American Journal Applied Sciences 5 (11): 1535-1542, 2008 ISSN 1546-9239 © 2008 Science Publications Corresponding Author: Juntanee Uriyapongson, Department of Food Technology, Faculty of Technology, Khon Kaen University, Khon Kaen, 40002, Thailand, Tel: +66-43362132, Fax: +66-43362131, 1535 Amphoteric Starch in Simultaneous Process Preparation with Box-Behnken Design for Optimal Conditions 1 Sopa Cansee, 2 Juntanee Uriyapongson, 1 Commueng Watyotha 1 Thavachai Thivavarnvongs and 3 Jatuphong Varith 1 Department of Agricultural Engineering and 2 Department of Food Technology, Khon Kaen University, Khon Kaen 40002, Thailand, and 3 Department of Agricultural and Food Engineering, Maejo University, Chiang Mai 50290, Thailand Abstract: Cassava starch was chemically modified to produce an amphoteric starch. The amphoteric starch was prepared in a simultaneous process which was evaluated in relation to four factors: temperature (45-55 °C), 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC, 4-12%) and sodium tripolyphosphate (STP, 2-8%) concentrations, and reaction time (2-6 h). The extent of amphoteric starch produced was determined by the degree of substitution (DS) of the nitrogen content and percentage of phosphorus content. In addition, a quantitative response of yield and whiteness as well as pasting characteristics were tested. Response surface analysis showed that the DS (0.01-0.05) increased with increasing temperature, CHPTAC and reaction time. The phosphorus content (0.09- 0.34%) followed a parabolic shape with all of the factors. Consequently, the response surface methodology appears to be a powerful technique to determine the optimal conditions for the production of amphoteric starches. Keywords: Amphoteric starch, Box-Behnken design, Response surface methodology INTRODUCTION Cassava starch is an important food ingredient in tropical countries such as Brazil, Nigeria, Indonesia and Thailand. Cassava starch has often been modified, and Thailand is also a country where modified starch from cassava starch is produced in large scale [1] . The traditional starch modifications are usually carried out in an aqueous medium and require a high concentration of modifying reagent to achieve the desired degree of chemical binding [2] . The commercial amphoteric starches consist of cationic and anionic modifications. Typically, cationic derivations are starch ethers prepared from tertiary amino or quaternary ammonium reagents, whereas anionic agents substitute with phosphate, phosphonate, sulfate, sulfonate or carboxyl groups [3] depending on specific objectives. The main applications of amphoteric starch are in the paper industry as wet-end additives, coating binders, retention aids, and overall dry-strength agents [4] . The use of recycled fibre has been growing steadily since 1984 to around 50% (the recycling rate is calculated on the basis of recovered paper used in recycling compared to total paper consumption) of the fibre mass used in paper production [5] . The increased recycling of fibres has decreased the pulp strength of the bonding fibres. The amino groups on the amphoteric molecules create new hydrogen bonds with hydroxyl groups on the cellulose. Thus, if the number of hydrogen bonds is increased, stronger paper is obtained. Therefore, the use of amphoteric starch has been steadily growing alongside with using of recycled fibre in the paper industry. Preparation of amphoteric starches has employed two-step treatments of starch with cationic and anionic modifying reagents [4, 6, 7, 8] . The traditional dual treatments of the amphoteric starch preparations are not resource efficient and require heat for reaction and a drying process, water for washing and unnecessary management. The simultaneous process of amphoteric preparation can be of economic benefit. Review of the literature shows that only Youquan et al. [9] have studied preparation of phosphate amphoteric starch in a simultaneous process, and its application. The results showed that amphoteric starch has more advantages than cationic starch in the paper industry. It can