A method of measuring mechanical damage to a grain, such as corn, includes applying a reacting solution to a sample of corn. The solution contains a material, such as 8-anilino-1-naphthalene sulfonic acid, that reacts selectively with the damaged portion of the corn kernels, i.e., the internal protein that is exposed when the outer shell is penetrated or breached. Excess solution is washed off; and the kernels are dried for convenience of handling. The dried corn is ground to a uniform fineness and then spread over a predetermined area. What is inherently a three-dimensional or volume phenomena (damage) is converted to a two-dimensional or area measurement. The sample is exposed to ultraviolet light; and induced fluorescence is measured. The output of the measuring system is linearly related to, and thus a measure of the mechanical damage of the sample.