Gentle friends: here's the answer to the questions I raised a few weeks ago:


From: Elizabeth Andress

"Why can't we substitute ascorbic acid (vitamin C) for citric acid (sour
salt) or lemon juice for acidifying canned goods? And if it is possible,
what is the substitution rate?"


The quick answer is that it cannot be substituted because there are no
established levels to provide the proper pH control in the canned foods
where we have it required to assure safe boiling water processing instead of
pressure processing.

Ascorbic acid is not as efficient of an acidifier for the needed purposes
(decreasing the pH of the food tissue). It is more expensive (in pure form)
and the economics would then be compounded by needing to use more. For
acidifying tomatoes, for example, the researchers worked out citric acid,
lemon juice and vinegar options, but did not determine an acidification
amount for ascorbic acid. There is no general conversion factor; different
amounts would have to be tested in the actual food to be acidified. Foods
contain natural components that can cause buffering with different acids in
solution, and thereby prevent desired pH changes until a threshold is
reached.

I was not in the profession when the tomato acidification studies were done,
but there could have also been some decision-making related to the fact that
pure ascorbic acid was not very available to consumers so it was not
considered. Three acidulants that were known to be effective food acidifiers
and available to consumers were used. It is my understanding, however, that
the reasoning has mostly to do with the fact that it is (and was) known that
ascorbic acid is not known to be an effective acidifier in the foods being
studied, fairly large amounts would be needed and there is a substantial
cost difference compared to the chosen compounds.

Citric acid is by far the most preferred and commonly used acidulant in the
food processing and food canning industry.

(And on the other hand, for many foods, ascorbic acid is a more effective
anti-darkening agent than citric acid.)

Elizabeth

Elizabeth L. Andress, Ph.D.
Project Director, National Center for HFP
Professor and Extension Food Safety Specialist
Department of Foods and Nutrition
The University of Georgia
208 Hoke Smith Annex
Athens, GA 30602-4356
Phone: (706) 542-3773
FAX: (706) 542-1979