Synthesis of a sustainable marine oleogel and its application as a fat substitute in a sponge cake system

Oleogel technology offers a promising solution for reducing trans fatty acids in food by solidifying liquid oils. However, this technology encounters challenges due to limited vegetable oil resources. This study explores the use of sustainable fish oil, a by-product of sardine canning, especially the saturated fatty acid from the biowaste of PUFA purification, as a liquid phase in oleogels. Beeswax and rice bran wax were tested as oleogelators at concentrations of 5, 10, 15, and 20%. The 20% rice bran wax oleogel exhibited superior gelation properties, reached 90% oil binding capacity, and improved pore distribution without affecting volume ( p > 0.05). A sponge cake prepared with commercial margarine (0% oleogel) displayed similar characteristics to a sponge cake with oleogel substitution in terms of hardness (∼6 N), springiness (∼25 mm), cohesiveness (0.4), gumminess (2-3 N), and chewiness (74 J). This indicated that the oleogel substitution mimicked and yielded margarine-like textures. The increasing concentration of oleogel substitution slightly decreased hedonic scores from ∼8.3 to ∼6.6 (from 'like very much' to 'like slightly'). Importantly, the sponge cake with 25% oleogel substitution exhibited high acceptability and overall liking similar to the 0% oleogel (commercial margarine), both scoring at approximately 8. Moreover, the specific texture attributes of the generated sponge cake, such as roughness, moistness, and smoothness, were demonstrated to be similar and comparable to those of commercial margarine, particularly at 25% and 50% oleogel substitution levels. Lipolysis during the in vitro digestion of the sponge cake revealed a reduction in the release of free fatty acids, decreasing from 93.01% to 62.79% with oleogel substitutions ranging from 0% to 75%, respectively. Consequently, the total energy of the product decreased by 14.26% with a 75% oleogel substitution. These findings offer an opportunity to utilize by-products from fish canning for the development of higher-value products. Specifically, this involves constructing an oleogel with a new liquid-phase system while simultaneously reducing margarine consumption. In comparison to other available reports on the utilisation of fish by-products, our study places emphasis on the sequential valorisation of fish oil biowaste after its initial use as the PUFA source. This approach represents a novel way to address challenges in achieving a zero-waste concept in industry related to Sustainable