Relationship between putrescine and histamine contents with the populations of aerobic mesophilic and psychrotrophic bacteria in rainbow trout (Oncorhynchus mykiss) in Shiraz market

Biogenic amines are small organic molecules with an aromatic and hydrocyclic structure. These compounds are formed duo to the decarboxylation of foods’ free amino acids by microbial enzymes. The aim of present study was to investigate the possibility of using putrescine and histamine contents as an indicator to assess the freshness of rainbow trout (Oncorhynchus mykiss). Therefore, using HPLC the concentrations of putrescine and histamine was determined in cold-stored rainbow trout samples. The samples were analysed every 3 days from day 0 to 18. Based on results, histamine was not detected at the first and third days of the storage, however putrescine was estimated at 1.30±0.03 µg/g. Initial concentrations of histamine and putrescine were 0.7 and 1.2 µg/g respectively. Theses parameters reached to 13.5 and 18 mg/g at the end of 18 days of storage which was statistically significant (p<0.05). Moreover, a direct and significant relationship was observed between the load of aerobic mesophilic bacteria and histamine contents in the fish samples. Similar relation (p<0.05) was found between the load of psychrotrophic bacteria and putrescine content. Consequently, histamine and putrescine concentrations could be used as an indicator to assess the freshness of rainbow trout.