# Texture Modification of 3D-Printed Multitol Candy by Changing Internal Design
## 1 Introduction  
3D printing technology is widely used in the production of various prototypes and special-purpose parts because it has the advantage of being able to manufacture parts with complex structures into three-dimensional shapes simply by designing them [1, 2, 3]. Accordingly, application areas of 3D printing technology are gradually expanding, and its importance is increasing in various industries such as mechanics, architecture, electronics, medical care, and food [4, 5, 6, 7]. As such, as the scope of applications of 3D printing technology is gradually increasing; attempts are actively being made to manufacture structures that can actually be used based on various materials beyond simple shape production. These attempts have had a significant impact on the food industry in recent years. Therefore, food 3D printing that actually creates edible food is being studied in various ways. 3D printing in the food industry is not only used for colorful shapes and decorations but also has a very high functional value because it can provide various textures and appropriate nutrients to the underprivileged in society who have restrictions on their food intake [8, 9]. Among the various 3D printing types, the methods mainly used for food printing can be divided into two types: powder-based methods and high-viscosity-gel-based extrusion methods. Given that many types of food materials such as vegetables and fruits, as well as sugar and flour, can easily be produced in powder form, there may be a method by which to form a shape by applying powders of these ingredients individually and thinly and then locally melting the powders with a high-power laseror a high-temperature heat source [10]. Alternatively, a food printer that can realize full-color 3D structures using various food powders and edible liquid adhesives was also introduced [11]. However, these powder-based printers have limitations in terms of materials and equipment. Accordingly, numerous attempts to realize food printing using an easy-to-use extrusion-based method have been made. Extrusion-based food printing requires a simple equipment structure and has almost no material restrictions. Therefore, printing examples for various foods such as chocolate, burritos, pasta, cheese, and pizza have been introduced [12; 13; 14; 15]. In addition, recent studies have attempted to observe changes in strength and texture levels by changing the internal design rather than merely making simple shapes. With regard to the existing 3D printing methods using metals or polymers, many studies have concentrated on making various mechanical strength changes through internal structural designs considering the material properties [16; 17; 18]. These designs for additive manufacturing (DfAM) studies are emerging as very important in the 3D printing field. Recently, there have been various attempts to study changes in mechanical strength and texture outcomes according to changes in internal design in food printing as well. First, one study investigated various textural and strength changes using mashed potatoes by changing the internal design [19]. By modifying the infill percentage (10%, 40%, 70%, and 100%) with different infill patterns (rectilinear, honeycomb, and Hilbert curve) and variations in the shell perimeter (3, 5, and 7 shells), printed foods of the same size and material could be manufactured, but with different textures. As a result, various firmness values from 25.15 g to 144.81 g were obtained, depending on the manufactured structure. Another study assessed textural changes using a slightly harder material: chocolate [20]. These researchers measured the breaking force in each case by varying the type of chocolate, the infill percentage, and the infill pattern. As a result, it was shown that it is possible to change the texture of chocolate using various break forces ranging from 1.9 N to 114 N, depending on the material and shape.