Stabilization of Fish Oil‐in‐Water Emulsions with Oleosin Extracted from Canola Meal

Abstract

International dietary guidelines advocate replacement of saturated and trans fat in food with unsaturated oils. Also, there is growing interest in incorporating highly unsaturated omega-3 oils in to food products due to beneficial health effects. A major obstacle to incorporating highly unsaturated oils in to food products is the extreme susceptibility to oxidative deterioration. Oil bodies were prepared from tuna oil, oleosin, and phospholipid mimicking natural oil bodies within oilseed. Oleosin was extracted from canola (Brassica napus) meal by solubilization in aqueous sodium hydroxide (pH 12) and subsequent precipitation at its isoelectric point of pH 6.5. The tuna oil artificial oil bodies (AOBs) readily dispersed in water to produce oil-in-water (o/w) emulsions, which did not coalesce on storage and were amenable to pasteurization using standard conditions. Accelerated oxidation studies showed that these AOB emulsions were substantially more resistant to lipid oxidation than o/w emulsions prepared from tuna oil using Tween40, sodium caseinate, and commercial canola protein isolate, respectively. There is potential to use commercial canola meal, which is cheap and abundant, as a natural source of oleosin for the preparation of physically and oxidatively stable food emulsions containing highly unsaturated oils.

The Effects of Oil Extraction Methods on Recovery Yield and Emulsifying Properties of Proteins from Rapeseed Meal and Press Cake

“…Protein was recovered from cold-pressed RPC, hot-pressed RM, and solvent-extracted RM (Figure 1). The protein recovery procedure was identical for all raw materials used and was modified from the procedure previously described by Wijesundera [31]. The rapeseed press cake or meal was stored in a freezer (−18 • C) until the start of the protein recovery processes.…”

“…Three batches were prepared for each raw material with and without heat treatment in the recovery process. from the procedure previously described by Wijesundera [31]. The rapeseed press cake or meal was stored in a freezer (−18 °C) until the start of the protein recovery processes.…”

“…It is well-known that increased pH in the extraction phase is associated with higher protein recovery yields, with a pH of 12 yielding the highest protein recovery [31,34,35]. However, it is neither industrially nor environmentally feasible to use a pH of 12 in the extraction process, and therefore a pH of 10.5 was used in our study as a compromise between high protein recovery yield and respect for environmental factors.…”

Canola/rapeseed protein-functionality and nutrition

“…Working with somewhat pure protein, Wu and Muir (2008) and Cheung et al (2014) showed cruciferin (>80% purity) possesses better emulsifying ability than napin (Cheung et al, 2015). Wijesundera et al (2013) demonstrated that canola protein extracted at alkaline pH (12) and recovered by precipitating at pH 6.5 can stabilize O/W emulsions. Emulsions of tuna oil stabilized by this canola protein product showed that the unsaturated lipids can be protected against oxidation.…”

Mimicking natural oil bodies for stabilising oil‐in‐water food emulsions

“…Basically, canola protein is first solubilised in strong alkali (pH 12.0) solution followed by adjustment of the pH to the isoelectric point of oleosin (6.5) to precipitate oleosin together with any other canola proteins co‐precipitating at this pH. Oleosin concentrates extracted in this manner can then be used to construct OBs with any oil of interest by mixing the oil with oleosin and phospholipid in proportions similar to those occurring in natural OBs . The highly hydrophobic nature of oleosin prevents preparation of o/w emulsions in the conventional manner by mixing aqueous solutions of protein with oil.…”