Human Foods and Their Nutritive Value

Directions for Measuring.—Reagents are measured in graduated cylinders (see Fig. 74). When the directions call for the addition of 5 or 10 cc. of a reagent, unless so directed it is not absolutely necessary to measure the reagent in a measuring cylinder. A large test tube holds about 30 cc. of water. Measure out 5 cc. of water and transfer it to a large test tube. Note its volume. Add approximately 5 cc. of water directly to the test tube. Measure it. Repeat this operation until you can judge with a fair degree of accuracy the part of a test tube filled by 5 cc. In the experiments where a burette is used for measuring reagents, the burette is first filled with the reagent by means of a funnel. The tip of the burette is allowed to fill before the readings are made, which are from the lowest point or meniscus. When reagents are removed from bottles, the stopper should be held between the first and second fingers of the right hand (see Fig. 75). Hold the test tube or receptacle that is to receive the reagent in the left hand. Pour the liquid slowly until the desired amount is secured. Before inserting the stopper, touch it to the neck of the bottle to catch the few drops on the edge, thus preventing their streaking down the sides of the bottle on to the shelf. Replace the bottle in its proper place. Every precaution should be taken to prevent contamination of reagents.

Fig. 76.—Microscope and Accessories.

1, eye-piece or ocular; 2, objective; 3, stage; 4, cover glass; 5, slide; 6, mirror.

Use of the Microscope.—Special directions in the use of the microscope will be given by the instructor. The object or material to be examined is placed on a microscopical slide. Care should be exercised to secure a representative sample, and to properly distribute the substance on the slide. If a pulverized material is to be examined, use but little and spread it in as thin a layer as possible. If a liquid, one or two drops placed on the slide will suffice. The material on the slide is covered with a cover glass, before it is placed on the stage of the microscope. In focusing, do not allow the object glass of the microscope to come in contact with the cover glass. Focus upward, not downward. Special care should be exercised in focusing and in handling the eye-piece and objective. A camel's-hair brush, clean dry chamois skin, or clean silk only should be used in polishing the lenses. Always put the microscope back in its case after using.

Experiment No. 1

Water in Flour

Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if the ash is to be determined on the same sample.) Place in it about 2 gm. of flour; record the weight; then place the dish in the water oven for at least 6 hours. After drying, weigh again, and from the loss of weight calculate the per cent of water in the flour. (Weight of flour and dish before drying minus weight of flour and dish after drying equals weight of water lost. Weight of water divided by weight of flour taken, multiplied by 100, equals the per cent of water in the flour.)

How does the amount of water you obtained compare with the amount given in the tables of analysis?

Experiment No. 2

Water in Butter

Carefully weigh a clean, dry aluminum dish, place in it about 2 gms. of butter, and weigh again. Record the weights. Place the dish containing butter in the water oven for 5 or 6 hours and then weigh. The loss in weight represents the water in the butter. Calculate the per cent of water. Care must be taken to get a representative sample of the butter to be tested; preferably small amounts should be taken with the butter trier from various parts of the package.

Experiment No. 3

Ash in Flour

Place the porcelain dish containing flour from the preceding experiment in a muffle furnace and let it remain until the organic matter is completely volatilized. Cool, weigh, and determine the per cent of ash. The flour should be burned at the lowest temperature necessary for complete combustion.

Experiment No. 4

Nitric Acid Test for Nitrogenous Organic Matter

To 3 cc. of egg albumin in a test tube add 2 cc. of HNO₃ (conc.) and heat. When cool add NH₄OH. The nitric acid chemically reacts upon the albumin, forming yellow xanthoprotein. What change occurs in the appearance of the egg albumin when the HNO₃ is added? Is this a physical or chemical change? What is the name of the compound formed? What change occurs on adding NH₄OH?

Experiment No. 5

Acidity of Lemons

With a pipette measure into a small beaker 2 cc. of lemon juice. Add 25 cc. of water and a few drops of phenolphthalein indicator. From the burette run in N/10 KOH solution until a faint pink tinge remains permanently. Note the number of cubic centimeters of KOH solution required to neutralize the citric acid in the lemon juice. Calculate the per cent of citric acid.

(1 cc. of N/10 KOH solution equals 0.00642 gm. citric acid. 1 cc. of H₂O weighs 1 gm. Because of sugar and other matter in solution 1 cc. of lemon juice weighs approximately 1.03 gm.)

1. What is the characteristic acid of lemons? 2. What is the salt formed when the lemon juice is neutralized by the KOH solution? 3. Describe briefly the process for determining the acidity of lemon juice. 4. What per cent of acidity did you obtain? 5. How does this compare with the acidity of vinegar?

Experiment No. 6

Influence of Heat on Potato Starch Grains

With the point of a knife scrape slightly the surface of a raw potato and place a drop of the starchy juice upon the microscopical slide. Cover with cover glass and examine under the microscope.

In the evaporating dish cook a small piece of potato, then place a very small portion upon the slide, and examine with the microscope.

Make drawings of the starch grains in raw and in cooked potatoes.

Experiment No. 7

Influence of Yeast on Starch Grains

Moisten a small portion of the dough prepared with yeast and with the stirring rod place a drop of the starchy water upon the slide. Cover with cover glass and examine under the microscope.

Repeat, examining a drop of starchy water washed from flour.

Make drawing of wheat starch grain in flour and in dough prepared with yeast.

Experiment No. 8

Mechanical Composition of Potatoes

Wash one potato. Weigh, then peel, making the peeling as thin as possible. Weigh the peeled potato and weigh the peeling or refuse. Calculate the per cent of potato that is edible and the per cent that is refuse.

Experiment No. 9

Pectose from Apples

Reduce a small peeled apple to a pulp. Squeeze the pulp through a clean cloth into a beaker. Add 10 cc. H₂O and heat on a sand bath to coagulate the albumin. Filter, adding a little hot water if necessary. To the filtrate add 5 cc. alcohol. The precipitate is the pectose material.

1. Is the pectose from the apple soluble? 2. Is it coagulated by heat? 3. Is it soluble in alcohol?

Experiment No. 10

Lemon Extract

To 5 cc. of the extract in a test tube add an equal volume of water. A cloudy appearance indicates the presence of lemon oil. If the solution remains clear after adding the water, the extract does not contain lemon oil.

Why does the extract containing lemon oil become cloudy on adding water?

