热处理红-黄色翡翠的红外光谱分析

红-黄色翡翠是否经过热处理,其价值相差悬殊。随着市场对红-黄色翡翠的需求增加,鉴别其是否经过热处理是目前宝玉石鉴定的难点和热点问题。通过加热实验,利用红外光谱测试技术对加热前、后的红-黄色翡翠样品的红外光谱进行对比分析。结果表明,加热前、后的红-黄色翡翠样品的红外光谱具有不同的特征,主要表现为硬玉结构中OH的四组吸收峰强弱的变化:(1)吸收峰的强变化是在3 000～4 000 cm-1之间的峰型从加热前呈U型到加热后呈V型;(2)吸收峰的弱变化则是谱线略有改变,出现3 622～3 628 cm-1或3 670 cm-1附近的吸收峰,这些特征可作为红-黄色翡翠是否经过加热处理的辅助性诊断指标。     

紫外/可见光谱技术无损检测李子可溶性固形物含量

利用光谱技术结合化学计量学对李子可溶性固形物含量检测进行研究,为李子品质无损检测提供科学方法。通过反射式光谱采集系统获取了"红"李子和"青"李子的平均光谱,并对原始光谱数据进行预处理;应用连续投影算法(SPA)和竞争性自适应重加权算法(CARS)对预处理后的光谱数据提取特征波长;分别建立基于全光谱和特征波长的预测李子可溶性固形物含量的误差反向传播(BP)网络模型。结果表明:利用SPA和CARS算法分别从全光谱的1024个波长中选取出31和104个特征波长;而基于特征波长建立的CARS-BP网络模型效果最优,其相关系数r_c为0.998,r_p为0.887,均方根误差RMSEC为0.026,RMSEP为1.767。这表明光谱技术结合化学计量学进行李子可溶性固形物含量的无损检测具有可行性。     

基于银镜的高灵敏表面增强拉曼光谱基底制备及其用于苏丹红Ⅰ的检测

利用银氨溶液和葡萄糖反应的银镜反应制备了表面增强拉曼散射(SERS)光谱银镜基底。扫描探针显微镜照片显示该基底表面颗粒较均匀,银粒粒径为100 500nm。将此基底插入含微量孔雀石绿水溶液中,测量吸附孔雀石绿分子的拉曼光谱,增强因子可达3.8×105。采用该基底对苏丹红Ⅰ进行了检测,得到了能够表征其毒性的特征拉曼频移。实验表明,利用表面增强拉曼光谱法检测苏丹红Ⅰ,方便快捷,有望成为苏丹红类物质的有效检测方法。     

反溶剂法制备姜黄素-高粱醇溶蛋白复合颗粒及其特性分析

以姜黄素为芯材,高粱醇溶蛋白为壁材,采用反溶剂法制备包埋姜黄素的高粱醇溶蛋白复合颗粒（简称复合颗粒）,并对其理化性质及稳定性进行研究。结果表明：姜黄素与高粱醇溶蛋白制备复合颗粒的最佳芯壁比（质量比）为1∶10,产品平均粒径为13.17?μm,电位为19.38?mV,得率为87.51%,包封率为62.61%,负载率为6.51%。相比于高粱醇溶蛋白颗粒,扫描电子显微镜显示：复合颗粒呈球形,但表面有多孔结构;红外光谱结果显示：复合颗粒位于1?534、1?655?cm－1等处的波峰均发生红移,α-螺旋含量减少,β-折叠含量增加。24?h紫外光照射后,高粱醇溶蛋白包埋的姜黄素光稳定性提高33%。复合颗粒的粒径和多分散性系数在30?d室内环境贮藏过程中均无明显变化,但在环境pH?5～6,颗粒易聚集。结果表明：高粱醇溶蛋白的包埋作用有益于提高姜黄素的稳定性,可为姜黄素和高粱醇溶蛋白的高值化利用提供理论依据。     

