Effect of alkaline extraction on the structure of the protein of quinoa (Chenopodium quinoa Willd.) and its influence on film formation

It is important to produce hydrophobic edible protein films for use in foods. The aim of this study was to evaluate the effect of alkaline extraction of quinoa proteins (QP) on the structure and their film‐forming ability without plasticiser. QP were extracted between pH 8 to 12, and their structure was evaluated by PAGE‐SDS, size‐exclusion HPLC light scattering, fluorescence spectroscopy and SH and SS. Film was characterised by FTIR, SEM, tensile strength, barrier and colour. Structural changes of QP showing that alkalinisation over pH 10 produce significant denaturation/aggregation/dissociation structural changes in QP. pH 12 was the condition to form a film (film₁₂). FTIR showed hydrogen bonds and hydrophobic film interactions. Film₁₂ had 16.6 ± 3.8% elongation and 15.7 ± 1.1 MPa tensile strength, and water vapour permeability was 5.18 ± 0.38 g mm m^?2 day^?1 kPa^?1. Film₁₂ had a brownish colour. A high degree of denaturation/aggregation/dissociation of QP structure is required to form a film without plasticiser.     

藜麦皂苷研究进展

藜麦(Chenopodium quinoa Willd.)是南美洲特有的一种植物,其叶片、花、果实、籽实和种皮中富含皂苷,藜麦皂苷是一种苦味物质和抗营养因子。目前常用的皂苷提取方法主要有溶剂提取法、酸碱水解法、沉淀法、超临界CO_2法及超声波萃取法等。近年来的研究表明,藜麦皂苷具有抗氧化、抗肿瘤、抑菌、免疫调节等药理活性,这些特性都使藜麦皂苷成为医学、保健品、食品等行业的重点研究对象。本文主要对藜麦皂苷的研究现状、结构组成、提取方法、分离纯化、分析测定、生物活性、以及环境对藜麦皂苷的影响进行了概述,以期为藜麦的进一步研究开发提供参考。     

Physicochemical and rheological properties of purees based on Mafafa (Xanthosoma robustum) and quinoa (Chenopodium quinoa Willd.) with the addition of cryoprotectants

Growing interest in processed frozen products with similar characteristics to natural products has generated the study of new products in the food industry field. The characteristics of each matrix, the process of elaboration, composition, and structure of the additives and the interactions amongst these modify the food's texture, structure, physical and sensory properties and, hence, interfere directly with consumer acceptance. This research studied the effect of adding cryoprotectors during frozen storage on the rheological, physicochemical, structural, and microbiological properties in a Mafafa‐quinoa‐olive oil puree. To carry out the study, the rheological properties were determined through dynamic oscillatory tests and in steady state; likewise, the physicochemical properties (humidity, color, pH, and syneresis) were analyzed. Regarding physicochemical properties, the humidity content in the purees formulated varied between 57 and 74%, without important variation (p > .05) with respect to the formulation, however, in the storage during the freezing/thawing process, this parameter diminished in greater proportion in those purees containing carrageenan as cryoconservant. Both the addition of cryoconservants and the storage time affected significantly (p < .05) the puree's syneresis, with the degree of exudation being lower in the formulation containing xanthan gum at 1% w/w. During the freezing/thawing process, decreased apparent viscosity was noted. Additionally, the analysis of the viscoelastic properties of the purees evidences that already described, given that a significant effect (p < .05) was observed of the formulation of purees in the elastic component G′, in contrast with a notable decrease in the viscous component G″.     

不同热处理对藜麦蛋白质营养品质的影响

本研究分别采用微波、蒸制、煮制和烘焙对藜麦分离蛋白（QPI）进行热处理,并评价处理前后QPI氨基酸组成、体外消化特性和生理活性变化。结果表明：蒸制、煮制和烘焙处理分别使QPI中必需氨基酸总量降低了2.93%、8.68%和1.91%（p<0.05）,同时改变了QPI中氨基酸的组成及评分;微波和煮制处理后QPI最终消化率分别提高至77.10%和82.86%（p<0.05）;在测定浓度范围内,各组QPI消化产物均展现出体外抗氧化活性,其中微波处理组样品DPPH自由基清除能力（42.71%）及氧自由基吸收能力最强（34.90%）; QPI消化产物能够促进3T3-L1脂肪细胞胰岛素抵抗模型对葡萄糖的摄取,蒸制、煮制和烘焙能够进一步提高该效果（p<0.05）。该研究为藜麦蛋白质的加工和功能性应用提供理论指导,旨在促进藜麦产业的进一步发展。     

Optimised methodology for the extraction of protein from quinoa (Chenopodium quinoa Willd.)

