土霉素—邻菲啰啉快速测定饲料及粮食中微量铁(Ⅲ)的研究和应用

本文提出了在pH3～4.5,以土霉素-1,10邻菲啰啉为显色剂,分光光度法快速测定微量铁的新方法。其最大吸收波长510nm,摩尔吸光系数1.35×10~4L·mol~(-1)·cm~(-1),线性范围0.20μg/ml～10μg/ml,显色速度快,大量常见离子无干扰。可直接用于饲料和粮食中铁的测定。     

NPBPT-CPB体系分光光度法测定小麦粉中的痕量锌

研究了测定痕量锌的新方法.利用NPBPT-CPB体系通过湿法消解对食用小麦粉的痕量锌进行分光光度测定.结果表明,摩尔吸光系数为1.89×105L·(mol·cm)-1;最大吸收波长为520 nm;锌含量为0～400μg/L时符合比尔定律.用本方法和国家标准法中的原子吸收法测定食用小麦粉样品中锌的含量进行比较,结果令人满意.     

Fe(Ⅱ)—BPT—Tween—20体系测定食品中的微量铁

<正> 本文提出了一种测定食品中微量铁的新方法,Fe(Ⅱ)-BPT-Tween-20络合物的最大吸收波长为538nm,摩尔吸光系数为2.2×10~4L·mol~(-1)·cm~(-1)。方法简便、快速,具有良好的选择性,结果精确可靠。 食品中的铁含量很低,常见的测定方法有磺基水杨酸法、硫氰酸盐法和邻菲啰啉     

铁-邻二氮杂菲间接分光光度法检测皮革甲醛含量

建立了一种用铁-邻二氮杂菲间接分光光度法检测皮革甲醛含量的方法。该法是基于在碱性条件下,甲醛与水合氧化银发生氧化还原反应,生成的银定量还原铁(Ⅲ)为铁(Ⅱ),铁(Ⅱ)与邻二氮杂菲形成稳定的桔红色络合物。此络合物的ε510为1.1×104L·mol-1·cm-1,方法用于皮革样品中游离甲醛的测定,取得了满意的结果。     

紫外分光光度法测定猕猴桃中Vc含量

应用紫外分光光度法间接测定猕猴桃中Vc含量,最大吸收波长290nm,Vc浓度在0～200mg·L-1范围内符合朗伯—比尔定律。回归方程为A=11.70C-69.59,线性相关系数γ=0.9993,表观摩尔吸光系数ε=1.79×104L·mol-1·cm-1。精密度高,回收率96%～102%。     

滤膜溶解分光光度法测定粮食中微量锰

锰(Ⅱ)与二溴羟基苯基荧光酮(DBHPF)和溴化十六烷基三甲铵(CTMAB)形成的配合物,通过微孔滤膜富集,用二甲亚砜将滤膜及配合物溶解,在分光光度计上测定吸光度的一种快速富集测定微量锰的方法。配合物最大吸收波长为592nm,表观摩尔吸光系数ε592=4.70×105L·mol-1·cm-1,锰含量在0～12μg/5ml范围符合比尔定律,用于粮食中锰的测定,结果满意。     

原子吸收分光光度计测定葡萄酒中铁含量的两种方法比较

比较了利用原子吸收分光光度计测定葡萄酒中铁元素含量的两种方法——标准浓度法与标准加入法，测定结果的相对标准偏差(n=6)：标准浓度法为2．8％，标准加入法为2．1％；回收率范围分别为119．93％～146.30％和101.33％～103.30％；线性范围均为0～12mg／L。确定了更为准确、稳定、快速的标准加入法作为原子吸收分光光度计分析葡萄酒中的铁元素含量的最佳方法，并可将该方法推广到其他元素的测量中使用。     

消除铁对铬天青S分光光度法测定铝的干扰研究

为消除铬天青S分光光度法测定臭豆腐中铝时铁带来的干扰,采用氢氧化钠溶液对铁和铝进行分离,并对方法进行优化。结果表明：不对臭豆腐消解液进行处理,采用铬天青S分光光度法测定其铝含量,当溶液铝含量一定时,溶液中铁含量越高,测得的结果越比真实值偏高,当溶液铁含量较高且一定,铝含量越高,测得的结果越接近真实值。采用优化后的方法对含有大量铁的臭豆腐消解液进行处理后,用铬天青S分光光度法测定其铝,测定结果与电感耦合等离子体质谱法测定的结果都没有显著性差异（P>0.05）;而铬天青S分光光度法测定未处理消解液的铝,其结果都显著高于（P<0.05）电感耦合等离子体质谱法测定的结果。因此,通过本方法对含有大量铁的臭豆腐消解进行处理后,采用铬天青S分光光度法能够准确测定样品中铝。     

