Correlations between texture and oxidation during ripening of old fashion salted herrings
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (LMC/Food - P1)
Keywords: oxidation
Herrings are fatty fish, which are very susceptible to oxidation. During the production of old fashioned salted herring, fish are stored for up to 12 months in brine to ripe. The brine contains a high level of salt and haemoglobin, which is a strong prooxidant in fish muscle and is believed to induce protein cross-linking. Therefore the role of haemoglobin in the development of the characteristic texture of salted herrings during ripening deserved further attention.
The changes in texture during ripening of salted herring was investigated mechanically after optimization of the Warner-Bratzler shear test (WB) and the texture profile analyzer (TPA). In addition, the rate of free radicals formation in the fish muscle was evaluated using electron spin resonance spectroscopy (ESR). Fresh and salted herring samples (2, 85, 151 and 371 days of ripening) were filleted and sampled for mechanical testing and ESR. Two ripening conditions were evaluated, normal salting conditions and conditions where extra blood was added to the brine during the production. The TPA was able to reveal differences in texture in salted herrings during ripening. An increase in hardness after 2 days ripening and a significant decrease in the hardness after 371 days were observed in the fish muscle. The WB shear test was also able to confirm these results but interpretation of the obtained data was more difficult. The ESR results indicated that more radicals were present in the fish samples processed with extra blood brine.
Based on the obtained data we postulate that oxidative reactions inducing protein cross-linking is responsible for the characteristic texture of salted herring. It is yet to be confirmed if haemoglobin is the main actor in these oxidative reactions.
