Evaluation of the bacterial adhesion in polymers employed in the food industry irradiated with cobalt 60

A adesão de Pseudomonas fluorescens ATCC 13525 ao polietileno de baixa densidade (PEBD) após irradiação com 0, 5, 10, 15, 20 e 25 kGy foi avaliada pelas técnicas de contagem-padrão em placa (CPP) e microscopia de epifluorescência (MEF). Constatou-se que, independentemente da dose de irradiação e da técnica empregada, a adesão não apresentou diferença significativa (p &#8805; 0,05). Na avaliação da adesão de Staphylococcus aureus ATCC 6523 e de Pseudomonas fluorescens ATCC 13525 em polináilon, PEBD e poli(cloreto de vinilideno) (PVDC) irradiados com cobalto 60, nas doses de 0, 50, 100, 200, 300 e 400 kGy, observaram-se diferenças significativas (p<0,05) entre os microrganismos, polímeros, graus de irradiação e também na interação entre microrganismos e polímeros. A adesão de S. aureus variou de 1,40 a 14,5 UFC.cm 2 por 104 UFC/mL pela técnica de CPP e de 14,3 a 55,62 UFC.cm 2 por 104 UFC/mL pela MEF; esses valores foram superiores aos encontrados para P. fluorescens: 0,15 a 7,94 e 4,93 a 24,97 UFC.cm 2 por 104 UFC/mL, respectivamente. O processo de adesão de S. aureus pôde ser explicado pelas alterações ocorridas na estrutura dos polímeros decorrentes da irradiação. Para P. fluorescens a adesão não foi associada às alterações na estrutura dos polímeros causadas pela irradiação, sugerindo-se, nesse caso, que outros fatores tenham contribuído para o processo de adesão. No estudo da rugosidade dos polímeros por microscopia de força atômica (MFA) e de carga máxima de ruptura, constatou-se que a irradiação alterou a microtopografia e a resistência dos polímeros. Estas técnicas foram melhores do que a microscopia eletrônica de varredura para avaliar alterações na rugosidade dos polímeros. Os resultados indicaram que o aumento na dose de irradiação dos polímeros resultou em maior adesão microbiana, em razão das alterações físicas na estrutura polimérica dos polímeros.The adhesion of Pseudomonas fluorescens ATCC 13525 to low density polyethylene after irradiation with 0, 5, 10, 20 and 25 kGy was evaluated by the technique of standard counting in plaques (SCP) and epifluorescense microscopy (MEF). It was found that, regardless of the dose of irradiation and the employed technique the adhesion did not exhibit significant difference (p&#8805;0.05) In the evaluation of the adhesion of Staphylococcus aureus ATCC 6523 and of Pseudomonas fluorescens ATCC 13525 in poly-nylon, PEBD and poly (vinyldene chloride) (PVDC) irradiated with cobalt60 in the doses 0, 50, 100, 200, 300 and 400 kGy significant differences were observed (p<0.05) between the microorganisms, polymers, degrees of irradiation and also in the interaction between the microorganisms and the polymers. The adhesion of S. aureus varied from 1,40 to 14,5 UFC.cm-2 per 104 UFC.mL-1 by the SCP technique and from 14,3 to 55,62 UFC.cm-2 per 104 UFC.mL-1 by the MEF, values superior to those found for P. fluorescens, 0.15 to 7,94 and 4,93 to 24,97 UFC.cm-2 per 104 UFC.mL-1, respectively. The process of adhesion of the S. aureus might be explained by the alterations that occurred in the structure of the polymers due to the irradiation. For P. fluorescens adhesion was associated with the alterations in the structures of the polymers due to the irradiation, which suggest, in this case, that other factors contributed to the adhesion process. In the study of the rugosity of the polymers by atomic force microscopy (AFM), and maximum charge of rupture, it was found that that the irradiation altered the micro topography and the resistance of the polymers. These techniques were better than electronic scanning microscopy to evaluate alterations in the rugosity of the polymers. The results indicated that the increase in the irradiation dose on the polymers resulted in a larger microbial adhesion due to physical alterations in the polymeric structure of the polymers.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Evaluation of the use of transglutaminase in dairy drinks made from goat milk

