Inactivation of Salmonella Enteritidis on cherry tomatoes by ultrasound, lactic acid, detergent, and silver nanoparticles.

Ultrasound (US) combined with chemical agents could represent an effective method for decontaminating fruits and vegetables. This study aimed to evaluate the use of US (40 kHz for 5 min) alone or with 1% lactic acid (LA), 1% commercial detergent (DET), or 6 mg/L silver nanoparticles (AgNP, average diameter 100 nm) as an alternative treatment to 200 mg/L sodium dichloroisocyanurate for inactivating Salmonella enterica serovar Enteritidis present on cherry tomatoes. The interfacial tension between sanitizing solutions and bacterial adhesion was investigated. Sanitizers in solutions with DET and AgNP had lower surface tension. All treatments, except that with DET, reduced Salmonella Enteritidis by more than one logarithmic cycle. There was no significant difference between the mean values of log colony-forming units (CFU)/g reduction in all treatments. Transmission electron microscopy revealed the loss of the Salmonella Enteritidis capsule following treatment with US and with US + LA. Salmonella Enteritidis counts (2.29 log CFU/g) in cherry tomatoes were markedly reduced to safe levels by treatment with the combination of AgNP and US + LA (2.37 log CFU/g).

Subinhibitory concentrations of silver nanoparticles and silver nitrate on the adaptative and cross-resistance to antibiotics on bovine mastitis pathogens / Concentrações subinibitórias de nanopartículas de prata e nitrato de prata na resistência adaptativa e cruzada com antibióticos em patógenos de mastite bovina

ABSTRACT: Biocides and/or antibiotics used in subinhibitory concentrations can promote the development of adaptive resistance or even cross-resistance in microorganisms. However, studies on these responses following silver treatments are scarce in the literature. Silver-based compounds, including silver nanoparticles (Ag-NPs), can be an alternative in the prevention and treatment of bovine mastitis. Thus, this research evaluated the effect of subinhibitory dosages of Ag-NPs and Ag+ ions from silver nitrate (AgNO3) on Staphylococcus aureus and Escherichia coli isolated from milk of cows with mastitis. Ag-NPs were synthesized by chemical reduction using AgNO3 and sodium citrate and the minimum inhibitory concentration (MIC) of Ag-NPs and Ag+ ions on the mastitis pathogens were determined. Isolates were exposed to subinhibitory concentrations of Ag-NPs or AgNO3 for 10 consecutive days to verify the development of adaptive resistance evaluated by changes in the MIC values. The development of cross-resistance with antibiotics was also studied, being verified by comparing the sensitivity profile of treated cells with non-treated cells. AgNO3 was more effective against all isolates. There was no change in the MIC values or in the antibiotic sensitivity profile for both bacteria following consecutive exposure to subinhibitory dosages of Ag-NPs or AgNO3, indicating that silver was not able to select adaptive resistance or cross resistance to the tested antibiotics. The potential of silver presented by these results is favorable to the continuity of studies aiming to elaborate silver-based therapies for the treatment of bovine mastitis.