Quinoa is a highly appreciated Andean pseudo‐cereal and has sparked attention worldwide due to its excellent nutritional value. The protein extraction parameters for defatted quinoa seed meal (DQSM) were optimised in this study. Initially, a Plackett–Burman design was applied to screen the factors displaying a potential effect on the quinoa protein extraction yield (Y %, g soluble protein/100 g total protein) being the main evaluated factors: pH, NaCl concentration, time, temperature, solvent type, particle size and solvent/meal ratio. Four main factors: temperature, solvent/meal ratio, pH and time selected from the screening step were optimised with a central composed design (CCD). The obtained response surface model (RSM) produced a satisfactory fitting of the results (R² = 0.9308). Optimal quinoa protein extraction conditions of 36.2 °C, solvent/meal ratio of 19.6/1 (v/w) and 90 min resulted in a protein yield of 62.1% (9.06 g of protein/100 g DQSM) which closely agree with the predicted value of 62.5%.The model was experimentally validated by extracting the quinoa protein using the optimal conditions revealed by RSM. The optimised conditions could be successfully employed in the design process of protein extraction from quinoa seed meal to obtain optimal yields.     

不同菌种发酵对藜麦蛋白质特性及脂质构成的影响

藜麦被认为是一种伪谷物,联合国粮农组织推荐其为最适宜人类食用的“全营养食品”。随着大健康产业的迅速发展,市场对藜麦产品需求也不断增加。据FAO标准,藜麦蛋白有均衡的氨基酸组成,含有人体必需的9种氨基酸,相较于其他谷物和豆类含有高水平的赖氨酸和蛋氨酸。因此,越来越多的研究关注藜麦蛋白的营养价值和功能特性。本文主要综述了有关藜麦蛋白的组成、营养价值、提取方法及乳化性、起泡性、凝胶性、消化性等功能特性的研究进展。除此之外,由于藜麦蛋白改性之后的功能特性增强,本文也概述了藜麦蛋白的物理和生物改性对藜麦蛋白功能特性的影响。藜麦蛋白作为优质蛋白,可以在植物蛋白加工领域被更多的挖掘和使用,推动藜麦蛋白的产业化。

     

藜麦营养功能成分及生物活性研究进展

藜麦是适宜人类食用的全营养食品,不仅含有丰富的蛋白质、淀粉、VB1、叶酸、矿物质（Ca、Zn、Fe）等营养物质,还含有多酚、黄酮、芦丁、槲皮素、异槲皮素、皂苷等功能成分,具有抗氧化、抗炎、降血糖、减肥等生理活性。本文综述藜麦的营养功能成分及其生物活性的国内外研究进展,并对其发展应用前景进行展望。     

Innovations in Health Value and Functional Food Development of Quinoa (Chenopodium quinoa Willd.)

Quinoa (Chenopodium quinoa Willd., Amaranthaceae) is a grain‐like, stress‐tolerant food crop that has provided subsistence, nutrition, and medicine for Andean indigenous cultures for thousands of years. Quinoa contains a high content of health‐beneficial phytochemicals, including amino acids, fiber, polyunsaturated fatty acids, vitamins, minerals, saponins, phytosterols, phytoecdysteroids, phenolics, betalains, and glycine betaine. Over the past 2 decades, numerous food and nutraceutical products and processes have been developed from quinoa. Furthermore, 4 clinical studies have demonstrated that quinoa supplementation exerts significant, positive effects on metabolic, cardiovascular, and gastrointestinal health in humans. However, vast challenges and opportunities remain within the scientific, agricultural, and development sectors to optimize quinoa's role in the promotion of global human health and nutrition.     

藜麦发芽过程中蛋白质与皂苷及淀粉消化特性的变化规律

发芽是改善谷物质构及其营养价值的一种高效的加工方式。本文研究了藜麦发芽过程中蛋白质与皂苷及淀粉消化特性的变化规律。结果显示,发芽显著地提高了藜麦中粗蛋白和可溶性蛋白含量,分别增加了5.38%和17.55%。随着发芽时间不断增加,藜麦总淀粉、直链淀粉及支链淀粉含量分别减少25.95%、4.86%和29.53%,而还原糖含量增加了26.60%。发芽处理显著改善了藜麦种子的淀粉消化性能。发芽前藜麦种子中快消化淀粉、慢消化淀粉及抗性淀粉的百分含量分别为38.45%、43.64%和17.90%。发芽48h后,快消化淀粉的百分含量显著地增加至53.46%,而慢消化淀粉及抗性淀粉的百分含量分别下降至40.42%和6.11%。此外,发芽后藜麦种子中总皂苷含量显著增加了16.46%。研究表明,发芽的藜麦种子含有更好的营养价值和消化性能,可以用于加工功能性食品,促进人体健康。     

