Formation and characterization of shellac-hydroxypropyl methylcellulose composite films Youngjae Byun, Amanda Ward 1 , Scott Whiteside * Department of Food, Nutrition, and Packaging Science, Clemson University, B-212 Poole & Agricultural Center, Clemson, SC 29643-0320, USA article info Article history: Received 6 July 2011 Accepted 14 October 2011 Keywords: HPMC Shellac Composite Biopolymer abstract Shellac-hydroxypropyl methylcellulose composite films (Sh-HPMC-CFs) were produced and the effects of emulsifier and shellac concentration on the Sh-HPMC-CFs were investigated. Two emulsifiers, stearic acid (SA) and lauric acid (LA), with three ratios of shellac to emulsifier (100:1, 20:1, and 10:1) were tested to select the best ratio of shellac to emulsifier before testing the effect of shellac concentration. When compared to pure HPMC film, the WVP was decreased by 6 and 11% in the Sh-HPMC-CFs containing shellac to LA (ShLA) ratios of 100:1 and 20:1, respectively. However, all the ShSA-HPMC-CFs had higher WVP than the pure HPMC film. In relation to mechanical properties, the ShLA(20:1)-HPMC-CF had the lowest reduction in TS when compared to a pure HPMC film. Therefore, ShLA(20:1) was selected for further characterization. Surface morphology, cross sectional image, thermal stability, WVP, and mechanical properties of the Sh-HPMC-CFs were also measured at varying shellac concentrations (0.1, 0.5,1.0, and 1.5%). The 0.1 and 0.5% Sh-HPMC-CFs had good distribution of shellac in the film structure while the 1.0 and 1.5% Sh-HPMC-CFs exhibited some agglomeration of shellac. The 0.1 and 0.5% Sh- HPMC-CFs had better moisture barrier than the pure HPMC film. All Sh-HPMC-CFs had better thermal stability than the pure HPMC film and its thermal stability increased as shellac concentration increased. Published by Elsevier Ltd. 1. Introduction Plastics are one of the most commonly used materials in the food packaging industry due to their ability to preserve the sensory properties and nutritional values in food products. The market size of rigid and flexible plastics was about 45% of the total packaging industry in 2009 (Barnett, 2010). It is expected that the market size of plastics will continue to grow. However, the price of crude oil has steadily increased during last decade and oil markets are very unstable and sensitive to political issues. There has been a substantial increase in the production costs of synthetic polymer (e.g. polypropylene, polystyrene, and polyethylene) due primarily to the recent rise in the cost of crude oil. In addition, there is a growing concern with consumers regarding the detrimental effects synthetic plastics have on the environment (Tharanathan, 2003). There is a huge demand for the utilization of natural poly- mer sources as food packaging materials (Byun, Darby, Cooksey, Dawson, & Whiteside, 2011; Byun, Kim, & Whiteside, 2010). Biopolymers are considered appealing alternatives to synthetic plastics since they are typically derived from renewable and abundant resources. Much research has been done on the appli- cation of biopolymers in food packaging (Byun, Bae, & Whiteside, 2012). Up until the early 2000’s, the high cost of biopolymers has been a major factor limiting their utilization. However, the current increase in crude oil prices have allowed biopolymer films to be more cost competitive. Hydroxypropyl methylcellulose (HPMC) could be used as a potential replacement for synthetic plastics due to its good film forming properties, flexibility, biodegradability, clarity, and its gas barrier properties (Jiménez, Fabra, Talens, & Chiralt, 2010; Villalobos, Hernandez-Munoz, & Chiralt, 2006). Currently, HPMC is primarily used as a coating for pharmaceuticals. On tablets, HPMC acts as a hard outer coating protecting the medicine against light, moisture, and shape distortion and it is also used to mask unpleasant tastes and textures of certain pharmaceutical products (Sakata, Shiraishi, & Otsuka, 2006). However, HPMC has certain limitations in food packaging applications due to its poor moisture resistance. Recent research has been focused on improving the barrier properties of HPMC by incorporating nano-fibers (de Moura et al., 2011), fatty acids (Jiménez et al., 2010), and essential oils (Sánchez-González, Vargas, González-Martínez, Chiralt, & Cháfer, 2009). According to Pastor, * Corresponding author. Tel.: þ 1 864 656 6246; fax: þ 1 864 656 4395. E-mail address: wwhtsd@clemson.edu (S. Whiteside). 1 Author Amanda Ward has equivalently contributed on this paper as a first author. Contents lists available at SciVerse ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd 0268-005X/$ e see front matter Published by Elsevier Ltd. doi:10.1016/j.foodhyd.2011.10.010 Food Hydrocolloids 27 (2012) 364e370