title: Thermal inactivation kinetics of β-galactosidase during bread baking.
abstract: In this study, β-galactosidase was utilized as a model enzyme to investigate the mechanism of enzyme inactivation during bread baking. Thermal inactivation of β-galactosidase was investigated in a wheat flour/water system at varying temperature-moisture content combinations, and in bread during baking at 175 or 205°C. In the wheat flour/water system, the thermostability of β-galactosidase increased with decreased moisture content, and a kinetic model was accurately fitted to the corresponding inactivation data (R2=0.99). Interestingly, the residual enzyme activity in the bread crust (about 30%) was hundredfold higher than that in the crumb (about 0.3%) after baking, despite the higher temperature in the crust throughout baking. This result suggested that the reduced moisture content in the crust increased the thermostability of the enzyme. Subsequently, the kinetic model reasonably predicted the enzyme inactivation in the crumb using the same parameters derived from the wheat flour/water system. However, the model predicted a lower residual enzyme activity in the crust compared with the experimental result, which indicated that the structure of the crust may influence the enzyme inactivation mechanism during baking. The results reported can provide a quantitative understanding of the thermal inactivation kinetics of enzyme during baking, which is essential to better retain enzymatic activity in bakery products supplemented with heat-sensitive enzymes.
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, PR China; Laboratory of Food Process Engineering, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, PR China; Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen City, Fujian 361005, PR China. Electronic address: xdchen@mail.suda.edu.cn.
authors.forename: Xiao Dong
authors.initials: XD
authors.lastname: Chen
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Remko M
authors.initials: RM
authors.lastname: Boom
authors.affiliation: Laboratory of Food Process Engineering, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: maarten.schutyser@wur.nl.
authors.forename: Maarten A I
authors.initials: MA
authors.lastname: Schutyser
mesh_terms: D001939:Bread / Q000032:analysis*; D004795:Enzyme Stability; D005433:Flour / Q000032:analysis; D005511:Food Handling; D006358:Hot Temperature; D007700:Kinetics; D014908:Triticum / Q000737:chemistry* / Q000201:enzymology; D001616:beta-Galactosidase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001616:beta-Galactosidase
keywords: Bread baking; Drying; Enzyme inactivation; Kinetic model; β-Galactosidase