6 . BULLETIlSr 952, U. S. DEPAETMENT OF AGRICULTURE. 



The tannin content in the mother liquid from which tlie cream 

 of tartar was crystallized Avas found to be too low to be considered 

 as a commercial product. 



PREPARATION OF GRAPE POMACE FOR THE MANUFACTURE OF 



JELLY AND OIL. 



Scarcely enough pomace is produced at any one factory to pay the 

 individual plant for the immediate utilization of both skins and 

 seeds. Since, however, the pomace as it is produced contains about 

 50 per cent of moisture, which is conducive to rapid spoilage, atten- 

 tion was directed along the line of preparing this wet pomace in such 

 a way as to permit it to be stored and manufactured later into the 

 various products or to be shipped to some central utilization plant 

 which could handle the entire output from the several grape- juice 

 plants. 



A plant handling even a comparatively small tonnage of grapes 

 could perhaps work up the skins into jelly at a good profit, but it 

 could not profitably extract the oil from the seed, since for this 

 purpose a large, comparatively expensive oil mill would be required. 



Fig. 4. — A direct-heat drier. 



To extract the jelly stock from the skins they must first be boiled 

 in a small quantity of water and then pressed in hydraulic presses. 

 This would necessitate either the installing of additional presses or 

 the reducing of the quantity of grapes handled; in the latter case 

 the output of juice would be curtailed. Experiment has proved that 

 the pomace can be satisfactorily dried, the seeds and skins separated, 

 and each worked up as desired. There would thus be no curtailment 

 of the output of juice because of reduction in the quantity of grapes 

 handled, nor would there be any added expense incurred for in- 

 stalling additional presses. 



The pomace may be dried by means of driers of the direct-heat 

 type (fig, 4) or the steam type (fig. 5), In either case the wet pomace 

 should be disintegrated and conveyed into the machine in a continu- 

 ous stream. Both driers rotate on a horizontal axis. The material 

 enters the driers at one end in a continuous stream and passes 

 out at the other end in a dry condition. The heated air current 

 enters at the discharge end and leaves at the entering end, thus 

 working on the counter-current principle. The two types of 



