Ocorrência de leite ácido e de resíduos de antimicrobianos no leite cru entregue em laticínios na região do Vale do Taquari, RS, Brasil = Occurrence of acidity and antimicrobial residues in raw milk delivered at a dairy plant in Vale do Taquari, RS, Brazil / Occurrence of acidity and antimicrobial residues in raw milk delivered at a dairy plant in Vale do Taquari, RS, Brazil

Fava, Luisa Wolker

Background: Milk is considered one of the most important sources of nutrients. It contains proteins, fat acids, vitamins and minerals. Its activity has a significant socio-economic impact in all over the world and in Brazil. The presence of bacterial inhibitors in milk for human consumption is a great concern for the dairy products industry and public health. With regard to the production of dairy products, mainly cheeses and fermented milks, this affects the growth of starter cultures in ripening processes of cheese and fermented milk. The risks for consumer health are represented by allergic reactions, which are usually manifested as urticarias, dermatitides or rhinitis and bronchial asthma, and that can result in anaphylactic shock in susceptible individuals. Another risk to be considered is the consumption by pregnant women of milk containing high levels of antimicrobial residues, considering the teratogenic potential presented by some of them. By the other hand, milk acidity is one of the biggest problems encountered at milk processing plants and, for that reason, the control of the storage temperature of products and the adoption of adequate hygienic practices must be prioritized. The objective of this study was to verify the incidence of acidity and antimicrobial residues in milk, at a dairy factory from Vale do Taquari, RS. Materials, Methods & Results: Data about milk condemnation caused by the presence of antimicrobial residues and acidity were collected from the period of January 1st, 2008 to April 2nd, 2009. The analyses were performed at the quality control laboratory of the dairy plant. The samples came from the milk trucks at the reception platform. The Charm-test® kit was used for detection of antimicrobial residues, and acidity was determined through titration with Dornic solution. Condemnation of acid milk occurred in June, November and December 2008 and in February 2009. On the other hand, condemnation of milk due to the presence of antimicrobial residues occurred in all months studied. Discussion: High temperatures influence in the growth of mesophilic bacteria and impair the maintenance of cooling temperatures. These bacteria cause milk acidification due to the formation of lactic acid from lactose fermentation. The condemnation of acid milk in June 2008, which corresponds to winter time in the south hemisphere, gives evidence that milk acidification is caused by multiple factors, being also associated to the initial microbial load. However, condemnation of milk occurred in November and December 2008, and the largest amount of condemned milk during the whole period of study was observed in February 2009, which highlights the influence of the storage temperature on milk acidification. Condemnation of milk occurred in all months studied due to the presence of antimicrobial residues, which suggests that part of the milk destined to the industry came from animals that were under mastitis treatment or whose grace period, as established by the pharmaceutical companies, was not observed. The results highlight the necessity of specialized technical assistance for producers, in order to prevent the bacterial contamination of milk and the indiscriminate use of veterinary drugs.

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