Proteid Foods 23

dough is formed. Then knead the dough in the hands until it becomes
smooth and elastic. Then place in a piece of cheese-cloth and wash
in cold water (by working and kneading under water) until when
fresh water is added it is no longer milky. This will take from 20 to
30 ee and must be carefully done or the experiment will not be
successful.

There should be remaining in the cheese-cloth a sticky, greyish-
white mass called gluten. Save a part of the gluten to compare with
the proteids and bake the rest in a hot oven. Note any changes that
ioe place in the gluten during baking and study it carefully after

aking.

Experiment ITI.

Add one teaspoonful of lemon juice, vinegar or any acid to one-
half cupful of sweet milk. Heat slowly until lukewarm, no longer,
stir and separate the curd from the whey by gathering into small
Te 4 The curd is mostly composed of casein and is part of the proteid
in milk.

Experiment III.

With a dull knife scrape a piece of lean beef until the tender
muscle fiber is separated from the connective tissue which will appear
as firm, white threads. The fiber is called myosin and is one of the
proteids of meat. 7

Experiment IV.

Beside the white of an egg, place the gluten, the casein and the
myosin. You have before you four principle representatives of the
proteid of human foodstuffs. If you could separate from peas, beans
and other pulses, the substance called legumin, you would see the
fifth important proteid.

Compare the four samples of proteid, notices all the differences,
then study them to observe certain properties which they have in
common. |

1. Notice the elasticity of each, also the tenacity of each.

2. Cook the egg white in hot water, boil the muscle fiber in
water, and bake the gluten. Notice the effect of heat on
each, observe that each is toughened by a high temperature.

3. Dry each cooked sample in a warm oven, then grind each
to a fine powder, and notice that in each case the powder is
similar in appearance and texture.

4. From these experiments write your observations and state
fully your own inferences regarding the correct methods
of cooking foods containing proteid.