Study On Surimi Cold-set Gelation Techniques

Surimi-based products with the characteristics of high nutritional value and convenience edible have been popular among consumers around the world.In traditional surimi-based products industry,heating process such as boiling,steaming,roasted or frying plays an important role in the formation of gelation,but high temperature not only damage to heat sensitive substances but not cause high energy consumption and increased production cost.Acid-induced gel as one of emerging cold-set gelation techniques can effectively avoid disadvantages of thermal-set gelation.Therefore,silver carp was selected as raw material,acid-induced surimi gel was prepared by soaking in organic acids in this study,and the mechanism of acid-induced gel formation was elucidated.In addition,glucono-?-lactone(GDL)as an acidulant was applied in preparing surimi gel,and then effect of food hydrocolloids on GDL-induced surimi gel was investigated.Acid-induced surimi gels were prepared from silver carp surimi by soaking in acetic acid,citric acid or tartaric acid in this study,and effect of concentration of organic acids on the properties of surimi gels was also investigated.Of the organic acid-induced and heat-induced surimi gels,the acetic acid-induced surimi gels had the highest TPA(Texture Profile Analysis)parameters.The pH of the surimi gel induced by 3% acetic acid was 4.3,in whiter color but poorer water-holding ability than thermally-treated one.Nevertheless,the protein subunits were observed similar in SDS-PAGE pattern for both gels.Furthermore,the results of in vitro digestion of surimi gels showed that 90% of proteins of acid-induced gels could be digested with combined action of pepsin and trypsin.The surimi gel induced by soaking in 3% acetic acid with highest gel strength was selected to elucidate the gel-forming mechanism.The negative net charge of protein was increased by adding neutral salts,which influenced the surimi protein solubility at acid conditions.The high molecular weight fractions were also formed with myosin heavy chain(MHC)and actin based on electrophoresis analysis.The data of protein subunits solubilized in various solvents revealed that the most important associative force in acid-induce gel was hydrophobic interactions.Furthermore,the compact and fine fiber microstructure in acid-induced surimi gel was observed by scanning electron microscopy.The effects of glucono-?-lactone(GDL)concentration,preheating time and temperature on the gelation characteristics of silver carp surimi were investigated.The breaking force,deformation and whiteness of surimi gel were increased with increasing GDL concentration,while pH and water holding capacity were decreased.When GDL concentration was more than 1%,the texture properties of GDL-induced surimi gel were higher than those of heat-induced surimi gel.Based on the electrophoresis analysis and the data of protein subunits solubilized in various solvents,it was revealed that the main associative force in GDL-induced surimi gel was hydrophobic interactions.Furthermore,the most compact fiber microstructure in the surimi gel incorporated with 2% GDL was observed by scanning electron microscopy.On the other hand,the textural properties and whiteness were increased with increasing preheating time.However,the quality of GDL-induced surimi gel declined when preheating for 4 h.In addition,the breaking force and deformation of GDL-induced surimi gel were increased with increasing preheating temperature from 30 °C to 45 °C,mainly due to the fact that the gel network formation was promoted by preheating.The compact fine fiber microstructure of surimi gel was formed by incorporating with 2% GDL and preheating at 45 °C for 1 h,resulting in the obtained superior textural properties.The highest breaking force of GDL-surimi gel was reached at 691 g,which was almost 2.5 times higher than traditional heat-induced surimi gel.However,the textural properties of GDL-induced surimi gel were decreased when preheating temperature was increased to 50 °C,due to myosin heavy chain degradation and fiber disruption.Finally,the effect of fish geltin,carrageenan and soybean dietary fiber on the characteristics of GDL-induced surimi gel was investigated.The results showed that the water holding capacity(WHC)of GDL-induced surimi gel was increased and the cooking loss(CL)was decreased by adding fish gelatin and soybean dietary fiber,respectively,while a small amount of carrageenan had no signicantly effects on WHC or CL.On the other hand,the compact and dense network structures of GDL-induced were disrupted to some extent with 1% fish gelatin,0.05% carrageenan and 5% soybean dietary fiber,however,the breaking force is still up to 693 g,the WHC was increased to 86% and the CL was significantly decreased.In conclusion,surimi gelation prepared by soaking in organic acid or induced by GDL all presented higher textural properties than traditional heat-induced surimi gel,mainly due to the compact and uniform three-dimensional network structures were formed with pH decreased at low temperture.Therefore,cold-set gelation technoiques have a potential to replace the traditional thermal-set galtion techniques to develop new surimi-based products and provide a new way for freshwater fish processing.