The effect of electrical processing on mass transfer and mechanical properties of food materials

摘要

In this research work, the effect caused by electrical processing on mass transfer in food materials was studied by designing and performing experiments that allowed the visualisation of: the effect of moderate electrical fields (MEF (leq)1000V cm(^{-1})) on mass transfer in cellular materials; the effect of MEF on mass transfer of solutes to polymer networks; and the effect of MEF and pulsed electrical fields (PEF) on mechanical properties of polymer networks. udMEF treatment was performed with continuous alternating current (50Hz frequency) at electrical fields up to 1400V m(^{-1}) using a jacket system processing cell to maintain constant temperatures. PEF treatment was performed with a pulse generator at Lund University, Sweden. Extraction of betanin from beetroot was monitored online and measured by spectrophotometry. Mass transfer of rhodamine6G into gel networks (alginate, albumin and gelatine) was measured by image analysis. Effective diffusion coefficients (D(_{eff})) for mass transfer of betanin and rhodamine6G were estimated, assuming Fickian diffusion was valid. Mechanical properties of alginate and gellan gum treated with MEF and PEF were studied. Compression force of gel samples was measured with texture analysis. udResults showed that the application of MEF and thermal treatment had an enhancing effect on the extraction of betanin from beetroot. The orientation of the beetroot slab also appeared to have an enhancing effect on extraction when the slab was placed perpendicular to the electrical field. The application of MEF had a decreasing effect on mass transfer of rhodamine6G to gel networks set with ions. Mass transfer decreased as electrical field increased. This effect was influenced by electrical conductivities of the gel and rhodamine6G solution. No significant effect of MEF was observed on gelatin or albumin. MEF and PEF had an increasing effect on compression force of polymer networks.