RHEOLOGICAL PROPERTIES OF BEDS OF RAISINS

The rheological properties of beds of Sun-dried Sultana and Corinth ra isins equilibrated to various moisture levels were investigated. Raisi n beds of fixed bulk density at various configurations were compressed in a cylindrical rest cell, and the apparent modulus and the two cons tants of an empirical model were estimated from the linearized stress/ strain and relaxation curves. Beds of black Corinth raisins were more elastic than Sultana (seedless) raisins at moistures lower than 18%, b ur both types of raisins showed similar rheological behavior at higher moistures. The unrelaxed stress of all beds, after 10 min of relaxati on, was about 25% of the initial stress. Beds of randomly mixed raisin s of different moisture content appeared to be more elastic when the p roportion of the moist raisins was increased. The apparent modulus of columns of raisins decreased as the number of raisins per column and t he number of adjoining rows were increased.