactic acid bacteria (NSLAB) are a common component of the microflora of many cheeses and nearly all hard ripened varieties. In a cheese such as Cheddar, they are perhaps the only aspect of the cheese that remains largely uncontrolled.

NSLAB in Cheddar are usually wild strains of Lactobacillus paracasei/Lb. casei that probably gain access to the cheese from the raw milk by surviving pasteurization or from the cheesemaking environment. These organisms grow from very low numbers and typically reach about 10^7-10^8 cfu/g within 2-3 months. They have enzyme systems generally similar to those of Lactococcus and probably contribute to ripening or indeed to the development of off-flavours (research in New Zealand has suggested many flavour defects in Cheddar made under best practice are due to NSLAB). NSLAB are the dominant viable microflora of mature Cheddar cheese. Ripening temperature and, significantly, the rate of cooling of Cheddar blocks after manufacture are major factors which control the growth rate of NSLAB.

Techniques in the literature used to study the contribution of NSLAB to ripening include comparison of raw and pasteurised milk cheeses, microfiltration, use of antibiotics, aseptic cheesemaking and low ripening temperatures.

Further information:

Fox, P.F., P.L.H. McSweeney and C.M. Lynch (1998). Significance of non-starter lactic acid bacteria in Cheddar cheese. Australian Journal of Dairy Technology 53, 83-89.