Study On Taste Components And Quality Variation Of Grass Carp Meat

Grass crap is farmed specie of freshwater aquaculture in China for its largest production,and it is important economic fish species in China.However grass crap's meat extremely perishable,which lead to low utilization rate.The objective of the present study is to thorough analysis about the effect of season,seasons;slaughter methods;freezing methods;storage temperature on the different parts of grass crap.The results were shown as follows:The seasonal variation of basic nutrients and tast compounds in grass crap were explored.Choose the belly meat,dorsal meat,and red meat of grass crap as the object.The contents of free amino acids and flavored nucleotides in different sason of grass carp were determined and compared by high performance liquid chromatography(HPLC),and the contents of basic nutrients(water,ash,crude protein,crude fat)and lactic acid in different part of fish meat were also determined.The results showed that grass carp's contains 70~80% water,0.7~1.6% ash,and crude protein content is 11~25%,and there is a big difference in crude fat in grass carp.There is rich in crude fat and low in water and crude protein in the red meat of grass crap.The content of ash have no seasonal difference in the dorsal meat of grass carp.At spring,grass crap has abundant content of water,and the content of crude protein is the lowest.The content of crude fat is haighest in autumn's fish.The content of tasty amino acid in the spring,winter,autumn,summer is reduced in turn.The content of IMP is the highest in the spring,however is the lowest in summer.The content of lactic acid is the highest in grass carp.Therefore,the season have some influence on the basic nutrients and taste compoundsThe effect of different slaughter methods on the physical characteristics and taste of grass carp were studied.The contents of free amino acids and nucleotides compounds in the dorsal meat and red meat of Grass Carp killed by different methods,which are natural,bleeding by cut off the gill,percussive stunning,were determined and compared by high performance liquid chromatography(HPLC),and the p H value,water-holding capacity(WHC),texture were also determined.The results showed that the p H and WHC of the dorsal meat are higher than the red meat.The p H and WHC of bleeding is the highest,and the bleeding have best of hardness and chewiness,the natural is the lowest.The content of free amino acids in dorsal meat is higher than the red.The content of sweet amino acid in natural,bleeding by cut off the gill,percussive stunning,is reduced in turn.In the natural,the content of IMP and AMP is lowest,the content of Hx and Hx R are highest,which lead to the K value is highest,the K value of dorsal and red meat is 29.18?66.18% respectively in natural.The dorsal meat and red meat of grass carp killed by three different methods were distinguished effectively with electronic tongue.To investigate the effect of freezing methods on the content of flavor substances of grass carp.The contents of water soluble components in the belly meat,dorsal meat and red meat of Grass Carp frozen by different methods,which are quick-frozen,-20 ? liquid alcohol freezing,-20 ? static air freezing,were determined and compared by high performance liquid chromatography(HPLC),acid auto-analyzer and electronic tongue,and the contents of lactic in fish meat were also determined.The freezing methods had influence on fish freshness and the water soluble components contents.There are positive correlation between the contents of IMP and AMP,total free amino acids and freezing-rate,however,the contents of Hx R and Hx negatively correlated with the freezing-rate.After 3 days storage under-20?,the K value of quick-frozen was the lowest,and the maximum K value was-20 ? static air freezing.The contents of IMP and AMP in red meat were lowest,while Hx R and Hx contents more than other two parts of grass carp,it lead to the taste and freshness of red meat were poor,the K value of three freezing methods were 28.99%,40.92%,46.58% in the red meat respectively.The contents of free amino acids in belly meat were similar with dorsal meat,which was higher than the red meat,it's noteworthy that asparagic acid and glutamate contents in red meat was significantly higher than belly meat and dorsal meat,besides the content of lactic in red meat was higher than belly and dorsal.So the influence of freezing method on freshness of red meat was higher than belly meat and dorsal meat in Grass Carp.The belly meat,dorsal meat and red meat of grass carp frozen by three different methods were distinguished effectively with electronic tongue.The quality changes of grass carp in different storage temperatures were investigated.Choose the dorsal meat,and red meat of grass crap as the object.We determine the total colony counts,TVB-N,the total of sulfydryl,the activity of Ca2+-ATPase,the content of lactic in the grass carp stored at-3? and-20?,and the contents of free amino acids and flavored nucleotides were determined and compared by high performance liquid chromatography(HPLC).The results showed that the quality of grass carp deteriorates with the extension of storage time in the low temperature storage.The increase rate of the total colony counts and TVB-N in-3?,is higher than that in-20?,The decline rate of the total of sulfydryl,the activity of Ca2+-ATPase in-3?,is faster than-20?.Meanwhile,the decline rate of the content of taste compounds in-3?,is faster than-20?.To sum up,grass carp have best taste and highest nutritional value in the spring and winter.In the process,we should choose rapid stunning method which not only can minimize the stress response to fish,but also can avoid fish blood into muscle,use the fastest freeze rate of freezing method to fish,adopt freezing storage at low temperature to ensure the best taste and quality of grass carp.