Patent ID: 8325345

Claim:
A method of evaluating the quality of frying oil, the method comprising the steps of: providing frying oil that potentially comprises free fatty acid content; providing an oil-absorbent sampling substrate, wherein the sampling substrate contains a plurality of test zones, wherein each test zone is responsive to free fatty acid; contacting the oil with the sampling substrate such that a sample of the oil is brought into contact with at least a portion of each of the test zones; directing light onto the plurality of test zones; measuring the amount of light reflected from each test zone; generating signals proportional to the amount of light reflected from each test zone; summing the signals together so as to provide an integrated signal; correlating the integrated signal with the free fatty acid content of the oil; and reporting an indication of the oil quality of the oil by an optical interrogation device, wherein the indication is associated with the free fatty acid content of the oil.