QUANTIFICATION OF FACTORS WHICH INFLUENCE NISINS INHIBITION OF CLOSTRIDIUM-BOTULINUM 56A IN A MODEL FOOD SYSTEM

We modeled nisin's anticlostridial activity and assessed the antagonis tic or potentiating influences of food ingredients. The model systems contained yeast extract, proteose peptone, and glucose; were supplemen ted with protein (0.075, 0.75, 7.5% w/v), phospholipid (0,075, 0.75, 7 .5% w/v), or soluble starch (5, 17.5, 30% w/v); and were adjusted to p H 5.5, 6.0, or 6.5. Samples inoculated with 10(4)/mL spores were incub ated at 15, 25, or 35 degrees C. Statistical analysis developed an equ ation (r(2) = 0.76) that modeled the response and identified temperatu re as the most significant (alpha less than or equal to 0.001) variabl e. Nisin lost effectiveness with increasing temperature. Nisin concent ration had significant positive and phospholipid negative, linear effe cts. Many interactive effects were significant (alpha less than or equ al to 0.20). Nisin inhibited C. botulinum until its residual level dro pped below a threshold, which decreased from 154 IU/mL at 35 degrees C to 12 IU/mL at 15 degrees C.