Behaviour of Agricultural Products in High Hydrostatic Pressure Regimes

Olaosebikan Layi Akangbe

Disertační práce

Abstract:

In this study, exponential functions for estimating densification requirements for whole seeds and powdered forms of Lens culinaris Medik. and Cicer arietinum L. in regions of high hydrostatic pressures ranging between 50-500 MPa and at a deformation rate of 5.5 mm.min-1,given depths of product charge corresponding to an aspect ratio of 0.5 at product moisture contents of approximately 12% , in dry basis, were established. A 4 X10 full factorial experimentfitted into a completely randomised design for the analysis of variance and comparison of treatment means using Duncan’s multiple range test was adopted. Both product form and applied pressure had highly significant effects on mechanical response in the compressed materials, except for the effects of pressure on the rate of strain, and of the interaction of the forms of the product with applied pressure on strain rate and the time to peak deformation.The modified Gompertz function was found to provide a proper fit for pressure-density relationship (R2=0.99). All the parameters of this model had highly significant effects inestimating the pressure as a function of density. The effect of the model at predicting this behaviour was found to be highly significant (p<0.0001). The development of radial or lateral wall pressure during compression presented a very steep slope, at the initial stages and a much gentler slope in the pressure range between 400-500 MPa. Gain in bulk density appreciated with increased magnitude of applied pressure and was higher for whole seed forms than forpowders. Energy requirement for compressing these materials increased as did the magnitude of applied pressure and varied for the different product forms, being lower for powders than for whole seeds; the time rate of expenditure of energy for every unit mass of material was however greater for powders than for whole seeds. Mean compressed product densities of between 1277.6-2060.6 kg.m-3 were achieved with the range of pressure employed. When thecombined effects of pressure, the time rate of deformation and aspect ratio were considered, at applied pressures of 50 and 100 MPa, deformation rates of 5.5, 10 and 14.5 mm.min-1 and aspect ratios of 0.5, 1.0 and 1.5 with Ceratonia siliqua L., at 4.81% moisture content, in dry basis, mechanical response was found to be affected significantly by the different levels of each of these factors and by their interactions. The rate of strain and specific power requirement for the densification of this product were found to be power functions of the aspect ratio, at all rates of deformation. Gain in bulk density was found to be better at the lower aspect ratios. However, energy efficiency improves significantly as aspect ratio increases. The findings in this study are of direct relevance to the development of modified food forms. Immediate applications are with respect to combined high pressure and short duration high temperature edible snack and cereals production systems. Mechanical behavior of biomaterials given high pressures is of importance in postharvest product handling, storage and food processing.

Keywords

compressibility, bulk density, deformation, hydrostatic pressure, strain

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 14. 2. 2019

Obhajoba závěrečné práce

• Vedoucí: prof. Ing. Radomír Adamovský, DrSc.
• Oponent: František Kumhála, prof. Dr. Ing., Jaroslav Buchar, externi

Česká zemědělská univerzita v Praze

Technická fakulta

Doktorský studijní program / obor:
Zemědělské inženýrství / Engineering of Agricultural Technological Systems