离子色谱-脉冲安培检测法测定酱油中的糖

以氢氧化钠为淋洗液,在CarboPac PA10高容量阴离子交换柱上分离,脉冲安培检测了几种常见类型酱油中阿拉伯糖、半乳糖、葡萄糖、木糖、果糖及蔗糖,其检出限(25μL进样,S/N=3)为2～8 μg·L-1.这六种糖均具有较宽的线性范围(0.02～30 mg·L-1),酱油测定结果的相对标准偏差在0.11%～4.10%之间,六种糖类的加标回收率在94.1%～103.8%之间.该方法检测糖具有简便快捷、分离效果好、无需衍生、灵敏度高等优势,适用于各种酱油中糖组分的分析.     

固相萃取-高效液相色谱法测定酱油中10种防腐剂

文章建立了固相萃取-高效液相色谱法测定酱油中10种防腐剂的检测方法.方法采用90%甲醇提取、沉淀后,滤液经PEP-SPE固相萃取柱净化,采用Plus C18柱:5 μm,250 mm×4.6 mm;流动相:乙腈为0.01 mol/L磷酸二氢钾溶液(pH=4.0)(梯度洗脱).流速:1.0 mL/min,检测波长230 nm和254 nm;柱温30℃;进样量10μL.该方法的检出限在1.0～2.0 mg/L,线性范围1.0～100.0 mg/L,加标回收率72.8%～100.9%之间.相对标准偏差(RSD)0.42%～6.87%(n=4),该方法简单、快速、灵敏度高,并具有良好的精密度与准确度,可作为酱油中检测这10种防腐剂的有效定量方法.     

液相色谱-串联质谱联用法测定酱油中T-2毒素残留

目的:研究以液相色谱-串联质谱联用法测定酱油中T-2毒素含量的方法。方法:液相色谱-串联质谱法。用乙腈-0.1%甲酸溶液提取酱油,经C18净化,电喷雾正离子多反应监测(MRM)模式检测。结果:T-2毒素在1～25μg/L的系列浓度范围呈线性相关,酱油中T-2毒素的检测限为2.0μg/kg,定量限为5.0μg/kg,在2～20μg/kg的添加浓度范围内平均回收率为85.5%～98.2%。结论:该方法灵敏度高,重现性好,可作为酱油中T-2毒素残留量检测方法。     

固相萃取-高效液相色谱法同时测定糕点中13种添加剂的研究

建立一种能够同时检测糕点中13种添加剂(7种人工合成色素、5种防腐剂与1种甜味剂)的高效液相色谱方法。方法:采用106g/L亚铁氰化钾和219g/L乙酸锌作为蛋白沉淀剂,经固相萃取小柱WAX富集、净化,Agilent 5HC-C_(18)(2)(4.6×250mm,5μm)色谱柱分离,0.02mol/L乙酸铵和甲醇为流动相,梯度洗脱,保留时间定性,峰面积定量,光谱确认进行检测。结果:13种添加剂在0.5～25μg/mL浓度范围内线性关系良好,相关系数r为0.9991～0.9999,检出限为0.01mg/kg～0.15mg/kg,样品加标平均回收率82.1%～105.4%,相对标准偏差小于5%(n=9),试验表明该方法定量准确,精密度高,方法重现性好,适用于各种糕点中多种添加剂的同时检测。     

酿造酱油挥发性风味成分测定方法的建立与组成比较

为建立一种测定酿造酱油中挥发性风味成分的顶空固相微萃取-气相色谱-质谱方法(HS-SPME-GC-MS),以3-辛醇作为内标,应用HS-SPME-GC-MS技术,对酱油中的香气成分进行快速、准确的定量分析.优化的SPME条件是:75μm CAR/PDMS萃取头、萃取温度50℃、萃取时间40min、NaCl质量浓度220g/L,回收率在81.3%～105.9%之间.使用该方法,从低盐固态酱油中鉴定出挥发性风味成分36种,总含量均值为3022.9μg/L;从高盐稀态酱油中鉴定出挥发性风味成分64种,总含量均值为3 749.1μg/L.两种酱油在酸类、醛类、酯类、呋喃酮类物质的含量上有显著的差异.     

