摘要:

Several factors relevant to food preservation had large effects on the resistance ofL. monocytogenesto high hydrostatic pressure. Cells in the stationary phase of growth were much more resistant to pressures above 200MPa than those in the exponential phase. Following treatment for 10 min at 400 MPa viable numbers of stationary phase cells were reduced by only 1.3 log10units compared with more than 7 log10units for exponentially growing cells. Stationary phase cells were sensitised to pressure by butylated hydroxyanisole, potassium sorbate and by acid conditions. The most effective sensitiser was BHA which, at 1.55 mM, caused a 104‐fold enhancement of killing by treatment at 300 MPa for 10 min. Propyl hydroxybenzoate, butylated hydroxytoluene and sodium ascorbate were without effect. Xylitol (15%) protected log phase cells against inactivation by pressure: after treatment at 350 MPa for 10 min viable numbers were reduced by only 0.24 log10units compared with 2.4 log10units in the absence of xylitol. The physicochemical environment can substantially increase or decrease resistance to pressure and these effects will require quantification if the microbiological effects of pressure are to be predicted.

ISSN:0890-5436    

DOI:10.1080/08905439509549881

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439509549880

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The main drawback of yeast biomass as a source of protein for human consumption is its high nucleic acid content. The present study deals with the development of a process for reducing the nucleic acid content of strains ofSaccharomyces cerevisiae, Candida utilis, C.tropicalisandC.lipolyticaby treating with an RNase ofAspergillus candidusstrain Ml6a. The cells were permeabilised either by heat‐treatment at 95°C for 5 min. or by treatment with chloroform for 6h followed by a heat treatment at 65°C for 3 min. The former pretreatment was sufficient forC. utilisandC.tropicalisstrains whereasS.cerevisiaerequired the latter treatment. The optimum conditions for the enzymatic treatment were a pH of 4.5–5.0, temperature of 45–55°C, incubation period of 60–90 min and an enzyme to cell ratio of 1:6,000 (w/v). Crude enzyme preparations showed a better activity than the pure enzyme. Under optimal conditions 80–85% of the total nucleic acid could be removed from yeast cells by the enzymatic treatment without any significant concomitant loss of protein.

ISSN:0890-5436    

DOI:10.1080/08905439509549882

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Callus was initiated from immature ovary portion of flower ofGardenia jasminoidesEllis on Murashige and Skoog (MS) medium (1962) supplemented with 2,4‐dichlorophenoxyacetic acid (2 mgl−1) and kinetin (0.5 mgl−1). Callus on subculture onto MS medium, with reduced nitrate and phosphate levels and supplemented with indole‐3‐butyric acid (1 mgl−1) and kinetin (1 mgl−1) induced yellowish pigmented callus when incubated in dark at 25+2° C. The extracts of yellowish callus when analysed by TLC and HPLC showed the presence of crocin and crocetins. Both crocin and crocetins were at low levels inGardeniacallus as compared toGardeniafruit or Saffron stigma.

ISSN:0890-5436    

DOI:10.1080/08905439509549883

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This study describes the production of a solid phase assay (dipstick test) for histamine in tuna based on the coupling of diamine oxidase to a peroxidase/dye system. The optimized dipstick preparation consisted of a diamine oxidase/peroxidase/Stabilcoat mixture layered onto a tetramethylbenzidine color strip. The assay was linear to 1.0 mM histamine (RSQ = 0.994) and the minimum detectable concentration was 0.07 mM corresponding to 2.3 mg% in tuna extracts. Quality control samples gave intra and interassay precisions of 9.14–9.84 %CV and 7.08–13.86 %CV respectively. Similarly, the assay was accurate (p> 0.05) for both low and high controls. Histidine and cadaverine did not interfere with the assay whereas putrescine reacted slightly with the dipstick. Histamine determinations of fresh and spoiled tuna gave good agreement between the dipstick method and both the official reference and modified AOAC flurometric methods.

ISSN:0890-5436    

DOI:10.1080/08905439509549884

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Effects of chitosan andAspergillus flavusto enhance elicitation of phenolic compounds in viable peanut seeds were conducted at two water activity levels.In vitroeffects of phenolic acids onA. flavusgrowth and aflatoxin B1production were also studied. Chitosan enhanced elicitation of free phenolic compounds (FPC) at Aw .85 and .95 levels.A. flavusinitially decreased and subsequently increased FPC content, but bound phenolic compounds (BPC) decreased during incubation. Chitosan +A. flavustreatment caused an increase in FPC reaching a plateau between 24–48 h at Aw .85 while BPC levels increased over the same period at both Aw levels. Major free and bound phenolic acids detected were p‐coumaric, ferulic and an unknown phenolic acid eluting at a retention time of 22 min. Generally, chitosan significantly enhanced elicitation of free ferulic and p‐coumaric acids and bound p‐coumaric acid at Aw .95. Free unknown phenolic and bound ferulic acids at Aw .85 were enhanced by chitosan.A. flavuscaused significant induction of bound p‐coumaric and ferulic acids and free unknown phenol at Aw .85. Chitosan +A. flavusenhanced free p‐coumaric (3 h) and unknown phenolic acids and bound p‐coumaric acid at Aw .95 while bound ferulic acid was enhanced at Aw .85. Chitosan limitedA. flavusgrowth and subsequent aflatoxin production by inducing susceptible tissues to produce more preformed phenolic compounds.

ISSN:0890-5436    

DOI:10.1080/08905439509549885

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

ß‐Glucosidases ‐ Biochemistry and Molecular Biology, Asim Esen, American Chemical Society, Washington, DC, 1993, 260 pages

ISSN:0890-5436    

DOI:10.1080/08905439509549886

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0890-5436    

DOI:10.1080/08905439509549879

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor