牛肉嫩化机制的初步研究

对牛肉分别注射300mmol／LCaCl2溶液、EDTA溶液、ZnCl2溶液（注射量为肉重的5％），然后将处理样品在4℃下分别腌制24h、48h，通过对其剪切力值、MFI的测定，初步研究牛肉嫩化的机制。结果表明，注射CaCl2能促进肌原纤维的分解，进而加速肉的嫩化；而注射EDTA和ZnCl2却抑制肌原纤维的分解，阻止肉的嫩化。牛肉的嫩化是Ca^2＋通过促进肌原纤维的分解而实现的。     

反相离子对高效液相色谱法测定果味饮料中的乙二胺四乙酸二钠

建立反相离子对HPLC测定水基果味饮料中的食品添加剂乙二胺四乙酸二钠(Na_2EDTA)的方法,通过测定Na_2EDTA与Fe~(3+)反应生成稳定的螯合物FeEDTA~-的含量以及建立标准曲线,计算样品中Na_2EDTA的添加量。样品在加入三氯化铁溶液后,以Zorbax C 8色谱柱进行分离,以含12.5%甲醇、0.13%四丁基氢氧化铵(TBAOH)和0.052%甲酸水溶液(pH 3.50)作为流动相,流速1.0 ml/min,检测波长254 nm。在5～50 μg/ml范围内峰面积与浓度呈良好的线性关系(r=0.9999),其加标回收率100.5%～103.6%,样品溶液6次重复测定的相对标准偏差为0.6%。本方法简单、快速,检测结果稳定,重现性好,可用于果味饮料中所添加的食品添加剂Na_2EDTA的测定。     

荧光试纸技术可视化定量检测食品中的乙二胺四乙酸

目的 建立荧光试纸技术对食品中乙二胺四乙酸(editic acid, EDTA)进行可视化定量检测的方法。方法 以豌豆荚为原料，采用水热法合成蓝色荧光碳量子点（carbon quantum dots, CQDs），利用透射电镜（transmission electron microscope, TEM）、X射线衍射仪（X-ray diffractomer, XRD）、X射线光电子能谱仪（X-ray photoelectron spectroscopy, XPS）和傅里叶变换红外光谱仪（fourier transform infrared spectrometer, FTIR）对制备的CQDs的形貌及表面结构进行表征；向豌豆荚碳量子点溶液中加入铜离子（Cu2+），使蓝色荧光淬灭，将CQDs-Cu2+溶液吸附于滤纸上，制得EDTA荧光检测试纸。结果 EDTA能使CQDs-Cu2+体系淬灭的荧光恢复，在20~120 μmol/L范围内与CQDs-Cu2+荧光恢复强度呈现较好的线性关系，检出限为6.29 μmol/L，回收率为98.73%~99.40%。结论 该试纸可用于定量检测食品中EDTA的含量，为EDTA的检测提供更加简便、直观的方法。     

EDTA-CaNa_2对发芽糙米γ-氨基丁酸(GABA)及矿质元素(Ca、Zn、Cd、Pb)影响

该文报道研究一种既提高发芽糙米GABA富集量又减少重金属含量新方法。在糙米发芽前,采用EDTA–CaNa2溶液浸泡,当EDTA–CaNa2浓度为80μg/mL(Ca2+浓度约0.2 mmol/L)、浸泡时间为10.5 h时,可使发芽糙米GABA富集量提高42.4%,达到63.36 mg/100g;同时,EDTA–CaNa2溶液浸泡可促进糙米中镉、铅元素迁移溶出。所以,EDTA–CaNa2溶液浸泡不仅提高发芽糙米GABA富集量,且提高发芽糙米产品安全性,为发芽糙米产品加工提供新思路。     

以Ba~(2+)作指示电极滴定废水中的SOi_4~(2-)

在含30％乙醇、pH=3.5的溶液中,用四甘酰双[二(对辛基苯)胺]钡离子选择电极作指示电极,氯化钡为滴定剂,直接滴定皮革厂废水中硫酸根,Ca~(2+)的干扰可用EDTA溶液消除,方法快速,变异系数(u=8)<1％。     

