10 BULLETIN 540, U. S. DEPARTMENT OF AGRICULTURE. 
Correlation.—Physics: Study of conduction, convection, and radia- 
tion of heat, as applied in the stove. The insulated oven. The 
fireless cooker. 
Norr.—lIf possible plan an additional lesson on the canning of fruit in which one © . 
of the outdoor canners is used in the orchard. In this case can in tin. Show how the 
culls, which would in many cases be wasted, may be utilized. This work could be 
given with all the girls in places wherelarge amounts of fruit are available. There 
might be a contest between the different classes. Aim to emphasize the economic 
side and at the same time give the girls opportunity to work with large quantities of 
material. This lesson may be substituted for one of the following lessons or given as 
an extra lesson on the weekly holiday. 
LESSON 4. 
Problem.—To study the relation of microorganisms to the spoiling 
of food. 
Pownts to be brought out.—Since microorganisms which may cause 
_the spoiling of food are present all about us extreme care is necessary 
to prevent the contamination of food. In preserving we must kill 
all the microorganisms present or prevent their development. Simple 
heating at the boiling point for 15 to 20 minutes is sufficient in the 
case of fruit. Most vegetables are more difficult to sterilize. They 
must be heated for several hours. A shorter time may be used at a 
much higher temperature such as is obtained under pressure, or the 
material may be heated for a shorter time on three successive days. 
References.—Preservation of Food in the Home, Univ. Mo. Bul, 
15 (1914), No. 7, pp. 1-8; U. S. Dept. Agr., Farmers’ Buls. 359, 426,* 
and 521. 
Correlation.—English: Stories of germ life. 
LESSON 5. 
Problem.—To can any available vegetables, using the following 
methods: (1) Cooking on each of three successive days, (2) long 
cooking at the boiling temperature, and (3) cooking under pressure, 
if possible. -Compare the methods as to time and trouble involved, 
the keeping qualities of the products, and the amount of fuel required. 
Points to be brought out.—Complete sterilization is more difficult in 
the case of vegetables than in the case of fruits. The comparative 
value of the different methods of canning. The canned vegetables 
are an important addition to the winter’s dietary. 
References.—U.S. Dept. Agr., Farmers’ Buls. 259*,! pp. 30-32; 359. 
Correlation.—Arithmetic: Estimate cost of home-canned vege- 
tables, taking into consideration the different factors involved. Com- 
pare with the cost.of the factory-canned material. English: His- 
tory of canning industry (Encyclopedia). 
1 Farmers’ Bulletins marked with an asterisk throughout this publication are not available for free dis- 
tribution, but may be secured from the Superintendent of Documents, Government Printing Office, Wash- 
ington, D.C., for 5 cents a copy. 
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