RESUMO: Biocidas e/ou antibióticos em concentrações sub-inibitórias podem promover o desenvolvimento de resistência adaptativa ou mesmo resistência cruzada nos micro-organismos. Entretanto, estudos destas respostas após o tratamento com a prata são escassos na literatura. Compostos a base de prata, incluindo as nanopartículas de prata (Ag-NPs), podem ser uma alternativa na prevenção e/ou tratamento de mastite bovina. Assim, este trabalho objetivou determinar o efeito de doses sub-inibitórias de Ag-NPs e dos íons Ag+ provenientes do nitrato de prata (AgNO3) sobre isolados de Staphylococcus aureus e de Escherichia coli, provenientes de leite de vacas com mastite. As Ag-NPs foram sintetizadas por redução química utilizando AgNO3 e citrato de sódio e a Concentração Mínima Inibitória (CMI) das Ag-NPs e íons Ag+ nos patógenos da mastite foi determinada. Os isolados foram expostos a concentrações sub-inibitórias de Ag-NPs ou de AgNO3 por 10 dias consecutivos para verificar o desenvolvimento de resistência adaptativa à prata pela mudança no valor da CMI, e de resistência cruzada com antibióticos pela mudança no perfil de sensibilidade em relação ao controle. AgNO3 apresentou-se mais efetivo contra todos os isolados. Não foi verificada alteração no valor da CMI nem do perfil de sensibilidade aos antibióticos, indicando que não houve seleção de resistência adaptativa à prata e de resistência cruzada aos antibióticos pelos micro-organismos estudados. O uso potencial da prata apresentado nos resultados é favorável à continuidade dos estudos objetivando a elaboração de terapias à base de prata para o tratamento da mastite bovina.

Phenolic extract of Eugenia uniflora L. and furanone reduce biofilm formation by Serratia liquefaciens and increase its susceptibility to antimicrobials.

Serratia liquefaciens is a spoilage microorganism of relevance in the dairy industry because it is psychrotrophic, able to form biofilm, and produces thermoresistant proteases and lipases. Phenolic compounds and furanones have been studied as inhibitors of biofilm formation. In this study, the potential of the pulp phenolic extract of Eugenia uniflora L. orange fruits, also called pitanga, and furanone C30 on the inhibition of biofilm formation by S. liquefaciens L53 and the susceptibility to different antimicrobials were evaluated. The pulp phenolic extract of pitanga had a high total phenolic content, being mainly composed of glycosylated quercetins and ellagitannins. Sub-inhibitory concentrations of this extract and furanone reduced biofilm formation by S. liquefaciens on polystyrene and the amount of polysaccharides, proteins and extracellular DNA in the biofilms. These biofilms were also more susceptible to kanamycin. The combinations of furanone with phenolic extract of pitanga or kanamycin showed a synergistic effect with total growth inhibition of S. liquefaciens.

Determinação do pH mínimo de crescimento de Listeria monocytogenes frente a diferentes ácidos orgânicos / Determination of the minimum pH growth of Listeria monocytogenes front of different organic acids

Os ácidos orgânicos são empregados no processamento de alimentos para retardar a multiplicação microbiana. O objetivo foi determinar o pH mínimo de crescimento de Listeria monocytogenes, mediante ao uso dos ácidos lático, acético e cítrico. Para determinar o pH mínimo de crescimento de L. monocytogenes em meio de cultura, frente aos diferentes ácidos orgânicos, foi utilizado caldo Brain Heart Infusion (BHI), que teve o pH ajustado para valo res de 4,0 a 6,0, em um intervalo de 0,2. O crescimento de L. monocytogenes, em diferentes valores de pH, foi monitorado pela medida da Densidade Óptica a 600 nm. Os ensaios foram realizados a 35 ºC, durante 7 dias. As taxas de crescimento foram ajustadas ao modelo de raiz quadrada, sendo um modelo para cada antimicrobiano estudado. Observou-se que o menor valor de pH mínimo para o crescimento de L. monocytogenes ocorreu ao ser empregado o ácido cítrico e o maior valor, ao ser empregado o ácido acético.

Avaliação da capacidade de formação de biofilmes de Bacillus cereus isolados de produtos lácteos frente a diferentes temperaturas / Evaluation of the capacity to form biofilm by Bacillus cereus isolated from dairy products at different temperatures

