核桃酚类物质和蛋白间的相互作用及其抗氧化活性（英文）

酚类物质和蛋白质之间存在多种相互作用力,因此难以被充分提取。该研究以核桃蛋白为研究对象,用不同量的尿素和氯化钠定向破坏核桃酚类物质和核桃蛋白之间的离子键、氢键和疏水作用力,以研究核桃酚类物质和核桃蛋白之间的非共价键结合机制。结果显示在p H值3.0时,77.7%的酚类物质与蛋白以共价键结合,而有34.6%的缩合单宁与核桃蛋白以共价键结合。在p H值8.0时,有65.4%酚类物质和59.4%的缩合单宁与核桃蛋白以非共价键结合。其中疏水作用力是主要的非共价键结合方式。对以不同非共价键与核桃蛋白相结合的酚类物质的抗氧化活性进行测定,结果显示以离子键与蛋白结合的酚类物质的抗氧化活性最强。其中,在p H值3.0条件下与WP(Iwalnut protein isolates)以离子键结合的酚类物质的DPPH自由基清除能力为5.7%,Fe2+螯合率为5.9%,在p H值8.0条件下与WPI以离子键结合的酚类物质的DPPH自由基清除能力为10.9%,Fe2+螯合率为11.5%。另外,该研究还探讨了在p H值3.0和8.0时,70%(v/v)乙醇和60%(v/v)甲醇提取核桃蛋白中酚类物质的能力,结果表明这两种提取剂不能显著提高酚类物质的提取率,且不能有效得到具有较强抗氧化能力的酚类物质。     

枣果皮中酚类物质提取工艺优化及抗氧化活性分析

为提高枣果皮中的酚类物质的提取效率,该文以马牙枣为试验材料,对枣果皮中酚类物质提取条件进行了优化,同时通过测定酚类物质清除2,2’-二苯基-1-间三硝苯基联肼(DPPH),2,2'-连氮基双(3-乙基苯并噻唑啉)-6-磺酸(ABTS)自由基和铁还原能力,分析了枣果皮提取物中酚类物质的抗氧化活性。结果显示,枣果皮中酚类物质提取的最优条件是采用70%(V/V)的甲醇、在40℃下,以1∶60的料液比浸提4h,重复浸提2次。枣果皮中酚类物质具有很强的抗氧化能力,与合成抗氧化剂2,6-二叔丁基对甲酚(BHT)相比,虽然果皮中酚类物质清除ABTS·+自由基能力略低于BHT,但其清除DPPH自由基和铁还原能力与之相当。研究结果表明枣果皮中酚类物质具有很强的抗氧化能力,在一定程度上可以取代合成抗氧化剂BHT,应用于食品加工业。     

超声预处理大米蛋白制备抗氧化肽

为优化中性蛋白酶酶解大米蛋白制备抗氧化肽的工艺条件,采用超声波预处理大米蛋白.以1,1-二苯基-2-苦基苯肼(DPPH)清除率为响应值,用响应面分析法研究超声功率、超声处理时间和超声处理初始温度对制备抗氧化肽工艺的影响.同时研究了其抗氧化肽清除超氧自由基、DPPH、羟自由基能力及螯合Fe2 和还原能力.结果表明:最佳超声预处理大米蛋白的工艺为:超声功率1500 W、超声处理时间20 min、超声处理初始温度40℃,该条件下的抗氧化肽(2.2057 g/L)清除DPPH可达到74.8%,抗氧化肽得率为33.2%.与未经超声预处理比较,抗氧化肽得率提高了43.7%,DPPH的半抑制率(IC50)降低了17.7%.抗氧化试验表明,大米蛋白抗氧化肽清除超氧自由基、DPPH和羟自由基的IC50值分别为0.0678、0.9315和0.1173 g/L,分别是维生素C的IC50值的1.8、175.8和1.4倍;其螯合Fe2 的IC50值是乙二胺四乙酸的42.2倍,还原能力是维生素C的0.7倍.     

