Study On Influence Factors Of The Odor Change Of Grass Carp Meat

In order to investigate the influence factors of odor change of grass carp meat,the volatile components of different parts of grass carp were studied,and the effects of slaughter methods,freezing methods and low temperature storage on the volatile components of grass carp meat were studied.The aim is to provide theoretical reference for the processing,storage and quality management of grass carp,and to promote the development of the grass carp breeding industry.In this study,a new type of material(MonoTrap)was applied as solid phase extraction to extract the volatile compounds of different parts of grass carp.The volatile flavor components of dorsal meat,red meat,gills,skin and intestine were analyzed and identified by gas chromatography-mass spectrometry(GC-MS).The results of GC-MS analysis demonstated that there are 45,49,56,62 and 62 volatile compounds in dorsal meat,red meat,gills,skin and intestine respectively,and aldehydes,ketones,alcohols and hydrocarbons have important contribution to the flavor formation of grass carp.The most species and the highest relative content of aldehydes and ketones of grass carp are the gills,the most kinds of alcohols are red meat,the highest relative content is dorsal meat,and the most kind and the highest relative content of hydrocarbons are the dorsal meat.Pentanal,hexanal,heptanal,octanal,2-octenal,nonanal,2,6-nonadienal,2-nonenal,decanal,2-decenal,undecanal,2,4-decenad-ial,dodecanal,1-penten-3-one,heptanol,1-octen-3-ol,xylene are the key flavor compounds in different parts of grass carp,aldehydes and alcohols have main contribute to the overall odor of grass crap.In order to investigate the effect of slaughter methods on the volatile flavor of grass carp meat,four different slaughter methods,namely the cryogenic temperature,knocking on head,gill removal and asphyxial death,were used to pretreat live grass carp.In this study,a new type of material(MonoTrap)was applied as solid phase extraction to extract the volatile compounds of dorsal meat and red meat.Thevolatile flavor components of dorsal meat and red meat of different slaughter methods were analyzed and identified by electronic nose and gas chromatography-mass spectrometry(GC-MS).The experimental results indicated that the odor of dorsal meat and red meat of different slaughter methods could be discriminated by electronic nose.the difference of odor components between cryogenic temperature death and asphyxial death is maximum.The results of GC-MS analysis demonstated that there are 33,39,47 and 51 volatile compounds in cryogenic temperature,knocking on head,gill removal and asphyxial death dorsal meat respectively,and 34,39,50 and 52 volatile compounds were detected in red meat respectively,aldehydes,alcohols and hydrocarbons have important contribution to the flavor formation of grass carp.Researches manifest that the cryogenic temperature death of four different slaughter methods have the lowest level of stress,it show the minimum influence on the volatile constituents of grass carp meat,the flavor is the best.the flavor of grass carp meat by knocking on head death is the second.The asphyxial death show the greatest influence on the volatile constituents of grass carp meat,the flavor is the worst.In order to investigate the effect of freezing methods on the volatile flavor of grass carp meat,three different freezing methods,namely the quick-freezing,ethanol immersion freezing and ordinary refrigerator freezing,were used to pretreat the fresh dorsal meat and red meat.In this study,a new type of material(MonoTrap)was applied as solid phase extraction to extract the volatile compounds of dorsal meat and red meat.The volatile flavor components of dorsal meat and red meat of different freezing methods were analyzed and identified by electronic nose and gas chromatography-mass spectrometry(GC-MS).The experimental results indicated that the freezing rate of quick-freezing was the fastest,which exhibited 6.65 times higher than that of ethanol immersion freezing,and 16.97 times higher than that of ordinary refrigerator freezing.The odor of fresh grass carp meat and freezing grass carp meat could be well discriminated by electronic nose.Principal component analysis(PCA)showed that the differences of odor components between ordinary refrigerator freezing and fresh meat is maximum.The results of GC-MS analysis demonstated that there are 45,33,28 and 22 volatile compounds in fresh,quick-freezing,ethanol immersion freezing and ordinary refrigerator freezing dorsal meat respectively,and 49,38,33 and 25 volatile compounds were detected in fresh,quick-freezing,ethanol immersion freezing and ordinary refrigerator freezing red meat respectively,the mainingredient of volatile compounds were aldehydes and alcohols.Researches manifest that the compounds such as pentanal,hexanal,heptanal,octanal,2-octenal,nonanal,2-nonenal,decanal,2-decenal,undecanal,2,4-decadienal,hexanol,2-octen-1-ol,1-octen-3-ol,xylene had an important contribution to the overall flavor formation of grass carp meat.Compared with the type and content of volatile components in fresh meat,the quick-freezing meat was closest to fresh meat,and ordinary refrigerator freezing meat were most different to fresh meat.The quick-freezing was more beneficial to maintain the quality of the freezing grass carp meat,so that the flavor of frozen grass fish close to fresh fish.In order to investigate the change of volatile components and quality of grass carpmeat during storage 4?,a number of parameters were examined,including total volatile basic nitrogen(TVB-N)value,2-thiobarbituricacid(TBA)value,pH value and the total number of bacterial colonies,the volatile flavor components of grass crap during storage 4? were analyzed and identified by monolithic material sorptive extraction-gas chromatography-mass spectrometry(MMSE-GC-MS).The experimental results indicated that TVB-N value,TBA value and the total number of bacterial colonies increased with the extension of storage time while pH value increased after an initial decrease,when the storage time is 7d,the pH value is the lowest.The results of GC-MS analysis demonstated that there are 34,36,36,41,44 and46 volatile compounds in 0d?2d?4d?5d?6d?7d and 8d meat respectively.At the initial period of storage,the main ingredient of volatile compounds were aldehydes,alcohols and hydrocarbons,at later storage period,the main ingredient of volatile compounds were aldehydes,alcohols,acids and estersand.hexanal,heptanal,nonanal,decanal,undecanal,2,4-decenadial,dodecanal,2-heptanol,heptanol,1-octen-3-ol,p-xylene are the key flavor compounds in grass carp during storage 4?,aldehydes and alcohols have main contribute to the overall odor of grass crap.The result show that the shelf life of grass crap stored at 4? is 7 days,then the fish is corrupted and can not be eaten again.