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

Silver point extended below canal orifice-endodontics, Silver point extende...

Silver point extended below canal orifice: - This discrepancy between the round silver wire and an irregularly shaped canal provides the clinician with an opportunity to use so

What is counsellor, Q. What is Counsellor? Counsellor is someone who gi...

Q. What is Counsellor? Counsellor is someone who gives advice about the problem. A counselor's role is to help patients help themselves. In our context  a counsellor is  a comm

Massaging and tumbling techniques in meat products, M a s s a g i n ...

M a s s a g i n g and tumbling techniques To improve the desirable characteristics of meat products massaging and tumbling techniques were developed. Massaging involves

.phylum pisces, wt is an air bladder and its function wt is catadromous and...

wt is an air bladder and its function wt is catadromous and anadromus migration

Does the environment exert an influence on the phenotype, Does the environm...

Does the environment exert an influence on the phenotype? The phenotype may be altered (compared to the original situation conditioned by its genotype) by nongenetic means, ins

Invasion or migration - ecology, Invasion or Migration - Ecology When ...

Invasion or Migration - Ecology When a habitat is changed it can be a potential site for the establishment of many organisms. Many species actually invade or reach this new si

Explain what is inversion, Explain what is Inversion ? Inversion is ano...

Explain what is Inversion ? Inversion is another way in which genetic recombination can occur, as seen below. In this case, the change occurs within a chromosome, rather than b

Decomposers, 5 beneficial effects of decomposers and 2 harmful effects

5 beneficial effects of decomposers and 2 harmful effects

Digestion, Digestion The nutritional requirements and the various way...

Digestion The nutritional requirements and the various ways used by heterotrophic organisms to obtain nutrition. Whether food is used to give energy or to build the body, the

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