响应面优化花生叶可溶性蛋白提取工艺及抗氧化活性分析

为确定花生叶可溶性蛋白提取最佳工艺,本试验以花生叶为材料,利用碱溶酸沉法提取花生叶可溶性蛋白,分析浸提pH值、料液比及提取时间对蛋白提取率的影响;在单因素试验的基础上,采用Box-Behnken响应面分析法(RSM)优化花生叶可溶性蛋白提取条件,并对所得蛋白进行抗氧化活性分析。结果表明,各影响因素主次顺序为浸提pH值>提取时间>料液比,最佳提取条件为料液比1∶20(w/v)、提取时间40 min、浸提pH值 9.0,以此条件建立的响应面试验回归模型拟合性好(R²=0.992 7),花生叶可溶性蛋白理论提取率为52.8%,实际提取率为54.2%,纯度为63.8%。花生叶可溶性蛋白具有较强的DPPH自由基、超氧阴离子自由基清除能力,以及较好的还原能力。本研究结果为花生叶的开发利用及花生产业链的延长提供了一定的数据支持。     

日喀则市青稞全籽粒抗氧化品质研究

为揭示日喀则青稞全籽粒所含酚类物质与抗氧化能力间的关系,遴选出抗氧化品质优异的品种,对13份青稞材料的酚类物质含量和抗氧化能力进行了品种间的多重比较分析、酚类物质含量和抗氧化能力的相关分析、抗氧化品质的主成分分析以及品种间的聚类分析。结果表明,按籽粒颜色可将13份青稞品种划分为棕、紫、黑三色,深色(紫色和黑色)品种中花色苷、原花青素、总黄酮和总酚含量较高,且氧化自由基吸收能力(ORAC)、铁离子还原能力(FRAP)、1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除能力也高于浅色(棕色)品种。ORAC、FRAP、DPPH自由基清除能力与酚类物质含量之间存在显著或极显著相关性,而金属离子螯合能力(MCC)与酚类物质无显著相关性。主成分分析和聚类分析结果表明,可通过籽粒颜色来进行青稞抗氧化品质初筛,深色青稞品种尤其是黑色青稞品种籽粒抗氧化品质最高。研究青稞籽粒酚类物质抗氧化有助于完善青稞抗氧化品质评价体系,为开发青稞抗氧化功能食品筛选出抗氧化能力优异的品种。     

热加工过程中鲍鱼腹足蛋白间作用力及其质构特性

为探究蛋白质形成凝胶过程中其化学作用力的变化规律以及与凝胶特性之间的关系,该文以鲍鱼腹足为原料,采用溶液分级提取方法,并结合扫描电镜和红外光谱法,考察热加工中鲍鱼腹足蛋白间作用力及其质构特性的变化情况。结果表明,随着加热温度升高(60、80、100℃),扫描电镜结果显示,鲍鱼腹足中间部位与边缘和过渡部位形成孔洞较小、排列紧密的网络结构,同时红外结果表明,随温度升高,蛋白二级结构发生明显变化,N-H弯曲和C-N伸缩振动较为明显,α-螺旋变为无规则卷曲结构,肌球蛋白疏水性增加,-S-S-形成。此时,对应离子键、氢键含量均呈下降趋势,疏水键相对含量呈先上升后下降趋势,二硫键、非二硫共价键含量呈上升趋势。进一步研究表明,各化学作用力与蛋白凝胶质构特性具有高度相关性。在较低温度下(60℃)离子键、氢键和疏水键对凝胶稳定性起主要作用,此时形成的凝胶较柔软;在较高温度下(80、100℃)二硫键、非二硫共价键为维持凝胶稳定的主要作用力,此时凝胶特性较佳,富有弹性、较好的凝聚性和回复性。该研究为热加工过程中鲍鱼腹足蛋白质变化的机理提供参考依据。     

