RESUMO
This study was carried out to assess the survival of Shiga toxin-producing E. coli (STEC) and atypical enteropathogenic Escherichia coli (aEPEC) during the traditional manufacturing and ripening of Spanish hard cheese from raw cow's milk. Milk samples were spiked with up to 3.1-3.5 log cfu/mL of one strain of STEC (O140:H32 serotype) and one of aEPEC (serotype O25:H2). The first steps of cheesemaking allow for a STEC and aEPEC increase of more than 1 log cfu/mL (up to 4.74 log cfu/g and 4.55 log cfu/g, respectively). After cheese pressing, a steady reduction of both populations was observed, with the STEC strain being more sensitive. The studied pathogenic E. coli populations decreased by 1.32 log cfu/g in STEC and 0.59 log cfu/g in aEPEC in cheese ripened during a minimum period of 60 d. Therefore, a moderate contamination by these diarrhoeagenic E. coli pathotypes, in particular, with aEPEC, on cheese manufactured from raw milk may not be totally controlled through the cheesemaking process and during a maturation of 90 d. These findings remark the importance of improvement in bacteriological quality of raw milk and cross-contamination prevention with diarrhoeagenic E. coli in the dairy industry.
RESUMO
The aim of this work was to use X-ray diffraction to identify substances used for adulteration of raw milk and to determine if crystallographic analysis can detect extraneous substances in milk. Two unknown substances were sent anonymously by employers linked to the dairy chain, who claimed that they were added directly in milk prior to water addition by truck drivers. The samples were analyzed by X-ray diffraction and submitted to physicochemical analysis. The first substance was identified by X-ray diffraction as sodium citrate, complying with its physicochemical attributes, such as the powerful ability to decrease the freezing point. The second substance was identified by X-ray diffraction as sucrose and this result was also in agreement with its ability to increase the density, decrease the freezing point and finally, to be positive for sucrose in the resorcinol qualitative test. To evaluate if X-ray diffraction can detect extraneous substances already mixed in milk, fresh raw milk samples tampered with urea, sodium hydroxide, sodium citrate and sucrose were freeze dried and analyzed by X-ray diffraction, with no detection of any extraneous substances at any percentage. This is the first report of attempted diagnosis of extraneous substances in milk by X-ray diffraction. However, this technique can be useful only when applied to identify substances used for adulteration prior to its dilution in milk, since the amorphous nature of milk seems to be a limitation for the accurate detection of extraneous substances.
Assuntos
Cristalografia por Raios X/veterinária , Contaminação de Alimentos/análise , Leite/química , Animais , Bovinos , Fenômenos Químicos , Citrato de Sódio/análise , Sacarose/análise , Água/análiseRESUMO
Este estudo teve como objetivo comparar a qualidade microbiológica e físico-química de leite cru proveniente de tanques individuais e coletivos, identificar a microbiota psicrotrófica do leite cru refrigerado e verificar o cumprimento da legislação vigente para este alimento. Realizou-se a contagem da microbiota de psicrotróficos, proteolíticos, lipolíticos, aeróbios mesófilos, coliformes totais, E. coli e enterobactérias. A microbiota psicrotrófica foi caracterizada através de testes morfotintoriais. Análises dos teores de gordura, proteína, lactose, sólidos totais, acidez titulável, índice crioscópico e contagem de células somáticas (CCS) também foram realizados. As contagens médias de aeróbios mesófilos não atenderam aos requisitos mínimos de qualidade, já os resultados médios de CCS e os parâmetros físicoquímicos estudados estavam de acordo com a legislação vigente. A contagem de psicrotróficos foi, em média, 90% da contagem total de aeróbios mesófilos, com contagens de psicrotróficos menores que 6 log UFC/ml. Foi encontrada alta porcentagem de proteolíticos e lipolíticos em relação à contagem total de psicrotróficos. Considerando as duas semanas de análise, houve diferença significativa (P>0,05) entre as amostras de leite provenientes de tanques coletivos e individuais somente para coliformes totais e para os teores de proteína e lactose. A microbiota psicrotrófica pred
