Preparation and characterization of pectin polysaccharides-containing Gardenia extract with dual functionality in food gel formation and coloring for 3D printing application.

Pectin polysaccharides play an important role in food processing as thickeners, gelling agents and emulsifiers. However, complex extraction processes, the need for multiple purification steps, low yields and high costs, etc. limited their application in food industry. In addition, the byproduct of food processing - gardenia residue from the oil processing industry - still contains valuable substances such as pectin polysaccharides and natural pigment crocin. This study utilized a simple, economical and eco-friendly water extraction (WE) method to efficiently obtain extracts containing pectin polysaccharides, crocin and other high-value components from gardenia residues. The WE extract demonstrated superior performance in higher content of both pectin polysaccharides (27.20 ± 0.10% vs 20.80 ± 0.53%) and crocin (5.33 ± 0.30 vs 3.01 ± 0.05 mg/g) as well as antioxidant activity (p < 0.05) than ethyl acetate-ethanol-water sequential extraction (ESE) extract. Importantly, extracts could form the gel with high sucrose in an acidic environment owing to the high methoxyl pectin (DE > 60%) of extracts, and WE extract exhibits good viscoelasticity and strength. The gel of WE extracts was successfully used in 3D printing. Interestingly, the prepared gel had visually appealing color due to the crocin, which adds another new function of the extract. The preparation of extract with dual functionality provides new perspectives and ideas for the recovery and utilization of valuable components from other residues.