Experiment No. 11

Vanilla Extract

Pour into a test tube 5 cc. of the extract to be tested. Evaporate to one third. Then add sufficient water to restore the original volume. If a brown, flocculent precipitate is formed, the sample contains pure vanilla extract. Resin is present in vanilla beans and is extracted in the essence. The resin is readily soluble in 50 per cent alcohol. If the alcohol is removed from the extract, the excess of resin is precipitated, or if free from alkali, it may be precipitated by diluting the original solution with twice its volume of water. Test the two samples and compare.

(Adapted from Leach, "Food Inspection and Analysis.")

1. Describe the appearance of each sample after evaporating and adding water. 2. Which sample contains pure vanilla extract? 3. State the principle underlying this test.

Experiment No. 12

Testing Olive Oil for Cotton Seed Oil

Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with cotton, and heat in a bath of boiling saturated brine for 15 minutes. If cotton seed oil is present, a deep red or orange color is produced. Test two samples and compare.

Halphen's Reagent.—Mix equal volumes of amyl alcohol and carbon disulphid containing about one per cent of sulphur in solution.

(Adapted from Leach, "Food Inspection and Analysis.")

Experiment No. 13

Testing for Coal Tar Dyes

Dilute 20 to 30 cc. of the material to 100 cc.; boil for 10 minutes with 10 cc. of a 10 per cent solution of potassium bisulphate and a piece of white woolen cloth which has previously been boiled in a 0.1 per cent solution of NaOH and thoroughly washed in water. Remove the cloth from the solution, wash in boiling water, and dry between pieces of filter paper. A bright red indicates coal tar dye. If the coloring matter is entirely from fruit, the woolen cloth will be either uncolored or will have a faint pink or brown color which is changed to green or yellow by ammonia and is not restored by washing. This is the Arata test.

(Adapted, Winston, Conn. Experiment Station Report.)

1. Describe Arata's wool test for coal tar dyes. 2. What is the appearance of the woolen cloth when the coloring matter is entirely from fruit? 3. What effect has NH₄OH upon the color? 4. Why is NaOH used? 5. Why may not cotton cloth be used instead of woolen? 6. What can you say of the use of coal tar dyes in foods?

Experiment No. 14

Determining the Per Cent of Skin in Beans

Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and ½ gm. of baking soda. Boil 10 minutes or until the skins are loosened, then drain off the water. Add cold water and rub the beans together till the skins slip off. Collect the skins, place on a watch glass and dry in the water oven for ½ hour. Weigh the dried skins and calculate the per cent of "skin."

1. What does the soda do? 2. What effect would hard limewater have upon the skins? 3. How does removal of skins affect food value of beans and digestibility?

Experiment No. 15

Extraction of Fat from Peanuts

Shell three or four peanuts and with the mortar and pestle break them into small pieces. Place in a test tube and pour over them about 10 cc. of ether. Cork the test tube and allow it to stand 30 minutes, shaking occasionally. Filter on to a watch glass and let stand until the ether evaporates, and then observe the fat.

1. What is the appearance of the peanut fat? 2. What is the solvent of the fat? 3. What becomes of the ether? 4. Why should the peanuts be broken into small pieces?

Experiment No. 16

Microscopic Examination of Milk

Place a drop of milk on a microscopical slide and cover with cover glass. Examine the milk to detect impurities, as dust, hair, refuse, etc. Make drawings of any foreign matter present.

Experiment No. 17

Formaldehyde in Cream or Milk

To 10 cc. of milk in a casserole add 10 cc. of the acid reagent. Heat slowly over the flame nearly to boiling, holding the casserole in the hand and giving it a slight rotary movement while heating. The presence of formaldehyde is indicated by a violet coloration varying in depth with the amount present. In the absence of formaldehyde the solution slowly turns brown.

Acid Reagent.—Commercial hydrochloric acid (sp. gr. 1.2) containing 2 cc. per liter of 10 per cent ferric chlorid.

(Adapted from Leach, "Food Inspection and Analysis.")

1. How may the presence of formaldehyde in milk be detected? 2. Why in this test is it necessary to use acid containing ferric chlorid? 3. Describe the appearance of the two samples of milk after adding the acid reagent and heating. 4. Which sample showed the presence of formaldehyde?

Experiment No. 18

Gelatine in Cream or Milk

To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric nitrate and about 40 cc. of H₂O. Let stand for a few minutes and filter. Filtrate will be cloudy if gelatine is present.

Add ½ cc. of a dilute solution of picric acid—a heavy yellow precipitate indicates gelatine.

Acid Mercuric Nitrate.—1 part by weight of Hg, 2 parts HNO₃ (sp. gr. 1.42). Dilute 25 times with water.

Experiment No. 19

Testing for Oleomargarine

Apply the following tests to two samples of the material:

Boiling or Spoon Test.—Melt the sample to be tested—a piece about the size of a chestnut—in a large spoon, hastening the process by stirring with a splinter. Then, increasing the heat, bring to as brisk a boil as possible and stir thoroughly, not neglecting the outer edges. Oleomargarine and renovated butter boil noisily, sputtering like a mixture of grease and water, and produce no foam, or but very little. Genuine butter boils with less noise and produces an abundance of foam.

Waterhouse Test.—Into a small beaker pour 50 cc. of sweet milk. Heat nearly to boiling and add from 5 to 10 gms. of butter or oleomargarine. Stir with a glass rod until fat is melted. Then place the beaker in cold water and stir the milk until the temperature falls sufficiently for the fat to congeal. At this point the fat, if oleomargarine, can easily be collected into one lump by means of the rod; while if butter, it will granulate and cannot be collected.

(From Farmers' Bul. 131, U. S. Dept. of Agriculture.)

1. Name two simple tests for distinguishing butter and oleomargarine. 2. Describe these tests. 3. Why do butter and oleomargarine respond differently to these tests? 4. Are these tests based upon chemical or physical properties of the fats?

Experiment No. 20

Testing for Watering or Skimming of Milk

a. Fat Content of Milk by Means of Babcock Test.—Measure with pipette into test bottle 17.6 cc. of milk. Sample should be carefully taken and well mixed. Measure with cylinder 17.5 cc. commercial H₂SO₄ and add to milk in test bottle. (See Fig. 25.) Mix acid and milk by rotating the bottle. Then place test bottles in centrifugal machine and whirl 5 minutes. Add sufficient hot water to test bottles to bring contents up to about the 8th mark on stem. Then whirl bottles 2 minutes longer and read fat. Read from extreme lowest to highest point. Each large division as 1 to 2 represents a whole per cent, each small division 0.2 of a per cent.

b. Determining Specific Gravity by Means of Lactometer.—Pour 150 cc. of milk into 200 cc. cylinder. Place lactometer in milk and note depth to which it sinks as indicated on stem. Note also temperature of milk. For each 10° above 60° F. add 1 to the lactometer number, in order to make the necessary correction for temperature. For example, if milk has sp. gr. of 1.032 at temperature of 70°, it will be equivalent to sp. gr. of 1.033 at 60°. Ordinarily milk has a sp. gr. of 1.029 to 1.034. If milk has sp. gr. less than 1.029, or contains less than 3 per cent fat, it may be considered watered milk. If the milk has a high sp. gr. (above 1.035) and a low content of fat, some of the fat has been removed.

