Fat crystals: A tool to inhibit molecular transport in W/O/W double emulsions

Abstract

Water‐in‐oil‐in‐water (W/O/W) double emulsions are a promising technology for encapsulation applications of water soluble compounds with respect to functional food systems. Yet molecular transport through the oil phase is a well‐known problem for liquid oil‐based double emulsions. The influence of network crystallization in the oil phase of W/O/W globules was evaluated by NMR and laser light scattering experiments on both a liquid oil‐based double emulsion and a solid fat‐based double emulsion. Water transport was assessed by low‐resolution NMR diffusometry and by an osmotically induced swelling or shrinking experiment, whereas manganese ion permeation was followed by means of T2‐relaxometry. The solid fat‐based W/O/W globules contained a crystal network with about 80% solid fat. This W/O/W emulsion showed a reduced molecular water exchange and a slower manganese ion influx in the considered time frame, whereas its globule size remained stable under the applied osmotic gradients. The reduced permeability of the oil phase is assumed to be caused by the increased tortuosity of the diffusive path imposed by the crystal network. This solid network also provided mechanical strength to the W/O/W globules to counteract the applied osmotic forces.

Production of reduced‐fat whipped toppings by solid fat‐based W/O/W double emulsions: proof of concept

“…30/20/50 (w/w/w) W/O/W double emulsions were prepared in a two‐step emulsification procedure as described by Nelis et al (). In the first step, a 60/40 (w/w) water‐in‐oil (W/O) emulsion was produced by slowly adding (over 1.5 min) an aqueous solution (W 1 ) containing 0.1 m KCl and 0.02 wt% NaN 3 to the oil phase, while mixing for 7.5 min in total with an Ultra‐Turrax (IKA Werke) T50 basic rotor G45F at a mixing speed of 5200 r.p.m.…”

“…The emulsion globule size distribution was determined using a Mastersizer 3000 (Malvern Ltd, Great Malvern, UK). The used method and parameters are described by Nelis et al (). For O/W emulsions, the dispersion unit was filled with distilled water.…”

“…The repression constant (τ o ) for the oil phase was determined using bulk oil samples and was 47.45 ms. The method is described in detail by Nelis et al ().…”

“…This FID‐CPMG sequence allows for determination of the water content (WC) of the sample and determination of the dispersed‐phase volume fraction (DVF). The model used to fit the FID‐CPMG data consisted of a Gaussian function in combination with multiple exponential functions as described in detail by Nelis et al (). Data processing was done by a CONTIN‐based analysis with the freely available MATLAB script (rilt.m) using MATLAB R2018a software.…”

“…As far as we know, the production of a quiescent stable, yet whippable, W/O/W emulsion, to produce a low‐fat whipped topping has never been studied before. In general, a limited number of research papers are found in literature studying W/O/W emulsion formulated with crystallising fats (Garti et al , ; Weiss et al , ; Guery et al , , ; Frasch‐Melnik et al , ; Pérez et al , ; Herzi & Essafi, ; Nelis et al , , 2019b). Pérez et al () investigated the stability of W/O/W emulsions under quiescent conditions and concluded that globule aggregation by partial coalescence was facilitated by PGPR.…”