Structure-related degradation of pectins and their impact on non-enzymatic browning and technological functionality

• Applicants: Professor Dr. Stephan Drusch; Professor Dr. Lothar Kroh
• Subject Area: Food Chemistry
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268547215

Processing and storage of food lead to chemical and biochemical changes in the biopolymeric constituents. Consequently, their functional properties modified by non-enzymatic browning reactions and oxidative processes. In contrast to reducing sugars, uronic acids as precursors in the Maillardreaction have rarely been studied. Hence, reaction processes, intermediates and reaction products of pectin degradation and their role in non-enzymatic browning reactions should be investigated. In model systems first results show a faster color development of uronic acids in comparison with reducing sugars. However, the hydrolytic and beta-eliminative cleavage does not provide a sufficient explanation. Additionally, the intermediates of the thermal induced degradation of pectins like saturated and 4,5-unsaturated oligogalacturonic acids are not systematically characterized. Regarding to the functional properties of modified pectins, further studies should be of interest. Objective of the project is to investigate and clarify the reaction mechanism of the thermally induced degradation of pectin. More precisely, the influence of the structure of starting materials and conditions used on intermediates formed and their role in color formation by the non-enzymatic browning (Maillard-reaction) should be elucidated. For this reason, different model systems will be used with galacturonic acid and its methyl ester, respectively. The purified partially methyl esterified saturated and unsaturated oligogalacturonic acids should be used separately in further models. Furthermore, the results should provide an insight into the mechanism of pectin degradation and the resultant effect to the physico-chemical characteristics of degradation products. The previously executed differential scanning calorimetry shows anomalies and a mechanism of degradation is postulated. The comparison of chemical investigations and structure-analytical characterizations as a part of the project could confirm our postulated degradation mechanism. Finally, the influence of degradation on functional properties of pectin should be examined. For this reason structures identified by NMR spectroscopy should be compared with results obtained during investigation of physico-chemical properties.

• DFG Programme: Research Grants
• Cooperation Partner: Professor Dr. Clemens Mügge