VEGETABLE AND FRUIT DEHYDRATION 167 



variety, growing environment, maturity, and storage of raw ma- 

 terials affect the rate and effectiveness of rehydration as well as the 

 color, taste, flavor, and texture of reconstituted products. In tests 

 at the Western Regional Eesearch Laboratory, rate of cooking, taste, 

 flavor, and texture were drastically changed when carrots were 

 permitted to become overmature, but the rate and completeness of 

 rehydration were not affected. This is illustrated in table 15, which 

 shows results from three varieties of carrots grown in one locality 

 and dehydrated by one method. The code numbers, PT67, P771, and 

 P775 represent immature, high-quality carrots, the code numbers 

 P119, P120, and P121, overmature and fair in quality of raw ma- 

 terial. The rate and total degree of rehydration were essentially 

 the same but the rate of cooking and the taste and flavor were 

 definitely and consistently poor in the older samples. 



Definition of Terms 



Four expressions denoting the imbibition of water by the dehy- 

 drated products are commonly used : reconstitution, rehydration, re- 

 freshing, and cooking. Reconstitution implies restoration to the con- 

 dition prior to dehydration in weight, size and shape, texture, color, 

 flavor, composition, structure, and other observable factors. Thus the 

 degree or completeness of reconstitution can be described only par- 

 tially in quantitative terms, since it is difficult, and in some cases im- 

 possible, to make a quantitative evaluation of these constituent fac- 

 tors. While restoration of weight, color, form, and shape can be 

 measured quantitatively, other factors such as taste, flavor, and texture 

 are subject only to qualitative measures. 



The restoration of the weight of the product through the imbibi- 

 tion of water is relatively easy to measure and, when the moisture 

 content of the material is determined before and after dehydration, 

 the percentage of restoration of weight can be calculated from the 

 drained weight of the rehydrated sample. An example is shown in 

 table 14. In this sample a rehydration ratio of 6.00 was equivalent to 

 79.4 percent of the original weight of the sample. 



Methods for calculating certain related ratios are illustrated in table 

 14. The decision regarding calculation rests with the operator and 

 will be influenced by the purpose of the experiment and the informa- 

 tion that is available on the composition of the sample under study. 

 Nevertheless, it is evident from the figures in table 16 that the rehy- 

 dration ratio is not a true index of reconstitution. For instance, the 

 four samples of dehydrated potato strips when rehydrated under ex- 

 actly the same conditions gained 4.5, 4.7, 4.8, and 4.9 times the dry 

 weight of the sample; the coefficients of weight restoration varied, 

 however, from 78.5 to 124.3 percent. The gain in weight in rehy- 

 dration was directly proportional to the solids in the dry sample, but 

 to have attained the original composition the Nebraska Triumph 

 sample required restoration to 85.0 percent water, while the Colorado 

 Russet required only 75.5 percent. 



