MODELING THE BROWNING KINETICS OF GARLIC

Garlic slices conditioned to corresponding equilibrium moisture conten ts were exposed to water activities (a(w)) from 0.11 to 0.81 (using sa turated salt solutions) at temperatures 50, 60, 75 and 90-degrees-C. N on-enzymic browning in these slices was significantly affected by temp erature and a w as well as time. C.I.E. L(star), a(star) and b(star) v alues for different heat treatments were measured with a hand-held ref lectance meter and compared to the optical index (OI) of the coloured garlic extract (using 10% NaCl solution). The L(star) values correlate d in a non-linear fashion with OI. An initial induction period of slow er browning preceded the main browning period which was temperature an d a(w) dependent. The browning of garlic followed a pseudo-zero order kinetics. A linear rate constant was found as a function of a(w) and a simple Arrhenius relationship characterised its temperature dependenc e. Activation energy and temperature sensitivity (Q10) varied from 76 to 93 kJ/mole and from 2 to 2.8, respectively.