Quality assessment of 3D-printed cereal-based products

The process of three-dimensional (3D) printing is of greatest interest to food science and engineering community because it offers numerous opportunities for innovative food design, new product formulations and personalized nutrition. Of particular interest are food inks based on cereal flours or starches, whose unique rheological properties make them suitable for 3D printing, typically with an extrusion-based printer. While the factors that influence the success of food printing are well addressed, the terminology and methods used to evaluate the process and product features are miscellaneous. Therefore, this research work aims at providing an overview of the most commonly used parameters and methods for evaluation of the extrusion-based 3D printing process and the resulting cereal-based foods. Physical and sensory methods that are successfully used for the quality assessment of the ink and the printed raw objects, as well as the post-processed products are here reviewed and outlined. The properties of inks, usually determined with dynamic rheological tests, are linked to various aspects of printing quality whereas the physical properties of printed raw forms are usually evaluated by image analysis combined with mathematical calculations. Microscopy analysis is undertaken to study the microstructure of both the raw objects and the end-products, while texture analysis and sensory evaluation of final product are performed both by a panel and instrumentally. We provide details of the tests, but also emphasize the need to standardize the procedures and terminology in order to avoid misunderstandings and multiple variations of similar methods. This review provides a basis for further development and standardization of the methodology for quality assessment of 3D-printed cereal-based foods.