How to favor crosslinking in hydrocolloid-based edible films
N Benbettaieb1,2, T Karbowiak2 and F Debeaufort2
1 National Center for Nuclear Sciences and Technologies, Sidi Thabet Technopark, 2020, Ariana, Tunisia
2 UMR A 02.102 PAM, Food Physico-Chemistry and Processing Lab, Université de Bourgogne/AgroSup Dijon, 1 esplanade Erasme, 21000 Dijon, France
Petroleum based synthetic polymers are mainly used for packaging purpose. This widespread use is due to their excellent mechanical and thermal properties as well as their cost effectiveness1. However, being non-biodegradable, these are inappropriate to cope with the steps of development of sustainable materials. Hence, during the last few decades, versatile efforts are in progress to develop biodegradable alternative packaging materials that, simultaneously, will be cheap, possess good mechanical and thermal properties, and provide a good resistance to moisture. Such attempted films are usually derived from natural renewable polymers or food by-products. Chitosan is a suitable material for designing packaging structures such as films or coatings due to its excellent film-forming capacity as well as good gas barrier properties. Gelatin is also a relatively low cost biosourced polymer with excellent functional and filmogenic properties2. However, those polymers are highly sensitive to moisture and exhibit poor water barrier and mechanical properties3. This represents a major drawback and limited their application until the present time. Chitosan and gelatin chains possess reactive side groups which can be potentially be modified via chemical, physical or enzymatic crosslinking to enhance the water and gas barrier properties as well as the structural properties of the blend film. A promising alternative consists in crosslinking those two polymers by using high-energy ionizing radiation, such as electron beam, gamma, or X-ray. The present work aimed to study the effect of electron beam irradiation (20, 40 and 60 kGy) on physical, chemical and mechanical properties of chitosan-gelatin films prepared by casting method. Tensile Strength (TS) of gelatin film significantly increased with higher irradiation doses (improved by 30% after 60 kGy).However TS of chitosan and blend films were not significantly affected. Irradiation significantly decreased the elongation at break (%E) for chitosan and blend films. Moisture barrier for blend films, studied for a 30-84% RH gradient, is improved after irradiation. It was more pronounced at doses higher than 20 kGy. Oxygen permeability decreased only for a 60 kGy irradiation dose, both for chitosan and blend films. Contact angle with water also decreased for all films. Thermal stability, determined from TGA analysis, was improved after irradiation for gelatin and blend chitosan-gelatin films. It is in good agreement with mechanical and barrier properties. Such enhancement of mechanical, barrier and thermal properties of studied films after irradiation could be explained by intermolecular cross-linking occurring between the polymers within the film matrix.
References
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3 Ben Bettaïeb, N., Kurek, M., Bornaz, S. and Debeaufort F. (2014) Barrier, structural and mechanical properties of bovine gelatin/chitosan blend films related to biopolymer interactions. Journal of the Science of Food and Agriculture, 94, 2409-2419.