VEGETABLE AND FRUIT DEHYDRATION 193 



destroyed. This may require 2 to 4 minutes or more as shown in 

 table 21. An undesirable color will develop in the finished product 

 if it is overblanched. If a delay occurs between blanching and de- 

 hydration, it will be necessary to cool the product to 65° or 70° F. 

 by means of cold-water sprays; otherwise the color of the finished 

 product may be injured. The blanched product should not be held 

 longer than 1 hour before being dried. 



Information on the moisture content of cabbage and on the maxi- 

 mum moisture content permitted by Government specifications for 

 dried cabbage can be found in table 22. The drying ratio and drying 

 yield are shown in table 23. Tables 24 and 25 contain information or 

 dehydration, and table 26 on container requirements. 



Hot packing of dehydrated cabbage tends to preserve the size of 

 flakes by lessening breakage, because the dried shreds are more pliable- 

 when hot. The packaged product requires protection from both mois- 

 ture and air. To meet Government specifications, the air in cans 

 must be displaced (type 1, p. 123). The vacuum-chamber-and-pump 

 method of removing air is recommended, and it is preferable that the 

 vacuum chamber be equipped with a sealing head; reduction below 



2 percent of oxygen would make this type of equipment necessary. 

 The reasons for a maximum of 2 percent of oxygen are urgent. The 

 purpose of air displacement is to save the flavor, color, and ascorbic 

 acid by the elimination of oxygen. Analysis should be made at least 

 12 hours after the cans are filled and sealed. 



In commercial practice, removal of air by displacement with carbon 

 dioxide from a cylinder without a meter has produced irregular re- 

 sults, ranging from 1.5 to 8 percent of oxygen in the gas left in the 

 filled can. Records obtained with an inexpensive iron-case gas meter 

 have shown that 1 cubic foot of carbon dioxide will reduce the oxygen 

 content of gas in the filled can to 1.8-2.4 percent in 10 seconds or 1.2-1.6 

 percent in 30 seconds ; 2 cubic feet will reduce it to 0.8-1.0 percent in 60 

 seconds. 



In general dehydrated cabbage is one of the less stable of the dehy- 

 drated vegetables. In storage tests Savoy cabbage that was blanched 

 in steam, dried to 3.7 percent moisture content, and stored in carbon 

 dioxide or nitrogen at 90° F. became inedible within 16 weeks. At 

 temperatures of 70° to 80°, four varieties blanched and dried to below 



3 percent moisture content retained both palatability and ascorbic 

 acid without material loss. Tests with varied moisture content have 

 shown that palatability and ascorbic acid are retained better at low 

 than at higher moisture content. 



In rehydrating dried cabbage it is best to subject it to a moderately 

 long soaking, followed by a relatively short boiling or cooking period. 

 When the material is to be used raw as salad or cole slaw, slightly 

 longer soaking may be required. In rehydrating samples for testing, 

 add 1 part by weight of dried cabbage to a consistent weight of water 

 (10 to 15 parts). Soak for 1 hour; then simmer for 10 to 20 minutes 

 in the same water. Drain through an 8-mesh strainer and weigh. 

 The drained weight will be approximately 8 to 12 times the original 

 weight of vegetable. Longer soaking will give a plumper product and 

 slightly greater weight. Longer boiling may cause deterioration in 

 flavor and color. 



569074—44 13 