杏仁种皮酚类物质的低共熔溶剂提取及其抗氧化能力

为了探讨低共熔溶剂（Deep Eutectic Solvents, DESs）对杏仁种皮酚类物质的提取率及其提取物抗氧化能力,以4种传统溶剂和5种低共熔溶剂为提取溶剂,比较评价了低共熔溶剂对杏仁种皮酚类物质的提取效果,并采用DPPH、ABTS自由基清除法和氧自由基吸收能力（Oxygen Radical Absorption Capacity, ORAC）分析杏仁种皮低共熔溶剂提取物的抗氧化能力。结果表明,低共熔溶剂对杏仁种皮酚类物质的提取效果更佳,其中氯化胆碱-草酸（DESs2）和氯化胆碱-苹果酸（DESs3）两组低共熔溶剂对杏仁种皮酚类的提取率分别为酸化甲醇的2.18和1.84倍;与酸化甲醇的杏仁种皮提取物相比,DESs2和DESs3杏仁种皮提取物的DPPH自由基清除能力分别提高了26.89%和73.13%,ABTS自由基清除能力分别提高了33.18%和114.81%,氧自由基吸收能力分别提高了14.92和17.73 μmol/g。HPLC结果表明传统溶剂的杏仁种皮提取液中酚类物质组成较复杂,而氯化胆碱-草酸（DESs2）、氯化胆碱-苹果酸（DESs3）和氯化胆碱-苹果酸-脯氨酸（DESs5）的杏仁种皮提取液中酚类物质组成较为单一,说明低共熔溶剂在提取酚类物质时具有很强的专一性。     

高压CO2处理保持非还原桃汁的品质

采用高压CO2（high pressure carbon dioxide,HPCD）处理非还原（not from concentrate,NFC）桃汁,分析HPCD处理后NFC桃汁pH值、可溶性固形物、色泽、酚类和抗氧化活性等品质特性的变化,讨论HPCD对NFC桃汁品质的影响。NFC桃汁的pH值和可溶性固形物含量分别为3.82和10.3°Brix,HPCD处理后没有显著变化;HPCD处理后NFC桃汁颜色变暗,色泽参数L、a、b值显著降低,对应的褐变度提高;NFC桃汁中的主要酚类物质有儿茶素、绿原酸、新绿原酸和阿魏酸,HPCD处理后酚类物质含量没有显著变化;采用FRAP和1,1-二苯基苦基苯肼（1,1-diphenyl-picrylhydrazyl,DPPH）清除率2种方法测定NFC桃汁的抗氧化活性,2种方法的测定结果都表明 HPCD 处理后 NFC 桃汁的抗氧化活性提高,并且随着处理时间的延长而逐渐提高。以上结果表明HPCD能较好的保持NFC桃汁的品质,为非热加工技术应用于果蔬加工提供理论基础。     

酸法提取青稞麸皮结合酚工艺优化

为了提高青稞的附加利用价值,该文以青稞麸皮为研究对象,考察了提取试剂、酸质量分数、萃取pH值、料液比和提取温度对多酚质量分数和 DPPH·自由基清除能力的影响。采用中心组合设计优化其结合酚提取工艺。结果表明,青稞结合酚提取最优工艺条件为：提取试剂为硫酸,酸质量分数为11.10%,水料比为1：17 g/mL,提取温度为75℃,pH值不作处理,此条件下提取得到的结合酚质量分数达224.33 mg/(100 g),DPPH·自由基清除能力达9919.28μmol/(100 g),与预测值多酚质量分数243.80 mg/(100 g),其DPPH·自由基清除能力9087.02μmol/(100 g)基本一致。高效液相色谱法检测到最优工艺下所得青稞结合酚中含有8种酚酸及8种黄酮类物质,总量达325.104 mg/(100 g)。研究结果为全面评价青稞结合酚含量及青稞麸皮的高效利用提供科学依据。     