(For extended direction for milk testing see Snyder's "Dairy Chemistry.")

Experiment No. 21

Boric Acid in Meat

Cut into very small pieces 5 gms, of meat, removing all the fat possible. Place in an evaporating dish with 20 to 25 cc. of water to which a few drops of HCl have been added and warm slightly. Dip a piece of turmeric paper in the meat extract and dry. A rose-red color of the turmeric paper after drying (turned olive by a weak ammonia solution) is indicative of boric acid.

1. How may meat be tested for boric acid? 2. Why is HCl added to the water? 3. Why is the water containing the meat warmed slightly? 4. What is the appearance of the turmeric paper after being dipped in the meat extract and dried? 5. What change takes place when it is moistened with ammonia, and why?

Experiment No. 22

Microscopic Examination of Cereal Starch Grains

Make a microscopic examination and drawings of wheat, corn, rice, and oat starch grains, comparing them with the drawings of the different starch grains on the chart. If the material is coarse, pulverize in a mortar and filter through cloth. Place a drop or two of the starchy water on the slide, cover with a cover glass, and examine.

Experiment No. 23

Identification of Commercial Cereals

Examine under the microscope two samples of cereal breakfast foods, and by comparison with the wheat, corn, and oat starch grains previously examined tell of what grains the breakfast foods are made and their approximate food value.

Experiment No. 24

Granulation and Color of Flour

Arrange on glass plate, in order of color, samples of all the different grades of flour. Note the differences in color. How do these differences correspond with the grades of the flour? Examine the flour with a microscope, noting any coarse or dark-colored particles of bran or dust. Rub some of the flour between the thumb and forefinger. Note if any granular particles can be detected.

Experiment No. 25

Capacity of Flour to absorb Water

Weigh out 15 gms. of soft wheat flour into an evaporating dish; then add from burette a measured quantity of water sufficient to make a stiff dough. Note the amount of water required for this purpose. Repeat the operation, using hard wheat flour.

1. How may the absorptive power of a flour be determined? 2. To what is it due? 3. Why do some flours absorb more water than others?

Experiment No. 26

Acidity of Flour

Weigh into a flask 20 gms. of flour and add 200 cc. distilled water. Shake vigorously. After letting stand 30 minutes, filter and then titrate 50 cc. of the filtrate against standard KOH solution, using phenolphthalein as indicator, 1 cc. of the alkali equals 0.009 gms. lactic acid. Calculate the per cent of acid present.

1. How may the acidity of a flour be determined? 2. The acidity is expressed in percentage amounts of what acid? 3. What per cent of acidity is found in normal flours? 4. What does a high acidity of a flour indicate?

Experiment No. 27

Moist and Dry Gluten

Weigh 30 gms. of flour into a porcelain dish. Make the flour into a stiff dough. After 30 minutes obtain the gluten by washing, being careful to remove all the starch and prevent any losses. Squeeze the water from the gluten as thoroughly as possible. Weigh the moist gluten and calculate the per cent. Dry the gluten in the water oven and calculate the per cent of dry gluten.

Experiment No. 28

Gliadin from Flour

Place in a flask 10 gms. of flour, 30 cc. of alcohol, and 20 cc. of water. Cork the flask and shake, and after a few minutes shake again. Allow the alcohol to act on the flour for an hour, or until the next day. Then filter off the alcohol solution and evaporate the filtrate to dryness over the water bath. Examine the residue; to a portion add a little water; burn a small portion and observe odor.

1. Describe the appearance of the gliadin. 2. What was the result when water was added? 3. When burned, what was the odor of the gliadin, and what does this indicate? 4. What is gliadin?

Experiment No. 29

Bread-making Test

Make a "sponge" by mixing together:

• 12 gm. sugar,
• 12 gm. yeast (compressed),
• 4 gm. salt,
• 175 cc. water (temp. 32° C.).

Let stand ½ hour at a temperature of 30° C. In a large bowl, mix with a knife or spatula 7.7 gms. of lard with 248.6 gms. of flour. Then add 160 cc. of the "sponge," or as much as is needed to make a good stiff dough, and mix thoroughly, using the spatula. With some flours as small a quantity as 150 cc. of sponge may be used. If more moisture is necessary, add H₂O. Keep at temperature of 30° C. Allow the dough to stand 50 minutes to first pulling, 40 minutes to second pulling, and 30 to 50 minutes to the pan. Let it rise to top of pan and then bake for ½ hour in an oven at a temperature of 180° C. One loaf of bread is made of patent flour of known quality as a standard for comparison, and other loaves of the flours to be tested. Compare the loaves as to size (cubic contents), color, porosity, odor, taste, nature of crust, and form of loaf.

Experiment No. 30

Microscopic Examination of Yeast

On a watch glass mix thoroughly a very small piece of yeast with about 5 cc. of water and then with the stirring rod place a drop of this solution on the microscopical slide, adding a drop of very dilute methyl violet solution. Cover with the cover glass and examine under the microscope. The living active cells appear colorless while the decayed and lifeless ones are stained. Yeast cells are circular or oval in shape. (See Fig. 46.)

(Adapted from Leach, "Food Inspection and Analysis.")

Experiment No. 31

Testing Baking Powders for Alum

Place about 2 gms. of flour in a dish with ½ gm. baking powder. Add enough water to make a dough and then 2 or 3 drops of tincture of logwood and 2 or 3 drops of ammonium carbonate solution. Mix well and observe; a blue color indicates alum. Try the same test, using flour only for comparison.

1. How do you test a baking powder for alum? 2. What difference in color did you observe in the test with the baking powder containing alum and in that with the flour only? 3. Why is the (NH₄)₂CO₃ solution used?

Experiment No. 32

Testing Baking Powders for Phosphoric Acid

Dissolve ½ gm. of baking powder in 5 cc. of H₂O and 3 cc. HNO₃. Filter and add 3 cc. ammonium molybdate. Heat gently. A yellow precipitate indicates phosphoric acid.

