Advancement of food-derived mixed protein systems: Interactions,aggregations, and functional properties

Recently, interests in binary protein systems have been developed considerably ascribed to the sustainability, environment-friendly, rich in nutrition, low cost, and tunable mechanical properties of these systems. However, the molecular coalition is challenged by the complex mechanisms of interaction, aggregation, gelation, and emulsifying of the mixed system in which another protein is introduced. To overcome these fundamental difficulties and better modulate the structural and functional properties of binary systems, efforts have been steered to gain basic information regarding the underlying dynamics, theories, and physicochemical characteristics of mixed systems. Therefore, the present review provides an overview of the current studies on the behaviors of proteins in such systems and highlights shortcomings and future challenges when applied in scientific fields.     

Extraction, denaturation and hydrophobic Properties of Rice Flour Proteins

ABSTRACT: Rice proteins were extracted from defatted rice flour. Turbidity measurement of supernatants revealed isoelectric points of albumin (pH 4.1), globulin (pH 4.3 and pH 7.9), and glutelin (pH 4.8), at which they were precipitated with 82.3 to 93.2% recovery efficiency. Prolamin did not aggregate and precipitate upon pH adjustment, but was precipitated by acetone. Denaturation temperatures (73.3, 78.9, and 82.2 °C) as well as enthalpy values (2.88, 3.14, and 3.79 J/g), of albumin, globulin, and glutelin were different. Prolamin did not show any thermographic denaturation peak. Heat-denaturation of globulin and glutelin resulted in progressive increases in their surface hydrophobicities. Measurement of surface hydrophobicity would be an effective parameter to evaluate rice protein denaturation.     

Seasonal effects on storage proteins and gluten strength in four Swedish wheat cultivars

Weather variations in Sweden result in differences in the bread‐making quality of wheat. This study investigated whether the variation in bread‐making quality caused by yearly weather fluctuations could be explained by variation in protein composition, amount of storage proteins, protein subunits and protein groups, and relative amount and size distribution of polymeric proteins. Four spring wheat (Triticum aestivum L) cultivars grown in Sweden during three different years were investigated. Bread‐making quality and gluten strength were measured using baking and glutograph tests. SDS‐PAGE, SE‐HPLC, RP‐HPLC and ELISA were applied for investigation of protein composition, amount of storage proteins, protein subunits and protein groups, and relative amount and size distribution of polymeric proteins. The bread volume within cultivars varied depending on the cultivation year. The highest gluten strength was found in 1994 and the weakest in 1991. Variation in composition or relative amount of specific storage proteins, protein subunits or protein groups could not explain the variation in gluten strength between years. Instead, a significant relationship was found between the cultivation year and the percentage of unextractable polymeric protein in the total polymeric protein. The percentage of unextractable polymeric protein in the total polymeric protein was found to be highest during years when gluten strength was also high. © 2002 Society of Chemical Industry     

酶解程度对花生蛋白理化性质及功能特性的影响

研究了不同酶解程度对花生蛋白理化性质(包括分子质量、表面疏水性、巯基含量)及功能特性(溶解性、乳化性、抗氧化性)的影响。研究发现:花生蛋白进行不同酶解处理后,分子质量变小、表面疏水性变小、总巯基及暴露巯基呈现先减小后增大的趋势,同时酶解物的功能性质也发生了较大改变,如所有酶解物的溶解性提高,水解产物的乳化稳定性降低,DH5的乳化活性较PPI强,深度水解后DH10、DH15的乳化活性较PPI均明显下降,多酚含量跟DPPH自由基清除率正相关。研究结果为花生蛋白的改性提供了一定的数据支持。     

Influence of size distribution of proteins,thiol and disulfide content in whole wheat flour on rheological and chapati texture of Indian wheat varieties

The influence of protein composition, as measured by size-exclusion high performance liquid chromatography (SE-HPLC), on rheological properties and chapati texture was investigated in the whole wheat flours of eight Indian wheat cultivars grown at a single location. Proteins were extracted using two-step procedure: extraction with buffer containing 0.5% SDS (SDS buffer), followed by sonication. The results showed that SDS buffer extracted 72–90% of the total flour protein in different varieties and 7–11% protein was extracted from the remaining residues by sonication. The proteins extracted were fractionated by SE-HPLC into large polymeric proteins (>130 kDa), small polymeric proteins (80–130 kDa) and monomeric proteins (10–80 kDa). Total polymeric protein content in the flour protein showed a significant positive correlation with dough hardness (r = 0.71, p < 0.05) and positive correlation with chapati texture (r = 0.58, p < 0.05). Of the SDS extractable polymeric proteins, large polymeric protein in flour protein had significant positive correlation to dough hardness (r = 0.89, p < 0.05) and chapati cutting force, which reflects the chapati texture (r = 0.70, p < 0.05). Protein disulfide content showed positive correlation to dough hardness (r = 0.66, p < 0.05) and texture of chapati (r = 0.58, p < 0.05) while protein thiol content showed significant negative correlation to chapati texture (r = −0.77, p < 0.05). Thus, the results indicate that high proportion of SDS extractable large polymeric protein in flour protein increases the toughness of chapati texture while flours having high thiol content decrease the toughness of chapati.     

