Lecture%2018

Lecture%2018 - ACIDS AS FOOD PRESERVATIVES ACID AS FOOD...

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A CIDS AS F OOD P RESERVATIVES
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A CID AS F OOD P RESERVATIVES Use of pH to control growth of harmful microganisms = natural Foods resist degradation because native pH is low = inhibitory Fermented foods, resist spoilage because of the low pH
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P H E FFECTS ON M ICROBIAL G ROWTH AND S URVIVAL A) pH limits-the general picture As with temperature and a W microbes have limits of tolerable pH Group microbes based on response to pH
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1. Optimal range is 2-3 pH units, exposure to pH above or below optimal adversely affects growth and survival Cells exposed to pH extremes beyond limits for growth are actually killed 2. Yeasts and molds have greater tolerance of pH extremes than bacteria Adjustment of pH is more effective in the control of bacteria than in control of yeasts and molds
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3. Bacteria capable of fermentation exhibit a greater tolerance of pH below optimal than of pH above optimal More tolerant of low pH than bacteria capable of respiration but not fermentation Lower pH selects for fermentative bacteria over aerobic respiratory bacteria
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M OST F OODS H AVE P H V ALUES B ELOW 7
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M ICROBIAL G ROUPS : A CID T OLERANCE
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This document was uploaded on 03/29/2010.

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Lecture%2018 - ACIDS AS FOOD PRESERVATIVES ACID AS FOOD...

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