4. To D add tannic acid or a solution of tannin.
Repeat this series of tests, applying them to solutions
of gelatine of equal strength. Carefully compare the
results with the results obtained in the case of albumin.
What inference may be drawn from this series of experi-
ments as a whole?
Ill
Action of Pineapple Juice on Gelatine and Albumin
1. Place in two test tubes 8 cc. each of gelatine and
albumin prepared as in Experiment I, 2, page 48. Add
to each test tube an equal volume of fresh pineapple juice,
mix well, and let stand 30 m. Divide the contents of
each test tube into four equal parts. Apply to each of
these four portions of gelatine and albumin, respectively,
the following reagents:
(a) The xanthoproteic test.
(6) A solution of magnesium sulphate (see II, 3).
(c) Acetic acid.
id) Heat.
50 PRINCIPLES OF FOOD PREPARATION
Compare the results in the present instance with the
characteristic reactions of gelatine and albumin to the
same reagents. Should you say that the pineapple juice
brought about a chemical change? Is the resulting prod-
uct the same in the case of the two food substances?
TOPICS FOR STUDY OR DISCUSSION
1. Sources of commercial gelatine; the various ani-
mal tissues which yield gelatine; gelatine from fish.
2. Manufacture of commercial gelatine; cause of the
acidity of certain brands.
3. Digestibility of gelatine, its ''acid-fixing" proper-
ties, its absorbability.
4. The function of gelatine in the body. Is it a ''pro-
tein sparer"? Is it a source of energy? Is it a tissue
builder?
5. "Fixed" or "tissue" (organized) albumin of body,
compared with the "circulating" albumin.
G. Bromelin and other ferments.
7. Peptones and other products of digestion.
QUESTIONS
1. Under what circumstances may an extra quantity
of gelatine be used for a mold? When may less than the
average amount be used?
2. Account for the difference in the consistency of
the coffee jelly as compared with the other jellies made
on the same basis.
3. Name four possible causes for the persistent lique-
faction of a gelatine jelly. How may each be treated?
4. What may be done to avoid the "curdling" of a
milk jelly?
5. Estimate from your work with gelatine what is the
smallest percentage of this substance that can be used
to stiffen a mold.
6. What percentage of albumin is the minimum needed
to stiffen a mold? (Review work with eggs.)
QUESTIONS
51
7. Compare gelatine and albumin as to source, com-
position, behavior in cooking, and function in the body.
8. Similarly compare gelatine and pectin.
9. With what foods may gelatine best be combined?
When is a gelatine dessert most appropriate for dinner?
10. Suggest some dietetic uses of fresh pineapple.
11. Which of the brands of commercial gelatine studied
would you choose for use in the home? Which for class
work? Why?
12. What are the characteristics of a well-made dish
of gelatine jelly?
TOMATO JELLY IN RING MOLD. GARNISHED WITH CELERY AND
LETTUCE
EXERCISES
1. Make tomato jelly in a ring; fill the center with
blanched and curled celery. Improvise a ring mold.
2. Mold fruits, nuts, etc., in a given design in a clear
gelatine jelly.
3. Make a ribbon jelly, using milk for one layer, yolk
of egg, coffee, or strawberry preserve for the others.
The milk and yolk of egg should be flavored with fruit
juice.
4. Make a milk jelly flavored with lemon juice.
Page 23
Presented as published in 1914. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
4. To D add tannic acid or a solution of tannin. Repeat this series of tests, applying them to solutions
of gelatine of equal strength. Carefully compare the results with the results obtained in the case of albumin. What inference may be drawn from this series of experiments as a whole?
Action of Pineapple Juice on Gelatine and Albumin
1. Place in two test tubes 8 cc. each of gelatine and albumin prepared as in Experiment I, 2, page 48. Add to each test tube an equal volume of fresh pineapple juice, mix well, and let stand 30 m. Divide the contents of each test tube into four equal parts. Apply to each of these four portions of gelatine and albumin, respectively, the following reagents:
(a) The xanthoproteic test.
(6) A solution of magnesium sulphate (see II, 3).
(c) Acetic acid.
id) Heat.
Compare the results in the present instance with the characteristic reactions of gelatine and albumin to the same reagents. Should you say that the pineapple juice brought about a chemical change? Is the resulting product the same in the case of the two food substances?
1. Sources of commercial gelatine; the various animal tissues which yield gelatine; gelatine from fish.
2. Manufacture of commercial gelatine; cause of the acidity of certain brands.
3. Digestibility of gelatine, its ''acid-fixing" properties, its absorbability.
4. The function of gelatine in the body. Is it a ''protein sparer"? Is it a source of energy? Is it a tissue builder?
5. "Fixed" or "tissue" (organized) albumin of body, compared with the "circulating" albumin.
G. Bromelin and other ferments.
7. Peptones and other products of digestion.
1. Under what circumstances may an extra quantity of gelatine be used for a mold? When may less than the average amount be used?
2. Account for the difference in the consistency of the coffee jelly as compared with the other jellies made on the same basis.
3. Name four possible causes for the persistent liquefaction of a gelatine jelly. How may each be treated?
4. What may be done to avoid the "curdling" of a milk jelly?
5. Estimate from your work with gelatine what is the smallest percentage of this substance that can be used to stiffen a mold.
6. What percentage of albumin is the minimum needed to stiffen a mold? (Review work with eggs.)
7. Compare gelatine and albumin as to source, composition, behavior in cooking, and function in the body.
8. Similarly compare gelatine and pectin.
9. With what foods may gelatine best be combined? When is a gelatine dessert most appropriate for dinner?
10. Suggest some dietetic uses of fresh pineapple.
11. Which of the brands of commercial gelatine studied would you choose for use in the home? Which for class work? Why?
12. What are the characteristics of a well-made dish of gelatine jelly?
TOMATO JELLY IN RING MOLD. GARNISHED WITH CELERY AND
LETTUCE
1. Make tomato jelly in a ring; fill the center with blanched and curled celery. Improvise a ring mold.
2. Mold fruits, nuts, etc., in a given design in a clear gelatine jelly.
3. Make a ribbon jelly, using milk for one layer, yolk of egg, coffee, or strawberry preserve for the others. The milk and yolk of egg should be flavored with fruit juice.
4. Make a milk jelly flavored with lemon juice.