Bacillus cereus encontra-se entre os patógenos de maior preocupação na indústria de alimentos por sua capacidade em formar biofilmes. Como resultado, podem contaminar os alimentos que entram em contato com as superfícies, representando dessa forma um obstáculo para conservação de leite e produtos lácteos, o que coloca em risco a saúde dos consumidores. Objetivou-se avaliar a capacidade de formação de biofilmes de estirpes de B. cereus frente à diferentes temperaturas encontradas na indústria de laticínios em superfície de aço inoxidável. A capacidade de formação de biofilme foi avaliada em diferentes temperaturas (5, 15, 25 e 32 ºC) e intervalos de tempo (24, 48,72, 96 e 120h). As estirpes de B. cereus apresentaram diferenças significativas nas temperaturas avaliadas e na capacidade de adesão, onde uma das estirpes apresentou maior capacidade de se aderir. Constatou-se que altas temperaturas favoreceram o desenvolvimento do biofilme e baixas temperaturas retardaram esse processo.

Physical and chemical quality, biodiversity, and thermodynamic prediction of adhesion of bacterial isolates from a water purification system: a case study

ABSTRACT The objective of this study was to evaluate the quality of water purification system and identify the bacteria this system, predict bacterial adherence according to the hydrophobicity of these microorganisms and of the polypropylene distribution loop for purified water. The assessment of drinking water that supplies the purification system allowed good-quality physical, chemical, and microbiological specifications. The physicochemical specifications of the distributed purified water were approved, but the heterotrophic bacteria count was higher than allowed (>2 log CFU mL-1).The sanitation of the storage tank with chlorine decreased the number of bacteria adhered to the surface (4.34 cycles log). By sequencing of the 16SrDNA genes, six species of bacteria were identified. The contact angle was determined and polypropylene surface and all bacteria were considered to be hydrophilic, and adhesion was thermodynamically unfavorable. This case study showed the importance of monitoring the water quality in the purified water systems and the importance of sanitization with chemical agents. The count of heterotrophic bacteria on the polypropylene surface was consistent with the predicted thermodynamics results because the number of adhered cells reached approximate values of 5 log CFU cm-2.

Polydiacetylene/triblock copolymer nanoblend applied as a sensor for micellar casein: A thermodynamic approach.

Polydiacetylene (PDA) and triblock copolymer nanoblends were synthesized to detect micellar casein (MC), the main milk protein and an indicator of milk quality. UV-Vis spectrum showed that MC induced blue-to-red transition in nanoblends. When nanoblends and MC were separated by dialysis membrane colorimetric response (CR) was similar, whereas a remarkable CR reduction was noticed after addition of dialyzed-MC, suggesting that small molecules present in MC (salts) caused PDA color change. Interaction enthalpy variation between nanoblends and MC showed an abrupt increase that coincided with MC concentration when colorimetric transition occurred. Copolymer hydrophobic/hydrophilic balance and presence of other molecules in the system affected nanoblends CR. MC salts were found to interact with nanoblends leading to color changes. MC concentration, MC salt release, copolymer hydrophobic/hydrophilic balance, and presence of other molecules in the system affected responses of the sensors. These results contribute to future applications of PDA/copolymer nanosensors to dairy models.

Nanotechnology in the food industry / Nanotecnologia na indústria de alimentos

Nanotechnologies involve the manipulation of matter at a very small scale, generally between 1 and 100 nanometers. They exploit novel properties and functions that occur in matter at this scale. The application of nanotechnology in the areas of food and food packaging is growing rapidly, and in the area of food security, these applications include the detection of microorganisms, environmental protection, water purification, encapsulation of nutrients and food packing. Nanotechnology is opening up a world of new possibilities for the food industry, but the entry of nanoparticles into the food chain can result in a buildup of toxic contaminants in food and harm human health. This review focuses on the nanoencapsulation of bioactive compounds, nanosensor especially to detect foodborne pathogens, applications of nanotechnology in food packing and highlight some of aspects of toxicology.

