UV-protecting films based on bacterial cellulose, glycerol and polyvinyl alcohol: effect of water activity on barrier, m
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ORIGINAL RESEARCH
UV-protecting films based on bacterial cellulose, glycerol and polyvinyl alcohol: effect of water activity on barrier, mechanical and optical properties Patricia Cazo´n . Gonzalo Velazquez . Manuel Va´zquez
Received: 16 March 2020 / Accepted: 9 July 2020 Ó Springer Nature B.V. 2020
Abstract Biodegradable films based on bacterial cellulose, glycerol and polyvinyl alcohol are a new alternative to develop food packaging with the capacity to retard or inhibit the effect of UV radiation. However, these compounds are sensitive to moisture. Therefore, the purpose of this study was to evaluate the modifications of the mechanical, water vapor permeability and optical properties of these composite films depending on their water activity. Results showed that water molecules acted as a plasticizer
agent, modifying the mechanical, water vapor permeability and optical properties of the developed films. However, an overplastification process took place at higher activity water, resulting in a weakness of film structure and decreasing drastically the elongation. The transmittance in the UV–VIS light region decreased when the activity water increased. No significant variations were observed in color, transparency or opacity properties.
P. Cazo´n M. Va´zquez (&) Department of Analytical Chemistry, Faculty of Veterinary, University of Santiago de Compostela, 27002 Lugo, Spain e-mail: [email protected] G. Velazquez Instituto Polite´cnico Nacional, CICATA unidad Quere´taro, Cerro Blanco No. 141, Colinas del Cimatario, 76090 Quere´taro, Mexico
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Cellulose
Graphic abstract
Keywords GAB model Moisture adsorption isotherms Plasticization Bacterial cellulose Mechanical properties UV-barrier properties
Introduction Food packaging materials play a crucial role in the distribution and commercialization of food, allowing its preservation, protecting it against physical damage as well as contamination from chemical or biological agents (Giuggioli et al. 2017; Lo´pez-Palestina et al. 2019). In recent years, there has been a growing interest in developing new biopolymeric materials from renewable sources with biodegradable properties (Embuscado and Kerry 2009; Pang et al. 2019). Cellulose is one of the main biodegradable materials studied as a raw material for films or coatings intended for applications in food packaging. Cellulose is the most abundant natural compound on earth, being the main component of the plant cell wall (Cazon et al. 2017). It has demonstrated interesting potential as an effective biopolymer in several fields. The structural characteristics of the biopolymer cellulose from bacterial (BC) are far superior to those of vegetable cellulose (Shah et al. 2013) due to its high purity and absence of plant remnants (Shah et al. 2013; Keshk 2014; Jozala et al. 2016).
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However, the use of BC as a food packaging material has not been spread faster mainly because of some drawbacks including the high cost of BC compared to vegetable cellulos
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