Effect of thermal treatments on functional properties of cress seed (Lepidium sativum) and xanthan gums: A comparative study

Foods are generally subjected to thermal treatments during processing operations, which affect on the functional properties of hydrocolloid solutions. In this paper, the effect of different thermal conditions (60 °C-30 min, 80 °C-23 min, 100 °C-18 min and 121 °C-15 min) on functional properties (rheological, emulsifying and foaming properties) of cress seed gum and xanthan gum were investigated. The results demonstrated that cress seed gum solutions had desirable rheological, emulsifying and foaming properties. When the hydrocolloid samples were heated, an irreversible increase in viscosity of cress seed gum solutions was observed and as a result, the emulsification and foaming properties improved. Whereas, xanthan gum would not have the ability to stand against heat treatment and its viscosity decreased. Nevertheless, the viscosity values of xanthan gum solutions were always higher than cress seed gum in all conditions.     

循环冻融对蛋清蛋白性质的影响

目的：研究循环冻融对蛋清蛋白加工特性与结构的影响。方法：对蛋清循环冻融0～5?次,分析其冻融后的功能性、理化特性、流变特点和二级结构的变化。结果：适当的循环冻融能够提高蛋清的凝胶及泡沫性质。循环冻融使蛋清蛋白疏水基团暴露,蛋白质结构伸展,形成分子间聚集体。动态流变结果表明循环冻融增加了蛋清的弹性模量与黏性模量。冻融过程中,蛋清蛋白的α-螺旋和β-转角含量减少,β-折叠和无规则卷曲含量增加,空间无序性更强。循环冻融能够改变蛋清蛋白的结构与性质,可应用于蛋清加工过程。     

Novel Radiofrequency‐Assisted Thermal Processing Improves the Gelling Properties of Standard Egg White Powder

Effect of radiofrequency (RF)‐assisted thermal processing on quality and functional properties of high‐foaming standard egg white powder (std. EWP, pH approximately 7.0) was investigated and compared with traditional processing (heat treatment in a hot room at 58 °C for at least 14 d). The RF‐assisted thermal treatments were selected to meet the pasteurization requirements and to improve the functional properties of the std. EWP. The treatment conditions were: RF heating to 60, 70, 80, and 90 °C followed by holding in a hot air oven at those temperatures for different periods ranging from 4 h at 90 °C to 72 h at 60 °C. The quality (color and solubility) and functional properties (foaming properties: foaming capacity and foam stability; and gelling properties: water holding capacity and gel‐firmness) of the std. EWP were investigated. RF‐assisted thermal processing did not affect the color and solubility of std. EWP at any of the treatment conditions. In general, the foaming and gelling properties of RF‐assisted thermally processed std. EWP increased with an increase in temperature and treatment duration. The optimal RF‐assisted treatment conditions to produce std. EWP with similar functional properties as the traditionally processed (hot room processed) std. EWP were 90 °C for ≥8 h. These optimal conditions were similar to those for high gel egg white powder (HG‐EWP, pH approximately 9.5). The RF‐assisted thermal pasteurization improved the gelling properties of std. EWP to the levels of HG‐EWP, leading to newer applications of this functionally improved safe product. The RF‐assisted thermal processing allows the processor to produce a HG‐EWP from std. EWP subsequent to processing while simultaneously pasteurizing the product, thus assuring the product safety.     

Modification of functional,rheological and structural characteristics of myofibrillar proteins by high-intensity ultrasonic and papain treatment

The effects of sonication duration (15 and 30 min) and papain enzyme treatments on the conformational, physicochemical and functional traits of myofibrillar proteins (MPs) were addressed in this study. As the ultrasound duration was increased, the water holding capacity (WHC), solubility, foaming and emulsifying properties were improved as a result of the changes in the particles size distribution and zeta potential. Our results indicated that the turbulence force caused increments in the surface hydrophobicity and significant changes in the secondary structure. Also, the rheological properties were influenced by both cavitation force and papain treatment. According to the observations, the samples treated with sonication (for 15 and 30 min) and enzyme were more elastic with higher viscosity, as compared to the control. Compared with the control, enzymolyzed samples indicated better functionality. Moreover, papain treatment led to the increase of the hydrophobicity groups on the surface of proteins and the decrease of the amount of α-helix and β-sheet structures. It was noteworthy that the most changes in the structure and techno-functionality of myofibrillar proteins were observed for the sample affected by the simultaneous application of papain treatment and 15 min sonication. The highest values in the surface hydrophobicity, specific surface area, net charge, storage modulus, solubility and WHC belonged to this sample. However, enzyme-modified samples exposed to the longer sonication time (30 min) demonstrated reductions in solubility, WHC and surface hydrophobicity, as well as increases in the particle size distribution and protein turbidity.     

