b. Apply the following tests to residue and filtrate re- spectively : Biuret, page 85 Coagulation on heating Xanthoproteic, page 85 Fehling-Benedict solution, page 13 c. What are your conclusions ? Milk (Sour) 103. — Have ready milk which has been sour i day, 2 days, 3 days. a. Test equal volumes of each with litmus paper. b. Neutralize each with -a solution of baking soda, testing with litmus paper. c. Note the amount of soda required in each instance. MILK, CREAM, AND BUTTER 87 104. - - a. Heat equal portions of each specimen of sour milk in a double boiler. b. Note the clotting which appears. c. Which clots quickest and in largest quantity? d. To what is this due ? 105. - - a. Add salt to each portion in double boiler in the propor- tion of | tsp. to i c. of sour milk. b. Note the effect. c. How do you explain the result ? 106. - - Strain the clotted masses from Expt. 105 through wet cheese- cloth and allow to hang undisturbed until nitrate no longer drips. Test as usual with : Biuret, page 85 Xanthoproteic, page 85 Coagulation on heating Fehling-Benedict solution, page 13 107. - - a. Compare the cheese obtained in Expt. 106 with that made from sweet milk. b. Note the difference in consistency, texture, and flavor. c. To what is this due? 108. - Test each specimen of sour milk with litmus paper. a. Which turns the paper quickest ? b. What acid is present in sour milk? c. How does it originate ? (Leach, Food Inspection and Analysis?) d. With the litmus paper still in the milk, add sufficient baking soda to neutralize the acid. Is a physical or chemical change produced ? e. What is the gas given off after the soda is added ? /. In what food products is this principle applied? g. Test i c. of sour milk with litmus paper and determine how much soda it is necessary to add to neutralize the acid. //. Take an average of the results of the class and com- pare with the amount usually given in cook books. How does it compare ? 88 LABORATORY MANUAL OF FOODS AND COOKERY 109. - - a. Test i c. of sweet milk with litmus and add sufficient vinegar to produce the same intensity of color as in 108, g. b. Neutralize a part of this milk with soda. c. Compare the amount of soda needed with 108, g. d. Prepare gingerbread, using the milk in 108, g in one in- stance and that in 109, a in the second instance. e. Compare the two products. Is one preferable to the other? /. Repeat g and heat the milk until the curd separates out. Compare this curd with that of normally sour milk and also with the curd made with junket and sweet milk. g. What are the noticeable differences and to what are they due? h. What sources of sour milk and curd have we? Cheese Cheese has already been prepared with sweet and sour milk. Test now commercial cheese. 110.- -Prepare three equal weights of American cheese, A, B, C. Heat A in a saucepan, B in a double boiler, and C in hot milk. Com- pare results. 111. - - Prepare two equal weights of American cheese, A, B. Cut into small pieces and put into equal volumes of warm milk. a. Continue heating A in a double boiler until cheese is melted. Examine consistency of mixture.

AI-modernized reading of the original text

b. Apply the following tests to residue and filtrate respectively : Biuret, page 85 Coagulation on heating Xanthoproteic, page 85 Fehling-Benedict solution, page 13 c. What are your conclusions ? Milk (Sour) 103. — Have ready milk which has been sour i day, 2 days, 3 days. a. Test equal volumes of each with litmus paper. b. Neutralize each with -a solution of baking soda, testing with litmus paper. c. Note the amount of soda required in each instance. 104. - - a. Heat equal portions of each specimen of sour milk in a double boiler. b. Note the clotting which appears. c. Which clots quickest and in largest quantity? d. To what is this due ? 105. - - a. Add salt to each portion in double boiler in the proportion of | tsp. to i c. of sour milk. b. Note the effect. c. How do you explain the result ? 106. - - Strain the clotted masses from Expt. 105 through wet cheesecloth and allow to hang undisturbed until nitrate no longer drips. Test as usual with : Biuret, page 85 Xanthoproteic, page 85 Coagulation on heating Fehling-Benedict solution, page 13 107. - - a. Compare the cheese obtained in Expt. 106 with that made from sweet milk. b. Note the difference in consistency, texture, and flavor. c. To what is this due? 108. - Test each specimen of sour milk with litmus paper. a. Which turns the paper quickest ? b. What acid is present in sour milk? c. How does it originate ? (Leach, Food Inspection and Analysis?) d. With the litmus paper still in the milk, add sufficient baking soda to neutralize the acid. Is a physical or chemical change produced ? e. What is the gas given off after the soda is added ? /. In what food products is this principle applied? g. Test i c. of sour milk with litmus paper and determine how much soda it is necessary to add to neutralize the acid. //. Take an average of the results of the class and compare with the amount usually given in cook books. How does it compare ? 109. - - a. Test i c. of sweet milk with litmus and add sufficient vinegar to produce the same intensity of color as in 108, g. b. Neutralize a part of this milk with soda. c. Compare the amount of soda needed with 108, g. d. Prepare gingerbread, using the milk in 108, g in one instance and that in 109, a in the second instance. e. Compare the two products. Is one preferable to the other? /. Repeat g and heat the milk until the curd separates out. Compare this curd with that of normally sour milk and also with the curd made with junket and sweet milk. g. What are the noticeable differences and to what are they due? h. What sources of sour milk and curd have we? Cheese Cheese has already been prepared with sweet and sour milk. Test now commercial cheese. 110.- -Prepare three equal weights of American cheese, A, B, C. Heat A in a saucepan, B in a double boiler, and C in hot milk. Compare results. 111. - - Prepare two equal weights of American cheese, A, B. Cut into small pieces and put into equal volumes of warm milk. a. Continue heating A in a double boiler until cheese is melted. Examine consistency of mixture.

A laboratory manual of foods and cookery