高效液相色谱法同时测定维生素D3和维生素K2的含量

目的建立高效液相色谱法同时测定维生素D_3和维生素K_2的含量的分析方法。方法以95%甲醇水:异丙醇=(98:2, V:V)为流动相,梯度洗脱,样品经C_(18)色谱柱(250 mm×4.6 mm, 5μm)分离,并于264 nm波长检测。结果维生素D3在浓度0.1282～1.2818μg/mL之间呈现良好的线性关系,r~2=0.9999,平均回收率为95.7%～100.7%,相对标准偏差为1.7%;维生素K_2在浓度0.51397～5.1397μg/mL之间呈现良好的线性关系,r=0.9999,平均回收率在97.3%～100.7%之间,相对标准偏差为1.3%。结论该方法操作简便、准确、重现性好,能同时测定维生素D_3和维生素K_2含量,可在实验室推广。     

复方营养混悬剂中维生素E含量测定方法的研究

目的 建立高效液相色谱法（HPLC）测定复方营养混悬剂中维生素E的含量。方法 采用Merck Hibar C18(4.6 mm×250 mm,5μm)色谱柱,以甲醇为流动相,流速1.0 ml/min,检测波长280 nm。结果 维生素E质量浓度在0.01～0.2 mg/ml范围内线性关系良好（r=0.9999）;检测限为0.45μg/ml;3个浓度回收率均在92.0%～109.1%;重复性RSD(n=6)为1.57%。结论 该方法可作为复方营养混悬剂中维生素E的定量分析方法。     

无花果中维生素C含量的测定

目的 采用分光光度法测定无花果和无花果干中维生素C的含量。方法 选取一定浓度维生素C标准液进行波长扫描, 确定维生素C的最大吸收波长, 将待测样品匀浆处理后在此波长下进行分光光度测定。结果 维生素C的最大吸收波长为520 nm, 校准曲线方程Y=0.0208X+0.001(r2=0.9998), 无花果和无花干果中维生素C含量分别为69.08 mg/100 g和64.06 mg/100 g, 加标回收实验中回收率均在90%以上。结论 无花果中含有较高的维生素C, 且无花果维生素C含量高于无花果干中维生素C含量。     

高效液相色谱法测定刺梨果酒中维生素C含量

建立了刺梨果酒中维生素C含量的高效液相色谱分析方法,在0.5~20μg/mL浓度范围内,具有良好的线性关系,相关系数r=0.99994,重现性良好(RSD=0.73%,n=6),检出限为0.99 mg/L。实验采用4种酸作为提取剂,并考察了不同酸浓度下提取维生素C含量的变化。结果表明,4种酸的加标回收率良好,为96.4%~104.8%;草酸、偏磷酸在8%的浓度下提取效果最佳,盐酸在1%的浓度时效果最好,三者的最佳测定结果相近;磷酸提取效果不好,其最高测定结果为最佳组的76.5%。本方法简单、快捷、重现性好,适用于刺梨果酒中维生素C的检测。     

新型紫外可见光法测定沙田柚中维生素C的含量

目的建立一种测定沙田柚中维生素C含量的新方法。方法采用紫外turn on法在510 nm处测定维生素C含量。优化氯化铁和邻菲啰啉的浓度、反应时间等因素。结果获得氯化铁最佳浓度是0.01 mol/L,反应时间为1 h。在最佳条件下,获得校准曲线方程Y=2971X+0.0218(r=0.9997),灵敏度为0.1μg/m L,并用于测定桂东南的沙田柚中的维生素C,结果显示沙田柚中维生素C的含量为78.58 mg/100 g,该结果与文献报道一致。结论该方法快速、准确、灵敏,适合水果、蔬菜的维生素C含量的测定。     

高效液相色谱法测定桃汁饮料中维生素C的含量

建立了一种高效液相色谱测定桃汁饮料中维生素C含量的方法。采用Agilent C18色谱柱分离,以0.05mol/LKH2PO4∶甲醇体积比为96∶4的混合液作流动相,流速为0.6mL/min,检测波长为288nm。维生素C在浓度为5～80μg/mL范围内浓度与峰面积有良好的线性关系,线性回归方程为y=11.2471x-16.6383,相关系数为0.9989,测定相对标准偏差为1.49%。该测定方法简便、快速、准确、稳定,适合于测定水果、蔬菜、饮料中的维生素C的含量。     

