In recent years, 3D food printing has garnered significant attention in the field of food engineering. A major challenge in advancing this field is the accessibility of functional printing devices, which are essential for conducting experiments and exploring novel applications. While commercial printers or those based on the RepRap project are widely used, this study explores an alternative approach by utilizing factory automation (FA) components to assemble a 3D food printer. The printer features a syringe-based extrusion system capable of handling various food paste materials. A belt-driven system controls the horizontal movement of the printing head, while a lead screw mechanism enables precise vertical positioning of the printing stage. Performance tests demonstrated that high-viscosity and highly compressible food paste materials could be accurately extruded by incorporating nozzle purging and retraction into the extrusion system. Printing tests using rice flour paste, cream cheese, and potato starch gel confirmed that the printer achieved sufficient precision for research purposes. The total cost of the mechanical and electrical components was approximately 390,000 JPY, with design and assembly times of 80 and 40 hours, respectively. This open-source 3D food printer provides researchers with a practical alternative for exploring new applications in 3D food printing technology.

To increase conversion rate of isoflavone glucosides to aglycones in okara through solid-state fermentation with lactic acid bacteria (LAB), we investigated the effects of alkali treatment to okara on hydrolyzation of isoflavone malonylglucosides. After incubation of okara in a solid state at various pH adjusted with sodium hydroxide solution, malonyl groups of malonylglucosides were most effectively hydrolyzed at pH 11.0. As a result of the alkali treatment, the proportion of β-glucosides in the total isoflavones in okara increased from 32.1% to 86.4%. After fermentation of alkali-treated okara with Lacticaseibacillus casei, 93.3% of the total isoflavones were converted to aglycones, which were 1.8-fold higher than those of untreated okara. Moreover, similar hydrolysis of malonylglucosides was observed when potassium carbonate solution was used. Thus, the combination of alkali treatment and fermentation with LAB could be one of the useful practical methods to increase the isoflavone aglycones contents in okara as a food material at low energy costs.