流动注射分光光度法测定制革废水中的甲醛

研究了流动注射变色酸分光光度法自动测定制革废水中的甲醛,基于在酸性介质中变色酸和甲醛在加热条件下的显色反应,该络合物最大吸收波长在390nm。优化了影响反应的化学因素和流动注射系统分析条件。该方法的检测限和线性范围分别为0·01μg/L(按照3倍基线噪音计算)、0·02～5mg/L,对含量100mg/L和100μg/L甲醛标准溶液进行了11次平行测定,其相对标准偏差分别为0·30%和0·42%(n=11)。应用于制革废水中的甲醛的测定,回收率在95·2%～97·7%,结果令人满意。     

快检法和仲裁法测定稻谷镉含量的比较

通过X射线荧光光谱仪测定稻谷镉含量,与原子吸收分光光度计法测定结果进行比较,对其进行t检验的结果表明两种方法测定结果不存在显著性差异;随着样品镉含量的增高,X射线荧光光谱仪法的准确性和稳定性也增强;如果样品镉含量大于0.17 mg/kg以上,X射线荧光光谱仪法测量结果可以与传统的原子吸收光谱法相媲美。     

强化面粉和食盐中乙二胺四乙酸铁钠检测的分光光度方法研究

在碱性介质中,NaFeEDTA(乙二胺四乙酸铁钠)与H2O2可形成稳定的紫红色络合物。在该显色体系中,NaFeEDTA浓度在(0.4～2)×10-3mol/L范围内符合朗伯-比尔定律,显色产物在515nm下的表观摩尔吸光系数为0.51×103L/(mol.cm)。应用该方法对强化面粉和食盐中的NaFeEDTA检测的平均回收率>94%。该方法具有简单、快速、选择性强的特点,可以用于强化面粉和食盐中的NaFeEDTA的鉴别和检测。     

Dispersibility of cereal proteins in urea solutions

Protein estimations by the biuret method were highly correlated with Kjeldahl determinations for 87 samples of the seven major cereal grains. The extent of binding of acid orange 12 in a phosphate buffer at pH 1·7 was correlated with the protein content but was affected by non-specific binding which varied with the tested cereals. Extraction with 3M-urea at 4° yielded an average of 67·9% protein from wheat, 67·3% from wheat flour, 66·2% from rye, 71·2% from oats, 46·7% from barley, 32·1% from rice, 22·3% from corn, and 24·6% from sorghum. Differences in dispersible proteins seem to be affected by the disaggregating and hydrogen-bond-disrupting effect of urea, and seem to be related to amino-acid composition and functional properties of cereal proteins. The urea-dispersible protein fraction in wheat flour was higher than in whole wheat.     

Microwave radiation for control of Tribolium confusum in wheat and flour

The susceptibility of Tribolium confusum Jacquelin du Val to microwave energy was determined by irradiating vials of infested wheat or flour near the aperture of an optimum gain horn coupled through a waveguide to a magnetron operating at 8·5 GHz and 30 W average output at a pulse repetition frequency of 4000 Hz. Mortality was a function of exposure time and wheat moisture content. Adult mortality was higher in insulated samples of wheat than in non-insulated samples. Susceptivility of stages to radiation at 60°C was: eggs > pupae > adults > larvae. Survival of pupae near the surface of wheat indicated that heat was distributed non-uniformly. Mortality was higher in wheat than in white flour. Adults from 1·5 to 7 months old were equally susceptible to radiation.     

Effect of flour extraction rate and baking process on vitamin B1 and B2 contents and antioxidant activity of ginger-based products