高效阴离子交换色谱法测定婴幼儿配方奶粉中酵母β-葡聚糖

建立一种测定婴幼儿配方奶粉中酵母β-葡聚糖的分析方法。奶粉样品经蛋白酶酶解去除蛋白质,脂肪酶酶解去除脂肪,葡聚糖酶酶解β-葡聚糖产生葡萄糖,经高效阴离子交换色谱-脉冲安培检测,计算β-葡聚糖含量。结果表明,最优酶解条件为：酶解温度50 ℃、酶解时间2.0 h、溶壁酶添加量500 μL。采用PA10阴离子交换柱进行分离葡萄糖,葡萄糖在0.10～50.0 mg/L范围内线性良好（R2＞0.999 5）,添加水平在10.0～50.0 mg/100 g范围的回收率为96.9%～102.1%,精密度试验结果相对标准偏差为2.43%（n=5）,方法检出限为3.0 mg/100 g,定量限为10.0 mg/100 g。该方法灵敏、准确,可用于婴幼儿配方奶粉中酵母β-葡聚糖的测定。     

气相色谱-串联质谱法（GC/MS/MS）测定酱油中氨基甲酸乙酯的含量

建立了气相色谱-串联质谱法测定酱油中氨基甲酸乙酯的方法,酱油样品在层析柱中用乙醇：二氯甲烷（1：9）洗脱,采用DB-225MS毛细管柱分离样品,GC/MS/MS检测氨基甲酸乙酯的含量,方法线性范围为5-500μg/L,方法检出限和定量限分别为5和10μg/kg,标准加入20-500μg/kg的平均回收率为88.00%-93.58%,本方法具有操作简便、快速、准确等优点,适用于酱油中的氨基甲酸乙酯检测。     

化学原子化-原子吸收光谱法直接测定酱油中砷含量的方法研究

建立一种化学原子化-原子吸收光谱法快速测定砷的方法。样品仅通过加酸定容处理后,通过对介质酸度、硼氢化钠浓度、氢氧化钠浓度、载气流速等条件的优化,直接测定酱油中的砷含量。在选定的条件下,该方法的检出限(3σ)为0.10μg/L,在0~10μg/L内线性良好,回归方程为Y=0.05667X+0.00303,回收率为97.7%~100.5%,相对标准偏差(n=7)为0.21%~1.02%。该方法简便、高灵敏度、高精密度、无背景校正,能够很好地检测酱油中总砷。     

固相萃取-气相色谱-质谱联用法测定酱油中脱氧雪腐镰刀菌烯醇

建立了固相萃取-气相色谱-质谱(SPE-GC-MS)检测酱油中脱氧雪腐镰刀菌烯醇的方法。酱油样品采用乙腈-水(84∶16)提取,提取液经石油醚脱脂后过C18小柱净化,滤液吹干后经三甲基硅咪唑(1-Trimethylsilylim-idazole,TMSI)-三甲基氯硅烷(Chlorotrimethylsilane,TMCS)(10∶1)衍生5 min,最终GC-MS进行定性和定量分析。此方法对DON的线性范围为0.025～8.0μg/mL,相关系数(R2)为0.999 5,定量限(S/N=10)和检出限(S/N=3)分别为16.67 ng/mL和5 ng/mL。在添加水平为0.05、1.00和8.00μg/mL时,实际样品的平均回收率在82%～106%之间,相对标准偏差为5%～8%。此方法具有提取效率高,净化效果好,灵敏度高等优点,适用于酱油中DON的检测。采用此方法对市售的19种酱油进行检测,DON含量范围在0.04～1.24μg/mL间。     

