Preparation And Function Evaluation Of Protein Isolates From Sthenoteuthis Oualaniensis

Sthenoteuthis oualaniensis is a kind of warm water marine species of Symtectoteuthis Ommastrephidae,it is mainly distributed in the Indian Ocean,Pacific Ocean and subtropical waters,and is widely distributed in the waters of the South China Sea and the northwestern part of the Indian Ocean.China has built Nansha fishery production information network system in 2011,the biological resources and distribution of Symplectoteuthis oualaniensis in South China Sea were monitored,by the preliminary estimate,the biological resources of Sthenoteuthis oualaniensis is huge,the annual catches can reach up to two million tons,is one of the largest potential marine biological resources.The protein content of the carcass muscle of the Sthenoteuthis oualaniensis accounts for 17.24% of the fresh weight and it has the higher protein content.It is one of the most promising protein resources in the ocean.It has high research value,but because of its meat quality is hard,the edible value is not high,deep processing is needed.This paper mainly discusses the optimum technological conditions and technological process of the preparation of the carcass muscle protein from the Sthenoteuthis oualaniensis,and analyzes the basic composition,function and structural characteristics,and and preliminary study of some functional and structural characteristics with the impact of pH changes.The main findings are as follows:1.In order to explore the best technological process for the preparation of carcass muscle protein from the South China Sea Sthenoteuthis oualaniensis,the single factor experiment was used to optimize and compare the technological conditions.The optimized results were: the dissolution rate of the prepared protein was the highest(80%)under the condition that pH 12.0,ratio of 1: 9(g / mL),dissolution temperature of 4 ℃ and dissolution time of 10 min;The results showed that the yield of precipitated protein was highest that dissolved at the best acid(pH 2.0)and best alkali(PH 12.0)and subsided at pH 5.5,and the yield of precipitated protein was up to 60% in the acidic environment,which was higher than that of alkali sediment;The effect of pH value on the composition of protein isolate was different.The Myosin heavy chain(MHC)and Paramyosin(PM)were faster at different pH conditions,and the acidic condition has a greater impact on degradation of Tropomyosin(TM),and Actin(A)changes less obviously in the acid,alkaline environment.Therefore,the muscle of the Sthenoteuthis oualaniensis was dissolved under the condition of pH 2.0,solid-liquid ratio 1: 9,dissolution temperature 4 ℃,dissolution time 10 min,and then precipitated at pH = 5.5 can get the most protein,and the protein composition are least affected.2.The basic nutrient composition,amino acid composition,mineral element and heavy metal content of the prepared protein were determined by semi-micro Kyling’s nitrogen method,burning method and graphite furnace and atomic absorption spectrometer,and the nutrition of the protein was evaluated.The results showed that the protein yield was 22.88%-69.34% under the condition of four kinds of better dissolving and precipitated pH conditions,and the yield is higher at extreme alkaline environment(PH 12.0).The color of the Sthenoteuthis oualaniensis protein is pure white or white slightly yellow,the crude protein content is above 97.05%,the ash content is lower than 1.87%,the powder contains 17 kinds of amino acids,the required amino acid content of the total amino acid content ratio of up to 52.32%,and the ratio of essential amino acids to non-essential amino acids is above 78%,and belongs to high quality protein.According to the FAO / WHO standard,the amino acid ratio of the separated protein powder is equal,the first limiting amino acid is methionine,followed by valine,and The lysine content is 1.5 times the lysine content in the ideal mode,and the amino acid content is fully consistent with the adult requirement.The solubility,emulsifying and emulsifying stability,foaming and foaming stability and gel preparation were studied by analyzing and analyzing the functional characteristics of the separation protein of Sthenoteuthis oualaniensis,and the first three items The effect of the index on the pH condition was studied.The results showed that the solubility of the prepared protein was not more than 21.7% under the condition of four kinds of dissolved and precipitated pH values,and the solubility was greatly affected by pH.The solubility of the protein is gradually increased with the pH value gradually decreasing,and the solubility of the protein is higher than that of the acidic condition.Under the condition of dissolving-precipitating pH 2.0-5.5,the emulsification of the isolated protein was about 56.78 m2/g,and the emulsification of the four kinds of protein was the same,and the emulsifying activity was better under alkaline condition.The emulsifying stability of the isolated protein under acidic conditions is better than that of the alkaline condition.The effect of pH value to foaming property and the stability of the foam is affected by multiple factors,the fluctuation is large.However,the foaming properties of the four isolates were poor under the condition of pH 6.0,and the foaming and foaming stability were negatively correlated with the overall trend of pH change,that is,the protein at the same pH,the higher the foaming property,the lower the stability of the foam;The hardness,elasticity and water loss of the protein were compared.The hardness values of the four kinds of proteins were small,but the overall hardness was above 486.89 ± 92 and the hardness was higher.The gel elasticity and water holding capacity of the protein were poor when the pH value was 3.0-5.5.4.The structure and properties of the separation protein of Sthenoteuthis oualaniensis were studied and analyzed.The total thiol and active thiol,surface hydrophobicity and tryptophan fluorescence were measured.The effects of the first two indexes on the pH were studied.By analyzing the experimental results,we can find:The total sulfhydryl and active mercapto contents of the isolates were significantly higher than those of the acidic conditions when the pH value was 12.0-5.5 and 11.2-5.5.The total thiol and active mercapto groups of the four isolates showed the same trend with the pH,And the maximum value was obtained under the neutral conditions of pH 6.0,the minimum value were obtained under very acidic,very alkaline conditions;and the hydrophobicity of the isolated protein was the highest at the pH value of 3.0-5.5.The highest hydrophobicity was 3420.98,The surface hydrophobicity of the four isolates decreased first and then decreased with the change of pH value,that is,the surface hydrophobicity of the isolates near the isoelectric point was the worst.