KINETIC COMPENSATION EFFECT ON CASSAVA LINAMARIN DEGRADATION AT VARYING PH, OPTIMUM TEMPERATURE AND PURIFIED Β-GLUCOSIDASE GENETICALLY ENGINEERED FROM SACCHAROMYCES CEREVISIAE.
Ikya, J.K., 1Ariahu, C. C1 and J.O.I. Ayatse2
1Department of Food Science and Technology, University of Agriculture, Makurdi.
2Department of Biochemistry University of Agriculture, Makurdi.
E-mail: aveyina2012@gmail.com
ABSTRACT
Heat degradation kinetics of linamarin were evaluated to obtain reaction rate constants Kmin-1 at varying pH3.5, 6.8 and 10.5. Reaction rate Data obtained were analyzed using the Arrhenius and absolute reaction rate models to obtain activation energies (Ea), enthalpy (AH ) and entropy (AS#).. The thermodynamic parameters were subjected to kinetic compensation analysis to obtain iso-kinetic temperatures (Tc), rate constants (kc) and free energies (AGW) related to the degradations of linamarin. at varying pH. The results showed that the Isokinetic Temperature (Tc) and Constant (Kc) for Degradation of at pH 3.5, Tc = 320k equivalent to 470C. The isokinetic constant was 1.25 x 10-3/min. and the least square regression analysis which was applied produced a correlation coefficient r2 value > 0.98. The same pattern was observed for degradation of Cassava linamarin at pH 6.8 and pH 10.5. Data obtained as isokinetic temperature (Tc) is very important and can be employed in control fermentation of foods containing Cassava linamarin. At this temperature, the fermentation processes are independent of environmental conditions. These are derived from Ko vs Ea and DS vs DH relationships respectively and are independent of the environmental variables and presumably applied for predictive purposes. Tc range from 47.0-47.8 this value is usually compared with mean harmonic temperature which TH which was computed in this study as 1340C. From the results TH was far greater than Tc. This observation validated true kinetic compensation effect where increase in Ko values Proportionally increased the Ea values and vice versa. Enthalpy of activation was plotted against the entropy of activation of heat degradation of Cassava linamarin produced 93.8KJ/mol of free energy of activation (DG). The enthalpy of activation varies from 274-302KJ/mol, the plot of this value against enthropy change produce the calculated DG value. Both entropy and enthalpy exhibited marked compensation effect in which increases in DH was accompanied by DG. The computed r2 = 0.98 value calculated by least square regression analysis indicated the fitness of kinetic compensation models in the prediction of environmental conditions.. It was concluded in this study that true kinetic compensation occurred in the degradation of cassava linamarin at varying pH. This study on kinetic compensation can be used for predictive purposes in controlled fermentation of foods in our localities.
Keywords: Kinetic compensation, mean harmonic temperature, Isokinetic Temperature (Tc) Controlled fermentation, pH