Thermal and high pressure high temperature processes result in distinctly different pectin non-enzymatic conversions

Pectin is a common, extremely complex and process sensitive polysaccharide in plant cell walls with many uses as an additive in the food and biomedical industry. Process induced chemical changes in pectin result in various effects on its functionality. An in-depth study is presented of the effects of thermal compared to HP/HT (high hydrostatic pressure combined with high temperature) processing on pectin nano-structure and characteristics. The results obtained emphasized the necessity of taking into account pectin association and conformation in solution when analyzing molecular weight changes. At a pH of 6.3, a decrease in molecular weight was observed for both thermal and HP/HT treated samples but with partially different reasons. While for the thermally treated samples the reduction in molecular weight was mostly due to pectin depolymerization for the HP/HT treated samples a significant effect was observed for conformational changes induced by electrostatic repulsion caused by the complete demethoxylation of the polymer. On the contrary due to conformational changes, an increase in the observed molecular weight was noticed for HP/HT treated samples at a pH of 4.4. The study also clearly shows the necessity of combining an absolute molar mass determination method like multiangle laser light scattering (MALLS) in studies on the effect of processing on pectin.