无花果内生菌WHG1及其胞外蛋白的分离鉴定和抗菌作用的研究

对无花果内生菌WHG1及其胞外蛋白进行分离鉴定,并探讨其抗菌作用。通过形态和生理生化特性及16sRNA序列分析方法鉴定菌株。采用滤纸片和牛津杯法抑菌实验研究其抗菌作用。用80%硫酸铵盐析,Sephadex G-100凝胶层析,DEAE-Sepharose Fast Flow离子交换色谱分离纯化内生菌的胞外抗菌蛋白,通过SDS-PAGE电泳测定其分子质量。WHG1为枯草芽孢杆菌(Bacillus subtilis),它对大肠埃希氏菌、金黄色葡萄球菌、沙门氏菌、酵母菌、黑曲霉等5种食源性致病菌和食品中常见污染菌均有较强的拮抗作用。WHG1胞外蛋白对大肠埃希氏菌和黑曲霉有较强的抗菌作用,该抗菌蛋白分子质量25～53ku。无花果内生菌WHG1具有产胞外抗菌蛋白的特性。     

HPLC-MS/MS-Detection of Caseins and Whey Proteins in Meat Products

Screening methods for the mass spectrometric detection of caseins and whey proteins in meat products have been developed. After tryptic digestion, two α-S1-casein and two β-lactoglobulin marker peptides were measured by HPLC-MS/MS. For matrix calibrations, emulsion-type sausages with different concentrations of milk and whey protein (ppm level) were produced. The limits of detection (LODs) were below 1 ppm for milk protein and about 3 ppm for whey protein. The determination coefficients for the correlation between peak area of the marker peptides and the concentrations of milk and whey proteins were R²≥0.9899.     

Texture and colour properties of proteins recovered from whole gutted silver carp (Hypophthalmichthys molitrix) using isoelectric solubilisation/precipitation

BACKGROUND: According to an FAO report, carp are the cheapest and by far the most commonly consumed fish in the world. Carp have minimal growth requirements, yet rapid growth rates. Although carp are generally considered unsuitable for human consumption in the USA, they have rapidly started populating major bodies of fresh water in the USA to the extent that commercial processing becomes of interest. However, typical mechanical means of meat recovery from carp are impractical owing to the bony nature of the carp carcass. Therefore the aim of the present study was to devise processing strategies to recover fish meat from carp that could be used in the development of human food products. RESULTS: Isoelectric solubilisation/precipitation at acidic and basic pH values was applied to whole gutted silver carp. Depending on the solubilisation pH, protein and fat recovery yields were approximately 420–660 and 800–950 g kg^?1 respectively. The process effectively removed impurities such as bones, scales, skin, fins, etc. from whole gutted carp. The proteins were concentrated to approximately 900 g kg^?1, while the fat was reduced by 970–990 g kg^?1. Functional additives (potato starch, beef plasma protein, transglutaminase and polyphosphate) improved (P < 0.05) the texture of carp protein‐based gels such that it was generally comparable to the texture of Alaska pollock surimi gels. Although titanium dioxide improved (P < 0.05) the whiteness of carp gels, it was lower (P < 0.05) than the whiteness of Alaska pollock surimi gels. CONCLUSION: Isoelectric solublisation/precipitation allows protein and lipid recovery from whole gutted carp. However, if the proteins are used as a gelling ingredient in fish food products, functional additives are recommended. Copyright © 2008 Society of Chemical Industry     

热激蛋白及其与果蔬的抗冷性关系

热激处理能够减缓果蔬采后低温贮藏时冷害的发生,热激蛋白的诱导是提高果蔬冷害耐受性机理中的一部分。本文介绍了热激蛋白及其与果蔬抗冷性关系的研究进展。     

Gel Point of Whey and Egg Proteins Using Dynamic Rheological Data

The gel point temperatures of coagulation type proteins and gelation type proteins were determined by extrapolating the rapidly rising phase of the storage modulus G’back to the temperature axis. The gelation onset. temperatures of the concentration-independent proteins oval-bumin, ovotransferrin, and BSA were 81°C, 62°C, and 75°, respectively, Gelation of whey protein isolate and egg white gels, both concentration-dependent, was presumably due to disulfide bonds formed by the interactions of the concentration-independent proteins: α-lac-talbumin and β-lactoglobulin, and ovalbumin and ovotransferrin, respectively. Moreover, the incipient gel temperature of whey proteins decreased when the concentration of whey proteins increased.     

