A fast micromethod for the estimation of nisin activity in a soft cheese

The British Standard protocol currently used to determine the nisin concentration in cheese requires the manipulation of a 40 g sample involves two critical points, pH adjustment and heating/cooling. In this work, we developed a fast micromethod that permits the manipulation of 0.2 g cheese, substitutes the use of 0.02N HCl by 50 mM citric acid and facilitates the handling of many samples in reduced time, and with increased efficiency/yield. This change keeps the pH stable at ~3.4, enough to sidestep the pH adjustment, and nisin antimicrobial activity was stable at boiling temperatures.