Addendum to my first post: Citric acid does not have the killing
capability of acetic acid because of the partial dissociation (ionization)
constant, pKa at equal pH's. This is because the antimicrobial activity
of the acid resides in the non-dissociated or undissociated molecules.
Citric acid has less of these molecules at equal pH's.
Based on equal pH values: We found acetic acid to be the best
antimicrobial we tested, followed by lactic acid, then citric acid, then
malic acid and the lest effective was hydrochloric acid (HCl). Note HCl
has no undissociated molecules at all.
Based on equal _molar_ concentrations: Citric acid is more inhibitory
than acetic acid. So, there _are_ different ways of looking at the
situation.
-----------------------------------
I'm surprised any acid at all works for your application.
1. Acid tolerant bacteria, yeast and molds _should_ not be inhibited
and should be eating up (spoiling) your protein.
2. Acid also denatures protein.
Why can't you use one of the other ("better") preservative systems?
Several others _are_ available.
See the (my) book:
Enigl, Davin C. and Kent M. Sorrells. In Press, 1996. Water Activity and
Self-Preserving Formulas. In: Preservative-Free and Self-Preserving
Cosmetic and Drug Products. Jon J. Kabara and Donald S. Orth, Eds.
Marcel Dekker, Inc. New York, NY.
As suggested before see my articles (or send me your snail mail address
and I will send them to you or anybody else who needs them.):
Sorrells, Kent M., Davin C. Enigl and John R. Hatfield. 1989. Effect of
pH, Acidulant, Time, and Temperature on the Growth and Survival of
Listeria monocytogenes. Journal of Food Protection 52: 571-573.
Sorrells, Kent M. and Davin C. Enigl. 1990. Effect of pH, Acidulant
Sodium Chloride and Temperature on the Growth of Listeria monocytogenes.
Journal of Food Safety 11: 31-37.
Davin
Davin C. Enigl, MS-MEAS, President-Microbiologist
HACCP Validations-sm Hazard Analysis and Critical Control Points for the
Food, Cosmetic, Pharmaceutical, and Nutritional Supplement Industry
Voice: (916) 989-8264, Fax: (916) 989-8205, Pager: (714) 725-7695
9040 Erle Blunden Way
Fair Oaks, CA 95628
November 15, 1996
2:18 pm
