ABSTRACT
OBJECTIVE: To establish an oil bath method to determine the D values and Z value of biological indicators in spore suspension forms for moist heat sterilization. METHODS: Spore suspension was sealed up in glass capillary, which was heated by thermostat oil bath. D value and Z value were determined by survivor curve method. RESULTS: The D values of Geobacillus stearothermophilus ATCC7953 spores suspension at 117, 121 and 125 ℃ were 7.04, 2.18 and 0.65 min, respectively, and the Z value was 7.75 ℃. The D values of Clostridium sporogenes CMCC(B)64941 spores suspension at 95, 100 and 105 ℃ were 11.36, 2.85 and 0.45 min, respectively, and the Z value was 7.14 ℃. CONCLUSION: By simulating the sterilization of aqueous liquid with oil bath method, the D values and Z values of biological indicators in spore suspension forms for moist heat sterilization can be determined conveniently and accurately(r2 is above 0.980 0). The oil bath method can be used for heat resistance research of biological indicators in spore suspension form for moist heat sterilization.
ABSTRACT
Lentinula edodes (Berk.) Pegler (shiitake) é o segundo cogumelo mais consumido no mundo e sua produção pode ser feita em toras de madeira ou em cultivo axênico utilizando resíduos agroindustriais como substrato. O cultivo do shiitake no Brasil tem sido gravemente prejudicado pela alta incidência de fungos contaminantes, como Trichoderma sp., e pela ausência de linhagens mais adaptadas às temperaturas tropicais. Duas linhagens resistentes ao Trichoderma sp. foram obtidas por meio de seleção quando crescidas em contato com o fungo contaminante e, por meio de fragmentação micelial, foram obtidas linhagens resistentes a temperaturas elevadas, capazes de crescer a 30º C em meio de cultura.
Lentinula edodes (Berk.) Pegler (shiitake) is the second most consumed mushroom in the world and its production can be made in natural logs or in axenic culture using agroindustrial residues as substrate. The cultivation of shiitake in Brazil has been seriously harmed by the high incidence of contaminant fungi such as Trichoderma sp. and by the absence of strains adapted to tropical temperatures. Two strains resistant to Trichoderma sp. were obtained by selection when grown in contact with the contaminant fungus and, by mycelial fragmentation, strains were obtained that can resist high temperatures and grow at 30º C in a culture medium.
ABSTRACT
The objective of this study was to isolate lactic acid bacteria (LAB) from vacuum packaged beef and to investigate their antagonist activity. LAB mean counts of 5.19 log cfu/cm² were obtained from five samples of vacuum packaged beef. Two hundred isolates were selected and screened for the inhibitory effect on five ATCC reference Lactobacillus strains. Thirty six isolates showed activity in the agar spot test against at least two of the indicator strains. However, only six cell free supernatants (CFS) from these isolates exhibited activity against the indicator strains using the well-diffusion test and conditions that eliminated the effects of organic acids and hydrogen peroxide. L. acidophilus was the most sensitive indicator tested, whereas L. plantarum and L. fermentum were the most resistant ones. Identification by MIDI system indicated that these LAB isolates were Lactococcus lactis subsp. cremoris, Pediococcus acidilactici, Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei GC subgroup A. The antagonistic factors produced by most of these LAB against L. acidophilus were resistant to heat treatment (100ºC for 10 min) and stable over a wide pH range (4.0 to 9.0). These data suggest that these isolates could be used as promising hurdles aiming increased safety and extended shelf life of meat products.
Este trabalho teve como objetivo isolar bactérias ácido láticas (BAL) de carne bovina embalada a vácuo e investigar sua atividade antimicrobiana. Uma média de 5,19 log ufc/cm² BAL foi obtida de cinco amostras. Duzentos isolados foram selecionados e o efeito inibitório sobre cinco cepas ATCC referência de Lactobacillus foi pesquisado. Trinta e seis isolados apresentaram atividade inibitória pelo teste 'agar spot' de pelo menos duas das cepas indicadoras. Sobrenadantes isentos de células (SIC) destes isolados foram obtidos. Apenas seis SIC apresentaram atividade contra as cepas indicadoras usando o método de difusão em poços e condições que eliminaram a influência do peróxido de hidrogênio e de ácidos orgânicos. L. acidophilus foi a cepa indicadora mais sensível, enquanto L. plantarum e L. fermentum foram as mais resistentes. Identificação pelo sistema MIDI indicaram que as BAL isoladas eram Lactococcus lactis subsp. cremoris, Pediococcus acidilactici, Lactobacillus delbrueckii subsp. bulgaricus e Lactobacillus casei GC subgrupo A. O efeito antagonista ao L. acidophilus dos SIC destas BAL foi resistente ao tratamento térmico (100ºC/10 min) e estável em ampla faixa de pH (4,0 a 9,0). Estes dados sugerem que os isolados obtidos poderiam ser utilizados como barreiras promissoras no aumento da segurança e na extensão da vida útil de produtos cárneos.
Subject(s)
Cattle , Food Microbiology , Food Packaging , In Vitro Techniques , Lactobacillus/isolation & purification , Meat Products/analysis , Culture Media , Food Samples , MethodsABSTRACT
For heat-resistance derterminations, a Neosartorya fischeri ascospore suspension, obtained at three different conditions of temperature (20, 30 and 35ºC) and age (1, 2 and 3 months), was heat treated in pineapple juice with three different ratio conditions. The 1/k (min) values obtained were statistically analysed through the software Statisitca 6.0. At 80ºC, when there was a level change in the ratio factor from a lower (10) to a higher one (38), the thermal resistance (1/k) increased in approximately 41 per cent. The increase of the ascospore production age and temperature caused an increase on the thermal resistance approximately equal to 28 per cent and 14 per cent, respectively. Throufh the results, it could be concluded that N. fischeri presented lower thermal resistance for heating mediums with lower ratio values, or rather, the increase of the soluble solids concentration caused an increase of its thermal resistance. It was also observed that the ascospore production age and temperature increased significantly the thermal resistance of this mould in pineapple juice.