No. 324: A fluorescent detection method to confirm the freshness of a food by sight (October 10, 2011)

A research team led by two professors of Tokyo Institute of Technology, Takanobu Sanji and Masato Tanaka, developed a technology to confirm easily the freshness of a food by sight in a few minutes. The technology is to add a special fluorescent molecule to a biogenic amine in stale fish and meats to shine it in blue. An organic solution mixed with a piece of fish is added by a fluorescent molecule shines in blue under ultraviolet radiation. The staler the sample is, the darker the blue is. 

The research members used a special fluorescent molecule called tetraphenylethylene (TPE). They modified the TPE and gave it a carboxyl group that combines with the amino group of a biogenic amine. TPEs resolved in an organic solvent do not emit fluorescence because they are in an unbound state. However, if biogenic amines with an amino group and the modified TPEs with a carboxyl group are mixed in an organic solution, the biogenic amines come to combine with the modified TPEs and emit fluorescence. The research team examined the freshness of canned tuna using this technology and successfully detected histamine with a concentration of 20 ppm. The upper limit of histamine in canned tuna subject to regulation set by the FDA’s standards is 50 ppm.