Study of the yeasts during the ripening process of Armada cheeses from rawgoat's milk

The counts, species and characteristics of yeasts were studied throughout t he manufacturing and ripening of four batches of Armada cheese, a craft var iety made in the north of Spain from raw goat's milk. Counts in Oxytetracyc line Glucose Yeast-Extract Agar (1.82 x 10(4) - 1.15 x 10(5) cfu.g(-1) in m ilk) increased one log. unit in curd and another log. unit during the first week of ripening, remaining stable in two- and four-week-old cheeses and d ecreasing from this point to the end of the ripening process. The yeast per centage of the isolates carried out remained practically constant at around 75 % throughout the ripening process, dropping to 27 % at the last samplin g point (16-week-old cheese). Of the 181 isolated yeast strains, 60 were id entified as Geotrichum candidum, 58 as Candida lambica, 11 as Candida kruse i, 4 as Candida lipolytica, 2 as Candida ingens, 1 as Candida catenulata, 1 as Candida pintolopesii, 1 as Candida colliculosa, 19 as Kluyveromyces lac tis, 11 as Kluyveromyces marxianus, 10 as Saccharomyces unisporus and 3 as Trichosporon beigelii. G. candidum predominated in 1- and 2-week-old cheese s and C. lambica was the most abundant species in milk and in 4- and 8-week -old cheese while C. krusei dominated in 16-week-old cheese, Juding from th eir metabolic characteristics, the yeasts in Armada cheese seem to particip ate in the initial acidification of the curd and in the consumption of lact ic acid which takes place throughout the ripening process, though, with the exception of G. candidum, they do not seem to play a relevant role in the lipolysis, either way its resistance to NaCl is not very high. However, the y seem to play an important role in the degradation of the biogenic amines; of the 181 strains identified, 136 assimilated the four biogenic amines te sted (cadaverine, histamine, putrescine and tyramine) and all the strains a ssimilated at least one of these amines. (C) Inra/Elsevier, Paris.