Simulation of starch gelatinisation during baking in a travelling-tray oven by integrating a three-dimensional CFD model with a kinetic model Nantawan Therdthai a,1 , Weibiao Zhou a,b, * , Thomas Adamczak c a Centre for Advanced Food Research, University of Western Sydney, Hawkesbury Campus, Penrith South DC, NSW 1797, Australia b Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore c BRI Australia Limited & Value Added Wheat CRC, North Ryde, NSW 2113, Australia Received 10 November 2003; accepted 16 February 2004 Abstract To simulate the progress of starch gelatinisation during a continuous industrial baking process, a three-dimensional computa- tionalﬂuiddynamics(CFD)modelwithmovinggridswasintegratedwithakineticmodel.Crumbtemperatureproﬁlessimulatedby the CFD model were utilized to estimate the degree of starch gelatinisation at diﬀerent positions within a loaf baked in a travelling- tray oven. The gelatinisation proﬁles were predicted to be asymmetrical both horizontally and vertically across the loaf. In addition, variations in gelatinisation rate were found among the four tins within a single tray. Due to the fact that starch gelatinisation was claimed to be an indicator of baking progression, it was utilised to check the completeness of baking under various oven operating conditions. The results in this paper also assured the completion of baking under a particularly modiﬁed operating condition that could provide the nearly optimum tin temperature proﬁle for baking white sandwich bread with a baking time of 25 min. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Starch gelatinisation; Bread; Baking; CFD; Modelling 1. Introduction Baking is a process where semi-ﬂuid dough is trans- formed to predominantly solid baked bread. The transformation is characterised by the corresponding rheological properties, which is aﬀected by the baking conditions. The process of the transformation involves crucial steps induced by starch gelatinisation and tran- sition from gel to coagel. Medcalf (1968) stated that starch gelatinisation properties appear to be of central importance. Starch gelatinisation occurs only in the presence of water. It starts when amylose and amylopectin, which form crystalline together, are heated up to the level where water has enough energy to break its bond (Medcalf, 1968). Engelsen, Jensen, Pedersen, Norgaard, and Munck (2001) noticed that the temperatures for the start and ﬁnish of starch gelatinisation were at approx- imately 55 and 85 °C respectively. A series of steps during starch gelatinisation includes swelling, melting, disruption of starch granules and exudation of amylose. It can be enhanced when the gluten phase is changed as viscous dough transforms into an elastic material (Bloksma, 1986). Due to protein denaturation, water adsorbed in the gluten during dough making stage is released, which is then used for starch gelatinisation (Marston & Wannan, 1976; Medcalf, 1968). Before baking, water in the dough is combined with starch, protein and pentosan. After baking, it is only associated with starch and pentosan (Bushuk, 1966). Factors inﬂuencing the starch gelatinisation proper- ties include starch molecular size, proportion of amylose and amylopectin, granule size, presence of surface active agents, and inorganic salts (Medcalf, 1968). Sahlstrom, Brathen, Lea, and Autio (1998) studied the inﬂuence of starch granule size distribution on bread characteristics. Journal of Food Engineering 65 (2004) 543–550 www.elsevier.com/locate/jfoodeng * Corresponding author. Tel.: +65-6874-3501; fax: +65-6775-7895. E-mail address: chmzwb@nus.edu.sg (W. Zhou). 1 Current address: Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand. 0260-8774/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2004.02.018