1. How do you test a baking powder for phosphoric acid? 2. What is the yellow precipitate obtained in this test?

Experiment No. 33

Testing Baking Powders for Ammonia

Dissolve ½ gm. of material in 10 cc. water; filter off any insoluble residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the gas given off with moistened turmeric paper. If NH₃ is present, the paper will be colored brown. Do not allow the paper to come in contact with the liquid or sides of the test tube. (Perform the tests on two samples of baking powder.)

1. How do you test a baking powder for ammonia? 2. Why do you add NaOH? 3. Why must you be careful not to let the turmeric paper touch the sides of the test tube or the liquid?

Experiment No. 34

Vinegar Solids

Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh and then evaporate over boiling water. To drive off the last traces of moisture dry in the water oven for an hour. Cool and weigh. Calculate the per cent of solids. Observe the appearance of the solids. Test both samples and compare.

1. How may the per cent of solids in vinegar be determined? 2. Describe the appearance of the solids from the good and from the poor sample of vinegar. 3. What is the legal standard for vinegar solids in your state?

Experiment No. 35

Specific Gravity of Vinegar

Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy liquids (sp. gr. 1 to 1.1) in the cylinder. Note the depth to which it sinks and the point registered on the scale on the stem. Note temperature of vinegar. Record specific gravity of vinegar.

1. What effect would addition of water to vinegar have upon its specific gravity? 2. What effect would addition of such material as sugar have upon specific gravity? 3. Why should the specific gravity of vinegar be fairly constant? 4. What would be the weight of 1000 cc. of vinegar calculated from the specific gravity?

Experiment No. 36

Acidity of Vinegar

Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few drops of phenolphthalein indicator. Run in standard KOH solution from a burette until a faint pink tinge remains permanently. Note the number of cubic centimeters of KOH solution required to neutralize the acid. Divide this number by 10, which will give approximately the per cent of acetic acid.

1. How may the per cent of acidity of vinegar be determined? 2. Why was phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar contain? 5. What is the legal requirement in this state for acetic acid in vinegar? 6. How did the acidity you obtained compare with this legal requirement?

Experiment No. 37

Deportment of Vinegar with Reagents

To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead sub-acetate and shake. Observe the precipitate. Lead sub-acetate precipitates mainly the malic acid which is always present in cider vinegar.

1. How may the presence of malic acid in a vinegar be detected? 2. Describe the precipitate. 3. What does malic acid in a vinegar indicate?

Experiment No. 38

Testing Mustard for Turmeric

Place 1 gm. of ground mustard on a small watch glass and moisten slightly with water. Add 2 or 3 drops of NH₄OH, stirring well with a glass rod. A brown color indicates turmeric present in considerable quantity.

Test a sample of good mustard and one adulterated with turmeric and compare the results.

Experiment No. 39

Examination of Tea Leaves

Soak a small amount of tea and unroll 8 or 10 of the leaves. Make a drawing of a tea leaf. Observe the proportion of stems in each of three samples of tea; also the relative proportion of large and small leaves. Observe if the leaves are even as to size and of a uniform color.

Experiment No. 40

Action of Iron Compounds upon Tannic Acid

Make an infusion of tea by placing 3 gms. of tea in 100 cc. of hot water and stirring well. Filter off some of the infusion and test 5 cc. with ferrous sulphate solution made by dissolving 1 gm. FeSO₄ in 10 cc. H₂O and filtering. Note the result.

1. What change in color did you observe when the ferrous sulphate solution was added to the tea infusion? 2. What effect would waters containing iron have upon the tea infusion?

Experiment No. 41

Identification of Coffee Berries

Examine Rio, Java, and Mocha coffee berries. Describe each. Note the characteristics of each kind of coffee berry.

Experiment No. 42

Detecting Chicory in Coffee

Fill a beaker with water and place about a teaspoonful of ground coffee on the surface. If much of the ground material sinks and it imparts a dark brown color to the lower portion of the liquid, it is an indication of the presence of chicory. Pure coffee floats on water. Chicory has a higher specific gravity than coffee.

1. How may the presence of chicory in ground coffee be detected? 2. Why does coffee float on the water while chicory sinks? 3. What effect does chicory have upon the color of water?

Experiment No. 43

Testing Hard and Soft Waters

Partially fill a large cylinder with very hard water. This may be prepared by dissolving 0.1 to 0.2 gm. calcium chloride in 500 cc. of ordinary water. Add to this a measured quantity of soap solution. Mix well and notice how many cubic centimeters of soap solution must be used before a permanent lather is formed, also notice the precipitate of "lime soap." Repeat this experiment, using either rain or distilled water, and compare the cubic centimeters of soap solution used with that in former test. Repeat the test, using tap water.

Soap Solution.—Scrape 10 gms. of castile soap into fine shavings and dissolve in a liter of alcohol, dilute with 1/3 water. Filter if not clear and keep in a tightly stoppered bottle.

1. Why is more soap required to form a lather with hard water than with soft water? 2. What is meant by "lime soap"? Describe its appearance. 3. How may hard waters be softened for household purposes?

Experiment No. 44

Solvent Action of Water on Lead

Put 1 gm. of clean bright lead shavings into a test tube containing 10 cc. of distilled water. After 24 hours decant the clear liquid into a second test tube, acidify slightly with HCL, and add a little hydrogen sulphid water. A black or brownish coloration indicates lead in solution.

(Adapted from Caldwell and Breneman, "Introductory Chemical Practice.")

Under what conditions may lead pipes be objectionable?

Experiment No. 45

Suspended Matter in Water

Place a drop of water on the microscopical slide, cover with cover glass, and examine with the microscope. Note the occurrence and appearance of any suspended matter in the water.

Experiment No. 46

Organic Matter in Water

Pour into the evaporating dish 100 cc. H₂O and evaporate to dryness over the sand bath. Ignite the solids. If the solids blacken when ignited, the water contains organic matter.

Experiment No. 47

Deposition of Lime by Boiling Water

Boil for a few minutes about 200 cc. of water in a flask. After the water is cool, note any sediment of lime or turbidity of the water due to expelling the carbon dioxid.

1. What is meant by a "hard" water? 2. What do the terms "temporary" and "permanent" hardness of water mean? 3. What acts as a solvent of the lime in water? 4. Why does boiling cause the lime to be deposited?

Experiment No. 48

Qualitative Tests for Minerals in Water

Test for Chlorids.—To 10 cc. of H₂O add a few drops of HNO₃ and 2 cc. of AgNO₃. A white precipitate indicates the presence of chlorids, usually in the form of sodium chlorid.

