If a food that is to be fried contains much water, what happens to the water when placed in the hot fat? Explain why it is better to leave the potatoes whole rather than cut them into pieces for cooking. Why is it especially necessary to dry the fish and potato mixture before frying?
What ingredient do Fish Balls contain that hardens immediately on being heated? Of what advantage is this ingredient in mixtures that are to be fried?
What is the price per package of codfish? What is the weight and measure of a package?
LESSON XXXVI
FAT AS A FRYING MEDIUM—DIGESTION OF FAT
EXPERIMENT 36: ACTION OF OIL AND WATER.—Pour a little corn or cottonseed oil into a test tube, add the same quantity of water, and shake the tube. Set the tube aside for a minute and examine. Which material rises to the top? Is oil soluble in water? What application can be made from this concerning the effectiveness of cleaning the fat of meats with water?
EXPERIMENT 36: EMULSION OF FAT.—In a test tube put a bit of soap and 2 tablespoonfuls of water. Heat until the soap is melted. Add 1/2 teaspoonful of vegetable oil. Shake the mixture and then examine. What familiar food does the mixture look like? Set the tube aside for a minute. Does the oil rise to the top as in Experiment 35? The fat is in an emulsified condition.
BREAKING UP OF FATS.—Fats and oils are not soluble in any substance found in the digestive juices, but they are acted upon by an enzyme [Footnote 41: Steapsin or lipase is the enzyme found in the pancreatic juice which acts upon fat.] and by an alkaline substance found in the pancreatic juice. The enzyme breaks up some of the fat into a fatty acid [Footnote 42: Fatty acids are substances related to fats; they have certain acid properties.] and glycerin.
During digestion, fat is emulsified, i.e. divided into tiny globules which do not coalesce.
When a fat is emulsified, it often looks like milk. (Milk contains fat in an emulsified form; the fat separates, however, by standing and rises to the top to form cream.) Fats can be emulsified by several different substances. A soap solution is one of the substances that will emulsify fats. (The action of soap solution in emulsifying fat was shown in Experiment 36.)