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

Abstract

The counts, species and characteristics of yeasts were studied throughout the manufacturing and ripening of four batches of Armada cheese, a craft variety made in the north of Spain from raw goat's milk. Counts in Oxytetracycline Glucose Yeast-Extract Agar (1.82 × 104 - 1.15 × 105 cfu·g-1 in milk) 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 decreasing from this point to the end of the ripening process. The yeast percentage of the isolates carried out remained practically constant at around 75 % throughout the ripening process, dropping to 27 % at the last sampling point (16-week-old cheese). Of the 181 isolated yeast strains, 60 were identified as Geotrichum candidum, 58 as Candida lambica, 11 as Candida krusei, 4 as Candida lipolytica, 2 as Candida ingens, 1 as Candida catenulata, 1 as Candida pintolopesii, 1 as Candida colliculosa, 19 as Kluyveromyces lactis, 11 as Kluyveromyces marxianus, 10 as Saccharomyces unisporus and 3 as Trichosporon beigelii. G. candidum predominated in 1-and 2-week-old cheeses 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. Judging from their metabolic characteristics, the yeasts in Armada cheese seem to participate in the initial acidification of the curd and in the consumption of lactic 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, they seem to play an important role in the degradation of the biogenic amines; of the 181 strains identified, 136 assimilated the four biogenic amines tested (cadaverine, histamine, putrescine and tyramine) and all the strains assimilated at least one of these amines. © Inra/Elsevier, Paris.