| Fish soup is rich in nutrition,delicious and tasty,simple and convenient,loved by people.In the cooking process,a complex colloid structure is formed due to the migration of lipid,protein and other components present in the fish.Tuna head is rich in protein,mineral elements,eicosapentaenoic acid(EPA),docosahexaenoic acid(DHA)and other polyunsaturated fatty acids,which have extremely high nutritional value.During the cooking process of tuna head soup,the transfer of nutrients and flavor componds into the soup and the formation of self-assembled micro/nano-sized colloidal particles,as well as the biological activities have been rarely reported.In this work,the tuna head soup as the research object,the effects of different ratio of tuna head pieces to water on the quality of the tuna head soup under different cooking methods were compared and analyzed.The transfer of lipid and other substances was studied,as well as the formation and change of micro/nano-sized colloidal structures and the components of micro/nano-sized colloidal particles were analyzed.The antioxidant activity of differernt size colloidal particles in the tuna head soup was also studied.This work could provide theoretical basis for the industrialization and standardization production of high-quality fish soup,promote the theoretical innovation in the field of novel self-assembled bioactive structures during food peocessing.(1)Under normal pressure cooking condition,the broth and pan-fried soup(PFS)of tuna head were stewed by two different methods.The effects of different ratio of tuna head pieces to water on the migration of each nutrients and sensory score in the two kinds of tuna head soup were compared and analyzed.The results showed that when the ratio of tuna head pieces to water was 1:8(g/g),the content of lipid,water-soluble protein,total sugar,total minerals and solid matter and sensory score of broth and PFS reached the highest.Furthermore,the migration content of nutrients and sensory scores in the PFS were higher than that of broth,which may be one of the reasons why PFS is more popular.(2)Based on production process of fish head soup,the transfer of lipid and other substances were studied.The results showed that as the cooking time prolonged,the nutrients in the fish head tissue gradually migrated into the soup,and the concentration of each substance gradually increased.The content of lipid,water-soluble protein,total sugar and vitamin E reached the maximum with the condition of fish and water ratio of 1:8(g/g),boiled for 150 min.With the extension of cooking time,the concentration of total minerals and solid matter was continued to increase and the chromaticity was getting brighter.The electronic tongue was used to analyze the taste profiles of the two kinds of fish head soup at different boiling times.The taste profiles of the broth was partially overlapped,and the taste profiles of the PFS was distributed in each quadrant,indicating that the tastes of the broth at different times were similar,while the tastes of the PFS were obviously different.The microstructure of colloidal particles in the tuna head soup was observed by optical microscope and laser confocal microscope,it was found that a large number of spherical particles of different sizes in the tuna head soup.The main body of particles was triglycerides,while the polar lipids and carbohydrates moieties were almost dispersed around particles.And a large amount of protein particles were also present in the soup.(3)The tuna head soup was treated by crude filtration,micro-filtration and ultrafiltration.After the tuna head soup was treated with three methods,the average particles size of the colloidal particles in the tuna head soup became significantly smaller which was observed by using malvern laser particle size analyzer.After the tuna head soup was treated by the method of micro-filtration and ultrafiltration,many large particles were trapped by the filter membrane,the small particles were permeable to the filter membrane,and the average particle size of the colloidal particles was significantly smaller(P<0.05).The antioxidant activity of fish head soup with different particle size was studied by chemical assay and cell antioxidant activity assay(CAA).Four kinds of chemical methods were used to determine the in vitro antioxidant capacity of different sizes of tuna head soup colloidal particles.It was found that fish head soup with coarse filtration(OGS),microfiltration(MFS)and ultrafiltration(UFS)all had certain antioxidant capacity,and the order of the antioxidant capacity of the three in vitro was OGS>MFS>UFS.The chemical composition and structure of the tuna head soup colloidal particles were changed during the separation process,resulting in lower antioxidant activity of MFS and UFS than OGS.Furthermore,cellular antioxidant assay was used to evaluate the intracellular antioxidant capacity of different sizes of tuna head soup colloidal particles,and it was also found that different sizes of tuna head soup colloidal particles had intracellular free radical scavenging ability.The intracellular free radical scavenging abilities of OGS,MFS and UFS were significantly different after different dilution ratios.The order of the intracellular antioxidant activity of the three was inconsistent with the results of the chemical assay.In the low dilution range,the antioxidant capacity of UFS was stronger than that of OGS and MFS.When the dilution factor was further increased,the antioxidant capacity of UFS was weaker than that of OGS and MFS.It may be related to the mechanism of action of the two methods and the difference of sample concentration.The chemical assay focuses on the action of antioxidant actives and free radicals in the system,while the cellular antioxidant activity focuses more on cellular antioxidant enzymes. |
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