Encapsulation of a PUFA-rich oil in alginate-protein hydrogels

Authors: AKONJUEN, BESSEM - Delaware State University; Wyatt, Victor; Jones, Kerby; Sharma, Brajendra; MARTIN, KATHERINE - University Of Delaware; ARYEE, ALBERTA - Delaware State University

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2025
Publication Date: 6/8/2025
Citation: Akonjuen, B.M., Wyatt, V.T., Jones, K.C., Sharma, B.K., Martin, K., Aryee, A.N. 2025. Encapsulation of a PUFA-rich oil in alginate-protein hydrogels. LWT - Food Science and Technology. https://doi.org/10.1016/j.lwt.2025.117970.
DOI: https://doi.org/10.1016/j.lwt.2025.117970

Interpretive Summary: Njangsa seed oil (NSO) is valued for its high content (73 - 79 percent) of polyunsaturated fatty acids (PUFA) and other bio-active components. The high PUFA content increases the oil's susceptibility to oxidation and reduces its shelf life, limiting its application. Encapsulation has been used to improve oxidative and thermal stability and preserve the functionality and flavor profile of oils. In this study, NSO was encapsulated with various combinations of alginate, a naturally occurring polymer typically obtained from brown seaweed, with proteins extracted from legumes. Various analytical methods were used to determine which optimal combination of alginate and protein isolate improved encapsulation efficiency, gastrointestinal tract release profile, and oxidative stability among other parameters. The results revealed that the encapsulation strategy employed resulted in a vast number of protective properties and had a positive effect on many of the parameters measured. This study suggests that the encapsulation of NSO can be effectively and efficiently designed for incorporation into functional food products; thereby, providing an alternative source of bio-active fatty acids and other components for humans.

Technical Abstract: Encapsulation has been used to improve the oxidative stability of certain oils and control the delivery of bio-active components. The study aimed at optimizing njangsa seed oil (NSO) encapsulation using a three-factor-five-level central composite design (CCD) response surface methodology to determine the effect of alginate (1.5 - 2.5 percent), protein concentration (3 - 6 percent), and NSO load (3 - 6 percent) on encapsulation efficiency (EE). All the independent variables significantly affected the EE of ALG-BPC-NSO capsules. The optimal formulations for NSO encapsulation using alginate-Bambara protein isolate (ALG-BPI), alginate-Bambara protein concentrate (ALG-BPC) and alginate-soy protein isolate (ALG-SPI) carriers were 2.5, 2.5, and 2.8 percent alginate, 3, 5, and 7 percent protein and 6, 6, and 8.25 percent NSO load, respectively. EE, size, and sphericity factor were 88.08, 87.21, and 84.30 percent, 1.98, 2.38, and 1.70 mm, and 0.04, 0.047, and 0.06 for ALG-BPI-NSO, ALG-BPC-NSO, and ALG-SPI-NSO, respectively. Confocal and scanning electron microscopy showed an even distribution of NSO within all the capsules and a highly porous internal surface for ALG-BPI-NSO. FTIR spectra suggested that no molecular interactions were formed between NSO and the encapsulation matrix. ALG-SPI-NSO showed a delayed NSO release, higher total phenolic content (TPC), and higher antioxidant activity during gastric and intestinal digestion compared to ALG-BPI-NSO and ALG-BPC-NSO. Encapsulated NSO had higher TPC and better DPPH and ABTS radical scavenging ability than free NSO, which increased during gastric and intestinal digestion. The higher onset temperature of NSO encapsulated in ALG-BPI compared to ALG-SPI suggest that NSO has better oxidative stability in the former than the latter.