Increased Nisin in Cheddar-Type Cheese Prepared with pH Control of the Bulk Starter Culture System

¹ Minnesota-South Dakota Dairy Foods Research Center, Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108

Five strains of Lactococcus lactis ssp. lactis and one transconjugant strain of Lactococcus lactis ssp. cremoris, previously shown to be nisin producers, were evaluated for nisin production during growth in pH-controlled media. Four strains showed increased nisin production in pH-controlled 10% reconstituted skim milk. The transconjugant, L. lactis ssp. cremoris JS102, produced a sixfold increase in nisin,L. lactis ssp. lactis NCDO 1402 and CNRZ 148 showed threefold increases, and nisin increased by fourfold in L. lactis ssp. lactis CNRZ 150. Lactococcus lactis ssp. lactis NCDO 1404 and ATCC 11454 did not show a discernible increase. All strains had three- to fivefold increases of colony-forming units per milliter when grown in pH-controlled media. Five vats of Cheddar cheese were manufactured using a pH-controlled bulk starter system consisting of strains JS102 and NCDO 1404. Approximately 20% more nisin was found in cheese prepared with a pH-controlled bulk starter than in cheese prepared without a pH-controlled bulk starter. The increase in nisin in the cheese could be attributed to higher cell numbers in the pH-controlled bulk starter culture and to carry-over from the inoculum.

Key Words: nisin • lactic acid bacteria • cheese

Submitted on January 19, 1993
Accepted on May 18, 1993