Influence of friction, sample dimensions and deformation rate on the uniaxial compression of raw potato flesh

Abstract

The influence of surface fricyion lubrication on the compresion behaviour, at compresion rates of 5-100 mm min-1, of cylindrical samples of potato flesh have been axamined with an Instron Universal Testing Machine at room temperature. The samples had lenght/diameter ratios of 0.2-0.8. Parameters derived from compression to failure were: failure stress; failure strain; and apparent modulus of elasticity. Stress relaxation with time was studied using samples with lenght/diameter ratios of o.4-0.8 folowing compressions of 10 an 30%. The lenght/diameter ratio, rate of compression, surface friction and lubrication influenced the parameters derived from both the compression and the stress relaxation test. Relaxation times increased following sample lubrication. The effect due to surface lubrication was smaller than in previous compression and relaxation tests on Gouda cheese. This was attributed to release of fluid from the damaded cellular tissue of the potato flesh wich reduced the effectiveness of the lubricant film.