纸上荧光数码成像法快速测定花生壳中的木犀草素含量

本文利用木犀草素在乙二胺四乙酸二钠(EDTA)协同配合下可增强铽离子(Tb~(3+))荧光强度的特征,建立了一种快速测定木犀草素含量的纸上荧光数码成像法。将木犀草素溶液及EDTA、Tb~(3+)、Na OH等检测试剂点样于纸芯片的检测区,用智能手机在紫外灯下采集并读取荧光图片的红(R)、绿(G)、蓝(B)颜色数值,研究了该检测体系的显色条件、干扰物质、木犀草素浓度计算模型等。结果表明:优化后的显色条件为依次在纸芯片检测区加入0.4μL 1.0 mol/L NaOH溶液、1.0μL 1.0×10-2 mol/L EDTA溶液、6μL木犀草素标准溶液、0.75μL 1.5 mmol/L Tb~(3+)溶液,室温下反应5 min。在此条件下,木犀草素的浓度在0.05～4.0 mmol/L时与B/(R+G+B)成良好的线性关系,R2=0.9954;用该法测定花生壳中木犀草素含量时,回收率为96.5%～106.3%,相对标准偏差为3.9%。该法快速、简便、成本低廉,能用于复杂样品中木犀草素含量的现场测定。     

面粉中掺有石膏粉的快速检测方法

通过定量 Ca2 含量的方法 ,来鉴别面粉中是否掺有石膏粉。该法简便 ,快速、准确、可靠。为检测面粉的质量提供了一种较理想的手段     

一种快速准确测定羧甲基淀粉取代度的方法

传统的络合滴定法测定羧甲基淀粉取代度(DS)时,存在耗时长,稳定性差,高取代度羧甲基淀粉测定效果差等问题。本文采用将过量CuSO4溶液加入pH6.0～7.0的变性淀粉溶液中,生成羧甲基淀粉铜沉淀,过滤除去沉淀,再调节pH至7.5～8.0后,采用1-2-吡啶偶氮-2-萘酚(PAN)为指示剂,用EDTA标准溶液滴定过量的Cu2 的方法来测定羧甲基淀粉的DS。该法简便快速,准确可靠,稳定性好,可适用于羧甲基淀粉工业简便快速的检测。     

分析化验小常识

1.配制EDTA溶液时,有时溶液发生浑浊,是什么原因?应如何消除? 答:通常所称的EDTA,是乙二胺四乙酸的二钠盐,结构式如下:     

电位滴定法测定婴幼儿配方奶粉中Vc含量

介绍了电位滴定法测定婴幼儿配方奶粉中Vc含量的方法。在试样被偏磷酸等酸性浸提剂提取后的酸性溶液中,用EDTA掩蔽干扰离子后,直接用2,6-二氯靛酚溶液滴定试样中的维生素,并利用电位滴定仪的电位突跃指示滴定终点。探讨了金属螯合剂EDTA、滴定剂浓度及酸性浸提剂对测定结果的影响。对滴定法的线性关系、回收率及精密度进行了研究,结果表明:该方法具有较好的线性和精密度,回收率为95%~101.5%,测定结果的相对标准偏差小于1.0%。该方法具有测试简便、快速、干扰少及准确等特点。     

面制品及糕点中含铝食品添加剂的测定

以乙二胺四乙酸二钠溶液为提取剂,选择性提取面制品及糕点中含铝食品添加剂残留铝,提取液酸化后用ICP-MS测定,实现了面制品及糕点中添加剂残留铝的准确测定。考察了超纯水、氢氧化钾溶液、硝酸溶液(2%)、EDTA二钠溶液及草酸溶液对食品中添加剂残留铝的提取效果和选择性,研究了EDTA二钠提取剂浓度、提取时间、提取温度及振摇时间间隔对添加剂残留铝提取效率的影响。结果表明,最佳提取条件为EDTA二钠提取剂浓度300μg/mL、提取时间30min、提取温度90℃、振摇时间间隔10min。对海苔麻花及蛋糕分别进行50mg/kg、100mg/kg两种梯度加标,加标回收率为98.0%~100.5%,相对标准偏差为1.36%~2.58%,方法检出限为0.026mg/kg,定量限为0.087mg/kg。     

EFFECT OF PACKAGING MATERIALS ON THE QUALITY OF IRON-FORTIFIED WHOLEMEAL FLOUR DURING STORAGE

ABSTRACT

The effect of packaging materials on the physicochemical and rheological characteristics of iron‐fortified wholemeal flour (WMF) during storage was determined. WMF was fortified with three fortificants, namely ferrous sulfate (30 ppm), ferrous sulfate + ethylenediamine tetraacetic acid (EDTA) (20 + 20 ppm) and elemental iron (60 ppm). Each flour was also fortified with 1.5 ppm folic acid. Moisture, flour acidity and peroxide value increased during storage, while protein and fat contents decreased. Highest conversion of Fe²⁺ into Fe³⁺was observed in flour fortified with ferrous sulfate (2.72%), followed by that fortified with ferrous sulfate + EDTA (1.49%) and elemental iron (1.06%). Water absorption and dough viscosity of iron‐fortified flours increased during storage. The flour containing ferrous sulfate was most acceptable regarding sensory characteristics, followed by samples containing ferrous sulfate + EDTA. Fortified flours were more stable during storage than unfortified. Addition of EDTA increased the stability of flours and fortificants. The fortified flours stored in polypropylene bags proved more stable than those stored in the tin boxes.

