Effect of Pectolytic and Cellulolytic Enzyme Treatments on Functional and Nutritional Properties of Cell Wall Materials from Apples

Abstract

Cell wall materials prepared from apple parenchyma tissue by treatment with commercial pectolytic and cellulolytic enzyme preparations were characterised in model experiments. During maceration and mash fermentation, apple tissue was decomposed mainly into single cells whereas enzyme action under conditions of liquefaction led to cell fragments. The macrostructure of the plant material was preserved after maceration and mash fermentation due to water-ethanol exchange as pre-treatment for drying. The porosity decreased and the solid density increased with advancing enzymatic degradation of the cell walls. This increasing degradation decreased the galacturonan content and the degree of methylation of the pectin component. It was possible to remove pectin from the cell wall matrix completely under optimal conditions of the enzymatic liquefaction process. Cell wall material prepared by maceration showed high water binding and excellent rheological properties, which were however reduced with increasing enzymatic degradation of the materials. The thermal stability of the pectin matrix as well as the cellulose network were nearly independent on a previous enzyme treatment. The advancing enzymatic degradation, however, results in an decreasing relative weight loss of the pectin matrix (first degradation step) and an increasing weight loss of the cellulose network (second degradation step) during thermogravimetry. During in-vitro fermentation of the cell wall materials with human faeces flora a spectrum of short-chain fatty acids (SCFA) was formed. With decreasing amounts of pectin HLthe cell wall materials, the total concentration of SCFA decreased whereas the portion of butyrate increased. Cell wall materials prepared from parenchyma tissue by specific enzymatic treatments have beneficial functional properties and are dietary fibre materials with interesting physiological effects.