Monitoring the contents of biogenic amines in sufu by HPLC with SPE and pre-column derivatization

Sufu is a nutritious fermented food whose consumption is currently increasing in many countries. The purpose of this study was to develop an HPLC method with SPE and pre-column derivatization for monitoring the content of biogenic amine in sufu and to understand the differences in the contents of biogenic amines with different processing technologies. Biogenic amines in sufu were extracted with 6% trichloroacetic acid, derivatized with 4-chloro-3,5-dinitrobenzotrifluoride, purified with Waters Oasis MCX cartridge, separated by HPLC using gradient elution, and detected by spectrophotometric UV at 254 nm. The method linearity, calculated for each biogenic amine, has a correlation coefficient higher than 0.9915. Detection limits of the biogenic amines were ranged from 0.016 mg/kg for putrescine to 0.067 mg/kg for spermine. Spiking experiments showed that the overall recoveries ranged between 83.6% and 103.5% with relative standard deviations of 1.26–5.24%. Of the seven biogenic amines under study, at least four biogenic amines were detectable in different kinds of sufu. Tryptamine, putrescine, histamine, and tyramine were the most prevailing biogenic amines in all sufu samples. The mean values of histamine, tryptamine, phenylethylamine, tyramine, putrescine, spermidine and spermine determined in samples were found to be 18.2 mg/kg, 39.0 mg/kg, 1.1 mg/kg, 21.7 mg/kg, 34.6 mg/kg, 11.1 mg/kg, and 8.7 mg/kg, respectively. The total contents of biogenic amines in bacteria fermented sufu samples (129.0 mg/kg) were slightly lower than those in enzymatically ripened sufu samples (137.7 mg/kg). The concentrations of biogenic amines detected in sufu samples were below the maximum permissible limits.