VEGETABLE AND FRUIT DEHYDRATION 



185 



The drying ratio and its converse, the drying yield, are shown for 

 18 vegetables in table 23. These ratios and yields "have been calculated 

 from the changes in the moisture content during the drying step. The 

 drying ratio is the ratio of the weight of the material entering the de- 

 ny drator to the weight as it leaves the dehydrator commercially dry. 

 The drying yield is the converse of the drying ratio and is expressed in 

 percentage. These ratios are useful to designers of dehydrators, to 

 operators, and also to prospective operators who wish to compare 

 yields of product from various types of raw materials, since it can 

 usually be assumed that the moisture content of the blanched, prepared 

 material is approximately the same as that of the raw material. 



Table 23. — Drying ratios and drying yields for specific vegetables 1 



Range Average Range Average 



"Ream, lima 



2. 3- 3. 3 

 4.4-15.8 

 5. 3-16. 1 



8. 2-18. 4 

 5. 6-10. 6 



9. 5 20. 

 9. 5-13. 5 

 2. 4- 6. 8 

 5. 1- 9. 7 



7. 2-22. 3 



3. 2-20. 

 3. 4- 8. 7 

 2. 1- 5. 9 

 2.7- 6.3 

 6.8-11.5 



8. 7-19. 2 

 2. 2- 5. 3 



10. 1-28. 7 



2.8 



8.5 

 7.6 



12.6 

 8.0 



15.2 



10.6 

 3.6 

 7.1 



12.3 

 7.6 

 4.4 

 3.6 

 4.2 

 8.7 



13.1 

 2.9 



16.1 



4(U.3) 



4 (12. 6) 



* (9. 4) 



* (4. 7) 



4 (3. 7) 



Percent 

 29. 6-43. 2 



6. 3-22. 3 

 6.2-18.6 

 5. 4-12. 

 9.3-17.7 

 5. 0- 9. 8 



7. 3-10. 5 

 14.6-40.7 

 10.2-19.6 



4.4-13.8 

 5. 0-31. 

 11.3-28.8 

 16.7-45.5 

 15.7-36.0 



8. 6-14. 6 

 5. 2-11.4 



18. 6-44. 6 

 3. 4- 9. 4 



Percent 

 35.2 



Beans, snap.. 



11.6 



Beets.. 



13.0 



Cabbase. __ 



7.9 



Carrots 



12.4 



Celerv... 



6.5 



Chard, Swiss . . 



9. 3 i (8. 8) 



Corn, sweet .- 



Kale 



27.4 

 13.9 



Mustard greens . 



8. 1 i (7. 9) 



Onions 



13. * (10. 6) 





22.5 



Peas, green _ 



27.0 



Potatoes... _ 



23. 6 * (21. 3) 



Rutabagas 



Spinach 



Sweet-potatoes. . .... 



11.4 



7.6 

 33. 8 * (26. 7) 



Tomatoes . .... 



6.2 







1 Calculated from data in table 22. 



2 Drying ratio=weight of prepared, blanched material entering drier divided by weight of dried material 

 leaving drier. 



3 Drying yield = weight of dried material leaving drier divided by weight of prepared, blanched material 

 entering drier x 100. 



4 Data in parentheses obtained at the Western Regional Research Laboratory, Albany, Calif. 



The operator is more directly interested in the overall shrinkage 

 ratio — that is, the weight of unprepared raw product required to yield 

 one weight unit of finished product which meets specifications. This 

 may also be expressed as the reversed ratio, usually as a percentage, 

 and is then known as the overall yield. The overall shrinkage ratio 

 is always substantially higher than the drying ratio, and the overall 

 yield lower than the drying yield, because all weight losses incurred 

 at various steps of the process, such as culling, washing, peeling, trim- 

 ming, and inspecting, must be discounted. Estimates of such losses 

 are presented in the discussion of certain vegetables but it must be 

 remembered that these losses vary widely. 



Suggested tray loadings are shown in table 24 for various systems 

 of air flow. These loadings cannot be regarded as specific recom- 

 mendations ; instead they are to be regarded as suitable for trial. Ex- 

 perience with various materials will indicate necessary modifications. 

 Loadings for cross circulation and through circulation of air are listed 

 separately. 



