128 MISC. PUBLICATION 5 10, U. S. DEPT. OF AGRICULTURE 



Sealing 



Dehydrated vegetables and fruits that are packaged in tin cans are 

 hermetically sealed, even when packed in air. Formerly the stud hole 

 was covered with a lid and a tight joint was made by soldering, but 

 more recently, because of the shortage of tin and the lower percentage 

 of tin in solder, the trend has been toward the use of square cans 

 with mechanically formed seams. These seams are of two types, 

 double seam and single seam. With both a sealing compound is used 

 on the surfaces subject to closure, in order to produce an hermetic seal. 

 An hermetic seal may be tentatively denned as one that is gasproof, 

 moistureproof, and bacteria-tight, both initially and throughout a 

 common period of handling and storage. Shipments of 5-gallon cans 

 of dehydrated products are frequently made across mountain passes 

 7,000 feet high; in a trip of this sort a sealed can filled at sea level 

 would be subjected to 3y 2 pounds per square inch of internal pressure. 

 Tests show that when a leaky can is packed with carbon dioxide at sea 

 level, shipped over a 5,000-foot pass, and returned to sea level, the 

 oxygen content may be expected to increase 4 percent. 



Seaming machines for 5-gallon square cans have been developed by 

 several companies and can be leased. Machines will seal at rates be- 

 tween 6 and 18 cans per minute (fig. 63) . 



Packaging in Cartons 



The equipment and methods recommended for cartons vary some- 

 what from one supplier to the other. An inner carton of banding 

 chipboard must be assembled and taped at the bottom, and the carton 

 is then filled and the top is taped. A lead-foil bag is expanded into 

 shape on a mandrel and the filled carton is slid into the bag on an 

 inclined chute. The package is placed in an erect position and passed 

 on a roller conveyor through a heat sealer, where the envelope is 

 deflated by suction or other method. The "ears" of the envelope are 

 folded over, a strip of folding U-shaped chipboard is placed over the 

 bottom and the sides, and the unit is thrust into the outer carton, 

 which is then sealed, and the seams at the end are covered with cloth 

 tape. 



Labeling Packages and Cases 



The labeling of packages is described in Government contracts, 

 which in general require the name and type of product, the net weight 

 in pounds, the month and year of dehydration, name of packer, loca- 

 tion of processing plant, and specific directions for rehydration. Part 

 of the foregoing is repeated on the packing cases. 



It is important that finished boxes be stenciled daily ; if for example 

 inspection reveals too high a moisture content, the number of cases 

 involved will be fewer if only 1 day's product has been grouped and 

 stenciled together. 



Cases 



Materials for cases and methods of packaging are included in Gov- 

 ernment specifications. For overseas shipment, packing cases undergo 

 3 to 5 times as much handling as for domestic shipments. A loaded 

 case that withstands 40 drops of 1 to 3 feet in a tumbling drum 7 feet 

 in diameter is safe for domestic use, but must withstand 120 to 200 



