Effects of processing conditions on the release of sodium chloride from fat crystal ‘shell’ stabilised water-in-oil emulsions

Abstract

Over the last two decades, water-in-oil fat crystal stabilised Pickering emulsions have been increasingly studied for the controllable release of encapsulated (water-soluble) species. The stability inherent to Pickering emulsions has been shown to be enhanced by sintering to form an interfacial lipid 'shell' around the droplets, which improves the retention and prolongs the delivery of the enclosed species. Using a scraped surface heat exchanger/pin stirrer setup, the present work shows that processing conditions used to produced W/O emulsions with dispersed droplets enclosed in lipid shells, have a significant impact upon the subsequent release of NaCl enclosed within them. The best performing emulsion structure produced here is reported to retain about 98% of its initial salt load over a period of 100 days. NaCl release profiles were also used to calculate the interfacial rate constants for the transferal of salt across the lipid shells. Interfacial rate constants ranged from 5.5 to 3593.2×10−3 nm2/s and were significantly (up to three orders of magnitude) lower than those reported in literature for similar systems. Analysis revealed that depending on the specific conditions employed, the processing environment can enhance or compromise lipid shell integrity. Overall, the current study offers significant direction in terms of the optimum processing requirements that are necessary to produce fat-continuous emulsion microstructures that can successfully regulate the release of NaCl, paving the way for the successful development of food formulations of controlled salt-perception.