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, produced using one of 2 different starter cultures (S A and S B ), was determined 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 each of the subspecies considered. For the cheeses made with the starter culture S A , the proportion of strains within the cheeses was relatively homo- geneous throughout maturation, while in the cheeses made with the starter culture S B , one strain predominated. However, with both starters the strains of 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.