Walnut Free Radicals Studied by ESR

ABSTRACT: The electron spin resonance (ESR) method was used. Walnut kernels were annealed within a wide temperature range [20 to 200 °C] in air and in vacuum. The concentration of free radicals increased with the temperature of sample annealing, especially between 120-200 °C. Annealing in vacuum brought about a lower increase in free radical concentration than the annealing in air. A considerable increase in free radical concentration was observed during annealing of samples impregnated with dibenzoyl peroxide. The observed ESR spectrum is a nonresolved singlet exhibiting a line width of about 0.8 mT and a g-factor of 2.0043. The increase in free radical concentration indicates degradation and oxidation processes.     

米糠蛋白O/W及W/O/W乳液制备及界面稳定性

为对比不同米糠蛋白质量浓度下O/W及W/O/W乳液的稳定性,以米糠蛋白作为基料,采用双乳化法制备O/W及W/O/W乳液,考察不同米糠蛋白质量浓度下乳液的微观形态和稳定性并探究其界面稳定机理。结果表明：W/O/W乳液的贮存稳定性显著优于O/W乳液;与相同蛋白含量的O/W乳液相比,W/O/W乳液的黏度显著提高;当米糠蛋白质量浓度为0.4 g/100 mL时,W/O/W乳液的稳定性较O/W乳液提高了1 倍以上;乳液内部包裹更多的W/O液滴,W/O/W乳液的粒径较大;而此时静电斥力也较大,起到稳定乳液的目的。同时,米糠蛋白质量浓度不小于0.4 g/100 mL时,O/W及W/O/W乳液中蛋白质的吸附率较高,达到78%以上。本研究为天然米糠蛋白质在食品级乳液中的开发提供参考,为粮食副产物的综合利用提供了新思路。     

高效液相色谱法测定糜子中酚酸类化合物

为探索糜子麸皮和糜米中酚酸类物质的成分和含量,采用福林-酚法和高效液相色谱法测定比较糜子麸皮 和糜米中自由酚含量和酚酸类物质的种类。结果表明：不同品种糜子麸皮之间自由酚含量差异不显著,糜米之间自 由酚法差异极其显著（P＜0.01）。同一品种糜子麸皮和糜米之间自由酚含量差异显著（P＜0.05）,糜子麸皮自由 酚含量远高于糜米。赤糜2号麸皮和糜米中自由酚含量最高,麸皮中为159.22 mg没食子酸/100 g,糜米中为47.98 mg 没食子酸/100 g。糜子中检测到的酚酸类物质有绿原酸、丁香酸、香草酸、p-香豆酸、阿魏酸。     

利用谷物进行类胡萝卜素固态发酵

研究了 7种谷物培养基及相关因素对青霉PT95菌株进行类胡萝卜素固态发酵的影响作用。结果表明 ,谷物培养基的组成对PT95菌株在固态发酵条件下的菌核生物量和菌核中的类胡萝卜素含量都有明显的影响 ;接种方式和接种量能明显影响谷物培养基上的菌核生物量 ,但对菌核中的类胡萝卜素含量没有明显的影响 ;在谷物培养基里添加麸皮有利于菌核的形成。在选择最佳接种方式、接种量 ,并在培养基里添加 2 0 %麸皮 (干重 )的固态发酵条件下 ,大米培养基上得到的菌核生物量最高 ,达到 1 5 0 0 g/1 0 0 g(干料 ) ;荞麦培养基上 ,菌核中的类胡萝卜素含量最高 ,达到82 6μg/g(干菌核 ) ;而在谷子培养基上 ,类胡萝卜素产率最高 ,达到 1 1 45 7μg/1 0 0 g(干料 )。     

Phenolic acid profiles and antioxidant activities of wheat bran extracts and the effect of hydrolysis conditions

Four different types of wheat bran were extracted and analyzed for phenolic acids using the Folin–Ciocalteu method and HPLC. The extracts and their hydrolysis products were also evaluated for their antioxidant activities. The total phenolic content of the red wheat bran was higher than that of the white wheat. We found that the majority of the phenolic acids existed in a bound form in wheat bran. These phenolic acids can be released by hydrolyzing the bran under alkaline or acidic conditions; however, the former was more efficient in the release of free phenolic acids than the latter. Ferulic, vanillic, and syringic acids were the major individual phenolic acids in the studied wheat bran. The main portion of the total ferulic acid was from alkaline hydrolysis. The alkaline hydrolysable fractions had greater antioxidant activities, while the acid hydrolysable fractions showed lower activities in both the red and white bran. The antioxidant activity of bran extract was stronger than that of free phenolic acids.     

