PRESERVATION OF FRUITS AND VEGETABLES 27 



thermometer whose bulb was buried in the spinach. In 3 minutes 

 more time the steam was shut off. A maximum temperature of 196° 

 was thus reached, the ports and dampers were then opened, and in 

 4 hours' time the product was completely dried. 



End Point of Dehydration 



Dehydrated fruits and vegetables should have a uniform moisture 

 content low enough to inhibit undesirable microbic and chemical 

 changes within the food, and they should be free from any part of the 

 life cycle of moths or other insects. The moisture content of dehy- 

 drated foods directly controls deterioration within the food, and the 

 protection afforded by sulfuring or blanching will not prevent insuffi- 

 ciently dried products from soon becoming unfit for use. Dehydrated 

 products having a low moisture content are not readily attacked by 

 insects. In the long run the additional protection afforded by a low 

 moisture content will more than make up to the producer the loss 

 resulting from the longer drying time and greater weight shrinkage 

 involved. To assure best keeping qualities the moisture content of 

 fruits containing much sugar should not exceed 15 to 20 percent, while 

 that of other fruits and vegetables should not exceed 5 to 10 percent, 

 the preference in both cases being for the lower percentage. 



The texture, or feel, of products is a guide in determining when the 

 proper stage of dryness has been reached. At a given moisture 

 content products usually feel softer when hot than after they have been 

 cooled, and often they feel softer after standing until the moisture has 

 become evenly distributed throughout the pieces than when first 

 cooled. 



A rough test for moisture in dried fruits is to take up a double 

 handful, squeeze it tight into a ball, and release the pressure. If the 

 fruit seems soft, mushy, or wet, and sticks together when the pressure 

 is released, the moisture content is probably 25 percent or more. If 

 the fruit is springy and, when the pressure is released, separates in a 

 few seconds to form pieces of approximately the original size and 

 shape, the moisture content is usually about 20 to 25 percent. If the 

 fruit feels hard or horny and does not press together, falling apart 

 promptly when the pressure is released, the moisture content is 

 probably below 20 percent. 



At the proper stage of dryness vegetables look thoroughly dry and 

 are often hard or crisp. 



The Association of Official Agricultural Chemists has published a 

 method for the determination of moisture in dried fruits (1). In 

 using methods of this type, care must be taken to select a composite 

 sample from different parts of the lot, so that it will be representative 

 of the lot as a whole, and directions for preparing the sample must be 

 carefully followed in order to obtain dependable results. 



CURING 



Products are never uniformly dry when removed from the drier. 

 Large pieces and pieces not as directly exposed to the currents of 

 heated air as most of the material contain more moisture than the 

 rest. Products should be stored in large bins until the moisture 

 becomes evenly distributed. This period of curing will usually take 



