Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Coyoacán, México.
Foodborne Pathog Dis. 2011 Dec;8(12):1257-61. doi: 10.1089/fpd.2011.0887.
The aim of the current work was to assess the influence of two temperatures, 4°C and 24°C, on pH and water activity and their association with Brucella melitensis survival during the traditional manufacture of ripened goat cheese. Raw milk from a brucellosis-free goat herd was used for the manufacture of ripened cheese. The cheese was inoculated with 5×10(9) of the B. melitensis 16M strain during the tempering stage. The cheeses were matured for 5, 20, and 50 days at both temperatures. To assess Brucella survival, the pH and a(w) were recorded at each stage of the process (curd cutting, draining whey, immersion in brine, ripening I, ripening II, and ripening III). B. melitensis was detected at ripening stage III (1×10(3) colony-forming unit [CFU]/mL) from cheeses matured at 4°C with a pH of 5.0 and a(w) of 0.90, and at a ripening stage II (1×10(4) CFU/mL) from cheeses ripened at 24°C with a pH of 4.0 and a(w) of 0.89. The remaining stages were free from the inoculated pathogen. In addition, viable B. melitensis was recovered in significant amounts (1-2×10(6) CFU/mL) from the whey fractions of both types of cheese ripened at 24°C and 4°C. These results revealed the effects of high temperature (24°C vs. 4°C) on the low pH (4) and a(w) (0.89) that appeared to be associated with the suppression of B. melitensis at the early stages of cheese ripening. In the ripened goat cheeses, B. melitensis survived under a precise combination of temperature during maturation, ripening time, and a(w) in the manufacturing process.
本研究旨在评估 4°C 和 24°C 两种温度对 pH 值和水分活度的影响，及其与传统成熟羊奶干酪制作过程中布鲁氏菌（Brucella melitensis）存活的关系。使用来自无布氏杆菌病羊群的生奶制作成熟奶酪。在调温阶段，将 5×10(9)个布鲁氏菌 16M 菌株接种到奶酪中。在这两种温度下，奶酪分别成熟 5、20 和 50 天。为了评估布鲁氏菌的存活情况，在加工过程的各个阶段（凝乳切割、排乳清、盐水浸泡、成熟 I、成熟 II 和成熟 III）记录 pH 值和 a(w)。在 4°C 成熟的奶酪中，在成熟 III 期（pH 值 5.0 和 a(w) 0.90）检测到布鲁氏菌（1×10(3)CFU/mL），在 24°C 成熟的奶酪中，在成熟 II 期（pH 值 4.0 和 a(w) 0.89）检测到布鲁氏菌（1×10(4)CFU/mL）。其余阶段未检出接种的病原体。此外，在成熟 24°C 和 4°C 的两种奶酪的乳清部分，都回收了大量的存活布鲁氏菌（1-2×10(6)CFU/mL）。这些结果表明，高温（24°C 与 4°C）对低 pH 值（4）和低水分活度（0.89）的影响，似乎与奶酪成熟早期布鲁氏菌的抑制有关。在成熟的羊奶干酪中，布鲁氏菌在成熟过程中的特定温度组合、成熟时间和制造过程中的 a(w)下得以存活。