Test for Sulphates.—To 10 cc. of water add 2 cc. of dilute HCl and 2 cc. of BaCl₂. A cloudiness or the formation of a white precipitate indicates the presence of sulphates.

Test for Iron.—If a brown sediment is formed in water exposed to the air for some time, it is probably iron hydroxid. To 10 cc. of the water add a few drops of HNO₃, heat, and then add ½ cc. of NH₄CNS. A red color indicates the presence of iron.

Test for CaO and MgO.—To 10 cc. of H₂O add 5 cc. NH₄OH. If a precipitate forms, filter it off, and to the filtrate add 3 cc. NH₄Cl and 5 cc. (NH₄)₂C₂O₄. The precipitate is CaC{2}O₄, and the filtrate contains the magnesia. Filter and add 5 cc. Na₃PO₄ to precipitate MgNH₄PO₄.

1. How would you test a water to detect the presence of organic matter? 2. Name some mineral impurities often found in water. 3. Describe the test for chlorids; for sulphates; for iron; for lime; for magnesium. 4. Of the two classes of impurities found in water, which is the more harmful? 5. Name three ways of purifying waters known to be impure, and tell which is the most effectual.

Experiment No. 49

Testing for Nitrites in Water

To 50 cc. of water in a small beaker add with a pipette 2 cc. of naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Stir well and wait 20 minutes for color to develop. A pink color indicates nitrites.

Reagents Used

Sulphanilic Acid.—Dissolve 5 gm. in 150 cc. of dilute acetic acid; sp. gr. 1.04.

Naphthylamine Hydrochloride.—Boil 0.1 gm. of solid α-amidonaphthaline (naphthylamine) in 20 cc. of water, filter the solution through a plug of absorbent cotton, and mix the nitrate with 180 cc. of dilute acetic acid. All water used must be free from nitrites, and all vessels must be rinsed out with such water before tests are applied.

1. Would a water showing the presence of nitrites be a safe drinking water? Why? 2. What are nitrites? 3. What does the presence of nitrites indicate? 4. Are small amounts of nitrites, when not associated with bacteria, injurious?

REVIEW QUESTIONS

1. To what extent is water present in foods? 2. What foods contain the most, and what foods the least water? 3. How does the water content of some foods vary with the hydroscopicity of the air? 4. How may changes in water content of foods affect their weight? 5. Why is it necessary to consider the water content of foods in assigning nutritive values? 6. How is the dry matter of a food determined? 7. Why is the determination of the water in a food often a difficult process? 8. What is the ash or mineral matter of a food? 9. How is it obtained? 10. What is its source? 11. Of what is the ash of plants composed? 12. What part in plant life do these ash elements take? 13. Name the ash elements essential for plant growth. 14. Which of the mineral elements take the most essential part in animal nutrition? 15. In what form are these elements usually considered most valuable? 16. Why is sodium chloride or common salt necessary for animal life? 17. How do food materials differ in ash content? 18. Define organic matter of foods. 19. How is it obtained? 20. Of what is it composed? 21. Into what is the organic matter converted when it is burned? 22. Give the two large classes of organic compounds found in food materials. 23. Name the various subdivisions of the non-nitrogenous compounds. 24. What are the carbohydrates? 25. Give their general composition. 26. What is cellulose? 27. Where is it found? 28. What is its function in plants? 29. What is its food value? 30. In what way may cellulose be of value in a ration? 31. In what way may it impart a negative value to a ration? 32. What is starch? 33. Where is it mainly found in plants? 34. Give the mechanical structure of the starch grain. 35. Why is starch insoluble in cold water? 36. How do starch grains from different sources differ in structure? 37. What effect does heat have upon starch? 38. Define hydration of starch. 39. Under what conditions does this change take place? 40. What value as a nutrient does starch possess? 41. What is sugar? 42. How does it resemble and how differ in composition from starch? 43. What are the pectose substances? 44. How are they affected by heat? 45. What food value do they possess? 46. What is nitrogen-free-extract? 47. How is it obtained? 48. How may the nitrogen-free-extract of one food differ from that of another? 49. What are the fats? 50. How do they differ in composition from the starches? 51. Why does fat when burned or digested produce more heat than starch or sugar? 52. Name the separate fats of which animal and vegetable foods are composed. 53. Give some of the physical characteristics of fat. 54. What is the iodine absorption number of a fat? 55. How does the specific gravity of fat compare with that of water? 56. Into what two constituents may all fats be separated? 57. What is ether extract? 58. How does the ether extract in fats vary in composition and nutritive value? 59. What are the organic acids? 60. Name those most commonly met with in foods. 61. What nutritive value do they possess? 62. What dietetic value? 63. What value are they to the growing plant? 64. What organic acids are found in animal foods? 65. What are the essential oils? 66. How do they differ from the fixed oils, or fats? 67. What property do the essential oils impart to foods? 68. What food value do they possess? 69. What dietetic value? 70. What are the mixed compounds? 71. How may a compound impart a negative value to a food? 72. What is the nutritive value of the non-nitrogenous compounds, taken as a class? 73. Why is it necessary that nitrogenous and non-nitrogenous compounds be blended in a ration? 74. What are the nitrogenous compounds? 75. How do they differ from the non-nitrogenous compounds? 76. Name the four subdivisions of the nitrogenous compounds. 77. What is protein? 78. What is characteristic as to its nitrogen content? 79. What are some of the derivative products that can be obtained from the protein molecule? 80. How does the protein content of animal bodies compare with that of plants? 81. Name the various subdivisions of the proteins. 82. What is albumin, and how may it be obtained from a food? 83. What is globulin, and how is it obtained from a food? 84. Give some examples of globulins. 85. What are the albuminates, and how are they affected by the action of acids and alkalies? 86. What are the peptones, and how do they differ from the albumins? 87. How are the peptones produced from other proteids? 88. What are the insoluble proteids? 89. Give an example. 90. Which of the proteids are found to the greatest extent in foods? 91. Why may proteids from different sources vary in their nutritive value? 92. What general change do the proteids undergo during digestion? 93. What is crude protein? 94. How is the crude protein content of a food calculated? 95. Why is the nitrogen content of a food more absolute than the crude protein content? 96. What food value do the proteins possess? 97. Why may proteins serve so many functions in the body? 98. Why is protein necessary as a nutrient? 99. What is the effect of an excess of protein in the ration? 100. What is the effect of a scant amount of protein in a ration? 101. What are the albuminoids? 102. Name borne materials that contain large amounts of albuminoids. 103. What food value do the albuminoids possess? 104. What are the amids? 105. How are they formed in plants? 106. What is their source in animals? 107. What general changes does the element nitrogen undergo in plant and animal bodies? 108. What is the food value of the amids? 109. What are the alkaloids? 110. What is their food value? 111. What effect do some alkaloids exert upon the animal body? 112. How may they be produced in animal foods? 113. What general relationship exists between the various nitrogenous compounds? 114. Why is it essential that the animal body be supplied with nitrogenous food in the form of proteids? 115. Name the cycle of changes through which the element nitrogen passes in plant and animal bodies.

