Effects of the addition of Enterococcus faecalis in Cebreiro cheese manufacture

Abstract

Ten batches of Cebreiro, a fresh or short-ripened acid-curd cheese, produced in the Galician mountains (NW Spain) were prepared from pasteurized milk inoculated with microorganisms isolated from raw-milk cheese. Two control batches were made with a Lactococcus lactis subsp. lactis starter; 8 batches were made with the lactococcal starter plus one of eight Enterococcus faecalis cultures: 4 E. faecalis var. liquefaciens (EFLB) and 4 E. faecalis var. faecalis (EFFB). Whey dry matter in the EFLB was notably higher than in the control batches and this was related to lower cheese yields. After over 15 days storage the highest counts of both aerobic bacteria and lactic acid bacteria were observed for the EFLB. The lower content in protein on dry matter was found in the EFLB. The β-casein broke down to a greater extent in the EFLB than in the EFFB, the lowest values being obtained for the control batches. The higher level of hydrolysis of α s1-casein and maximum peptide α s1−I/α s1-casein ratio were obtained for EFFB at day 15 of storage. In all the batches made with enterococci soluble nitrogen was higher than in the control batches, with the highest values in the EFLB. In all the batches made with enterococci, volatile free fatty acid, long-chain free fatty acids and diacetyl and acetoin contents at days 10 and 15 of storage were higher than in the control batches, the highest values being obtained for EFLB. Acetic acid in all batches accounted for the main proportion of the volatile free fatty acids. Butyric and caproic acids were not detected in the volatile free fatty acids fractions of the control batches, but both acids were detected in most of the batches made with enterococci. The more intense acid taste was found in the EFFB and control batches, the most bitter taste being found in the EFLB. Buttery, rancid and spicy flavors were more evident in the EFLB. The rancid and spicy flavors were positively correlated with the contents of volatile free fatty acids and long-chain free fatty acids. The cheeses of EFLB proved to be more crumbly than the EFFB, whereas the stickiness and deformability were higher in the EFFB. The batches with similar organoleptic characteristics to those of traditional cheese were the batch IV made with the less proteolytic strain of E. faecalis var. liquefaciens, and the batch VI made with a moderate lipolytic activity strain of E. faecalis var. faecalis.