Fabrication of rice bran oil nanoemulsion and conventional emulsion with Mustard Protein Isolate as a novel excipient: Focus on shelf-life stability, lipid digestibility and cellular bioavailability

Abstract

Proteins are one of the many effective biomolecules found in oilseed meals. In order to formulate an oil-in-water nanoemulsion based lipophilic nutraceutical delivery vehicle for Rice Bran oil (RBO) rich in γ-oryzanol, we used mustard seed meal protein isolate (MPI) as a novel natural surfactant together with a small molecular weight co-surfactant Tween 20 in various ratios (3:1, 1:1, 1:3) to stabilize the heterogeneous system. The oxidative stability, physico-chemical characterization in response to pH and ionic strength, shelf-life, and storage of the nanoemulsions containing 1% surfactant in total, comprising different ratios of MPI and Tween 20 were optimised to form an efficient biphasic surfactant system. The oil-in-water nanoemulsions fabricated utilizing high energy approach, i.e. high pressure homogenisation method was found to reduce dispersed phase particles size in the range of 150–160 nm. Minimal non-significant variation in droplet size and surface charge over the 8 weeks storage periods proves their excellent shelf-life stability. The use of MPI as surfactant for the delivery system also increased the lipid fraction digestibility releasing 70% of the fatty acids from dispersed phase oil droplets in simulated intestinal phase of three step in vitro digestion of nanoemulsion as compared to its conventional counterpart. The γ-oryzanol rich nanoemulsions improved prophylactic effectiveness against ROS in terms of overall cell survival and cell membrane integrity. The results will pave new domains to use MPI as surface active agents for delivery system formulation enriched with nutraceuticals and phytochemicals possessing superior functional advantages, bioavailability and antioxidative potentials.