Andrzej DOWGIAŁŁO
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: drying, feed, concentrates.

Abstract.
The lack of literature data relating to drying of plant-fish feeding concentrates, more and more frequently encountered on the market, was the reason for undertaking this research the objective of which was to determine the relationship between the input parameters of the process of hot-air drying of plant-fish feeding concentrates in a chamber drier and their moisture content. The knowledge of this relationship is a necessary condition for a conscious control of the drying process of such concentrates under the industrial conditions. In the tests, mashes were used at ratios of fish component to plant component of 3:1 and 2:1, based on feed sprat and wheat bran, preliminarily ground to particles of an equivalent diameter of 3.5-4.5 mm. The mashes were dried within the following ranges of input parameters: air temperature T � [100; 160] [�C], air stream velocity (air flow parallel to the surface of the sample) v � [0.8; 1.2] [m � s^-1], drying time t � [1,200; 4,800] [s], and the thickness of the dried layer h � [0.015; 0.030] [m]. The achieved results made it possible to determine the relationship between the dry weight content in the product in a function of drying parameters grouped into dimensionless numbers, and to plot drying curves for different values of input parameters. Based upon them, the process of hot-air drying of plant-fish feeding concentrates can be not only consciously controlled, but also optimized with respect to the criterion adopted.