Mechanisms of mechanical oil expression from rapeseed and cashew.
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Date
1979-02
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Publisher
University College Dublin
Abstract
The conventional theory of oil expression from vegetable oilseeds suggests that before substantial oil expression can occur, the oilseed cellwalls have to be ruptured by a combination of physical (crushing) and thermal (cooking) pre-treatments. Results from oil expression tests using rapeseed and cashew on the Instron Universal Testing Machine have suggested an alternative mechanism in which up to 80% oil is expressed through a porous cellular
microstructure under pressure without cellwall rupture and at ambient temperature. The porous
mission electron microscopy. The cellwall pores (plasmodesmata) were of diameter 0.87 and 0.126 pm wall surface area for rapeseed and cashew respectively.
The oil expression process has been successfully described by a mathematical model based on three modified form of Terr.aghi's equation for the consolidation of saturated soils., to describe the behaviour of the consolidating oilseed cakej the Hagen Poiseulle equation for flow of fluids
to describe the flow of oil through the pores on the cellwall; and The model has Darcy 's law of flow of fluids through porous media to describe the flow of oil through the intra-kernel voids. in pipes, fundamental equations: a oil expression can occur, the oilseed cellwalls and average porosity of 0.093 and 0.171% of the cellnature of the cellwalls has been confirmed by trans been succeafully applied to experimental data which has revealed that the flow of oil across cellwalls in the seed kernel was the rate determining step. In addition the model was also used to analyse the performance of hydraulic and screw expellers. The study has suggested that the design of both hydraulic and screw expellers could be improved by incorporating an undrained compression pretreatment to rupture cellwalls 3 and by reducing the drainage area to 0.5% - 1.5%. Furthermore^ improved strategies for oil expression have been suggested in two cases, (a) For mechanical expression followed
by solvent extraction it is proposed that the physical (pre-crushing) and thermal (cooking) pre-treatments be replaced by an undrained compression pre-treatment.
are not r equired (b) where mechanical expression is the sole process^ the pre-crushing pre-treatment should replaced by an undrained compression pre-treatment.
Description
PhD Thesis
Keywords
Mechanical oil expression, Cashew, Vegetable oils