A nanotecnologia envolve a manipulação da matéria em uma escala muito pequena, geralmente entre 1 e 100 nanômetros. Ela explora novas propriedades e funções que ocorrem na matéria nesta escala nanometrica. A aplicação da nanotecnologia nas áreas de alimentos, embalagens para alimentos e segurança alimentar têm crescido rapidamente. Estas aplicações incluem a detecção de microrganismos, proteção ambiental, purificação de água, encapsulamento de nutrientes e embalagem para alimentos. A nanotecnologia está abrindo novas possibilidades para a indústria de alimentos, mas, a entrada de nanopartículas na cadeia alimentar pode resultar em um acúmulo de contaminantes que podem ser tóxicos e prejudicar a saúde humana. Esta revisão enfoca a nanoencapsulação de compostos bioativos, nanosensores, especialmente para detecção de patógenos em alimentos, aplicação da nanotecnologia na área de embalagens para alimentos e destaca alguns aspectos sobre toxicologia.

Microbiological aspects of the biofilm on wooden utensils used to make a Brazilian artisanal cheese.

The artisanal Minas cheese is produced from raw cow's milk and wooden utensils were employed in its manufacture, which were replaced by other materials at the request of local laws. This substitution caused changes in the traditional characteristics of cheese. Due to the absence of scientific studies indicating the microbial composition of biofilms formed on wooden forms, tables and shelves used in these cheese production, the present work evaluated the counts of Staphylococcus aureus, Escherichia coli, coliforms at 32 °C, yeasts, presumptive mesophilic Lactobacillus spp. and Lactococcus spp. in these biofilms, milk, whey endogenous culture and ripened cheese in two traditional regions: Serro and Serra da Canastra. Also, we checked for the presence of Salmonella sp. and Listeria monocytogenes in the ripened cheeses. The ultra structure of the biofilms was also assessed. Counts above legislation (> 2 log cfu/mL) for the pathogens evaluated were found in milk samples from both regions. Only one shelf and one form from Serro were above limits proposed (5 cfu/cm(2) for S. aureus and E. coli and 25 cfu/cm(2) for coliforms) in this study for contaminants evaluated. In Canastra, few utensils presented safe counting of pathogens. There was no Salmonella sp. and Listeria monocytogenes in the cheeses after ripening. Thus, the quality of the cheese is related to improving the microbiological quality of milk, implementation and maintenance of good manufacturing practices, correct cleaning of wooden utensils, and not its replacement.

Removal of Salmonella enterica Enteritidis and Escherichia coli from green peppers and melons by ultrasound and organic acids.

The aim of this study was to evaluate the effectiveness of ultrasound treatment combined with organic acids in the decontamination step for green peppers and melons. The influence of the surface roughness of the peppers and melons on bacterial adhesion was evaluated, as measured using a profilometer. The adhesion of Salmonella enterica serovar Enteritidis and Escherichia coli to the green pepper and melon surfaces was also evaluated by measuring the hydrophobicity of the microorganisms and the surfaces. The bacteria that adhered to the surface of green peppers and melons was quantified by plate count and visualized by scanning electron microscopy. In addition, the efficiency of ultrasound and organic acids to remove bacteria from the pepper and melon surfaces was examined. The average roughness (Ra) of the green peppers (13.0±2.7 nm) was significantly different (p>0.05) from the melons (33.5±7.9 nm). Adherence of S. Enteritidis and E. coli are thermodynamically unfavorable for both surfaces studied (∆G(adhesion)>0). Despite these data, good adhesion occurred on both surfaces. The number of bacteria on green pepper slices was 7.3 and 7.0 log CFU/cm(2) for E. coli and S. enterica Enteritidis, respectively. For melon surfaces, the number of bacteria was 7.0 and 6.9 log CFU/cm(2) for E. coli and S. Enteritidis, respectively. The greater adherence of both bacteria on the green peppers can be explained by its hydrophobic surface; the hydrophilic surfaces of melons resulted in lower adherence. These results suggest that the adhesion observed in this experiment is a multifactorial process. Among the treatments evaluated for green peppers, a higher removal of pathogens was observed after use of a combination of ultrasound and 1% lactic acid; this treatment reduced E. coli and Salmonella by 2.9 and 2.8 log CFU/cm(2), respectively. For melons, the combination of ultrasound and lactic acid showed a reduction of 2.5 and 3.1 log CFU/cm(2) for E. coli and S. Enteritidis, respectively. These results indicate that it is possible to replace the chlorinated compounds that are commonly used to sanitize fruits and vegetables. These results confirm that ultrasound, an emerging technology for food processing applications, could enhance the microbial safety of fresh produce.

