| China,as a large sericulture country,has abundant pupa resources,but due to lack of theoretical support for its intensive processing technology,the overall utilization rate is relatively low.Silkworm pupa protein is the main nutrient in silkworm pupae,and its current content is about 50%~ 60% in the dry base of silkworm pupae.However,its research mainly focuses on protein extraction,nutritional evaluation of primary structure,and preparation of bioactive peptides.No mature and commercial silkworm pupa protein-related products are available in the food industry.The main reason is the potential allergens in silkworm pupa protein,which can cause food safety risks.However,the distribution of allergens in silkworm pupa protein in various proteins has not been studied.Based on the analysis of the basic components of silkworm pupa,this work systematically studied the distribution of potential allergens in silkworm pupa protein,comprehensively analyzed the content of allergens and the proportion of various proteins,and explored the functional characteristics of water-soluble and insoluble proteins in silkworm pupa protein.The insoluble protein is used as the raw material for the exploration of gel protein products,with the aim of providing a theoretical basis for the further development and utilization of silkworm pupa protein in the food industry.The specific conclusions are as follows:(1)The results showed that the content of unsaturated fatty acids in silkworm pupa oil was 60.83%,and the content of oleic acid was the highest(35.43%);the content of insoluble protein in silkworm pupa protein was the highest(53.00%),showing a subunit distribution of 27~85 k Da;the water-soluble protein accounted for 23.63%,showing a subunit distribution of 25~85 k Da;the alkali-soluble protein accounted for 19.73%,showing a subunit distribution of 13~29 k Da;the salt-soluble protein accounted for 2.58%,showing a subunit distribution of 15~35 k Da;the alcohol-soluble protein was only 1.06%,showing subunits mainly distribution of 12 k Da and 20 k Da.Allergen distribution studies showed that the water-soluble,alcohol-soluble,salt-soluble,alkali-soluble and insoluble protein contained six,eight,eight,twelve and three kinds of allergens respectively,whose relative content was 1.33%,25.64%,1.21%,17.93% and 9.86%,respectively.Proteins with high levels of allergens must be desensitized before being used in the food industry.(2)Silkworm pupa water-soluble protein was rich in amino acids,and the ratio of essential amino acids to total amino acids reached 39%.It is a protein resource with high nutritional value.The solubility of silkworm pupa water-soluble protein solution at 70 ? has a small decrease in solubility;in the range of p H 4.0~9.0,with the increase of p H,the contents of ?-helix and ?-sheet gradually increased,and the solubility increased due to the increase of ?-helix and ?-sheet;after p H 9.0,the total contents of ?-helix and ?-sheet tend to show a downward trend.The hydrogen bond and hydrophobic interactions that maintain these structures under strong alkalinity were destroyed,which reduces the protein order degree of protein.The contents of ?-corners and random curl increased,but the degree of spread is not large and the repulsion between proteins increases,the solubility still increased with the increase of p H.In the salt concentration range of 0.2~1.0 mol/L,the solubility increased with increasing salt concentration,and when over 1.0 mol/L the solubility decreased due to salting out.The oil phase volume fraction was 35%,the protein concentration was 1.0 g/L,and the protein emulsification performance was good at p H 10.0;the protein foamability was relatively highest at the protein concentration of 3.0 g/L,foam stability was relatively highest at a protein concentration of 1.0 g/L;the oil holding capacity of protein was up to 3.9 g/g(oil/ protein).(3)The insoluble silkworm pupa protein has an essential amino acid content of 40%,which is a protein resource with high nutritional value,and the proportion of hydrophobic amino acids reached 40%,and the possibility of an opaque gel formed by hydrophobic interaction between protein molecules.After the insoluble protein was treated with different p H and different salt concentrations,rheological frequency scanning and temperature scanning showed that the G? value and G? value of the insoluble protein system were the highest at p H 6.0 and the salt concentration was 3.5%,and the viscoelasticity was the optimal;in the range of p H5.0~8.0,salt concentration 0.0%~ 3.5%,the G' value was significantly greater than the G " value,tan ? <1,and the insoluble protein gel system is a weak gel.Raman spectroscopy shows that increasing the p H will cause an increase in the order degree of protein structure,,but it is not conducive to the formation of protein networks.The G' and G" values of the insoluble protein system were the lowest at p H8.0.The exposure of tryptophan is related to hydrophobic interaction.At p H 6.0 and a salt concentration of 3.5%,tryptophan tend to be embedded.The formation of hydrophobic interaction within the molecule is more conducive to the formation of silkworm pupa protein gel network,the G? value and G? value were the highest.When tryptophan residues tend to be exposed,it may lead to reduced the hydrophobic interactions within protein,which is not conducive to the formation of silkworm pupa protein gel network.The exposure of tyrosine is related to the hydrogen bond force.Tyrosine has the least exposure at p H 6.0 and salt concentration of 3.5%,indicating that the intermolecular hydrogen bond was reduced.Combined with the rheological results,it is speculated that excessive bonds formed may be not conducive to the formation of insoluble silkworm pupa protein gel network system.Hydrophobic interaction and hydrogen bond may be the key forces affecting the protein gel network.When the protein microenvironment changes,the structure of the protein gel network will also change,and the G? and G? values of the rheological characteristics will be altered.The addition of TG enzyme can improve the gel properties of insoluble proteins,the G? and G? modulus of the protein system was significantly increased,and the viscoelasticity was enhanced.(4)For pure silkworm chrysalis protein products,the addition of psyllium husk powder(0.5%)and the addition of TG enzyme at 0.3% had the highest texture characteristics such as hardness,adhesion and elasticity,but it had a rough texture.On this basis,the improvement effect was better by adding soy protein.Compared with pure soy bean curd,when the addition ratio of silkworm pupa reaches 1.0 g/g,although the hardness and adhesion were reduced to a certain extent,it still maintained good elasticity,and the appearance was uniform and the taste was good,so the optimal compounding ratio of silkworm pupa insoluble protein and soybean protein isolate(20.0g)is less than 1.0 g/g(0 ~ 20.0g). |
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