| As the consumption of tropical fruit-Carica papaya continues to increase,the amount of by-product Carica papaya seeds will increase.As a kind of waste,it will exert certain pressure on the environment,so it will increase its added value and realize“turning waste into treasure”.It is a feasible idea;at the same time,with the increasingly contradiction between the supply of animal protein and the needs of residents,the development and utilization of plant proteins is increasing.The protein content of Carica papaya seeds?dry basis?is about 30%.The functional value of Carica papaya seeds protein is studied,which provides theoretical support for new product development.This paper first analyzes the basic nutrients?mineral elements,fatty acids,amino acids?of papaya seeds;then uses RSM to optimize the extraction rate of protein,and studies the effects of pH and ionic strength on protein emulsifying and foaming properties.The thermal properties,SDS-PAGE and amino acid pattern of papaya seed protein;preliminary exploration of the structural properties of papaya seed protein components?albumin,globulin,gluten?;finally,the study on the gel properties of papaya seed protein to surimi influences.The relevant test results and conclusions are as follows:?1?The results of nutrient analysis of Carica papaya seeds showed that the content of crude fat?25.27%?,crude protein?26.91%?and crude fiber?27.47%?was higher;rich in mineral elements,among which Ca?2.03%?and K?4.99%?is higher,the higher content of trace elements is Fe?142.50 mg/kg?,heavy metal elements are in the safe content range;20 fatty acids are detected,the saturated fatty acid content is 23.40%The unsaturated fatty acid content is 76.955%,and the monounsaturated fatty acid-oleic acid?72.74%?is the most important component of fatty acids.Its fatty acid composition is similar to the olive oil known as"liquid gold";18 amino acids are detected in the protein.The amino acid type is relatively complete,and the tryptophan amino acid score is significantly higher than other essential amino acids,but its composition ratio is relatively unbalanced,and it can be used in combination with other proteins?such as grain protein?to increase its utilization value.?2?In this chapter,Carica papaya seeds protein was prepared by alkali-soluble acid precipitation method.The best extraction process was optimized by response surface methodology:pH 11.3,ratio of material to liquid:45mL/g,time:224min,temperature:47.5?.Under the conditions,the average value of the verification test results is 53.74%,which is close to the theoretical value of 55.21%.The isoelectric point?pI?of Carica papaya seeds protein was 3.0,solubility,emulsification and stability,foaming and stability were lowest near the isoelectric point,and the alkaline function was enhanced.At 0.8 moL/L NaCl solubility,emulsifying properties and stability,foaming properties and stability of the solution are the highest.Under different pH conditions,the Carica papaya seeds protein had the lowest hydrophobicity near the isoelectric point,while?max had the highest fluorescence intensity.Under the acid and alkali conditions,the free sulfhydryl content decreased.The protein contains six subunits with a molecular weight in the range of 20-170 KDa;the DSC spectrum shows two endothermic peaks with denaturation temperatures?Tp?of 60.7? and 123.6?,respectively,and the enthalpy changes??H?are 21.82 and 42.73 J/g;Carica papaya seeds protein contains 16 kinds of amino acids?tryptophan is not measured?,8 kinds of essential amino acids are complete and contain the essential histidine for infants and young children,the first limiting amino acid is lysine and methionine is second Limit amino acids.?3?Osborne protein fractionation method was used to extract the protein components?albumin,globulin,gluten?from Carica papaya seeds,and the structural properties were explored.The contents of albumin,globulin and gluten were 13.01%,51.27%and30.60%,respectively,and the isoelectric points were 2.5,3.5 and 2.5,respectively.The surface hydrophobicity of protein components is compared:albumin>globulin>glutenin.The CD spectra of the three protein components were mainly?-sheet and random coil,and the sum of the content of?-helix and?-sheet was:gluten?59.57%?>albumin?53.23%?>globulin?52.44%?,indicating that the order structure of gluten is higher than that of albumin and globulin;the DSC spectrum of three protein components shows the denaturation temperature contrast:gluten>albumin>globulin,which is the comparison of the size of the enthalpy change and the circle The results of the two chromatographic order are consistent.The SDS-PAGE map showed that the albumin contains 6 bands with a molecular weight range of 20-61 KDa;the 5 subunit bands of the globulin have a molecular weight range of 20-63 KDa;and the gluten only has one subunit that molecular weight is 22.66 KDa.?4?The effects of different addition amounts?0%,0.5%,1.0%,1.5%,2.0%?of Carica papaya seeds protein on the gel properties of white mullet were investigated.The test results are as follows:the breaking force,breaking distance,water holding capacity,full texture?hardness and chewiness?,storage modulus?G'?and loss modulus?G''?of the surimi gel are all increased first.The post-reduction trend,in which the puncture performance?breaking force and breaking distance?and the full texture analysis were the best when the protein addition amount was 1.0%,and the rheological properties of the surimi achieved the best result when the addition amount was 0.5%;L*and the whiteness value gradually decreased as the amount of addition increased,while a*and b*increased.Through the determination of chemical force,the main chemical forces forming the surimi gel are-hydrophobic interaction and non-specific binding. |
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