Physical characterization of high methoxyl pectin and sunflower oil wax emulsions: A low-field ~1H NMR relaxometry study

摘要

Pectin-wax-based emulsion systems could be used to form edible films and coatings with desired water permeability characteristics. Pectin is often used in food industry due to its gelling and viscosity increasing properties. Physical properties of pectin are highly dependent on its esterification degree. Waxes are commonly used as edible coatings to enhance the water barrier properties of food products. This study focuses on preparing emulsions with sunflower oil wax (SFW) and high methoxyl pectin (HMP) at different concentrations for any possible edible film or coating formulations. Sunflower oil (SFO) was added as the dispersed oil phase to these emulsions. Characterization of the emulsions was performed by using particle size, rheology, and time domain nuclear magnetic resonance (NMR) relaxometry measurements. Effects of HMP concentration and the presence of SFO in the emulsion formulations were explored. Mean particle size values were recorded between 1 and 3 μm. Rheology measurements showed that increasing HMP concentrations and presence of SFO in emulsions resulted in more pseudoplastic behavior. NMR transverse relaxation times (T_2) were measured to detect the differences between the emulsions. Relaxation spectrum analysis was also conducted for a detailed understanding of the transverse relaxations. Addition of SFO and higher HMP concentrations decreased the T_ 2 values of the emulsion systems (P ＜ 0.05). However, T_2 decreasing effect of SFO was compensated at 10% (w/w) HMP concentration showing that SFO was well dispersed in this particular emulsion formulation. Changes in the rheological behavior and relaxation times provided insight on the formation and stability of the emulsions.