挤压膨化处理对藜麦营养成分及体外酵解特性的影响

本研究采用挤压膨化技术对藜麦进行处理,分析处理后藜麦营养成分变化,并结合体外酵解实验,探究挤压膨化处理对藜麦酵解特性的影响。结果表明,挤压膨化能显著降低藜麦中直链淀粉、脂肪、总膳食纤维和不可溶性膳食纤维含量（P＜0.05）,并显著增加可溶性膳食纤维含量（P＜0.05）。体外酵解实验中,随着酵解时间的延长,培养基中产气量不断增加,pH值在发酵前期显著降低（P＜0.05）。相较于空白对照,挤压膨化处理后藜麦能显著上调体外酵解过程中普雷沃氏菌、巨单胞菌、巨球形菌、考拉杆菌、双歧杆菌以及拟杆菌等的相对丰度（P＜0.05）,显著下调瘤胃菌科和肠杆菌科的相对丰度（P＜0.05）。同时,各组发酵产物中短链脂肪酸浓度均增加,且发酵48 h结束时挤压膨化处理后藜麦组高于空白对照组。综上,挤压膨化能影响藜麦的营养组成,其制品作为发酵底物能有效改善肠道菌群,有益于肠道健康。该研究可为通过挤压膨化处理获得藜麦制品及其促进肠道健康产品的开发提供数据支持。     

藜麦淀粉理化特性研究

藜麦(Chenopodium quinoa Willd.)是一种拟谷物,含有丰富的营养物质并具有药用和保健价值。本文采用X射线衍射(XRD)、扫描电子显微镜(SEM)和差示扫描量热仪(DSC)等对碱法和酶法提取的藜麦淀粉的结构和热性能进行了分析,并测定了藜麦淀粉的膨胀度、冻融稳定性和碘蓝值。结果表明,藜麦淀粉颗粒较小,平均粒径为1.15~1.97μm,支链淀粉含量较高。几种淀粉的溶解度、膨胀度、冻融稳定性、透光度和糊化温度等理化特性均与各自的结构特征相关,表现出不同程度的差异。      

藜麦对鲷鱼鱼糜凝胶性能及挥发性风味的影响

研究藜麦作为外源添加物对鲷鱼鱼糜凝胶性能及挥发性风味的影响,结果表明:藜麦添加量在0~3g/100g时,鱼糜的凝胶强度随着添加量的增加而提高,当添加量继续增大,凝胶强度呈现减少趋势。对比零添加组,仍有显著提升(P<0.05)。白度随着添加量的增加而降低。持水力随着添加量的增加而提高。随着藜麦添加量的增加,离子键的变化不明显,氢键呈下降趋势,疏水相互作用、二硫键呈现一定的上升趋势。TCA-可溶性肽随着添加量的增加呈现减小趋势。通过HS-SPME-GC-MS分析纯鲷鱼鱼糜和添加藜麦的鲷鱼鱼糜,分别检出35种和32种挥发性成分,均以醛类、烷烃类、芳香族化合物为主。用相对气味活度值(ROAV)来表明不同挥发性成分对两种鱼糜制品总体风味的影响,分别确定6种和7种关键风味物质。经比对,添加藜麦的鲷鱼鱼糜和纯鲷鱼鱼糜的挥发性风味物质组成及相对含量差别不显著。     

不同加工方式对藜麦淀粉结构与功能特性的影响

为探究藜麦加工方式对其淀粉结构与功能特性的影响,研究采用蒸制和萌发处理藜麦籽粒及挤压膨化处理藜麦全粉,对不同处理后的藜麦进行淀粉提取与特性分析.结果表明:蒸制、萌发和挤压膨化处理藜麦后,其淀粉出现不同程度损伤,损伤程度依次为挤压膨化＞蒸制组＞萌发组;淀粉粒径增大,但其晶型和表面基团未改变;蒸制和萌发组淀粉结晶度提高,挤...     

Interrelationships among seed yield, total protein and amino acid composition of ten quinoa (Chenopodium quinoa) cultivars from two different agroecological regions

BACKGROUND: Quinoa is a good source of protein and can be used as a nutritional ingredient in food products. This study analyses how much growing region and/or seasonal climate might affect grain yield and nutritional quality of quinoa seeds. RESULTS: Seeds of ten quinoa cultivars from the Andean highlands (Bolivia/Argentina site) and Argentinean Northwest (Encalilla site) were analysed for seed yield, protein content and amino acid composition. Grain yields of five cultivars growing at Encalilla were higher, and four were lower, compared with data from the Bolivia/Argentina site. Protein contents ranged from 91.5 to 155.3 and from 96.2 to 154.6 g kg^?1 dry mass for Encalilla and Bolivia/Argentina seeds respectively, while essential amino acid concentrations ranged from 179.9 to 357.2 and from 233.7 to 374.5 g kg^?1 protein respectively. Significant positive correlations were found between the content of essential amino acids and protein percentage. CONCLUSION: It appears that there are clear variations in seed yield, total protein content and amino acid composition among cultivars from the two sites. Essential amino acid composition was more affected than grain yield and protein level. The study revealed that both environmental and climatic factors influence the nutritional composition of quinoa cultivars growing in different agroecological regions. Copyright © 2011 Society of Chemical Industry     