The effect of flour extraction rate and baking on thiamine (vitamin B₁) and riboflavin (vitamin B₂) content and antioxidant capacity of traditional ginger cake was studied and then compared to white wheat bread. Ginger cake was formulated either with whole-grain (100% extraction rate) or with brown (92% extraction rate) rye flour and baked at 180 °C for 18 min. The antioxidant capacity was evaluated in terms of radical scavenging activity against peroxyl (ROO·) and superoxide anion radicals (O ₂ ^·? ). Thiamine content in rye doughs (F-100% and F-92%) was found to be 38% lower when compared to wheat dough. In contrast, whole-grain and brown rye doughs exhibited an almost fourfold higher riboflavin content than wheat dough. Rye dough baking led to reductions in thiamine (from 53 to 65%) and riboflavin (from 69 to 71%) contents. Likewise, thiamine and riboflavin contents in wheat dough were also reduced (56 and 10%, respectively) after baking; however, ginger cake with whole-grain rye flour exhibited significantly higher thiamine and riboflavin contents. Rye doughs and ginger cakes showed higher scavenging activities against ROO· radicals when compared to that of wheat dough and bread. Thus, baking significantly enhanced ROO· scavenging properties of ginger cakes while only a slight increase was observed in wheat bread. In contrary, baking gave rise to a decrease in SOD-like activity both in ginger cake or wheat bread. Our findings suggest that formulation with whole-grain rye flour can potentially increase B₁ and B₂ vitamin contents as well as the ROO· scavenging capacity of traditional ginger cake.     

藜麦全谷物粉对馕抗氧化性影响的研究

目的 为提高馕的抗氧化物质的含量和提高其抗氧化特性, 方法 通过添加不同量的杂粮谷物粉以增加馕的抗氧化物质的含量和提高其抗氧化特性,在单因素实验的基础,利用Box-Behnken试验优化馕的口感得分制备条件。结果 馕的最优工艺为藜麦全谷物粉添加10.34%、高粱粉添加11.41%、小米粉添加9.97%、酵母使用量为0.96%、水分加入量为51.81%、发酵时间为85.94 min, 在此条件下制备的复合谷物粉馕的感官评价平均得分为80.43, 黄酮含量为1.2 mg/g、多酚含量为61.26 mg/g, 分别比纯小麦粉馕的感官得分、黄酮和多酚含量提高了3.4%、9.1%和16.46%; DPPH●自由基清除率平均值为58.83%, ABTS●+自由基清除率平均值为51.58%, 还原力平均值为10.67 mg/g, 分别比纯小麦粉馕的DPPH●、ABTS●+自由基清除率和还原力提高了22.05%、15.39%和10%。结论 以藜麦全谷物粉、高粱粉和小米粉混粉制备馕, 可以显著提高其黄酮含量、多酚含量及其抗氧化性能。     

Comparison of enhancement in bioaccessible iron and zinc in native and fortified high‐phytate oilseed and cereal composites by activating endogenous phytase

In developing countries, iron and zinc deficiencies are mostly attributable to poor bioavailability of iron and zinc. The study aimed at enhancing the bioaccessibility of minerals in high‐phytate oilseed and cereal flour mixes by activating the intrinsic phytase of wheat flour. The flour mixes were fortified with iron and zinc separately for comparison. The flour mixes were incubated at optimum conditions of temperature and pH for phytase activation. Phytase activation enhanced bioaccessible iron by 43–162% in native and 40–168% in fortified wheat–soya, 83–192% in native and 97–240% in fortified wheat–groundnut flour mixes in relation to control flour mixes. Bioaccessible zinc was enhanced by 87–183% in native and 30–113% in fortified wheat–soya, 31–65% in native and 61–186% in fortified wheat–groundnut flour mixes. Endogenous phytase activation was effective in enhancing bioaccessibility of iron and zinc in native and fortified flour composites economically.     

Production of iron-fortified bread employing some selected natural iron sources

Iron fortification of wheat breads is the optimal approach for reducing the high prevalence of iron deficiency in wheat-eating developing countries as in Egypt. The effectiveness of some natural iron-fortificants for potential use in Egyptian bread was tested. Defatted soybean flour, soybean flour, soybean hull flour, molasses and fenugreek flour at different levels besides FeSO₄ · 7H₂O as standard were separately incorporated in the wheat flour dough. Dough characteristics were studied using a Brabender Farinograph, where addition of such fortificants improves significantly (p < 0.05) the water absorption, development time, dough stability and dough weakening. Good breads with high nutritive value, excellent crust color, crumb grain and high overall acceptability were produced by adding either 10% defatted soybean flour, 5% soybean hull flour, 2% molasses or 4% fenugreek flour. Rat feeding trials have shown a good haematological response, i.e. higher haemoglobin (Hb) and haematocrit (Hct) values gained. Additional work is needed to identify other fortification options and to develop targeted fortification programes that will supply iron to all segments of a population in greatest need.     