Effects of enzymatic modification of milk proteins on flavour and textural qualities of set yoghurt

Milk proteins were enzymatically modified, using neutrase and trypsin immobilised on CM‐Sephadex C‐50, to the extent of 3, 4 and 5% degrees of hydrolysis. The neutrase‐treated milk and the trypsin‐treated milk were used separately to prepare set yoghurt. The set yoghurt prepared from neutrase‐treated milk showed an improvement in body, texture and flavour, a faster rate of acid development and a reduction in setting time compared with the control. However, the set yoghurt prepared from trypsin‐treated milk showed either a small or no improvement in textural and sensory properties. © 2000 Society of Chemical Industry     

Sensorial properties of red wine polyphenols: Astringency and bitterness

Polyphenols have been the subject of numerous research over the past years, being referred as the nutraceuticals of modern life. The healthy properties of these compounds have been associated to a natural chemoprevention of 21st century major diseases such as cancer and neurodegenerative diseases (e.g. Parkinson's and Alzheimer's). This association led to an increased consumption of foodstuffs rich in these compounds such as red wine. Related to the ingestion of polyphenols are the herein revised sensorial properties (astringency and bitterness) which are not still pleasant. This review intends to be an outline both at a sensory as a molecular level of the mechanisms underlying astringency and bitterness of polyphenols. Up-to-date knowledge of this matter is discussed in detail.     

The molecular biology of olfactory perception

This review discusses the anatomy of human odorant reception, with particular reference to the seven-helical transmembrane-protein superfamily of olfactory receptors, the concept of a novel multigene olfactory-receptor family, the location of the olfactory-receptor genes in the human genome and the characterization of the receptor proteins by cloning and overexpression. It then turns to the evidence for secondary message transduction following odorant binding, and the latest evidence on the structural analysis of G-protein coupled signalling as well as how the binding of odorant molecules to the transmembrane olfactory receptors is transmitted through the neural pathways to the brain, including the remarkable success in generating cDNA libraries from single neurons.     

白葡萄酒中不稳定蛋白的研究进展

白葡萄酒中的蛋白质不稳定是仅次于酒石酸不稳定的问题。主要阐述了白葡萄酒中不稳定蛋白的来源,蛋白质对白葡萄酒的影响及不稳定蛋白检测的方法;总结了近年来提高白葡萄酒中蛋白稳定的方法,并进一步进行了展望。以期为白葡萄酒品质的提高提供有效的技术指导。     

Antioxidative and antibacterial peptides derived from bovine milk proteins

The search for alternative preservatives is on the rise due to safety issues linked with the application of synthetic antioxidants and the extensive increase in bacterial resistance to several conventional antibiotics. Therefore, the quest for finding suitable alternatives including bioactive peptides has received attention. This article reports a comprehensive insight concerning antioxidative and antibacterial peptides derived from milk proteins, a prolific source of peptides having various bioactivities. Caseins and whey proteins have also been evaluated for antioxidative and antibacterial potential using the BIOPEP database. A notable number of potentially active peptides are present in milk proteins. Technological approaches are here reported for the production of these peptides. The findings of this review show potentiality of utilizing dairy derived antioxidative and antibacterial peptides in the development of a superior alternative to the current generation of preservatives and therapeutic agents, as well as a functional ingredient in dietetic or pharmaceutical applications.     

Enhanced thermal stability of soy protein particles by a combined treatment of microfluidic homogenisation and preheating

Recently, the pursuit of having a healthy diet has heightened the superiority of protein-enriched beverages; however, this is challenged by the heat-induced aggregation and gelation of proteins at high concentration. In this study, a facile and efficient strategy of combined preheating and microfluidic homogenisation treatment (CPMHT) was tested to enhance the heat stability of soy proteins (SPs). Results revealed that the CPMHT promoted the denaturation and unfolding of SPs, evidenced by the reduction of β-sheet content and a slight red shift of fluorescence intensity. Increasing the number of CPMHT cycle led to an apparent decrease in the surface hydrophobicity and total sulfhydryl groups of soy proteins. In addition, when the suspensions (10% (w/v)) of modified soy proteins at higher CPMHT cycle were reheated at 100 °C for 30 min, no gelation was found, along with lower viscosities and higher flow behaviour index. The present study provides an approaching to enhance the heat stability of soy proteins by CPMHT, which might expand the application of soy proteins in protein-enriched beverages.