Formulation of high-value-oil-rich ingredients by citrus pectin and insoluble fiber

The citrus industry is one of southern Italy's most widespread agri-food chains. Starting from citrus, it is possible to squeeze the juice, distill essential oils and finally extract the pectin. The final residue is the insoluble component of total dietary fiber. With this work, the interactions between pectins and insoluble fiber were studied with the goal of obtaining food products resistant to heat treatment, with a wide range of textures and the possibility of implementing lipophilic molecules in them. For this purpose, the manufacturing of emulsion-filled-hydrogels was selected as best potential system using mango puree as dispersing phase to improve taste and nutritional value. First, emulsions at different concentrations of sunflower oil (20 - 25 - 30%) and insoluble fiber (3 - 4 - 5%) were prepared and analysed for the oil droplet’s size (Fluorescence Microscopy) and phase separation after centrifugation (4000 g for 2 minutes) to find the more stable combination. Mango puree, oil and insoluble fiber were mixed at 1200 rpm for 15 min with a mechanical mixer while heating up to 90°C. After 10 min of mixing, four low-methoxy pectins with different degrees of methylation and amidation were added at 1% w/w to create the emulsion-filled-hydrogel. The resulting samples were allowed to cool overnight at room temperature and then subjected to texture and confocal analysis to demonstrate the emulsion-filled-hydrogel formation and investigate consistency and microstructure. The insoluble citrus fiber showed the ability to stabilize the emulsion reaching a D5:3 droplet size of around 15 µm. The final selected formulation was with 1% pectin, 5% fiber, 20% oil, and 74% mango puree. Depending on the pectin type a variety of products with different structural characteristics were obtained. Insoluble citrus fiber can stabilize an emulsion able to withstand the heat treatment necessary to prepare the hydrogel. The final products are oil- and fiber-rich without any added sugar. They can be considered as a texturally versatile way to implement foods with fat-soluble nutrients (e.g. PUFA, D and E vitamins). Further study should be made to investigate potential preserving effects for the oily phase.