TEXTURAL DETERIORATION OF RED HAKE AND HADDOCK MUSCLE IN FROZEN STORAGE AS RELATED TO CHEMICAL PARAMETERS AND CHANGES IN THE MYOFIBRILLAR PROTEINS

摘要

ABSTRACTThe present study involved the measurement of fish muscle texture by both objective and subjective means. Reliable methods for the evaluation of fish texture as well as interpretation of results are discussed. The study demonstrated that significant correlations between the methods could be achieved if carefully controlled conditions were maintained. The presence of dimethylamine in frozen hake (Urophycis chuss) appeared to be a good chemical indicator of toughness whereas the extractable protein nitrogen was not as reliable. Data suggest that although the enzymatic formation of formaldehyde was a major factor in the toughening of red hake, other factors probably contribute to the textural deterioration observed during cold storage. It is evident that haddock (Melunogrammus aeglefinus) toughens when stored at relatively high temperatures (‐5°C) and like hake, experiences a loss of water‐holding capacity although no formaldehyde accumulates in the tissues. The molecular basis of toughening in fish was examined by SDS gel electrophoresis. Apparently, the formaldehyde produced by the TMAO‐ase enzyme system in red hake resulted in the covalent cross linking of troponin and myosin light chains, forming higher molecular weight aggregates. Changes at the molecular level were not detected by this method in haddock. Textural changes in this species are not as pronounced as those of hake and are most likely due to secondary bonds such as hydrogen or electro