| Surimi products are popular with consumers with high-protein,low-fat and tender taste,hence its yield increases year by year.Transglutaminase(TGase)has been widely applied to improve the properties of surimi gels since TGase can significantly enhance surimi gel strength due to the cross-linking between lysine and glutamine.However,the textural properties of surimi gel will transfer from elastico-viscous body to elastico-crip body if the surimi is set with TGase at low temperature for a long time.Its flavor will obviously change,too.The jump point of texture,the law of organization evolution and the effect of gel structure on flavor release of TGase induced surimi gels are not clear.In this study,the evolution law of the structural parameters such as the mechanical properties,micro network structure,cross-linking density,the diffusion kinetics of several taste substances(Na Cl,sucrose,sodium glutamate)and the relationship between the structural evolution and release of the flavor were investigated when the surimi was set at different temperatures(40℃,25℃,4℃)with the setting time prolonged.The main results were as follows:1.The effects of setting time on the mechanical properties of TGase-induced surimi gels at different temperature were studied.The breaking force,hardness and chewiness of surimi gels increased significantly(p<0.05)along with the setting time.The lower the setting temperature was,the longer the time was required to achieve the maximum mechanical properties.At 40℃,the breaking force achieved equilibrium(1100g)when setting for 3-6h and the highest deformation(17mm)was obtained in control group when setting for 1-2h,then decreased with the setting time extending.The breaking force of MTGase group reached up to the highest value(1268g)when setting for 3h(p<0.05).The hardness and chewiness achieved equilibrium when setting time was extended up to 3h,while the deformation decreased significantly(p<0.05)with the setting time prolonged.At 25℃,the breaking force of control group and MTGase group reached up to the highest value at 24h(831g,1518g)respectively.At 4 ℃,the highest breaking force was respectively obtained at 6h(495g)and 48h(1040g).2.The effects of setting time on the structure properties of TGase-induced surimi gels at different temperatures were investigated.The pore size of surimi gels decreased firstly and then increased significantly(p<0.05)along with the setting time.At 40℃,the lowest pore size of the surimi gels was obtained respectively when setting for 3h.The pore sizes of control group and MTGase group were 1.34μm and 1.31μm respectively.At25℃,the lowest pore size of the surimi gels was obtained when setting for 12 h and 4h.At4℃,the pore size of the control group reached the lowest value when setting for 6h.However,the pore size of the MTGase group decreased significantly along with the setting time and reached the lowest value when setting for 48 h.The cross-linking density of MTGase group was higher than that of the control group(p<0.05)along with the setting time.The results of free amino groups showed that at 40℃ and 25℃,the cross-linking density both increased with the setting time prolonged(p<0.05),and reached the highest value at 6h and 24 h respectively.At 4℃,the cross-linking density increased firstly and then decreased significantly(p<0.05).The control group reached the highest value at 12 h while the MTGase group can reach at 6h.3.The effects of setting time on the water holding capacity and water distribution of TGase-induced surimi gels at different temperatures were studied.At 40 ℃,the expressible moisture content significantly increased when the setting time was longer than2h(p<0.05).At 25℃,the expressible moisture content significantly increased when the setting time was longer than 12 h and the expressible moisture content of MTGase group was lower than that of the control group(p<0.05).In a certain time range,the mobility of water protons decreases with the setting time prolonged.4.The effects of setting time on the release degree of taste substances of TGase-induced surimi gels were studied.The electronic tongue analysis showed that significant difference was found among the release degree of taste substances when the surimi gel structure is different.The diffusion rate constants(Ka)of Na Cl,sucrose and sodium glutamate of surimi gels when setting at 40℃ for various time were significantly different(p<0.05)with the setting time prolonged and the value of control group was higher than that of MTGase group at the same setting time.Ka of Na Cl gradually decreased(p<0.05)with the setting time prolonged and the lowest value were 0.089 and0.072 respectively.Ka of sucrose decreased firstly and then increased significantly(p<0.05),reaching the lowest value 0.055 and 0.044 respectively when setting for 3h.Ka of sodium glutamate of control group reached the lowest value(0.065)at 3h.However,there was no significant difference on Ka of sodium glutamate in MTGase group with the setting time prolonged(p>0.05).The Ka of the flavor substances was negatively correlated with the breaking force,hardness,chewiness and cross-linking density,and positively correlated with the pore size of the gel network within a certain time range.5.The effects of setting time on the volatile components of TGase-induced surimi gels at different temperatures were studied.There was significant difference among the release degree of volatile constituents when the surimi gel structure is different.The contribution to volatile constituents by alcohols and ketones such as 1-Octen-3-ol,2-Octen-1-ol and [1,1’-Bicyclopentyl]-2-one in surimi gels was the highest and the contribution by saturated alkanes and olefin hydrocarbons was lower.Different heating conditions resulted in difference of volatile components in type and quantity of surimi gel.Under the same heating condition,the difference of volatile of control group and MTGase group was in quantity.The amount of volatile components of control group was higher than that of the MTGase group. |
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