Effect of extruded wheat bran on dough rheology and bread quality

Bran extrusion is mainly under study and works should be performed to know the effect on dough and bread. This study was designed to investigate the effect of bran extrusion (addition of 2.5 g/100 g to 20 g/100g bran) on the rheological characteristics of bread dough, behaviour during fermentation, and bread quality. Extruded bran increased dough development time and tenacity to a greater extent than non-extruded bran, and minimized the loss of stability if over-mixing occurred. Extruded bran, due to its greater gas production, also reduced loss of dough height during fermentation to a greater extent than untreated bran. However, breads with extruded bran showed a higher volume and lower initial firmness than breads with normal bran if improver was added. However, no differences were found in the organoleptic evaluation. Bran extrusion therefore modified dough rheology but did not negatively affect bread quality. It could even improve the quality of breads with bran when improvers are added.     

稻谷水热加工过程中镉迁移规律研究

目的研究稻谷在蒸谷米水热加工过程中镉的迁移规律。方法以蒸谷米小试装置及生产线采集样品为研究对象,在优化碾米时间的基础上,在排除水分含量差异对测定结果的前提下,利用统计分析考察水热工艺(浸泡和蒸煮)对稻谷各部分(稻壳、米糠和精米)镉含量的影响。结果由实验数据推断,在水热过程中,镉的迁移主要发生在稻谷的内部,且主要是在浸泡时从精米向米糠迁移富集,而蒸煮工艺则对镉的分布变化影响很小;经过浸泡,精米中的镉含量可降低约40%;推测热水的浸泡一方面使胚乳淀粉分子间游离的镉部分溶出,一方面促使镉向络合能力更强的米糠蛋白迁移,最终导致其分布发生明显变化。结论该研究为在稻谷加工过程中实现重金属镉的消减提供了科学依据。     

灵芝发酵液的超滤提取及其抗氧化活性的研究

考察了超滤浓缩醇沉法提取发酵灵芝胞外多糖,超滤条件:截留分子量10000,压差0.2MPa,料液浓度12.20mg/mL。超滤浓缩法与传统的减压浓缩法相比,多糖含量、多糖得率均高于后者,所得多糖的品质得到提高,相应减轻了后道多糖纯化的负担。灵芝胞外多糖对羟自由基·OH(HFR)有较好的清除能力,在一定范围内清除率与浓度呈正相关,超滤浓缩醇沉法提取灵芝胞外多糖的·OH清除率高于减压浓缩醇沉法。     

Copper oxide-based model of persistent free radical formation on combustion-derived particulate matter

We have found that environmentally persistent free radicals (PFRs) are formed by adsorption of substituted aromatic molecular precursors on the surface of cupric oxide-containing particles at temperatures between 100 and 400 degrees C. This temperature range corresponds to the conditions in the postflame, cool zone of combustion, and thermal processes. Depending upon the nature of the precursor and the adsorption temperature, both substituted phenoxyl and semiquinone radicals are formed. The PFRs are formed through a mechanism of initial physisorption, followed by chemisorption via elimination of water or hydrogen chloride, and electron transfer resulting in the simultaneous reduction of Cu(II) to Cu(I) and formation of the PFR. The PFRs are still observable by electron paramagnetic resonance (EPR) after exposure to air for more than a day. Their lifetimes under vacuum appear to be infinite. Other redox-active transition metals such as iron are expected to also mediate or catalyze the formation of PFRs. The properties of the observed radicals are consistent with radicals previously observed on airborne and combustion-generated particulate matter. We propose a catalytic biochemical cycle for both the particle-associated semiquinone and phenoxyl PFRs that result in the formation of hydroxyl radical and other reactive oxygen species (ROS). This suggests that combustion-generated, particle-associated PFRs may be responsible for the oxidative stress resulting in cardiopulmonary disease and probably cancer that has been attributed to exposure to airborne fine particles.     

