|
Michael W. Allen, Ph.D
Fluorescence Product Manager
Regulatory agencies in the United States and across Europe have established strict upper limits on acceptable levels of histamine in canned seafood products. Testing is also routinely performed in canneries during the production process, as well as on final products. The histamine detected in scombroid fish, which include tuna, mahi mahi, bluefish, sardines, mackerel, amberjack, and abalone, is a product of spoilage due to time and temperature abuse. Therefore, histamine concentration serves as an important quality and safety indicator in seafood products. The Thermo Scientific Quantech™ Digital Filter Fluorometer is ideal for the measurement of histamine levels using fluorescence detection.
Elevated histamine concentration is a result of improper handling, temperature control, and elevated levels of histamine producing bacteria in the marine environment. Most of these bacteria are present on the gills or in the digestive system of the fish. The defense mechanisms of the fish, which protects surrounding tissues from bacterial infection, no longer function after the death of the fish. For this reason, most sampling for histamine concentration takes place from the tissues present in the gut.
The implication of elevated levels of histamine is severe. Histamine poisoning induces a continuum of physical responses from becoming very ill with what appears to be a seafood allergy to a minor tingling and burning sensation in the mouth or rash. Once ingested, large doses of histamine can cause elevated gastric secretion, constriction of the airway, and dilation of the vascular system. It is therefore critically important for fisheries, canneries, and fish processors to keep a tight control on the concentration of histamine in the products they produce.
Specifically, the US FDA has established a 50-ppm maximum histamine limit. Fluorescence analysis performed on the Quantech Digital Filter Fluorometer with o-phthalaldehyde (OPT) is a sensitive enough to detect histamine at the 0.1 ppm concentration level, well below the common 10 ppm levels found in seafood samples. Moreover, fluorescence analysis published by Ambrose is equal in accuracy to Amino Acid Analysis performed concurrently (1).
The AOAC method of analysis for histamine in seafood (method number 977.13) requires excitation with a mercury lamp and the use of a narrow bandpass filter at 350nm. OPT has a fluorescence maximum near 444 nm. The recommended configuration for the measurement is the Wide Band Model Quantech Digital Filter Fluorometer equipped with a NB360 and SC415 emission filter. These filters are included as standard with the Wide Band model.
The assay is relatively simple requiring the preparation of a standard curve using known concentrations of histamine. The samples used for analysis are passed over an ion-exchange resin and the test portion of the mixture is mixed with the OPT in strong acid to produce the fluorescent product. The histamine concentration is determined from the linear calibration curve of known standard.
|
0 Items