Estimation of nisin in foods

Abstract

Abstract Methods for the estimation of nisin in solution and in foods are described and the nisin unit is redefined. The presence of interfering substances in certain food extracts has been demonstrated. In the foods examined compensation for the effect on the plate assay could be made by inactivating the nisin by an alkali treatment, and using these treated extracts as a basis for controls. For quantitative determination of suspensions of nisin alone and in food extracts, a large plate diffusion method requiring no prediffusion and using M. flavus as test organism is described. For semi‐quantitative estimations, or for sorting purposes, a simple reverse‐phase disk assay technique based on B. stearothermophilus spores, with overnight incubation at 55°, is proposed.