© All Rights Reserved *Corresponding author. Email: zuraidaa@iium.edu.my International Food Research Journal 19(2): 715-719 (2012) * Zuraida, A., Yusliza, Y., Anuar, H. and Mohd Khairul Muhaimin, R. Kulliyyah of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728, Kuala Lumpur, Malaysia The effect of water and citric acid on sago starch bio-plastics Abstract: Starch is a biodegradable polymer produced in abundance from many renewable resources. This study examined the infuence of citric acid (0-40% w/wt%) ) and water (0-40% w/wt%) as secondary additive and glycerol as plasticizer on the mechanical properties of bio-plastic starch (BPS) from Malaysian sago. The CA content varies from 0 to 40 w/wt% while water was also varied from 0 to 40 w/wt%. FT-IR spectroscopy showed that acid citric improve the properties of BPS and water give negative effects to the carbon hydrogen- bond. It is obvious that the addition of the CA at 30 wt/wt% improve the mechanical property of BPS to more than 40% compare to the addition of water. Keywords: Component, sago, starch, melt processing, citric acid Introduction Particular attention has been given in the recent years for the development of biodegradable polymers from renewable resources, especially for packaging and disposable applications to maintain sustainable development of economically and ecologically attractive technology, towards greener environment (Schlemmer et al., 2010; Fischer et al., 2011). Among these biopolymer, starch is one of the promising materials because of its large availability, low cost, renewable resources and inherent biodegradability (Shi et al., 2007). Native starch is the major sources of polysaccharide in plants. Previously many researchers have focused on starches from corn, wheat and potato and very few reports are available on sago starch. Sago starch is produced from sago palm (Metroxylon spp.), which is also known as rumbia. Sago is initially presents in South East Asia and can be found especially in Sarawak, Malaysia. Sago starch is commonly used as functional ingredient (e.g. thickener, stabilizer, gelling agent) in the food industry (Mohamed et al., 2008). In order to adjust the properties of these starch-based materials for non-edible applications, it requires combination with other polymers that may need for starch modifcations such as esterifcation, grafting and reactive or melting extrusion of thermoplastic starch (TPS), which is also known as bioplastic starch (BPS) (Carvalho, 2008). BPS is an amorphous or semi-crystalline polymeric material composed of gelatinized or destructurized starch containing one or a mixture of plasticizer (Liu et al., 2009). Various plasticizer and additives have been evaluated for the gelatinization of starch during thermal processing. Among the plasticizers, water is the most commonly used in the thermal processing of starch based polymers. BPS containing only water alone however, results in poor mechanical properties such as the brittleness due to the fast retrogradation (recrystallization). Therefore, other non-volatile plasticizers are investigated to improve the processing ability and product properties of the BPS such as, glycerol, glycol and sorbitol, sugars, urea, formamide, acetamide,ethylenebisformamide, ethanolamine and citric acid. This study was carried out to investigate the potential of sago starch as natural sources for the production of BPS and to optimize the process condition of the starch plasticized with glycerol, and the effect of water and citric acid as co-plasticizer on the mechanical and thermal properties of the BPS. Further, morphological structure of the samples was observed by using scanning electron microscope (SEM). Materials and methods Materials Sago starch powder (25% amylose) was purchased from Hup Seng Heng Sdn Bhd, Malaysia, glycerol (95% purity) with density of about 1.261 g/cm³ and citric acid were supplied by Merck. Fabrication process In this experiment there were two compositions prepared. First is a mixture of starch and glycerol.