II Dec, 1911.] French Prunes. 8ir 



The diagram will give some idea of the arrangement of these different 

 parts. It is only intended to show the main principles ; details vary very 

 considerably with different makes of machines. The drying cliamber is 

 usually built of masonry or brick; the latter permits the use of hollow 

 walls which minimize loss of heat. The fire-box is either of wrought, or 

 preferably of, cast iron. The rails on which the truck runs are immediately 

 over the fire-box. Provision for the entry of fresh air (hot or cold, 

 according to the make of machine) and for the evacuation of moist air, 

 seems of considerable importance, especially the latter. According to 

 Professor Rabate : — 



It is most important to be able, during the currency of the drying, to vary the 

 degree of mois'ure in the interior of the oven. It is therefore necessary to place, 

 at suitable points, openings, the aperture of which can be altered at will. This 

 is the principal constructional ])oint concerning which investigation is necessary. 

 In the present ovens the exit of moist air is always under control. The exits 

 are narrow, and at given moments they are completely closed. The jjrune then 

 cooks itsself* in an atmosphere saturated with steam. Many practical driers consider 

 that this i)reparation in a moist and hot atmosphere contributes to give to Agen 

 prunes their colour, their gloss, and their so delicate aioma. 



Evenness of heating, so that drying is equally rapid throughout the 

 machine, is another necessary feature. It is not possible to here reproduce 

 all that is said concerning the structure and working of the different 

 machines ; an account of the drying process in the winner of the first 

 prize will suffice. This was exhibited by M. Boudie, of Allez, par Sainte- 

 Livrade ; its truck was 8 storied, each taking 6 trays, or 48 in all. 



The absence of any preliminary preparation before undergoing the 

 drying process is noteworthy — Agen prunes are neither dipped in lye nor 

 is the skin pricked mechanically, as is usually the case with Californian 

 prunes. The thinness of skin already referred to, and the high tempera- 

 ture at which drying is conducted, no doubt render this not only unneces- 

 sary but undesirable. 



Work was controlled with the aid of a thermometer, placed in a recess 

 in the door, 4 ft. 3 in. above the rails. A pane of glass separated the 

 thermometer from the outside air. 



Two principles were constantly observed : — 



ist. The temperature should never descend after the mon-.int when, 

 the prunes having been placed in the oven, equilibrium is 

 established. The temperature should rise, or else remain 

 stationary, if it be up to the required degree. 

 2nd. Moisture should never conden.se on the thermometer pane; if a 

 deposit commences to form, the air entrance must ie opened 

 so as to carry away the surplus steam. 



The work comprises thn-e phases : Wrinkling. Seconding, and 

 Finishing. 



W rhikling. "W-XQ empty oven is first heated for alKUit an hour, with 

 all air entran(t's clo.sed, so as to reach 212" F. The truck, loadetl with 

 fruit, is then wheeled into it. The thermometer descends progressively 

 to 140" at the clo.se of an hour. .Mr entrances are gradually opened to 

 carry off surplus moisture. 



Two hours after the intrndiiction of tlie fruit, the door is slightly 

 opened to see if tlie prunes have not swelled too much. If leakage of 

 juice is feared, the truck is taken out for 5 minut«-s so that the skin may 

 acquire strength. The truck is wheeled in once more and the thermt^meter 

 falls again somewhat, reaching 129"- 133" F. L'nder the.se conditions, 



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