高效液相色谱法测定酱油中的5-羟甲基糠醛

采用高效液相色谱法测定酱油中5-羟甲基糠醛(5-HMF)的含量.样品经乙酸乙酯提取后,用C18色谱柱分离,以甲醇-水(体积比为5:95)为流动相,在UV 284 nm波长条件下进行检测.该方法快速、准确,在0.5～20 mg/L范围内线性相关系数为r2=0.9992,平均回收率为82.4%～ 86.9%,相对标准偏差为3.2%～5.1%.方法的最低检测浓度为0.1 mg/L.     

盐酸精氨酸葡萄糖注射液中葡萄糖含量的测定

目的建立测定盐酸精氨酸葡萄糖注射液中葡萄糖含量的方法。方法选择适宜的pH值,然后通过考察该pH值下溶液旋光度与盐酸精氨酸和葡萄糖浓度的线性关系并测定盐酸精氨酸的比旋度,建立旋光法测定葡萄糖含量的计算公式。结果测定pH值为4.2。在此pH值下,盐酸精氨酸和葡萄糖混合溶液的旋光度与盐酸精氨酸浓度和葡萄糖浓度的复相关系数为0.9999,线性范围分别为2.3～3.0g/100ml和1.8～3.2g/100ml;测得盐酸精氨酸的比旋度为11.54。结论盐酸精氨酸和葡萄糖的旋光度具有加和性,从测得的旋光度中扣除盐酸精氨酸的旋光度,即是葡萄糖的旋光度,葡萄糖的含量可按公式c=2.0852(α-0.1154c1)计算。     

Electrochemical determination of glucose using polyaniline electrode modified by glucose oxidase

Polyaniline (PANI) enzyme electrode was formed by immobilisation of Glucose oxidase (GOx) via glutaraldehyde into electrochemically polymerised PANI on graphite electrode. Electrochemical polymerisation of PANI on graphite was performed from aqueous solution of 1.0 mol dm⁻³ HCl and 0.25 mol dm⁻³ aniline at constant current density of 2.0 mA cm⁻². Hronopotentiometric curves of the PANI enzyme electrode obtained at current density of 10 μA cm⁻² were recorded in different glucose concentrations. The linearity response range was between 1.0 and 5.0 mmol dm⁻³ of glucose concentration. The estimated apparent Michaelis–Menten constant, was K_m^′ = 0.30 mmol dm⁻³, which is significantly lower than that of free enzyme.     

Catalytic efficiency of immobilized glucose isomerase in isomerization of glucose to fructose

Glucose isomerase (GI) from Streptomycesrubiginosus was immobilized covalently onto Eupergit C 250 L made by copolymerization of N,N-methylene-bis-methacrylamide, glycidyl methacrylate, allyl glycidyl ether and methacrylamide. The catalytic efficiency of immobilized GI in isomerization of glucose to fructose was found as three fold higher than that of free GI. The residual activity of immobilized GI after 18 reuses in a batch type stirred reactor was about 85% of its initial activity. The thermal stability of immobilized GI was almost same with that of the free GI at 60 °C for 18 h preincubation time. The residual activities of immobilized GI when stored at 5 °C and 25 °C for four weeks were 72% and 69% of the initial activity, respectively. However, free GI retained 88% and 78% of its initial activity at 5 °C and 25 °C upon four weeks storage, respectively. Thus, the use of Eupergit C 250 L immobilized GI instead of free GI is suggested in enzymatic isomerization of glucose to fructose.     

