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The Centrifugal separation of apple cell serum Coltart, Michael Logan


Factors affecting the centrifugal separation of apple parenchyma cell serum were investigated for three important cultivars from the Okanagan Valley of British Columbia; Mcintosh, Red Delicious, and Winesap. The factors studied included cultivar, maturity, maceration treatment, and centrifugation time and speed. Observations included yield of cell serum, relative serum clarity, pulp and serum viscometric properties, alcohol insoluble solids, soluble solids, serum pH, particle size and tissue firmness. The pulp viscometric property, viscosity at a shear rate of 100 sec⁻¹, was the observation which primarily influenced juice yields. The increased separation obtained for Mcintosh > Red Delicious > Winesap was attributed to pulp viscosity values. Relative serum clarity was influenced by serum soluble solids when centrifugation time was constant at six minutes or by the serum pH and pulp viscosity at maturity one (0 storage). Increased centrifugation speed and time markedly improved the yield of cell serum for the factors evaluated. Maceration treatments reduced the average particle diameter from 330 μm to 229 μm and the pulp viscosity values. At 5,500 and 8,000 rpm, higher yields were obtained when the particle size was small. At 10,500 rpm or 14,500 rpm, higher serum yields were obtained with larger particle sizes. Consideration of the particle size (> 100 μm) and shape (non-spherical), along with sedimentation theory indicated the separation followed Newton's Law. The high yields obtained with the larger particle size at high rpm confirmed a low drag force coefficient (C[sub D] = .5). Although a slight reduction in particle size and viscosity was observed when parenchyma tissue was subjected to ultrasonic vibration, no improvement was obtained in serum yield or clarity. The centrifugal separation of apple parenchyma cell serum was shown to be feasible. The efficiency of the separation improved as pulp viscosity decreased and speed or time of centrifugation increased. The tissue particle size evaluated was of secondary importance for the separations observed.

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