Exploring citrus fiber as an emulsifying agent: Synergy with low methoxyl pectin and amidated pectin for advanced food formulations

Citrus fiber consists of the residue remaining after primary citrus processing and pectin extraction. While the emulsifying properties of this byproduct and the gelling abilities of pectins are well known, research has primarily focused on their interactions within emulsions. However, the technological properties of a gelled emulsion system had never been investigated. This study focused on the synergistic interaction of citrus fiber, mango puree, sunflower oil, and four distinct low-methoxyl pectins within an emulsion-filled hydrogel. Low-methoxyl pectins were chosen for their gelling ability at low sugar concentrations, allowing the formulation of products aligned with specific dietary needs. Mango was selected as an illustrative fruit-based dispersing phase to assess the applicability of citrus fiber in a realistic food system. First, the research engaged in homogenization conditions and resilience to heat treatment at 90 °C. Various combinations of fiber and oil were tested to minimize both droplet size and phase separation, identifying 5 % (w/w) citrus fiber and 20 % (w/w) oil as the most stable formulation. The emulsifying ability of citrus fiber was found to be linked to the water-to-fiber ratio, which had to be lower than the water binding capacity. Then, the emulsion-filled hydrogel was created from the previously optimized emulsion using four different pectins (1 % w/w). Among them, only the amidated low-methoxyl pectin with a higher degree of methoxylation was capable of forming a self-standing gel. The findings indicate that the texture of a hydrogel comprising insoluble citrus fiber and pectins is primarily influenced by the citrus fiber rather than the pectin. However, when citrus fiber acts as a heat-resistant emulsifier, the addition of pectin imparts unique characteristics, allowing the modulation of the final product's consistency.