pH值偏移大豆油体-姜黄素复合乳液的物理特性及稳定性

以大豆油体为原料，利用油体天然水包油结构，借助pH值偏移法将姜黄素负载到油体油相内核中，制备姜黄素递送体系。通过乳液包封率、粒径、Zeta电位、显微结构等研究其包封特征，通过内源荧光光谱、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析其结构变化，探讨其贮藏稳定性、pH值稳定性及氧化稳定性。结果表明：大豆油体借助pH值偏移可成功包封姜黄素，pH值偏移为1.0时，大豆油体对姜黄素的包封效果最佳，乳液包封率为65.55%；脂滴形状规则、大小均匀，平均粒径为590.5 nm；氧化稳定性良好，但贮藏稳定性、pH值稳定性较差；蛋白质结构与未处理油体相比，未发生明显改变。本研究为天然油体运载姜黄素等亲脂性多酚物质提供一定参考。     

巧克力珍珠的呈色与成因属性

采用LA-ICP-MS、拉曼光谱仪、微型光纤光谱仪等分析测试仪器,对近期市场上出现的巧克力珍珠样品的化学成分、拉曼光谱、反射光谱、表面微观特征及其成因属性进行了初步研究。分析与测试结果表明,多数巧克力珍珠样品内发育有简单且着色外浅(棕黄色、棕红色)内深(灰黑色)的同心色带结构,深浅不一的棕红色色斑和灰白色色斑沿珍珠层表面相间无序分布;经低温加热漂白处理后,巧克力珍珠样品的化学成分、拉曼光谱、UV-NIS反射光谱特征均发生了不同程度的变化。其化学成分以相对富Cu和Pb、贫K为特征;1 276 cm-1处的拉曼谱峰红移至1 371 cm-1附近,1 583 cm-1处的拉曼谱峰则蓝移至1 545 cm-1附近,663 cm-1处的拉曼谱峰随之消失;在可见光波长范围内,c带(697 nm)的相对吸收强度骤减,a带向长波方向红移并与b带组合成一宽大舒缓的吸收谱带。初步证实,巧克力珍珠样品的颜色与其黑色素内共轭双键电子跃迁之间尚无直接的内在联系,主要归因于塔希提棕黑色珍珠内存在的钾色素蛋白经热变异作用所致。     

MTGase聚合大豆蛋白及其改性机理(III) MTGase聚合改性大豆蛋白机理

采用紫外光谱 (UV -spectrum)、荧光光谱 (fluorescencespectrum)以及红外光谱 (FT -IRspectrum)分析了SAPP以及其MTGase -聚合物的结构特征。紫外光谱结果显示MTGase催化SAPP导致它的多肽链的侧链结构发生了变化 ,Tyr和Trp残基的吸收峰红移说明其Cα原子的构型从非平面型转变为平面型 ,而荧光光谱显示MTGase催化导致SAPP的疏水区域暴露出来 ,而且还经历一个空间结构重排的过程 ,而红外光谱显示这种聚合作用还导致多肽链的二级结构发生较大的变化 ,即一部分的 β -折叠二级结构转变为以α -螺旋或无规卷曲。从蛋白质分子结构的角度 ,探讨了MTGase聚合SAPP的改性机理 ,指出其机理在于MTGase聚合导致了SAPP的空间结构发生了变化的缘故。     

MTGase聚合大豆蛋白及其改性机理(Ⅲ)MTGase聚合改性大豆蛋白机理

采用紫外光谱(UV—spectrum)、荧光光谱(fluorescence spectrum)以及红外光谱(FT—IR spectrum)分析了SAPP以及其MTGase-聚合物的结构特征。紫外光谱结果显示MTGase催化SAPP导致它的多肽链的侧链结构发生了变化,Tyr和Trp残基的吸收峰红移说明其Ca原子的构型从非平面型转变为平面型,而荧光光谱显示MTGase催化导致SAPP的疏水区域暴露出来,而且还经历一个空间结构重排的过程,而红外光谱显示这种聚合作用还导致多肽链的二级结构发生较大的变化,即一部分的β-折叠二级结构转变为以α-螺旋或无规卷曲。从蛋白质分子结构的角度,探讨了MTGase聚合SAPP的改性机理,指出其机理在于MTGase聚合导致了SAPP的空间结构发生了变化的缘故。     

