Edible Products, 



252 



[March, 1909. 



circumstances and the will of the planter 

 which at least, for the most part, should 

 be used in potato-starch manufacture as 

 well— by which, with chea per plant and 

 at a lower running cost, they get nearly 

 or quite 25 per cent. The new process is 

 the work of Archbold, who published a 

 brief description of it in the Journal ot 

 the Society of Chemical Industry (1903, 

 p. 63-66), The washed roots are scraped 

 and milled- The pulp is then driven 

 upward by a stream of water against a 

 wire-gauze diaphragm, through which 

 the starch and water pass. Instead of 

 having the starch settle in still tanks, 

 the milky mixture of starch and water 

 is piped to near the bottom of a tank 

 which has the form of a large inverted 

 cone, in which the mixture flows up- 

 ward. As the cone widens upward the 

 rate of flow decreases until it becomes 

 so slow that the starch settles against 

 it ; only the dirty water flows off at the 

 top, and the starch is drawn off below. 



To insure the quality of starch, there 

 is one condition more important than 

 all others— an abundance of clean pure 

 water. The pulp must be thoroughly 

 washed to separate the starch from the 

 waste, and then the starch needs from 

 two to sometimes as many as eight 

 washings. If there is any evident im- 

 purity in the water, the starch may be 

 relied upon to take it up. It is of course 

 expected that the starch will be free 

 from all particles of cellulose or wood ; 

 this is easily managed by the use of a 

 sound fine sieve, whether of cloth or wire. 



The completeness with which the 

 starch can be extracted depends on how 

 completely all the cells are broken. In 

 the potato-starch factories and in 

 Florida, the comminuation of the roots 

 is accomplished by a rotating cylinder 

 set with blades with saw-like edges. A 

 cheaper mill can be made by filling a 

 sheet of iron or tin with holes by 

 driving a nail into it, driving it 

 always in the same direction. The 

 sheet is then fastened around a cylinder. 

 I quote from Bulletin 106, Bureau of 

 Chemistry, United States Department 

 of Agriculture, page 28 :— " A two-horse- 

 power gas engine was used for grinding, 

 the mill consisting of a revolving drurn 

 covered with a sheet of roofing tin punc- 

 tured to make a grating surface. Over 

 this a hopper was arranged, the whole 

 resting on a suitable frame. This mill 

 cost, when complete, with shaft, boxings, 

 and pulley, §10, and would grind one 

 ton of tubers in one and a half hours." 



The quality of the work of such a mill 

 depends on the fineness of the projec- 

 tions and the speed of the rotation. A 

 cylinder with fine teeth will not 

 work a§ fast as one with coarse 



teeth ; but it will not use much more 

 power in milling a given weight of roots, 

 and for the sake of greater capacity it 

 has only to be made longer. With such 

 a cylinder whose projections are more 

 than one millimeter high, not more than 

 24 per cent out of 31 is likely to be ex- 

 tracted. With a cylinder whose projec- 

 tions ate less than 0"5 millimeter high 

 it is as easy to get 3 or 4 per cent. more. 



In the Philippines the roots can be 

 produced at so low a cost that the use of 

 expensive machinery for the extraction 

 of the last possible percentage of starch 

 would be foolish. The money that would 

 be spent in the purchase and operation 

 of such machinery will give a much larger 

 return in starch if it is spent in producing 

 more roots. The process of manufacture, 

 as it can most profitably be carried out 

 here, reduces itself to this : — 



1- Cleaning the roots perfectly. 



2. Milling them on the rough cylinder 



just described. 



3. Screening the pulp — This is sim- 

 ply and thoroughly done by running it 

 through a trough with sieve bottom of 

 cloth or wire. To make it screen well and 

 quickly, the trough should be shaken and 

 fine jets of water should play upon it. 



4. Settling.— Concrete tanks will, 

 without doubt, prove most economical. 

 For fast work in washing they should 

 be shallow. 



5. Washing.— After the water is run 

 off, preferably by means of cocks in the 

 sides of the tanks, the starch must be 

 washed with clean water and allowed to 

 settle, and this must be repeated until it is 

 perfectly white. To keep the starch from 

 making a hard sediment and not being 

 washed except on the top, each tank 

 should have a stirring paddle or set of 

 paddles which will best be worked by 

 hand. Care must be taken that no dirt 

 can fall or blow into the tanks. 



6. Drying.— How this is done will 

 depend upon local conditions, but will 

 usually prove unsafe to rely upon the 

 sun. If a drying house is used, it must 

 be absolutely free from smoke and dust. 



Cost op Production. 

 It would not be without interest, if 

 it were possible, to make a detailed 

 statement in support of the assertion that 

 manioc production in the Philippines 

 is remarkably cheap. But as soon as 

 such statements become really detailed, 

 they cease to have more than a very 

 local value, and fit only the case of the 

 individual whose experiments they re- 

 present. The cost of management and 

 the items chargeable as interest, deterior- 

 ation, and rent depend go entirely upon 



