Frozen herring as raw material for spice-salting

One batch of herring (Clupea harengus) was spice-salted fresh and as thawed after 32 days of frozen storage at -24 degrees C. After salting, samples o f both groups were sent to participating laboratories in Iceland, Denmark, Norway, Germany and England. The herring was kept at 5 +/- 1 degrees C and sampled three times during a 26 week storage period. The development of tas te and texture characteristics (determined by sensory evaluation and instru mental texture measurements), formation of low-molecular-weight nitrogen co mpounds and changes in proteolytic activity were followed in both groups. T he sensory evaluation results showed that thawed salted herring ripened in a similar manner to herring salted fresh, but at a faster rate. Instrumenta l texture analysis showed a faster rate of tenderising in thawed salted her ring, Proteolytic activity measured as general activity and with specific s ynthetic substrates was higher in the thawed salted herring. The formation of trichloroacetic acid-soluble nitrogen and free amino acids was faster in the previously frozen herring. The results show an accelerated but similar rate of ripening in thawed spice-salted herring in comparison with fresh s alted herring. (C) 2000 Society of Chemical Industry.