多孔淀粉对姜黄素的吸附

采用扫描电子显微镜(scanning electron microscope,SEM)、傅里叶变换红外光谱(fourier transform infrared spectroscopy,FTIR)、粒度分布、吸附能力等指标对复合物进行表征;利用差示扫描量热法(differential scanning calorimety,DSC)和水溶性分析其稳定性;通过自由基清除能力及体外模拟胃液(SGF)和肠液(SIF)环境研究其释放特性。比较SEM、FTIR结果,可以看出姜黄素被吸附在多孔中并表现为化学吸附。姜黄素以不同的质量比进行吸附,0.4wt%的负载量实现了最高的吸附能力(3.67 mg/g),吸附后样品呈淡黄色,水溶性大大提高,保留大部分抗氧化能力,体外SGF和SIF中表明具有缓释效果。该研究成功制备马铃薯多孔淀粉-姜黄素复合物,且有望扩大姜黄素在食品工业中的应用。     

姜黄素对秀丽隐杆线虫降脂及抗氧化保护作用

本文研究姜黄素对秀丽隐杆线虫的降脂及抗氧化作用。将L1期秀丽隐杆线虫暴露于不同浓度姜黄素(12.5、25、50和100μmol/L)48 h后,以油红O染色线虫肠道脂肪,检测线虫体内甘油三酯的含量变化,同时测定线虫体内总超氧化物歧化酶活力(T-SOD)和丙二醛(MDA)含量的变化。结果表明,与二甲基亚砜(DMSO)对照组相比,姜黄素浓度在25μmol/L以上显著降低线虫肠道脂肪(p0.05),姜黄素浓度在50μmol/L以上降低线虫肠道脂肪作用极显著(p0.01),随着姜黄素浓度升高,线虫肠道脂肪含量逐渐降低。姜黄素浓度在25μmol/L以上极显著降低线虫体内甘油三酯和MDA含量(p0.01)。黄素浓度在50μmol/L以上极显著提高线虫体内T-SOD酶活力(p0.01)。综上所述,姜黄素浓度在25μmol/L以上对线虫具有降脂及抗氧化保护作用。     

Chemical modification of curcumin: Solubility and antioxidant capacity

The aim of this study was to develop a chemical method for demythylation of curcumin. The methoxy groups reduced solubility and low bioavailability of curcumin. The treatment of curcumin with hydrogen bromide or choline chloride increased cucumin water solubility from 1 mg/mL to 30 or 25 mg/mL, respectively. ¹HNMR spectra showed that the chemical shift of O-methoxy groups at 3.9 ppm disappeared upon chemical treatment of curcumin, and indicated that these groups were removed especially after hydrogen bromide treatment. The antioxidant activity of treated curcumin and untreated curcumin was measured using different in vitro assays (i.e., 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging, and phosphomolybdenum complex formation). A remarkable increase in 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging was observed as curcumin-hydrogen bromide > curcumin-Choline chloride > curcumin. The formation of phosphomolybdenum complex was found to increase in the order of curcumin-choline cloride > curcumin-hydrogen bromide > curcumin with EC₅₀ 30, 41, and 114 µg/mL, respectively. In conclusion, hydrogen bromide-treated curcumin could be used as potential antioxidant in new functional foods.     

Characterisation of sugar beet pectin fractions providing enhanced stability of anthocyanin-based natural blue food colourants

The bathochromic effect resulting from the addition of sugar beet pectin (SBP) to black currant juice, purified anthocyanins (ACN-E) and purified polyphenol extracts comprising both anthocyanins and non-anthocyanin phenolics (PP-E), respectively, were monitored by VIS spectroscopy at varying pH relevant to food formulations (pH 3.6–5.0). Furthermore, a low molecular pectic polysaccharide fraction (PPF) was isolated from SBP using 70% aqueous 2-propanol and further characterised with respect to its chemical composition and mineral content. The marked bathochromic effect was found to be due to the formation of anthocyanin–metal chelate complexes. Only at pH 5.0 SBP entailed a moderate bathochromic shift of 12 nm in model solutions containing ACN-E. This effect was enhanced in PPF model solutions resulting in a λ_max shift up to 50 nm, bringing about an intense blue colour. The bathochromic shift was boosted with increasing pH and upon purification of the anthocyanins. In contrast, after SBP and PPF addition to black currant juice, the bathochromic effect was almost annihilated. Model solutions were stored at 20 °C in the dark for 12 days, and optimum stability of the blue colour was observed at pH 5.0.     