CHAPTER II

Changes in Composition of Foods During Cooking and Preparation

116. How do raw and cooked foods compare in general composition? 117. In what ways are foods acted upon during cooking? 118. What causes chemical changes to take place during cooking? 119. What are the principal compounds that are changed during the process of cooking? 120. How does cooking affect the cellulose of foods? 121. What change does starch undergo during cooking? 122. When foods containing starch are baked, what change occurs? 123. How are the sugars acted upon when foods are cooked? 124. What effect does dry heat have upon sugar? 125. What change occurs to the fats during cooking? 126. How does this affect nutritive value? 127. What changes do the proteids undergo during cooking? 128. Why does the action of heat affect various proteids in different ways? 129. Why are chemical changes, as hydration, often desirable in the cooking and preparation of foods? 130. What physical changes do vegetable and animal tissues undergo when cooked? 131. How do foods change in weight during cooking? 132. Why is a prolonged high temperature unnecessary to secure the best results in cooking? 133. To what extent is the energy of fuels utilized for producing mechanical and chemical changes in foods during cooking? 134. What effect does cooking have upon the bacterial flora of foods? 135. In what ways do bacteria exert a favorable influence in the preparation of foods? 136. How may certain classes of bacteria exert unfavorable changes in the preparation of foods? 137. What are the insoluble ferments? 138. What are the soluble ferments? 139. What part do they take in animal and plant nutrition? 140. Define aerobic ferments. 141. Define anaërobic ferments. 142. What general relationship exists between the chemical, physical, and bacteriological changes that take place in foods? 143. Why should foods also possess an esthetic value? 144. What kinds of colors should be used in the preparation of foods? 145. What processes should be used for removal of coloring materials from foods?

CHAPTER III

Vegetable Foods

146. Give the general composition of vegetable foods as a class. 147. How do vegetable foods differ from animal foods? 148. Name some vegetables which contain the maximum, and some which contain the minimum percentage of protein. 149. Give the general composition of potatoes. 150. Of what is the dry matter mainly composed? 151. How much of the crude protein of potatoes is true protein? 152. What ratio exists between the nitrogenous and non-nitrogenous compounds in the potato? 153. Give the chemical composition of the potato. 154. What influence do different methods of boiling have upon the crude protein content of potatoes? 155. To what extent are the nutrients of potatoes digested and absorbed by the body? 156. What value do potatoes impart to the ration? 157. How do sweet potatoes differ in chemical composition and food value from white potatoes? 158. How do carrots differ in composition from potatoes? 159. What is characteristic of the dry matter of the carrot? 160. How do carrots and milk differ in composition? 161. To what is the color of the carrot due? 162. To what extent are the nutrients removed in the cooking of carrots? 163. What is the value of carrots in a ration? 164. Give the characteristics of the composition of parsnips. 165. How does the starch of parsnips differ from that of potatoes? 166. How does the mineral matter of parsnips differ from that of potatoes? 167. How does the cabbage differ in general composition from many vegetables? 168. To what extent are nutrients extracted in the boiling of cabbage? 169. Give the nutritive value of cabbage. 170. How does the cauliflower differ from cabbage? 171. Give the general composition of beets. 172. Give the general composition of cucumbers. 173. What nutritive value has lettuce? 174. Give the composition and dietetic value of onions. 175. How does the ratio of nitrogenous and non-nitrogenous compounds in spinach differ from that in many other vegetables? 176. Give the general composition and nutritive value of asparagus. 177. How much nutritive material do melons contain? 178. What are the principal compounds of tomatoes? 179. What nutrients do they supply to the ration? 180. In the canning of tomatoes, why is it desirable to conserve the juices? 181. How does sweet corn differ in composition from fully matured corn? 182. What nutritive value does the egg plant possess? 183. What are the principal nutrients of squash? 184. What nutritive material does celery contain? 185. To what does celery owe its dietetic value? 186. Why are vegetables necessary in a ration? 187. Why is it not possible to value many vegetable foods simply on the basis of percentage of nutrients present? 188. Name the miscellaneous compounds which many vegetables contain, and the characteristics which these may impart. 189. Why is it necessary to consider the sanitary conditions of vegetables? 190. How do canned vegetables differ in composition and food value from fresh vegetables? 191. What proportion of vegetables is refuse and non-edible parts? 192. Why is it necessary to consider the refuse of a food in determining its nutritive value?

CHAPTER IV

Fruits

193. To what extent do fruits contain water and dry matter? 194. Give the general composition of fruits. 195. What compounds impart taste and flavor? 196. How much nutrients do fruits add to a ration? 197. Why is it not right to determine the value of fruits entirely on the basis of nutrients? 198. Give the general composition of apples? 199. What compound is present to the greatest extent in the dry matter of apples? 200. How do apples differ in composition? 201. Give the general physical composition of oranges. 202. What nutrients are present to the greatest extent in oranges? 203. How do lemons differ in composition from oranges? 204. How does grape fruit resemble and how differ in chemical composition from oranges and lemons? 205. What are the main compounds in strawberries? 206. In what ways are strawberries valuable in a ration? 207. Of what is grape juice mainly composed? 208. What acid is in grapes, and what is its commercial value? 209. To what are the differences in flavor and taste due? 210. How do ripe olives differ in composition from green olives? 211. What is the food value of the olive? 212. What physiological property does olive oil have? 213. What is the principal nutrient in peaches? 214. What compounds give flavor to peaches? 215. Of what does the dry matter of plums mainly consist? 216. How do plums differ in composition from many other fruits? 217. What are prunes? What is their food value? 218. How do dried fruits differ in composition from fresh fruits? 219. What should be the stage of ripeness of fruit in order to secure the best results in canning? 220. How do canned fruits differ in composition and nutritive value from fresh fruits? 221. To what extent are metals dissolved by fruit juices? 222. Why should tin in which canned goods are preserved be of good quality? 223. What preservatives are sometimes used in the preparation of canned fruits? 224. What is the objection to their use? 225. Why are fruits necessary in the ration? 226. What change does heat bring about in the pectose substances of fruits?

