Abstract:

The contents of nucleotide compounds and free amino acids in the dorsal meat of grass carp slaughtered by
different methods, that is, natural death, emergency slaughter and gill removal, were determined and compared by high
performance liquid chromatography (HPLC) and amino acid auto-analyzer. Besides, pH and the contents of glycogen and
lactic acid in fish dorsal meat were also determined. The results showed that the percentage of bitter amino acids accounting
for the total amount of free amino acids in the dorsal meat of grass carp subjected to the above three slaughter methods
were 78.95%, 68.60% and 69.44%, respectively, and K values as a freshness index for fish meat were 20.28%, 15.49% and
12.13%, respectively. Dorsal meat samples from naturally dead grass carp exhibited the lowest contents of ATP and IMP
and worst freshness. The changes in pH and lactic acid content were negatively correlated with each other along with the
changes in lactic acid and glycogen contents in the dorsal meat of grass carp, regardless of the slaughter methods used. The
dorsal meat of naturally dead fish had the highest lactic acid content and lowest pH value. Different slaughter methods had a
large effect on water-soluble flavor components in grass carp meat. The taste of naturally dead grass fish was the worst and
the taste difference between two other slaughter groups was not obvious. Thus, during slaughter and processing of fish the
blood should be prevented from infiltrating into the muscle in order to avoid the generation of off-flavor.

Key words: grass carp, slaughter methods, free amino acids, ATP related compounds, lactic acid