Structural characterization and functional properties of egg white protein treated by electron beam irradiation

This study investigated the functional properties and structural characteristics of egg white protein (EWP) powder treated by electron beam irradiation (EBI) at the doses of 5, 10, 20, 30, 50, 70 and 100 kGy. In comparison with the untreated sample (0 kGy), the EBI-induced EWP showed generally better solubility and higher antioxidant capacity by ABTS•⁺ radical scavenging assay. Furthermore, the emulsifying activity index of EBI-induced EWP increased with increased EBI dose, reaching the maximum value of 15.8 ± 0.4 m²/g at 100 kGy. The emulsifying stability index and ϛ-potential of EBI-induced EWP showed fluctuating tendencies. These functional property changes of protein were attributed to the conformational changes caused by EBI. SDS-PAGE patterns confirmed that high-dose EBI would result in protein depolymerization to low-mass molecules at 11 kDa, contributing to the increased solubility. Circular dichroism data demonstrated that EBI-induced EWP exhibited partial denaturation and a flexible structure, which was responsible for the improved emulsifying properties. Fluorescence spectra revealed that high EBI doses led to an increase in the polar environment around tryptophan, which could enhance the solubility and antioxidant activity of EWP. In addition, high EBI doses decreased the content of free and total sulphydryl groups, and changed the intermolecular forces of protein, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. These findings can provide solid support for practical applications of EBI technology in EWP food processing.     

干燥方式对蛋清蛋白理化性质和功能特性的影响

为探究干燥方式对蛋清蛋白（egg white protein,EWP）功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液（EWP-C）相比,喷雾干燥使蛋清蛋白（EWP-P）的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白（EWP-D）分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D（接触角为65.97°）,表明喷雾干燥能显著提高蛋白的疏水性（P<0.05）。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。     

Formation of conjugates between β-lactoglobulin and allyl isothiocyanate: Effect on protein heat aggregation,foaming and emulsifying properties

Whey proteins are widely used food ingredients due to their nutritional and functional properties (gelling, emulsifying, foaming). Owning to their structure (free thiol group, lysine residues, hydrophobic pocket), they can also be used as carriers for bioactives. In this study, conjugates between β-lactoglobulin (β-lg), and a bioactive metabolite from Brassicaceae vegetables, allyl isothiocyanate (AITC) were formed. Heat aggregation behavior (85 °C, 15 min), foaming and emulsifying properties of conjugates, at pH 4.0 and 7.1, were evaluated.     

Effect of high‐pressure treatment on trypsin hydrolysis and antioxidant activity of egg white proteins

High‐pressure processing (HPP) is known to modify the functional properties of the proteins by changing its structure that can lead to protein denaturation, aggregation or gelation, depending on the protein system and the applied pressure. The potential to modify functional properties of protein and their products using HPP has been explored widely in last decade. In this study, the effect of HPP on the degree of trypsin hydrolysis (DTH) and antioxidant activity (AA) of egg white protein (EWP) and freeze‐dried egg white powder (DEW) was evaluated. EWP and DEW were subjected to trypsin hydrolysis for up to 120 min, with and without HP treatments [pressure level (350–550 MPa) and treatment time (5–15 min)]. HP treatment caused substantial increase in DTH of EWP and DEW, increasing it from 2.78% (EWP control) and 2.20% (DEW control) to 11.3% (HP‐treated EWP) and 8.41% (HP‐treated DEW), respectively. HP treatment also had an emphatic effect on AA of EWP (concentration 10% w/v) with AA increasing from 9.34% for control EWP to 19.0% after 5‐min HP treatment at 350 MPa and 25.00% after the same treatment at 550 MPa. Overall, HPP caused an increase in DTH and AA of EWP and DEW over the control. SDS‐PAGE and differential scanning calorimetric studies confirmed the effect of HP on the hydrolysis of egg proteins.     