黑水虻幼虫蛋白质的制备及体外抗氧化活性

本文主要研究黑水虻幼虫蛋白质的制备及其体外抗氧化活性。以黑水虻幼虫为原料,采用碱提酸沉法提取黑水虻幼虫蛋白质,并于等电点沉淀,沉淀复溶后再浓缩、透析、冻干。分别测定了其总还原力,超氧阴离子自由基清除活性、羟基自由基清除活性、DPPH自由基清除活性、ABTS自由基清除活性、金属离子螯合能力及脂质体系中抗氧化能力,并将其体外抗氧化能力与维生素C(测定金属离子螯合能力时与EDTA)和卵清白蛋白进行比较。结果显示:BSFLP的等电点在4.8左右,并且该法所提蛋白纯度较高,表明利用碱提酸沉法对黑水虻幼虫进行蛋白的提取的方法可行。BSFLP的总还原力约是VC的0.013倍,是OVA的1.319倍;BSFLP的超氧阴离子自由基清除活性强于OVA,而弱于VC;其清除羟基自由基、清除DPPH自由基、清除ABTS自由基、螯合亚铁离子、亚油酸体系中抑制过氧化的IC50分别为2.577、3.965、0.228、0.876、5.050 mg·m L-1,也均介于VC(或EDTA)和OVA之间,说明BSFLP具有较高的体外抗氧化活性。本文为黑水虻的进一步研究与综合利用及抗氧化功能蛋白食品的研发提供了一定的依据。     

Antioxidant and antiradical activities in extracts of hazelnut kernel (Corylus avellana L.) and hazelnut green leafy cover

Phenolic compounds in the aqueous systems were extracted, from hazelnut kernel (HK) and hazelnut green leafy cover (HGLC), with 80% (v/v) ethanol (HKe and HGLCe) or 80% (v/v) acetone (HKa and HGLCa). The extracts were examined for their phenolic and condensed tannin contents and phenolic acid profiles (free and esterified fractions) as well as antioxidant and antiradical activities by total antioxidant activity (TAA), antioxidant activity in a beta-carotene-linoleate model system, scavenging of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, and reducing power. Significant differences (p < 0.05) in the contents of total phenolics, condensed tannins, and TAA existed among the extracts that were examined. HGLCa extract had the highest content of total phenolics (201 mg of catechin equivalents/g of extract), condensed tannins (542 mg of catechin equivalents/g of extract), and TAA (1.29 mmol of Trolox equivalents/g of extract) followed by HGLCe, HKa, and HKe extracts, respectively. Five phenolic acids (gallic acid, caffeic acid, p-coumaric acid, ferulic acid, and sinapic acid) were tentatively identified and quantified, among which gallic acid was the most abundant in both free and esterified forms. The order of antioxidant activity in a beta-carotene-linoleate model system, the scavenging effect on DPPH radical, and the reducing power in all extracts were in the following order: HGLCa > HGLCe > HKa > HKe. These results suggest that both 80% ethanol and acetone are capable of extracting phenolics, but 80% acetone was a more effective solvent for the extraction process. HGLC exhibited stronger antioxidant and antiradical activities than HK itself in both extracts and could potentially be considered as an inexpensive source of natural antioxidants.     

Polyphenols and antioxidant capacity of seed coat and cotyledon from Brazilian and Peruvian bean cultivars (Phaseolus vulgaris L.)

Seed coats and cotyledons from 25 Brazilian and 3 Peruvian bean cultivars were investigated in relation to their phenolic profiles and antioxidant capacity. Condensed tannins, anthocyanins, and flavonols such as kaempferol and quercetin glycosides were mostly found in seed coats. Cotyledons were rich in phenolic acids, such as ferulic, sinapic, chlorogenic, and other hydroxycinnamic acids. In general, the seed coat color pattern and the type of cultivar showed an important influence on the variability of phenolic profiles and levels, respectively. Total phenolics and antioxidant capacity assessed by the DPPH method were higher in seed coats than in cotyledons. The antioxidant capacity had a significant correlation with condensed tannins for all samples and with total anthocyanins in black and red seed coats, whereas in cotyledons, it was more related to the total phenolic content.     

