Kinetics of the apparent non-enzymic browning of potatoes
Darwin A. Bicomong1 and Ponciano S. Madamba2
The kinetics of apparent non-enzymic browning (NEB) in dehydrated diced potatoes were studied by exposing product samples (known equilibrium moisture contents from 4.4 to 14.7%db) to 40, 60 and 80oC and from 7 to 79% relative humidity. The color (O.D./g sample) changes in the potato extract (using 10%NaCl) during storage were determined. No lag phase or initial induction period was observed before the main browning period within the range of the variables studied. A zero-order reaction was found for NEB of potatoes with reaction rate constant, k, increasing with moisture content and temperature. The temperature dependency of the reaction followed a simple Arrhenius type relationship and the calculated activated energy, (Ea= 42.1 +0.8kJ/mol) appeared to be independent of temperature and moisture content over the 40-80oC range. Shelf-life studies of dried potatoes were conducted based on k and Ea and the “limit-of-acceptability”, set at 0.45 O.D. / g sample. The kinetic model was validated under various temperatures (50, 60, 70, 80 and 90oC) and moisture content levels (4.8-17.1% db). The predicted shelf life tended to underestimate the actual shelf life showing consistency of the predictions by less than 10% error.
1Chemical Engineering Student, Department of Chemical Engineering; 2Associate Professor, Division of Agricultural and Bio-Process Engineering (ABPROD), Institute of Agricultural Engineering (IAE), College of Engineering and Agro-industrial Technology (CEAT), University of the Philippines Los Baños (UPLB)