No abstract

The microbiological air quality at processing areas in a dairy plant was evaluated by using a one-stage air sampler, based on Andersen principles (impaction technique) and by culture settling plate technique, also known as sedimentation technique. Among these areas, milk reception, packaging, and pasteurization rooms were included. Rooms where cheese, yogurt, butter and "doce de leite" (Latin American typical treat made of concentrated milk and sugar) are made were also evaluated. For all processing areas, the numbers of mesophilic aerobic bacteria and yeast and molds recovered by air sampler were higher than 90 CFU•m-3-the maximum value recommended by American Public Health Association (APHA). In four of the six processing areas, the microbial numbers were higher than APHA's standard (30 CFU.cm-2 .week-1) according to culture settling plate technique. The results showed a difference (p<0.05) for the Staphylococcus aureus numbers (from <1.0 to 4.3 UFC•m-3) at processing areas. The numbers of microorganisms recovered by impaction technique were about 2 to 10 times higher than by sedimentation technique. The microorganism group determined at processing areas depended mainly on the technique. By the air sampler technique, it was observed the predominance of yeasts and molds and by sedimentation technique, of mesophilic aerobic bacteria. The increase of temperature at processing areas did not seem to affect the numbers of airborne microorganisms. On the other hand, the increase of air humidity showed a relation with the increase of microorganism numbers. The impaction technique should be chosen since it is better to recover airborne microorganisms, including pathogens.

RESUMOFoi observada a adesão de Bacillus cereus em superfície de aço inoxidável em contato com o leite, segundo o procedimento de limpeza, a sanitização e as propriedades físico-químicas da superfície. O número de B. cereus viáveis, após os procedimentos de higienização, foi afetado pela temperatura, pela concentração das soluções alcalinas e ácidas e pelo pH da solução clorada. A adesão de B. cereus em aço inoxidável não foi termodinamicamente favorável, e ocorreu pouca adesão desse microrganismo, de acordo com os aspectos termodinâmicos da adesão.Palavras-chave: Bacillus cereus, equipamento, indústria do leite, higienização

The efficiency of chemical sanitizing agents to control the microbiota of milk processing areas at a dairy plant was evaluated. Diluted solutions of chlorhexidine digluconate at 1,000 and 2,000 mg.L−1, pH = 5.2 and 5.3, respectively; peracetic acid, at 45 and 75 mg.L−1, pH = 4.2 and 3.8; and a quaternary ammonium compound, pH = 9.2 and 9.3, respectively, were pulverized, at ambient temperature (20–25C) in the milk processing areas using spray equipment which produced a consistent fogging. For each 30 m2 of processing area, 0.5 L of sanitizer solutions were applied at 9 Kgf.cm−2 in 10 min. The sanitizer's efficiency was evaluated against mesophilic aerobic bacteria and yeast and molds. The microbial counts (APC) in the processing areas were detected by impaction technique, as proposed by APHA. Analysis were done before sanitizer application (T0) and after 0.5, 12 and 24 h (T1, T2 and T3), respectively. Activity of 2000 mg.L−1 of chlorhexidine and 700 mg.L−1 of quaternary ammonium against yeast and molds was observed. The T0 number of microorganisms (1.5 and 1.3 log cfu.m−3) decreased in 0.45 and 0.5 log cycle, respectively. Solutions containing 45 mg.L−1 of peracetic acid were effective to control mesophilic aerobic microorganisms. The T0 number of microorganisms (2.1 log cfu.m−3) decreased in 0.55 log cycle. Residual effects against yeasts and molds were observed for 1000 mg.L−1 of chlorhexidine digluconate and 75 mg.L−1 of peracetic acid. Chemical sanitizer applications to control the microbiological quality of the air in milk processing areas is a barrier technology that helps in the production of foods with good microbiological, sensory and organoleptic characteristics.