Formation, characterization and application of hemp seed protein isolate-alginate complex for the production of hemp seed oil-based products

Polyunsaturated fatty acids (PUFAs) are valued for their role in preventing metabolic disorders, primarily sourced from oily fish for dietary and supplement purposes. However, challenges such as overexploitation and accessibility barriers hinder seafood’s availability, leading to a growing demand for plant-based PUFAs. This shift is also driven by concerns encompassing ecological sustainability, economic viability, ethical considerations, geographical constraints and individual taste preferences which are reflecting a collective effort towards healthier and more environmentally conscious dietary choices. Hemp seed oil (HSO) is recognized as a valuable plant oils rich in PUFAs, specifically linoleic α-linolenic and γ-linolenic acid with an ideal ω-6/ω-3 fatty acid ratio. Despite its nutritional benefits, the high PUFA content in HSO makes it susceptible to oxidation, necessitating the implementation of effective preservation techniques. This study proposes microencapsulation of HSO using protein-polysaccharide complexes as a strategy to mitigate the risks of oxidation. The preliminary phase of this work included solvent extraction to obtain HSO and alkaline extraction/isoelectric precipitation to isolate hemp seed proteins (HPI). The subsequent research aimed to improve HSO nanoemulsion stability by complexing HPI with anionic polysaccharides (carrageenan (CA), alginate (AL), pectin (PC) and gum arabic (GA)) and evaluating their efficacy in HSO microencapsulation. The results indicated that the type and concentration of polysaccharide significantly affected the properties of coated droplets. Nanoemulsions formulated with 0.5% (w/v) protein and 0.01% (w/v) polysaccharide using HPI-AL demonstrated the highest stability and lowest polydispersity index (PDI). Moreover, HPIpolysaccharide nanoemulsions showed high thermal stability with only HPI-AL maintaining stability across all salt concentrations. Consequently, the HPI-AL complex was chosen to encapsulate HSO, yielding liquid microcapsules that were subsequently transformed into powder using the solution-enhanced dispersion by supercritical fluids (SEDS). To enhance the microencapsulation process of HSO, the SEDS method’s parameters were systematically optimized using response surface methodology. The optimum conditions were determined as follows: a temperature of 40°C, pressure of 150 bar and feed flow rate of 2 mL/min, resulting in a microencapsulation efficiency (MEE) of 89.47%, particle size (PS) of 7.81 μm and peroxide value (PV) of 2.91 meq/kg oil. These microcapsules were then compared with those produced via spray and freeze-drying method. The SEDS method proved significantly more effective in producing HSO microcapsules, delivering higher MEE, better oxidative stability and spherical microcapsules with smooth surfaces. Additionally, a comparative study evaluated the performance of HPI against pea and soy proteins in HSO microencapsulation through the SEDS process. HPI-AL was identified as the most efficient carrier matrix with the highest MEE (90.56%), a uniform spherical shape without pores or fissures and an exceptional glass transition temperature. This study concludes that producing HSO nanoemulsions with the HPI-AL complex and microencapsulating them using the SEDS method yields microcapsules with exceptional properties, paving the way for their integration into various food products.

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