高密度CO_2对全蛋液功能性质的影响

鸡蛋除具有很高的营养价值外,还有重要的功能特性如乳化性、起泡性和凝胶性等,文中研究了高密度CO2对全蛋液功能性质的影响。结果表明:全蛋液的功能性质随处理压力增加而增加,当处理压力大于15 MPa时,全蛋液的溶解性、起泡性、凝胶性及表面疏水性下降;全蛋液的乳化性在处理压力大于10 MPa时下降。全蛋液的功能性质随处理时间的延长而增加,当处理时间超过20 min时,全蛋液的溶解性、起泡性和表面疏水性下降;全蛋液的乳化性及凝胶性在处理时间超过25 min时下降。     

鸡蛋清蛋白水解物的物化及功能性质的研究

蛋清蛋白质溶解性欠佳且容易起泡,使其应用受限。本文利用Alcalase酶解鸡蛋蛋清蛋白制取水解度为5~15%的酶解物并对酶解物的理化性质和功能性质进行了表征。测定性质包括乳化性、起泡性及稳定性以及溶解性、表面疏水性。所有酶解产物具有较低的表面疏水性,水解大大提高了溶解度,当水解度15%时最大值为89%,但乳化性有所降低,起泡性及稳定性也大约下降了40%。     

Influence of atmospheric-pressure cold plasma-induced oxidation on the structure and functional properties of egg white protein

This study examined the effects of atmospheric-pressure cold plasma (ACP) on the structure and functional properties of egg white protein (EWP). Egg white solution was treated with ACP for 0, 10, 20, 30, and 40 min. The structural unfolding of EWP was confirmed as the exposed free SH group content and surface hydrophobicity increased during the 30 min treatment; however, 40 min of ACP treatment showed the opposite tendency, suggesting the formation of protein aggregates. The emulsion stability of egg white emulsions was the highest at 30 min but decreased again at 40 min. In addition, the proportion of large droplets decreased as the treatment time increased up to 30 min. As a result, moderate oxidation was induced during 30 min of ACP treatment, which could contribute to the enhancement of functional properties of EWP. However, excessive oxidation caused by further ACP treatment negatively affected the enhanced functional properties.Industrial relevanceEgg whites are used as functional ingredients for a variety of food products, so the quality and functionality of egg whites can directly affect the productivity of the final products. The present study suggests the moderate oxidation of egg white protein induced by atmospheric-pressure cold plasma, which could contribute to the enhancement of functional properties. These applied studies can serve as a cornerstone for the establishment of advanced oxidation techniques that can enhance the functionality of egg whites without chemical additives, and consequently contribute to the improvement of food quality and productivity.     

两种不同干燥方式对不同预处理方式的脱盐鸭蛋清品质的影响

采用真空冷冻干燥和负压微波喷动干燥两种干燥方式,对经不同预处理的咸鸭蛋清进行干燥制粉,以鲜鸭蛋清为对照,研究不同干燥方式咸鸭蛋清脱盐前后的功能特性。产品的质量主要通过色差、表观密度、凝胶性、起泡性及泡沫稳定性、乳化性及乳化稳定性等方面来衡量。实验结果表明:当负压微波喷动干燥条件为干燥腔压力80 Pa,脉冲压力800 Pa,微波功率0.1~0.6 kW,每间隔10 min脉冲2 s;真空冷冻干燥条件为真空泵压力10 kPa,温度为50℃,加热功率为350 W,干燥时间为10 h时,负压微波喷动干燥产品的理化特性优于真空冷冻干燥产品的理化特性(色泽、表观密度值、硬度、起泡性和乳化性等),咸鸭蛋清的最佳干燥方式是负压微波喷动干燥(PSMFD);经超声波预处理后PSMFD的蛋清粉具有最好的色泽,较好的表观密度值(0.333 kg/dm3)、较小的硬度(831.251 g)、较高的起泡性(86.7%)和乳化性(0.540 4)、较好的起泡稳定性(93.3%)和乳化稳定性(26.48 min)。     

蛋清肽的抗氧化稳定性与功能特性

选用胃蛋白酶水解冻干蛋清制得蛋清肽,测定蛋清肽的抗氧化稳定性及功能特性。研究温度和pH值对蛋清肽抗氧化稳定性的影响以及蛋清肽的乳化性、吸水能力和吸油能力。结果表明：随着蛋清肽质量浓度的增加其清除羟自由基( ·OH)、超氧阴离子自由基(O2－ ·)及DPPH自由基的能力均随之增加;温度与pH值对蛋清肽的抗氧化活性影响较大,在pH12.0条件下存放4h后其抗氧化活性消失;蛋清肽具有较好的乳化能力、乳化稳定性、吸油和吸水能力,这些均有利于其在食品和化妆品行业中的应用。     