类胡萝卜素在癸酸反胶束溶液中的电子吸收光谱特征变化

采集3种类胡萝卜素在癸酸反胶束溶液中的电子吸收光谱,进行特征分析。用四氢呋喃、丙酮和乙醇3种组装助剂分别构建癸酸反胶束溶液,番茄红素（开环碳氢化合物）、β-胡萝卜素（具环碳氢化合物）和玉米黄素（具环羟基化合物）分别溶解在其中后,采集各溶液在300～550 nm波长范围内的电子吸收光谱,分析其特征。结果表明：与3种类胡萝卜素在癸酸中的光谱特征相比,它们在癸酸反胶束溶液中的最大吸收波长（λmax）均有微小位移;具环类胡萝卜素的λmax发生红移,开环胡萝卜素的λmax发生紫移;同时,助剂极性的增强可使三者的吸光系数（A1%1 cm）减小。     

Temperature-dependent structure stability and in vitro release of chitosan-coated curcumin liposome

Liposome, a promising delivery system with phospholipid bilayer, could improve the water solubility of curcumin, which is a polyphenolic natural product with many bioactivities. However, the instability of liposome limits its development in application. In this study, the chitosan was used to protect the structure stability of phospholipid bilayer of curcumin liposome and control the sustained release rate of curcumin further. The temperature stability and phase transition were studied by differential scanning calorimetry. When curcumin molecule was embedded in phospholipid bilayer, the pre-transition temperature (50.40 °C) and main phase transition temperature (61.47 °C) decreased about 10 °C compared to it without curcumin, and phospholipid bilayer fluidity was increased. The pre-transition temperature was disappeared after chitosan coated on the surface of curcumin liposome. The thermal stability test and X-ray diffraction also indicate that high temperature could change the structure of liposome and chitosan could protect the curcumin from damage and leak. The in vitro release study showed that the cumulative release rate got faster with temperature increased and chitosan could decrease the release rate. These results may guide the potential application of chitosan-coated liposome as a carrier of curcumin in nutraceutical and functional foods.     

Complexation of curcumin with soy protein isolate and its implications on solubility and stability of curcumin

Curcumin, a natural polyphenolic food colourant, suffers a low bioavailability because of its low solubility and instability in aqueous solutions. Our study demonstrates that the food derived soy protein isolate (SPI) can form a complex with the curcumin. Fluorescence spectroscopy of the SPI–curcumin complex revealed that the complex is formed through hydrophobic interactions. Moreover, curcumin molecules quench the intrinsic fluorescence of SPI upon binding. Upon complexation, curcumin showed increased water solubility. Stability studies by UV spectroscopy showed that >80% of the curcumin was stable in the SPI–curcumin complex when dissolved in water, simulated gastric and intestinal fluids for 12 h, which would provide sufficient time for intestinal absorption. SPI–curcumin complex exhibits enhanced antioxidant activity and is capable of forming foam and emulsion, indicating its possible utilisation in food product formulation. This study suggests that SPI, being an edible protein, could be used as a material to encapsulate water-insoluble bioactive compounds in functional foods.     

Determination of boric acid in foods: Comparative study of three methods

Three methods for the determination of boric acid in foods were studied in detail, namely the titrimetric method using mannitol, and two colorimetric procedures using carminic acid or curcumin. Agar-agar strips, pickled mango, noodles and prawns were analysed and the repeatability, sensitivity and recovery of the methods compared. The titrimetric and curcumin methods gave mean values for boric acid which were significantly (P < 0·05) higher than those of the carminic acid method. Results with the titrimetric method did not differ from those with the curcumin method; the latter method gave good recoveries (～ 100%) for all four foods at all levels of addition. Analyses carried out on NBS Standard Material showed that the curcumin method gave the most accurate results. This method was also found to show the least internal variation both in terms of mean boric acid content and recovery. Furthermore, the method possessed practical advantages over the other two techniques. Based on the results obtained from the comparative studies, the curcumin method was found to be the most reliable and hence would be the method of choice for boric acid determination in foods.     