富含维生素C食品中总黄酮含量的测定

目的建立富含维生素C食品中总黄酮的定量分析方法,解决维生素C干扰络合法测定总黄酮的问题。方法使用Waters Sep-Pak C18固相萃取小柱对提取物进行脱脂和去除色素,D101大孔固相萃取(SPE)小柱去除维生素C,得到总黄酮洗脱液,用硝酸铝比色法进行测定,检测波长510 nm。结果总黄酮在0~48μg/m L具有良好的线性关系,相关系数为0.9998,相对标准偏差(RSD)小于5%,三个水平的添加回收率为95.31%~98.38%。考察三种不同总黄酮和维生素C比例含量的食品(Vc:总黄酮=1:1,2:1,10:1),发现随着维生素C含量增加,对总黄酮测定结果的影响越大。因此,对样品进行前处理,可以测得较为准确的总黄酮含量。结论本方法样品前处理简单、环保、快速、准确,适用于富含维生素C食品中总黄酮的含量测定。     

维生素B1、B2含量测定方法比较

目的:比较维生素B1、B2含量测定方法。方法:采用紫外分光光度法中三种不同方法测定维生素B1、B2含量。结果:1、按E值测标示量维生素B1:98.3±2.51,维生素B2:94.8±0.308,复合维生素B片中维生素B1:102.1±1.70,维生素B1平均回收率为100.4%,RSD为2.13%(n=6),维生素B2平均回收率为94.9%,RSD为6.5%(n=6)。2、标准曲线法维生素B1、B2浓度分别在3～18、1～8μg/ml范围内,均呈良好线性关系,标示量分别为:102.9±0.661,98.4±0.152。3、双波长法测维生素B1标示量:94.2±1.97。结论:三种方法用于维生素B1、B2含量测定,操作简便、快速、准确,精密度好。     

果蔬中总多酚和维生素C测定方法优化的研究

目的建立一种简单、准确地测定果蔬中总多酚和维生素C含量的方法。方法采用Oasis HLB固相萃取柱富集待测物质,用纯水洗脱回收水溶性干扰物质,用甲醇洗脱回收多酚类物质,加热水洗脱液除去其中的维生素C,优化福林酚比色法,测定总多酚和维生素C的含量。结果该方法的线性方程为Y=0.0118X+0.0045,R2=0.9989,确定福林酚比色法的条件为:在760 nm处测定,福林酚试剂:水(1:1),7.5%的Na2CO3溶液,温度为20~30℃,静置60 min。通过采用福林酚比色法分别测定原料提取液(RE)和水洗脱液(WE)中还原性物质的含量,取其差值作为样品总多酚含量。同时,测定加热处理水洗脱液(HWE)中还原性物质的含量,取其与WE测定结果的差值作为样品维生素C的含量。结论此方法简便实用、条件易满足,分析结果可靠,可应用于果蔬总多酚和维生素C含量的测定。     

婴幼儿奶粉中维生素C检测方法的研究

目的 应用荧光分光光度计对婴幼儿乳品中维生素C的含量进行测定。方法 以婴幼儿奶粉为例, 依据国家标准GB 5413.18-2010《食品安全国家标准 婴幼儿食品和乳品中维生素C的测定》, 应用日立F-4600型荧光分光光度计测定婴幼儿乳品中维生素C的含量。结果 线性方程为Y=457.79X 28.877, 相关系数为0.9993, 方法检出限为0.1 mg/100 g。在50 mg/100 g、100 mg/100 g 两个加标水平下, 加标回收率为91.8%~101.8%, 相对标准偏差为0.36%~0.85%(n=6)。结论 此方法操作简便, 线性良好是测定食品中维生素C含量的理想方法。     

紫外光度法测定食品中的还原型维生素C

本文以Ｆｅ（３＋）将在２６５ｎｍ有最大紫外吸收的还原型维生素Ｃ选择性地氧化为在２６５ｎｍ无吸收的氧化型维生素Ｃ，实现对食品样品中多种紫外干扰成分的本底校正，建立了一种测定食品中还原型维生素Ｃ的新方法。还原型维生素Ｃ含量在０～３００ｕｇ／２５ｍｌ范围内符合比耳定律，ｒ＝０．９９９９５。运用本法实际测定了马铃薯、番茄等食品中的还原型维生素Ｃ的含量，回收率在９７．５～１０１．２％之间，相对标准偏差在０．７５～１．２６％之间，测定结果与２，６－二氯靛酚法基本一致。     

雪莲果发酵酒的防褐变技术研究

在不影响雪莲果果酒发酵过程和品质的前提下,通过添加抗坏血酸、柠檬酸、蜂蜜、菠萝汁等抗褐变剂来解决雪莲果果酒生产中的褐变问题,得到营养成分损失少、风味佳、色泽鲜亮的雪莲果果酒。结果表明,抑制雪莲果褐变程度的先后顺序为柠檬酸>抗坏血酸>菠萝汁雪莲混合比,蜂蜜在雪莲果酒陈酿期会产生深色物质,不适宜作为雪莲果果酒的抗褐变剂。影响感官的顺序分别为菠萝汁雪莲混合比>抗坏血酸>柠檬酸,最后得出抑制雪莲果酒褐变的最佳组合为抗坏血酸的添加量1.00%,柠檬酸的添加量0.75%,菠萝雪莲混合比为1:4。     

