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Whey protein isolate (WPI) and Carboxymethyl Cellulose (CMC) blend films: effect of CMC/WPI ratio on physicochemical properties

G. Azevedo1, L.M. Pastrana 1 and M.A. Cerqueira 1

1 INL - International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga s/n 4715-330, Braga, Portugal

Whey protein isolate (WPI) has received attention to produce edible and biodegradable films. They exhibit good mechanical and oxygen barriers properties compared with edible films produced with other commercial proteins (e.g. corn zein, soy protein isolate and wheat gluten). However, whey protein isolate films have demonstrated few limitation on mechanical and barrier properties. So, plasticizers (e.g. glycerol and sorbitol) are added to improve resistance to moisture transfer, as well as to avoid brittleness while enhancing flexibility and extensibility. On the other hand, the addition of carboxymethyl cellulose (CMC), one of the most used derivatives of cellulose, can also be used to improve the final properties of protein-based films. Based on this, WPI and CMC were used to produce edible films for food packaging applications. The effect of CMC (2 % w/w) addition on WPI-based films with different concentrations (2, 4, 6, 8 and 10 % w/w). These were compatibilized by glycerol and prepared using solution casting method. Barrier (water vapour permeablity), mechanical (tensile strenght and elongation at break), thermal (thermogravimetrical analysis), surface (contact angle) and optical (opacity and color) properties were determined. Results showed that CMC and WPI blend films can be used to produce edible films with good processability. However, when the content of WPI increased to 8 and 10 % w/w, CMC/WPI films became brittle when handling. Their surfaces appeared smooth, without visible pores or cracks. The opacity of CMC/WPI films increased for higher WPI concentrations as well as the thickness values (from 0.121 ± 0.006 mm to 0.389 ± 0.017 mm). Concerning the mechanical properties, films made with WPI and CMC blends are stronger and more stable than WPI films without CMC. Further studies will studied the use of the developed WPI/CMC blends as films and coatings of food products.

Acknowledgements:

Conducted under the project “MobFood – Mobilizing scientific and technological knowledge in response to the challenges of the agri-food market” (POCI-01-0247-FEDER-024524), by “MobFood” Consortium, and financed by European Regional Development Fund (ERDF), through the Incentive System to Research and Technological development, within the Portugal2020 Competitiveness and Internationalization Operational Program.

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