Microbiological changes throughout the manufacturing and ripening of a Spanish goat's raw milk cheese (Armada variety)

Abstract

Summary -The microbial groups of technological interest (aerobic mesophilic flora, presumptive lactococci, presumptive lactobacilli, presumptive leuconostocs, presumptive enterococci, presumptive Micrococcaceae and mou Ids and yeasts) were enumerated throughout the ripening process in 4 batches of Armada goat's milk cheese (2 ripened in summer and 2 ripened in autumn). High counts of ail microbial groups were observed in milk (loglO cfu/g: aerobic mesophilic flora 6. presumptive enterococci 2.9~.29,; the highest counts being generally reached in ail the microbial groups in 1-week-old cheese. Beyond this, they progressively dropped until the end of ripening. In the first 8 weeks of ripening, no significant differences were observed in the counts related to the season when the cheeses were ripened. Only in 16-week-old cheeses were the counts in ripened cheeses during the summer lower than those determined in autumn ripened cheeses. The lactic acid bacteria were the most abundant flora during manufacturing and ripening of this cheese. Lactococci (Lactococcus lactis subsp lactis and Lactococcus lactis subsp cremoris) dominated in milk (50% of the isolates carried out in M17 agar), curd (70% of the isolates carried out in M17 agar) and 1-week-old cheese (70% of the isolates carried out in M17 agar) and lactobacilli (mainly Lactobacillus casei subsp casei and Lactobacillus plantarum) were the most abundant group during the last stages of ripening (92.5, 95 and 77.5% of the isolates carried out in Rogosa agar in 4-, 8-and 16-week-old cheese, respectively). M17 agar showed a moderate selectivity for the isolation of lactococci (45.71 % of the isolates carried out in M17 agar were classified as lactococci). The selectivity of MSE agar for the isolation of leuconostoc was very low (only 16.42% of the isolates carried out in MSE agar were c1assified as leuconostocs). On the other hand, Rogosa agar and KAA agar showed a very high selectivity for the isolation of lactobacilli and enterococci, respectively * Correspondence and reprints. fromage Armada / fromage de chèvre / évolution de la flore bactérienne / bactérie lactique Microflora of Armada goat's milk cheeses

Ibores goat's milk cheese: Microbiological and physicochemical changes throughout ripening

“…With respect to the NaCl content, the levels increased gradually to 2.5% by 60 d. Values were also very close to those that have been reported for some other goat's milk cheeses [21,24,33], although usually goat's milk cheeses have high salt levels [16,18,36]. Surprisingly, the present salt content in Ibores cheese is almost 50% 582 M. Mas et al lower than that observed a decade ago for the same type of cheese.…”

“…lactis ssp. lactis as almost the sole representative of the genus Lactococcus is reported frequently for raw milk cheeses [18,19,22,30,33]. It is also in agreement with the observations of Weerkamp et al [35] on the predominance of Lc.…”

“…The scarcity of lactobacilli was initially unexpected because lactobacilli had been detected as the predominant group (nearly 50%) in the previous study of Ibores cheese [22]. This prevalence of lactobacilli had also been found in other goat's milk cheeses [18,33,36], in which, as the ripening progressed, lactobacilli outnumbered lactococci. This probably reflects a combined effect of high salt concentration and low pH, which lactobacilli tolerate better than lactococci [2].…”

“…In other types of goat's milk cheeses, the total solid content is very variable, possibly due to the very different cheesemaking methods used [6,18,24,33]. Even in the case of the Ibores cheeses analysed some years ago [23], the total solid content was much higher (65.4% at 60 d of ripening), possibly because the ripening was not performed at a controlled temperature, whereas at present it is.…”

“…Although other Spanish goat's milk cheeses have been extensively studied (Majorero cheese [6], Gredos cheese [24], Armada cheese [33], Tenerife cheese [36]), there have only been some preliminary studies of Ibores cheese [22,23]. Moreover, recent modifications of some aspects of Ibores cheese production, the improvement of hygiene, and more controlled ripening conditions, suggested to us that the microbiological and physicochemical characteristics could be quite different to those a decade ago.…”