Antioxidant activity and phenolic compositions of lentil (Lens culinaris var. Morton) extract and its fractions

Phenolic compounds were extracted from Morton lentils using acidified aqueous acetone. The crude Morton extract (CME) was applied onto a macroresin column and desorbed by aqueous methanol to obtain a semipurified Morton extract (SPME). The SPME was further fractionated over a Sephadex LH-20 column into five main fractions (I-V). The phytochemical contents such as total phenolic content (TPC), total flavonoid content (TFC), and condensed tannin content (CTC) of the CME, SPME, and its fractions were examined by colorimetric methods. Antioxidant activity of extracts and fractions were screened by DPPH scavenging activity, Trolox equivalent antioxidant capacity (TEAC), ferric reduced antioxidant power (FRAP), and oxygen radical absorbing capacity (ORAC) methods. In addition, the compositions of active fractions were determined by HPLC-DAD and HPLC-MS methods. Results showed that the fraction enriched in condensed tannins (fraction V) exhibited significantly higher values of TPC, CTC, and antioxidant activity as compared to the crude extract, SPME, and low molecular weight fractions (I-IV). Eighteen compounds existed in those fractions, and 17 were tentatively identified by UV and MS spectra. HPLC-MS analysis revealed fraction II contained mainly kaempferol glycoside, fractions III and IV mainly contained flavonoid glycosides, and fraction V was composed of condensed tannins. The results suggested that the extract of Morton lentils is a promising source of antioxidant phenolics and may be used as a dietary supplement for health promotion.     

NMR, HPLC-ESI-MS, and MALDI-TOF MS analysis of condensed tannins from Delonix regia (Bojer ex Hook.) Raf. and their bioactivities

The structures of the condensed tannins isolated from leaf, fruit, and stem bark of Delonix regia (Bojer ex Hook.) Raf. have been investigated with (13)C nuclear magnetic resonance ((13)C NMR) and high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS) coupled with thiolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. The results showed that these condensed tannins from D. regia possessed structural heterogeneity in monomer units and degree of polymerization. Propelargonidin (PP) and procyanidin (PC) were found in the leaf, fruit, and stem bark of D. regia, while prodelphinidin (PD) was found only in the leaves. The polymer chain lengths of condensed tannins from leaf and fruit organs were detected to be trimers to hexadecamers but from trimers to tridecamers for stem bark. B-type linkages were present in all these compounds. Condensed tannins from different parts of D. regia can be explored as tyrosinase inhibitors and food antioxidants because of their potent antityrosinase and antioxidant activities. The inhibitor concentration leading to 50% enzyme activity (IC(50)) was estimated to be 38 ± 1, 73 ± 2, and 54 ± 1.5 μg/mL for the condensed tannins of leaf, fruit, and stem bark. Condensed tannins extracted from stem bark exhibited the highest antioxidant activity; the DPPH scavenging activity (IC(50)) and the FRAP values were 90 ± 2 μg/mL and 5.42 ± 0.09 mmol AAE/g, respectively.     

Effects of roasting on the antioxidant status and phenolic profiles of commercial Turkish hazelnut varieties (Corylus avellana L.)

The effect of roasting on the antioxidant status and phenolic profiles of seven commercial Turkish hazelnut varieties (namely, ?ak?ldak, Fo?a, Karaf?nd?k, Mincane, Palaz, Sivri, and Tombul) was assessed. Samples were examined for their total phenolics, oxygen radical absorbance capacity (ORAC) values, condensed tannins, and phenolic acids (free and bound forms). Significant losses (p < 0.05) in total phenolics (~66.3%), ORAC values (~41.6%), condensed tannins (~75.2), and phenolic acids (~42.7) were noted when the hazelnuts were roasted. Some variations both between and within natural and roasted hazelnuts were observed (p < 0.05). Phenolic acids were mainly found in the bound form. Gallic, protocatechuic, p-coumaric, and ferulic + sinapic acids were present in all hazelnut varieties, albeit to different extents, and the first two were dominant. Mincane, in roasted form, had the highest total phenolics, ORAC values, condensed tannins, and phenolic acids. This was due to the presence of some skin in roasted Mincane. No skin was left in all other varieties upon roasting. The present work suggests that roasting results in a significant loss in the antioxidant status and phenolic profiles because of the removal of the skin, which is a rich source of phenolics. It is highly recommended to consume natural hazelnut instead of the roasted counterpart to take advantage of all of the functional benefits of this nut.     

