A method of determining authenticity of an ingestible product purportedly from a batch of saccharide-marked ingestible product is provided. The ingestible product is a food, beverage, or pharmaceutical, for example. The method includes identifying a sample of the ingestible product to be tested; and testing the sample for a marked presence of the saccharide using a saccharide-specific binding protein. The ingestible product is not authentic when the testing demonstrates an unexpected change in the marked presence of the saccharide, and the ingestible product is authentic when the testing demonstrates no unexpected change in the marked presence of the saccharide.