Food properties of egg white protein modified by rare ketohexoses through Maillard reaction

d ‐psicose (Psi), a rare ketohexose, improves food properties of proteins through the Maillard reaction (MR) much more than d ‐fructose (Fru). This encouraged us to investigate the improvement of food properties of proteins through MR with various rare ketohexoses (d ‐psicose, Psi; d ‐tagatose, Tag; and d ‐sorbose, Sor). The food properties of egg white protein (EWP) after reaction with Psi, Tag, Sor and Fru were studied. Psi‐EWP (43.3 μmol TE g^?1) and Tag‐EWP (43.4 μmol TE g^?1) had the highest antioxidant activity, followed by Sor‐EWP (38.4 μmol TE g^?1) and Fru‐EWP (38.9 μmol TE g^?1). MR enhanced the breaking stress of heat‐induced EWP gels by 224–267%. The breaking stress was higher in Psi‐EWP (81.1 kN m^?2), Tag‐EWP (80.0 kN m^?2) and Sor‐EWP (77.8 kN m^?2) than in Fru‐EWP (71.6 kN m^?2). Furthermore, the foaming capacity was highest in Psi‐EWP and Sor‐EWP. Rare ketohexoses improved food properties of EWP more than Fru. Overall, Psi offered the greatest functional improvement.     

Effect of cavitation jet on the structural,emulsifying properties and rheological properties of soybean protein-oxidised aggregates

The objective of this study was to investigate the effects of cavitation jets on the structural, emulsifying and rheological properties of soybean protein oxidation aggregates. The results showed that oxidation might induce the formation of larger particle sizes and molecular weight protein aggregates and the decrease of emulsifying properties. The cavitation jet at a short treatment time (<6 min) broke down the disulphide bonds and protein skeleton structures, which reduced the aggregate sizes and molecular weights and increased the emulsion activities, emulsion stabilities, apparent viscosity and elastic modulus. The cavitation jet at a long treatment time (>6 min) supported disulphide bond formation among molecules by intermolecular interactions to form protein aggregates. In addition, the skeleton structure showed cross-linking aggregation. This increased the particle sizes and molecular weights and reduced the emulsion properties, consistency index K and elastic modulus. The findings showed that a cavitation jet at 6 min on oxidised aggregates of soybean protein might enhance the structural, emulsifying and rheological characteristics for the industry.     

Physicochemical,nutritional and functional properties of marama bean flour

Marama bean is a protein-rich, underutilised, drought-tolerant legume in sub-Saharan Africa. Its utilisation may be increased through value addition into protein-rich flours. Defatted flour from unheated and dry-heated (150 °C/20 min) whole marama beans (UMF and HMF) were analysed for physicochemical and protein-based functional properties. Heating significantly increased in vitro protein digestibility of marama bean flour. Of functional importance are the high levels of tyrosine present in marama bean flours. Heating significantly reduced protein solubility and emulsifying capacity of marama bean flours whilst water absorption capacity was improved. Foaming capacity was not affected by heating. UMF could be useful in food systems requiring high emulsifying capacity, but would not be suitable for applications requiring high water absorption and foaming capacity. Due to its high protein contents, marama bean flour could be used to increase the protein quality of cereal-based foods to help alleviate protein-energy nutrition in the region.     

Hyperbaric storage of egg white at room temperature: Effects on hygienic properties,protein structure and technological functionality

Fresh hen (Gallus gallus domesticus) egg white was submitted to hyperbaric storage at 200 MPa at room temperature for up to 28 days. Control samples were stored at 4 °C and 0.1 MPa. Storage conditions were compared for antimicrobial capacity towards inoculated (circa 4 log CFU g⁻¹) Staphylococcus aureus and Salmonella enterica, and changes in physical, structural and functional properties. S. enterica was completely inactivated within 3 h of hyperbaric storage. Prolonged hyperbaric storage promoted slight egg white yellowing, probably due to non-enzymatic browning or riboflavin-protein decomplexation, and induced minor changes in egg white protein structure. Partial conversion of ovalbumin into S-ovalbumin led to slightly decreased gelling capacity. Pressurized egg white proteins also resulted slightly compressed and electrically stabilized, becoming more prone to solvent interactions. Based on these effects, viscosity of egg white increased almost 4-fold and foaming capacity increased by circa 35%. Our work demonstrated for the first time that hyperbaric storage guarantees safety and hygiene of egg white without detriment to its technological functionality.Industrial relevanceHyperbaric storage could represent an interesting alternative to refrigeration due to its capability to preserve food hygienic properties. Concomitantly, it could be used to pasteurize and even enhance technological functionality of protein-rich food ingredients. These goals could be achieved with negligible energetic consumption if working units were made viable for industrial application.     

