This section is from the book "Save It For Winter.", by Frederick Fry Rockwell. Also available from Amazon: Save It For Winter; Modern Methods Of Canning, Dehydrating, Preserving And Storing Vegetables And Fruit For Winter Use, With Comments On The Best ... For Saving, And When And How To Grow Them.
(1) Obtain the products, as for canning, as fresh, young and tender as possible. Pick over and grade carefully; wash all products that may need it and thoroughly clean and peel or scape root products to avoid possibility of strong acid flavor in the dry products.
(2) Slice, cut, shred or "pulp" the product, as may be required.
(3) Blanch, or par-boil and cold-dip, as required, and place in trays ready for drying.
Fig. 16 - Slicing or cutting the product to be dehydrated is a vital part of the process. A rotary slicing machine like this, which is being used to cut sweet potatoes into strips, is a great time saver.
Fig. 17 - An electric fan and home-made wooden trays complete this simple but effective "dehydrating plant." in which several products may be dried quickly at one time.
(4) Dry carefully for the required length of time-examinations should be frequent and occasional turning may be necessary. Be sure to keep sun-dried products carefully protected at all time from dust or moths. The product should be taken in each night before sunset and put out each morning after the dew is off. There should be a protecting cover of light cheese-cloth-mosquito netting is not fine enough-which should be kept over the product to prevent moths or other insects from depositing their eggs, with the result that a large part or all of the product may be spoiled afterward while in storage. The "Indian meal moth," which is about 3/8 of an inch in length and is gray and copper-brown in color, is the insect which causes most injury to dry vegetables and fruits. A close second is the "fake moth," about the same size, but a darker gray. Both are night flyers and are likely to attack the product about dusk. The eggs hatch within ten days, with a new generation about every two months thereafter; so that just from a few eggs originally the whole product may be completely spoiled.
In evaporating by heat, care should be taken to avoid too high a temperature at first, as this may cause the freshly cut surfaces to be sealed up, with the results that the pieces do not dry out evenly and a poor product results. Start the heat slowly and raise it gradually to 140 to 150 degrees. This is high enough to do the drying as rapidly as it should be done, and will also destroy any insect eggs which may be present. To keep track of the degree of heat in the drier a thermometer, preferably an oven thermometer, should be used. If you do the work without a thermometer, it is risky, as the temperature varies rapidly and scorching may be the result.
When dehydrating by air-current, for reasons already explained, a high temperature in the drying of vegetables or fruit is objectionable. They will not dry, even if a correspondingly longer time be given them, without a fairly rapid movement of the air about them. This is because the moisture evaporating from the freshly cut surfaces soon saturates the air, which acts like a blanket and checks the evaporation. The result is that the right conditions for the growth of molds are created, and the product is soon spoiled. If, however, the moisture-saturated air is removed-by having a current of air blown over the vegetable-as fast as it is saturated, evaporation will continue at a rapid and steady rate until the product is uniformly and sufficiently dry. with large commercial evaporators, great care has to be taken not to take out too much of the moisture; but there is little danger of this with the home air-blast equipment. The layer of products should not be so thick that they will not dry through evenly, and, if necessary, should be stirred up or turned over occasionally.
Fig. 18 - A small open pan evaporator of the double-boiler type. The water in the bottom pan prevents scorching the product and makes more uniform drying possible.
(5) Remove from drier. Experience only, in this as in many other things, will teach the operator just when the right condition or degree of dryness has been obtained. In commercial dehydrating, from seven to twelve per cent, of the water content is allowed to remain in the product. There is no way of determining this in the home drier; but one of the tests, to show when this condition has been reached, is to snap one of the pieces and see if it is impossible to press any of the juice from the freshly cut end. The natural "grain" of the vegetable or fruit should also have disappeared; but it should not be so dry as to be absolutely brittle; it should be, rather, slightly leathery.
(6) It is necessary also, to get a product that will keep well and that will not mold, to have it dried uniformly through and through, when the product has been dried sufficiently, as nearly as can be judged, "condition" it for a day or two, if necessary redrying all parts that appear to be still too moist.
Fig. 19 - A self-contained evaporator of larger capacity for use out of doors. The drier or evaporator is mounted on the top of a simple stove. These driers are large enough for commercial work.
(7) Put the product in the containers in which it is to be kept. If the product has been sun dried, it should be sterilized before being stored by heating to a temperature of about 140 degrees F. If dried by artificial heat or air-current, the product should be heated again for a short time after conditioning, as an added precaution. All con tainers for dried products need not be air-tight, but they must be tight enough to protect the contents from outside moisture. Having small containers is of advantage in many ways. A pint jar of the dried products will go several times as far as a, pint of canned products. It is advisable not to have the package so large that the contents, after it is once opened, will not be used in a comparatively short time. In case of insects, also, the damage is likely to be localized if small containers are used. For many things paper bags make satisfactory containers if they are filled only about half-full, the upper portion of the bag being twisted tight, bent over and tied with a string. A wide fiat brush and melted paraffin may be used to paint the bags over to protect them against penetration of moisture; or paper bags may be used and these kept in tin or other containers to protect them, one bag being taken out at a time. An ordinary tin pail or lard pail will accommodate a number of bags, sufficient for a good many meals.
Label everything carefully; labeling is important even in canning, but it is easier to distinguish what the canned goods are than dried products. Have the labels ready to tag everything as it is put up; and until you are familiar with the work of drying or dehydrating, it will be well to put on the labels also, data as to the length of time the product was dried, etc., as a guide for future work.
Fig. 20 - Dehydrated white potatoes ready to be put in containers for storing.
Fig. 21 - Dehydrated string beans ready to be put in containers for storing.
Fig. 22 - Dehydrated peas ready to be put in containers for storing.
(8) Examine before storing. Products which seem perfectly dry when put away, sometimes will be wet after they are put into the containers-with the result that they will begin to mold almost immediately and be spoiled. As a precaution against this, a sample of all products put away should be examined carefully about twenty-four hours after being packed; if there is any sign of moisture being present still, the batch must be put back for further drying.