Nisin preliminary study as a potential preservative for sliced ripened cheese: NaCl, fat and enzymes influence on nisin concentration and its antimicrobial activity

We studied the effect of NaCl, fat and proteolytic enzymes on the concentration in cheese of nisin (RP-HPLC) and its antimicrobial activity (agar-well diffusion with an indicator strain). As a cheese model we used agarose gels containing concentrations of anhydrous milk fat from 5% to 30% (w/w), and NaCl from 0.5% to 2% (w/w). We also studied Emmental cheese. Increasing anhydrous milk fat concentration in agarose gels caused nisin concentration to drop by a factor of 1.6, and also gave rise to a significant decrease in nisin bioactivity. However, increasing NaCl slightly increased nisin bioactivity. The study performed with Emmental indicated that the nisin interacted with the cheese matrix, likely milk fat globules and was not affected by proteases.