超声处理对蛋清蛋白结构性质及蛋清液起泡性的影响

研究脉冲式超声处理对蛋清液拉曼光谱、内源性荧光光谱、静态流变学性质、粒径和理化结构的影响,结合起泡性的变化进行相关性分析。研究发现,超声处理能够改变蛋清蛋白二硫键构象,降低蛋清液黏度,减少总巯基含量,对无规卷曲、β-转角含量和酪氨酸残基峰强比（I850/I830）影响较小,蛋清液依旧为假塑性流体。在超声处理15 min内,蛋清蛋白质粒径、表面巯基含量、热变性焓（ΔH）、α-螺旋和β-折叠含量逐渐减少,内源性荧光强度和表面疏水性逐渐增强,色氨酸残基趋向于“暴露的”展开形式;起泡性得到改善,且泡沫体积小,呈均匀紧密的排列,泡沫稳定性小幅降低。随着超声时间的延长,β-折叠含量继续降低,粒径、表面巯基含量、ΔH、α-螺旋含量、色氨酸残基峰强比（I1 363/I1 338）、内源性荧光强度和表面疏水性呈现不同的变化趋势,起泡性逐渐降低,但泡沫稳定性有所升高。相关性分析表明,起泡性与I1 363/I1 338、表面疏水性呈正相关,与ΔH、平均粒径、α-螺旋含量和表面巯基含量呈负相关,泡沫稳定性与表面疏水性呈负相关。     

Amino acid profile,protein digestibility,thermal and functional properties of Conophor nut (Tetracarpidium conophorum) defatted flour,protein concentrate and isolates

Functional properties, amino acid compositions, in vitro protein digestibility, electrophoretic and thermal characteristics of conophor defatted flour (CDF), conophor protein concentrate (CPC), isoelectric protein isolate (CII) and neutral protein isolate (CNI) were evaluated. The isolates (CII and CNI) showed significantly lower (P < 0.05) water and oil absorption capacities, emulsifying and gelling capacities, but higher emulsion stability and foaming capacity. In vitro protein digestibility, enthalpy and denaturation temperature varied between 52.28% and 73.4%, 1.62–4.04 J g^?1 protein and 79.7–89.3 °C, respectively. The native proteins were comprised of subunits with molecular weights ranging between 15.3 and 129.3 kDa. The major amino acids in all the samples were aspartic acid, glutamic acid and arginine, whereas the percentages of essential amino acids in CDF, CPC, CII and CNI were 39.35%, 40.46%, 44.54% and 46.04%, respectively. Conophor protein products could be used as functional ingredients in food formulations and for enriching low quality protein diets.     

Novel,non-thermal hydrodynamic cavitation of orange juice: Effects on physical properties and stability of bioactive compounds

Effect of hydrodynamic cavitation (HC) at pressure 3–15 bar and treatment time5–25 min on physical and chemical qualities of orange juice was investigated. Processing parameters were optimized on the basis of retention of vitamin C and antioxidant activity; inactivation of pectin methyl esterases (PME) and peroxidase (POD) enzyme and stability of pH, °Brix, viscosity, titratable acidity and total color difference. HC of orange juice at 5 bar 15 min and 13 bar 10 min resulted into maximal overall desirability at 0.52 and 0.40 respectively. No significant change in °Brix, pH, titratable acidity for fresh and cavitated orange juice was observed. Only 21% and 13% of reduction in PME and POD respectively was recorded. A 94% and 91% of antioxidant activity and vitamin C retention was noted in both optimized samples. This study demonstrated that HC can produce orange juice more economically with better physical properties and nutritional value.Industrial relevanceThe demand for more natural, preservative free with highest nutritional bioactive containing juices has created a need of non-thermal processing. Hydrodynamic cavitation (HC) processing is novel, emerging and under explored technology for fruit juices. HC due to the formation of cavities and shock waves causes enzyme and microbial inactivation at low temperature while retaining natural bioactives with fresh-like organoleptic characteristics. It is believed worldwide that non thermal technologies like HC will be among the most cost effective, scalable and impactful liquid food processing technologies in the coming decades especially for commercial products.