糕点饮料中维生素C的分光光度测定法

关于饮食品中维生素C的测定,已提出了荧光法,2,4-二硝基苯肼比色法,2,6-二氯酚靛酚滴定法等多种方法。荧光法专一性强,但需要贵重的荧光分光光度计,目前尚无法普遍     

食品中抗坏血酸的荧光测定法

<正> 测定食品中总抗坏血酸,目前国内最常使用的方法是2,4-二硝基苯肼比色法。该方法操作手续比较繁复,且费时间。荧光分析法测定抗坏血酸,在国外已经获得应用,国内虽然介绍了测定食品特别是果汁中总抗坏血酸的荧光分析法,但尚未见实际应用的报道,本文应用荧光法测定了柑桔鲜汁和猕猴酒中总抗坏血酸,变异系数为1.06％～1.17％,回收率     

荧光分光光度法测定蔬菜中Vc含量

Vc经活性炭处理后,可氧化为顺式脱氢型,此化合物的α-酮基与邻苯二胺反应形成喹喔啉,在激发波长351nm,发射波长432nm处测定其荧光强度。采用外标法(标准曲线),所作标准曲线相关系数为0.9993,相对标准偏差小于0.86%,回收率在97%～99.2%之间,此法精确度好、回收率高,适合于蔬菜中微量Vc的含量测定。     

油脂中羰基化合物的分光光度法测定研究

本文报导一种测定油脂羰基值的分光光度法。该方法直接用油脂与2,4-二硝基苯肼的氯仿饱和溶液反应生成橙红色的2,4-二硝基苯腙,在最大吸收波长455nm处测量吸光度,然后换算成羰基值作为评价油脂酸败程度的指标。实验表明,该方法用于评价油脂酸败程度简便灵敏且结果满意。     

测定丙酮酸发酵生产产量的几种化学方法的比较

通过4种测定丙酮酸的化学方法（乳酸脱氢酶法、2,4-二硝基苯肼法、硝酸铁化学比色法、紫外分光光度法）回收率及重现性的试验比较,找出各种方法测定丙酮酸的适用范围及优缺点,为试验室测定丙酮酸的方法提供理论的依据。     

果蔬汁中V_C的测定

建立了一种利用荧光分光光度计检测果蔬汁中VC检测的新方法,用荧光光谱检测VC含量的最佳激发和发射波长分别为342 nm和430 nm。     

2,4-二硝基苯肼法测定果蔬VC含量条件探索

对2, 4-二硝基苯肼法测定果蔬VC含量的条件进行探索。结果表明,活性炭最佳用量1.8～2.2 g;显色剂2, 4-二硝基苯肼最佳用量2.0 mL,显色时间3～3.5 h;测定波长523 nm,且在2 h内吸光度无显著变化;抗坏血酸质量浓度在0～80μg/m L范围内遵守朗伯-比尔定律,表观摩尔吸光系数ε=2.455×10~3 L/(mol·cm),桑德尔灵敏度S=0.071 74。利用所得出的试验条件测定西红柿、辣椒、草莓和樱桃中VC含量,与碘量法和2, 6-二氯酚靛酚法相比,试验结果令人满意。     

用库仓滴定法测定食品中抗坏血酸的研究

<正> 众所周知,抗坏血酸是人体不可缺少而又不能在人体中合成的一种维生素,抗坏血酸参与机体的代谢过程,可帮助酶将胆固醇转化为胆酸而排泄,减慢毛细管的脆化,增强机体的抵抗能力,而且抗坏血酸还可用来治疗多种疾病。前人已利用各种方法来测定抗坏血酸的含量,这些方法是用于测定还原型抗坏血酸的2,6—二氯靛酚滴定法,用于测定抗坏血酸总量的2,4—二硝基苯肼比色法,荧光测定法,改良染料法,以及库仓滴定法。但前人所     

苹果汁荧光特性的研究

利用荧光分光光度计研究了4种100％苹果汁的荧光特性,结果表明4种市售100％苹果汁都具有荧光特性.对4种苹果汁进行了3D扫描,由图谱分析后可得荧光分光光度计的激发波长为379 nm,发射波长为463 nm,此波长下测定苹果汁的荧光特性最为合适.     