Effects of ingredients on the characteristics of rice cakes

Steamed leavened rice cakes made from rice flour, sugar, water, yeast or baking powder were used to study the effects of ingredients on cereal-based cakes. Volume expansion linearly correlates to amylopectin and negatively correlates to amylose content (r²=0·84), with an optimum amylose/amylopectin ratio of approximately 1: 8. Higher amylopectin content resulted in sticky, elastic and unacceptable cake. The optimum water content for volume expansion was in the range of 90±5% by weight of rice flour. Sugar content correlates linearly with volume expansion and tenderness of chemically leavened rice cakes (CLRC) (r²=0·99 and 0·92, respectively). Sugar content above 50% of rice flour weight decreased volume and softness of yeast-leavened rice cakes (YLRC). Tenderness of YLRC correlates linearly to fat content (r²=0·98), but volume expansions correlates negatively to the square root of fat content (r²=0·81 and 0·97 for the two rice cakes). Both tenderness (r²>0·92) and volume expansion (r²>0·93) correlates linearly with emulsifier content up to 3% by weight of rice flour, above which the cake becomes crumbly. A little salt increased hardness, but further increase reduced both volume expansion and hardness of rice cakes. Skimmed milk powder greatly increased the expansion of CLRC. Ovalbumin content correlates linearly to volume expansion of YLRC (r²=0·87) but negatively to the expansion of CLRC (r²=0·96). The proteins that improved the textures of rice cakes were skimmed milk and egg white with an optimum content of 2–4%. Egg yolk, soya protein, whey powder and wheat gluten reduced both tenderness and volume expansion. The effects of the various ingredients interacting together were studied and the optimum formulations was determined using a Random Centroid Optimisation Program. © 1998 SCI.     

Whole wheat and white wheat flour— the mycobiota and potential mycotoxins

Mold growth has detrimental effects on the quality of flour and may result in mycotoxin contamination. The search for potential mycotoxins—almost 400 are known—is time-consuming and expensive. However, detailed knowledge about the mycobiota and especially the toxin producing fungi enables the effective search for these toxic fungal metabolites. Therefore, a whole wheat flour and a white wheat flour (type 405) were investigated for their total qualitative as well as quantitative mycobiota. Overall, 51 species belonging to 14 different genera could be isolated. Total fungal counts of the whole wheat flour amounted to 1833 molds while the white wheat flour contained 1730 cfu 2 g⁻¹. The mycobiota of both flours was dominated by Aspergillus spp. accounting for 84% and 77·3% of the isolations, respectively. Fungi of the genus Penicillium spp. occurred only to a minor degree: 8% of the isolations in whole wheat flour and 15% in white wheat flour. Aspergillus candidus was the most frequently encountered mold.Penicillium aurantiogriseum , Cladosporium cladosporioides, A. flavus, Eurotium herbariorum,P. griseofulvum , P. brevicompactum and P. viridicatum were isolated to a lesser degree. From the 3563 identified fungi 93·3% (32 species) belong to the group of toxigenic molds.     

Determination of benzoyl peroxide, as benzoic acid, in wheat flour by capillary electrophoresis compared with HPLC

BACKGROUND: In recent years, debate on the addition of benzoyl peroxide (BP) to wheat flour has increased in China. Medical studies have so far not confirmed that BP in wheat flour causes definite damage to the human body, but its main metabolite in the human body is benzoic acid. The addition of BP to wheat flour has been forbidden in China since 1 May 2011. It is therefore necessary to develop a suitable method to determine BP in wheat flour. RESULTS: A simple method using capillary electrophoresis (CE) was developed for determination of BP in wheat flour. BP was determined as benzoic acid after preceding reduction by potassium iodide. Separation was completed in less than 7 min with a running buffer of 10 mmol L^?1 sodium borate (pH 9.18), 4 s hydrodynamic injection, 25 kV separation voltage and UV detection at 228 nm. The method was validated in terms of linearity, sensitivity, detection limit, precision and accuracy. The detection limit was 0.29 µg mL^?1. The method was successfully applied to the determination of BP in wheat flour samples, with recoveries between 96.1% and 102.6%. CONCLUSION: The performance of the CE method was comparable, and the quantitative results were in good agreement with those using high‐performance liquid chromatography (HPLC). Meanwhile the proposed CE method has the advantages of better resolution, shorter analysis time and lower cost, and would be a good alternative to HPLC for routine monitoring of BP amount in wheat flour. Copyright © 2011 Society of Chemical Industry