Phenolic,apparent antioxidant and nutritional composition of quinoa (Chenopodium quinoa Willd.) seeds

Quinoa, a gluten-free pseudocereal, has a nutrient and phytochemical profile which may benefit health. Our aim was to investigate the variability in the phenolic and apparent antioxidant content of different quinoa varieties to identify a variety with a high phytochemical content to use in a quinoa-enriched bread. The results showed that free phenolics contributed most (50–83%) to total phenolic content compared with conjugated or bound forms. Apparent antioxidant activities measured by FRAP, ABTS+• and DPPH of free, conjugated and bound extracts were broadly similar, except for free antioxidants when determined by FRAP, which were higher. Phenolic content was positively correlated with FRAP and ABTS+• apparent antioxidant activity. Quinoa samples had a high protein content (13.5 g/100 g dry weight), with a well-balanced amino acid profile. Incorporation of quinoa into baked products such as bread is proposed as a way to deliver this healthy whole-grain cereal into the diet.     

Insights into the nutritional value and bioactive properties of quinoa (Chenopodium quinoa): past,present and future prospective

In recent years, quinoa gained increased attention due to its great adaptability to harsh environmental conditions, high nutritional values and high preference as ingredients of gluten-free and functional foods. In order to improve the diet and direct the population to a better health, the search for new foodstuffs suitable for a healthy lifestyle and proper diet is still ongoing and quinoa seeds are one of these food raw materials. It is a promising variety for human consumption and nutrition in the world, as it has higher nutritional and health values than traditional cereal grains, such as high concentration of protein, fatty acids, tocopherols, phytosterols, phenolic compounds, and low glycaemic index and gluten-free nature. Its consumption is not spread worldwide due to lack of knowledge regarding nutritional and health benefits of quinoa among consumers. This review summarises the nutritional values, bioactive properties, antinutritional factors, and uses of quinoa seeds and oils.     

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300–600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300–600 MPa significantly decreased emulsion stability index. Additionally, HHP‐treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient. © 2012 Society of Chemical Industry     

Effects of pulsed electric fields on physicochemical properties of soybean protein isolates

Effects of pulsed electric fields (PEF) treatment (0-547 μs and 0-40 kV/cm) on physicochemical properties of soybean protein isolates (SPI) were studied. Solubility, surface free sulfhydryls (SH_F) and hydrophobicity of SPI dispersions (20 mg/ml) increased with the increment of the PEF strength and treatment time at constant pulse width 2 μs, pulse frequency 500 pulse per second (pps) and sample flow rate (1 ml/s). When the PEF strength and treatment time were above 30 kV/cm and 288 μs, solubility, surface SH_F, and hydrophobicity of SPI decreased due to denaturation and aggregation of SPI by hydrophobic interactions and disulfide bonds. Size-exclusion chromatography and laser light scattering analyses demonstrated further that stronger PEF treatment-induced dissociation, denaturation and reaggregation of SPI. Circular dichroism analysis showed that PEF treatment did not produce significant secondary structure changes of SPI. These results suggested that controlled PEF could be applied to process liquid food including soybean protein ingredient and to modify their structure and function in order to get desired products.     

超高压对乳清分离蛋白结构和抗氧化活性的影响

为了研究超高压处理对乳清分离蛋白结构的影响,该研究对乳清分离蛋白进行了不同条件的超高压处理,之后测定表面疏水性、傅里叶变换红外光谱、自由巯基含量和内源荧光光谱分析乳清分离蛋白的结构变化。与未经处理的乳清分离蛋白相比,200 MPa及以上压力显著提高了乳清分离蛋白的表面疏水性,在400 MPa-30min时达到最大值。超高压处理使乳清分离蛋白的α-螺旋、β-折叠含量发生明显变化,证明了其对乳清分离蛋白二级结构的影响。超高压处理增加了蛋白自由巯基含量,在400 MPa-30 min时增加49%,并且超高压处理也引起了乳清分离蛋白内源荧光强度的显著变化。在所有的超高压处理条件中,400 MPa-30 min对乳清分离蛋白结构的影响最为显著,并显示出了最高的抗氧化活性。研究表明,超高压处理能显著改变乳清分离蛋白的二、三级结构,暴露出疏水基团等活性基团,从而对抗氧化活性产生影响。