A Modified Methodology to Evaluate Viscosity of Non-Newtonian Liquid Foods with a Flow Channel Instrument

Through experimental analysis of the liquid flows in a flow channel instrument, prompt evaluation of the physically defined viscosity of non-Newtonian liquid foods was investigated for development into a structurally simple and easy-to-use viscometer. For Newtonian and non-Newtonian test liquids, a relation between the friction coefficient and Reynolds number, which was dimensionless as derived from an expression of analysis as a gravity current, indicated a condition under which the flow in the instrument was laminar and under which an average shear rate was on the order of less than 1 s~. Prediction organized based on this empirical relation reproduced practically the flow curve determined for the liquid foods using a rotor type viscometer. Utilization of the channel instrument as a viscometer was formulated in terms of physical meanings of measurements such as the flow length and elapsed time.

Selecting the Packaging System for Liquid Foods Using an ANP Model

This paper provides a model to identify the most appropriate packaging system （i.e. the industrial process by which the product is hygienically coupled with the container） for different liquid foods. The model developed is grounded on the Analytic Network Process （ANP） methodology, a powerful and flexible tool used in decision making. To select the appropriate packaging system, the model takes into account several factors, including packaging material, cost, safety, performance （e.g., speed and accuracy）, plant reliability and flexibility, which may directly or indirectly affect the suitability of the process. Moreover, the chemical and physical properties of commercial liquid foods, and the packaging technology are included in the model as further variables to be considered for the final choice. We try to answer the following research questions： is a filling system appropriate for a given liquid food？ Is it compatible with a defined packaging technology？ When several filling systems are available for a given liquid food, how can the most appropriate one be selected？ The ease of application of the model and the robustness of the results provided have been tested on a sample of 59 commercial liquid foods, for which the model allowed to identify the most suitable packaging system, providing useful practical guidelines. The model was developed in close collaboration with a panel of experts, operating in the beverage bottling industry, and validated by the same experts; thus, the resulting tool is suitable for use as a decision support system by food and bottling industries.

Changes in electrical conductivity of liquid foods during ohmic heating

Ohmic heating is a food processing method in which alternating current(AC)went through a food sample and resulted in internal energy generation in foods.It is an alternative fast heating technique.Its principal advantage is the ability to rapidly and uniformly heat food materials of various densities.During ohmic heating,change in electrical conductivity was observed.The intensity of food materials’electrical conductivity or overall resistance critically controls ohmic heating rate.An ohmic heating set-up was prepared under this project.Tomato juice was heated(about 32℃ to 80℃)in a batch type ohmic heater at different voltage gradients in the range of 50-70 V/cm.It was statistically found that the voltage gradient had significant impact on conductivity and system performance coefficient(SPC)(P<0.05).It was concluded that the electrical conductivity values linearly increased with temperature.The SPCs of the system ranged between 0.779 and 0.943.The value of R2 of the linear model was greater than 0.98.

Determination of Sym-triazine Residues in Animal-derived Food by Liquid Chromatography-High Resolution Mass Spectrometry

[Objective]The research aimed to establish a liquid chromatography-high-resolution mass spectrometry for detecting residues of diclazuril,toltrazuril and its metabolites in animal-derived food.[Method]The samples were pre-treated by QuEChERS technology and detected by Exactive liquid chromatography-high resolution mass spectrometry.The liquid chromatography-high-resolution mass spectrometry for detecting the residues of diclazuril,toltrazuril,toltrazuril sulfone and toltrazuril sulfoxide in animal-derived food was established.[Result]Diclazuril,toltrazuril,toltrazuril sulfone and toltrazuril sulfoxide showed a good linear correlation in the range of 2.0-50.0μg/L（r^2〉0.99）.The average recoveries of these four compounds in bovine power at the spiked levels of 2,10 and 20μg/kg were 74.5%-90.1%,and the relative standard deviations（RSD）were 15.4%-17.5%.[Conclusion]This method was stable and reliable,and could be used to detect diclazuril,toltrazuril,toltrazuril sulfone and toltrazuril sulfoxide in animal-derived food.

Determination of Cobalt in Food, Environmental and Water Samples with Preconcentration by Dispersive Liquid-Liquid Microextraction

A new method for the determination of cobalt was developed by dispersive liquid-liquid microextraction preconcentra-tion and flame atomic absorption spectrometry. In the proposed approach, 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide (DPTH) was used as a chelating agent, and chloroform and ethanol were selected as extraction and dispersive solvents. Some factors influencing the extraction efficiency of cobalt and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent, and extraction time, were studied and optimized. Under the optimum conditions, a preconcentration factor of 8 was reached. The detection limit for cobalt was 12.4 ng?mL–1, and the relative standard deviation (RSD) was 3.42% (n = 7, c = 100 ng?mL–1). The method was successfully applied to the determination of cobalt in food, environmental and water samples.