Microbiological aspects of the biofilm on wooden utensils used to make a Brazilian artisanal cheese

The artisanal Minas cheese is produced from raw cow's milk and wooden utensils were employed in its manufacture, which were replaced by other materials at the request of local laws. This substitution caused changes in the traditional characteristics of cheese. Due to the absence of scientific studies indicating the microbial composition of biofilms formed on wooden forms, tables and shelves used in these cheese production, the present work evaluated the counts of Staphylococcus aureus, Escherichia coli, coliforms at 32 °C, yeasts, presumptive mesophilic Lactobacillus spp. and Lactococcus spp. in these biofilms, milk, whey endogenous culture and ripened cheese in two traditional regions: Serro and Serra da Canastra. Also, we checked for the presence of Salmonella sp. and Listeria monocytogenes in the ripened cheeses. The ultra structure of the biofilms was also assessed. Counts above legislation (> 2 log cfu/mL) for the pathogens evaluated were found in milk samples from both regions. Only one shelf and one form from Serro were above limits proposed (5 cfu/cm² for S. aureus and E. coli and 25 cfu/cm² for coliforms) in this study for contaminants evaluated. In Canastra, few utensils presented safe counting of pathogens. There was no Salmonella sp. and Listeria monocytogenes in the cheeses after ripening. Thus, the quality of the cheese is related to improving the microbiological quality of milk, implementation and maintenance of good manufacturing practices, correct cleaning of wooden utensils, and not its replacement.

Ocorrência do gene da toxina da síndrome do choque tóxico em Staphylococcus spp. isolados de leite de vacas com mastite e de leite cru refrigerado / Occurrence of the toxic shock syndrome toxin gene in Staphylococcus spp.isolated from bovine mastitis milk and refrigerated raw milk

Avaliou-se a presença do gene (tst-1) para Toxina da Síndrome do Choque Tóxico-1 (TSST-1), utilizando-se a técnica de Reaçãoem Cadeia da Polimerase (PCR) em um total de 264 Staphylococcus spp. isolados de leite. Desses, 221 eram Staphylococcusaureus, 33 Staphylococcus coagulase negativo (SCN) e 10 Staphylococcus coagulase positivo (SCP). As amostras eram oriundasde vacas com mastite (n=96) e de leite cru refrigerado (n=168), coletadas de 46 e 22 propriedades, respectivamente. As amostrasforam coletadas de rebanhos localizados em diferentes regiões dos Estados de Minas Gerais e Rio de Janeiro. Observou-seproduto de amplificação (250 pares de base-pb) na reação de PCR para tst-1 em sete amostras (2,6%), sendo todas as estirpesidentificadas como Staphylococcus aureus isoladas de leite cru refrigerado. Embora a detecção do gene não indique a produçãoda toxina, o monitoramento de estirpes bacterianas potencialmente produtoras torna-se importante como forma de realizar umlevantamento epidemiológico e controle dos rebanhos leiteiros brasileiros, uma vez que esse gene está associado aos elementosgenéticos móveis, representando um risco à possível transferência horizontal de genes para outras bactérias. Além disso, a presençadesses genes tem sido associada à presença de genes para enterotoxinas estafilocócicas, o que pode implicar o aumento dapatogenicidade dos isolados bacterianos e um potencial risco à saúde pública.

