3D printing using layer-by-layer deposition technology also called additive manufacturing are increasingly studied for their potential in terms of food personalization. 3D extrusion printing offers the possibility to design shape, texture, taste, and nutritional needs that meet consumers preferences and the needs of specific populations (e.g., people with dysphagia, athletes, people with allergies or following a diet, etc.). Different types of edible inks have been studied for 3D food printing such as chocolate (Mantihal, Prakash, & Bhandari, 2019), gels system (Chen, Zhang, & Phuhongsung, 2021; Wang, Zhang, Bhandari, & Yang, 2018; Yang, Zhang, Bhandari, & Liu, 2018), mashed potato (Liu, Zhang, Bhandari, & Yang, 2018), ground meat (Dick, Bhandari, Dong, & Prakash, 2020; Dick, Bhandari, & Prakash, 2019). Other studies have focused on cereal-based food like cookie dough (Pulatsu, Su, Lin, & Lin, 2020) or snack (Derossi, Caporizzi, Oral, & Severini, 2020; Derossi, Caporizzi, Paolillo, & Severini, 2020; Uribe-Wandurraga et al., 2020).

Wheat flour dough shown a strong interest in 3D food printing because of their structuring properties of starch and proteins when using a thermomechanical treatment. A two-step thermomechanical treatment firstly allows the hydration of the constituents of the flour during mixing, and then the gelatinization of the starch as well as the denaturation of the proteins occurs during the mixing step combined with heating (Masbernat et al., 2021). These changes make it possible to increase the viscosity of the dough and thus make it printable. In the field of cereal products, few studies have focused on this type of treatment, but the results of Champenois, Rao, and Walker (1998) and Masbernat et al. (2021) demonstrated that hydrothermal transformations of starch and gluten proteins in hydrated doughs made from wheat flour are impacted by water/flour ratio and process parameters (duration, intensity and temperature). For example, if the amount of water available for starch gelatinization is not sufficient, the dough obtained after the treatment will contain non-gelatinized or partially gelatinized starch granules that are more rigid (higher G') than gelatinized starch and could lead to less dough sticky particles. These properties of rigidity and stickiness could thus affect the printing quality of the doughs (Masbernat, 2021).

More complex recipes with the addition of sugar and oil, dairy ingredients, fruits or vegetables puree to the wheat flour dough have also been printed and validated (Guénard-Lampron, Masson, Leichtnam, & Blumenthal, 2021; Masbernat, 2021). However, to diversify the tastes and textures and improve the nutritional intake of these printable products made from flour, it is essential to explore matrices based on other cereals, legumes, or nuts flours for example. Recent publications report on new food inks integrating different flours with interesting nutritional properties (e.g., gluten-free, richer in fiber or protein). Gluten-free snack bite (lupine or chickpea flour) (Agarwal et al., 2022), high fiber cookie (oat, rye, rice, and carob flour) (Pavičić, Grgić, Ivanov, Novotni, & Herceg, 2021), protein and dietary fiber-rich snack (wholegrain rye flour) (Lille, Kortekangas, Heiniö, & Sozer, 2020), gluten-free snack (wholegrain buckwheat, proso millet, white corn, sweet potato or flax seed flour) (Radoš et al., 2022) are some examples. However, the integration of these flours in food inks can affect printing quality and stability of the printed product. For example, Agarwal et al. (2022) and Radoš et al. (2022) observed that the print quality of the gluten-free snacks was strongly affected by the particle size of flour (e.g. coarse filaments with lupine flour compared to smoother filaments with chickpea flour). It therefore seems essential to study a formulation and process strategy that considers the printability of edible ink prior to the development of these new 3D printed foods.

Godoi, Prakash, and Bhandari (2016) define the printability of a food material by its ability to maintain its dimensional stability and support its own height. Nijdam, LeCorre-Bordes, Delvart, and Schon (2021) summarized the quality of a print according to three main factors: printer capability (ex.: force required to extrude food ink and accuracy of the displacement), filament quality (e.g.: rheological and microstructural properties of the food ink) and dimensional stability (during and after printing). In addition, several printing (e.g. printing speed, nozzle diameter, layer height, filling rate, fill pattern) and post-processing parameters (e.g. cooking methods, temperature, and time) affect the quality and stability of the 3D-printed products (Guénard-Lampron et al., 2021; Severini, Azzollini, Albenzio, & Derossi, 2018; Severini, Derossi, & Azzollini, 2016).

In this study, we developed a 3-step approach to answer our main objective, which was to know how to ensure good printing quality of dough made from different flours with interesting nutritional qualities by using a thermomechanical treatment similar to that developed by Masbernat et al. (2021) for wheat flour dough. The first step of this study was to conduct a bibliographic screening of flours and to select five flours according to three criteria (nutritional value, distance to major product region and price). The second step was to select two flours from the previous selection according to their printability potential by using an experimental screening. The last step was to optimize and validate the print quality of the two flours that have demonstrated good printability potential during the previous step. The final selection was limited to two flours due to the time required to conduct the tests and to validate the potential for optimization by the process before applying this method to several flours. Finally, the aim of our study was to propose a predictive model for each flour to obtain the specific thermomechanical parameters to use for a good printing quality. The next sections are organized accordingly to our 3-step approach.