Microbiological, physico-chemical and proteolytic changes in a Spanish blue cheese during ripening (Valdeón cheese).

The aim of this work was to study the microbiological, physico-chemical and proteolytic changes in Valdeón blue-veined cheese during ripening. Eight replicas of cheese were produced and a total of 48 cheeses were analysed. Lactic acid bacteria, mainly lactococci, were the predominant flora during the early stages of ripening, gradually being replaced by moulds and yeasts (8 log units). Enterococci and Enterobacteriaceae counts were very low or zero. This variety was characterised by a total solids content of 61.80g per 100g(-1) of cheese, a salt/moisture ratio of 8.92g salt per 100g(-1) moisture, a pH of 6.4-7.6 and a water activity of 0.917. At the end of ripening, primary and secondary proteolysis were very high, which resulted in an almost total degradation of αs1- and ß-casein (approximately 90%). The peptide profile of the aqueous soluble extracts at pH 4.6 showed great complexity during ripening.

Effect of autochthonous starter cultures on the biogenic amine content of ewe's milk cheese throughout ripening.

Cheese is among the most commonly implicated foods associated with biogenic amines poisoning. The aim of this study was to evaluate the effects of the type of autochthonous starter culture and ripening time on the concentration of biogenic amines (histamine, tyramine, putrescine, cadaverine, tryptamine, ß-phenylethylamine, spermine and spermidine) in cheeses made from pasteurized ewe's milk. 4 cheese batches were made, in duplicate, and ripened for 7 months. The biogenic amines of 40 cheeses were analysed by high performance liquid chromatography. The predominant biogenic amines determined at the end of the ripening time were phenylethylamine, spermine and tryptamine. Together, these accounted for 81% of the total of biogenic amines studied. The type of starter culture used to make the ewe's cheese had a significant effect (p < 0.001) on the content of biogenic amines throughout ripening time. It was lower in the batches made with an autochthonous starter culture made up entirely of Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris or of the same in combination with Lactobacillus plantarum.