Submitted to: Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/21/2010
Publication Date: 2/10/2011
Citation: Shih, F.F., Daigle, K.W., Champagne, E.T. 2011. Effect of rice wax on water vapor permeability and sorption properties of edible pullulan films. Food Chemistry. 127:118-121. Interpretive Summary: Rice bran oil (RBO) is a valuable milled rice co-product. However, only about 800 MT of RBO, out of an estimated 7 MMT annual total, is currently available in the market. The main reason for this lack of availability is the high content of waxy materials (up to 5% RBO) that cause difficulties in the RBO processing. Recently, this waxy component has been found to be a rich source of high molecular weight fatty alcohols, known as policosanols, which are useful ingredients for the treatment of hypercholesterolemia. As a result, there has been an increased interest in the processing and utilization of RBO and its components. Food grade rice bran wax is now commercially available, and is becoming a popular ingredient in foods for health-conscious consumers. Edible films have been studied extensively in recent years, as a special form of food, or as carriers of flavor and nutritional additives. In this study, we prepared edible films using a good film-forming polysaccaride (pullulan) with various degrees of the water resistant rice wax. Freestanding composite films were obtained with up to 50% rice wax, which showed superior water barrier properties. Water adsorption characteristics of the films were also examined, providing information useful in evaluating the films for stability as a food product.
Technical Abstract: Edible pullulan films were prepared by substituting the pullulan with various ratios of rice wax. Freestanding composite films were obtained with up to 50% rice wax. Water vapor barrier properties of the film were improved with increased addition of the rice wax. Moisture sorption isotherms were also studied to examine the impact of rice wax on the water sorption characteristics of the film. The Brunuer-Emmet-Tetter (BET) and Guggenheim-Anderson-deBoe (GAB) sorption models were tested to fit the experimental data. The models gave a good fit up to the water activity (Aw) of 0.55 for BET, and a full range of Aw from 0.12 to 0.95 for GAB (R2 ' 0.98). Changes in the sorption parameters, particularly in the decrease in monolayer moisture content (Mo), reflect the trend of reduced hydration capacity with increased addition of rice wax, providing useful information on water activity conditions to achieve stability for the composite films.