β-Casein will chaperone β-lactoglobulin during nanofibril assembly,but prefers familiar company at high concentrations

Bovine β-casein behaves as a chaperone at neutral pH, i.e., it inhibits aggregation of unfolded proteins, but chaperone effects have not been investigated at acidic pH. We examined chaperone effects during heating at pH 2 and 80 °C for mixtures of 1% (w/v) β-lactoglobulin (β-Lg) and β-Lg:β-casein molar ratios of 1:0.0625 to 1:1. These conditions hydrolyse β-Lg into peptides that self-assemble into amyloid-like nanofibrils. Hydrolysis rates in mixed solutions were unchanged from single-protein controls, according to sodium dodecyl sulphate polyacrylamide gel electrophoresis. At ratios ≥1:0.125, β-casein slowed fibril growth in a concentration-independent way, according to Thioflavin T fluorescence. We observed twisted irregular fibrils coexisting with long semiflexible fibrils when β-casein was heated with β-Lg, using transmission electron microscopy. We hypothesise that β-casein monomers and peptides can interact with growing β-Lg nanofibrils or assemble into micelles, with the latter pathway predominating at high β-casein concentrations.     

A taxonomy-based approach to shed light on the babel of mathematical models for rice simulation

For most biophysical domains, differences in model structures are seldom quantified. Here, we used a taxonomy-based approach to characterise thirteen rice models. Classification keys and binary attributes for each key were identified, and models were categorised into five clusters using a binary similarity measure and the unweighted pair-group method with arithmetic mean. Principal component analysis was performed on model outputs at four sites. Results indicated that (i) differences in structure often resulted in similar predictions and (ii) similar structures can lead to large differences in model outputs. User subjectivity during calibration may have hidden expected relationships between model structure and behaviour. This explanation, if confirmed, highlights the need for shared protocols to reduce the degrees of freedom during calibration, and to limit, in turn, the risk that user subjectivity influences model performance.     

Fast total variation deconvolution for blurred image contaminated by Poisson noise

In this paper, we present a fast non-blind deconvolution method for restoring blurred images contaminated by Poisson noise. The problem is formulated by finding the minimizer of the negative logarithmic Poisson log-likelihood combined with the total variation (TV). To attack the challenging task, we adopt the well-known variable splitting and penalty technique to convert the problem into two easier sub-problems: one is a modified TV regularized deconvolution and the other is a simple convex optimization problem. Experimental results show that the proposed method runs very fast and the quality of the restored image is comparable with that of some state of the art methods.     

Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5–10 days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10 days. For longer times the profile stabilized, only the HAA content increased.A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.     

Removal of phenolic compounds in the production of high-quality canola protein isolates

Phenolic compounds are a major cause of the dark colour and undesirable taste of canola protein isolates. Based on our previous study of phenolic–protein interactions, a variety of treatments were tested for the removal of phenolic compounds from canola proteins. The combined use of these treatments was able to reduce the phenolic content of the products by 80–90%. Thus modified, the process produced two canola protein isolates, both of high protein content (>85%), low in phenolic acids (∼200 mg/100 g), and essentially free of condensed tannins. Colour measurement and sensory evaluation confirmed that the removal of phenolic compounds improved the colour and taste of canola protein isolates.     

不同采收期不同品种莲藕的营养品质变化规律及评价

目的 探究不同采收期不同品种莲藕的营养成分和活性成分的变化规律。方法 选取5个采收期的4个品种莲藕,测定蛋白质、淀粉等指标。采用主成分分析和聚类分析进行综合评价,并建立莲藕品质评价模型。结果 在采收期内,莲藕淀粉含量呈现先上升后下降再上升的趋势,可溶性糖的变化趋势与其相反;总酚含量整体呈现先上升后下降的趋势;蛋白质、膳食纤维等指标呈现不同的变化规律。主成分分析法提取出PC1、PC2、PC3 3个主成分因子,特征值依次为2.274、1.933、1.023,累积方差贡献率达87.170%。不溶性膳食纤维、可溶性膳食纤维、可溶性总糖、淀粉、总酚和总黄酮6个指标可以用来综合评价莲藕营养品质。综合评价发现, 9月采收的八月粉,10月的鄂莲6号,2月的鄂莲10号和鄂莲11号,营养品质较好,优于其他采收期。3月采收的4个品种莲藕的综合营养品质较低。结论 在采收期内, 4个品种莲藕的营养物质动态规律存在一定差异。基于主成分分析和聚类分析的分析方法能够科学评价不同采收期莲藕的综合营养品质,为莲藕育种、加工等提供支撑。     

Milling fractions fatty acid composition of common (Fagopyrum esculentum Moench) and tartary (Fagopyrum tataricum (L.) Gaertn) buckwheat

The objective of the present study was to determine the composition of fatty acids in the whole grain, hulls, bran and the light flour of common (Fagopyrum esculentum Moench) and Tartary (Fagopyrum tataricum (L.) Gaertn) buckwheat harvested in two consecutive years. Fatty acid composition for different milling fractions was determined as methyl esters using gas chromatography. Nine fatty acids were determined: lauric (12:0), myristic (14:0), palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (C18:1; n-9), linoleic (C18:2; n-6), α-linolenic (C18:3; n-3) and arachidic (20:0) acid. The highest relative content was determined for linoleic acid (from 35.54 to 47.57%), followed by oleic acid (from 20.96 to 40.76%) and palmitic acid (from 13.86 to 26.42%). The total fatty acid content was the highest in bran (up to 62.64 g/kg), followed by whole grains (up to 22.93 g/kg), light flour (up to 9.69 g/kg) and hulls (up to 5.87 g/kg). Saturated fatty acid content was the highest in the hulls and the lowest in the bran. Polyunsaturated fatty acid content was the highest in light flour. High positive correlations were found between saturated fatty acids with 18 carbon atoms or less.     

Heterostructured thin LaFeO3/g-C3N4 films for efficient photoelectrochemical hydrogen evolution

The deposition of LaFeO₃ at the surface of a graphitic carbon nitride (g-C₃N₄) film via magnetron sputtering followed by oxidation for photoelectrochemical (PEC) water splitting is reported. The LaFeO₃/g-C₃N₄ film was investigated by various characterization techniques including SEM, XRD, Raman spectroscopy, XPS and photo-electrochemical measurements. Our results show that the hydrogen production rate of a g-C₃N₄ film covered by a LaFeO₃ film, exhibiting both a thickness of ca. 50 nm, is of 10.8 μmol h⁻¹ cm⁻² under visible light irradiation. This value is ca. 70% higher than that measured for pure LaFeO₃ and g-C₃N₄ films and confirms the effective separation of electron-hole pairs at the interface of LaFeO₃/g-C₃N₄ films. Moreover, the LaFeO₃/g-C₃N₄ films were demonstrated to be stable and retained a high activity (ca. 70%) after the third reuse.