Was evaluated the presence of the gene (tst -1) for toxic shock syndrome toxin - 1 (TSST -1), using the technique of PolymeraseChain Reaction (PCR) on a total of 264 Staphylococcus spp. isolated from milk. Of these, 221 were Staphylococcus aureus, 33Staphylococcus coagulase negative (SCN) and 10 Staphylococcus coagulase positive (SCP). The samples were from cows withmastitis (n=96) and refrigerated raw milk (n=168), collected from 46 and 22 dairy herds, respectively. Samples were collectedfrom herds located in different regions of Minas Gerais and Rio de Janeiro States. Was observed PCR amplification of the tst-1gene (250 base pairs-bp) in seven (2.6 %) samples, and all strains of Staphylococcus aureus isolated from refrigerated raw milk.Although its detection in isolated does not mean that it will be expressed, monitoring of bacterial strains producing potentiallybecomes important as performing an epidemiological survey and control of Brazilian dairy herds, since this gene is associatedwith mobile genetic elements, representing a risk to possible horizontal gene transfer to other bacteria. Furthermore, the presenceof these genes have been associated with the presence of genes for enterotoxins, which may result in increased pathogenicity ofthe isolates and a potential risk to public health.

Modification of polysulfone membrane used in the water filtration process to reduce biofouling.

Polysulfone membranes (PSF) were modified with silver nanoparticles obtained by new synthesis (nAgNS), silver nanoparticles obtained commercially (nAgC), silver sulfadiazine (SP), dodecyltrimethylammonium bromide (DOTAB), benzalkonium chloride (CB) or sodium dodecylbenzene sulfonate (DBSS) to improve the efficiency of the water filtration process by reducing biofouling. All membranes had lower hydrophobicity compared with PSF. The zeta potentials of all membranes were negative at pH 7.0, except for CB 10%. In the agar diffusion test, E. coli was considered to be sensitive to the antimicrobial effect of the nAgNS 1%, 3%, 6%, 10% and DOTAB 10%, whereas S. aureus was sensitive to the nAgNS 1%, 3%, 6%, 10%, DOTAB 10%, CB 0.22%, 2% and 10%. The lowest adhesion of E. coli was found in the nAgNS 6% and 10%. In the evaluation of the loss of flow rate during filtration of the E. coli suspension and pure water, nAgNS showed higher flow rate values when compared with PSF. The nAgNS did not release quantities of silver (0.1 mg/l) above the amount considered safe by the World Health Organization. Membranes nAgNS 6% and 10% showed the best anti-biofouling characteristic.

Physical-mechanical and antimicrobial properties of nanocomposite films with pediocin and ZnO nanoparticles.

This work aimed to develop nanocomposite films of methyl cellulose (MC) incorporated with pediocin and zinc oxide nanoparticles (nanoZnO) using the central composite design and response surface methodology. This study evaluated film physical-mechanical properties, including crystallography by X-ray diffraction, mechanical resistance, swelling and color properties, microscopy characterization, thermal stability, as well as antimicrobial activity against Staphylococcus aureus and Listeria monocytogenes. NanoZnO and pediocin affected the crystallinity of MC. Load at break and tensile strength at break did not differ among films. NanoZnO and pediocin significantly affected the elongation at break. Pediocin produced yellowish films, but nano ZnO balanced this effect, resulting in a whitish coloration. Nano ZnO exhibited good intercalation in MC and the addition of pediocin in high concentrations resulted crater-like pits in the film surfaces. Swelling of films diminished significantly compared to control. Higher concentrations of Nano ZnO resulted in enhanced thermal stability. Nanocomposite films presented antimicrobial activity against tested microorganisms.

