| As a healthy substitute for meat products,textured soy protein(TSP)can not only meet people’s nutritional needs,but also save resources and protect the environment,so TSP has a broad market prospect.However,the existing research on the flavor of TSP mainly focuses on the identification of volatile compounds,lack the understanding of its beany compounds.In this paper,headspace solid phase microextraction combined with gas chromatography-olfactory mass spectrometry(HS-SPME-GC-O-MS)and the odor activity value(OAV)were used to determine the beany compounds of TSP,and the effects of alcohol method soybean protein concentrate(ALSPC)raw materials and enzymatic hydrolysis on the beany compounds and sensory quality of TSP were studied,the effect of heat treatment on the interaction between soy protein isolate and flavor compounds was explored.The specific research content and results are as follows:(1)With total peak area and peak number of volatile compounds as indicators,the optimal conditions for headspace solid phase microextraction were as follows:DVB/CAR/PDMS extraction head,equilibrium temperature of 70℃,equilibrium time of 30min,adsorption time of 30 min.168 volatile compounds were identified in the four TSP,the highest content of which was heterocyclic(26.40-82.25%),followed by alkanes(3.25-41.74%),aldehydes(4.48-11.17%),ketones(5.62-9.84%),acids(0-7.75%),alcohols(0.43-5.54%)and esters(1.78-5.48%).A total of 13 amoma-active compounds was identified GC-O,of which 11 aroma-active compounds were identified as the compounds of beany compounds.The beany compounds were accurately quantified by external standard method,and combined with their threshold value,the odor activity value(OAV)was obtained.The key beany compounds common to the four kinds of TSP were:n-hexenal,nonanal and 2-pentylfuran.(2)The differences in the content of beany compounds and quality characteristics of Low Moisture Textured Vegetable Proteins(LMTSP)produced from different SPC raw materials were compared.ALSPC was beneficial for reducing the beany compounds of TSP(the volatile compounds content and beany compounds content of TSP produced from ALSPC were 7629.36-9197.15μg/kg and 6218.57-7610.01μg/kg,respectively,which were significantly lower than the volatile compounds content and beany compounds content of TSP produced from the acid method of SPC),which may be related to the low crude fat content of ALSPC.However,the functional characteristics(the water and oil holding capacity)of ALSPC were worse than that of acid method SPC.The TSP produced from ALSPC had a low degree of expansibility and a low tissue status score.(3)The effects of enzymatic hydrolysis with flavor protease and alkaline protease on beany compounds,quality characteristics,chemical bond cross-linking and secondary structure of TSP were studied and investigated.Enzymatic hydrolysis decreased the relative concentration of alcohols,aldehydes,and ketones in SPC,significantly reduced the total amount of beany compounds and the content of hexanal(the total amount of beany flavor components decreased from 20777.46μg/kg to 7493.53μg/kg and 5277.01μg/kg,respectively,while the content of n-hexanal decreased from 427.70μg/kg to 206.76μg/kg and 222.36μg/kg,respectively),and the beany taste of TSP was significantly reduced.Enzymatic hydrolysis of protein raw materials with flavor protease and alkaline protease promoted the conversion of hydrogen bond-disulfide bond interactions in TSP to hydrophobic interaction-hydrogen bond-disulfide bond interactions,and promoted the conversion ofα-helical toβ-turn structure,and the hardness and chewiness of the products increased and then decreased.In addition,with the increase of flavor protease addition,the oil holding capacity of products showed a decreasing trend,the water holding capacity and rehydration capacity of products were firstly increased and then decreased,and the brightness value L~*of TSP increased.With the increase of the amount of alkaline protease addition,the water and oil holding capacity of the product decreased,and the quality of the product decreased.When the addition amount of flavor protease and alkaline protease was0.2%,the sensory quality of TSP was the best.(4)The effects of different protein concentrations,heat treatment time,and heat treatment temperature on the binding of soybean protein isolate(SPI)to beany compounds were investigated,and the effects of heat treatment on the binding parameters of SPI with n-hexanal were determined.When the concentration of SPI increased from 1%to 3%,the binding percentages of n-hexanal,benzaldehyde,and n-hexanol with protein increased.The binding percentage of SPI with n-hexanal increased first and then decreased with the increase of heat treatment temperature,and the highest binding rate was 47.65%at the heat treatment temperature of 80°C.The binding percentage of SPI with n-hexanol and benzaldehyde showed an opposite trend with increasing heating temperature.When the heat treatment temperature was raised to 100℃,the binding percentage of n-hexanol with SPI increased by 22.10%,while for benzaldehyde,the increase in temperature increased the activity coefficient of flavor substances,resulting in a decrease in the binding percentage of SPI with benzaldehyde.The binding percentages of SPI with n-hexanal and hexanol increased first and then decreased with the prolongation of heat treatment time.When the heat treatment time was 5 minutes,the binding percentage of protein with hexanal was the highest.When the heat treatment time was 15 minutes,the binding percentage of protein to hexanal and hexanol was the highest.The binding percentage of benzaldehyde with protein decreased with the prolongation of heat treatment time.Heating can change the conformation and aggregation state of proteins,resulting in changes in the binding percentage of proteins with flavor compounds.Before and after heat treatment,the binding sites of hexanal and L-SPI decreased from 2.46 to 1.46,the binding constants decreased from 488.23 L/mol to 144.88 L/mol,and the n K decreased from 1198.99 L/mol to 211.33L/mol,further indicating that heat treatment reduced the binding ability of SPI to n-hexanal.The study of this topic found that there were 11 beany compounds in TSP,ALSPC and enzymatic hydrolysis had an impact on the beany compounds and quality characteristics of TSP.The TSP produced from ALSPC had light flavor,low beany flavor,and good color,but its expansibility degree was poor,and its organization was not sufficient.Excessive addition of protease gradually weakened the beany taste,but the apparent and histological morphology of the product deteriorated,resulting in a lower sensory score.Within a suitable addition range,it effectively removed the beany compounds of tissue proteins,while improving the quality characteristics of the product.Heat treatment reduced the binding ability of soybean protein with hexanal,thereby achieving the goal of controlling and removing the beany flavor of TSP.It is of great significance to optimize the extrusion process and enhance the flavor properties of products. |
