Sodium alginate-based composite gel beads encapsulation of algal oil emulsion: enhancing DHA bioaccessibility and reducing fishy odor

Algal oil, an eco-friendly and DHA-rich substance, is limited in market applications due to its fishy odor and low DHA bioaccessibility. This study investigated the effects of combining sodium alginate (SA) with carrageenan (C), Arabic gum (AG), or xanthan gum (XG) on the hardness, digestibility, and flavor controlling of gel beads encapsulating algal oil emulsion. The SA/other polysaccharides ratio of 0.8/0.2 was selected based on comprehensive evaluation of viscosity, hardness, and morphological uniformity. Under this ratio, SA-C, SA-AG and SA-XG exhibited distinct digestibility during in vitro digestion. SA-C gel beads showed the highest free fatty acids (FFA) release rate, with DHA bioaccessibility of 86.85%. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses revealed that SA-C gel beads possessed a highly amorphous structure and relatively weak hydrogen bonds, consistent with the larger pore sizes after digestion and lower resistance to oil release observed compared to SA-AG and SA-XG gel beads. A 60-day storage experiment further demonstrated that gel bead encapsulation significantly ( P  < 0.05) reduced malodorous substances such as (E, E)-2,4-heptadienal by 76.26%, effectively alleviating the fishy odor.