12 MISC. PUBLICATION 52 4, U. S. DEPT. OF AGRICULTURE' 



frequently tested, is necessary. Sewage disposal must be adequate. 

 In well-managed food-processing plants some employees should be 

 assigned solely to cleaning operations. Strict cleanliness on the part 

 of all who handle the foods is necessary. 



Blanching 



Nearly all vegetables are blanched, or partially cooked, immediately 

 after they are prepared and just before they are dehydrated. The 

 word "blanch" means to whiten, and for that reason "scald" is possibly 

 a more appropriate term, since blanching in this sense preserves color 

 instead of bleaching it out. "Scald," however, implies the use of hot 

 water, and although hot water is effective, it is likely to reduce the 

 amounts of water-soluble nutritive factors such as vitamin C, the B 

 vitamins, and minerals. Steam blanching is therefore recommended 

 and is widelv used. 



Figure 6. — These carrots have already been mechanically washed and peeled. 

 As the conveyor belt carries them along, the women cut off ends and trim out 

 flaws. 



The value of blanching has come to be more fully appreciated in 

 recent years. Although the mechanism of its action is not completely 

 understood, it is known that it results in much better retention of 

 vitamins, flavor, and color throughout the dehydration process and 

 subsequent storage than dehydrating without blanching. Blanching 

 inactivates certain enzymes, increases the ease of rehydration of some 

 products, destroys bacteria, molds, and other microscopic organisms, 

 and causes other changes which need further study. 



Blanching must be carried out quickly and thoroughly. If pre- 

 pared food cannot be blanched immediately, it should be held under 

 cool running water or in a 1- or 2-percent salt solution. One hour is 

 the maximum time it should be held. 