葡萄糖/葡萄糖氧化酶抗菌纸及抗菌性研究

葡萄糖氧化酶是氧化葡萄糖的专一催化酶,具有脱氧、杀菌的功能。通过定性和定量抗菌实验方法研究了葡萄糖/葡萄糖氧化酶体系在以淀粉作为载体和不混合淀粉时施涂于纸张表面的抗菌效果。定性抗菌实验表明,葡萄糖/葡萄糖氧化酶抗菌纸具有良好的抗菌效果。而定量检测结果表明,pH等于5.5时,35℃反应10min,不添加淀粉时,葡萄糖氧化酶最小的抑菌浓度约为70U/m2,葡萄糖足量时,酶用量越高,抗菌率越好;添加0.7g/m2淀粉后,最小抑菌浓度提高到约650U/m2。淀粉对葡萄糖/葡萄糖氧化酶体系的抗菌效果有较大影响,主要原因是淀粉能够促进细菌的繁殖。     

酶法制取葡萄糖的工艺研究

随着现代精细工业的发展,葡萄糖作为基料的社会用量日益增大,用途日趋广泛,制取葡萄糖的工艺研究也成为国内外不间断的课题。本文采用酶法水解与目前先进的过滤、离子交换及蒸发浓缩等下游工程技术结合,研究葡萄糖加工的工艺条件与提高产品纯度和得率的实用技术。通过实验确定最佳工艺条件为：液化时,pH6．0～6．5,温度85℃,时间40min,α-淀粉酶用量0．3％,淀粉浆浓度30％；糖化时,pH4．2～4．5,温度60℃,时间48h,糖化酶用量0．6％。     

Optimising glucose conversion in the production of reduced alcohol wine using glucose oxidase

The use of a glucose oxidase (GOX)-catalase enzyme system for the production of reduced-alcohol white wine is investigated. The process reduces alcohol potential by converting glucose to gluconic acid. Trials were conducted with grape juice and model solution to determine key factors affecting the activity of the GOX system, and to optimise the process for use with grape juice. Under our processing conditions, the low pH of grape juice was found to be a dominant limiting factor in the rate and extent of glucose conversion by GOX. An optimised process for glucose conversion (up to 87%) was developed after investigation of the effects of enzyme dosage, sparging, aeration and mixing rates, and temperature. Maximum GOX activity was observed during the first 4 to 6 h of treatment, after which a significant decrease in the rate of gluconic acid formation and glucose degradation occurred. An expected increase in titratable acidity and concurrent decrease in pH during GOX treatment was also observed, and is attributable to an increase in the juice gluconic acid concentration of ca 73 g/l.     

Duodenal glucose increases glucose fluxes and lactose synthesis in grass silage-fed dairy cows

The effect of intestinal glucose supply on whole body rate of glucose appearance (WBGRa) and mammary utilization of glucose was studied in four lactating dairy cows. Glucose (0, 443, 963 and 2398 g/d) was continuously infused in the duodenum over 14-d periods using a Latin square design. A grass silage-based diet was formulated so that treatments were isoenergetic and isonitrogenous and contained 100 and 110% of energy and protein requirements according to INRA (1989). The WBGRa was measured by the [6,6-(2)H2]glucose dilution technique, and mammary glucose balance by arteriovenous differences and blood flow measurements. Duodenal glucose infusion increased arterial glucose concentrations linearly, whereas arterial concentrations of insulin, growth hormone, and glucagon were not changed. The WBGRa increased linearly with increasing glucose loads. The increase represented 42% of the intestinal glucose supplement. Mammary blood flow dramatically increased (up to 45%) and was associated with a significant increase of arterial insulin-like growth factor-1 concentrations. Mammary gland rate of glucose disappearance ([6,6-(2)H2]glucose measurement) increased linearly, whereas net mammary balance of glucose, lactose, and milk yields increased quadratically. Net mammary balance of glucose accounted for 60% of WBGRa, except for the greatest dose (47.6%). The decrease in milk yield with 2398 g/d of glucose may be explained by an imbalance in intracellular intermediate concentrations. The milk ratio of glucose-1-phosphate to glucose-6-phosphate decreased significantly at the greatest infusion of glucose. In conclusion, exogenous glucose supply to a grass silage-based diet increased WBGRa, mammary utilization of glucose and milk synthesis.     

