Development of 3D food printer and use of mushrooms in 3D food printer within the scope of new plant-based food production

Abstract

3D printing which is also referred as additive manufacturing is the process of generating three-dimensional objects from a CAD (computer-aided design) model. 3D printing technology is gaining popularity because of its diverse production capabilities, cost-effectiveness, and efficiency. As an emerging technology in the food industry, 3D food printing has great potential in meeting the individual needs of consumers for shapes and nutrition. Production of functional foods for specific target populations and novel dietary customization are main interest areas of food sector to meet customer preferences. To achieve these objectives and to offer a solution for the problems, printers capable of extruding food materials are required. Although various 3D food printing techniques are used in the food industry, extrusion-based technologies are currently the most widely used. Over the years, three-dimensional printing has developed into a user-friendly and cost-effective craft. But it is still a very expensive process to implement these techniques in the field of food and biotechnological research and development in laboratories. Since popularity of 3D printing is increasing and implementation of new 3D food printing mechanism is an expensive option, we observed an opportunity of developing a 3D printer which is capable of printing foods in an affordable way. Besides, food sector searches for sustainable and environmentally feasible high-nutritional foods, including the investigation of alternative protein sources, this lead us to study on plant-based food alternatives. Furthermore there are some chronic problems such as risk of malnutrition, concerning some of elderly people and dysphagia patients who suffers from mastication and swallowing food and that has limited choices of food sources, we aimed to research for a possible solution of this problem by using 3D-printing technology. The first aim of this study was to evaluate the opportunity of filling an open research area in 3D printing in food science and to show an alternative option to the expensive commercial 3D food printers by designing, producing and implementing a new 3D food printing capable mechanism in an affordable way. Taking this objective into consideration, an attachment mechanism was sketched in a CAD program and printed with regular 3D printer. This attachment assembled with some common small hardwares and fixated to a conventional 3D printer. Then printing capability and validation studies were conducted. We studied on two other different designs that are available in common 3D printing forums and adapted them to the desktop printer before the current mechanism. In these preliminary experiments, misleading movement was realized which was resulted in misplaced and uneven layers of desired 3D objects. After redesigning and reconfiguration with the results of validation process, a laboratory type 3D printer that is capable of printing shaped foods was successfully constructed. After that, possible food printing capabilities of this 3D food printer was observed by preparing a functional food for elderly and dysphagia patients. For this purpose dryed mushrooms which contains high antioxidants and rich in protein was mixed with a plant-based edible food ink that comprised of soy protein and xanthan gum. Fungis, Pleurotus ostreatus (oyster mushroom) and Agaricus bisporus (cultivated brown mushroom) that have 19.83% and 33.42% amount of protein in dry base and antioxidant activity of 7.60 mg/g and 11.77 mg/g and phenolic content of 6.00 mg/g and 4.74 mg/g dry fungi respectively, was used. Printing of edible ink was conducted with 1.6 mm nozzle size, speed of 20 mm/s and 1.5 mm layer height with 4 layers. A layered flower shape, that has size of 47 mm width and height, was printed to assess visual acceptance of paste-like foods. Results were satisfactory for the beginning studies, the research showed that visual acceptance of paste-like foods can be increased by new technology 3D food printers and they can be possible solution for malnutrition of patients with the functional foods. On the next stage, 3D food printer improved for it is software and printing settings and a cooling apparatus attached. So that, an exchangeable syringe-pump mechanism (SPM) developed on the basis of first study to demonstrate transformation of conventional 3D printer from polymer to food extrusion. The proposed mechanism, SPM, has capability of printing a variety of materials, including miscellaneous foods, pastes, hydrogels and even biopolymers. The complete mechanism relies mostly on 3D printed parts and costs approximately 72$. The main functional component of apparatus consists of 23 parts in which 16 parts are 3D printable elements and remaining parts are easily found items that include one trapezoidal lead screw and two brass nuts, luer-lock syringe and three bearings. Therefore, it allows users to obtain a 3D food printer inexpensively and does not require large amounts of technical labor. The SPM uses 60 ml volume luer-lock syringe and with its modular design, it can be adapted to smaller or bigger volumes only by modifying some parts of attachment. Moreover it uses blunt tip needles for greater versatility and user-friendliness thus it can accommodate a variety of standard needle sizes with dimensional variations ranging from 0.1 to 1.6 mm. With its cooling mechanism extension, SPM