Antioxidative efficacy of alkali-treated tilapia protein hydrolysates: a comparative study of five enzymes

The antioxidant activities of alkali-treated tilapia protein hydrolysates were determined by their ability to inhibit the formation of lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS) in a washed muscle model system and by their ability to inhibit DPPH free radicals and chelate ferrous ion in an aqueous solution. Protein isolates were prepared from tilapia white muscle using alkali solubilization at pH 11.0 and reprecipitation at pH 5.5. Protein hydrolysates were prepared by hydrolyzing the isolates using five different enzymes, Cryotin F, Protease A Amano, Protease N Amano, Flavourzyme, and Neutrase, to 7.5, 15, and 25% degrees of hydrolysis (DH). All of the protein hydrolysates significantly (p<0.05) inhibited the development of TBARS and PV. The antioxidant activity of the hydrolysates increased with the DH. Also, the antioxidant activity of the hydrolysates varied significantly (p<0.05) among the different enzymes. The ability of different enzyme-catalyzed protein hydrolysates to scavenge DPPH radicals was not reflected in their ability to inhibit oxidation in a washed tilapia model system. In a washed muscle model system, the hydrolysates prepared using Cryotin F were most effective and the hydrolysates prepared using Flavourzyme and Neutrase were least effective in inhibiting the development of TBARS and PV, whereas in an aqueous solution, hydrolysates prepared using Flavourzyme were most effective in scavenging DPPH radicals and chelating ferrous ions. Enzymatic hydrolysis decreased the size of tilapia protein hydrolysates and, in general, tilapia protein hydrolysates with low molecular weights were better antioxidants than those with high molecular weights.     

Antioxidant and iron-binding properties of curcumin, capsaicin, and S-allylcysteine reduce oxidative stress in rat brain homogenate

Research demonstrates that antioxidants and metal chelators may be of beneficial use in the treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). This study investigated the antioxidant and metal-binding properties of curcumin, capsaicin, and S-allylcysteine, which are major components found in commonly used dietary spice ingredients turmeric, chilli, and garlic, respectively. The DPPH assay demonstrates that these compounds readily scavenge free radicals. These compounds significantly curtail iron- (Fe2+) and quinolinic acid (QA)-induced lipid peroxidation and potently scavenge the superoxide anion generated by 1 mM cyanide in rat brain homogenate. The ferrozine assay was used to measure the extent of Fe2+ chelation, and electrochemistry was employed to measure the Fe3+ binding activity of curcumin, capsaicin, and S-allylcysteine. Both assays demonstrate that these compounds bind Fe2+ and Fe3+ and prevent the redox cycling of iron, suggesting that this may be an additional method through which these agents reduce Fe2+-induced lipid peroxidation. This study demonstrates the antioxidant and metal-binding properties of these spice ingredients, and it is hereby postulate that these compounds have important implications in the prevention or treatment of neurodegenerative diseases such as AD.     

Effects of different organic farming methods on the concentration of phenolic compounds in sea buckthorn leaves

The effects of different cultivation methods on the amount of phenolic compounds in leaves of 1-year-old seedlings of two Finnish sea buckthorn (Hippophae rhamnoides L. ssp. rhamnoides) cultivars 'Terhi' and 'Tytti' were studied in a field experiment established at coastal area in Merikarvia, western Finland. The cultivation methods included different fertilizers (suitable for organic cultivation), mulches (organic and plastic), and land contours (flat vs low hill surface). Two experiments were conducted. The first allowed the estimation of the effects of cultivar, fertilizer, surface contour, and all their interactions, while the other allowed the estimation of the effects of mulches, land contours, and their interactions for the cultivar 'Tytti'. Eleven different hydrolyzable tannins, pentagalloylglucose, and 14 other phenolic compounds were detected by chemical analysis with high-performance liquid chromatography (HPLC). The amount of phenolic compounds varied between different land contours and mulches. The concentrations of gallic acid, pentagalloylglucose, quercetin-3-rhamnoside, monocoumaroyl astragalin A, total hydrolyzable tannins, and condensed tannins were significantly higher on the flat surface than on the low hill surface. The plastic mulch decreased the concentration of gallic acid, hydrolyzable tannins, and condensed tannins compared to the other mulches used. These results suggest ways to cultivate sea buckthorn to produce large amounts of valuable chemicals, especially tannins in the leaves.     

