Hypothesis: There is a recognized technological need for delivery systems encapsulating lipophilic substances in food and pharmaceutical products. Pickering emulsions can provide well-defined and highly stable systems, but may not provide good enough barrier properties. Starch granules, recently being used for Pickering stabilization, have the advantage of the ability to swell during gelatinization. Hence, this property could be used to tune and control barrier properties.
Experiments: Oil-in-water Pickering emulsions stabilized by starch were subject to heat treatment at different conditions. The influence of temperature, time, and storage on emulsion drop characteristics was evaluated. In order to further evaluate the barrier properties, lipolysis using the pH-stat method was applied and the effect of starch concentration, treatment temperature, and preliminary oral conditions were also investigated.
Findings: A better encapsulating barrier was obtained by starch swelling at the oil drop interface. This was seen as reduced lipase activity. The internal oil drop size remained intact and the starch was kept at the interface during heat treatment. The extent of swelling could be controlled by the heating conditions and had impact on the ability to prevent lipase transport through the starch barrier layer. Addition of α-amylase simulating oral digestion only had minor impact on the barrier effect.
Keywords: Barrier properties; Encapsulation; Gelatinization; Lipolysis; Pickering emulsion; Starch granule.
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