Impact of 3D/4D Printing and Electron Beam Post-Processing Parameters on Rheology, Printability, and Microbiological Safety of Lupin Protein-Based Gel Emulsion

Abstract

The broader use of lupin proteins in food products is hindered by formulation challenges despite their recognized nutritional and techno-functional advantages. The aim of this study is to develop lupin protein-based gel emulsions suitable for 3D/4D food printing using electron beam (eBeam) technology as a non-thermal preservation strategy to enhance microbiological safety and shelf life without relying on chemical preservatives. Eight formulations were made with varying protein content (20 and 25%, P), xanthan gum (2.0 and 2.5%, XG), and allulose (6 and 12%, AL). Rheological properties, including storage and loss moduli, and polydispersity index were evaluated to ensure printability and post-printing stability, while FTIR spectroscopy was used to monitor protein structural modifications. 3D-printed structures were baked at 170 °C for 16 min for 4D transformation and subsequently treated with 5 kGy eBeam dose. Microbial shelf life was assessed through aerobic and anaerobic plate counts, mold and yeast analyses, and quality changes were monitored by colorimetric measurements during storage. Among the formulations tested, 25P-2.5XG-6AL and 20P-2.0XG-6AL exhibited superior printing fidelity and physical stability. Electron beam processing significantly extended microbial shelf life up to 8–10 weeks, with no detectable mold or yeast growth observed in 25P-2.5XG-6AL throughout storage. Color stability was also improved, with perceptible changes (ΔE > 3.5) occurring only after week 8 in irradiated samples. These findings demonstrate that lupin-based gel-emulsions are suitable for 3D and 4D printing, exhibiting enhanced physical and microbial stability after eBeam processing, supporting the development of safe, clean-label plant-based foods with extended shelf life.