There are many factors to consider prior to processing canned potatoes. Initially, one should perform preliminary tests on the different types of potatoes available such as, a specific gravity test. If the potatoes float in a 1.075 specific gravity solution, it is then considered a better choice for canning. Having a specific gravity of 1.075 to 1.095 or adding calcium chloride will prevent slough from occurring, unless the specific gravity is around 1.100. A potato is considered good for canning if it does not slough or disintegrate during processing. Potatoes are canned either with salt brine or with a starch sauce. The canned potatoes in brine are usually smaller in size. Canned potatoes may diced, sliced, strips, or canned whole. The canning potato process includes the following steps, inspection, washing, size grading, preheating, peeling, inspecting, cutting, filling, brining, sealing, retorting, cooling, casing, and storing.

The potatoes used for canning are normally small tubers, which are not suitable for fresh market. After harvest, these potatoes are separated from the larger sized potatoes. They are then transferred to canneries and processed within a few days. If the potatoes are going to be stored for several days before canning, and then they should be placed in a cooled environment away from light and in a well - ventilated area. This will prevent "greening" and rot. The potatoes may also become discolored due to the high sugar content, which is increased as a result of low temperature storage. Water pollution is an increasing problem in the canning industry, during the peeling step. A new method of peeling without the use of water has been developed and has reduced the water pollution problem.

The first step in canning potatoes is inspection. The second step is washing and preheating the potato in order to remove the dirt, prior to the peeling process. The potatoes are washed using a strong spray of water. The next step is to peel the potatoes; either by abrasion peelers, lye peelers, or high pressure steam peelers. The lye and high pressure steam peelers consist of a two step process, in which the skin and potato immediately under it is softened and then the skin and cooked potato portion are removed by friction and washing. Small operations are the main users of the abrasion peelers. Once the potatoes are peeled, they should immediately be placed under water or a 3% salt solution. This step is performed in order to prevent discoloration of the potatoes. The next step is to fill the potatoes into cans. Boiling hot brine is added to the cans with plain bodies and enameled ends. The brine should completely cover the potatoes. However, salt may be added either in a tablet form or a flake form when hot water is used. The salt content should not exceed 2.0% by weight. After brining the No. 10 cans should be exhausted, however, the smaller sized cans do not need to be exhausted. This will allow the temperature of the No 10 cans to reach a temperature of 140 degrees celcius.

In order to maintain the potatoes quality it is regular practice to add salt tablets which contain 1.4% - 1.7 % CaNa2 EDTA with or without 20% calcium chloride in order to prevent graying discoloration. The discoloration is caused by iron sulfides. The prevention of sloughing is accomplished by adding 0.1% calcium. Calcium is not normally added for tubers with a specific gravity of 1.075.

The canned potatoes are then retorted at a minimum initial temperature of 50 degrees F for 50 minutes and then at 240 degrees F for 47 minutes, 245 degrees F for 38 minutes and  250 degrees celcius for 32 minutes.   The previous set conditions are for a can size of 303 X 406 and smaller.  Once it has been retorted the final step is to  label the can.

References:    Sultan, J.S. Practical Baking 3rd edition, The Avi publishing company, Inc.                        Westport, Conneticut, 1981.     Call number:  TX763  S8  1981

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