Heat-Induced Aggregation of Egg White Proteins as Studied by Vertical Flat-Sheet Polyacrylamide Gel Electrophoresis

Heat-induced aggregation of proteins in egg white was investigated by a vertical flat-sheet polyacrylamide gel electrophoretic method. The fractional and step-wise aggregation of egg white proteins was caused by heating. Even with a heating time of 120 min, ovalbumin and globulins Al and A2 failed to aggregate in egg white (pH 7 and 9) at 70°C, and ovotransferrin and ovomucoid also did not aggregate in egg white at 60°C (pH 9) and 76°C (pH 7 and 9), respectively. The ovoinhibitor was much more unstable than ovomucoid under heat-treatment, and the time dependency of heat-induced aggregation of flavoprotein was greater than those of the other proteins in egg white.     

Multilayer polarization elements and their applications to polarimetric studies in vacuum ultraviolet and soft X-ray regions

Multilayer polarization elements and their applications to polarimetric studies in 20～400 eV region are mainly reviewed.General principle of selecting material combinations to get high linear polarizance multilayers of reflection type is given with practical examples,with periodic or non-periodic layer structures depending on the usage.Transmission type is introduced as linear polarizer and phase shifter.Their applications include polarization diagnosis of laboratory optical systems and synchrotron radiation beamlines of linear and circular polarization,magnetic rotation experiments such as Faraday rotation and magnetic Kerr rotation on magnetic films and multilayers,and ellipsometry to measure optical constants of thin films precisely.Polarization analysis of soft X-ray fluorescence using multilayer-coated grating is also mentioned.Finally this review is summarized with outlook of further developments.     

Gelation of Egg White Proteins as Affected by Combined Heating and Freezing

Combined effects of preheating (60°C, 0 ～ 30 min) and freezing (– 10 or –20°C, 20 hr) on the gelation of dried egg white induced by reheating (80°C, 30 min) were examined in comparison with those of refrigerating (5°C, 20 hr). Refrigeration consistently induced harder gels, while freezing resulted in either harder or softer gels. Results of soluble protein content, turbidity, SDS-PAGE and gel filtration indicated that the unfolded and aggregated levels of ovotransferrin, caused by the cooperative effects of preheating and freezing or refrigerating, mainly determined the characteristics of gel properties.     

EFFECTS OF TEXTURAL CHANGES IN COOKED APPLES ON THE HUMAN BITE, AND INSTRUMENTAL TESTS

A multiple-point sheet sensor was used to measure the bite force applied to raw and cooked apple specimens during the first bite with incisors. Wedge penetration tests were compared with human bite measurements on the same samples. The shape of the force-time curves during biting of cooked apples clearly differed from that for raw apples. The first curve of cooked apple biting became jagged, and the maximum force was reduced. The second curve emerged following the first curve in most subjects as a characteristic feature of cooked apple biting, whereas it was not seen in the bite curve of a raw specimen or the wedge penetration curve of a cooked specimen. The maximum force for tissue fracture decreased for cooked apples, but the duration of biting increased. No adequate counterparts for the impulse of biting could be obtained from the load-displacement curves of the wedge penetration tests. The existence of parameters only measurable by bite tests and not by mechanical tests suggests the necessity of directly measuring the human bite.     

框架边节点斜压机构混凝土强度有效因数解析

利用斜压-桁架模型对以往35个剪切破坏型以及6个梁屈服后剪切破坏型钢筋混凝土框架边节点试件抗剪强度进行解析.探讨了混凝土抗压强度、柱轴压比、节点水平箍筋量、节点竖向箍筋量以及斜压机构倾角等参数对斜压机构混凝土强度有效因数p的影响.研究结果表明,混凝土强度越高,最大荷载时p值衰减率越大;普通强度混凝土时节点箍筋对p值衰减的抑制效果比高强度混凝土时明显;节点箍筋配箍率小于0.3%范围内斜压机构承担总剪力的80%以上.根据对p值的解析结果提出了针对节点强度的计算式,计算值与试验结果吻合.     

Enthalpy of Denaturation and Surface Functional Properties of Heated Egg White Proteins in the Dry State

The enthalpy of denaturation (ΔH) and surface properties of proteins were related to elucidate the mechanisms of foaming and emulsifying properties by using various heated egg white proteins in the dry state. Foaming and emulsifying properties of all sample proteins were greatly increased with a decrease in the enthalpy of denaturation as determined by differential scanning calorimetry analysis. In plots, foaming and emulsifying properties correlated linearly with ΔH values for various dry-heated egg white proteins. Thus, the enthalpy of denaturation of proteins seemed to be a significant structural factor governing surface functional properties.     

Effects of Ca++, Mg++ and Na+ on Heat Aggregation of Whey Protein Concentrates

Effect of Ca⁺⁺ on the heat aggregation of whey protein concentrates (WPC) was compared with that of Na⁺ and Mg⁺⁺. On the alkaline side of the isoelectric zone, aggregation of WPC was increased by the addition of CaCl₂, MgCl₂ or NaCl, among which CaCl₂ showed the greatest effect. The denaturation temperature of WPC determined by differential scanning calorimetry significantly decreased in the presence of CaCl₂ or MgCl₂, but increased slightly in the presence of NaCl. In the electrophoretic patterns of heated WPC, the most sensitive protein to Ca⁺⁺ was β-lactoglobulin.     

Microbial Biosensor System for Rapid Determination of Vitamin B6

A microbial biosensor system was based on an immobilized microorganism (Succharomyces uvarum 4288 ATCC9080) and Clark-type oxygen electrode consisting of a platinum cathode, lead anode, alkaline electrolyte, and an oxygen permeable Teflon membrane. The determination was based on the respiratory activity of the microorganism in presence of vitamin B₆. Optimum conditions were: concentration of immobilized cells on membrane: OD₆₆₀, = 0.05, temperature: 30°C. When oxygen permeable Teflon membranes (0.5 mil and 2.0 mil) were employed, relationships between vitamin B₆, (pyridoxine) and current decrease were linear in the range of 0.5 ng/mL-2.5 ng/mL and 2.5 ng/mL-12.5 ng/mL, respectively. One assay could be completed within 15 min. This system provided rapid and simple determinations of vitamin B₆ in marine products with good correlation to traditional microbial assay values.     

Functional and Sensory Properties of Meat Emulsions Produced by using Enzymatically Modified Gelatin

Mettwurst and Bologna sausage were produced from pork using enzymatically modified gelatin (EMG-8), which had been produced with covalent attachment of L-leucine n-octyl ester. EMG-8 improved spreadability, smoothness and softness of the Mettwurst. With the addition of EMG-8, the texture of the Bologna sausage was kept soft over a 1 to 7 day period of storage at 4°C or 2 to 4 weeks of storage at -20°C. Microscopic observation showed that fat globules in the Bologna sausage produced with EMG-8 were more homogeneously distributed than those in a control Bologna sausage.     

Combined Effect of pH and Sodium Chloride on the Heat-induced Aggregation of Whole Egg Proteins

Heat-induced aggregation of whole egg proteins through various treatment combinations ranging from 70–85°C, pH 2.0–9.0, and NaCl concentrations of 0–3%, was investigated using multiple regression analysis and vertical flat-sheet polyacrylamide gel electrophoresis. The importance of single variable was in the order of temperature, pH and NaCl concentration, and the combined variable of pH and NaCl had a highly significant (p<0.001) effect on soluble protein content. From the fractional and step-wise aggregation appearances of whole egg proteins in the electrophoretic patterns, the heat stability of main proteins was considered to increase as pH (pH>5) and NaCl concentration increased.