Search

This article explored the effect of insoluble okara fiber (IOF) on the properties of okara protein (SOP) emulsion. The effects of different concentrations of IOF (0.25 wt%, 0.50 wt%, 0.75 wt% and 1.00 wt%) on the microstructure, interfacial activity, emulsifying activity and stability of SOP emulsion were studied with sunflower oil as oil phase. The results showed that with the increase of the IOF concentration, the particle size of the SOP/IOF emulsion showed a trend of gradual increase. The laser confocal microscope observation experiment showed that the emulsion droplets change in the same trend, and the absolute value of the zeta potential presents an increasing trend. The content and concentration of interfacial protein showed an increasing trend, and the change of rheological index showed that the trend of shear thinning was increasing, and high concentration of IOF could significantly enhance the long-term storage stability, acid resistance stability and salt resistance stability of SOP emulsion. This provides a theoretical basis for the further application of IOF in the protein emulsion gel system.

In order to improve the quality of high-temperature defatted soybean meal, which is the raw material for producing soybean protein powder, and improve the stability and reliability of process control. Under the condition of microwave power of 20 kW, wind speed of 2.5 m/s, and material thickness of 20 mm, the effects of microwave treatment for 4 to 6 min on the moisture content, temperature, total number of colonies, color after water-dissolving and the secondary structure of soybean protein in high-temperature defatted soybean meal were analyzed. It could be used to guide the production and application of high temperature defatted soybean meal for soybean protein powder production. The results showed that: When the microwave treatment time was between 4 and 6 min, the water content decreased at a rate of 1.51%/min; when the microwave treatment time was 5.45 min, the temperature could be controlled at 103 ℃, the killing rate of microorganisms reached 96.8%, and the total number of colonies reached 100 CFU/g; when the microwave treatment time was between 4.62 and 5.45 min, the red value of the aqueous solution were relatively stable, the brightness and yellow value changed slightly, and the color was good; when the microwave time was ≥5 min, the urease activity was negative, which met the requirements of food for infants and children; microwave treatment had a significant effect on the secondary structure of the protein. When the microwave time was between 4.29 and 5.45 min, the α-helix transformed to the β-turn and then disappeared, and the amount of the β-turn increased rapidly; when the microwave time was between 5.45 and 6 min, the β-turn was rapidly transformed to the α-helix; the β-sheet changed only in small amplitudes and was relatively stable during the entire microwave treatment process. Microwave treatment can effectively control the moisture, color, total number of colonies, urease activity of high-temperature defatted soybean meal, and improve the secondary structure of soybean protein, which is of positive significance for improving the quality of high-temperature defatted soybean meal and expanding the application field.

The identification model of chlorpyrifos pesticide residues in wheat was established based on near infrared spectroscopy and stoichiometry. Wheat samples with different chlorpyrifos residues were prepared by spraying method. Near infrared diffuse reflectance spectra of samples were collected, and qualitative prediction models of factorization method, Euclidean distance method and quantitative prediction model of partial least squares method were established. The results showed that: The qualitative discrimination rate of factorization method was higher than that of Euclidean distance method, the characteristic bands of construction conditions were 5543.68~4643.72, 7582.43~6510.28 cm−1, the preprocessing method was second derivative+vector normalization+5-point smoothing, the discrimination rate could reach 96%. The characteristic bands of the construction conditions of partial least squares quantitative discrimination model were 5543.68~4643.72 cm−1, 7582.43~6510.28 cm−1, the preprocessing method was to eliminate the constant offset, the main component fraction was 7, the cross validation coefficient (R2) was 99.46, and the mean square residual (RMSECV) was 1.15. The correlation between the actual value and the predicted value was good, and the minimum detection limit was 1 mg/kg, which could accurately determine the pesticide of Chlorpyrifos in wheat. The above results showed that the discrimination rate of the qualitative analysis model established by the factorization method was as high as 96%, which could realize the qualitative analysis and identification of chlorpyrifos pesticide residues in wheat, and the partial least squares method could realize the quantitative analysis and identification with good reproducibility.