Liquid and Pressure-Sensitive Adhesives Based on Cassava Starch and Gelatin Capsule Residue: Green Alternatives for the Packaging Industry

MONROY, Y.; RIVERO, S.; GARCIA, M. A.

Foods

Multidisciplinary Digital Publishing Institute (MDPI)

Lugar: Berna; Año: 2023 vol. 12

In recent years, there have been increasing efforts in the adhesives industry to improve the sustainability of processes and products. Natural polymer-based adhesives are “green” alternatives, necessary to reduce the problems impacted by synthetic adhesives. The packaging industry is the main recipient of this type of input and is still in need of challenges within the framework of the Circular Economy. The development of eco-compatible and water-based adhesives that allow easy and rapid washing with the consequent reuse of containers is seen as an considered alternative with potential functionality to minimize environmental impacts, also contributing to the sustainability of processes. In this way, starch and gelatin have extraordinary potential for the synthesis of various formulations due to the versatility of functional groups. One interesting source of protein to develop biodegradable materials is the residue generated by the industrialization of gelatin capsules, which are used to deliver bio-active compounds in the nutraceutical sector. Therefore, the valorization of industrial by-products to produce bioadhesives materials may contribute to scaling down the amount of residue disposal reducing the use of non‐biodegradable synthetic polymers. Starch has advantages such as being biodegradable, low cost, renewable, and contains hydroxyl groups with strong intra- and intermolecular hydrogen bonding. Citric acid (CA) is a natural acid and it has been already demonstrated to be suitable for the cross-linking and hydrolyzing of both gelatin and starch. In this sense, the present work deals with the use of gelatin capsule residues as a promising material to produce biobased adhesives in combination with cassava starch and characterize their mechanical, physicochemical, and microstructural properties.Depending on the concentration of citric acid, formulations adjusted to different applications can be obtained. The inclusion of citric acid allows not only to improve the applicability of the system as it modifies the flowability of the adhesives as evidenced by the observed changes in the viscosity (from 158.3 to 90.3 for formulations with 20 and 80% CA, respectively) but also provides increased adhesive bond strength. Structural modifications induced by CA in adhesive formulations were highlighted by ATR-FTIR analysis.