Fabricating and characterization of bambara protein nanocarriers for njangsa seed oil encapsulation

Abstract: Njangsa seed oil (NSO) contains various bioactive compounds, making it suitable as a functional food ingredient. However, its potential is limited due to its highly unstable polyunsaturated fatty acid (PUFA) content. This study aims to enhance the oxidative stability of NSO through encapsulation by ionic gelation with extrusion using sodium alginate (ALG) solely or in combination with Bambara groundnut protein isolate (BPI) as wall materials. Microcapsules produced using ALG and ALG-BPI resulted 73.76 and 76.30% encapsulation efficiency (EE) and 57.99 and 61.48% loading capacity, respectively. The physical properties of the microcapsules, including moisture content, water activity, hygroscopicity, and density, were 1.0%, 0.536, 0.21 g/100 g, 0.47 g/cm³ and, 1.16%, 0.523, 0.17 g/100 g and 0.45 g/cm³ for ALG-NSO, and ALG-BPI-NSO, respectively. The L*, a*, and b* values for ALG-BPI-NSO and ALG-NSO were 26.57, 0.63, 6.60 and 48.50, 2.70, and 2.87, respectively. Confocal microscopic analysis indicated an even distribution of NSO within the ALG-BPI-NSO microcapsules. About 18.50 and 22.29%, and 65.80, and 78.51% of NSO were released from ALG-BPI-NSO and ALG-NSO during simulated gastric and intestinal digestion, respectively. The free fatty acid content, peroxide, para anisidine, and 2-thiobarbituric acid reactive substances values of encapsulated NSO were lower than those of the free oil throughout the 21-day study period. Also, NSO encapsulated in ALG-BPI showed better oxidative stability than encapsulated with alginate alone. The study provided valuable information on designing alginate-Bambara groundnut protein isolate-based effective delivery system for njangsa seed oil.