Mass spectrometric imaging of localization of fat molecules in water-in-oil emulsions containing semi-solid fat.

Firstly, we report the localization analysis of the lipid components of a water-in-oil (W/O) semi-solid emulsion by mass spectrometry imaging (MSI). Uniform emulsion droplets were prepared using microchannel emulsification devices with lecithin, stearic acid-binding monoglyceride (St-MAG), and polyglycerol polyricinoleate (PGPR) as emulsifiers. The mass image gives us the localization of phosphatidylcholine (PC) in lecithin, St-MAG, tripalmitin (PPP), medium-chain triglyceride (MCT), and high-melting-point triglyceride tristearin (C18-TAG). PC, St-MAG, and PPP were localized at the interface with the dispersed water droplets. PC and PPP took the same localized position, suggesting an interaction between PC and PPP at the interface. Conversely, PC existed in other regions with St-MAG. MSI revealed multiple target molecules in fat products in a single measurement, and it is expected to reveal fat crystallization at the emulsion interfaces, which will clarify the mechanisms related to the physical properties of high-fat products such as fat spread and butter.

Model studies on volatile release from different semisolid fat blends correlated with changes in sensory perception.

The effect of dispersed aqueous droplets in water-in-oil (W/O)-emulsion semisolid fats on aroma release and sensory perception was investigated on margarine models where model aroma substances were added. Aroma release from W/O-emulsion fat blends and bulk fat blends with added monoglycerides combining different fatty acids of various short-chain free fatty acids, methylketones, esters, and lactones were measured using headspace solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS), and their perception profiles were evaluated by sensory analysis. The presence of aqueous phase in a fat blend significantly reduced the headspace concentrations of butanoic acid and hexanoic acid, and also decreased the perceived intensity of total aroma and cheesy aroma. The aroma release of methylketones, esters, and lactones from the W/O-emulsion fat blends increased with increasing carbon chain length of the volatile molecules. The intensity of aroma perception in a W/O-emulsion fat blend depended on the melting point of the fatty acids (oleic, palmitic, stearic, and behenic) of the monoglyceride used as an emulsifier. Thus, aroma release from a W/O-emulsion semisolid fat blend was influenced by interactions between aroma volatiles and the dispersed aqueous droplets and by their viscoelastic properties.