In this article:
A number of factors involved in the ground drying of sultana raisins to give an acceptable moisture content (‘finishing off ‘) were studied. Drying responses were related to the potential for water movement from the fruit to the surrounding air as determined by vapour pressure differentials.
The direct input of solar radiation energy during the day raises berry temperatures and increases the vapour pressure differential, thus drying occurs.
The results show that drying is unduly retarded and non-uniform when fruit is spread in layers exceeding 25 mm that is. Covering the fruit at night to protect from dew is unnecessary, as the moisture uptake by berries at night is very slow because at the lower temperatures the potential for water movement into the berries is small, and the dew on the surface evaporates once solar radiation increases in the morning.
As the season progressed from March to May, conditions for drying became less favourable as both the intensity of the solar radiation and day length decreased, thus reducing both berry temperatures and the length of drying time per day.
Effects of Time of Season, Fruit Depth and Covering at Night when Ground Drying, on Acceptable Moisture Content of Sultana Raisins
1984, Journal of the Science of Food and Agriculture, vol 35, pages 173-181
Please note accessing PDF may be slow, thank you.
