Bacteria reduction and quality improvement of 3D printed fresh carrots by inner design and moderate microwave treatment

Abstract Bacteria reduction and quality change of 3D printed carrots with different infill percentages (%) were studied after being treated with microwave (MW) at three power levels (120, 230, and 390 W). The color, appearance, texture (hardness, chewiness, and gumminess), and total polyphenol contents (TPCs) were comprehensively evaluated. The results showed that infill levels had no effect on bacterial population reduction but significantly affected the appearance of the samples after MW treatment. The total number of colonies (TNCs) were decreased by 0.27–0.68 (120 W, 60 s), 2.24–2.48 (230 W, 60 s), and 4.27–4.54 (390 W, 60 s) log CFU/g under the three MW treatments, respectively. 390 W MW treated achieved a very significant effect on inoculated Escherichia coli , with a death rate of 81.13%. MW treatment enhanced the hardness, chewiness, and TPC of the printed carrots as well as improved sticky mouthfeel without adversely affecting the visual color. The bacterial reduction effect of MW 390 W treatment for 60 s was relatively better. 60% infill sample was the best for the purpose of avoiding surface shrinkage and deformation of low infill samples and surface puffing of high infill samples. Practical applications In this study, fresh vegetables were used for printing and MW sterilization was combined into 3D printing, so as to ensure the microbial safety of 3D printed products and provide technical basis for the sterilization treatment of meat, seafood, and other printed foods susceptible to microbial contamination.