Isolamento de coliformes, estafilococos e enterococos de leite cru provenientes de tanques de refrigeração por expansão comunitários: identificação, ação lipolítica e proteolítica

Abstract

Isolation and identification of microorganisms in raw milk is interesting from the viewpoint of public health, since, depending on the species isolated, directed actions may be taken to improve milk quality. Milk deterioration is mainly the result of the growth of psychrotrophic microorganisms that produce heat-resistant lipases and proteases which are not denatured during pasteurization, conferring rancid and sour flavors, respectively. Thus, this work aimed at isolating and identifying the main genera of bacteria belonging to the Enterobacteriaceae family, oxidase-positive Gram-negative, Staphylococcus and Enterococcus genera, as well as determining lipase and protease activity in 16 rural farms in Boa Esperança-MG, Brazil. The Gram-negative bacteria were isolated in Eosin Methylene Blue (EMB) and Hektoen Enteric agar media. Staphylococci were isolated in Baird-Parker agar and Enterococcus in KF agar. Colonies of interest were collected and submitted to Gram stain and to catalase and oxidase tests. Following these procedures, the isolates selected were identified using Bactray I, II and III; Api 20 Strep and tests suggested by Bergey´s Manual of Determinative Bacteriology. Sorological identification of Enterococcus was carried out using Prolex. Milk from the 16 rural properties contained strains of fecal microorganisms, such as Escherichia coli and Enterococcus from the Lancefield D group. Oxidase-positive Gram-negative bacteria were identified in five farms. Staphylococcus was found in 10 farms. Milk collected from the farms investigated contained microorganisms that compromise its quality. All the microorganism groups tested showed lipase and protease activities. Keywords: raw milk; bacterial identification; mesophyllic bacteria; lipases; proteases. ResumoO isolamento e a identificação de microrganismos em leite cru se tornam interessantes do ponto de vista de saúde pública, pois dependendo das espécies isoladas, ações direcionadas podem ser tomadas visando a melhoria de sua qualidade. A deterioração do leite é conseqüência sobretudo do crescimento de microrganismos psicrotróficos, que produzem lipases e proteases termoestáveis que não são desnaturadas durante o processo de pasteurização, conferindo sabores e odores rançoso e amargo, respectivamente. Assim, o objetivo deste trabalho foi isolar e identificar os principais gêneros de bactérias pertencentes à família Enterobacteriaceae, Gram- IntroduçãoA natureza complexa e interligada para se obter alimentos e produzi-los de forma segura tem sido amplamente reconhecida. A aproximação integrada para controlar a segurança dos alimentos por toda a cadeia produtiva tem se tornado importante aspecto para se garantir grande número de alimentos seguros. Pensando em segurança, vários países elaboraram e introduziram regulamentações para garantir a segurança do alimento em diferentes estágios na cadeia de produção (VALEEVA et al., 2005). Assim, no Brasil, em 2005, entrou em vigor a Instrução Normativa 51 na qual, dentre vários fatores a serem adotados para a o...

The influence of the climatology of the semi-arid from Alagoas-Brazil on the raw milk microbiota

“…A significant coagulase-positive Staphylococcus count was observed in relation to the maximum temperature of the regions (27 ºC) and bovine thermal discomfort at the time from the third, fourth and fifth collections characterized by the intermediate between the end of the summer season and the beginning of autumn. Other relevance studies about the relation between raw milk microbiota and the climate variation in semiarid areas from Brazil (southeast and northeast from Brazil) have been reported in scientific literature (Catão & Ceballos, 2001;Mendonça et al, 2001;Mendes et al, 2010;Da Silva et al, 2008;Silva et al, 2010;Tebaldi et al, 2008).…”

Action of lactoferrin on the multiplication of Lactobacillus casei in vitro and in Minas fresh cheese

“…The main psychrotrophic bacteria that spoil milk products belong to the genus Pseudomonas (FRANK; CHRISTEN; BULLERMAN, 2005), which produce extracelular proteases and lipases at refrigeration temperatures (ARCURI et al, 2008;TEBALDI et al, 2008). These enzymes are responsible for proteolysis, lipolysis and changes in taste, aroma and color of the cheeses (PERRY, 2004;CANTONI;BERSANI, 2010).…”

“…These results show there was no positive or negative influence of lactoferrin on the growth of L. casei during 28 days in the conditions tested (P>0.05). Several authors have evaluated the multiplication of probiotic microorganisms in the culture medium promoted by LF (GRIFFITHS et al, 2003, KIM et al, 2004RAHMAN et al, 2010;TIAN et al, 2010). Studies on the effect of lactoferrin in cheeses have been carried out aiming to evaluate the antimicrobial activity of this protein (KENJIN, 2002;QUINTIERI et al, 2012), but its ability to promote the multiplication of probiotics has been little studied.…”

Refrigerated raw milk quality of a processing plant in the north of Parana after the implementation of changes imposed by NI 62 of 2011

“…These bacteria are capable of producing thermoresistant extracellular proteases and lipases at refrigeration temperatures (ARCURI et al, 2008;COUSIN, 1982;CRAVEN;MACAULEY, 1992;MUIR, 1996;TEBALDI et al, 2008;VIDAL-MARTINS et al, 2005).…”

“…Thus, the refrigeration process does not ensure the microbiological quality of the milk until it arrives at processing plant, being important a correct handling with good milking practices (GUERREIRO et al, 2005;SILVA et al, 2011;VALLIN et al, 2009;YAMAZI et al, 2010).…”