3.7. MA content in canned mackerel fillets
Commercial canned mackerel fillets from different producers were purchased from local markets and their MA content was quantified according to our optimized MA-DAN assay. The resulting contents were between 0.89 and 6.44 nmols/g, with a mean of 3.35 nmols/g. At present, data on free MA in canned mackerel fillets are not available, whereas MA in fresh mackerel samples have been estimated only by TBA spectrophotometric test under different conditions. The recently reported contents were in a range 3–20 nmols/g, corresponding to 0.21–14 mg MA/kg [19], [20] and [21]. The MA concentration in the canned samples tested by us in most cases was lower than that estimated by TBA test in fresh samples. Since the assay is carried out in 20 min at pH 2.0, only MA weakly bound to peptides should be hydrolised and added to the original free MA. Therefore, according to the consideration elsewhere reported [18], the calculated content could be presented as “not strongly bound” MA. In conclusion our optimized MA-DAN assay can be proposed as a rapid, simple and reliable alternative method for the estimation of MA content by HPLC-UV technique.