External Concentration of Organic Acid Anions and pH: Key Independent Variables for Studying How Organic Acids Inhibit Growth of Bacteria in Mildly Acidic Foods

Although the mechanisms by which organic acids inhibit growth of bacteria in mildly acidic foods are not fully understood, it is clear that intracellular accumulation of anions is a primary contributor to inhibition of bacterial growth. We hypothesize that intracellular accumulation of anions is dri...

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Bibliographic Details
Published in:Journal of food science 2009, Vol.74 (1), p.R12-R15
Main Authors: Carpenter, C.E, Broadbent, J.R
Format: Article
Language:English
Subjects:
acid tolerance
acids
Acids - pharmacology
Anions
antibacterial properties
Bacteria
Bacteria - drug effects
Bacteria - growth & development
bacterial contamination
Bacteriology
beverages
Biological and medical sciences
Food
food biopreservation
food biopreservatives
food contamination
Food industries
Food Microbiology
food pathogens
food preservation
food preservatives
Food science
foods
Fundamental and applied biological sciences. Psychology
Hydrogen-Ion Concentration
Hypotheses
Ions
Kinetics
Listeria monocytogenes
Listeria monocytogenes - drug effects
Listeria monocytogenes - growth & development
Mathematics
mildly acidic foods
minimum inhibitory concentration
Models, Biological
new methods
organic acids
organic acids and salts
Physical growth
predictive microbiology
Predictive Value of Tests
probiotics
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Summary:Although the mechanisms by which organic acids inhibit growth of bacteria in mildly acidic foods are not fully understood, it is clear that intracellular accumulation of anions is a primary contributor to inhibition of bacterial growth. We hypothesize that intracellular accumulation of anions is driven by 2 factors, external anion concentration and external acidity. This hypothesis follows from basic chemistry principles that heretofore have not been fully applied to studies in the field, and it has led us to develop a novel approach for predicting internal anion concentration by controlling the external concentration of anions and pH. This approach overcomes critical flaws in contemporary experimental design that invariably target concentration of either protonated acid or total acid in the growth media thereby leaving anion concentration to vary depending on the pKa of the acids involved. Failure to control external concentration of anions has undoubtedly confounded results, and it has likely led to misleading conclusions regarding the antimicrobial action of organic acids. In summary, we advocate an approach for directing internal anion levels by controlling external concentration of anions and pH because it presents an additional opportunity to study the mechanisms by which organic acids inhibit bacterial growth. Knowledge gained from such studies would have important application in the control of important foodborne pathogens such as Listeria monocytogenes, and may also facilitate efforts to promote the survival in foods or beverages of desirable probiotic bacteria.
ISSN:0022-1147
1750-3841
DOI:10.1111/j.1750-3841.2008.00994.x