凝胶糖果中Vc含量检测方法比对

采用2,4-二硝基苯肼比色法与高效液相色谱法检测凝胶糖果中Vc的含量,结果发现液相色谱法测定值略小于比色法测定值。     

Effect of Ascorbic Acid on the Properties of Ammonia Caramel Colorant Additives and Acrylamide Formation

Ammonia caramels are among the most widely used colorant additives in the food industry. They are commonly prepared through the Maillard reaction and caramelization of mixtures of reducing sugars with ammonia or ammonium salts. Antioxidants are known to inhibit acrylamide formation during the Maillard reaction, and they may affect the properties of the ammonia caramel products. Thus, the objective of this study was to investigate the effect of the antioxidant ascorbic acid on the properties of ammonia caramel. A mixture of glucose and ammonia was allowed to react at 120 °C for 60 min in the presence of ascorbic acid at final concentrations of 0 to 0.08 M. The ammonia caramels obtained from these reactions were all positively charged. As the concentration of ascorbic acid increased, the color intensity of the ammonia caramel showed a decreasing trend, while the intensity of the fluorescence and total amount of pyrazines in the volatiles showed a tendency to increase. The addition of ascorbic acid did not result in obvious changes in the UV‐visible spectra of the ammonia caramels and the types of pyrazines in the volatiles were also unchanged. It is noteworthy that the addition of 0.02 to 0.08 M ascorbic acid did reduce the formation of the by‐product acrylamide, a harmful substance in food. When the concentration of ascorbic acid added reached 0.04 M, the content of acrylamide in the ammonia caramel was 20.53 μg/L, which was approximately 44% lower than that without ascorbic acid. As a result, ascorbic acid can be considered to improve the quality and safety of ammonia caramels.     

紫胶色酸A的荧光性质及其在检测中的应用

考察紫胶色酸A的荧光性质和影响因素,探索其对金属离子的识别作用以及在实际检测中的应用。结果表明,溶剂的化学特性和极性、其自身浓度以及溶液的pH值都会影响紫胶色酸A的荧光强度和发射波长;Cu2＋、Fe3＋、Fe2＋和Pb2＋使紫胶色酸A的荧光猝灭,而Zn2＋和Al3＋使其荧光增强,其中Al3＋体现出显著增强紫胶色酸A荧光强度的特异性,其他金属离子对其荧光强度几乎没有影响。在Al3＋（0.04?mol/L）存在的条件下,紫胶色酸A的荧光强度与其浓度呈良好的线性关系。应用实验结果表明,以Al3＋为标准液,用荧光法检测两种不同饮料中添加的紫胶色酸A的含量,样品回收率在95.0%～109.3%之间,相对标准偏差在1.9%～5.4%之间。本实验开发了一种新的检测紫胶色酸A的方法,该方法具有实际应用价值。     

氨基酸与丙二醛反应体系的荧光光谱

采用荧光光谱法研究氨基酸与丙二醛的反应,考察反应时间、pH和浓度对赖氨酸与丙二醛反应体系发射光谱的影响,并对不同种类的氨基酸与丙二醛反应进行比较。结果表明,氨基酸与丙二醛反应生成了400nm激发、460nm发射的荧光物质,该反应在中性条件下易于进行,并随时间延长产物增多,反应体系中,丙二醛浓度高于赖氨酸浓度有利于生成荧光产物。不同氨基酸与丙二醛反应产物的荧光强度差异明显,精氨酸、赖氨酸、甘氨酸、苯丙氨酸、组氨酸等五种氨基酸易与丙二醛反应,脯氨酸、羟脯氨酸、色氨酸未能与丙二醛反应生成荧光物质。      

Fluorescence inner-filtering correction for determining the humification index of dissolved organic matter

