Other Additives
Another diverse class of polysaccharides that are widely employed in the food industry are the hydrocolloids which form a group of long‐chain hydrophilic polymers (Li and Nie 2016). The presence of one or more hydroxyl groups rendered them water‐loving thereby forming a colloidal suspension when added into the food mixture. Hydrocolloids are derived either from plants/ seaweeds (xanthan gum, carrageenan, gum arabic, locust bean gum, guar gum, gellan gum, glucomannan, and pectin) or animal sources (gelatin, chitin, and chitosan) (Mehta et al. 2019) (Table 3.1). They exhibit a varied range of functional property as they can act as thickeners, stabilizers, foaming agents, emulsifiers, and gelling agents that help in tailoring the rheology of food systems. Concerning 3D printing, hydrocolloids are commonly used as food additives for making the material supply attain a conducive consistency suitable for 3D printing by altering its flow and viscosity. Further many studies were reported on food hydrocolloids as reference material for 3D food printing. Kim et al. (2018) conducted a study on a comparative assessment of various hydrocolloids such as guar gum, gellan gum, xanthan gum, locust bean gum, hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and gelatin for their applicability in food printing. The study was performed for framing a classification system based on printability assessment. Among all the hydrocolloids considered for the study, MC was found to be capable of simulating the handling properties and deformation behaviour of foods and possess good mechanical stability which was comparable to most of the food systems with diverse viscosity. Thus, a classification system was made based on dimensional and storage stability as grade A to D with grade A more suitable for 3D printing that requires less extrudable force as with cheese. On the other hand, the latter category of grade D includes materials like cookie dough which requires more force to extrude out of the printing nozzle (Kim et al. 2018).
Table 3.1 Classification of food hydrocolloids.
| Origin | Examples of hydrocolloids |
|---|---|
| Plant | Gum arabic, basil seed gum, gum karaya, konjac, locust bean gum, flaxseed gum, guar gum, and starches |
| Animal | Chitin, chitosan, and gelatin |
| Seaweeds | Agar, alginate, xylan, carrageenan, and ulvan |
| Microbial | Gellan gum, tara gun, xanthan gum, dextran, curdlan, and pullulan |
| Synthetic | Carboxymethyl cellulose, methylcellulose, hydroxypropyl methylcellulose, and other cellulose derivatives |
In another study, Vancauwenberghe et al. (2017) developed a pectin‐based food stimulant for 3D printing applications. The study correlates the effect of the degree of methoxylation of pectin with a concentration of Ca2+ ions as a cross‐linking agent that aids in printability. Results showed that the formulation of food ink was greatly influenced by the density of the polymeric network and its degree of cross‐linking with Ca2+ ions. The addition of sugar to the food stimulant affects the viscoelastic behaviour and hence could be positively correlated with printability. As the incorporation of sugar dehydrates the polymeric matrix thereby enhancing the gelation mechanism with the formation of hydrogen bonds that would result in higher young’s modulus with firmer pectin‐based gel (Vancauwenberghe et al. 2017). Further, the study demonstrates the production of porous aerated 3D structure with the use of bovine serum albumin (BSA) and remains to be a base for future works for the development of food stimulants with added flavours and textures for food 3D printing.
Basic mechanisms responsible for the gelation of hydrogels are ionotropic cross‐linking, chemical cross‐linking and coacervate formation. Among which ionotropic cross‐linking is the most commonly employed technique for hydrogel formation. The physiochemical characteristics of the hydrocolloids were greatly affected by several factors such as temperature, melting and solidification, ionic strength, gelation behaviour, and cross‐linking (Godoi et al. 2016). Hydrocolloids in the form of hydrogels are gaining attention in recent days as it possesses the centric value as that of dietary fibres. A study was reported on the satiety effects of hydrocolloids, as it could result in slowing down of enzymatic actions or could delay gastric emptying (Li and Nie 2016). As an important application, hydrocolloids are utilized for increasing the fibre content of the diet. Along with other major food constituents, hydrocolloids play a significant role in modifying the sensorial aspects of food and hence found to possess a key role in regulating the dietary aspects of food for providing a healthy 3D printed customized diet.
3.5 Classification of Foods Based on Their Printability
The nature of the material supply is an essential criterion in determining the final quality of the 3D printed edible constructs. Printability refers to the inherent ability of the material to withstand its own weight upon deposition over the printing platform (Kim et al. 2018). A material to possess good printability must have enough dimensional and mechanical stability to retain its shape after printing. Based on the nature and printability of the material supply, the ingredients for 3D printing can be categorized as natively printable, non‐printable traditional materials and alternative ingredients (Sun et al. 2018). The first class of natively printable materials include chocolates, cheese, cake frostings, hydrogels, etc., which are innately printable on their own without the addition of additives. This class of material supply requires less processing with ease of handling during printing. A second class of traditional materials includes staple cereals, fruits and vegetables, eggs and flesh foods that are common in our day‐to‐day life but are non‐printable on its own. This kind of material requires certain pre‐processing such as the addition of food additives or mixing a proportionate amount of natively printable materials for converting them into a printable form. The most common application is the use of food hydrocolloids as additives for making non‐printable materials printable. The third category includes alternate ingredients like insects, algae, fungi, and lupin seeds which are quite a good source of nutrients but are uncommon foods (Sun et al. 2015). They are widely used as a novel approach for the development of sustainable food to tackle the ever‐growing food demand. A detailed description of the classification of materials based on printability was discussed in the subsequent chapters.
3.6 Conclusion
Food 3D printing implies a novel way of customizing foods based on individual preferences. The final acceptability of any food recipe was based on the ingredient’s choice that makes a wholesome food. The role of various food constituents in terms of printing was well discussed in the present chapter. The chemical and structural constituents responsible for the printability of macronutrients provides insights for the development of 3D printed functional foods based on age group and dietary pattern. The study of the individual food constituent and its response towards printability helps to combine the ingredients that pave for the exploration of new dishes by utilizing the synergistic benefits of each constituent. Thus, apart from the nutritional benefits, each of the macro elements of food has its role in imparting printability and acts as a key in modifying the sensorial attributes of food.
References
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2 Anukiruthika, T., Moses, J.A., and Anandharamakrishnan, C. (2020). 3D printing of egg yolk and white with rice flour blends. Journal of Food Engineering 265: 109691. https://doi.org/10.1016/j.jfoodeng.2019.109691.
3 Chen,