The aim of this study was to evaluate the use of transglutaminase in dairy drinks made from with goat milk with 45% of serum, and the physical, chemical, microbiological and sensory characteristics of these drinks within the expiration date of the product. In the first phase, five different levels of transglutaminase (0, 0.2, 0.3, 0.4, 0.5 U/g) were evaluated. In the second phase, the drink that had the best sensory acceptability was evaluated for 30 days. It was observed that the dairy drink treated with 0.5 U/g transglutaminase showed higher sensory acceptability in relation to the 7.18 overall impression. The color values of the dairy drink treated with 0.5 U/g showed no significant difference (p&lt;0.05). The values of lactic acid bacteria are established according to the legislation. Results show the feasibility of the use of transglutaminase in dairy drinks

Evaluation of ultraviolet radiation to control microorganisms adhering to low-density polyethylene films Avaliação da radiação ultravioleta no controle de microrganismos aderidos em filmes de polietileno de baixa densidade

Efficiency of ultraviolet (UV) radiation in reducing the cell number of Staphylococcus aureus ATCC 25923 and Escherichia coli K-12 adhered to low-density polyethylene (LDPE) films was evaluated. The microorganisms were let to adhere to the surface of LPDE bags for 12h at 18ºC, and then submitted to UV radiation at an intensity 196 µW.cm-2, 254nm, for 2 seconds. Staphylococcus aureus was less resistant to UV radiation than E. coli, and the efficiency increased with the increase of the concentration of microbial suspension. After 1500 hours of use the UV radiation intensity of the lamp was reduced from 288 to 78 µW.cm-2, and the higher decrease occurred in the first 100 hours of use. Also, the efficiency of the UV radiation decreased after 1500 hours of use. The number of mesophilic aerobes on the surface of LDPE films was reduced by 90% after irradiation with 137 µW.cm-2 for 2 seconds. Atomic force microscopy revealed cracks and crevices and protuberances on the LDPE surface, a topography that can protect the cells from UV radiation, reducing the efficiency of the process. The results showed that UV radiation can be a useful technique for reducing the microbiota adhered to LDPE films.<br>A eficiência da radiação ultravioleta (UV) na redução do número células de Staphylococcus aureus ATCC 25923 e Escherichia coli k12 aderidas a filmes de polietileno de baixa densidade (PEBD) foi avaliada. Os microrganismos em suspensões foram aderidos à superfície de sacos de PEBD a 18ºC durante 12 horas, e, em seguida, submetidos à exposição de raios UV na intensidade de 196 µW.cm-2 a 254 nm, durante 2 segundos. Staphylococcus aureus foi menos resistente do que E. coli à ação da radiação UV. Após 1500 horas de uso, a intensidade da radiação UV reduziu-se de 288 para 78 µW.cm-2, com declínio acentuado nas 100 horas iniciais. A eficiência da radiação UV na inativação dos microrganismos decresceu após 1500h de uso da lâmpada germicida. O numero de mesófilos aeróbios nas superfícies dos filmes de polietileno de baixa densidade (PEBD) foi reduzido em 90% após a irradiação com 137 µW.cm-2. Fendas e elevações, observadas na superfície do PEBD através de microscopia de força atômica, podem proteger as células do contato com a radiação UV, reduzindo sua eficiência. Os resultados mostram que a radiação UV é uma técnica útil na redução da microbiota aderida à superfície de filmes de PEBD

Physical-chemical, microbiological and sensory evaluation of spicy soybean paste

This study aimed to develop a spicy soybean paste. Three formulations of spicy soybean paste were prepared, and then submitted to prior microbiological and sensory acceptance test with 50 untrained tasters. The most accepted formulation was evaluated on the microbiological quality during its shelf life. Significant differences were found (p <0.05) for the attributes flavor, aroma, texture and overall impression for the formulation B of spicy soybean paste, the most accepted of the two. It was found that the microbiological analyzes are within the established by the Technical Regulation on microbiological standards for food nº 12 of January 2nd, 2001. The mean values found for the physicochemical analyzes were 38.93% for moisture, 11.00% for lipids, proteins and 11.12% to 6.85% for ash content. The spicy soybean paste is a good food option, presenting good sensory acceptance

Bacterial adherence to different inert surfaces evaluated by epifluorescence microscopy and plate count method

The adherence of Listeria inoccua L6a and Staphylococcus aureus ATCC6538 was evaluated on stainless steel (SS), polycarbonate (PC) and polypropylene (PP) chips. The EP results showed a significant difference (p<0.05) among the microorganism species interactions, the surfaces and the contact time. The number of adhered cells on the chip surfaces increased as contact time increased and the number of L. innocua or S. aureus on the surface of SS, PC and PP chips reached 1.0x10(5) CFU/cm² after 12 h of contact, in both methods. The CP method showed a better sensitivity to detect low number of adhered cells. The EP was better when the average number of adhered cells was between 10 and 100 per microscopy field