Curcumin antifungal and antioxidant activities are increased in the presence of ascorbic acid

The objective of this study was to evaluate the antifungal and antioxidant activities of curcumin, ascorbic acid and the mixture of these two compounds. For the antifungal assay, the minimum inhibitory concentrations (MIC) were determined using Candida strains (ATCC and clinical isolates). Curcumin alone inhibited growth of Candida albicans yeast cells, whereas ascorbic acid did not present effects. However, when the mixture of ascorbic acid and curcumin was assayed to determine the association of the two compounds, the curcumin MIC decreased 5- to 10-fold. In the antioxidant assays, the sum of the alone activities of curcumin and ascorbic acid were lower than the activity of the two-compound mixture. This study highlights the importance of the association between two common antioxidants in foods, to improve the antifungal and antioxidant activities of curcumin (in vitro), and can be applied to Candida spp. infection and diseases associated with oxidative stress.     

Effect of principal polyphenolic components in relation to antioxidant activity in conventional and organic red wines during storage

Many of the health beneficial physiological effects of the spice—turmeric (Curcuma longa), documented in recent years are attributable to the major flavour and colouring compound curcumin. Considerable decrease in the concentration of bioactive compound curcumin has been observed during the heat processing of turmeric. This study was aimed at understanding the nature of altered/degraded compounds formed from the bioactive spice compound—curcumin as a result of heat treatment encountered during domestic cooking. Among several of the degradation compounds of curcumin, three major ones were characterized as ferulic acid, vanillin and vanillic acid on the basis of their UV absorption, proton NMR spectra and mass spectral data of LC fractions, as well as by comparison of the three identified compounds with respective standards. The study confirmed the vulnerability of the diketone bridge in curcumin molecule to heat. In addition, formation of vanillic acid and vanillin indicated that the molecule is sensitive to heat at the first carbon atom of the alkyl chain which is connecting the two phenyl moieties.     

大鼠体内类姜黄素的组成变化

类姜黄素主要包括姜黄素、去甲氧基姜黄素及去二甲氧基姜黄素三种同系物。目的:探索类姜黄素在大鼠体内代谢中的组成变化。方法:姜黄根萃取物灌喂雄性SD大鼠,2h后收集血和肝脏,24h内收集粪便。应用C30-HPLC-PDA,测定和比较根萃取物、血清、肝脏和粪便中的类姜黄素组成。结果:粪便中姜黄素的组成与姜黄根中的一致,而血清和肝脏中的姜黄素比例显著上升。结论:姜黄素的比例在血清中开始上升。姜黄素是进入体内的主要组分。     

DECOMPOSITION OF TURMERIC CURCUMINOIDS AS AFFECTED BY LIGHT,SOLVENT AND OXYGEN1

Turmeric curcuminoids are important natural pigments but their instability limits their use in many foods. This study was conducted to examine light-induced degradation of turmeric curcumin as affected by solvent system and oxygen. The rate constants and half-lives were determined for purified curcumin, demethoxycurcumin and bis-demethoxycurcumin exposed to 1450 lux using reversed-phase HPLC. Rates of degradation of each pigment followed first-order kinetics. Differences in rate constants and half-lives between the individual pigments were minor in an acetic acid-NaCl solution; however, in methanol, large differences in stability to light of the individual pigment were observed. Stability of all the pigments to light was several fold greater in methanol than in acid brine. In methanol sparged with air, stability to photooxidation was curcumin > demethoxycurcumin > bis-demethoxycurcumin. In methanol, curcumin was more stable than the other curcuminoids when sparged with air than when sparged with nitrogen. In methanol sparged with nitrogen, demethoxycurcumin was the most stable pigment. All of the pigments were stable in the dark.