Peterson, W. H. Forms of Sulfur in Plant Materials and Their Variation with Soil Supply. J. Am. Chem. Soc. 36: 1290 (1914).

Peterson, W. H., and Hoppert, C. A. The Loss of Mineral and Other Constituents from Vegetables by Various Methods of Cooking. J. Home Econ. 17: 265 (1925).

Pratt, O. B., and Swartout, G. O. Fruit and Vegetable Pigments as Indicators. Science 71: 486 (1930).

Rahn, O. Bacteriological Studies of Brine Pickles. The Canner 31: 13, June (1935).

Rider, A. E. The Oxalic Acid Content of Vegetables Used as Greens. J. Home Econ. 22: 309 (1930).

Sale, J. W., and Badger, C. H. Contamination of Beverages and Other Foods with Zinc. Ind. Eng. Chem. 16: 164 (1925).

Schorger, A. W. The Chemistry of Cellulose and Wood. McGraw-Hill Co. (1926).

Sherman, H. C. Chemistry of Food and Nutrition. Macmillan & Co. (1933).

Shibita, K., Nagar, I., and Kishida, M. The Occurrence and Physiological Significance of Flavone Derivatives in Plants. J. Biol. Chem. 28: 93 (1916).

Shilling, I. M. The Formation of Hydrogen Sulfide in the Cooking of Vegetables. Master's Thesis. University of Chicago (1923). Personal communication.

Simpson, J., and Halliday, E. G. The Behavior of Sulfur Compounds in Vegetables on Cooking. Abstracts of Reports of Research. Food and Nutrition Section. Asheville, N. C. June (1927) and J. Home Econ. 20: 121 (1928).

Snyder, E. B. Some Factors Affecting the Cooking Quality of the Pea and Great Northern Types of Dry Beans. Research Bull. 85. Agri. Expt. Sta., Neb. (1936).'

Steinbarger, M. The Effect of Salt upon the Loss of Iron in Cooking Vegetables. Unpublished Thesis (M. A.) University of Missouri, Columbia, Mo. (1923). Courtesy of Miss Steinbarger.

Stevenson, A. E. Discoloration in Canned Foods. Canning Age 5: 951 (1924).

Stevenson, F. J., and Whitman, E. F. Cooking Quality of Certain Potato Varieties as Influenced by Environment. Am. Potato J. 12: 41 (1935).

Swalley, M. Potato Chips. Special Problem. Unpublished. Iowa State College, Ames (1932).

Sweetman, M. D. The Physico-Chemical Changes Produced by the Cooking of Potatoes. Am. Potato J. 10: 169 (1933).

Thatcher, R. W. Chemistry of Plant Life. McGraw-Hill Co. (1921).

Van der Marel. The Causes of Hardening of Peas During Boiling. Chemical Abs. 16: 1116 (1922), from Pharm. Weekblad 59: 89 (1922).

Wheldale, M. The Anthocyanin Pigments of Plants. Cambridge University Press (1916).

Whittemore, M., and Juschke, B. M. Certain Relationships of Potash Fertilization and Varieties of Potatoes to Table Value. Bull. 231. Agri. Expt. Sta., Rhode Island (1933).

Williams, K. I. The Chemical Composition of Cooked Vegetables. Ind. Eng. Chem. 5: 653 (1913).

Willstatter, R. Chlorophyll. J. Am. Chem. Soc. 37: 323. (1915).

Wright, R. C, Peacock, W. M., Whiteman, T. M., and Whiteman, E. M. The Cooking Quality, Palatability, and Carbohydrate Composition of Potatoes as Influenced by Storage Temperature. Technical Bull. 507. U. S. Dept. Agri. (1936).

Zerban, F. W. Relative Importance of Some Coloring Matters in Cane Juices and Sirups. Ind. Eng. Chem. 12: 744. (1915).

Zerban, F. W. The Role of Oxidases and Iron in the Color Changes of Sugar Cane Juice. Ind. Eng. Chem. 10: 814. (1918).

Experiment 17

A. To determine the effect of different methods of cooking on the color of green vegetables.

Use 1/8 pound (56 grams) of spinach, lettuce, Brussels sprouts, green beans cut in 1-inch strips, or green asparagus. Use 1 cup of water. Cook 10 to 25 minutes, the time depending upon the vegetable used, but decide upon the length of time the vegetable is to be cooked before experiments are started. Save the water left from each experiment to compare for color and flavor. Notice the texture of the vegetable.

1. Pour boiling water over the vegetable. Cook covered for the length of time agreed upon.

2. Repeat A1, but cook uncovered.

3. Add salt to the cooking water. Use 1/4 teaspoon per cup of water. Cook uncovered and start in boiling water.

4. Cook uncovered in boiling distilled water.

5. Cook uncovered in boiling distilled water to which 1/16 teaspoon of soda has been added.

6. Cook uncovered in boiling distilled water to which Y\ teaspoon of vinegar has been added.

7. Cook in a steamer.

8. Cook in a pressure cooker, 10 minutes at 15 pounds pressure.

9. Cook in milk.

If desired, some of the cooking water may be tested for iron and phosphates.

In which case is the green color of the vegetable best preserved? Is there any difference in the texture of the vegetables with soda and with vinegar added?

Vegetable used:

Time of cooking

Color of vegetable


Color and amount of water


Results and conclusions.

B. To determine the effect of different methods of cooking on the color of red vegetables.

Use red cabbage if it can be obtained. If it is not obtainable, use red onions or beets. Repeat the directions under A for cooking. Vegetable used:

C. To compare the effect of different methods of cooking on the color of yellow vegetables.

Use carrots or squash. Repeat the directions under A for cooking. Do not confuse caramelization of sugar by alkali with pigment change of color.

Vegetable used:

Compare the effect of acid and alkali on the green, red and yellow pigments found in vegetables. What is the effect of the soda on the texture? Of the vinegar? Which is the preferable way of cooking each of the different colored vegetables ?

Experiment 18

To determine the effect of alkaline and neutral water upon the color of white cereals and vegetables.

la. To 1 1/3 cups of boiling water add 1/4 cup of washed rice. Cook until tender. Add more boiling water if necessary during cooking. Remove about 1/2 of the cooked rice from the sauce pan and drain.

lb. To the rice remaining in the sauce pan from \a, add 1/8 to 1/16 of a teaspoon of cream of tartar. Cook 2 minutes and drain.