Influence of physical and chemical caracteristics of plasticizers in the manufacturing and on the structural behavior and hygroscopic of films of calcium alginate

Author(s)

Audirene Amorim Santana

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2010-02-26

Examining board members

Theo Guenter Kieckbusch; Carlos Raimundo Ferreira Grosso; Fernanda Paula Collares Queiroz

• Advisor: Theo Guenter Kieckbusch

Abstract

Responsible consumers are looking for processed food with higher nutritional value and extended shelf live, without disregarding the damaging cumulative effects of sub products discharge on the environment. Biodegradable films are part of this concept. They are produced from natural polymers, mainly saccharides and proteins, with potential applications in the pharmaceutical or food industries. Alginates are polysaccharides with large applications in biotechnology due to their ability to form strong and insoluble gels when crosslinked with Ca++. This reaction is fast and localized, preventing subsequent casting of the gel in the form of a film. In order to produce smooth and insoluble films, a weekly reticulated film already containing the plasticizer is confectioned first, and then exposed to a calcium solution and the reticulation is complemented by diffusion. During the contact period, however, the solution is prone to leach the plasticizer, and the resulting film will not present the required flexibility. The objective of this study was to select calcium alginate film forming formulations structured with plasticizers that show low solubilization/leaching susceptibilities in aqueous environments. The study examined initially the more conventional plasticizers (glycerol, mannitol, xylitol, sorbitol maltitiol, polyethylene glycol (PEG 300)). Consideration was then given to the simpler sugars (like fructose, lactose and sucrose), short chain fatty acids (hexanoico acid), non ionic surfactant (Tween 20) and non conventional solutes like ethanolamine, sodium lactate, triacetin and tributyl citrate. The final selection of adequate plasticizers was based on visual aspect, moisture content, solubility in water, water vapor permeability, degree of swelling in water, tensile strength and elongation of the films. The plasticizers that produced films with an adequate compromise within these attributes were glycerol, xylitol, mannitol and tributyl citrate. Films containing these plasticizers were submitted to microscopic observations of their structure (MEV), and their sorption isotherms, color and transparency, and glass transition temperature were determined. The results confirmed the excellent and powerful plasticizing effect of glycerol and a similar behavior of xylitol. Mannitol and tributyl citrate form films with lower hygroscopicity, but are less flexible. A compromise between high mechanical resistance, attractive appearance and low solubility in water can be obtained with a mixture of tributyl citrate and glycerol (AU)