Study On The Odor Formation Mechanism Of Meat In Grass Carp

Grass carp is one of the four largest domestic fish,the output ranked first in freshwater aquaculture.But the unique smell of grass carp also limits its development.This article mainly from the perspective of endogenous enzymes to explore the mechanism of grass carp muscle odor formation.In this study,grass carp muscle as raw material,combined with LOX to explore the mechanism of odor formation.With grass carp fish as raw material,electronic nose is used to identity the volatile compounds in different sizes of grass carp and principal component analysis;and the combination of solid-phase micro extraction and gas chromatography mass spectrometry(SPME)detection of different size of grass carp red meat,belly meat,dorsal meat volatile compounds.Through the detection of electronic nose analysis can better distinguish red meat,belly meat,dorsal meat volatile components in different sizes of grass carp.32,38,34 volatile compounds were detected in big grass carp red meat,belly meat and dorsal meat,respectively;41,34,36 volatile compounds were detected in small grass carp red meat,belly meat and dorsal meat,respectively.The volatile compounds are mostly carbonyl compounds and alcohols,the respective relative contents are above 90%.There were significant differences in the volatile components of different sizes of grass carp.Grass carp as raw materials,electronic nose and solid phase micro-extraction(SPME)combined with gas chromatography – mass spectrometry(GC-MS)to study the effects of slaughter methods on the volatile component.The way of death are killing,removed the gill,cryogenic death and natural death.The way of death can affect the lipoxygenase(LOX)'s activity.The highest activity of LOX is 4500U/ml crude enzyme solution in the killing grass carp red meat.Through the electronic nose detection analysis,four deadly ways of grass carp red meat can be distinguished,but the belly meat and the back meat can not be distinguished.SPME can effectively adsorb volatile components in grass carp,killing slaughter method's red meat,back meat and belly meat were determined respectively 31,18 and 31 kinds of volatile components,carbonyl and alcohol compounds relative content reached 65.32%,76.22% and65.21%;removed the gill slaughter method's red meat,back meat and belly meat were determined respectively 27,27 and 32 kinds of volatile components,carbonyl and alcohol compounds relative content reached 64.98%,79.32%and 90.30%;cryogenic slaughter method's red meat,back meat and belly meat were determined respectively 34,29 and 29 kinds of volatile components,red meat,carbonyl and alcohol compounds relative content reached70.08%,70.56% and 69.24%;natural slaughter method's red meat,back meat,belly meat were determined respectively 26,20 and 21 kinds of volatile components,carbonyl and alcoholcompounds relative content reached 77.71%,75.99% and 71.27%.The slaughter methods had significant effects on the activity of LOX and the volatile components of grass carp.Fatty acids in farmed and wild grass carp red meat,back meat and belly meat were studied by gas chromatography mass spectrometry.The results showed that the farmed and wild grass carp red meat,back meat and belly meat are rich in unsaturated fatty acids.27,19 and 19 kinds of fatty acids were detected in farmed grass carp red meat,back meat and belly meat.26,22 and 22 kinds of fatty acids were detected in wild grass carp red meat,back meat and belly meat.The relative content of DHA(C22:6n3c)and EPA(C20:5)in farmed grass carp red meat,back meat and belly meat was significantly higher than the wild grass carp(P < 0.05).The relative content of ARA(C20:4n6)in wild grass carp red meat and belly meat was significantly higher than the farmed grass carp(P < 0.05),but in farmed grass carp back meat was significantly higher than the wild grass carp(P < 0.05).There was significant difference in the ratio of n-3/n-6 in farmed and wild grass carp muscle(P < 0.05).Unsaturated fatty acid oxidation results show that the product is related to the substrate of the lipoxygenase,different substances produced by different substrates.Grass carp lipoxygenase catalyzed linoleic acid to get more aldehydes,arachidonic acid to get more alcohols,especially 1-octene-3-ol.The content of esters was higher in EPA samples,hydrocarbons are measured in DHA and model fish meat and the hydrocarbon content of fish was decreased after enzyme addition.The purification efficiency of grass carp was 36.9 and the activity increased to11748.56U/ml after ammonium sulfate 20%~40% precipitation and DEAE-Sepharose FF.The studies show that LOX from grass carp is sensitive to heat.Using inoleic acid as the substrate,the optimum reaction temperature is 40 ?,the optimum substrate concentration is10 mmol / L,the optimum pH is 5.0.