The Oil And Water Migration Of Stuffed Fish Ball As Affected By Freeze-thaw Cycles And Cooking Process And Its Controlling Technology

Surimi product processing is an effective way to realize the value-added utilization of bulk low-value fish.Stuffed surimi products are loved by consumers because of their high protein,low fat,unique taste and flavor.However,quality deterioration as affected by freeze storage and freeze-thaw（F-T）cycles induced the juiciness loss and decreased taste of stuffed surimi products,which seriously affect the market development of products and the economic benefits of enterprises.In addition,the reason,underlying mechanisms and control technology behind the juiciness loss of stuffed fish balls,are still unclear.Hence,the present study sought to investigate the migration behavior and changes of juiciness in the stuffed fish balls to understand the key factors and processing phases contributing to the juiciness loss.By regulating the surimi gel and enhancing the stability of the juiciness system in the fillings,juice preservation and critical quality control technologies are produced,which can significantly improve the eating quality of stuffed surimi products.Overall,this study will serve as a benchmark for controling and improving the quality deterioration of stuffed surimi products affected by storage and transport,and have a practical significance in reducing juiciness loss of stuffed surimi products after frozen storage.The main conclusions are as follows:Firstly,the present study sought to investigate the key factor and processing phases on the quality attributes of the stuffed fish balls to address its juiciness loss.The impact of juiciness loss in stuffed fish ball on thaw loss,water holding capacity and microstructure was studied.The low-field nuclear magnetic resonance（LF-NMR）,filling stability and bromophenol blue and Sudan red staining was used to address its juiciness loss in terms of microstructural changes and migration of water and oil affected by F-T cylce and cooking process.The results showed that there were no significant changes in water and oil migration from the fillings to the outer surimi gel during the F-T cycles,while the juiciness loss mainly occurred in the cooking process after F-T cycles.With the increase of F-T cycles,the water holding capacity decreased significantly,and the thawing loss and cooking loss of stuffed fish balls increased,gel network structure severely destruction mediated by ice crystal and the mean equivalent diameter of ice crystals increased dramatically.In addition,changes of water distribution showed that the immobile water T₂₃ and free water T₂₄ shift right,which induced the water mobility increased and the ratio of the free water A₂₄ rise gradually.The sectional observation and T₁ weighted images also revealed that with the increased F-T cycles treatment,cooking mainly caused a significant change of oil-water migration from the fillings to the outer surimi gel to different extents.The stability of fillings showed that total expressible fluids and the content of fat increased with the increase of F-T cycles.However,the proximate composition of the fillings in the cooked stuffed fish ball showed that the water content decreased,and no significant difference in the fat content,protein and ash.The bromophenol blue and Sudan red staining indicated that water migration played a major role in juiciness loss,oil migration was less than water migration.Secondly,in order to solve the juiciness loss and decreased taste of stuffed fish balls caused by quality deterioration as affected by freeze-thaw cycle,based on regulation of the outer layer of surimi,the effects of addition amount and addition method of different hydrophilic colloid on the juiciness loss,texture properties and whiteness microstructure of stuffed fish balls was investigated.The results showed that the juiciness loss,texture,whiteness and microstructure of adding with pre-emulsification were better than those of adding directly.With the increasing addition amount of carrageenan,konjac gum and curdlan gum,the juiciness loss decreased before increasing.Among them,adding 0.3%（w/w）ι-carrageenan,0.3%（w/w）konjac and0.4%（w/w）curdlan gum with pre-emulsification,the juiciness loss and migration of stuffed fish ball was lower at 28.08%、36.23%and 35.20%,respectively.In addition,the juiciness migration was less significantly,the hardness and chewiness of surimi gel of stuffed fish ball was improved obviously,whiteness values reached the maximum（P<0.05）.And the network structure of gel was denser and the surface was smooth.The holes are fewer and evenly distributed.However,with the increment of xanthan gum,the juiciness of stuffed fish ball was decreased,but there was no significant to improve the texture properties and whiteness.On the basis of determining the addition amount and addition method of a single hydrocolloid,theι-carrageenan,konjac gum and curdlan were optimized,to further explore the influence of juiciness loss of stuffed fish ball through the pairmise compounding.The results showed that compared with control group and sigal hydrocolloid,the juiciness loss of stuffed fish ball and pores can be significantly decreased by the compound.The compound also can significantly improve water holding capacity,whiteness,protein secondary structure content ofβ-fold and texture of outer layer of stuffed fish ball.Among them,the optimum compounding ratio between konjac and curdlan was 7:3,the juiciness loss of stuffed fish ball was the lowest at22.00%,which decreased by 52.22%compared with control group,the texture was highest and whiteness values reached the maximum.Compared with the control group,WHC was increased by 10.62%.Observation by optical microscope showed that the structure of the surimi gel network was orderly,regular,dense and continuous.Finally,the present study sought to improve the eating taste of stuffed fish ball,based on the improvement of stability of the fillings,oil-water ratio,addition amount of emulsifier and soybean protein isolate were respectively studied by juiciness loss,the stability of the fillings,fat oxidation,the volume average particle size and protein adsorption rate of the cooking liquid of filling.The result showed that to control the ratio of oil and water,addition amount of emulsifier and soybean protein isolate,the juiciness loss and fat oxidation decreased significantly,and the stability of filling was improved.With the increasing addition amount of soy protein isolate,the juiciness loss decreaed,TBARS and the average particle size decreased,the adsorption rate of the interface protein was higer.With the amount of 2%and 4%soy protein isolate,there were no significant between them.With the increased of water content in the oil-water ratio,the juiciness loss and average particle size decreased before increasing,and,the TBARS decreased continuously.Among them,the oil-water ratio was 20:80,the juiciness loss was the lowest at 14.73%.All three emulsifiers can effectively improve the stability of fillings and reduce the juiciness loss.Under the same conditions,the effect of glyceryl monostearate to fillings is significantly better than that of sucrose fatty acid ester and lecithin.The filling with 2%（w/w）soy protein isolate,20:80 oil-water ration and 2‰（w/w）glyceryl monostearate,which the juiciness loss was decreased by 73.50%,effectively improving the quality of stuffed fish ball,compared with the control group.