VEGETABLE AND FRUIT DEHYDRATION 151 



siderable importance in dehydrated foods and it is most desirable 

 to retain as much of the original content in the fruits and vegetables 

 as possible. Because of its sensitivity to conditions that also tend 

 to affect flavor characteristics adversely, measurement of its retention 

 has been suggested as a means of following objectively general quality 

 retention. 



Vitamin A does not occur in plant materials, but its precursor, caro- 

 tene, does occur in green and yellow vegetables, 13 notably greens, 

 carrots, and sweetpotatoes. Like ascorbic acid it is labile and some- 

 what difficult to retain through the various steps of processing and 

 storage. However, it appears to be affected only slightly by the mois- 

 ture content of the dehydrated product but to a large extent by the 

 oxygen content of the storage atmosphere, especially during storage 

 at high temperatures. For this reason inert gases, such as nitrogen 

 and carbon dioxide, are employed in packaging carrots in hermetically 

 sealed containers. Because it contributes largely to the color of some 

 vegetables, its destruction is closely related to adverse changes in their 

 characteristic color. Moreover, in carrots it appears to undergo trans- 

 formation to beta-ionone, an organic compound with a pronounced 

 violet odor. 



Vitamin assays are much more complicated than moisture or enzyme 

 determinations and require special equipment and more highly trained 

 personnel. Because of limited space it is impossible to present com- 

 plete details of the methods but general instructions and precautions 

 for application of certain accepted procedures to dehydrated foods 

 are given below. References to more comprehensive discussions are 

 cited and it is strongly urged that the chemist or laboratory technician 

 refer to them before undertaking the performance of these assays if 

 he wishes to attain that high degree of accuracy in his results that 

 comes with a full understanding of the procedures. Bioassay will not 

 -be considered since it requires specialized training and experience, 

 animal colonies, and long periods of time. Moreover, for thiamine, 

 riboflavin, ascorbic acid, and carotene, quite reliable chemical methods 

 are now known that make possible large numbers of determinations in 

 a short time. 



CAROTENE 



The analysis for carotene as here outlined takes into account the 

 problems involved in the quantitative extraction of carotene from de- 

 hydrated vegetables. The procedure also employs a chromatographic 

 adsorption step similar to that now being investigated by the com- 

 mittee on the determination of chlorophyll and carotene of the As- 

 sociation of Official Agricultural Chemists. The precision of the 

 method has been studied and in the case of dried carrots and spinach 

 the standard deviation has been found to be less than ± 4 percent of 

 the mean carotene value. 



Equipment: Colorimeter (reliable make) with blue filter, Waring blender or 

 equivalent, hand-operated meat grinder, funnels (5.5 cm. Biichuer, sintered-glass 

 500-ml. separatory), flasks (500- and 100-ml. volumetric, 50-ml. round bottom), 

 calcium phosphate chromatographic column. 



Reagents: Acetone (90-percent), diethyl ether, petroleum ether, Filter-Cel, 

 pure crystalline carotene, calcium phosphate (CaHPCh). 



13 In the analysis of sweet corn, cryptoxanthin as well as carotene contributes to the 

 vitamin A value and special treatment is required. 



