Contribution of lipid oxidation to bitterness and loss of free amino acidsin the autolytic extract from fish wastes: Effective utilization of fish wastes

The reason why bitterness of the autolytic extract is enhanced by shaking d uring autolysis was investigated from the viewpoint of improving the taste of the extract from fish wastes. Two kinds of extract were prepared from th e head-viscera mixture of frigate mackerel after autolysis with (S1) and wi thout shaking (S2). A comparison of the two extracts showed significant dif ferences in their organoleptic and chemical properties. More brown in color , S1 tasted much more bitter than S2, while S1 gave lower contents of free amino acids, higher thiobarbiturate (TBA) values and a smaller ratio of pol yunsaturated fatty acids to the total ones. This indicates that lipid oxida tion occurred more vigorously in S1 than in S2. Furthermore, it was found t hat the increase in the bitterness and in the loss of free amino acids was correlated with the increase in TBA values of the extract. In conclusion, l ipid oxidation accelerated by shaking during autolysis contributed to the e nhanced bitterness and brown discoloration and to the loss of free amino ac ids of the autolytic extract from fish wastes.