Flavor Character Of Silver Carp And The Influence Of Heating History On The Silver Carp Flavor

Silver carp is one of main fishes cultivated in fresh water in China, and the degree of processing is very low. Flavor is one of important eating qualities of aquatic product. Before eating, heating history has important influenc on aquatic product processing. Currently, flavor compounds, flavor characteristic of silver carp and the relationship of heating has not been reported yet. This paper took silver carp as the object investigated, and discussed the character flavor and the influence of heating history on flavor of silver carp using gas chromatography- mass Spectrometry (GC-MS), high performance liquid chromatography (HPLC), high resolution (HR) inductively coupled plasma spectrometer (ICP) and taste active value(TAV). This study provided the theory basis for the processing of silver carp products. The main results were as follows:1. Studies on volatile flavor compounds in heated silver carp muscles.The solids phase microextraction (SPME) and the simultaneous distillation extraction(SDE) were employed to discuss volatile flavor compounds in heated silver carp muscles. The optimized conditions of SPME were that a DVB/CAR/PDMS SPME fibres was exposed to the vapor phase above 6g for 40 min at 60℃. 62 volatile compounds were detected under the best extraction condition, and SPME provided better extraction for aldehydes, alcohols and ketones having a lower molecular mass. Ether was used as extraction agent, 2h was the best extraction time for SDE. Under the best extraction condition, 46 volatile compounds in heated silver carp muscles were detected. SDE provided better extraction for aldehydes and esters having a higher molecular mass, while the results of SDE was inverse.The two methods can supplement the analysis of volatile flavor compounds in heated silver carp meat.2. Studies on characteristic flavor compounds in heated silver carp muscles.The characteristic volatile flavor compounds were studied by using gaschromatography-olfactometry. The volatile compounds having greater contribution to entire aroma of heated silver carp muscles as follows: (E,Z)-2,6-nonadienal (cucumber), hexanal (grass scent), 2,4-decadienal (oil flavor), octanal (fat), nonanal (fat), 1-octen-3-ol (earthy smell) and (E)-2-nonenal (earthy). The characteristic taste compounds were studied by using taste active value. The taste compounds having contribution to entire taste of heated silver carp muscles as follows: Gly(sweet), Lys(bitter), His(bitter), IMP(umami), K(salty) and Na (salty). Among them, (E,Z)-2,6-nonadienal, 2,4-decadienal, His and IMP were the characteristic flavor compounds of the heated silver carp muscles.3. Studies on the influence of heating history of heating, reheating and heating during cold storage on flavor of muscles of silver carp.The violate compounds of raw and heated silver carp muscles such as aldehydes, alcoholds, ketones and hydrocarbons reduced with expansion of cold storage time, while the TMA content increased. The taste intensity of Glu, Hx, Val, Met, and Lie increased, however, the umami of IMP reduced. Raw silver carp muscles could produce a large quantity of violate compounds including aldehydes, alcohols, ketones and hydrocarbons during heating. TMA content in muscles of silver carp reduced when heating. The contribution to taste by Ala, His, IMP, K, Na and Ca lowered.Reheating may lead to great reduction in violate compounds including aldehydes, alcohols, ketones and hydrocarbons, but the TMA content had minor variation. When reheating, the reduction of contribution to taste by IMP was significant. Heating history of heating, reheating, and heating during cold storage all reduce the entire delicate flavor intensity of silver carp muscles. The heating history had significant effect on the variation of small peptides content in silver carp muscles.4.Studies on the influence of traditional heating (90℃, 100℃, 121℃at high pressure) and microwave heating on flavor of muscles of silver carp.Compare with the traditional heating, the variety of volatile compounds in muscles of silver carp was few, only hydrocarbons and a few of aldehydes and alcohols have high content in microwave heating. The contribution to taste by His and IMP in muscles of silver carp was higher.The microwave heating had the smallest effect on small peptides content in silver carp muscles.In the traditional heating, the main difference of volatile compounds was their content not their variety. The content of most of volatile compounds was higher when heating silver carp muscles at 100℃(normal pressure), followed by at 90℃(normal pressure), and the content was lower at high pressure. TMA in muscles of silver carp was lower when heating at high pressure.The contribution to taste by IMP and entire umami flavor were lower and lower with the increase of temperature in the traditional heating method. In traditional heating, the main small peptides content increased with the increase of temperature.5. Studies on the influence of heating on the difference of flavor in different parts of silver carp.After heating, the main difference of flavor compounds in different parts of silver carp was their content. The content of volatile compounds in the back had lower content. Gly, His, Lys, IMP, K and Na was main taste compounds in the back. The content of hydrocarbons was higher in the head. His, IMP, K and Na were main taste compounds in the head.The content of alcohols was higher in the belly. His, Lys, IMP, K and Na were main taste compounds in the belly. The content of ketones was higher in the tail. Gly, His, Lys, IMP, K and Na were mian taste compounds in the tail. The tail of fresh silver carp had highest TMA content, the back had the higher content, and the head and the belly had the low content. The difference of small peptides content in different parts of silver carp was obvious.6. Studies on the difference of flavor in muscles of silver carp with a body weight of 1.0kg-3.0kg.The difference of TMA content in muscles of silver carp with different weights was not great. Taste of Glu, His, IMP, K and Na and the entire umami flavor were quite different for muscles of silver carp with different weights. The contribution to taste by Glu and His in heated muscles of silver carp was the highest about 2.5 kg body weight. The contribution to taste by Glu, K, Na and the entire umami flavor in heated muscles of silver carp was higher about 1.0 kg body weight. The difference of small peptides content in body weight of silver carp was obvious. The content of aldehydes, alcoholds, ketones and hydrocarbons in muscles of fresh silver carp with a weight of 1.0-2.0 kg reduced with increase in weight. For the weight of 2.0-3.0 kg, the content of volatile compounds had no great variation. The content of aldehydes, alcoholds and ketones increased with the increase in weight after heating muscles of silver carp with different weights.7. The formation mechanism of flavor of silver carp muscles during heating. Flavor compounds were formed from lipids and proteins in raw silver carp muscles under the effects of enzyme and heat, and contributed characteristic flavor of heated silver carp muscles.Volatile compounds such as aldehydes, alcoholds, ketones and hydrocarbons came from fatty acids degradation reaction. Free amino acid and small peptides came from protein and peptides degradation reaction.