Canning Certain Vegetables with Hydrochloric Acid R. C. BURRELL, ESTHER M. JOHNSON, BEVERLEE J. RICE, and PHYLLIS J. SOHN The Ohio State University, Columbus, Ohio
C
ANNING the surplus products of war gardens has presented a problem due to the lack of pressure cookers, since the majority of the common vegetables, with the exception of tomatoes, have too high a pH to obviate the danger of bacterial spoilage, even botulism, unless pressure sterilization is employed. According to Shrader (4) Colostridium botulinum grows best a t a neutral or 'slightly alkaline reaction, although slight growth may occur at pH values of 5.0 or slightly less. The State Board of Health of California has established pH 4.5 as the dividing line between acid and nonacid foods (1, a). A relatively high acidity in the canned product also contributes to the conservation of both vitamin C (1,b) and carotene (3). I t was therefore deemed of interest to investigate the possibilities of the use of acid in the canning of vegetables with respect to: 1. Finding an acid that would not give an undesirable flavor to the canned product; 2. Findine - a suitable concentration to use under actual canning conditions; 3. Determining what the effects of the acid are on the quality of the product when subsequently used as food. EXPERIMENTAL PROCEDURE
approximately 1 gram) was found to be the right quantity to remove the sour taste and yet not quite neutralize the product (which, if done, would cause a more rapid destruction of vitamin C during the heating preliminary to serving). The beans, after neutralization by the baking soda, had a pH of 6.2; the vegetable mixture, 4.9 to 5.0. The exact canning procedures were as follows: The snap beans cut in one-inch lengths and blanched, or the vegetable mixture, either blanched or not, were packed loosely in pint Mason jars. One-half teaspoon of salt was added to each jar, then 25 cc. of 0.5 N hydrochloric acid, and finally sufficient water to bring the level of liquid up to the base of the rim. The jars were closed with No. 10 glass-top"'Presto" closures (unscrewing the band one-fourth turn before processing) and placed in a water bath. They were allowed to process for 45 minutes of active To prepare for serving, the Contents of the jar were em~tiedinto a sauceDan and water added as desired. One-fourth teaspoon of baking soda was added to each Sample and heating was continued for or minutes, The addition of the contents of one small envelope of "G. Washington's Instant B r o t h powder makes a verv valatahle vegetable sou^ from the vegetable mixture. In a series of experiments, determinations of the vitamin C content ( 2 ) of the original vegetable mixture, the stored product, and the product prepared for s e n ing were made. Due to the lack of homogeneity of the product the results obtained from separate samples were variable. However, they confirmed the already established idea that acidity is favorableto the preservation of the vitamin C content of a foodstuff. Fifty cans of the vegetable mixture and forty cans of snap beans were stored for periods of six months to one year without any spoilage occurring.
..
-
-
Two vegetable products were investigated, green snap beans and a mixture of vegetables suitable for vegetable soup. For the latter, the following proportions by volume were used: 2 parts shredded cabbage; 1 part tomatoes; 1 part sweet corn; 1 part chopped celery; ''2 part diced carrots; '/z part chopped onions; and ' / ' I part chopped parsley. With the beans, blanching was carried out with boiling water for three minUtes. For most of the experiments, the vegetable mixture was prepared unblanched. Hydrochloric was selected as the acid, since in the subsequent preparation of the canned product for the table the addition of a little baking soda not only removed LITERATURE CITED the sour taste but merely produced a little more ordinary salt asthe result of such neutralization. After trials (1) ( a ) Cnusss, W. V., "Commercial Fruit and Vegetable Products," 2nd Ed.. McGraw-Hill Book C o . , Inc., New York, of various concentrations it was found that 25 cc. of 1938, p. 121. ( b ) Ibid., p. 720. 0.5 IV hydrochloric acid added to a one-pint can would (2) DUNNIGAN, M., M . LEWIS, AND M. R. S~ETLAR, *'Astudy OF the ascorbic acid control of the diet commonly prescribed give a pH of 3.6 with the snap beans and a pH of 3.5 to for patients with gastric ulcers," Ohio J. Sci., 44, 123 3.7 with the vegetable mixture. Such pH values are (1941). unfavorable to the activity of most enzymes as well as (3) SHETLAR, Unpublished data. C. L., A N D M. R. SHETLAR. Dept. of Agricultural Chemistry, The Ohio State Unito the growth of bacteria. When preparing the product versity (1944). baking use, One-quarter of a (4) SKRADE~, J. H., "Food Control: Its Public-Health Aspects," from a kitchen measuring spoon (weight of NaHC03 John Wiley and Sons, Inc, New York, 1939. 409
