VEGETABLE AND FRUIT DEHYDRATION 43 



ment purchase specifications for dehydrated cabbage provide that the 

 product shall be so sulfited that it contains sulfur dioxide within the 

 limits of 750 to 1,500 parts per million. 



Sulfiting of white potatoes and carrots has been under consideration, 

 but up to the present specifications have not been issued in which toler- 

 ances for sulfur dioxide have been included. The sulfiting of white 

 potatoes does not present unqualified advantages. From the stand- 

 point of acceptable palatability they tolerate substantially less sulfite 

 (perhaps not over 500 p. p. m. as S0 2 ) without exhibiting an un- 

 desirable sulfur flavor in the reconstituted product. Moreover, the B 

 vitamins are unstable in the presence of sulfites, and potatoes lose these 

 vitamins when so treated. Application of sulfite to some potatoes 

 may result in better color as the product comes from the dehydrator 

 and also better retention of quality through storage under adverse con- 

 ditions. Carrots will probably respond more favorably to sulfite 

 treatment than potatoes, from the standpoint of improved storage 

 characteristics, and will probably tolerate a higher content of sulfur 

 dioxide without undesirable sulfite flavor. 



Apart from the beneficial effects that sulfiting offers in the retention 

 of quality, it has made possible the use of higher finishing tempera- 

 tures in dehydration and consequently shorter drying times. Particu- 

 larly with cabbage, finishing temperatures 10° to 15° F. higher can be 

 employed safely without scorching, as compared with unsulfited cab- 

 bage. This has reduced the drying time as much as one-third in 

 some cases. The effect is also observed with onions, potatoes, and 

 carrots. 



It is possible to accomplish the sulfuring by any one of several 

 methods. In England where blanching is done by immersion in hot 

 water, it is relatively easy to incorporate the sulfiting treatment by 

 merely adding sulfite salts to the blanching bath and maintaining 

 the desired concentration by addition of salts at fairly frequent inter- 

 vals. The Canadians also have recommended the immersion proced- 

 ure and the Australians and New Zealanders have experimented both 

 with dipping and with application by spraying the trayed product. 

 In the United States blanching is done almost exclusively in con- 

 tinuous-belt steam blanchers or in cabinet or pressure retort units, 

 also with steam. Application of sulfite by any dipping technique 

 thus requires the addition of another operation to a processing se- 

 quence already firmly established. Since by far the greatest number 

 of blanchers used in this country are of the continuous-belt type, 

 efforts were first directed to the development of a spraying procedure 

 which could be made an integral part of the blanching operation and 

 equipment. This has been successfully accomplished with cabbage 

 and the method has been used in the production of more than a half 

 million pounds of dehydrated sulfited cabbage up to the present 

 time (1944). 



The method involves application of a sulfite solution by means of a 

 spray on the cabbage as it is conveyed through the steam blancher. 

 Application to the raw shredded cabbage before it enters the blancher 

 has not proved desirable because of relatively poor absorption of 

 sulfite. Undesirably high concentration of sulfite salts must be used 

 in the solution if enough uptake to give 750-1,500 p. p. m. in the 

 dried product is to be achieved. On the other hand application to the 

 blanched product as it emerges from the blancher will result in very 



