Characterization of biochemical changes during ripening in Argentinean sheep cheeses.

BERGAMINI, C.; WOLF I. V.; PEROTTI, M.C.; ZALAZAR, C.A.

JOURNAL OF SMALL RUMINANT RESEARCH

ELSEVIER SCIENCE BV

Año: 2010 p. 79 - 89

0921-4488

In recent years, there has been an increase in the production of sheep milk in our country,which has been used mainly in cheese-making. This production, however, is not wellstandardised, as there are neither defined protocols nor well-characterised products forthis procedure. Previously, different methodologies for making two types of sheep cheeseswere developed at our institute. In the present work, the levels of free amino acids, organicacids, free fatty acids and volatile compounds for these sheep cheeses were studied in orderto thoroughly characterise them. Therefore, we have produced two types of cheeses: oneusing a starter of Streptococcus thermophilus, in which the curd was cut into 5-mm pieces,washed and then heated to 43 ºC (S cheeses); the other one using a mixed starter composedof S. thermophilus, Lactobacillus helveticus and Lactobacillus bulgaricus, in which the curd wascut into smaller pieces, was not washed and was heated to 47 ºC (L cheeses). These cheeseswere analysed at 2 and 180 days of ripening. Free amino acids (FAAs) and organic acids werestudied by HPLC, free fatty acids (FFAs) were quantified by GC and volatile compounds wereanalysed by SPME-GC-FID/MS. The concentrations of all FAAs were significantly higher inthe L cheeses than in the S cheeses, and this was evident from the beginning of the ripening.Both types of cheeses showed similar changes in the concentrations of some FAAs duringripening, but S cheeses were characterised by higher percentages of Phe, Leu and Val, whileL cheeses had higher percentages of Pro, Ile, His and Asp. Lactic and citric acid were themost important organic acids present in both types of cheeses. At the end of the ripening,L cheeses presented higher levels of succinic and formic acids, while S cheeses showeda much higher amount of acetic acid. The levels of FFAs increased during ripening, andmyristic, palmitic, stearic and oleic acids were the most abundant ones in both types ofcheeses. L cheeses showed significantly higher levels of all FFAs at the end of the ripeningand presented a greater increase in the percentages of short-chain fatty acids duringripening compared to S cheeses. Regarding volatile compounds, higher levels of aldehydesand ketones characterised the L cheeses, whereas S cheeses had higher proportions ofesters and alcohols. Both types of cheeses presented similar areas in the most compoundsof acids group, but the levels of butanoic and hexanoic acids were significantly higher in Scheeses than in L cheeses. The results of the present work offer an important contributionto this field: they have provided a better understanding of the changes that occur duringthe ripening of the two sheep cheeses manufactured with technologies developed in ourgroup. These technologies could also be used by small sheep farm producers located in ourregion with the aim of increasing the economic yield of their products.