Production and stability of nisin in whey protein concentrate

Abstract

The objective of this research was to manufacture nisin-containing whey protein concentrate (WPC) and study its stability during storage. Pasteurized reconstituted (6% w/v) sweet whey powder was used before or after ultrafiltration (UF) as a growth medium for nisin-producing strains of Lactococcus lactis subsp. lactis (ATCC 7962 or BS10). The fermented medium was freeze-dried, stored in polyethylene bags protected from light at 4 °C or 30 °C for 3 months. There was no difference in nisin yields by both strains between the regular and UF whey. Yeast extract supplementation resulted in an increase in nisin activity in UF whey fermented with BS10 and ATCC 7962 from 183 to 167 IU/ml to 1617 and 1667 IU/ml respectively. During storage at 4 °C for 1 month, the freeze dried WPC powder lost 55–60% of the nisin activity. At 30 °C for the same period, a 65–70% reduction in nisin activity was observed. Samples reconstituted at pH 2 and then boiled for 5 min increased nisin activity (P < 0.05). The present study presents WPC as an attractive, clean label ingredient with antimicrobial activities.