Otimização da produção de nanopartículas de prata utilizando nova síntese e avaliação da sua ação sanitizante / Optimization of production of silver nanoparticles produced by new synthesis and evaluation of its sanitizing action

Sanitizantes químicos são utilizados na higienização de superfícies que entram em contato com os alimentos, de forma a eliminar patógenos e reduzir deterioradores assegurando a inocuidade dos alimentos para os consumidores. Atualmente, tem-se o interesse no desenvolvimento de novos antimicrobianos, em razão do aumento no número de bactérias resistentes. Neste contexto, o objetivo deste trabalho foi otimizar a produção de nanopartículas de prata a partir de uma nova síntese, bem como avaliar sua capacidade antimicrobiana por diferentes metodologias. Observou-se que o rendimento na produção das nanopartículas de prata aumentou à medida que a concentração do surfactante usado na dispersão foi também aumentada, isto pode ser explicado pelo fato da reação de formação das nanopartículas se caracterizar como uma catálise micelar. Pelos resultados obtidos no teste de adesão bacteriana, observouse que a adesão de Staphylococcus aureus e Listeria innocua foi menor nas superfícies condicionadas com as nanopartículas de prata. As nanopartículas de prata também foram capazes de reduzir o número de bactérias aderidas em diferentes superfícies de aço inoxidável, superfícies estas, comumente utilizadas nas indústrias de alimentos. Portanto, as nanopartículas de prata obtidas por uma nova síntese apresentam-se eficientes como agentes antimicrobianos, com potencial uso como sanitizantes, na indústria de alimentos.

Sanitizers are used to clean surfaces that come in contact with food in order to eliminate pathogens and reduce spoilage ensuring food safety for consumers. Actually, there is interest in developing new antimicrobial agents, due to the increase in the number of resistant bacteria. In this context, the work aimed to optimize the production of silver nanoparticles obtained by a new synthesis, and assess their antimicrobial ability. We observed that the yield in production of the silver nanoparticles increases as is also increased the concentration of surfactant used in the dispersion, since the reaction produced is characterized in a micellar catalyst. Results obtained during testing of bacterial adhesion showed us that the adherence of S. aureus and L. innocua was lower when the surfaces were covered with the silver nanoparticles. The nanoparticles were also able to reduce the number of attached bacteria on surfaces of stainless steel. Therefore, the silver nanoparticles obtained by a new synthesis have to be effective antimicrobial agents with the potential use as sanitizing in the food industry.

Work of adhesion of dairy products on stainless steel surface

The adhesion of the solids presents in food can difficult the process of surface cleaning and promotes the bacterial adhesion process and can trigger health problems. In our study, we used UHT whole milk, chocolate based milk and infant formula to evaluate the adhesion of Enterobacter sakazakii on stainless steel coupons, and we determine the work of adhesion by measuring the contact angle as well as measured the interfacial tension of the samples. Inaddition we evaluated the hydrophobicity of stainless steel after pre-conditioning with milk samples mentioned. E. sakazakii was able to adhere to stainless steel in large numbers in the presence of dairy products. The chocolate based milk obtained the lower contact angle with stainless steel surface, higher interfacial tension and consequently higher adhesion work. It was verified a tendency of decreasing the interfacial tension as a function of the increasing of protein content. The pre-conditioning of the stainless steel coupons with milk samples changed the hydrophobic characteristics of the surfaces and became them hydrophilic. Therefore, variations in the composition of the milk products affect parameters important that can influence the procedure of hygiene in surface used in food industry.

Bioactive Peptides: Synthesis, Properties, and Applications in the Packaging and Preservation of Food.

Bioactive peptides are protein fragments which have a positive impact on the functions and conditions of living beings. Peptides have shown several useful properties for human health, including antimicrobial, antifungal, antiviral, and antitumor activities. These compounds are produced by almost all species of life. However, they are produced in limited quantities in nature. As a result, researchers have tried to synthesize bioactive peptides to study their properties and applications in various areas. Among their applications in food preservation, peptides have been incorporated into packaging materials. This review begins with a brief description of the methods used for the synthesis, purification, and characterization of peptides. Also, the main bioproperties and mechanisms of action of peptides are discussed. Finally, some applications of peptides are presented, especially their use in active packaging, their effects on the polymeric matrix, and peptide migration.