CHAPTER V

Sugar, Molasses, Sirups, Honey, and Confections

227. What is sugar? 228. From what sources are sugars obtained? 229. Name the two divisions into which sugars are divided. 230. How are sugars graded commercially? 231. What per cent of purity has granulated sugar? 232. How is the coloring material of sugar removed? 233. How is sugar treated to make it whiter? 234. What value as a nutrient does sugar possess? 235. Why should sugar be combined with other nutrients? 236. What foods contain appreciable amounts of sugar? 237. Why is an excessive amount of sugar in a ration undesirable? 238. Does sugar possess more than condimental value? 239. What is the average quantity of sugar consumed in this country? 240. What is maple sugar? 241. How does it differ in composition from other sugar? 242. How is adulterated maple sugar detected? 243. To what extent is granulated sugar adulterated? 244. Why is it not easily adulterated? 245. What are the dextrose sugars? 246. How do they differ chemically from sucrose? 247. What is the inversion of sugar? 248. In what way does acid act upon sugar? 249. How are the acid products removed? 250. What is the food value of glucose? 251. What is molasses? 252. How is it obtained? 253. Of what is it composed? 254. What gives taste and flavor to molasses? 255. How may molasses act upon metalware? 256. What is the food value of molasses? 257. What is sirup? 258. Name three kinds of sirup, and mention materials from which they are prepared. 259. What is the polariscope, and how is it employed in sugar work? 260. What is honey? 261. How does it differ in composition from sugar? 262. How is strained honey adulterated? 263. What materials are used in the preparation of confections? 264. What changes take place in their manufacture? 265. What materials are used for imparting color? 266. What can you say in regard to the coal tar colors? 267. What should be the position of candy in the dietary? 268. What can you say of the comparative value of cane and beet sugar? 269. How do the commercial grades of sugar compare as to nutritive value? 270. What are some of the impurities in candy? 271. What is saccharine? 272. What are its properties?

CHAPTER VI

Legumes and Nuts

273. What nutrients do the legumes contain in comparatively large amounts? 274. How does the amount of this nutrient compare with that found in meats? 275. Why are legumes valuable crops in general farming and for the feeding of farm animals? 276. Give the general composition of beans. 277. How do beans compare in protein content with cereals? 278. How does the protein of beans differ from that of many other food materials? 279. To what extent are the nutrients of beans digested? 280. What influence does the combination of beans with other foods have upon digestibility? 281. What influence does removal of skins have upon digestibility? 282. In what part of the digestive tract are beans mainly digested? 283. How does the cost of the nutrients in beans compare with that of the nutrients in other foods? 284. How do string beans differ from green beans? 285. Give the general composition, digestibility, and nutritive value of peas. 286. What can you say of the use of copper sulphate in the preparation of canned peas? 287. What nutrients do peanuts contain in large amounts? 288. Give the general composition of nuts. 289. What are the characteristics of pistachio? 290. Give the general composition of the cocoanut. 291. What is cocoanut butter? 292. To what extent may nuts contribute to the nutritive value of a ration?

CHAPTER VII

Milk and Dairy Products

293. What can you say as to the importance of dairy products in the dietary? 294. Give the general composition of milk. 295. What compound in milk is most variable? 296. To what extent are the nutrients in milk digestible? 297. What influence does milk have upon the digestibility of other foods? 298. Why is cheese cured in cold storage? 299. How can the tendency of a milk diet to produce costiveness be overcome? 300. Why is it necessary to consider the sanitary condition of milk? 301. What factors influence the sanitary condition of milk? 302. What is certified milk? 303. What is pasteurized milk? 304. How can milk be pasteurized for family use? 305. What is tyrotoxicon? 306. What is its source in milk? 307. To what is the color of milk due? 308. To what extent is color associated with fat content? 309. What causes souring of milk? 310. What change occurs in the milk sugar? 311. What are the most favorable conditions for the souring of milk? 312. What are some of the preservatives used in milk. 313. What objection is urged against their use? 314. What is condensed milk? 315. What is buttermilk, and what dietetic value has it? 316. How does goats' milk differ from cows' milk? 317. What is koumiss, and how is it prepared? 318. What are the prepared milks? 319. How does human milk differ in composition from cows' milk? 320. Give the nutritive value of skim milk. 321. What content of fat should cream contain? 322. In what ways is milk adulterated? 323. How are these adulterations detected? 324. Give the general composition of butter. 325. What is the maximum amount of water that a butter may contain without being considered adulterated? 326. What can you say in regard to the digestibility of butter? 327. How is butter adulterated? 328. How does oleomargarine compare in digestibility and food value with butter? 329. What is the food value of butter? 330. How does cheese differ in composition from butter? 331. Give the general composition of cheese. 332. To what are the flavor and odor of cheese due? 333. Why is cheese ripened? 334. What chemical changes take place during ripening? 335. To what extent are the nutrients of cheese digested? 336. Why is cheese sometimes considered indigestible? 337. To what extent do the nutrients of different kinds of cheese vary in digestibility? 338. How does cheese compare in nutritive value and cost with meats? 339. What is cottage cheese? 340. What is Roquefort cheese? 341. Name four kinds of cheese, and say to what each owes its individuality. 342. How is cheese adulterated? 343. Why are dairy products in older agricultural regions generally cheaper than meats?

