Lactic acid bacteria isolated from a hand-made blue cheese

Abstract

Nearly 500 strains isolated from different media used to study the aerobic mesophilic and lactic acid flora of Valdeón cheese (a Spanish hand-made blue cheese) have been identified. Nearly 95% of aerobic mesophiles were lactic acid bacteria (LAB). From these, Enterococcus (40·4%) and Lactococcus (42·2%) were the dominant genera, with Lactobacillus (4·1%) and Leuconostoc (5·0%) being also found. The selectivity of the other media used was variable and this is discussed. Several species of Enterococcus were isolated from our samples (Ent. avium, Ent. faecium and Ent. durans), although one was outstanding (Ent. faecalis, 24·7% of the total of strains identified). The dominating LAB species found was Lact. lactis subsp. lactis (31·1%). Other LAB identified were Lact. raffinolactis, Lb. plantarum, Lb. casei, Leuc. mesenteroides subsp. dextranicum, Leuc. mesenteroides subsp. mesenteroides and Leuc. paramesenteroides. The evolution of the lactic-acid flora found during the manufacture and ripening of this variety of cheese showed a pattern marked by the dominance of lactococci and enterococci during the first stages and the substitution of lactococci by lactobacilli and leuconostoc from drying onwards which would be, along with enterococci, the major genera found in the cheese at the stage of consumption. From a technological point of view, the quantitative importance of certain species such as Lact. lactis and Ent. faecalis, as well as the presence of others, i.e. Lb. plantarum and Leuc. mesenteroides, suggest their possible use as starters in the industrial manufacture of this variety.