Some people will desire to sulphur their fruit, which is quite an innocuous practice, although in some countries considered harmful. Sulphur has always been looked upon as beneficial to mankind from the days of infantile brimstone and treacle to the sulphur springs in later life.
The object of "sulphuring" is to fix the colour. Afterwards fruit retains its natural colour for a much longer period than can be attained in any other way. Also, any insects present are destroyed, and the fruit rendered less liable to damage from this quarter, a serious consideration in the South African climate.
When a sufficient number of trays are full they should be placed in an air-tight box and exposed to the fumes of sulphur for a short time. A sulphur box is easy to make; it should just fit the trays, and contain slats on each side on which to slide the trays in and out. Ordinary tongued and grooved timber lined with paper makes a good box. It should be fairly air-tight but not completely so, as without some air the sulphur will not burn. The sulphur should be placed in a vessel in the centre of the box, and lighted, the trays put in, door closed securely, and the fruit left for forty minutes, more or less. The quantity of sulphur to be used depends, of course, on the size of the box; 1/21b. is sufficient for a box 6x4x4 inside measurement. Galvanized wire netting should not be used in a sulphur chamber, as it causes a chemical action that makes the fruit injurious.
The drying trays should not be large. A tray 3 x 6 needs two people to handle it, while one 3 x 3 can easily be moved by one person. 3/8 inch mesh wire netting nailed over a wooden frame makes an excellent tray.
This can be done where electricity is available to drive an electric fan. The drying process is considerably shortened by it. Sixty per cent. of the moisture can be removed in ten hours. The fan is placed on the table directly in front of the box containing the products which are intended to be dried, which should be spread on small trays with plenty of ventilation between them. Afterwards place the products on an ordinary drying tray in the sun or in the oven. When rain threatens the trays should be placed on top of one another so that air can pass through, and protected from the wet by a substantial covering.
If it is not certain that the fruit is sufficiently dry to keep, place some overnight in a clean dry glass jar and add a crisp cracker biscuit. If, in the morning, the cracker has lost its crispness, is soft and damp, there is still too much moisture in the fruit, and it should be dried an hour or two longer.
Do not pack away the product at once, but for two or three days move it from one box to another to bring about thorough mixing. If, during this time, which is called "conditioning," and places are found to be too moist, return them to the trays for further drying.