Cheese is a histamine-rich food and may contain biogenic amines formed during ripening process, due to degradation of proteins through proteolysis. Therefore, histamine producing bacteria and biogenic amines content were studied during ripening of ras cheese at refrigeration temperature 4±1oC for 10 weeks using HPLC. Three batches of Ras cheese were manufactured using Egyptian conventional method. From each batch, samples collected at zero, 2, 4, 6, 8 and 10 weeks after cheese manufacture. The obtained results revealed that Enterobacteriaceae and Enterococci had the same pattern during ripening of ras cheese with a significant decrease from (5.0x108±7.02x106 at zero day until reach 4.60x10±0.24x10 cfu/g at week 10 of storage), (from 3.46x105±3.17x104 at day zero until reach to 2.20x10±0.23x10 cfu/g at week 10 of storage), respectively. Lactobacilli count showed fluctuation during ripening period where the highest count recorded at 2nd and 10th week 4.40x105±0.25x105 and 4.40x105±0.15x105 cfu/g, respectively. Enterobacteriaceae, enterococci and lactobacilli producing histamine were identified. Investigated biogenic amines (Cadaverine, Histamine and Tyramine) significantly decrease during ripening of ras cheese while, Putrescine showing fluctuation during ripening. Therefore, to protect consumers from biogenic amines poisoning, factors that enhance biogenic amines formation during cheese processing should be controlled.
Key words: Ras cheese, histamine- producing bacteria, biogenic amines, HPLC
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