This study aimed to compare the microbiological and physicochemical quality of raw milk from individual and collective tanks, identify the psychrotrophic microbiota of refrigerated raw milk and verify compliance with current legislation. The enumeration of proteolytic and lipolytic psychrotrophs, as well as, populations of mesophilic aerobes, total coliforms, E. coli and enterobacteria was carried out. The psychrotrophic microbiota was characterized by morpho-tinctorial tests. Determination of fat content, protein, lactose, total solids, titratable acidity, cryoscopic index and somatic cells count (SCC) were also conducted. The average counts of mesophilic aerobes did not met the minimum quality requirements; however, the average results of SCC and the physicochemical parameters were in accordance with Brazilian legislation. The psychrotrophs counts were on average 90% of the total count of mesophilic aerobes, with psychrotrophic population of less than 6 log CFU/ml. A high percentage of proteolytic and lipolytic psychrotrophs in relation to psychrotrophs total counts was found. Considering the two weeks testing, there was a significant difference (P> 0.05) between milk samples from collective and individual tanks only for total coliforms and for protein and lactose contents. Although the predominant psychrotrophic microbiota was Gram negative bacilli, but Gram positive bact
RESUMO
Este estudo teve como objetivo comparar a qualidade microbiológica e físico-química de leite cru proveniente de tanques individuais e coletivos, identificar a microbiota psicrotrófica do leite cru refrigerado e verificar o cumprimento da legislação vigente para este alimento. Realizou-se a contagem da microbiota de psicrotróficos, proteolíticos, lipolíticos, aeróbios mesófilos, coliformes totais, E. coli e enterobactérias. A microbiota psicrotrófica foi caracterizada através de testes morfotintoriais. Análises dos teores de gordura, proteína, lactose, sólidos totais, acidez titulável, índice crioscópico e contagem de células somáticas (CCS) também foram realizados. As contagens médias de aeróbios mesófilos não atenderam aos requisitos mínimos de qualidade, já os resultados médios de CCS e os parâmetros físicoquímicos estudados estavam de acordo com a legislação vigente. A contagem de psicrotróficos foi, em média, 90% da contagem total de aeróbios mesófilos, com contagens de psicrotróficos menores que 6 log UFC/ml. Foi encontrada alta porcentagem de proteolíticos e lipolíticos em relação à contagem total de psicrotróficos. Considerando as duas semanas de análise, houve diferença significativa (P>0,05) entre as amostras de leite provenientes de tanques coletivos e individuais somente para coliformes totais e para os teores de proteína e lactose. A microbiota psicrotrófica pred
This study aimed to compare the microbiological and physicochemical quality of raw milk from individual and collective tanks, identify the psychrotrophic microbiota of refrigerated raw milk and verify compliance with current legislation. The enumeration of proteolytic and lipolytic psychrotrophs, as well as, populations of mesophilic aerobes, total coliforms, E. coli and enterobacteria was carried out. The psychrotrophic microbiota was characterized by morpho-tinctorial tests. Determination of fat content, protein, lactose, total solids, titratable acidity, cryoscopic index and somatic cells count (SCC) were also conducted. The average counts of mesophilic aerobes did not met the minimum quality requirements; however, the average results of SCC and the physicochemical parameters were in accordance with Brazilian legislation. The psychrotrophs counts were on average 90% of the total count of mesophilic aerobes, with psychrotrophic population of less than 6 log CFU/ml. A high percentage of proteolytic and lipolytic psychrotrophs in relation to psychrotrophs total counts was found. Considering the two weeks testing, there was a significant difference (P> 0.05) between milk samples from collective and individual tanks only for total coliforms and for protein and lactose contents. Although the predominant psychrotrophic microbiota was Gram negative bacilli, but Gram positive bact