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Biogenic amines and polyamines were studied in 18 market samples of spinach. Histamine and spermidine were detected in relatively high amounts in all samples within the ranges of 9.5-69.7 and 15.6-53.0 mg/kg, respectively. Other biologically active amines were either detected at low levels or not found at all. Changes in amine content during storage at 6 degrees C were studied. The content of most of the amines remained constant during storage, with the exception of spermidine and histamine. Spermidine showed a clear decreasing trend, whereas histamine significantly increased in all trials, but decreased at the end of the storage in two of the trials. Trials showing a decrease in histamine content also showed the highest spermidine decrease and recorded the highest pH values. Microbial loads throughout storage were also followed, with Pseudomonadaceae and Enterobacteriaceae being the predominant bacterial groups. Trials with higher microbial loads in initial samples also showed the highest histamine content in these samples. Potential explanations for both the formation and the degradation of histamine during storage are discussed.

A total of 364 bacterial isolates, obtained from spinach leaves, were assayed in a decarboxylase broth containing histidine, lysine, and ornithine to check their ability to produce biogenic amines, and then quantified by high-performance liquid chromatography. Among these isolates, 240 formed cadaverine, 208 formed putrescine, and 196 formed histamine, in widely varying amounts. They frequently produced more than one biogenic amine. Klebsiella pneumoniae subsp. pneumoniae and Morganella morganii were the main histamine producers, with mean values of 1,600 and 2,440 mg/liter, respectively, followed by Pantoea spp. 3 (1,710 mg/liter) and Hafnia alvei (2,500 mg/liter). Enterobacter amnigenus and Enterobacter cloacae produced particularly high amounts of putrescine, with mean values of 2,340 and 2,890 mg/liter, respectively. The strongest cadaverine formation was shown by Serratia liquefaciens (3,300 mg/liter), Serratia marcescens (3,280 mg/liter), and Stenotrophomonas maltophilia (1,000 mg/liter).