Citric acid powder is used in food preparation and canning, pharmaceuticals and water softening. The most common home use is in preventing discoloration in canned fruits and vegetables. Citric acid occurs naturally in many fruits and vegetables, with higher concentrations in lemons and limes. Citric acid should not be confused with ascorbic acid, contained in many vitamin C tablets.
Decide how much citric acid you need. If you are canning, you will need approximately 1 tbsp. for every gallon of water needed for canning, not counting the water used in the canner itself.
Check your local supermarket. During the normal canning season, many supermarkets carry powdered citric acid in the canning section of the store.
Check with your local pharmacy. Many full service drug stores and pharmacies carry powdered citric acid year round. You may have to ask at the prescription counter because it may be kept behind the counter and not on the open store shelves.
Check your local health food store or natural vitamin shop. Both carry citric acid, in pill or bulk form.
Buy citric acid powder in bulk from a supplier such as Bulk Foods. (See the Resource section for website link.) Citric acid is available in 1-, 5- and 50-lb. quantities. It can also be purchased from online retailers.
Citric acid doesn't work as well as ascorbic acid for preventing food discoloration. Many products used in canning are made from a combination of the two acids.
Powdered citric acid contains no vitamins or calories.