Mechanism of the interaction between insoluble wheat bran and polyphenols leading to increased antioxidant capacity

This study aimed to provide an in-depth investigation of the interaction between insoluble wheat bran and polyphenols. Treatment with tannic acid, but not gallic acid, increased the bound antioxidant capacity of insoluble wheat bran depending on its aqueous concentration (p < 0.05). Among the beverages tested (white and red wines, black and green tea infusions), treatment with green tea infusion caused the highest increase in the total antioxidant capacity. Temperature, time, air and pH were found to significantly affect the reaction between insoluble wheat bran and polyphenols. The bound antioxidant capacity of insoluble bran increased to above 100 mmol TE.kg^− 1 after treatment with green tea infusion at optimum conditions (50 °C, pH 9.0, no airflow). Concentration of free amino groups available in wheat bran significantly decreased (59.5%) after the treatment. The results suggested that polyphenols are oxidized to quinones under alkaline conditions further bound to free amino groups available on the surface of wheat bran.     

糙米酵素流变学特性研究

研究糙米粉在不同温度和浓度条件下剪切速率和表观黏度的变化关系,并确定在各温度和浓度条件下其稠度系数和流变指数,建立流变学方程.试验结果表明,糙米粉的黏度随温度的升高而增大,且发酵后的糙米酵素粉黏度随温度的变化范围大于未发酵;糙米粉的黏度随浓度的增大而增大,且发酵后的糙米粉黏度随浓度的变化范围小于未发酵的.     

Carbon-centered radicals in isolated soy proteins

ABSTRACT:  Solid-state electron paramagnetic resonance (EPR) spectroscopy of commercial samples of isolated soy proteins (ISP) revealed a symmetrical free-radical signal typical of carbon-centered radicals ( g = 2.005) ranging from 2.96 × 10¹⁴ to 6.42 × 10¹⁴ spins/g. The level of free radicals in ISP was 14 times greater than similar radicals in sodium caseinate, 29 times greater than egg albumin, and about 100 times greater levels than casein. Nine soy protein powdered drink mixes contained similar types of free radicals up to 4.10 × 10¹⁵ spins/g of drink mix, or up to 6.4 times greater than the highest free-radical content found in commercial ISP. ISP samples prepared in the laboratory contained trapped radicals similar to the levels in commercial ISP samples. When ISP was hydrated in 2.3 mM sodium erythorbate or 8.3 mM L-cysteine, frozen and dried, the level of trapped free radicals increased by about 17- and 19-fold, respectively. The ESR spectrum of defatted soybean flakes contained overlapping signals from the primary free-radical peak ( g = 2.005) and a sextet pattern typical of manganese-II. The manganese signal was reduced in the laboratory ISP and very weak in the commercial ISP.     

Effect of milling time on antioxidant compounds and activities of methanol extracts of sorghum [Sorghum bicolor (L.) Moench]

Antioxidant compounds and activities of methanol extracts of sorghum for different milling times were investigated. Total polyphenol, flavonoid, and tannin contents were measured using spectrophotometric methods. Methanol extracts were also evaluated for antioxidant activities based on DPPH and ABTS radical-scavenging activities. As milling rates increased, milling recovery and a value decreased, while L and b values increased. The extraction yield, antioxidant compound contents, and antioxidant activities of sorghum grain decreased with increasing milling rates. Methanol extracts from sorghum bran generally showed higher antioxidant activities than extracts from sorghum grain. The antioxidant content was higher in sorghum bran extracts than in grain extracts. A significant (p<0.05) correlation was observed between free radical-scavenging activity and the content of polyphenolic compounds. Sorghum bran exhibited antioxidant activities that may have important health benefits.     