CHAPTER VIII

Meats and Animal Food Products

344. Give the general composition of meats. 345. How do meats differ in chemical composition from vegetable foods? 346. What is the principal non-nitrogenous compound of meats, and what of vegetables? 347. Name the different classes of proteins in meats. 348. Which class is present in largest amounts? 349. To what extent are amid compounds present in meats? 350. What characteristics do amids impart to meats? 351. How are alkaloids produced in meats? 352. In what ways does the lean meat of different kinds of animals vary chemically and physically? 353. Give the general composition of beef. 354. What relationship exists between the fat and water content of beef? 355. How much refuse have meats? 356. In what forms are the ash elements (mineral matter) present in meats? 357. How does veal differ in composition from beef? 358. What general changes in composition occur as animals mature? 359. How do these compare with the changes that take place when plants ripen and seeds are produced? 360. How does mutton vary in composition from beef? 361. How does it compare in food value with beef? 362. How do lamb and mutton differ in composition? 363. To what extent do the various cuts differ in composition? 364. How do the more expensive cuts of lamb compare in nutritive value with the less expensive cuts? 365. How does pork differ in composition from other meats? 366. Give the general composition of ham. 367. Give the composition and nutritive value of bacon. 368. How does bacon compare in food value with other meats? 369. How does the character of the fat influence the composition and taste of the meat? 370. What influences the texture or toughness of meats? 371. How do cooked meats compare in composition with raw meats? 372. To what extent are nutrients lost in the boiling of meats? 373. What influence does the temperature of the water in which the meat is placed for cooking have upon the amount of nutrients extracted? 374. To what is the shrinking of meats in cooking due? 375. Of what does meat extract mainly consist? 376. To what do beef extracts owe their flavor? 377. What is their food value? 378. What is their dietetic value? 379. What is lard? 380. How does it differ in composition from other fats? 381. What is imparted to meats during the smoking process? 382. Why is saltpeter used in the preservation of meats? 383. Do vegetable foods contain nitrates and nitrites? 384. How does poultry resemble and how differ in composition from other meat? 385. Give the characteristics of sound poultry. 386. Give the general composition of fish. 387. How does the flesh of different kinds of fish vary in composition? 388. What influence does salting and preservation have upon composition? 389. How do fish and meat compare in digestibility? 390. How does the mineral matter and phosphate content of fish compare with that of other foods? 391. What are the main nutrients in oysters? 392. Give the general food value of oysters. 393. What is meant by the fattening of oysters? 394. What effect does the character of the water used in fattening have upon the sanitary value? 395. Give the general composition of the egg. 396. How do different parts of the egg differ in composition? 397. How does the egg differ in composition from the potato? 398. Is color an index to the composition of the egg? 399. What effect does cooking have upon the composition of the egg? 400. What factors influence the flavor of eggs? 401. How do different ways of cooking affect the digestibility? 402. Under what conditions can eggs be used economically in the dietary? 403. Why should eggs be purchased and sold by weight? 404. How do canned meats differ in composition from fresh meats? 405. How do the nutrients of canned meats compare in cost with those of fresh meat? 406. What are the advantages of canned meats over fresh meats? 407. What are some of the materials used in the preservation of meats?

CHAPTER IX

Cereals

408. How are the cereals milled? 409. What are the cereals most commonly used for food purposes? 410. Give the general composition of cereals as a class. 411. What are the main nutrients in corn preparations? 412. What influence does the more complete removal of the bran and germ of corn have upon its digestibility? 413. How does the cost of nutrients in corn compare with other foods? 414. Why is corn alone not suitable for bread-making purposes? 415. Why should corn be combined in a ration with foods mediumly rich in protein? 416. What change takes place in corn meal from long storage? 417. Give the characteristics and composition of oat preparations. 418. How does removal of the oat hull affect the composition of the product? 419. To what extent do the various oat preparations on the market differ in composition and food value? 420. Do oats contain any special alkaloidal or stimulating principle? 421. Why should oatmeal receive longer and more-thorough cooking than many other foods? 422. To what extent are the nutrients in oatmeal digested? 423. How do wheat preparations differ in general composition from corn and oat preparations? 424. What influence upon the composition of the wheat breakfast foods has partial or complete removal of the bran? 425. What is the effect upon their digestibility and nutritive value? 426. What are the special diabetic flours, and how are they prepared? 427. What are the wheat middlings breakfast foods, and how do they compare in digestibility and food value with bread? 428. How do they differ mechanically? 429. How does barley differ from wheat in general composition? 430. What is barley water, and what nutritive material does it contain? 431. What cereal does rice resemble in composition? 432. With what food materials should rice be combined to make a balanced ration? 433. What can you say as to comparative ease and completeness of digestibility of rice? 434. Why are cereals valuable in the ration? 435. In what way do they take a mechanical part in digestion? 436. What are predigested breakfast foods? 437. How would you determine the general nutritive value of a breakfast food, knowing the kind of cereal from which it was prepared? 438. To what extent are cereals modified or changed in composition by cooking? 439. To what extent are the nutrients of cereal foods digested and absorbed by the body? 440. To what extent do the cereals supply the body with mineral matter? 441. How does the phosphate content of cereals compare with that of meats and milk?

CHAPTER X

Wheat Flour

442. Why is wheat flour especially adapted to bread-making purposes? 443. To what extent may wheat vary in protein content? 444. What are spring wheats? 445. What are winter wheats? 446. Give the general characteristics of each. 447. What are glutinous wheats? 448. What are starchy wheats? 449. Name the different proteids in wheat flour. 450. About how much starch does wheat flour contain? 451. What other carbohydrates are also present? 452. What is the roller process of flour milling? 453. What is meant by the first break? 454. How are the different products of the wheat kernel separated? 455. What is meant by middlings flour? 456. What is break flour? 457. What is patent flour? 458. Name the high grade flours. 459. Name the low grade flours. 460. How are the impurities removed from wheat flour? 461. What per cent of the wheat kernel is returned as flour? As offals? 462. What becomes of the wheat germ during milling? 463. What sized bolting cloths are used in milling? 464. What is graham flour? 465. How does it differ in mechanical and chemical composition from white flour? 466. What is entire wheat flour? 467. How does it differ in physical and chemical composition from white flour? 468. What effect has the refining of flour upon the ash content? 469. How do low and high grade flours differ in chemical composition? 470. How do the wheat offals differ in composition from the flour? 471. What are the factors which influence the composition of flours? 472. What effect does storage have upon the bread-making value of flour? 473. What change takes place when new wheat is stored in an elevator? 474. What is durum wheat flour, and how does it differ from other flour? 475. What gives flour its color? 476. Why is color an index of grade? 477. How is the color of a flour determined? 478. How do flours differ in granulation? 479. How does the granulation affect the physical properties of flour? 480. How is the granulation of flour approximately determined? 481. How is the absorptive capacity of a flour determined? 482. What factors cause a variation in the capacity of flours to absorb water? 483. Give the characteristics of a good gluten. 484. What causes unsound flours? 485. How is the bread-making value of a flour determined? 486. How are flours bleached? 487. How does bleaching affect the chemical composition of flour? 488. What influence does bleaching have upon bread-making value? 489. Traces of what compounds are formed during bleaching? 490. Are these compounds injurious to health? 491. What effect does bleaching have upon the color of fiber and débris particles in flour? 492. Is it possible to bleach low grade flours and cause them to resemble high grade flours? 493. Are flours usually adulterated? 494. Why? 495. How would mineral adulterants be detected? 496. How would the presence of other cereals be detected? 497. How does flour compare in nutritive value with other foods? 498. How does the cost of flour compare with that of other foods? 499. What causes flours to vary so in bread-making value? 500. Why may flours produced from the same type of wheat vary slightly in character from year to year? 501. What relationship exists between the nutritive and bread-making value of a flour?