Low field NMR T2 transverse relaxation measurements were performed on muscle samples from sixty hake (Merluccius merluccius, L.). Fish fillets from hake stored in ice for 3 and 14 days were subjected to different freezing methods (air blast, liquid nitrogen or walk-in freezer) and storage conditions (-20 and -10°C for 5 days, 8 and 18 weeks). Distribution analysis of T2 data of unfrozen muscle displayed a major band (T21), accounting for 90-92% of the total signal, with a relaxation time centred at 47-60 ms and a broad band with protons of higher mobility between 300 and 800 ms, accounting for 3-5% of the signal. Upon freezing, T21 became wider and an extra band appeared within the range 120-360 ms. Whereas no changes were detected at -20°C, the T21 time constant decreased during frozen storage at -10°C in a similar way for all three freezing methods. The relative abundance of T21 declined with storage time but differences were found as a function of freezing. Results are discussed in the light of morphological alterations and protein denaturation, and it is concluded that LF NMR relaxometry is sensitive to different freezing and frozen storage conditions which can have important implications for the quality of fish muscle.

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a b s t r a c tThe antioxidant effectiveness of caffeic acid addition to minced fish muscle with or without wheat dietary fibre added was studied. Wheat dietary fibre showed a significant prooxidant effect on minced fish muscle during chilled storage that was significantly inhibited in presence of 100 mg/kg caffeic acid. In samples containing caffeic acid and wheat dietary fibre, lipid oxidation was completely inhibited after 10 days. Results obtained from the instrumental texture profile analysis showed that the inclusion of wheat dietary fibre with or without caffeic acid lowered the texture profile analysis parameters. Caffeic acid did not render any changes on the water binding capacity. These results prove that caffeic acid can be successfully used as a natural antioxidant in wheat dietary fibre minced fish restructured products.

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