Preparation of oil-structured materials as alternatives to solid fats using chitin nanofibers

With the improvement of living standards, people are increasingly demanding a healthy diet. Some of the most popular foods with unique tastes, such as saturated and trans fatty acids, have been found to have negative effects on human health, prompting people to seek their alternatives. In this study, oleogels were prepared to replace these two kind of solid fat using chitin nanofibers, and the influence of nanofiber morphology on oleogels were systematically studied. Firstly, chitin nanofibers were prepared through dissolution, degradation and regeneration processes, and their morphology was adjusted by controlling their molecular weight. SEM and XRD showed that these regenerated nanofibers have damaged microstructure and rearranged network, exhibiting obvious larger lattice plane spacing and smaller crystallite size. Chitin nanofibers with high molecular weight (79.6 kDa) are prone to aggregating into bundles and even form membranes, while nanofibers with reduced molecular weight tend to form locally short-range networks and even aggregate into nanofiber microspheres. When these chitin nanofibers were transferred into camellia oil, they exhibited excellent gelation effects. The resulting oleogels show different rheological properties, among which the oleogel prepared by chitin nanofibers with the medium molecular weight (42.4 kDa) showed the most stable rheological properties. Even at a concentration of only 2.5%, its storage modulus (9072 Pa) and viscosity (7.98 × 10 5  mPa·s) were much higher than those of the 8% beeswax oleogel and the 13% stearic acid oleogel. In addition, the prepared oleogels all exhibit good thermal stability below 280 °C, and its structural transformation under shear force is independent of the concentration, and is only affected by the morphology of the nanofiber. Our study provides new opportunities for the application of solid fat substitutes in food industry. Graphical abstract