Analysis And Evaluation Of Flavour In Chinese Soft-shelled Turtle (Trionyx Sinensis) Edible Parts

Evaluation of flavour value is fundamental to understanding of foods.Food flavor value is the study of the chemical nature of food flavor components and the ways and means of their formation.Flavour includes aroma and relish.Aroma usually means volatile components of food.Relish means non volatile flavor components.Chinese soft-shelled turtle is a kind of characteristic food in china,and is beneficial to our health,whose whole body is a treasure,and the various parts of the body could be used as medicine,which is traditional diet therapy tonic in China.In this paper,volatile components of muscle(legs and carina)of Trionyx sinensis under steaming and boiling were investigated and quality evaluated.In addition,the difference of volatile components from edible parts of muscle(legs and carina)of Trionyx sinensis under boiling before and after de-fishy were analyzed.Finally,relish components of muscle(legs and carina)of Trionyx sinensis under steaming and boiling before and after de-fishy were researched.The main research results are described as follows.In terms of volatile components of muscle(legs and carina)of Trionyx sinensis under steaming and boiling,the more volatile components in the edible parts of the prepared Chinese soft shelled turtle were aldehydes,alkanes and aromatic compounds in orders.The amounts of aldehydes in muscle(legs)of Trionyx sinensis are more than those in muscle(carina)of Trionyx sinensis,and the amounts of aldehydes increased more obviously than other volatile components in muscle(legs)of Trionyx sinensis.Octadecanal,2-undecenal,(E)-2-octenal were all found in muscle(legs and carina)of Trionyx sinensis under steaming and boiling,which were characteristic different volatile components in the edible parts of the prepared Chinese soft shelled turtle.Nonanal,decanal were all found in muscle(legs and carina)of Trionyx sinensis,which was raw & cooked by steaming & boiling.Among them,nonanal is considered commonly found in freshwater fish,with a rose,citrus aroma.(E)-2-octenal single aldehyde compounds was characteristic different volatile components in the edible parts of the prepared Chinese soft shelled turtle,which was low threshold,fruity,sweet and clear fat aroma.The threshold of 2-pentyl furan is relatively low,which is about 4*10-9 g/kg,with a barbecue flavor.It was reported in many documents that it had analogous meat ham flavor.It has great influence on meat flavor for 2-pentyl furan,which can be used as indicators of meat lipid oxidation.It was found in all prepared muscle(legs)of Chinese soft shelled turtle,which is the characteristic flavor of prepared muscle(legs)of Chinese soft shelled turtle and has great contribution to the flavour of prepared muscle(legs)of Chinese soft shelled turtle.2,6,10,14-tetramethyl-pentadecane was only found in prepared muscle(legs)of Chinese soft shelled turtle,which was formed by oxidation of lipid of alkyl free radicals or by the breakdown of carotenoids.It was distinctive volatile compounds compared with fresh muscle(legs)of Chinese soft shelled turtle,with fresh and sweet smell.1-octene-3-alcohol was produced by hydrogen peroxide degradation of linoleic acid,like mushroom odor,which was related to volatile aroma substances in fresh water fish.It was widespread in volatile aroma substances of fresh water fish and sea fish,only found in prepared muscle(legs)of Chinese soft shelled turtle,and it is why prepared muscle(legs)of Chinese soft shelled turtle has popular flavour characteristics.The quality and quantity of volatile compounds of muscle(legs and carina)of Trionyx sinensis: boiling > steaming > fresh.It shows that: It is more beneficial for volatile compounds of muscle(legs and carina)of Trionyx sinensis to escape by boiling than by steaming.It is easier for peculiar odor to abate and volatile aroma compounds to volatilize after cooked.It’s better to cook the muscle(legs and carina)of Trionyx sinensis by boiling.Most of the volatile components in the soup were from edible parts of Trionyx sinensis.There is more contribution for muscle(legs)of Trionyx sinensis to volatile compounds.Some substances whose content is very low had no resources.Chemical reaction of muscle(legs and carina)of Trionyx sinensis in the water environment may be the cause of it.Volatile components of muscle(legs and carina)of Trionyx sinensis by boiling before and after de-fishy were analyzed and compared,concluding that the effect of de-fishy by bile smearing is obvious.After de-fishy by bile smearing,kinds of volatile compounds muscle(legs)of Trionyx sinensis which is raw & cooked by boiling increased significantly,especially aromatic compounds.And kinds of volatile compounds muscle(carina)of Trionyx sinensis decreased significantly,especially aldehydes.The main volatile components of muscle(legs and carina)and soup of Trionyx sinensis by boiling were aromatic compounds,alkanes and aldehydes,respectively.Type and quantity of volatile components changed significantly.Stimulating 1-tetradecanol was only found in raw carina and disappeared after de-fishy.The same as(E,E)-2,4-decadienal which was lower threshold with oil flavor and was only found in carina of Trionyx sinensis by boiling before de-fishy.These substances were all remarkable which indicated that de-fishy by bile smearing was effective.And the sensory experiment showed that the de-fishy effect is remarkable.Relish components of muscle(legs and carina)of Trionyx sinensis under steaming and boiling before and after de-fishy were studied: The content of NPN in the muscle(legs)of Trionyx sinensis did not increase by heating.The way of boiling leads to the loss of nitrogenous substances in the muscle(legs)of Trionyx sinensis.The content of NPN in the muscle(carina)of Trionyx sinensis increased by heating.And the way of heating is conducive to nitrogen dissolution.It had no significant difference between steaming and boiling.The way of heating promoted the dissolution of umami nucleotides to a certain extent.The way of boiling led to a little part of umami nucleotides dissolving in the soup.Effects of heating modes on umami amino acids were not significant,promoting the umami amino acid dissolution to a certain extent.But heating modes could decrease the content of bitter taste amino acids significantly.Among them,valine decreased significantly after heating,histidine couldn’t be detected after heating.The bitter amino acids tyrosine and methionine couldn’t be found in the muscle(legs)of Trionyx sinensis.The same as arginine,methionine and isoleucine which were undetectable in the muscle(carina)of Trionyx sinensis after cooked.The contents of umami amino acids increased significantly after de-fishy.They were glutamic acid and aspartic acid in order.And the change trend agreed with nucleotide.However,the contents of bitter amino acid decreased.A little part of umami amino acids dissolved in the soup by boiling.It had no significant difference compared with steaming method.Valine decreased significantly after cooked and de-fishy.Histidine couldn’t be found after cooked and de-fishy.Tyrosine and methionine couldn’t be detected before and after cooked and de-fishy in muscle(legs)of Trionyx sinensis.