Lec_11_Foodborne Factors

Lec_11_Foodborne Factors - Factors Affecting Foodborne...

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Factors Affecting Foodborne Disease
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Types of Foodborne Disease Infection Foodhandler Food Concentration Direct Contamination Water-washed Toxico-infection Intoxication (food poisoning) Bacterial and Fungal Toxins Shellfish Toxins Metals, Chemicals, etc. Allergy
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Microbial Growth in Food Bacteria and Fungi Complex Ecology Interaction with multiple environmental factors controls whether an organism can grow in a given environment Food Preservation Ecology of zero growth
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Microbial Growth in Food Intrinsic Factors : pH Water Activity Salt Concentration Nutrients Etc. Extrinsic Factors Temperature Gaseous Conditions Presence of Other Microbes Heterogeneity - Question of scale - Food items may have several distinct microenvironments
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pH Influences genes encoding carboxylases, lactate dehydrognease, outer membrane proteins, and virulence factors Cells sense change in pH by various mechanisms (e.g. protonation/deprotona tion of amino acids)
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pH Two pHs are important: external and internal Cells must maintain internal pH to maintain viability thus redundant mechanisms for pH maintenance: for example in S.enterica Homeostatic response (allosteric regulation of proton pumps etc.) Acid tolerance response (membrane –bound ATPase proton pumps) Acid shock proteins (synthesis of regulatory proteins triggered by low pH, e.g. DNA binding proteins)
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Temperature Affects growth kinetics and gene expression (e.g. motility to virulence)
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This note was uploaded on 04/05/2010 for the course ENVH 451 taught by Professor Meschke during the Fall '09 term at University of Washington.

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Lec_11_Foodborne Factors - Factors Affecting Foodborne...

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