162 MISC. PUBLICATION 5 4 0, U. S. DEPT. OF AGRICULTURE 

















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Figure 70. — Effects of soaking and boiling for various periods on the amount of 

 water imbibed by dehydrated carrot slices. (See text for details.) 



Composition and Amount of Water 



In order to maintain effective rehydration throughout the test, ade- 

 quate water must be supplied to the sample. It is impossible to main- 

 tain proper ratios of water to sample during the test if the rate of 

 boiling varies from one test to the next. 



The amount of solution to use for a given weight of material in any 

 test may depend upon the immediate purpose of the test. Enough 

 must be used to insure complete wetting of all parts of the sample. It 

 may be desirable to shake or stir during the test period, in order to 

 insure uniform wetting. When a sample is prepared for palatability 

 tests, or for the purpose of demonstrating the preparation of the foods 

 for homes or institutions, it may be desirable to use relatively small 

 amounts of water and thus conserve taste, flavor, and nutrients, even 

 though a lower coefficient of rehydration is attained. The nature of 

 the solution is also highly important, because a variety of reactions 

 may occur as a result of variations in composition. Taste, flavor, 

 texture and color, one or all, may be affected. 



There are four groups of pigments in fruits and vegetables which 

 determine color: anthocyanins, flavonols, carotinoids, and chloro- 

 phylls. Red, purple, and black products, such as beets, plums, grapes, 

 and red cabbage or onions, contain the anthocyanin pigments, which 

 are highly soluble in water, and when excessive amounts are used 

 and drained off, the color becomes poor. When acid is added to the 

 solution, tne color becomes pleasantly brighter and lighter, but in 