Conversion of glucose in lactase-hydrolyzed whey permeate to fructose with immobilized glucose isomerase

The maximum conversion of glucose to fructose in lactase-hydrolyzed whey permeate by glucose isomerase was approximately 52% at .1 g enzyme/ml substrate after 7 h incubation at 60 degrees C. Removal of minerals from the substrate was essential for enzyme activity. The dependence of the enzyme on Mg++ and Co++ for activity in the presence of high ash concentration was demonstrated. Optimum Mg++ and Co++ additions were 250 and 100 ppm, respectively. The isomerization reaction was enhanced more when both 100 ppm Mg++ and 50 ppm Co++ were added. Hydrolyzed isomerized lactose whey syrup with sweetness equivalent to sucrose was successfully produced through enzymatic isomerization of glucose in lactase-hydrolyzed whey permeate after supplementation with pure glucose. Fructose in hydrolyzed isomerized lactose whey syrup was effectively separated from other sugars by Dowex 1X8-200 anion exchange resin in the bisulfite form.     

Evaluation of glucose dose on intravenous glucose tolerance test traits in Holstein-Friesian heifers

Glucose metabolism in dairy and beef cattle has received considerable attention because balanced blood glucose is essential for numerous processes, such as milk production and general health. The glucose tolerance test measures the ability of an organism to regulate blood glucose levels. Glucose half-life time (GHLT) has high heritability and could serve as a potential parameter to breed for metabolic resistance. However, studies focusing on identification of an adequate glucose dose have not yet been conducted in cattle. The objective of this study was to analyze the effect of 5 different glucose doses (0.5, 1, 1.5, 2, and 3 g/kg of body weight^0.75) on intravenous glucose tolerance test (ivGTT) traits and insulin responses in nongestating heifers. A total of 150 tests were performed in 30 Holstein-Friesian heifers aged 13 to 15 mo. Blood samples were obtained every 7 min after glucose injection until min 63. Glucose traits and insulin parameters included blood serum glucose and insulin concentration at min 0 (basal concentration), min 7 to 21 (peak glucose and insulin concentration), and min 63 (last sampling) relative to glucose administration, glucose and insulin area under the curve (GAUC and IAUC), and GHLT estimated between min 14 and 42. Serum glucose and insulin concentrations were measured according to the hexokinase colorimetric method and radioimmunoassay, respectively. Generalized linear mixed model was used to test for significant differences in ivGTT traits, insulin responses, and glucose elimination rates (k) over time at different glucose doses. Maximum glucose and insulin concentrations at min 63 increased with higher glucose doses. Significantly lower GHLT were obtained at increasing glucose doses, whereas GAUC and IAUC were significantly higher at increasing doses. The k values were affected by glucose dose and by time interval. Glucose dose greatly affected most ivGTT traits, insulin responses, and glucose elimination rates. Therefore, researchers should standardize their methods to achieve repeatable results and use the same time points for GHLT calculation. Higher glucose doses (≥1.5 g/kg of body weight^0.75) triggered glucose concentrations above the glucose renal threshold during the initial 42 min, whereas the lowest glucose concentration failed to induce a maximum insulin response. Further research is necessary to determine an adequate dose inducing maximum insulin responses with minimum renal glucose losses.     

Effect of multivalent cations on the enzymatic determination of glucose with glucose oxidase]

Iron and copper ions, in a concentration greater than 10(-4) M, inhibit the indicator reaction of a glucose oxidase-peroxidase reagent for the enzymatic determination of glucose, when weakly complexing buffers or buffer-free reaction media are used. The addition of EDTA and other complexing agents or, time-dependently, the buffer ions themselves reverse the inhibition to a great extent. The discussed mechanism of inhibition is based on the assumption that the metal ions share in the re-oxidation of the co-enzyme of glucose oxidase.