The use of fluorescence spectrometry has been suggested as a simple method to determine the extent of natural organic matter humification by quantifying the red-shifting of fluorescence emission that occurs with increasing humification. Humification indices are calculated by dividing fluorescence intensity at longer wavelengths by intensity at shorter wavelengths. These indices calculated without any specific efforts to standardize dissolved organic matter (DOM) concentration will result in index values thatvary with DOM concentration due to fluorescence innerfiltering effects. This study critically evaluated the effect of DOM concentration on humification index determination using organic matter isolated from field corn extract, soil: water extract, and soil fulvic acid. The results show that humification index values are sensitive to DOM concentration of the solution and are linear with respect to transmittance of the solution at the 254 nm used as the excitation wavelength. An approximate correction for DOM is to exploit the linear nature of the regression fit and to determine index values at the extrapolated 100% transmittance value. An exact correction using explicit correction factors for both primary and secondary innerfiltration effects was shown to give humification index values that are concentration invariant when absorbance of the solution at 254 nm was less than approximately 0.3 unit. Defining the humification index as the fluorescence intensity in the 300-345 nm region divided by the sum of intensity in the 300-345 nm and 435-480 nm regions was statistically advantageous. This study suggests that for quantitative results which can be used to compare humification of natural organic matter across different studies, correction of the fluorescence emission spectra for innerfiltration effects is needed.     

钼蓝比色法测定还原型维生素C

食品中还原型维生素 Ｃ（Ｌ－ＶＣ）能将磷钼酸盐定量还原成蓝色的铝蓝化合物,通过分光比色的方法即可测定出食品中还原型维生素的含量。本文进一步详细的研究了影响显色反应的各种因素,结果表明,在酸性介质中,Ｖｃ与磷钼酸盐的反应速度快,环境因素对其影响小,且反应体系的吸光度稳定。在本实验条件下,ＶＣ浓度在８～２８ｕｇ／ｍｌ的范围内服从比耳定律。在此范围内,回归方程为：Ｙ＝０．０１８９２９２＋３６８６．３１Ｘ（ｍｏｌ／Ｌ）,相关系数ｒ＝０９９８２６,间按摩耳系数为 ３．６８６３１×１０~３,最大吸收波长 ７０５ｎｍ,回收率在９８．５０％～９８．６３％之间,本方法具有简便、快速、准确的特点。     

氧化胭脂虫红酸用于蘑菇中的铁离子检测

为进一步开发胭脂虫红酸的荧光检测应用，以胭脂虫红酸为原料，高碘酸钾为氧化剂，通过乙醇/水热法一步合成水溶性可发射蓝色荧光的氧化胭脂虫红酸（oxidized carminic acid，OCA）。通过傅里叶变换红外光谱法和X射线光电子能谱分析表明OCA结构中含有共轭芳香环结构和丰富的含氧官能团，透射电子显微镜和动态散射光测试表明其平均粒径约为7.5 nm。光学测试表明，OCA的荧光发射位于380～620 nm区间，最大激发波长为336 nm，最大发射波长为445 nm；其荧光在pH 1～9的溶液和含有不同阴离子的盐溶液中稳定性良好；紫外-可见光测试显示其在波长225 nm处有最大吸收峰。OCA对铁离子（Fe3＋）有良好的选择性，加入Fe3＋会导致其荧光强度明显降低，荧光发射峰积分面积减小率与Fe3＋质量浓度在11.2～56.0 mg/L范围内具有良好的线性关系，检出限为2.5 mg/L。应用结果表明，基于OCA作为荧光传感器的荧光检测方法用于实际样品中Fe3＋的检测，样品回收率在95.3%～110.4%之间，相对标准偏差在2.3%～4.6%之间，表明该方法可用于香菇、白菇和杏鲍菇等蘑菇中Fe3＋的含量检测，方法可靠。     

The influence of ascorbic acid on the composition, colour and flavour properties of a Riesling and a wooded Chardonnay wine during five years' storage

