The following information with regard to "Fruit Drying," published in leaflet form by the South African National Union, will no doubt prove useful to our readers.
Sun drying is the least expensive and easiest method, but the product must not get damaged by rain. If fruit once gets wet the colour is partly ruined, and it becomes useless for commercial purposes. In a hot climate like that of the Transvaal and the O.F.S. sun drying would be very effective if only satisfactory precautions could be taken against rain.
As a general rule, however, the summer weather in the inland areas is too uncertain. Fruit must be picked when it is in the right stage, and dried at once; one cannot wait for a sunny day. And even if drying trays are covered during rain the moist air prevailing for some time afterwards is quickly re-absorbed by the fruit, with the resultant danger of mould and decay.
Another drawback to drying in the sun is the opportunity presented to flies and other insects for laying eggs and excreta amongst the fruit. The use of an evaporating machine prevents all this.
It is recognised, however, that until small evaporators are available at moderate prices simpler methods must be adopted.
In drying fruit the essential things are heat and free circulation of air; both are necessary. The principle of drying is to subject the product to a current of warm dry air, absorbing the moisture, which is afterwards driven away. This result is most easily attained by a process of artificial heat.
Fruit dried by air, with an ordinary electric fan, requires about three days, whilst if part of the moisture is first driven off by the fan and the process then finished by slow artificial heat in an oven, in an evaporator, or in the sun, the work can be completed on the second day. The wind can also be turned to advantage. With a dry light breeze, free from dust, a better finished product is obtained than with the fierce heat of the sun only. The sun draws out the moisture and the dry wind wafts it away.
As an electric fan is seldom available on the farm, a simpler method is necessary. An inexpensive frame for outdoor drying can be made in the following manner:
In the sunniest spot near the house drive four posts, the front ones two feet and a half high, the rear ones four feet high. To these attach three shelves about four inches apart, made of 1/2 or 3/8 inch mesh chicken wire or other screening. Across the back nail a sheet of galvanised iron. On the top place an old window frame. Around the sides nail cheesecloth which, while keeping out dust and insects, will permit a circulation of air and help to carry off moisture.
Arrange one side of the cheesecloth so that it can be removed and the fruit placed on the shelves.
After the last meal of the day has been cooked, the heat of the oven, instead of being wasted, can be used to dry fruit or vegetables. Take out the oven shelf, put in the drying tray with its charge of fruit and leave it all night, with the oven door ajar. In the morning remove the tray, but if the contents are not thoroughly dry put the tray back again the following evening.
Trays may be made of the size required by nailing together four wooden laths and stretching wire gauze, canvas, or hessian previously washed, across the frame work. Fruit should not be done in a moderate warm oven. It is essential that the heat should not be sufficient to scorch the fruit.
Drying by artificial heat improves the colour of fruit. It is the saving in drying that saves the colour. The longer fruit takes to dry the darker it gets.
At the same time the drying process must not be too rapid. Rapidity of evaporation often means imperfectly dried fruit, cooked on the outside and untouched within.