RESUMO
The aim of this work was to evaluate the metals content in surface water of Arroyo San Ignacio (San Ignacio stream) and its main tributary, which are located in a priority ecological region of Mexico. For this study, these streams were divided in three sampling zones establishing thirty two sampling sites. Al, As, B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Si and Zn were measured. Some physicochemical parameters were also evaluated. Results indicated significant difference (P≤0.05) in pH, electrical conductivity, total solids, Ca, K, Na, and Mg levels for the three zones but no differences in heavy metals contents were found. Results were compared with Mexican and international standards and showed that seven metals (Al, Fe, Ni, Mn, Cr, Pb and Cd) exceeded drinking water standards. This pollution is mainly due to increased anthropogenic activities in the region and will likely worsen in the future due to unsustainable practice of discharging wastes into the streams.
RESUMO
The aim of this study was to evaluate and compare the percentage content of fatty acids (FA) of 54 rainbow trout fresh and frozen fillets. Frozen fillets were stored at -15ºC for 45 and 90 days. Saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA), omega-6 (n-6) and omega-3 (n-3) fatty acids were determined by gas chromatograph coupled to mass spectrometry. The results indicated that during frozen storage, SFA and MUFA content increased by 32.63 and 9.25%, respectively, while PUFA content decreased by 25.3%, n-6 by 12.4% and n-3 by 32.55%. These changes were more significant (P ≤ 0.05) during the first 45 d of storage. It was concluded that the frozen storage had a negative impact on meat quality of rainbow trout due to the reduction of PUFA, n-3/n-6, polyene index and PUFA/ SFA and the increase of the SFA, and atherogenic and thrombogenic indexes, which meant a substantial loss of nutritional value in the fillets of rainbow trout.