PRACTICAL APPLICATIONS

The main role of packaging is to protect the product during handling, distribution and storage against environmental and mechanical hazards. The success of a fortification program depends on the stability of micronutrients and food to which these are added. Chemical changes during storage badly affect chapatti making and sensory properties. Exposure of the fortificant to any factor including heat, moisture, air or light, and acid or alkaline environments during processing, packaging, distribution, or storage affects its stability. Flour containing elemental iron and ferrous sulfate with EDTA remained stable up to 42 days. The unfortified flour and flour containing ferrous sulfate remained stable for 21 days in tin boxes and 28 days in the polypropylene bags. Wheat flour milling industry would be benefited from this research if government is keen to launch iron fortification program in the country to curb iron deficiency anemia among population.

     

Removal and recovery of antinutritional factors from soybean flour

An integrated process for removal purification of two antinutritional factors, namely soybean trypsin inhibitor and soybean agglutinin, from soybean flour has been developed. The process is based upon binding of soybean trypsin inhibitor and soybean agglutinin to an immobilized metal affinity chromatography medium, consisting of zinc alginate beads. Both soybean trypsin inhibitor (95%) and soybean agglutinin (94%) could be removed from an aqueous extract of soybean flour. The bound protease inhibitor and lectin could be recovered by washing the zinc alginate beads with 0.05 M imidazole solution and dissolving the beads in 0.01M EDTA, respectively. Recoveries of 89%, in the case of soybean trypsin inhibitor and 81% in case of soybean agglutinin, were possible. Both purified proteins gave single band on SDS–PAGE. Thus, soybean flour, free of these two antinutritional factors, could be obtained. Simultaneously, these two antinutritional factors were purified as value-added products.     

Determination of thiol groups and disulphide bonds in wheat flour and dough

A study was made of the conditions for determining all thiol (SH) groups and disulphide (S—S) bonds in wheat flour and dough. Thiol groups were determined by amperometric titration with Ag₂SO₄, the flour or dough which contains proteins and peptides being suspended in a solution of 6 m urea and 10^?4 M sodium dodecyl sulphate (SDS). The potential of the platinum electrode was ?0.24 V vs calomel reference electrode. Disulphide bonds were determined in two ways: (a) Using an excess of Ag₂SO₄ in the presence of 9 M urea; when the reaction was finished, the excess Ag₂SO₄ was removed by adding an exact quantity of glutathione. The glutathione which remained after binding the Ag₂SO₄ excess was determined by amperometric titration with a 5.10^?5 M Ag₂SO₄ solution, (b) Determination after reduction with NaBH₄; the disulphide bonds were reduced to thiol groups and the total amount of thiol groups was determined with Ag₂SO₄. The results indicated that wheat flour contains 5–7 μmol SH-groups, which is about six times the level found by previous workers, and 11-18 μmol disulphide bonds per gram flour. A correlation with baking quality was not observed.     

高效液相色谱法测定面粉中乙二胺四乙酸二钠的不确定度评定

目的评定高效液相色谱法测定面粉中乙二胺四乙酸二钠(ethylenediaminetetraacetic acid disodium,EDTA-2Na)含量的不确定度。方法采用高效液相色谱法测定面粉中乙二胺四乙酸二钠含量。通过建立数学模型,分析测量不确定度的来源,量化各个测量不确定度分量,合成不确定度。结果面粉中乙二胺四乙酸二钠含量测定的不确定度主要由乙二胺四乙酸二钠标准工作曲线拟合的不确定度所引起,通过分析各分量不确定度发现标准曲线拟合所导致的不确定度较高的主要原因是由于选取的标准溶液浓度范围过宽,样品测量值与标准溶液浓度平均值相差较远。经计算,乙二胺四乙酸二钠含量测定的合成不确定度为2.37%,扩展不确定度为4.74%,测量结果表示为(760.98±36.07)mg/kg,k=2。结论建立的不确定度评定方法适合高效液相色谱法测定面粉中乙二胺四乙酸二钠含量的不确定度分析。     

Extraction and fractionation of wheat flour proteins

Extraction of wheat flour with 1.5% sodium dodecyl sulphate (SDS) solution dissolved 65–67% of the total flour nitrogen. The SDS-insoluble proteinaceous material was separated into glycoproteins-I, II and III by ultracentrifugation. Part of the SDS-soluble proteinaceous material was precipitated by addition of ethanol and separated into glycoproteins-IV, glutenins and globulins. The rest of the dissolved proteinaceous material was separated into glycoproteins-V, gliadins, glycoproteins-VI, and albumins by (NH₄)₂SO₄-precipitation and gel filtration chromatography.     

