Abstract
Antarctic krill oil (AKO) with 5–30% (w/w) dilution by soybean oil was co-emulsified by phospholipids (PLs) naturally present in AKO and 2% (w/w) casein in the aqueous phase to prepare high internal phase emulsions (HIPEs). The results showed that raising the AKO level resulted in concave-up changes in the mean size of oil droplets which became more densely packed. Confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (cryo-SEM) micrographs revealed that PLs at higher concentrations expelled more casein particles from the oil droplet surface, which facilitated the formation of a crosslinked network structure of HIPEs, leading to reduced mobility of water molecules, extended physical stability, and somewhat solid-like behavior. The rheological analysis showed at lower levels of AKO promoted fluidity of emulsions, while at higher levels it increased elasticity. Lastly, increasing the AKO level slowed down the oxidation of HIPEs. These findings provide useful insights for developing HIPEs of highly viscous AKO and its application in foods.
Highlights
Antarctic krill oil (AKO) contains considerable amounts of bioactive minor components such as astaxanthin, sterols, tocopherols, vitamin A, flavonoids, and minerals [1], as well as a high content of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) that are present in phospholipids (PLs, 39.89% to 80.69%), which mainly comprise phosphatidylcholine (PC, 44.58% to 99.80% of total PLs) and phosphatidylethanolamine (PE, 0.20% to 24.74% of total PLs) [2]
In the present study, foodgrade high internal phase emulsions (HIPEs) of AKO carried by soybean oil were prepared using casein as a co-emulsifier together with PLs in AKO
The effect of the casein concentration in the continuous phase on the formation of HIPEs was investigated by using soybean oil as the oil phase
Summary
Antarctic krill oil (AKO) contains considerable amounts of bioactive minor components such as astaxanthin, sterols, tocopherols, vitamin A, flavonoids, and minerals [1], as well as a high content of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) that are present in phospholipids (PLs, 39.89% to 80.69%), which mainly comprise phosphatidylcholine (PC, 44.58% to 99.80% of total PLs) and phosphatidylethanolamine (PE, 0.20% to 24.74% of total PLs) [2]. The semi-solid viscoelastic structure of HIPEs that is formed by high accumulation and crosslinking of the oil phase makes the emulsions highly stable and resistant to creaming. Based on the abovementioned observations, we hypothesized that PLs naturally present in AKO may interact with an added protein in the oil–water interface and enhance the protein’s emulsifying properties. On this basis, in the present study, foodgrade HIPEs of AKO carried by soybean oil were prepared using casein as a co-emulsifier together with PLs in AKO. To understand a possible underlying mechanism of the emulsion formation, the microstructure, particle size, rheological properties, and stability of the emulsions were investigated
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