Work of adhesion of dairy products on stainless steel surface.

The adhesion of the solids presents in food can difficult the process of surface cleaning and promotes the bacterial adhesion process and can trigger health problems. In our study, we used UHT whole milk, chocolate based milk and infant formula to evaluate the adhesion of Enterobacter sakazakii on stainless steel coupons, and we determine the work of adhesion by measuring the contact angle as well as measured the interfacial tension of the samples. In addition we evaluated the hydrophobicity of stainless steel after pre-conditioning with milk samples mentioned. E. sakazakii was able to adhere to stainless steel in large numbers in the presence of dairy products. The chocolate based milk obtained the lower contact angle with stainless steel surface, higher interfacial tension and consequently higher adhesion work. It was verified a tendency of decreasing the interfacial tension as a function of the increasing of protein content. The preconditioning of the stainless steel coupons with milk samples changed the hydrophobic characteristics of the surfaces and became them hydrophilic. Therefore, variations in the composition of the milk products affect parameters important that can influence the procedure of hygiene in surface used in food industry.

Assessment of hydrophobicity and roughness of stainless steel adhered by an isolate of Bacillus cereus from a dairy plant

The interaction between the surface of stainless steel and Bacillus cereus was studied in terms of the characteristics of interfacial interaction determined from the measurement of the contact angle of the surface of B. cereus and stainless steel in the presence or absence of B. cereus adherence. The microtopographies and the roughness of the surface of stainless steel and stainless steel adhered by B. cereus were evaluated with the help of atomic force microscopy and perfilometry. The strain of B. cereus studied was considered hydrophilic, whereas the stainless steel was considered hydrophobic. The adhesion was not thermodynamically favorable (ΔGadhesion > 0) between the stainless steel and the strain of B. cereus studied. Thus, the interaction between them was not favored by the thermodynamic aspect of adhesion. There was no difference (p > 0.05) in the roughness of the surfaces of stainless steel adhered by B. cereus when analyzed by atomic force microscope and perfilometry.

Toxigenic status of Staphylococcus aureus isolated from bovine raw milk and Minas frescal cheese in Brazil.

A group of 291 Staphylococcus aureus isolates from mastitic cow's milk (n = 125), bulk tank milk (n = 96), and Minas frescal cheese (n = 70) were screened for staphylococcal enterotoxin (SE) genes (sea, seb, sec, sed, see, seg, seh, sei, selj, and sell) and for the tst-1 gene encoding staphylococcal toxic shock syndrome toxin 1 by PCR assay. A total of 109 (37.5%) of the isolates were positive for at least one of these 11 genes, and 23 distinct genotypes of toxin genes were observed. Of the S. aureus isolates bearing SE genes, 17 (13.6%) were from mastitic cow's milk, 41 (41.7%) were from bulk tank milk, and 51 (72.9%) were from Minas frescal cheese. The occurrence of exclusively more recently described SE genes (seg through sell) was considerably higher (87 of 109 PCR-positive strains) than that of classical SE genes (sea through see, 15 strains). The SE genes most commonly detected were seg and sei; they were found alone or in different combinations with other toxin genes, but in 60.8% of the cases they were codetected. No strain possessed see. The tst-1 gene was found in eight isolates but none from mastitic cow's milk. Macrorestriction analysis of chromosomal DNA from 89 S. aureus isolates positive for SE gene(s) was conducted with the enzyme SmaI. Fifty-five distinct pulsed-field gel electrophoresis patterns were found, demonstrating a lack of predominance of any specific clone. A second enzyme, Apa I, used for some isolates was less discriminating than Sma I. The high genotype diversity of potential toxigenic S. aureus strains found in this study, especially from Minas frescal cheese, suggests various sources of contamination. Efforts from the entire production chain are required to improve consumer safety.