Effects of Drying Temperatures and Glycerol Concentrations on Properties of Edible Film from Konjac Flour Lamul Wiset 1 , Nattapol Poomsa-ad 2 , and Prayoon Jomlapeeratikul 3 Faculty of Engineering/Mahasarakham University, Mahasarakham, Thailand Email: { 1 Lamulwiset, 3 prayoon_eng}@hotmail.com; 2 nattapol.p@msu.ac.th Chaleeda Borompichaichartkul Faculty of Science, Chulalongkorn University, Bangkok, Thailand Email: chaleedab@hotmail.com Abstract—The objective of this research was to study the effect of drying temperatures and glycerol concentrations on properties of edible film from konjac flour. Glycerol was used as plasticizer at the concentrations of 0 and 0.3% w/v for film forming. The drying process was done using heat pump dryer at various temperatures of 45, 50 and 55 C. Sample was dried until the final moisture content was down to 1% wet basis. Then, film samples were taken to determine various properties including, tensile strength, elongation, water vapor permeability and solubility. The results found that konjac film without glycerol had a higher tensile strength than that konjac film with 0.3% glycerol. Also, tensile strength was significantly increased with the increasing of drying temperature (p ≤ 0.05). For the elongation, water vapor permeability and solubility of film, these properties of konjac film with 0.3% glycerol were higher than that konjac film without glycerol. The elongation was significantly decreased when the drying temperature increased (p ≤ 0.05). Moreover, water vapor permeability and solubility were significantly difference at various drying temperature (p ≤ 0.05). The drying temperature at 50 C provided the lowest water vapor permeability and the highest solubility Index Terms—edible film, konjac, drying, plasticizer, film properties I. INTRODUCTION The wide use of petroleum-derived plastics and the negative impact of these on the environment prompted the search for biodegradable materials obtained from renewable resources. The use of agriculture derived biopolymers, such as proteins and glucomannan, appears as an interesting alternative to synthetic plastics for some applications, especially those with a short life-time, such as food packaging, and generates new uses of higher added value for agriculture products [1]. Edible films and coatings have long been used to protect food products, improving food quality. The application of edible films is a technological hurdle that Manuscript received August 31, 2013; revised November 2, 2013. can modify vegetable tissue metabolism while affecting respiration; they can be conveyors of antimicrobials, antioxidants and other preservatives; they can enrich product formulation, carrying vitamins and minerals [2]. In general, edible films and coatings provide the potential to control transport of moisture, oxygen, aroma, oil, and flavor compounds in food systems, depending on the nature of the edible film-forming materials [3]. The physical and mechanical properties of edible films are a subject of great importance due to their influence on product performance and consumer acceptance. Konjac glucomannan (KGM) is the main renewable products which are economical, readily available, biodegradable and highly safe. They possess special nutritional and/or health-protective functions as well as good film-forming properties. For instance, KGM is found to have functions such as has the ability to lower blood cholesterol and sugar level, help with weight loss, promote intestinal activity and immune function [4]. One important component of edible films is the plasticizer which is required to overcome film brittleness and improve its flexibility and extensibility [5]. Plasticizers are low molecular weight components added to films to reduce their brittleness, by increasing the space between polymer chains and, consequently, decreasing the intermolecular attractive forces and increasing the flexibility and extensibility of the material [6], [7]. An alternative to reduce the hygroscopicity of films is the utilization of hydrophobic plasticizers. The effect of given drying conditions depends on various characteristics of the raw material, such as a pre- existing gel phase or the occurrence of thermal gelation during drying. Moreover, various phenomena, such as the transition from an amorphous to a vitreous phase, the appearance of phase separation (thermodynamic incompatibility) and crystallization, may occur. The interaction between the physicochemical nature of biopolymers and the drying conditions is very important [8]. Banker et al. [9] show that found the water vapor permeability of cellulose films increased as the film Journal of Medical and Bioengineering Vol. 3, No. 3, September 2014 171 ©2014 Engineering and Technology Publishing doi: 10.12720/jomb.3.3.171-174