Study On Thermal Processing Properties Of Surimi Gels And Formulation Of The Heat Tolerant Surimi Sausage

The surimi product is a kind of food with certain elasticity and unique flavor that which is made of surimi and certain auxiliary materials by forming,heating and solidifying.However,at present,commercial surimi products are mainly refrigerated or frozen products,with short shelf life and high transportation and storage costs,which cannot satisfy the consumers'demand of convenience and ready-to-eat.After high-temperature sterilization,surimi products are able to achieve commercial sterilization,which can realize normal temperature circulation.However,the gel structure destruction of surimi products might happen after high-intensity heating treatments,resulting in a significant reduction in quality.In order to obtain high quality surimi products which could be stored at room temperature,the effects of different heat processing conditions on the gel properties of surimi gels were studied with silver carp?Hypophthalmichthys molitrix?surimi as a raw material.Via the analysis of protein chemical interactions and spatial structure changes,the mechanism of thermal processing properties of surimi gel was deeply discussed.On this basis,the gel properties of surimi products after high-temperature sterilization were improved by adding heat tolerant exogenous additives.This study provides a theoretical basis for the rational design of sterilization process and the development of high-quality surimi products which could be stored in normal temperature.In addition,it will also open up a new way for promoting the large-scale industrial production of freshwater products,especially freshwater surimi products in China.Firstly,the influences of different thermal processing conditions on the gel properties of surimi were investigated.Changes of the gel strength,texture profile analysis,whiteness,water-holding capacity and microstructure under different heating temperatures?100¹25??and heating times?2⁶0 min?treatments were determined,so as to explore the rules of changes of surimi gel quality with variation of thermal processing conditions.The results showed that,the gel strength,springiness,hardness,water-holding capacity and whiteness showed a downward trend with the heating time increased.And the higher the temperature,the faster the relevant indexes decreased.At the end of heating,value of gel strength was decreased by 16.25%,53.77%,67.15%and 63.95%after heating at 100? for 60 min,110? for 50 min,120? for 40 min and 125? for 30 min,respectively.There were more protein aggregates when heating temperature was much higher,with the appearance of small and compact arranged surimi network structure.Besides,as heating time prolonged,regular and orderly three-dimensional structure became fragile and loose,as well as the lager holes,and the water retaining capacity was reduced.Compared with the heating time,the effect of the heating temperature on the gel properties was more intense.Therefore,a gradient heating program can be designed to improve the quality of surimi products after sterilization by reducing the phenomenon of partial overheating.Secondly,the influences of different thermal processing conditions on the chemical interactions and protein spatial structure of surimi were investigated.Changes of chemical bonds,total sulfhydryl groups,protein solubility,TCA-soluble peptides,moisture status,SDS-PAGE electrophoresis,Raman spectroscopy and infrared spectrogram under different heating conditions were investigated,so as to explore the mechanism of thermal processing properties of surimi gel.The results showed that the ionic bonds increased as the increase of thermal processing temperature and time.The hydrogen bonds increased with heating time increasing at 100? and 110?,while increased first and then decreased at 120? and 125?.As to hydrophobic interactions,disulfide bonds and non-disulfide covalent bonds,the contents declined with fluctuations and finally tended to be stable,indicating certain destructive effects of high-temperature treatments on the main chemical forces.Electrophoretic analysis indicated that the contents of myosin heavy chain?MHC?gradually decreased or even disappeared with the increase of heating temperature and time.The contents of actin were decreased slightly,and these changes got more significant with the increase of heating temperature.The appearance of bands above 200 kDa indicated the myofibrillar protein had accumulated.Increasing TCA-soluble peptides also illustrated the thermal degradation of surimi gel proteins.Results of T₂ relaxation times showed that water in the gel system became more active when heating temperature increased,and immobilized water migrated into free water,resulting in significant increasing free water contents and relaxation times.The random coil tended to be the main protein secondary structure of surimi gel and damaged with the increase of treating intensity.While?-sheet increased,and the change of?-helix content was the same with the hydrogen bonds.These leaded to the damage of the gelling properties of surimi gels.Thirdly,the influences of exogenous additives on the gel quality of surimi,which was heating at 120? for 10 min,were investigated.These two kinds of heat tolerant were added and surimi plural gels were made.Changes of rheological properties,textural characteristics,water-holding capacity,moisture distribution,whiteness,chemical bonds,TCA-soluble peptides and SDS-PAGE electrophoresis were determined,so as to analysis the effect of curdlan?CUD?and potato hydroxypropyl distarch phosphate?HPDSP?on improving the gelling quality of surimi products after sterilization.With the addition of CUD,whiteness took on a decrease and hydrogen bonds and hydrophobic interactions increased,while no significant effect was observed on protein compositions.With the addition of HPDSP,the values of whiteness,hydrogen bonds and disulfide bonds both took on an upward trend,and it could enhance the cross-linking with the MHC and actin.As the addition of CUD and HPDSP,the storage modulus G?during the temperature increasing process,textural properties and water-holding capacity improved,as well as the increase of immobilized water and the decrease of free water,leading to a much stable gel system.The decrease in content of TCA-soluble peptides indicated that the degradation of surimi protein by high-temperature heating could be reduced.Therefore,the addition of CUD and HPDSP could inhibit texture deterioration of surimi gel and increase protein thermal stability,and further obtain better textural properties,taste and flavor.The final optimized formulation?based on the total mass?of the heat tolerant surimi sausage was as follows:69.2%of frozen surimi,26.1%of water,2.8%of HPDSP,1.7%of salt and 0.2%of CUD.