蔬菜中微量铜的测定方法

建立测定蔬菜中微量铜的硫脲-EDTA 滴定新方法。样品经干法消解,在用溴化钾掩蔽汞干扰后的pH5～6 的消化液中,以砒啶偶氮萘酚为指示剂,用EDTA 标准溶液滴定能与EDTA 络合的所有金属离子的总量;然后在另一份用硫脲掩蔽Cu2+ 后的试液中,再用EDTA 滴定除Cu2+ 外的其他金属离子。两者之差即相当于铜的量。测定结果的相对标准偏差均小于2.50%,其加标回收率在96.8%～100.4% 之间。结果表明,改进后的方法具有简单、快捷、干扰小等特点。     

Cassava as a non-conventional filler in comminuted meat products

Cassava (Manihot esculenta) was used as an unconventional filler to produce affordable comminuted meat products that stored well under tropical conditions without refrigeration. The study involved two experiments. In experiment 1, five different emulsion-type pork sausages containing 5.4, 9.0 and 10.0% mould-free cassava flour, 5.4% crude full fat soy flour and a control without filler were assessed 0 and 7 days after preparation. A 40-member taste panel sensorily assessed the products in a 5 × 2 factorial (treatment × storage occasion) experiment based on the external appearance of the uncooked products and the external and internal colour, consistency, texture, aroma and taste of the cooked products. Although the panel judged products with 5.4% cassava flour as the best, the 9% inclusion level of cassava flour was found not to compromise the organoleptic qualities of the product. At this level 54 000 cedis (US$150) was saved on the cost of producing 1t of the product. In experiment 2, the sausages were pasteurised at 80 °C for 1 h and stored in a 4:1 vinegar-sugar solution or a 1:1:50 vinegar-sugar-water solution at 5 and 30 °C. Storage in 4:1 vinegar-sugar medium arrested bacterial growth over the 7-day monitoring period. It was concluded that 9% cassava flour could conveniently replace fat in comminuted meat products and a combination of pasteurisation and storage in vinegar-sugar solution is an effective method of storage of such products in the tropics.     

真空碱溶液润麦处理对全麦粉稳定性和品质特性的影响

为了得到低脂肪酶活性、高稳定性的全麦粉,将小麦在不同真空度(-0.04,-0.07 MPa)下用不同浓度Na_2CO_3溶液(0.10%,0.25%,0.50%)润麦处理,利用低场核磁共振技术(LF-NMR)探究真空润麦过程中水分迁移情况,测定不同浓度Na_2CO_3溶液润麦下小麦中脂肪酶的相对活性。将润麦后的小麦制成全麦粉后,测定重组全麦粉的储藏稳定性和品质特性。结果表明:润麦过程中小麦籽粒的A_(21)值持续上升,结合水含量增加;真空碱溶液润麦可以降低小麦籽粒中脂肪酶活性,增加全麦粉贮藏稳定性,当Na_2CO_3溶液浓度为0.5%时脂肪酶活性最低;对全麦粉的粉质特性、RVA和面团流变学分析表明,真空碱溶液润麦能显著延长全麦粉的稳定时间,增强面团中面筋筋力,提高全麦粉的糊化特性,增加全麦面团的黏弹性,Na_2CO_3溶液润麦可有效改善全麦粉的品质特性。     

流动注射法同时检测水中挥发酚和氰化物

目的建立连续流动注射分析仪同时测定末梢水中挥发酚和氰化物的分析方法。方法末梢水经过EDTA和抗坏血酸的混合溶液(20.0 g/L)预处理,用连续流动注射分析仪同时测定挥发酚和氰化物。结果末梢水样品预处理的条件为50 ml水样中加入0.5 ml EDTA和抗坏血酸的混合溶液(20.0 g/L),加标回收率为90.0%~105.0%,相对标准偏差为0.39%~5.85%,挥发酚和氰化物的检出限分别为0.000 2和0.000 4 mg/L。结论该方法精密度好,准确度高,符合分析质控要求。