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

Fundamental structure of the hiv virus, Q What is the fundamental structure...

Q What is the fundamental structure of the HIV virus? What is the function of the glycoproteins of its envelope? HIV is an RNA virus in its core there are two strands of RNA an

Define discovery of other essential nutrients, Define Discovery of other Es...

Define Discovery of other Essential Nutrients? Following the identification of the food factors involved in beriberi, pellagra and scurvy, the search was on for other water-sol

Physiological & socio psychological factor- public nutrition, Define Physio...

Define Physiological and Socio Psychological Factors - public nutrition? Food related behaviour depends on a combination of biochemical factors, mainly, physiological aspects a

Can it be influenced by environmental factors, Variation exhibited in share...

Variation exhibited in shared traits present in a population is due to alleles of the shared genes. can be influenced by interactions of alleles of multiple genes. Can be influence

Cytokinesis in an animal cell, Cytokinesis in an animal cell: Splitting...

Cytokinesis in an animal cell: Splitting of the cell is called cytokinesis which starts at telophase. In animal cells, microtubules form a furrow in a ring around the cell.

Introduction of quality attributes of food, Q. Introduction of Quality Attr...

Q. Introduction of Quality Attributes of Food? Seasonal fruits and vegetables are grown in plenty, and are available in their respective seasons in abundance. While choosing th

Animal around us, #question.what are the reason that arthropodans are abund...

#question.what are the reason that arthropodans are abundant in nature.

What are the physical propertie of sol, What are the physical propertie of ...

What are the physical propertie of sol Sols resemble liquids in their main physical properties - that is, they flow and they do not show rigidity of form. However, when a sol a

What is imbibition, What is Imbibition The ability of colloids to pick ...

What is Imbibition The ability of colloids to pick up water and swell when they come in contact with water is called imbibition. Imbibition is usually accompanied by the evo

Simple cuboidal epithelium and columnar epithelium, Q. How different is the...

Q. How different is the simple cuboidal epithelium from the columnar epithelium? Where can these epithelia are found in the human body? The simple cuboidal epithelium is made o

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