Valorization of edible industrial and agricultural food byproducts for rheological properties and 3D printability in food inks

Food waste generated from food manufacturing byproducts and agricultural surplus is a pressing global concern, leading to the loss of valuable nutrients and environmental challenges. This study explores the use of different hydrogels as a sustainable carrier for incorporating this edible food by product commonly regarded as food waste into 3D food printing (3DFP) inks, aiming to reduce nutrient wastage while promoting sustainable practices in food manufacturing. Four types of food waste – okara, sesame cake (SC), brewer's spent grain (BSG), and butterhead lettuce, were investigated for their particle morphology, water hydration capacity (WHC), and tap density. These properties are crucial as they determine the rheology and printability of the 3DFP ink. Rheological evaluations identified 5 % w/v thermoplastic (TPS) gel as the optimal base material, offering favorable gel-like properties, good structural integrity and flowability during printing during extrusion 3DFP. Among the tested inks, 20 % w/v BSG and lettuce exhibited the most consistent and stable printing performance, with mean viscosities of 4016.7 mPa·s and 6330.4 mPa·s at a shear rate of 100 1/s. Okara, which has the highest WHC led to ink drying and instability, even at reduced concentrations, while SC's high density caused nozzle clogging due to particle agglomeration and separation from gel phase. This study demonstrates the potential of valorizing food waste by leveraging its fiber and protein content to create functional 3DFP inks. By transforming zero-cost food waste into printable food inks, this research offers innovative solutions for sustainable food preparation, reducing landfill waste, and advancing environmentally responsible manufacturing methodologies.