VEGETABLE AND FRtttT DEHYDRATION 41 



Stacks connected directly to the blancher either at the ends or at 

 the midsection are undesirable. They serve no useful purpose and are 

 in fact detrimental to the blanching process, because live steam is 

 induced to escape. Unattached hoods located at the two ends are 

 desirable to take away unavoidable steam leakage. Some leakage of 

 steam is necessary, however, to insure a full chest of air-free steam. 



If water-wash or sulfite-spray sections are provided either before 

 or after the blancher, these should not be constructed so as to cause a 

 draft in the blancher. A satisfactory practice is to eliminate the tunnel 

 cover over the water-wash or sulfite-spray sections. A heavy canvas 

 curtain should be provided at both ends of the blanching section so as 

 to minimize leakage. 



Spreading the product on the blanching belt or trays can be ac- 

 complished manually or mechanically. For mechanical spreading, 

 use is made of revolving brushes or drums, stationary bars (straight, 

 angular, or curved) , or vibrators and shakers. At least two additional 

 procedures are in common use. The material discharged from the 

 cutter may pass into a water flume which empties on the front end of 

 the blancher belt. The water drains through the belt into a sump, 

 leaving the cut material in a uniform layer on the blancher. Another 

 method uses the momentum of the vegetable pieces as they come from 

 the cutter. The discharge spout is removed and replaced by a suitably 

 shaped deflector plate. Proper use of this method on diced vege- 

 tables gives a satisfactory spread over a width of three feet or more. 



The multiple-belt blancher, as its name implies, comprises a number 

 of belts. The product is dropped from one belt to the other as it 

 progresses through the blancher (fig. 20). It has the advantage of 



3> 



C — D 



Figure 20. — Multiple-belt blancher. 



being considerably more compact than the ordinary continuous 

 blancher. Designing such a blancher, however, is a difficult task and 

 requires considerable mechanical skill. Because of multiplicity of 

 parts and the alternate stresses produced in the side walls of the unit, 

 it cannot be readily constructed of wood. 



Retort blanching requires a means of subjecting cut vegetables to 

 steam above atmospheric pressure. This method is quick and positive ; 

 however, the equipment is costly and, being essentially a batch process, 

 must be supplied in duplicate so as to produce a steady flow of product. 

 The labor required also may limit its use in dehydration. Improve- 

 ment in product quality resulting from this process is probably neg- 

 ligible and the method cannot be justified unless retorts are available 

 and other equipment cannot be procured. 



Summary of olanchers. — Of the various types of blanchers now em- 

 ployed in the dehydration industry, the simplest and most commonly 

 used is the belt blancher. If this unit is modified for use as a con- 