This paper presents the results from an investigation to assess the development of a Riesling and a wooded Chardonnay wine over five years. The wines were bottled either with or without added ascorbic acid and stored under controlled temperature and humidity conditions. Ascorbic acid addition to wine at bottling had little effect on wine aroma and flavour when the wines in this study had been in bottle for 6 months or less. For both wines, at bottle storage times of 3 years or more, addition of ascorbic acid at bottling resulted in wines with no difference in aroma or less oxidised and/or more fresh fruity aromas, even if all the ascorbic acid had been depleted at the time of assessment, compared to wines without addition of ascorbic acid at bottling. In terms of colour, for the Chardonnay wines, the effect of ascorbic acid addition at bottling assessed between two weeks and two years after bottling suggested that wines without addition were browner and had more overall colour intensity. For the Riesling wines, ascorbic acid addition had no significant effect on brownness and overall colour intensity although the Riesling wines with ascorbic acid were generally higher in yellow colour. The A₄₂₀ measurements, which are widely used to estimate the brown colour of wines, did not always appear to correlate with the brown scores obtained by visual assessment or colour measures by CIELAB when wines with and without ascorbic acid addition were compared together. For both wines, after three and five years storage, the concentration of the antioxidant sulfur dioxide was either little different or else slightly(statistically significantly) higher in wines to which ascorbic acid was added at bottling than those without addition.     

吸光光度法标定抗坏血酸标准溶液

本文报道了标定抗坏血酸标准溶液的新方法。实验结果表明,在酸性条件下,KIO_3能严格定量地转变成I_2,I_3~-的最大吸收波长在287nm处,用722型光栅分光光度计测定,最大吸收波长为352nm,于287nm和352nm处,I_3~-的摩尔吸光系数为—4.11×10~4L/mol·cm和2.57×104L/tool·cm;I_3-的吸光度随抗坏血酸加入量的增大在一定深度范围内遵守Beer定律;与滴定法比较,标定结果的符合率分别为97.4～104.8％和98.4～102.9％;重复测定的变异系数分别为1.060％和1.08％。本法标定抗坏血酸溶液,具有灵敏、简便、准确、快速等特点。     

纸质食品包装材料中荧光增白剂迁移规律的研究

采用浸泡方式提取纸质食品包装中的荧光增白剂,并以VBL为标准物质建立了对纸质食品包装中荧光增白剂定量检测的方法。该方法激发波长345nm,发射波长430nm;定量标准曲线为y=121.58x-0.6535,在0～0.8μg/ml范围内线性相关性R2=0.9997;回收率在78%～90%之间,三种加标浓度测定值的相对标准偏差RSD均小于3%,可满足检测要求。通过对荧光增白剂迁移规律的探讨,发现浸泡时间到2h时,迁移量会出现大的跳跃;温度升高会使荧光增白剂的迁移量增大;VBL在酸性条件下的荧光强度明显下降,而碱性条件下荧光强度会增强。     

馥郁香型白酒三维荧光光谱特征分析研究

采用Aqualog荧光光谱仪测定馥郁香型湘泉、酒鬼、内参酒三维荧光光谱，并分析其荧光光谱特征。结果表明，激发波长在200～300 nm范围激发时，湘泉酒有3个荧光峰，分别在λex/λem(224 nm/305 nm)、λex/λem(242 nm/426 nm)和λex/λem(299 nm/408 nm)左右；酒鬼酒有2个荧光峰，分别在λex/λem(224 nm/305 nm)和λex/λem(242 nm/426 nm)左右；内参酒只有一个荧光峰，在λex/λem(227 nm/305 nm)左右。三种酒在激发波长305 nm左右的荧光峰强度逐渐降低。在激发波长300 nm以上激发时均出现了两个荧光峰，分别在λex/λem(359 nm/433 nm)和λex/λem(371 nm/436 nm)左右，是三种酒类的主荧光峰，反映多种微量风味物质与乙醇-水通过氢键形成团簇分子荧光峰特征，两个荧光峰强度随着白酒等级增加呈现逐渐增强的趋势，体现着馥郁香型白酒荧光光谱特征。