gains unique attribute among its counterparts. There are many different types of food or bioprinters on the literature and they generally operate at low speeds. Since the mechanism we proposed is mounted on a linear rail guide and its center of gravity is designed to be on the rail, it can operate at relatively higher speeds (more than 50 mm/s) than other printers. Validation and characterization of proposed mechanism were evaluated by printing of various shapes with different needle sizes and variable layers. Within this regard, printing of some oleogels, mushroom-fortified food paste and a plant-based meat analogue formulation were investigated. To validate the working of SPM and observe possible printing capabilities of different nozzles, an oleogel mixture prepared to assess 0.6 mm diameter nozzle, a mushroom fortified semi-solid food mixture for dysphagia patients prepared to assess 1.2 mm nozzle and a meat analogue prepared to assess 1.6 mm nozzle. A flower structure and hollow circles were drawn and exported as a "stl" file to obtain "gcode" for printer software. Resulting prints were analyzed with image processing programme, ImageJ, in order to accurately measure the perimeters and the gaps and each formulation was printed at least in triplicate and shape fidelity calculated. Hollow cylinders and flower shapes were successfully 3D-printed with three different food inks. Shape fidelity values of diameters ranged between 99.3-100.7 %, heights ranged between 100.2-100.8% and accuracy of gap size ranged between 99.0-102.3 %. Flower shape were 3D-printed without retraction, on the other hand during printing of cylinders different retraction speeds were used. A filamentous structure could be observed between the skirt and the print body when no retraction was used however with relatively lower retraction speed oleogel sample accumulated and represented a ridge on the retraction point. Results showed that at high layer numbers, deviation of height accuracy increased, this could be related with rheological properties of food materials. However deviation of all dimensions were not higher than 3% which demonstrates that the performance of the SPM was satisfactory for the food materials. As the food sector searches for sustainable and environmentally feasible high-nutritional foods, including the investigation of alternative protein sources, this lead us to study on plant-based food alternatives. In this context, another objective of this study was to investigate a printable and functional vegan meat analogue. Meat analogue formulations consisting of pea and soy protein as main protein sources was prepared as a food ink (C) and then fortified with three different mushroom cultivars (reishi, Ganoderma lucidum, GL; saffron milk-cap, Lactarius deliciosus, LD; and oyster, Pleurotus ostreatus, PO). The 3D printing performance of four formulations were evaluated by a factorial design in terms of nozzle height, printing speed and flow compensation. Levels of factors were 0-3.3 mm, 20-80 mm/s and 90-100% respectively. Based on the findings, a lower nozzle height (0 mm), a medium printing speed (50 mm/s), and a regular flow compensation rate (100%) were chosen for the further analysis. A 60×70 mm and 6 layered (approximately 10 mm) shape, that contains, hole, empty border and narrower and wider areas, were printed with meat analogue formulations. Target design were succesfully printed with smooth layers and in accurate sizes for all formulations. Inks were characterized by analyzing rheological properties, microstructure, color characteristics, texture profile, cooking loss, amino acid content, and sensory evaluation. Results showed that the nozzle height and printing speed were found to be most effective on accuracy of prints and smoothness of layers. All inks (C, GL, LD and PO) represented shear-thinning and gel-like viscoelastic behavior (G' > G'') with predominant elasticity (tan δ<1). Therefore they were suited for 3D printing and possessed supporting the following layers for additive manufacturing as well as meeting the criteria for a stable structure. GL was looking linty while there was no perceived defects on other formulations however it has more stable layers than others. LD and PO inks brought the advantage of recycling as a result of their re-printability whereas GL could not. Moreover, mushroom fortification reduced hardness, stiffness, springiness, and chewiness properties of the meat analogues whereas it increased the juiciness with reasonable overall acceptance besides enhancing the nutritional value and improving release of umami amino acids. Overall, the finding of the study demonstrated that mushrooms could be a functional and nutritious candidate for 3D printable plant-based meat analogues. 3D printing is still in its early stages and has a widespread application areas. In this study we developed a cheaper option of food printing 3D device for the scientific researches. We intended to add an easily adaptable and simple to operate syringe-pump system to the literature, open a gate to cost effective research and demonstrate transformation of 3D printer from polymer to food extrusion. As 3D printing technology advances and our understanding of food printability improves, printers with two, three or more printing heads (cartridges) could be manufactured in a cost-effective way for the scientific laboratories. Different protein sources could be combined to obtain functional and full nutritional foods in desired shape with this new process technology.