STUDY OF THE MECHANICAL RESISTANCE OF THE SUNFLOWER (HELIANTHUS-ANNUUS L) SEED WITH A VIEW TO DEHULLING - INFLUENCE OF MOISTURE-CONTENT ANDORIENTATION

The fitness of sunflower seed for dehulling was studied with whole see ds at three moisture contents (6, 11, 17 p.cent) and three orientation s of the seed (length, width and thickness). Various characteristics o f the seed -histological, physicochemical, mechanical - were determine d, the most significant being the force required for crushing the seed pericarp, the deformation ratio, the dissipated energy, the stiffness of the set hull-kernel and the elastic component of the seed. The see d orientation and moisture content significantly affect the mechanical resistance of the seed pericarp. The most favorable mechanical charac teristics (high stiffness 51.10(-5) N.m-2 and high degree of elasticit y 69,9 %, low deformation ratio 8,6 % and low energy required for crus hing 14 mJ) are obtained when the stress is longitudinally oriented an d at a low seed moisture content. The pericarp preferably breaks throu gh the parenchyma tissues.