摘要:

SummaryIt has been recognized for many years that irradiation can remove spoilage organisms and pathogens from foods thereby extending shelf‐life and reducing the risk of food poisoning. Shelf‐life extension is of benefit to the food processor as the market can expand in terms of both variety and supply distance. The consumer also has the advantage of a longer ‘at home’ shelf‐life which is in keeping with the trend for less frequent shopping rather than the daily purchasing of fresh foods.Combination treatments is the area where irradiation shows the greatest potential. Successful combinations will enhance the preservative action and/or reduce the severity of one or all of the treatments. This should give better product quality without reducing food safety. Combination treatments which show promise include irradiation with mild heat treatment, with MAP or with curing salts. Such treatments would be of value in increasing the quality of fruits, vegetables and meats. The increasing variety of refrigerated foods, including value‐added and ready prepared products could also be treated in this way. In addition to shelf‐life extension, psychrotrophic pathogens such as listeria and yersinia would be killed along with mesophilic pathogens like salmonella. More foods traditionally regarded as unsuitable for irradiation may be successfully treated if correct processing conditions are used. Camembert cheese, made from unpasteurized milk, can be irradiated to kill pathogens, provided the storage temperature and ripening are carefully controlled.Further work, including sensory evaluation studies, is required to optimize combination treatments for irradiated foods and to investigate the microbiological implications and economics of the

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01274.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Electroporation‐mediated transformation ofLactococcus lactiswith plasmid pGB301, a 9.8 kilobase pair vector (Behnke et al. 1981), has been reported by McIntyre&Harlander (1989a). Improved transformation efficiencies of 102‐103/μg DNA were achieved by altering the conditions under which the bacteria were grown prior to electroporation (McIntyre&Harlander 1989b). This present investigation sought to improve still further transformation efficiencies in order to provide a reliable high frequency transformation system forLc. lactissubsp.la

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of selected fermentation gases (H2, CO2, CH4) on refuse acidogenesis and methanogenesis were examined with laboratory batch cultures. Although extremely limited initial stimulation of total methanogenesis resulted from H2supplementation, both acetogenesis and acetate methanogenesis were inhibited. A culture headspace atmosphere of 100% CO2effected 98% inhibition of methanogenesis and partial suppression of acetogenesis. A gas mixture of CO2‐CH4(40: 60) also exerted inhibitory effects on methanogenesis but not acetogenesis. Conversely, 100% CH4did not significantly reduce methanogenesis or acetogenesis. Individual supplementation with N2or CO2in conjunction with increased culture headspace pressure (1.6 bar) approximately doubled the CH4volumes but volatile fatty acid pattern changes were not apparent. The possible implications of high partial pressures of gas on refuse methanogenesis are discusse

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The statistical technique of response surface methodology was used to optimize the component concentrations of aSalmonellalysine medium for conductance responses on a Malthus microbial growth analyser. When the original and modified media were compared, conductance changes in pure cultures improved by 135 μS on average, and those from fopds both naturally contaminated and spiked with salmonellas by 220 μS. Salmonellas were successfully isolated from all assays after subculturing conductance broths onto xylose lysine desoxycholate agar and confirming by serolog

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01277.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Plasmid DNA of six strains ofRhizobium galegaewas blotted onto nitrocellulose and hybridized with the 4.8 kb PstI fragment of pRme4lb, a megaplasmid carrying the nifH and the nifD genes ofRhizobium meliloti.DNA sequences homologous to the nif genes were localized on the megaplasmid or on the large plasmid bands of theR. galegaestrains tested. In three of the strains analysed the nif genes were located on the megaplasmids. In the other three strains investigated, which also possessed megaplasmids, the nif genes were located on the smaller plasmids.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01278.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The susceptibility of strains ofEnterobacter cloacae, Klebsiella pneumoniae, Serratia marcescens, Pseudomonas aeruginosa, Proteus mirabilisandEscheriehia colito six aminoglycosides was tested in media of different osmolarity and ionic content. We observed that increasing osmolarity decreased susceptibility of these Gram‐negative bacteria to all antibiotics used. On the other hand, raising of ionic strength increased the susceptibility to tobramycin, neomycin and gentarnicin in all bacteria teste

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01279.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

An electroporation‐induced transformation system was developed for two raw sausage starter organisms:Lactobacillus curvatusLc2‐c andLact. sakeLs2. Several plasmids of different origin (pAMβ1, pIL253, pNZ12 and pLP825) were tested for transformation and expression of their resistance determinants. Transfer rates were strongly dependent on growth phase and voltage. Several parameters were studied with possible influence on trasformation efficien

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01280.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Improvements in performance of a lysine conductance medium for the detection of salmonellas were achieved from a study of the effects of its various components. When sodium biselenite was included as an inhibitor for non‐salmonella organisms conductance signals were depressed. The inclusion of sodium chloride reduced this toxicity and improved conductance responses. Increasing the pH to pH 7.0 prevented the medium becoming too acidic and inhibitory to salmonellas. The new medium detected 70‐0% of salmonella‐positive animal protein sa

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01281.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The percentage of dividing biomass was calculated for attached and free‐living bacteria, in a coastal marine and a freshwater system. In the marine system with low concentrations of total and dissolved organic carbon (TOC and DOC) the percentage of dividing biomass was higher for attached (41.4 ± 13.9) than for the free‐living bacteria (22.0 ± 11.7). However, in the freshwater system, which had a higher concentration of TOC and DOC, the percentage of dividing biomass was similar for both communities‐attached (53.4 ± 26.5) and free‐living (78.4 ± 21.9). Thus the attachment to particulate material is not necessarily an advantage in waters where dissolved organic nutrients are readil

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01282.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The lactoperoxidase level in milk from 10 goats throughout a 150 d lactation period was 1.55 units/ml, with a range of 0.05‐3.55 units/ml for invidiual samples. Samples obtained 0–24 h after kidding exhibited the lowest mean concentration (0.50 units/ml). Mean thiocyanate content was 4.03 ppm, with a range of 0.67‐11.17 ppm for indidual sa

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1990.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY