Kenaf seed protein emulsion gel with fenugreek seed saponin and tween 20 as co-surfactants: Design, characterization, and bioactive encapsulation

In this work, a comprehensive investigation was performed on the process of fabricating emulgels from kenaf seed protein stabilized with natural (fenugreek seed saponin, FS) and synthetic (Tween 20) co-surfactants using high shear technology. The influence of saponin incorporation on the viscoelastic property, droplet size and morphology, environmental (pH and temperature) stability and simulated digestibility of the emulgels was studied. A lower critical micelle concentration (0.351 g/L) of FS was responsible for its excellent emulsifying nature. Synergistic effects of protein and saponin enhanced interfacial activity by forming emulgels having lower droplet size, homogenous appearance, higher surface charge and greater environmental stability. The emulgel having 4 % protein and stabilized with 1 % FS showed zeta potential of −52.59 mV which was comparable to the corresponding tween 20 stabilized emulgel. Addition of saponin at higher concentration (1 %) reduced the droplet size of the emulgel to a greater extent. The rheological experiment showed that the storage modulus (G’) of saponin stabilized emulgel was higher as compared to the tween 20 resulting in the formation rigid gel structure. Also, the emulgels incorporated with saponin demonstrated greater structural recovery than the only protein based and tween 20 stabilized gel. Apart from Tween 20, saponin being a natural co-surfactant was able to form a stable emulgel tested against different pH and temperature conditions. The firmer gel network formed by higher concentration of saponin and protein enhanced the encapsulation efficiency (89.25 %) and bioaccessibility of β-sitosterol (79.81 %) loaded within the emulgel. These findings offered valuable insights into the use of natural emulsifiers for fabricating and stabilizing emulgels that can serve as an ideal carrier to deliver bioactive compounds. The outcomes of this study highlight the potential of emulgels as versatile carriers for functional ingredients, with wide-ranging applications in the food industry as fat replacers, mayonnaise analogs, and in the formulation of novel dairy and bakery products.