Evolution of Lactococcus strains during ripening in Brie cheese using Fourier transform infrared spectroscopy

The diversity of the Lactococcus flora during maturation of soft cheese, pr oduced using one of 2 different starter cultures (S-A and S-B), was determi ned using Fourier transform infrared spectroscopy (FTIR). identification of Lactococcus sp. was achieved using a model composed of the 6 strains of Lc . lactis ssp. lactis and the 2 strains of Lc. lactis ssp. cremoris, present in the starter cultures S-A and S-B, as well as a reference strain for eac h of the subspecies considered. For the cheeses made with the starter cultu re S-A. the proportion of strains within the cheeses was relatively homogen eous throughout maturation, while in the cheeses made with the starter cult ure S-B, one strain predominated. However, with both starters the strains o f Lc. lactis ssp. cremoris failed to develop in the milk culture and in the cheeses. Results demonstrated that FTIR spectroscopy is a rapid and robust method for the qualitative analysis of cheese flora.