Development of amino acids and organic acids in Norvegia, influence of milk treatment and adjunct Lactobacillus
2001
Interaction between microflora and chemical compounds in Norvegia, a Gouda type cheese, was studied from 4 to 12 weeks of ripening. Norvegia was made from either pasteurised or microfiltered milk, with or without adjunct Lactobacillus, in three experimental blocks. During ripening the cheese made from microfiltered milk had higher non-starter lactic acid bacteria (NSLAB) counts, pH, pyruvate, and alanine content but lower dry matter, lactate, citrulline and tyrosine compared to the cheese made of pasteurised milk. The addition of adjunct lactobacilli resulted in: higher counts of NSLAB, a more rapid decrease of starter bacteria during ripening, lower pH, higher concentration of lactate and arginine but also lower concentration of pyruvate, total amount of free amino acids, gamma-amino butyric acid (GABA) and cysteine. This lower concentration of free amino acids may be explained possibly either by a faster degradation or accumulation of amino acids in cheeses with or without adjunct, respectively. Principal component analysis (PCA) showed that milk treatment was most important for the distribution of the organic acids in fresh cheese, whereas the addition of lactobacilli played a major role in the distribution of organic acids after 12 weeks of ripening. Milk treatment was the most important factor influencing the distribution of individual amino acids. However, partial least-squares regression analysis (PLS2) showed clear correlations between some of the organic acids and amino acids. The results showed that day of production (blocking factor) also played an important role in the biochemical composition of the cheese, especially the concentration of various organic acids and free amino acids.
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