I9i8 



BETTER FRUIT 



Page 7 



Evaporation of Prunes and Economical Suggestions 



By A. F. Barss, Assistant Professor of Pomology Oregon Agricultural College 



IN view of the present outlook for an 

 especially large crop of prunes 

 quite generally throughout the 

 prune-growing sections of the North- 

 west, it seems advisable to prepare our- 

 selves in time so that the entire crop 

 may be saved. In the case of many 

 young prune orchards this will be the 

 first year of bearing. For those men 

 who are to evaporate prunes for the 

 first time, the following remarks will 

 save them many mistakes and at the 

 same time prove most timely and valu- 

 able to more experienced evaporator 

 men by giving them suggestions for 

 changing and improving their present 

 methods. Before actual evaporation, a 

 building should be supplied and prop- 

 erly equipped. It is realized, however, 

 that this is no time to begin to think 

 about building, for unless already well 

 under way it would be next to impos- 

 sible to have such a building in shape 

 for this season's run. It cannot be too 

 strongly urged, however, in the face of 

 the present labor conditions that every- 

 one so readjust and systematize the 

 work in the drier as to get the maxi- 

 mum results with what labor is avail- 

 able. By cutting down on extra han- 

 dling and introducing mechanical con- 

 veniences it will frequently be possible 

 to save on man power without loss of 

 efficiency. 



When we realize that it is impossible 

 to produce a high-grade evaporated 

 product from inferior fresh fruit, we 

 can see the importance of care in har- 

 vesting. If the dried product is to have 

 superior flavor and to give the greatest 

 yield, it is important that the fruit be 

 allowed to ripen on the trees and to be 

 picked up only when it has fallen nat- 

 urally or after a very light shaking. 

 Experimental evidence proves beyond 

 doubt that the prunes which do not 

 ripen on the tree are much inferior to 

 those which are harvested only after 

 falling to the ground. In view of this 

 fact it is essential for most satisfactory 

 results that the season of picking be not 

 thrown in advance of the normal sea- 

 son, but delayed until sufficient prunes 

 have fallen to the ground to make a 

 first picking practicable. The weather 

 records for a number of years show 

 that the earlier picking does not tend 

 to avoid the rain any more than picking 

 at the natural season. When we con- 

 sider, then, that the most important 

 time in the life of the prune to give it 

 size, quality and yield per acre, is 

 during the last few days of maturity, 

 we can see the importance of delaying 

 the picking. Heavy shaking except just 

 before the last picking is to be dis- 

 couraged. A light shaking, however, 

 before each picking will merely tend 

 to remove those prunes which would 

 be falling naturally within a short time 

 in case of a light wind. The prunes 

 should be gathered into small slatted 

 crates, for in case of moist, warm 

 weather at time of harvesting, those 

 prunes which are picked into large lug 

 boxes and allowed to remain for any 



length of time in these before being 

 placed in the evaporator deteriorate 

 very rapidly. Such weather conditions 

 are most favorable for the spread of 

 brown rot and also tend to increase 

 fermentation to such a degree as to 

 cause a material loss of sugar and 

 weight in the final dried product. 



It must be borne in mind that regard- 

 less of the way in which the fruit is 

 handled in the field or the kind of con- 

 tainer into which it is gathered, the 

 least delay between the time of har- 

 vesting and actual placing of the fruit 

 in the evaporating chamber, the better 

 will be the results. In regard to what 

 constitutes preparation for evaporation 

 there is a wide difference of opinion. 

 Excellent results have been obtained by 

 evaporator men each following a differ- 

 ent practice. Certain suggestions, how- 

 ever, may be followed to advantage. 

