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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



" upright " or vertical type, which is the one made by most 

 manufacturers. Fig. 36 represents the other type, and in 

 that, as you will see, the hot-air chamber is not vertical, but in 

 an inclined plane at a slight angle from the stove or furnace. 



It is necessary to point out that evaporated fruit must not be 

 confounded with sun-dried or kiln- dried fruit ; the latter are both 

 very inferior in quality, and are in a different chemical state. 

 Sun-drying is still much used in California and elsewhere, but 

 is being rapidly superseded by the more scientific process of 

 evaporation. The description of the chemistry of this process 

 which I am about to submit to you I have selected as being the 

 best I am acquainted with, and for which I am indebted to an 

 eminent American scientist, Dr. J. F. Symons, of Fayetteville, 

 Arkansas. It is the account he gave to the " South-West 

 Association of Fruit and Vegetable Evaporators " at Springfield, 

 Mo., and will, I hope, afford useful information as to the reasons 

 why properly evaporated fruits are superior to those which are 

 sun-dried or kiln-dried. Dr. Symons says : — - 



I will now describe the process of true evaporation. It has been 

 found that by removing a part of the water rapidly, in swift-moving 

 currents of air, heated from 240° F., a different product is the result, 

 wholly unlike either the fresh or sun-dried fruit, and which will 

 keep better, is more digestible and nutritious, is less acid, and will sell 

 for more in the market. But if, after having heated the air hot enough, 

 there is not sufficient circulation, or the currents not rapid enough, the 

 fruit will cook and then dry, or burn the same as in a close oven. 

 Apples will cook in boiling water at a temperature of only 212° F., 

 or bake in an oven at 225° F. ; but if the heated air circulates fast 

 enough, the fruit will not cook or burn or become itself heated to the 

 temperature indicated by the thermometer, even at 300° F., for the 

 evaporation of the water is a cooling process, and every particle of 

 vapour leaving the minute cells which contained it carries with it also 

 a large amount of caloric in a latent form, and thus keeps the heat of 

 the apples far below the surrounding air. The chemical changes which 

 belong to truly evaporated fruit will now begin, and the albumen, 

 instead of being slowly dried, is coagulated precisely the same as in an 

 egg when boiled. The soluble starch existing in all the fruit, and 

 composed of C 6 H 10 O 5 , will, if the heat is high enough, combine with 

 one equivalent of water (H 2 0), so that now we have an entirely differ- 

 ent compound, to wit, glucose, or fruit sugar, which will assist in the 

 preservation of the fruit, instead of being liable to decomposition as 

 the dried starch is in sun-dried or slowly dried product. 



All the pectine, or fruit jelly, remains in the cells undecomposed, or 

 is left upon the surface by the evaporation of the water in which it was 

 dissolved, and may be seen condensed upon the surface, instead of 

 being decomposed, and passing on with the starch and gluten into the 

 acetic fermentation. The diastase or saccharine ferment contained in 



