Foaming and Structural Studies on the Acidic Subunit of Amaranth 11S Globulin Modified with Antihypertensive Peptides as a Function of pH and Ionic Strength

Some studies aimed at revealing the relationship between protein structure and their functional properties. However, the majority of these reports have been carried out using protein isolates. There are limited reports on the possible relationship between the functional properties and the structure of a purified protein. In this work the amaranth 11S globulin acidic subunit (AAC) and five mutations of the same protein that were modified in their variable regions with antihypertensive peptides (VYVYVYVY and RIPP), were analyzed at two ionic strength (2.9 and 17.6 g/L NaCl) and pH (3.0–7.0). Results revealed better solubility for the proteins mutated at the terminal ends (AACM.1 and AACM.4) and lower solubility for the protein inserted with RIPP peptide. Spectroscopy studies revealed an increase of β-sheet structure at high salt concentration for all proteins. It was also observed that salt concentration acted as a modulator, which allowed a better foam features for all modified proteins limiting movement of side chains and reducing red-shifted displacement of λmax. All proteins showed foam capacity ranging from 76 to 93% although foam stability was twofold better for modified proteins than for AAC at high salt concentration. This study allowed better understanding about the structural changes that influence the foaming properties of engineered proteins.     

Evaluation of Water Ammonium Ion Test Kit and Its Feasibility for the Analysis of Protein in Food

The traditional method for the determination of protein in food needs the operations of digestion, distillation, absorption, and titration; therefore, it is complicated and time-consuming and requires professional personnel. Is there a more convenient and faster detection method that can directly determine the ammonium ions in protein digestion solution to obtain the protein content of food and avoid the distillation–absorption–titration process? The feasibility of water ammonium ion test kits for food protein rapid detection was discussed here. After digestion, the protein in food transforms into ammonium ions in the digestion solution. Because of the variety of food, there are many different inorganic ions left in the food digestion solution, and at the same time, digestion agents are added in the digestion process and become potential interference factors in ammonium determination. Therefore, the detection accuracy of ammonium test kits needs to be evaluated first, including their anti-interference ability. The standard curve of ammonium was established by the test kit. When the ammonium concentration was 0.00–2.50 mg/L, the absorbance at 620 nm was linearly related to the ammonium concentration, the determination coefficient R² was 0.9995, and the detection limit of this method was 0.01 mg/L. The influences of temperature, pH value, and reaction time on the test kit method were discussed. The precision was 0.90–3.33%; the repeatability was 1.71–4.86%; and the recovery rate of tap water, river water, and sea water was controlled within 90–103%. The anti-interference ability of the evaluated test kit was better than that of the national standard detection method. The test kit, combined with sample pretreatment and protein conversion formula, was used to detect protein in different types of food (milk powder, rice flour, wheat flour, soy, banana, milk, fish food, chicken food, and dog food). The results showed that there were no significant differences (ρ > 0.05) between the national method and the test kit method. The ammonium ion test kit method shortened the determination time and had higher sensitivity, showing its potential for the rapid determination of food protein.     

鱼糜漂洗水中可溶蛋白的回收技术

对鱼糜漂洗水中可溶蛋白的综合回收技术情况进行了相关介绍, 主要包括絮凝沉淀法、等电点沉淀法、膜分离法、电阻加热法等, 这些技术的使用不仅实现了蛋白资源的再利用, 而且也减少了对环境的污染.     

饲料中补充晶体蛋氨酸和羟基蛋氨酸钙对罗氏沼虾幼虾生长性能的影响

饲料中添加30%鱼粉为对照组饲料和6组试验饲料(分别替代对照组中16.67%、33.33%和50.00%的鱼粉,同一鱼粉替代水平的2组分别添加晶体蛋氨酸和羟基蛋氨酸钙,使其蛋氨酸含量与对照组一致)喂养罗氏沼虾(初始体重为(0.29±0.04) g )10周,研究不同鱼粉替代水平下,分别添加晶体蛋氨酸和羟基蛋氨酸钙对罗氏沼虾幼虾生长性能和血清生化指标的影响.结果表明：复合蛋白源替代对照组16.67%鱼粉并补充羟基蛋氨酸钙组的增重率、特定生长率、蛋白质效率和饲料系数同对照组无显著差异(P>0.05);同一鱼粉替代水平下,羟基蛋氨酸钙组的增重率、特定生长率和蛋白质效率均显著高于晶体蛋氨酸组(P<0.05).血清生化组成的分析结果表明：血清总蛋白含量各处理组之间差异显著(P<0.05),对照组血清谷草转氨酶和谷丙转氨酶活力显著低于其他各组(P<0.05),其中同一替代水平下,饲料中添加羟基蛋氨酸钙组谷草转氨酶和谷丙转氨酶活力低于添加晶体蛋氨酸组.由此可见,与晶体蛋氨酸相比,羟基蛋氨酸钙能更有效提高罗氏沼虾生长性能和饲料利用效率.     

