Development of enterococci and production of tyramine during the manufacture and ripening of Cheddar cheese

peer-reviewedThe effect of six strains of enterococci (three strains of Enterococcus faecalis, and one strain each of Ec. faecium, Ec. durans and Ec. casseliflavus) on flavour development and tyramine production in Cheddar cheese during manufacture and ripening was studied in two trials. No strain produced gelatinase or haemolysin and all of them grew well during manufacture reaching 107 colony forming units (cfu)/g in 6 h, after which they remained more or less constant during at least 48 weeks of ripening. There was no relationship between tyramine production in a broth containing tyrosine and tyramine production in the cheese. All strains, except Ec. casseliflavus, produced tyramine in the cheese, with the greatest concentration (162 mg/kg) being produced by Ec. durans after 9 months ripening at 8 ºC. There was no statistically significant difference (P > 0.05) between the flavour of the control cheese and any cheese containing an enterococcus. Nevertheless, cheese made with Ec. faecium E-24 received the best score in each trial at both time points. No off-flavours were found. Regarding proteolysis, only Ec. faecalis E-140 showed significant (P < 0.05) increases in both phosphotungstic acid and pH 4.6 soluble N. It is concluded that enterococci have little effect on the flavour of Cheddar cheese.This project was partly financed under FAIR Contract CT97-3078 from the E

The microbiology of South African dried sausage

No Abstrac

The influence of the dressing procedure on the (mesophilic) bacterial population of baconer carcass surfaces

No Abstrac

Frequency and occurrence of Lactobacillus acidophilus in the gut of the pig, as indicated by its presence in the faeces

Faecal samples of 2 pigs, kept on a constant diet, were analysed for Lactobacillus acidophilus and other lactic acid bacteria at 1 week intervals over a period of 3 months. Enumeration of L. acidophilus by selective methods was verified by phenotypic identification of representative isolates. The total lactic acid bacteria (LAB) population ranged between 10⁸ and 10¹⁰ colony-forming units per gram of faeces over the 3 months period. L. acidophilus contributed on average a relatively constant figure of 10 % to the total LAB population.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Large Scale Pressure Fluctuations and Sunyaev-Zel'dovich Effect

The Sunyaev-Zel'dovich (SZ) effect associated with pressure fluctuations of the large scale structure gas distribution will be probed with current and upcoming wide-field small angular scale cosmic microwave background experiments. We study the generation of pressure fluctuations by baryons which are present in virialized dark matter halos and by baryons present in small overdensities. For collapsed halos, assuming the gas distribution is in hydrostatic equilibrium with matter density distribution, we predict the pressure power spectrum and bispectrum associated with the large scale structure gas distribution by extending the dark matter halo approach which describes the density field in terms of correlations between and within halos. The projected pressure power spectrum allows a determination of the resulting SZ power spectrum due to virialized structures. The unshocked photoionized baryons present in smaller overdensities trace the Jeans-scale smoothed dark matter distribution. They provide a lower limit to the SZ effect due to large scale structure in the absence of massive collapsed halos. We extend our calculations to discuss higher order statistics, such as bispectrum and skewness in SZ data. The SZ-weak lensing cross-correlation is suggested as a probe of correlations between dark matter and baryon density fields, while the probability distribution functions of peak statistics of SZ halos in wide field CMB data can be used as a probe of cosmology and non-Gaussian evolution of large scale structure pressure fluctuations.Comment: 16 pages, 9 figures; Revised with expanded discussions. Phys. Rev. D. (in press

The influence of various production processes on the microbiology of manufactured meat products

No Abstrac

Biological degradation of aflatoxin B1 by Rhodococcus erythropolis cultures

Aflatoxin contamination of food and grain poses a serious economic and health problem worldwide, but particularly in Africa. Aflatoxin B1 (AFB1) is extremely mutagenic, toxic and a potent carcinogen to both humans and livestock and chronic exposure to low levels of AFB1 is a concern. In this study, the biodegradation of aflatoxin B1 (AFB1) by Rhodococcus erythropolis was examined in liquid cultures using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), electro spray mass spectrometry (ESMS) and liquid chromatography mass spectrometry (LCMS). AFB1 was effectively degraded by extracellular extracts from R. erythropolis liquid cultures. Results indicated that the degradation is enzymatic and that the enzymes responsible for the degradation of AFB1 are extracellular and constitutively produced. Furthermore, the biodegradation of AFB1 when treated with R. erythropolis extracellular fraction coincided with a loss of mutagenicity, as evaluated by the Ames test for mutagenicity. © 2006 Elsevier B.V. All rights reserved.Articl