Bioactive peptides are small molecular peptides with some physiologically active functions. These peptides have been shown to possess antibacterial, antioxidant, and blood pressure lowering activities. Although walnuts are rich in high-quality plant proteins, the extracted walnut dregs have low utilization by the walnut industry chain. Therefore, the aim of the study was to investigate the nutritional value and antioxidant activity of walnut dregs in order to increase the added value of walnut by-products. Using the response surface methodology, the optimum process parameters of purification and stability for walnut polypeptide liquid were determined as follows: pH 4.5, 8 column/hours (h) column speed and 3:2 ratio of anion to cation. The scavenging reaction rates for hydroxyl radicals and superoxide anion by 3, 5, 10 u ultrafiltration membrane fractionation screening were found to be 73.3% and 64.4%, 66.1% and 58.9%, 59.2%, and 51.6%, respectively. After comparison, walnut polypeptide liquid showed some degree of antioxidant capacity. The stability of walnut polypeptide liquid was optimized by the response surface. Under the homogeneous pressure of 35 Mpa, the use of a certain amount of stabilizers improved the stability of walnut polypeptide liquid. In conclusion, with the addition of additives, the optimum values of parameters for walnut polypeptide liquid obtained using response surface methodology were determined as follows: the ratio of solid to liquid was 15%; the amount of protein sugar was 0.2%; the amount of citric acid was 0.25%; and the addition of walnut powder flavor was 0.15%. Also, the study has provided a theoretical basis for the waste utilization of walnut by-products, and partial support for the intensive processing of the walnut industry chain.
Based on passive total neutron counting with the 3He detectors, an assay system that can define the plutonium holdup in glove-box directly had been established through optimization design by Monte-Carlo simulation. The subsequent debugging for the electronics of this system ensured the system staying in a good operation state. The carried out experimental measurements had defined a series of parameters for the system, including the optimal operation voltage, detection efficiency for neutrons, spatial efficiency distribution, and the relationship between sample mass and the counts. Finally, according to the on-site measurements, the RSD of the measurement system for the glove-box holdup was 0.2%, which indicates the excellent stability of this system.
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