Effect of Coconut Protein and Xanthan Gum,Soybean Polysaccharide and Gelatin Interactions in Oil-Water Interface

We report on our study of the interactions between coconut protein extracted from coconut meat and three hydrocolloids (gelatin, xanthan gum, and soybean polysaccharide) and their interfacial adsorption and emulsification properties. We used Zeta potential, fluorescence spectroscopy scanning and ITC to investigate the interactions between a fixed concentration (1%) of coconut protein and varying concentrations of hydrocolloid. Through the interfacial tension and interfacial viscoelasticity, the interfacial properties of the hydrocolloid and coconut protein composite solution were explored. The physical stability of the corresponding emulsion is predicted through microstructure and stability analysis. Xanthan gum forms a flocculent complex with coconut protein under acidic conditions. Soy polysaccharides specifically bind to coconut protein. Under acidic conditions, this complex is stabilized through the steric hindrance of soy polysaccharides. Due to gelatin-coconut protein interactions, the isoelectric point of this complex changes. The interfacial tension results show that as time increases, the interfacial tensions of the three composite solutions decrease. The increase in the concentration of xanthan gum makes the interfacial tension decrease first and then increase. The addition of soybean polysaccharides reduces the interfacial tension of coconut protein. The addition of xanthan gum forms a stronger elastic interface film. Emulsion characterization showed that the gelatin-added system showed better stability. However, the addition of xanthan gum caused stratification quickly, and the addition of soybean polysaccharides also led to instability because the addition of polysaccharides led to a decrease in thermodynamic compatibility. This research lays the foundation for future research into coconut milk production technology.     

Zur Berechnung von Geometriefaktoren bei der Kernstrahlungsmessung

Der Geometriefaktor von radioaktiven umschlossenen oder offenen Strahlenquellen hängt bei der Messung mittels einer Kernstrahlungsmeßsonde von der räumlichen Anordnung der Strahlenquelle zu der strahlenexponierten wirksamen Fläche des Detektors und von der Geometrie der Strahlenquelle selbst ab. Fūr punktförmige Strahler in verschiedenen Positionen, Geraden, Kreisflächen und Zylinder wurde in möglichst einheitlicher Vorgehensweise die Berechnung der Geometriefaktoren bezüglich kreisförmiger ebener Detektionsflächen vorgenommen und rechentechnisch in Form von BESM 6-Algolprogrammen realisiert. Die Berechnungsergebnisse sind untereinander konsistent und wurden möglichst durch unabhängige Verfahren oder experimentelle Werte kontrolliert. Die Rechengenauigkeit kann gemäß den vorliegenden Anforderungen frei gewählt werden.     

Computerprogramm zur interaktiven Auswertung von 15N-tracerkinetischen Stoffwechselexperimenten

The theoretical concept of the computer program is based on the compartment theory for the 3-pool model using single pulse administration of the tracer. The code estimates the model parameters by means of the non-linear method of least squares fit under steady state conditions. Furthermore the parameters of the protein metabolism are calculated. The program works interactively and allows reading and modifying the experimental ¹⁵N tracer data via terminal and controlling the program.     

The Influence of the Flow-Pattern on Column Leaching Experiments: Formulation and Measurement by Radiotracer

The leaching of microconstituents from granular solid wastes is often studied by column experiments. The underlying assumption is that the flow is of the one-compartment or “backmix” type. The influence of small deviations from this ideal situation on the outcome of the leaching experiment depends slightly on the specific mass-transfer function of the trace involved. The deviation itself may be measured by a simple separate radiotracer experiment.     

Excitation of the Characteristic K Series Radiation,Coherent and Incoherent Scatter of Low Energy Gamma Rays

On the basis of a simplified mathematical model there is calculated the probability of a photon of characteristic K series radiation excited by a photon of low energy gamma radiation hitting the detector. There are also included the probabilities for coherently and incoherently scattered primary radiation considering electron binding energies.