Tensile and water vapour properties of calcium crosslinked alginate-cashew tree gum films

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International Journal of Food Science & Technology

Tensile and Water Vapour Properties of Calcium Crosslinked Alginate-Cashew Tree Gum Films

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International Journal of Food Science and Technology IJFST-2011-08013.R3 Original Manuscript Edible Films, Biodegradable Packaging, Polysaccharides, Gums

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Tensile and Water Vapour Properties of Calcium Crosslinked Alginate-Cashew Tree Gum Films

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Alginate/Cashew TreeGum Films Henriette M.C. Azeredo*, Ulysses S. Magalhães, Samira A. Oliveira, Hálisson L. Ribeiro, Edy S. Brito, Márcia R. De Moura Embrapa Tropical Agroindustry *Corresponding author. Embrapa Tropical Agroindustry, R. Dra. Sara Mesquita, 2270, Fortaleza, CE, Brazil, CEP 60511-110, ette@cnpat.embrapa.br.

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Abstract

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In this study, sodium alginate films were blended with cashew tree gum (CTG) andimmersed in CaCl2 solution. The influence of CTG concentration and immersion time in CaCl2 on tensile properties, water vapour permeability and water solubility of alginate films was evaluated. Glycerol-plasticized alginate/CTG films were cast on glass plates, which were then immersed in a 2% CaCl2 solution in order to crosslink alginate. CTG concentration in the film solution and immersion time inCaCl2 bath were varied according to a central composite design. Tensile strength, Young´s modulus, water solubility and water vapour barrier of the films were favoured by higher immersion times in CaCl2 and lower CTG concentrations. The negative CTG effects on such properties have been attributed to competition between the polysaccharides for interactions with calcium ions, reducing crosslinkingdensity and loosening the film structure. On the other hand, this loosening effect resulted in a higher film flexibility at higher CTG concentrations.

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Keywords: biopolymer films; biodegradable packaging; polysaccharides; gums.

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1. Introduction

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Concerns over packaging waste have motivated the development of biodegradable and/or edible packaging films, based on renewable biopolymers such as polysaccharides andproteins (Krochta and Mulder-Johnston, 1997; Debeaufort et al., 1998). Edible films and coatings are expected to function similarly to conventional packaging, acting as barriers against water vapour and gases, and improving mechanical-handling properties of foods. Edible packaging is not meant to entirely replace conventional packaging, but to enhance the efficiency of food protection, reducingpackaging requirements and waste. Moreover, edible films can act as barriers between food components, where traditional packaging is unable to function (Krochta & De Mulder-Johnston, 1997). Sodium alginate is an anionic carbohydrate extracted from various species of brown seaweeds (Phaeophyceae). It is a family of unbranched binary copolymers of (1-4)linked β-D-mannuronic acid (M) and α-L-guluronic...
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