干燥方式对金银花多酚组分及其抗氧化活性的影响

研究传统热风干燥、自然阴干以及真空干燥、真空冷冻干燥等不同干燥方式对金银花多酚类物质含量及抗氧化活性的影响。采用Folin-酚比色法及高效液相色谱（high performance liquid chromatography,HPLC）法分别检测4 种干燥方式下的金银花总酚及多酚类组分含量,并比较其清除1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、羟自由基（•OH）和2,2’-二氮-双（3-乙基苯并噻唑-6-磺酸）铵盐（2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonate acid) diammonium salt,ABTS）自由基的能力。结果表明：4 种干燥方式对金银花总酚含量及多酚类组分均有一定影响,其中真空冷冻干燥处理时金银花总酚及多酚类组分损失最小;不同干燥方式对金银花的抗氧化能力影响显著（P＜0.05）,真空冷冻干燥样品清除DPPH自由基、•OH和ABTS＋•的半抑制浓度（IC50）分别为5.43、17.64、44.32 μg/mL;而自然阴干、真空干燥和热风干燥处理的样品清除DPPH自由基、•OH及ABTS＋•的IC50高于真空冷冻干燥金银花相应的IC50。相关性分析显示,金银花酚酸类组分与其抗氧化活性显著相关（P＜0.05）。因此,真空冷冻干燥能较好地保留金银花多酚类物质,且具有较强的抗氧化活性,适宜用于金银花的干燥。     

Rice kernel phenolic content and its relationship with antiradical efficiency

Plant phenolics exert beneficial effects on human health and may also prevent oxidative deterioration of food. Two field experiments were carried out for characterising phenolics in rice. The first assay was conducted in 1999 and 2000 in Beaumont, TX and included five light‐brown, two purple and 10 red pericarp coloured cultivars. ‘Bran colour’ was highly statistically significant for both bran phenolic concentration and antiradical efficiency (p < 0.001). ‘Year’ and its interaction with bran colour were not significant for the analysed traits, suggesting that seasonal differences and their interactions may not affect phenolic content or antiradical efficiency. The accessions ranged from 3.1 to 45.4 mg gallic acid equivalents (GAE) g^?1 bran and from 10.0 to 345.3 µM trolox equivalents (TE) g^?1 bran for total phenolic content and antiradical efficiency respectively. The light‐brown bran genotypes exhibited the lowest values for phenolic content and antiradical efficiency, whereas red bran ones displayed ca 10 times higher total phenolic content and more than 50 times higher tannin content than light‐brown ones. The two purple lines showed either low or high values for the studied traits. Antiradical efficiency of rice bran extracts was highly positively correlated with total phenolic content (r = 0.99***), suggesting that phenolics are the main compounds responsible for the free radical‐scavenging activity in rice bran extracts. In the second field experiment (Stuttgart, AR, 2001 and Beaumont, TX, 2000), 133 coloured rice cultivars were analysed for total phenolic content in whole grain. The accessions showed a large variation for total phenolics, ranging from 0.69 to 2.74 mg GAE g^?1 grain. The data confirmed previous results suggesting bran colour as the main factor affecting phenolic concentration in rice kernel and seasonal effects and their interactions as not significant. The results also confirm that within red and purple bran groups can be found the highest phenolic concentrations in rice kernel. Published in 2004 for SCI by John Wiley & Sons, Ltd.     

黑米糠用于运动食品开发的价值探讨及展望

通过对黑米糠中10种运动营养成分的分析表明,黑米糠是难得的潜在运动营养食品原料。黑米糠的运动功效研究主要集中在花青苷的功效研究。现有研究结论显示,黑米糠具有抗氧化、抗疲劳、抗炎、提高免疫力和清除自由基的潜在活性。本研究指出开发黑米糠运动食品的8个途径,旨在引起体育科研工作者对黑米糠运动营养源的关注,为运动食品增添新成员和黑米糠资源的利用提供新途径。     

Antioxidant activity of feruloylated oligosaccharides from wheat bran

Ferulic acid, the main phenolic acid in wheat bran, is esterified to arabinose residues in the cell wall arabinoxylan. Treatment of wheat bran insoluble dietary fibre with xylanases from Bacillus subtilis released feruloylated oligosaccharides, which were purified with Amberlite XAD-2. The antioxidant activity of such oligosaccharides was evaluated using the assay system for erythrocyte hemolysis mediated by peroxyl free radicals generated from 2,2^′-azobis-2-amidinopropane dihydrochloride (AAPH) under in vitro conditions. The feruloylated oligosaccharides inhibited hemolysis of erythrocytes in a dose-dependent manner with 91.7% inhibition of erythrocyte hemolysis at 4 mg/ml.     

