Effect on microbial growth and activity, Biology

Assignment Help:

Effect on Microbial Growth and Activity

Bacteria require higher aw for growth than fungi. Gram-negative bacteria have higher requirements than gram positives. Most spoilage bacteria do not grow below aw 0.91, while spoilage molds can grow as low as 0.80. Food-poisoning bacteria like Staphylococcus aureus can grow at aw as low as 0.86, while Clostridium botulinum does not grow below 0.94. Yeasts and molds can grow over a wider aw range than bacteria. The lowest aw values for bacteria is 0.75 for halophilic bacteria, while xerophilic molds and osmophilic yeasts can grow at aw values of 0.65 and 0.60, respectively. The limiting value of water activity for the growth of microorganisms is about 0.6 and below this value the spoilage of foods is not due to microorganisms but may be due to insect damage or chemical reaction such as oxidation. At a water activity of 0.6, corresponding to a water potential of -68MPa (Mega Pascals), the cytoplasm would need to contain very high concentrations of an appropriate compatible solute and it is probable that the macromolecules such as DNA would no longer function properly and active growth may stop.


Related Discussions:- Effect on microbial growth and activity

Determine the part of the human visual system, Which is the part of the hum...

Which is the part of the human visual system where the receptors that sense light, i.e., the photoreceptor cells, are located? How do those cells work? The photoreceptor cells

What are primary consumers, What are primary consumers? Can a food chain pr...

What are primary consumers? Can a food chain present quaternary consumers without having secondary or tertiary consumers? Can a tertiary consumer of one chain be a primary or secon

Explain gonorrhea, Gonorrhea Single doses of cefixime (Suprax) orally ...

Gonorrhea Single doses of cefixime (Suprax) orally or ceftriaxone  (Rocephin)  intramuscularly (IM) are highly effective for uncomplicated anogenital or pharyngeal infection,

Molecular biology on which dna fingerprint is based, What is the fact of Mo...

What is the fact of Molecular Biology on which DNA fingerprint is based? The DNA fingerprint, the method of individual identification using DNA, is based on the fact that the D

Explain the failure of endodontic Treatment, Explain the Failure of Endodon...

Explain the Failure of Endodontic Treatment 1. Microorganisms are left inside the canal - Improper/inability of cleaning and shaping, - Source of infection could be: peri

How does phosphocreatine act in the muscle contraction, How does phosphocre...

How does phosphocreatine act in the muscle contraction and relaxation? Phosphocreatine is the main means of energy storage of the muscle cells. During relaxed periods ATP mo

Substances that facilitate to compose the plasma membrane, Q. What are the ...

Q. What are the chemical substances that facilitate to compose the plasma membrane? The major constituents of the plasma membrane are phospholipids, proteins and carbohydrates.

Watson - crick model how many polynucleotide chains, Q. As per the Watson -...

Q. As per the Watson - Crick Model how many polynucleotide chains does a DNA molecule have? The DNA molecule is formed by two polynucleotide chains bound in antiparallel mode (

Calculating the amounts of dissimilar nucleotides, Erwin Chargaff conducted...

Erwin Chargaff conducted a series of experiments in which he was calculating the amounts of dissimilar nucleotides that were present in dissimilar tissues and organisms. These stud

Monosaccharide derivatives, MONOSACCHARID E DERIVATIVES They are modif...

MONOSACCHARID E DERIVATIVES They are modified monosaccharides. G L YCOSIDES They are compounds formed by condensation reaction between a sugar and hydroxyl group

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd