Characterization of chitosan-based films with vanillin as a natural cross-linking agent

PEREDA, M.; ANSORENA, R.; TOMADONI, B.

Mar del Plata

Simposio; SLAP 2018-XVI Simposio Latinoamericano de Polímeros junto con el XIV Congreso Iberoamericano de Polímeros; 2018

INTRODUCTIONWith the increasing concern on environmental issues, different authors have focused their attention on the development of natural innovative materials for food packaging applications, such as Chitosan (CH) films. CH has excellent film-forming nature, antimicrobial properties, biocompatibility and biodegradability; however, CH films do not have good mechanical characteristics. Therefore, some cross-linking agents such as glutaraldehyde, formaldehyde and glyoxal, should be added to improve its properties1. Nevertheless, these agents may be considered as health hazards, with some undesirable side effects. Thus, people want to replace them with natural non-toxic cross-linking agents, such as vanillin (V). Until now, few studies have been found were vanillin application for enhancement of chitosan film properties is reported. EXPERIMENTAL METHODSCH film-forming solutions were prepared according to Pereda et al.2: 2% (w/v) of chitosan were dissolved into 1% (v/v) acetic acid aqueous solution, and glycerol (45% w/w of CH) was added as plasticizer. Once the solution was homogeneous, vanillin (37.5% w/w of CH) was incorporated as a natural cross-linking agent and dissolved using a magnetic stirrer. The films were prepared by the casting technique in a convection oven at 57.5ºC. Film formulation (vanillin and glycerol content) and drying temperature was obtained in a previous study by response surface methodology. A control was used without vanillin. Color parameters (L*, a*, b*), total color difference (ΔE), opacity, mechanical properties (young modulus, YM; elongation at break, εb; and ultimate strength, σb), water vapour permeability (WVP) and total soluble matter (TSM) were evaluated according to Pereda et al.2. RESULTS AND DISCUSSIONProperties of the chitosan films with and without vanillin are shown in Table 1. The incorporation of vanillin into the chitosan films affected its color, with a decrease in L* parameter, and an increase in both a* and b* (red and yellow), leading to a significant increment in the opacity of the films and an important total color difference when compared to CH films. As it was expected, YM and the ultimate strength were improved significantly with the incorporation of Vanillin. At the same time, a decrease in the elongation at break was observed. Finally, WVP was slightly reduced with vanillin addition. These results are correlated with cross-linking reaction that occurs when the aldehyde group of the vanillin molecule reacts with chitosan amine group leading to a secondary aldimine, better known as a Schiff base.Contrary to what was expected, TSM was increased with vanillin addition.CONCLUSIONVanillin is a promising natural alternative to commercial cross-linking agents to improve mechanical and barrier properties in chitosan films. REFERENCES1. Tang X.Z. et al. Crit Rev Food Sci Nutr. 52(5), 426-442, 2012.2. Pereda M. et al. Carbohydr Polym. 101, 1018-1026, 2014.ACKNOWLEDGMENTSThis work was supported by CONICET, ANPCyT, UNMdP.