is in many cases considered the preferred method 

 lor household use because unilorm contact wltli 

 the heating medium can be readily attained and 

 sul'ficient heat treatment to inactivate enzymes 

 is fairly certain. 



Preheating in a liousehold steamer requires more 

 attention to details of procedure to assure ade- 

 quate heating of all portions of the vegetable or 

 fruit. Unless fruits and vegetables are steamed 

 in relatively Oiin layers, inferior frozen prod- 

 ucts may result because of insufficient preheat- 

 ing of central portions. However, since better 

 retention of flavor and soluble nutrients is re- 

 ported for some foods that are preheated in steam, 

 tills method was selected when reports indicated 

 tliat steaming yielded satisfactory products. 



Time- temperature relationships. — Wliile reports 

 in Uie literature give much attention to the prob- 

 lem of time-temperature relationships required 

 for preheating different vegetables, recommenda- 

 tions vary considerably. Some of these variations 

 are due to differences in methods of counting time. 

 T^iough it did not seem feeisible to include this 

 detail in the outlines, in some cases preheating 

 is timed from the moment of immersion of the pre- 

 pared vegetable in boiling water. In otlier in- 

 stances, time is counted when the water returns 

 to boiling. With a specified heating time, the 

 latter procedure provides for considerably more 

 heat treatment than tlie former. 



Proportion of water. — There was general agree- 

 ment in the literature that the best proportion 

 of vegetable to water to use is 1 pound of pre- 

 pared vegetable to approximately 1 gallon of water. 

 Tlierefore this information is not reported in the 

 notes . 



Cooling 



Essentially the same cooling procedure is rec- 

 ommended by all investigators. As soon as pre- 

 heating is completed, the vegetable is plunged 



Into colli running water liaving a temperature of 

 ">0° to 00° F. or into water to which ice has been 

 adiled. Some vegetables that are mashed or pressed 

 tlirougli a sieve are cooled in air or by floating 

 the pan in cold water. References are not given 

 lor tliis step in the preparation of vegetables for 

 freezing except where additional information is 

 given . 



Varieties 



The notes do not include specific recommendations 

 as to varieties of fruits and vegetables and other 

 •factors sucli as maturity, although it is recognized 

 tliat they are important to the quality of the frozen 

 products. Because tlie varieties available and the 

 quality of fruits and vegetables vary with tlie 

 region in which they are grown, detailed infor- 

 mation on selection for freezing should be souglit 

 from horticulturists and food-freezing specialists 

 in local areas. 



Packaging 



Only in the sections on prepared foods lias in- 

 formation on packaging been included in the classi- 

 lled notes. Tlie packaging requirements for most 

 I'ruits and vegetables are very similar, the major 

 prerequisite being that the package be moisture- 

 vapor-proof. Tills publication does not attempt 

 to evaluate the varioustypes of packaging materials 

 on the market. 



Storage 



Wliere information was available on the storage 

 life of frozen prepared foods i t has been included 

 in the outline. Time did not permit a review of 

 the literature on storage life of frozen fruits 

 and vegetables. However, the storage life of these 

 products is generally longer than that of precooked 

 foods. Most frozen fruits and vegetables, when 

 properly prepared and packaged, are satisfactory 

 during storage for 9 to 12 montlis at 0°F. or lower. 



