Patent ID: 7348180

Claim:
A method of evaluating freshness of a fish product comprising: cutting a small quantity of sample from the fish product; adding an effective amount of a staining reagent comprising at least one of a cell-permeant dye and a cell-impermeant fluorescent dye onto the sample; wherein the cell-permeant dye converts to a compound emitting a first fluorescence in the presence of intracellular esterase activity; wherein the cell-impermeant fluorescent dye can penetrate into compromised membranes of cells and emit a second fluorescence; and wherein the first fluorescence and the second fluorescence are distinguishable from each other when the indicator reagent comprises both the cell-permeant dye and the cell-impermeant dye; incubating the sample added with the staining reagent for a predetermined duration; and determining the freshness of the fish product based on at least one parameter selected from the group consisting of (1) the intensity of the first fluorescence emitted from the incubated sample, (2) the intensity of the second fluorescence emitted from the incubated sample, (3) a first distance starting from the top of the sample to the farthest point in the sample at which the first fluorescence is detected, (4) a second distance starting from the top of the sample to the farthest point in the sample at which the second fluorescence is detected.