In recent years, the food industry has been undergoing major changes driven by new social and environmental demands. Nowadays, biodegradable packaging is perceived as the most feasible alternative for food packaging. Great efforts are being devoted to the development of new materials from agro-industrial wastes and byproducts that are opening new alternatives and trends in the biopolymer sector. The aim of this laboratory exercise is to provide a tool to motivate active learning of new technologies and trends in the chemistry of biopolymers. The presented guide introduces to undergraduate students to the basic concepts of polysaccharide-based biopolymers and the characterization of functional properties. This exercise is focused on barrier properties, specifically on water vapor permeability. Chitosan is used as an example of a biopolymeric matrix, and its synthesis and water vapor permeability measurement are described in detail. In addition, a guide for the 3D printing of a temperature-controlled permeability chamber is provided, which will allow the experiment to be carried out in less time as the equilibrium state of the system is not broken when the permeability cup is weighed. It is expected that this exercise and the complementary Supporting Information will be of great interest to biopolymer teaching and research laboratories.