Thermal analysis of plant cell wall materials depending on the chemical structure and pre-treatment prior to drying

Abstract

It is of great importance for the manufacturing of food containing dietary fiber to investigate the connection between process-dependent structural changes and state transitions of plant cell wall materials (CWM) and the resulting functional properties of the products. The chemical structure of CWM from apples was modified by de-methoxylation and charged with sodium ions, respectively. Furthermore, the CWM contained various ethanol concentrations before the drying process (pre-treatment before drying). Changes of structure and functional properties of altogether 12 resulting preparations have been investigated by thermal analysis (TA) and by the determination of the water binding capacity (WBC). The data were analyzed statistically by multiple analysis of variance (factors: "Degree of Methoxylation" – DM, "Sodium Charging" – NaCh, "Initial Ethanol Content" – IEC). Materials with almost structurally unaltered cell walls showed the best thermal stability. Chemical modifications, however, decreased the thermal stability of the pectin matrix as well as that of the cellulose network. Sodium charging primarily effected the stability of the pectin matrix, but de-methoxylation of the pectin matrix directly influenced the cellulose network's stability. The weight loss during TA was mainly dependent on the IEC. It was also shown that a combined data evaluation of TA, WBC and rheological measurements allows a better understanding of state transitions during processing.