Effect of Antioxidant Application Methods on the Color, Lipid Oxidation, and Volatiles of Irradiated Ground Beef

ABSTRACT:  Four antioxidant treatments (none, 0.05% ascorbic acid, 0.01%α-tocopherol + 0.01% sesamol, and 0.05% ascorbic acid + 0.01%α-tocopherol + 0.01% sesamol) were applied to ground beef using either mixing or spraying method. The meat samples were placed on Styrofoam trays, irradiated at 0 or 2.5 kGy, and then stored for 7 d at 4 °C. Color, lipid oxidation, volatiles, oxidation-reduction potential (ORP), and carbon monoxide (CO) production were determined at 0, 3, and 7 d of storage. Irradiation increased lipid oxidation of ground beef with control and ascorbic acid treatments after 3 d of storage. α-Tocopherol + sesamol and ascorbic acid +α-tocopherol + sesamol treatments were effective in slowing down lipid oxidation in ground beef during storage regardless of application methods, but mixing was better than the spraying method. Irradiation lowered L *-value and a *-value of ground beef. Storage had no effect on lightness but redness decreased with storage. Ascorbic acid was the most effective in maintaining redness of ground beef followed by ascorbic acid +α-tocopherol + sesamol. Irradiation and storage reduced the b *-value of ground beef. Irradiation lowered ORP of ground beef regardless of antioxidants application methods, but ORP was lower in beef with mixing than spraying method. Beef sprayed with antioxidants produced more hydrocarbons and alcohols than the mixing application, but ascorbic acid +α-tocopherol + sesamol treatment was effective in reducing the amount of volatiles produced by irradiation. Therefore, mixing was better than the spraying method in preventing lipid oxidation and maintaining color of irradiated ground beef.     

二苯胺磺酸钠褪色光度法测定饮料中还原型维生素C

在硫酸介质中,二苯胺磺酸钠可被过氧化氢氧化生成二苯联苯胺磺酸紫。利用在酸性条件下还原型维生素C（L—VC）对二苯联苯胺磺酸紫的褪色效应建立了褪色光度法测定还原型维生素C的方法。最大吸收波长为780nm,还原型维生素C浓度在0～24μg／ml范围内与溶液的褪色程度（ΔA）服从比耳定律,回收率为94．5％-100．8％     

The effects of ascorbic acid, taurine, carnosine and rosemary powder on colour and lipid stability of beef patties packaged in modified atmosphere

This research was aimed at evaluating the inhibition of oxidative changes of beef patties packaged in modified atmosphere (70% O₂+20% CO₂+10% N₂) by natural antioxidants: ascorbic acid (500 ppm), taurine (50 mM), carnosine (50 mM), rosemary powder (1000 ppm) and their combinations with the first. Beef patties stored at 2±1°C for 20 days were evaluated for colour (L*, a*, b*, C* and H*), TBARS, metmyoglobin formation (% of total myoglobin), psychrotrophic microbial counts and sensory odour and discolouration. Rosemary, either alone or with ascorbic acid, was highly effective in inhibiting both metmyoglobin formation and lipid oxidation; sensory analysis was in agreement with these results. Ascorbic acid, ascorbic acid+taurine and ascorbic acid+carnosine treatments showed a limited inhibitory effect of myoglobin oxidation, while carnosine and carnosine+ascorbic acid were effective in inhibiting lipid oxidation. Taurine alone failed to exert any antioxidant effect. Principal components analysis confirmed these results.     

Stability of patulin in a juice-like aqueous model system in the presence of ascorbic acid

In the present study, the stability of patulin in an aqueous juice-like model system was investigated. At acidic pH, the presence of ascorbic acid reduced the stability of patulin. After 34 days, patulin was reduced to 30% of its initial concentration in the presence of ascorbic acid compared to 68–71% in samples without ascorbic acid. Conditions during storage (presence of light, oxygen and/or metal ions) influenced the stability of patulin. Furthermore, it was possible to induce degradation of patulin by either generating hydroxyl radicals or by adding the rather stable radical diphenyl-1-picrylhydrazyl (DPPH). Data from the present study indicate that patulin is decomposed by free radicals generated by oxidation of ascorbic acid to dehydroascorbic acid. Rapid oxidation of ascorbic acid in the presence of oxygen, catalysed by free metal ions, resulted in a decrease of patulin. After complete oxidation of ascorbic acid, no further patulin degradation was observed. In contrast, slow oxidation of ascorbic acid in the presence of metal-chelators induced a continuous, slow oxidation of patulin. Due to low oxygen content in the headspace of a food package, addition of ascorbic acid to products such as apple juice, prior to filling, cannot be considered as an effective decontamination strategy.     

