Release behavior of quercetin from chitosan-fish gelatin edible films influenced by electron beam irradiation

Highlights

• Irradiation was applied to edible chitosan-gelatin films.

• Irradiation generated reversible interactions between quercetin and polymer matrix.

• Irradiation delayed the release and increased the quercetin retention.

• Irradiation did not modify the rate of diffusion.

Abstract

This work dealt with the study of the release kinetics of quercetin incorporated into chitosan-gelatin edible films after electron beam irradiation. The aim was to determine the influence of irradiation dose (at 40 and 60 kGy) on the retention of quercetin in the films, their release in a hydroalcoholic medium (30% ethanol v/v) at 25 °C. Irradiation induced a reduction of the release rate for quercetin, revealing that cross-linking probably occurred during irradiation. Indeed, the content (%) of quercetin remaining in the film after the release increased from 23.4 ± 5.7% for non-irradiated sample to 33.6 ± 2.1% after a 60 kGy irradiation dose. But the effective diffusion coefficient of quercetin was not significantly modified by the irradiation process. However, it was noticed a significant increase of the lag-time (time required before the release starts) by ten times. Thus, the irradiation influenced the retention by creating new interactions or linkages between biopolymers and the quercetin, which finally led to an entrapment of a significant amount of the antioxidant. As expected, the electron beam irradiation allowed modulating the retention and then the release of the antioxidant encapsulated in the chitosan-gelatin matrices.

Introduction

Edible films and coatings offer the opportunity to effectively control mass transfer among different components within a food system or between the food and its surrounding environment (Debeaufort et al., 2002, Hernandez-Izquierdo and Krochta, 2008). Moreover, a modern trend for developing active edible films and coatings is to combine different biological polymeric materials and to incorporate various functional ingredients, such as nutritional supplements, antimicrobial or antioxidant agents (Cheng, Wang, & Weng, 2015). The most frequently used materials for edible films and coatings are polysaccharides (such as starch, cellulose derivatives, alginate, pectin and chitosan), proteins (such as gelatin, zein, gluten, milk casein, whey and soy proteins) and lipophilic materials (such as glycerides, beeswax and shellac). These materials can be used either individually or in combination to produce films and coatings (Nesterenko, Alric, Silvestre, & Durrieu, 2013). Active packaging can be achieved when functional ingredients are incorporated.

Chitosan is a natural polymer obtained by the deacetylation of chitin, which is a fish industry by-product. It is among the most investigated polysaccharides for active edible films and coatings development due to its inherent antimicrobial, antifungal properties and good film forming ability (Fernández-Pan, Maté, Gardrat, & Coma, 2015). Gelatin is another widely used bio-based material obtained by the controlled hydrolysis of the insoluble fibrous collagen present in the bones and skin generated by fish processing wastes. Its excellent film forming ability is well-known (Hoque, Benjakul, & Prodpran, 2010). Gelatin and chitosan based films used for coating or packaging could maintain the quality of foods during storage, due to their good barrier to oxygen, light and prevention of dehydration and lipid oxidation (Jongjareonrak et al., 2006, Park and Zhao, 2004). In order to improve the food-protective capacity of chitosan and/or gelatin films, various active substances including synthetic antimicrobial and antioxidant agents or natural plant extracts have been added into the film for increasing the food shelf life (Wu et al., 2015). In acidic environment (pH < pKa) the amino groups of chitosan are protonated and their positive charges can interact with polyanions such as gelatin, at a pH lower than its isoelectric point, forming a polyelectrolyte complex. Due to these characteristics, chitosan and gelatin have been widely used for the production of edible films (Benbettaïeb, Karbowiak, Brachais, & Debeaufort, 2015a).

The incorporation of antioxidants in these biodegradable edible polymers is an interesting alternative to food preservation, since oxidation is one of the major problems affecting food quality as well as biopolymer film ageing (Martins, Cerqueira, & Vicente, 2012). The use of natural, non-toxic antioxidants such as ferulic acid or α-tocopherol is sought in order to be consistent with the consumer health (Benbettaïeb et al., 2015, Fabra et al., 2011). Very few studies have established the effects of polymer structure, in particular chitosan-gelatin films, on the retention and release properties of the antioxidant compounds (Papadokostaki, Amarantos, & Petropoulos, 1998). Besides, irradiation have been shown as a promising technique to induce cross-linking between polymers and to improve the physical and functional properties of edible coatings (Benbettaïeb et al., 2015b, Vachon et al., 2000). However, the effects of irradiation treatment on the release mechanism of active compounds from edible films are not well-known. Lacroix et al. (2002) showed that gamma-irradiation was efficient enough for inducing cross-links in calcium caseinate edible films and could thus be envisaged for the immobilization of enzymes or active compounds. Gamma irradiation of caseinate also contributed to control the release. However, these works neither explained the mechanism involved in the release rate delay nor the impact of irradiation on the diffusivity of active molecules into the simulant media. The objectives of this study were to investigate the effects of electron beam irradiation on the release behaviour of quercetin in hydroethanolic medium.