Citrus or apple inks for the 3D printing - the influence of the low methylated pectin structure and the standardized sugar type on their printability

In the article the possible using of low methylated amidated pectin for hydrogel bioinks preparation was investigated. The used pectins were obtained from different fruits and were characterized by their varying molecular weight characteristics, monosaccharide composition, and degree of esterification, degree of amidation and type of sugar additive (sucrose or glucose). The focus was on analysing the influence of the polymer structure and added sugar type on the 3D printability and thermal properties of the developed formulations. The studies had shown that the influence of the type and amount of sugar seems to be more crucial. It was observed that in the presence of sucrose, pectin crosslinking occurs not only through ionic and hydrogen interactions sugar-pectin-metal ion, but also through chemical crosslinking occurring as a result of the Millard reaction between amidated pectin and fructose formed as a result of sucrose hydrolysis. This phenomenon is not observed in the presence of glucose in the system, where the polymer forms reversible gels. The printability tests indicates that in order to obtain inks based on amidated pectin with a low degree of esterification, it is beneficial to use biopolymer standardized with glucose and optimize its amount in the system.