Destructive Effect of Aspartame on Ascorbic Acid in Cu-catalyzed Solutions

The effect of aspartame on the early stage of ascorbic acid oxidation in solutions was studied by measuring ascorbic acid retention in an open system at 30°C and the oxygen uptake in a closed system at 33°C. Comparisons were also made between aspartame (0.06% and 0.12%) and sucrose (10% and 20%) in Cu-catalyzed and noncatalyzed solutions at 30°C. Copper activity in aspartame solution was measured by using a cupric ion selective electrode. Aspartame increased the rate of ascorbic acid oxidation in all tested solutions. In the presence of copper the oxidation rate of ascorbic acid was significantly higher in aspartame solutions than in sucrose solutions despite the fact that aspartame showed Cu-complex capacity in solution.     

响应面法优化天然抗氧化剂抑制调理鸡排褪色和脂质氧化工艺

目的：为延缓调理鸡排贮藏期间的褪色和脂质氧化,研究迷迭香提取物和抗坏血酸对其红度（a*）值和脂肪氧化的影响。方法：采用单因素试验结合中心组合试验设计,对腌制液中迷迭香提取物和抗坏血酸的添加量进行优化,以a*值和脂肪氧化值作为响应值筛选最佳配比。结果：单因素和响应面试验结果表明,迷迭香提取物和抗坏血酸添加量对鸡排a*值和脂肪氧化值具有显著影响。以a*值和脂肪氧化值为响应值,得到2 个二次多项式回归方程,决定系数R2分别为0.932 0、0.886 3,失拟项的P值均大于0.05,说明2 个模型均建立有效。迷迭香提取物的一次项（P＜0.05）、抗坏血酸的一次项和二次项（P＜0.01）对鸡排a*值影响显著;迷迭香提取物的一次项（P＜0.01）和抗坏血酸的二次项（P＜0.05）对脂肪氧化影响显著。结论：当设定a*值最高、脂肪氧化值最低时,获得最佳复配参数为迷迭香添加量0.198 g/kg、抗坏血酸添加量0.255 g/kg,经验证实验测得50 d后调理鸡排的a*值为21.88,脂肪氧化值为0.59 mg/kg,与拟合结果一致。     

雪莲果防褐变技术的研究

从雪莲果块茎中提取多酚氧化酶(Polyphenol Oxidase,PPO),采用分光光度法对其最大吸收波长最适反应温度进行研究,还研究了VC、氯化钠、柠檬酸、柠檬汁、橘子汁对雪莲果PPO活性的影响。结果表明:雪莲果多酚氧化酶最大吸收波长为400nm,最佳反应温度为30℃。氯化钠、抗坏血酸、柠檬酸、柠檬汁、橘子汁都有抑制褐变的效果。组合抑制剂抑制褐变效果比单一抑制剂好且最佳组合抑制剂为1.5%氯化钠+0.5%抗坏血酸+1.5%柠檬酸+10%柠檬汁。     

几种天然抗氧化剂对牡丹籽油氧化稳定性的影响

采用Schaal烘箱耐热试验法,以人工合成抗氧化剂二叔丁基羟基甲苯、丁基羟基茴香醚和特丁基对苯二酚等为阳性对照,研究茶多酚、苹果多酚、葡萄多酚、野葡萄多酚、牡丹籽多酚、生育酚、脂溶性迷迭香提取物和水溶性迷迭香提取物等8种天然抗氧化剂及2种增效剂(维生素C和柠檬酸)对牡丹籽油氧化稳定性的影响。研究以过氧化值为评价指标。结果表明,在国家允许添加量范围内,几种天然抗氧化剂均能提高牡丹籽油的氧化稳定性,但单独使用的效果要弱于人工合成抗氧化剂特丁基对苯二酚。其中脂溶性迷迭香提取物抗氧化效果较为理想,与合成抗氧化剂特丁基对苯二酚效果接近。维生素C与柠檬酸是抗氧化剂的良好增效剂,协同抗氧化作用显著,且维生素C的效果优于柠檬酸。复合抗氧化剂的抗氧化效果优于同等质量浓度的单一抗氧化剂,复合添加0.01%脂溶性迷迭香+0.01%茶多酚+0.02%维生素C、0.01%牡丹籽多酚+0.01%苹果多酚+0.02%维生素C和0.01%脂溶性迷迭香+0.01%茶多酚+0.02%柠檬酸均能显著减缓牡丹籽油的氧化速度,可使牡丹籽油的贮藏时间明显延长。