Antibotulinal Effectiveness of Nisin in Pasteurized Process Cheese Spreads

Pasteurized process cheese spreads were prepared at moisture levels ranging from 52 to 57% with added sodium chloride at levels from 0 to 2.0%, with disodium phosphate levels ranging from 1.4 to 2.5%, and with nisin levels of 0 to 250 ppm. Clostridium botulinum spores were added at a level of approximately 1000 spores per gram of cheese spread except for control batches and one experiment where the spore levels were varied (10-1000 spores/g). The cheese spreads were incubated at 30°C for up to 48 weeks. Nisin is an effective antibotulinal agent in pasteurized process cheese spreads. Addition of nisin allows formulation of pasteurized process cheese spreads with reduced sodium levels (addition of 1.4% disodium phosphate and no added sodium chloride) or slightly higher moisture levels (55-57%) by comparison to typical commercial pasteurized process cheese spreads. Higher levels of nisin (100 and 250 ppm) were required to prevent outgrowth of botulinal spores in cheese spreads with highest moisture levels or most greatly reduced sodium levels. However, in a cheese spread of 52% moisture prepared with 2.5% disodium phosphate but no added sodium chloride, a nisin level of 12.5 ppm was able to prevent completely outgrowth and toxin production by C. botulinum .