Assessment of microbiological and physicochemical quality of raw milk sold informally through social media

This study evaluated the quality of raw milk sold informally in Cuiabá, Mato Grosso, Brazil, focusing on the ease of acquisition via social media and the association of this practice with fraud and serious quality issues. Eighty liters of raw milk were acquired from four distinct producers via social media, totaling 40 samples. The analyses revealed high microbiological contamination, with elevated counts of aerobic mesophilic bacteria (8.63 log₁₀ colony-forming units [CFU]/mL), Enterobacteriaceae (7.71 log₁₀ CFU/mL), total coliforms (4.15 log₁₀ most probable number [MPN]/mL), thermotolerant coliforms (3.34 log₁₀ MPN/mL), Escherichia coli (3.57 log₁₀ MPN/mL), and psychrotrophic bacteria (4.41 log₁₀ CFU/mL). Salmonella spp. was not detected. Physicochemical analyses indicated non-compliance with parameters for fat (15%), protein (20%), lactose (15%), solids non-fat (47.5%), total solids (20%), density (20%), the cryoscopic index (82.5%), and Dornic acidity (60%). Additionally, 70% of the samples exhibited instability in the alcohol-alizarin test, with a pH ranging from 5.58 to 6.12. We identified several frauds-the addition of water, sucrose, hydrogen peroxide, and antimicrobial residues-underscoring the severity of informal trade. Additionally, as part of this study, we investigated the antimicrobial efficacy of different disinfectants commonly used or suggested for sanitation in milk production environments. Among the five disinfectants tested, 2.5% sodium hypochlorite demonstrated the highest antimicrobial efficacy, followed by 3% hydrogen peroxide and benzalkonium chloride. Iodophor at 0.4% and sodium hypochlorite diluted according to the manufacturer’s recommendations did not show a significant effect. The results highlight the poor microbiological and physicochemical quality of informally traded raw milk in this region of Brazil, with contamination and fraud posing a substantial sanitary risk to consumers. The results strongly advocate for more rigorous oversight and greater public understanding regarding the risks associated with consuming uninspected milk.

Key-words:
hygiene; food microbiology; food fraud; public health; coliforms; bovine milk