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

Are there chloroplasts in cyanobacteria, Are there chloroplasts in cyanobac...

Are there chloroplasts in cyanobacteria? In cyanobacteria there are no chloroplasts and the chlorophyll layers are dispersed in cytosol. Which chemical element is central in

What is infra-diaphragmatic type of tapvc, What is Infra-diaphragmatic Type...

What is Infra-diaphragmatic Type of TAPVC? Initial stages of operation are the same as for supracardiac type of TAPVC. The heart is lifted out of the pericardial cavity and c

Ameoba, what is the scientific name of ameoba

what is the scientific name of ameoba

Sociability - qualitative characters, Sociability (Gregariousness) Soc...

Sociability (Gregariousness) Sociability refers to the nature of grouping of individual plants, that is, whether they grow singly, in patches, in colonies or evenly intermixed

History of evolution, History of evolution? Evolution is usually define...

History of evolution? Evolution is usually defined as "change over time." In spite of the incredible diversity of life found on Earth, many fundamental characteristics are shar

Define the estimation of haemoglobin in blood, Define the Estimation of Hae...

Define the Estimation of Haemoglobin in Blood? Several methods are used to determine haemoglobin. In these methods hemoglobin is measured as oxyhaemoglobin, carboxyhaemoglobin,

Describe the non direct approach, Q. Describe the Non Direct Approach? ...

Q. Describe the Non Direct Approach? The counsellor's participation is minimal; here the counsellee freely expresses. The counsellor pays attention to the emotion and attitudes

Chlamydiosis-clinical manifestations, Clinical manifestations Since the...

Clinical manifestations Since the disease due to Chlamydia involves many organs/systems, system-wise descriptions of clinical signs is described as under: Genital infectio

Explain the transcription factor of zinc, Explain the Transcription Factor ...

Explain the Transcription Factor of Zinc? Zinc is an important structural component of DNA- binding proteins also known as 'transcription factors'. These transcription factors

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