Hydration Rates for Various Types of Mexican Maize Based on Single‐Kernel Measurements

Hydration kinetics for sound maize kernels in liquid water, determined by single‐kernel measurements for three different Mexican maize types, yielded water diffusion coefficients ordered as Celaya corn > Toluca corn > Palomero corn, at all temperatures examined. These diffusion coefficients are lower than those reported earlier for maize grains, possibly due to the fact that in the present study damaged kernels were rigorously excluded. The energies of activation determined from the Arrhenius plots were ordered as Palomero corn > Celaya corn = Toluca corn and were similar in value to those reported earlier for other maize types. Damage to the surface of the maize kernels during the hydration experiments occurs at a significant frequency. Even minor surface lacerations can strongly affect the rate of hydration of the kernels. Experiments with maize grains selectively varnished in various parts of their surface show that the entry of water into the kernels occurs predominantly through the pericarp, not through the tip cap, though the tip cap has a higher water inflow per unit area.