Preservation of oleic acid entrapped in a condensed matrix of high-methoxy pectin with glucose syrup

This investigation deals with the diffusional mobility of essential fatty acids in triglyceride form (oleic acid) from a condensed matrix comprising 3% (w/w) high-methoxy pectin and 81% (w/w) co-solute (glucose syrup) to absolute ethanol. Work utilises rheological measurements in shear, differential scanning calorimetry, ESEM, FTIR and WAX diffraction to identify the molecular properties of the composite system. Results showed that the amorphous carbohydrate matrix underwent vitrification at -15 °C (mechanical Tg) calculated mathematically using the Williams, Landel and Ferry (WLF) and modified Arrhenius equations. Diffusion kinetics of the fatty acid (monitored via UV-vis spectroscopy) was combined with the newly introduced concept of spectroscopic shift factor to demonstrate that, although the increment of oleic acid mobility appeared to respond to the predicted glass transition temperature, this is distinct from the structural relaxation of the matrix. Experimental observations were further treated with the concept of diffusion coefficient to provide an estimate of the transport rate of the triglyceride as a function of time or temperature of observation within the glass transition region.