 Little, if any, grading previous to fray- 

 ing has been practiced in the North- 

 west. It appears that there is such a 

 wide variation in the time required to 

 dry the large and small prunes or to 

 dry the more matured as opposed to 

 the greener prunes, that it would seem 

 wise to grade the fruit by dividing into 

 at least three sizes. This may be done 

 at less expense by the use of a mechan- 

 ical grader, but few would find it pos- 

 sible to install such a machine at this 

 time. Home-made hand-grading de- 

 vices which will do satisfactory work 

 may be substituted. By grading, all the 

 prunes on any one tray would be of 

 approximately the same size. This 

 would give more even drying, it not 

 being necessary to over-dry some of the 

 smaller prunes because of the presence 

 of larger prunes on the same tray. Such 

 a practice in itself would increase the 

 percentage of dried fruit obtained from 

 a given weight of fresh. While it may 

 not be possible to install a grading sys- 

 tem at this time, it will at least be 

 found worth while to carefully hand 

 pick the fruit, removing any worthless 

 or decayed fruit, the precence of which 

 on a tray would merely tend to lower 

 the quality of the whole as well as 

 occupy space on a tray which might 

 be used to advantage by first-class fruit. 



The particular method of handling 

 the prunes before spreading on the 

 trays seems to differ with the section, 

 most of the growers in a given section 

 following the same practice, there being 

 no one accepted method used in all re- 

 gions alike. Some growers dip in hot 

 lye water, some in boiling water, some 

 in cold water and some tray the prunes 

 as they come in from the orchard with- 

 out any dipping. An interesting point 

 is that all of these men are able to com- 

 mand standard prices for their dried 

 product. While it might be stated that 

 the most common practice is to dip the 

 prunes in a lye solution, many packers 

 strongly discourage the use of lye. It 

 has been found by experimentation that 

 when pioperly regulated, not only may 

 lye dipping not injure the dried pro- 

 duct, but it does materially tend to re- 



duce on the time of drying. Where lye 

 is used the average strength is one 

 pound of lye to from thirty to fifty gal- 

 lons of water. Some use it much 

 stronger than this, but where arrange- 

 ment is made to keep the water actively 

 boiling, a smaller amount of lye will do 

 the same work as more lye in colder 

 water. Lye dipping, unless the prunes 

 have previously been graded, will tend 

 to accentuate uneven drying since the 

 ripe prunes will tend to check much 

 more easily than green prunes. For 

 this reason and because of the fact that 

 a strong lye solution is often used to 

 conceal the effects of serious brown-rot 

 infection, the use of actively boiling 

 wafer in place of lye wafer is to be 

 commended. While there seems to be 

 no serious objection to the use of lye 

 in small quantifies followed by thor- 

 ough rinsing, nevertheless lye has in 

 the past been used improperly so 

 widely that it has quite largely fallen 

 into disfavor and the use of boiling 

 water substituted for it. In addition to 

 the first dipping a thorough rinsing in 

 one or two waters is desirable for sani- 

 tary reasons. 



While those growers who are oper- 

 ating small evaporators cannot well 

 afford to install modern power ma- 

 chinery for dipping and fraying, those 

 evaporating on a larger scale will find 

 it decidedly to their advantage to do 

 away with the hand outfits. A com- 

 parison of the efficiency of the two 

 methods leaves no doubt but that where 

 the larger machine can be kept occu- 

 pied through handling large quantifies 

 of fruit, it should be installed. This is 

 of especial importance this season 

 when any means which can be em- 

 ployed to reduce hand labor will be 

 essential. Mliere the dipping and fray- 

 ing device can be so arranged as to 

 allow for a careful inspection of the 

 fruit, either before dipping or after it 

 is placed on the tray, a great deal of 

 space which might be wasted will be 

 saved by removing all immature and 

 decayed fruit and filling the trays com- 

 pletely. After the fruit is spread on the 

 trays it should be placed in the evapor- 

 ating chamber as soon as possible. 



There are two essential requirements 

 to evaporation — heated air which is 

 not saturated and some means of pass- 

 ing this air over the material to be 

 evaporated. A\Tiefher this air is heated 

 by means of stoves, furnaces or steam 

 and whether circulated naturally or by 

 means of a fan, the principles employed 

 are the same. It must be remembered 

 that the warmer the air, the more 

 moisture if will absorb. If then the 

 moisture is not being removed properly 

 from the fruit, the remedy will be 

 either to increase the temperature of 

 the air or its circulation. There is a 

 limit, however, to thi^ heat which 

 prunes will stand and ncit scorch. The 

 temperature at the hottest end, where 

 the finished product will be removed, 

 should for best results rarely pass 180 



Continued on pape 11. 



