Nisin activity is usually quantified using agar diffusion methods. The assay sensitivity (increase in zone size/increase in nisin concentration) for nisin was greatly increased by using Lactobacillus sake ATCC 15521 as the indicator organism, rather than Micrococcus luteus ATCC 10420, the previous indicator organism of choice.

We modeled nisin's anticlostridial activity and assessed the antagonistic or potentiating influences of food ingredients. The model systems contained yeast extract, proteose peptone, and ,glucose; were supplemented 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 pH 5.5, 6.0, or 6.5. Samples inoculated with 104/mL spores were incubated at 15, 25, or 35°C. Statistical analysis developed an equation (r* = 0.76) that modeled the response and identified temperature as the most significant (a s 0.001) variable. Nisin lost effectiveness with increasing temperature. Nisin concentration had significant positive and phospholipid negative, linear effects. Many interactive effects were significant (a < 0.20). Nisin inhibited C. botulinurn until its residual level dropped below a threshold, which decreased from 154 IU/mL at 35°C to 12 IU/mL at 15°C.