Communication A Kinetic Study on Corn Gluten Hydrolysis In the present study, the hydrolysis of corn gluten was performed by using two commercial enzymes, Protamex and PTN, to investigate the reaction kinetics. The reactions were carried out for 10 min in 0.1 L of aqueous solutions contain- ing 10, 20, 30 and 40 g protein L –1 corn gluten at various temperature and pH va- lues. The progress of the reactions was monitored by a pH-stat method. It was found that the kinetics of corn gluten hydrolysis by Protamex and PTN obey the Michaelis-Menten model and higher catalytic yields were obtained with Protamex than PTN at all of the experimental conditions applied. Keywords: Alcalase, Corn gluten, Hydrolysis, Kinetics Received: September 16, 2008; revised: October 14, 2008; accepted: October 22, 2008 DOI: 10.1002/ceat.200800468 1 Introduction In the food industry, proteins represent an important class of functional ingredients because they possess a range of dynamic functional properties [1]. The protein sources most commonly used in nutritional products are casein and whey proteins. However, plant proteins have recently been investigated as an alternative to animal proteins, and are being employed in ever increasing quantities in the food industry since new sources of proteins are required because of increasing global demand [2, 3]. It is possible to modify the functional properties of the proteins by chemical or enzymatic hydrolysis. However, the hydrolysis by chemical reagents produces nonselective by- products. The use of enzymes provides milder process condi- tions and allows for a selective hydrolysis of the proteins in- volved [3, 4]. The kinetic study of protein hydrolysis is quite complicated due to the various types of peptide bounds involved and their differing vulnerability to attack by enzymes during the hydro- lytic process [5]. In general, the reaction rates of enzymatic hy- drolysis are characterized by Michaelis-Menten kinetic models [6–10]. The aim of the present study is to examine the confor- mity of corn gluten hydrolysis to Michaelis-Menten kinetics and to evaluate the influence of temperature and pH on the hydrolysis kinetics. 2 Materials and Methods The corn gluten used in this research was obtained from Car- gill (Istanbul, Turkey). The enzymes used in this work were Protamex (1.5 AU-NH/g), a bacterial protease produced by Bacillus Amyloliquefaciens and Bacillus Licheniformis; and PTN P-110 (110000 LVU/g), a pancreatic trypsin obtained from Novozymes (Istanbul, Turkey). Hydrolysis experiments were carried out in a 200 mL jacketed reactor with magnetic stirring and pH and tempera- ture control. The reactions were carried out for 10 min in 0.1 L of aqueous solutions containing 10, 20, 30 and 40 g pro- tein L –1 corn gluten at various temperatures ranging between 40 and 55 °C, and various pH values ranging between 6.5 and 8.0. These reaction solutions contained ca. 7 AU (= 380600 LVU) enzyme/L for each experiment. In this study, all experiments were carried out at least in duplicate and the reproducibility between trials was within ±5 %. The software package MATLAB 5.0 was used in the numeri- cal calculations. The parameters were evaluated by the non- linear least squares Marquardt-Levenberg method until mini- mal error was achieved between experimental and calculated values. 3 Results and Discussion In order to examine the conformity of the corn gluten hydroly- sis to Michelis-Menten kinetics, Eq. (1), a series of experiments were conducted at protein concentrations varying between 10 and 40 g L –1 by using two commercial enzyme preparations, i.e., Protamex and PTN, at various temperatures and pH val- ues. In order to monitor the progress of the reactions during the experiments, the consumption of base (mmol L –1 ) was in- vestigated with respect to time, and it was observed that it in- creased linearly with time during the 10 min of processing. Hence, the initial reaction rates were determined from the slopes of the linear models that fitted the base consumption data. The models show strong agreement with the experimen- tal data and for the experiments performed using Protamex and PTN, values for the coefficients of determination of great- © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim http://www.cet-journal.com Dilek KılıÇ Apar 1 Belma Özbek 1 1 Department of Chemical Engineering, Yildiz Technical University, Esenler/Istanbul, Turkey. – Correspondence: Prof. B. Özbek (bozbek@yildiz.edu.tr), Department of Chemical Engineering, Yildiz Technical University, Davutpasa Campus, 34210, Esenler/Istanbul, Turkey. Chem. Eng. Technol. 2009, 32, No. 4, 673–675 673