| Chicken bone is the main by-product of chicken processing,which contains relatively full soluble protein,rich amino acids,high biological titer,and is a high-quality protein source.When chicken bones are braised,a large number of amino acids,peptides and other fresh substances can be dissolved.They will have different degrees of Maillard reaction and other reactions,so that the taste is delicious.At present,the clear soup products prepared from chicken bone by hot press extraction,separation and concentration,purification and impurity removal are also called "flavored chicken bone element",which is widely used in meat products,convenience food and salty flavor fields.However,clear soup prepared from livestock and poultry bones usually contains high purine,and excessive intake will lead to high uric acid in the body,which can cause gout in severe cases.Therefore,it is of great significance to develop low purine chicken bone clear soup products.In this paper,by optimizing the technological conditions of low-purine chicken bone clear soup and adding natural antioxidant active substances,while pursuing high nutritional value and good flavor,the purine content in chicken bone clear soup is reduced as far as possible and the inhibitory effect of chicken bone clear soup on xanthine oxidase activity is improved.To provide new theoretical and technical support for industrial processing of low purine chicken bone clear soup and prevention of gout or hyperuricemia.The main research contents and results of this paper are as follows.With the ratio of total purine to protein concentration as response value and sensory evaluation as auxiliary index,the optimal preparation conditions were obtained by Box-Behnken response surface method.The taste characteristics of chicken bone clear soup were evaluated by free amino acid,flavorable nucleotide,monosodium glutamate equivalent,electronic tongue and sensory results.headspace solid-phase microextraction gas chromatography mass spectrometry,HS-SPME-GC-MS),headspace solid-phase microextraction gas chromatography olfactory,HS-SPME-GC-O,The key volatile flavor compounds were identified by odor active value(OAV).Results:The optimum preparation conditions of chicken bone clear soup were as follows:temperature 122.3℃,time 149.8 min,and solid-liquid ratio 0.94.Under these conditions,the total purine content of chicken bone clear soup sample was 407.03 mg/L,protein was 3.67 g/100g,and the ratio of total purine to protein mass concentration was 110.98.The results of taste analysis showed that glutamic acid contributed directly to the umami of chicken bone clear soup,and the taste active value(TAV)was 1.96.The TAVs of flavorable nucleotides were all less than 1 and had no direct contribution to taste.Sensory evaluation analysis showed that the overall acceptable grade was "good",which was suitable for the subsequent production of bone broth products.51 volatile flavor compounds were identified by HS-SPME-GC-MS analysis,and 23 compounds with OAV greater than 1 were identified,including(E)-2-nonenal,(E)-2octenal,3-(methylthioyl)propanal and 1-octene-3-ol.GC-O analysis showed that hexal,2-methyl-3furan mercaptan,3-(methyl-thiophenyl)propanal,butyl lactone,1-octene-3-ol,caproic acid,(E)-2heptenal,dipropyldisulfide,(E)-2-nonenal and a-terpineol had stronger odor intensity.Contribute the aroma of grass,meat,potato,sweet,mushroom,sour,sulfur and fat to the chicken bone soup.Onion not only contains a lot of antioxidant active substances,and it is also a seasoning agent in the process of food processing,with seasoning,fishy and other effects.Therefore,adding onion to the preparation of chicken bone clear soup can realize the inhibition of XOD activity and improve the sensory quality of the product.According to the analysis results of physical and chemical indexes,onion can bring more flavor substances to chicken bone clear soup,improve the umami,and inhibit or cover the original bitterness.The overall acceptability of onion increased significantly at a low level,but excessive addition of onion resulted in a significant decrease in sensory scores,which was related to the increase of irritating taste caused by the high sulfur compounds in onion.In terms of antioxidant capacity,the addition of onion significantly enhanced the activity inhibition of free radicals and xanthine oxidase in chicken bone clear soup,which had a dose-effect relationship with flavonoids and polyphenols,and significantly improved the function of chicken bone clear soup.The results can provide scientific basis for the development of chicken bone soup products that inhibit the production of uric acid in the future.In order to further explore the deep mechanism of the enhanced inhibition of xanthine oxidase in chicken bone clear soup after the addition of onion,LC-MS technology was used to conduct nontargeted metabolome studies on the samples before and after the addition of onion,analyze the influence of onion on the metabolites of chicken bone clear soup,and screen out the flavonoids and polyphenols with significant differences.Secondly,isoquercetin,the flavonoid compound with the greatest change,was identified according to the results of the untargeted metabolome study.Through in vitro activity inhibition tests and enzyme kinetics studies,it was proved that the combination of isoquercetin and xanthine oxidase was reversible,and had a good inhibition effect on XOD activity,and showed a doseeffect relationship.The fluorescence quenching experiments showed that isoquercetin had obvious quenching effect on xanthine oxidase fluorescence spectrum and could combine well with it,but it did not affect the polar microenvironment of XOD chromophore.Fourier infrared spectroscopy showed that isoquercetin could make the secondary structure of xanthine oxidase more compact,thus affecting its catalytic activity.Finally,molecular docking technology was used to simulate the interaction mode of the two.The results showed that isoquercetin could insert into the active cavity of xanthine oxidase and interact with the surrounding amino acid residues.The driving force of the interaction was mainly hydrogen bond and van der Waals force.The results can provide scientific basis for the production of functional chicken bone clear soup and the application of isoquercetin. |
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