Total phenolics, phenolic acids, isoflavones, and anthocyanins and antioxidant properties of yellow and black soybeans as affected by thermal processing

The effects of boiling and steaming processes on the phenolic components and antioxidant activities of whole yellow (with yellow seed coat and yellow cotyledon) and black (with black seed coat and green cotyledon) soybeans were investigated. As compared to the raw soybeans, all processing methods caused significant (p < 0.05) decreases in total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), monomeric anthocyanin content (MAC), DPPH free radical scavenging activity (DPPH), ferric reducing antioxidant power (FRAP), and oxygen radical absorbing capacity (ORAC) in black soybeans. Pressure steaming caused significant (p < 0.05) increases in TPC, CTC, DPPH, FRAP, and ORAC in yellow soybeans. The steaming resulted in a greater retention of TPC, DPPH, FRAP, and ORAC values in both yellow and black soybeans as compared to the boiling treatments. To further investigate the effect of processing on phenolic compounds and elucidate the contribution of these compounds to changes of antioxidant activities, phenolic acids, isoflavones, and anthocyanins were quantitatively determined by HPLC. The pressure steaming treatments caused significant (p < 0.05) increases in gallic acid and 2,3,4-trihydroxybenzoic acid, whereas all treatments caused significant (p < 0.05) decreases in two predominant phenolic acids (chlorogenic acid and trans-cinnamic acid), and total phenolic acids for both yellow and black soybeans. All thermal processing caused significant (p < 0.05) increases in aglucones and beta-glucosides of isoflavones, but caused significant (p < 0.05) decreases in malonylglucosides of isoflavones for both yellow and black soybeans. All thermal processing caused significant (p < 0.05) decreases of cyanidin-3-glucoside and peonidin-3-glucoside in black soybeans. Significant correlations existed between selected phenolic compositions, isoflavone and anthocyanin contents, and antioxidant properties of cooked soybeans.     

Effects of extraction solvent mixtures on antioxidant activity evaluation and their extraction capacity and selectivity for free phenolic compounds in barley (Hordeum vulgare L.)

Four kinds of solvent extracts from three Chinese barley varieties (Ken-3, KA4B, and Gan-3) were used to examine the effects of extraction solvent mixtures on antioxidant activity evaluation and their extraction capacity and selectivity for free phenolic compounds in barley through free radical scavenging activity, reducing power and metal chelating activity, and individual and total phenolic contents. Results showed that extraction solvent mixtures had significant impacts on antioxidant activity estimation, as well as different extraction capacity and selectivity for free phenolic compounds in barley. The highest DPPH* and ABTS*+ scavenging activities and reducing power were found in 80% acetone extracts, whereas the strongest *OH scavenging activity, O2*- scavenging activity, and metal chelating activity were found in 80% ethanol, 80% methanol, and water extracts, respectively. Additionally, 80% acetone showed the highest extraction capacity for (+)-catechin and ferulic, caffeic, vanillic, and p-coumaric acids, 80% methanol for (-)-epicatechin and syringic acid, and water for protocatechuic and gallic acids. Furthermore, correlations analysis revealed that TPC, reducing power, DPPH* and ABTS*+ scavenging activities were well positively correlated with each other (p < 0.01). Thus, for routine screening of barley varieties with higher antioxidant activity, 80% acetone was recommended to extract free phenolic compounds from barley. DPPH* scavenging activity and ABTS*+ scavenging activity or reducing power could be used to assess barley antioxidant activity.