| Congresso Brasileiro de Microbiologia 2023 | Resumo: 306-2 | ||||
Resumo:Milk stands out as a nutrient-rich food, making it ideal for the growth of microorganisms, such as spoilage bacteria. Spore-forming bacteria are often associated with technological defects of microbiological origin in UHT milk. However, the detection of this microbial group in the final product using conventional methodologies is time-consuming, making it difficult to correct the industrial problem in a timely manner. Therefore, the development of alternative and rapid methodologies is essential for the success of the dairy industry. In this context, this study aimed to evaluate the detection of Bacillus subtilis ATCC 19659, a spore-forming bacterium, in UHT milk using the blood culture system. The experiments were carried out with the culture of B. subtilis ATCC 19659 activated in Brain Heart Infusion (BHI) broth and incubated at 32°C for 24 hours. The active culture was standardized to an optical density of 0.100 at 600 nm, which corresponded to a population of 107 CFU/mL. To evaluate the interference of stabilizers present in UHT milk in the analysis time, the standardized culture was inoculated into UHT milk samples with and without stabilizers. The samples with and without stabilizers were diluted at concentrations of 1:2, 1:5, and 1:8 (milk:water). Then, these samples were inoculated with B. subtilis ATCC 19659 at concentrations of 101 and 102 CFU/mL. The detection of the bacterium was performed in the blood culture system (alternative methodology), and the verification of the inoculated bacterial population was performed by pour plate method inoculation in BHI agar. In the second stage of the study, the standardized B. subtilis ATCC 19659 cell suspension was inoculated into UHT milk samples with and without stabilizers at different concentrations (100 to 104 CFU/mL). The detection of the inoculated bacterium and the verification of the inoculated population were carried out by the same methodologies described above. The experiments were conducted in duplicate. The presence of stabilizers in UHT milk did not interfere in the detection of B. subtilis ATCC 19659 using the alternative methodology. The results of the second stage demonstrated that the relationship between the detection time of the alternative methodology and the contaminating bacterial population of the UHT milk is linear. The equations of the lines that describe this relationship for UHT milk with and without stabilizers, respectively, were as follow: y =-0.0591x + 0.5219 and y = -0.068x + 0.545, where y is the detection time in hours and x is the inoculated bacterial population in log10 CFU/mL. The detection time of B. subtilis ATCC 19659 by the alternative methodology was approximately 14 hours for the lowest bacterial population tested (100 CFU/mL). This time is much shorter than that required to complete the conventional methodology for UHT milk sterility testing, which can range from 5 to 10 days. Therefore, the results demonstrated that the blood culture system is a rapid and promising methodology for the microbiological analysis of UHT milk. Palavras-chave: Alternative methodology, dairy industry, microbiological stability, spore-forming bacteria, sterility testing Agência de fomento:CAPES, CNPq and FAPEMIG | |||||