Effect of low temperature thermal treatment on soils contaminated with pentachlorophenol and environmentally persistent free radicals

The effect of low temperature thermal treatment on soils from a former Superfund wood-treating site contaminated with pentachlorophenol (PCP) and the environmentally persistent free radical (EPFR), pentachlorophenoxyl, was determined. The pentachlorophenoxyl EPFRs' and the PCP molecules' chemical behavior were simultaneously monitored at temperatures ranging from 25 to 300 °C via electron paramagnetic resonance (EPR) spectroscopy and GC-MS analysis, respectively. Two types of thermal treatment were employed: a closed heating (oxygen-starved condition) where the soil was heated under vacuum and an open heating system (oxygen-rich conditions), where the soil was heated in ambient air. EPR analyses for closed heating indicated the EPFR concentration was 2-12 × 10(18) spins/g of soil, with a g-factor and line width (ΔHp-p) of 2.00311-2.00323 and 4.190-5.472 G, respectively. EPR analyses for the open heating soils revealed a slightly broader and weaker radical signal, with a concentration of 1-10 × 10(18) spins/g of soil, g-factor of 2.00327-2.00341, and ΔHp-p of 5.209-6.721 G. This suggested the open heating resulted in the formation of a more oxygen-centered structure of the pentachlorophenoxyl radical or additional, similar radicals. The EPFR concentration peaked at 10 × 10(18) spins/g of soil at 100 °C for open heating and 12 × 10(18) spins/g at 75 °C for closed heating. The half-lives of the EPFRs were 2-24 days at room temperature in ambient air. These results suggest low temperature treatment of soils contaminated with PCP can convert the PCP to potentially more toxic pentachlorophenoxyl EPFRs, which may persist in the environment long enough for human exposure.     

香兰素和维生素C对卤煮牛肉中杂环胺含量的影响

目的探索牛肉卤煮加工过程中添加香兰素和维生素C对杂环胺形成含量的影响。方法采用固相萃取前处理技术,结合不同处理情况下高效液相紫外和荧光检测法测定肉样中杂环胺的含量。结果香兰素和维生素C都能够减少卤煮牛肉中杂环胺的形成。当维生素C的添加浓度量达0.15%时,杂环胺总量减少90%以上。当维生素C浓度增大到0.5 mg/m L时,维生素C对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除率高达90%;当维生素C添加浓度为0.4 mg/m L时,其对超氧阴离子的清除率高达84%左右。结论维生素C和香兰素均可减少卤煮牛肉中杂环胺的生成,维生素C对DPPH自由基清除率和超氧阴离子自由基清除率均比香兰素高,且对卤煮牛肉中杂环胺的抑制效果比香兰素好。     

过氧自由基氧化对米糠蛋白结构和功能性质的影响

采用不同浓度的2,2’-盐酸脒基丙烷（2,2’-azobis(2-amidinopropane),AAPH）有氧热分解产生的过氧自由基氧化米糠蛋白,研究过氧自由基氧化对米糠蛋白结构和功能性质的影响。结果显示：随着AAPH浓度的增加,米糠蛋白羰基、二硫键和二酪氨酸含量分别从2.0?nmol/mg、12.04?nmol/mg和84.54增加到7.09?nmol/mg、14.69?nmol/mg和127.1,游离巯基含量从23.97?nmol/mg下降到15.29?nmol/mg。过氧自由基氧化导致米糠蛋白α-螺旋和无规卷曲相对含量下降,β-折叠相对含量增加,氨基酸残基侧链含量先增加后略微下降;同时使得米糠蛋白表面疏水性和内源荧光强度下降,最大荧光峰位蓝移。过氧自由基氧化对蛋白质亚基结构影响较小,可同时使得米糠蛋白多肽链聚集和主肽链部分断裂形成多肽。随着AAPH浓度的增加,米糠蛋白溶解性逐渐降低,持水性、持油性、起泡能力、泡沫稳定性、乳化性和乳化稳定性先上升后下降。