Supported Liquid Membrane Extraction Technology and Its Application in Detection of Meat Security

As a novel technology,supported liquid membrane extraction has gradually become the direction of the research of extraction,for the advantages of using little organic solvents,good selectivity and repeatability.This paper is based on describing the working principle,structure and infiuencing factors of supported liquid membrane,and research in domestic and foreign literatures which are in the same period, and give a review on the application of supported liquid membrane in meat security determination.

Simultaneous Determination of Catechins and Caffeine in Green Tea-Based Beverages and Foods for Specified Health Uses

Catechins in green tea have various useful features including antioxidant activity and preventive effects on metabolic syndrome. Various beverages that are enriched with tea catechins are marketed as Foods for Specified Health Uses (FOSHU) in Japan. However, recent reports have indicated that excessive consumption of green tea extracts as a dietary supplement are associated with adverse health effects such as liver disorders. Various catechins and caffeine are constituents of FOSHU tea-based beverages. The amount of catechins in FOSHU products is displayed on labels as total catechin content, but the content of individual catechins are not provided. Although health hazards of FOSHU products have rarely been reported, precise information about the content and types of catechins in FOSHU products is needed to ensure safety. We used high-performance liquid chromatography with a photodiode array (HPLC/PDA) to simultaneously identify and quantify catechins and caffeine in green tea-based popular beverages and FOSHU beverages. This technique allowed simultaneous quantitation of five types of catechins and caffeine in green tea without complicated sample preparation. Epigallocatechin gallate (EGCG) and epigallocatechin EGC were the main catechins in various FOSHU beverages and the concentrations of almost all catechins were higher in FOSHU, than in popular green tea-based beverages. The concentrations of EGCG in green tea-based popular beverages and in FOSHU beverages were 5.4 - 7.3 and 10.2 - 41.9 mg/100mL, respectively, with the highest concentration being in a product named Healthya (approximately 147 mg/bottle). The simultaneous determination of compounds such as catechins and caffeine in FOSHU beverages can help to estimate beneficial and adverse effects to prevent deleterious effects on health and the excessive consumption of FOSHU beverages containing high concentrations of tea catechins should be avoided.

固相萃取-高效液相荧光法测定食品接触材料中双酚A、双酚F和双酚S的迁移量

本研究建立了同时检测食品接触材料中双酚A、双酚F和双酚S的固相萃取-高效液相荧光的分析检测方法。根据食品类型,选择水性和油性食品模拟液进行迁移实验,浸提液经HLB固相萃取柱富集、浓缩、净化提取,采用甲醇-水作为流动相,荧光检测器检测。试验表明,在0.10~100.0μg/L质量浓度内线性关系良好,相关系数≥0.9997,双酚A、双酚F的检出限均为0.02μg/L,双酚S的检出限为0.05μg/L。测得3种双酚类物质在5种食品模拟液中加标回收率分别为80.2%~100.1%、83.3%~101.6%、77.6%~90.7%,相对标准偏差(RSD)为1.7%~4.0%,方法符合研究要求。同时模拟液在60℃浸提30 min条件下测定了市售4款食品接触材料的180个样品,,结果在5个样品中检测到双酚类物质迁移量。该方法灵敏、检测快速、结果准确,适用于食品接触材料中双酚A、双酚F和双酚S迁移量研究。

在线固相萃取-液相法测定食品中胡萝卜素

目的:采用两泵一阀的在线固相萃取-高效液相色谱技术建立一种能够快速检测食品中胡萝卜素的方法,避免了胡萝卜素在复杂前处理过程中的损失。方法:在线固相萃取柱PLRP-S(2.1 mm×12.5 mm)液相分离色谱柱PAH(2.1 mm×100 mm,1.8μm);固相萃取泵流动相,水+甲醇,液相分离流动相,甲醇+二氯甲烷;检测波长450 nm。结果:该方法在0.10~2.00μg/mL保持良好的线性,方法的检出限和定量限均能够满足检测需求。α-胡萝卜素回收率为92.0%~105.4%,β-胡萝卜素回收率91.1%~107.2%。结论:该方法利用两泵一阀的在线固相萃取技术,能高效、快速检测食品中胡萝卜素,检测效率高,前处理提取效率好,方法能够满足检测需要。

基于食品冻结曲线的小龙虾液氮速冻装备设计与试验

针对液氮速冻产品冻裂率高、液氮损耗量大的问题,基于食品冻结曲线,设计三腔体液氮速冻设备,包括预冷腔(4.2 m,-70℃)、结晶腔(5.8 m,-100℃)和深冷腔(5.0 m,-120℃)。相较于单腔体液氮速冻设备(15.0 m,-100℃),三腔体液氮速冻设备使预包装调理小龙虾的冻结时间缩短10.0%,冻裂率降低40.4%,液氮节约15.0%;质构(硬性、弹性、内聚性、回复性、咀嚼性)和色泽(L*,b*)显著改善,挥发性盐基氮显著降低,水分、盐溶性蛋白和感官(色泽和质地)品质显著提高。研究为液氮速冻技术和装备的改进提供参考和借鉴。

减肥类保健食品中酚酞、西布曲明基体标准物质的研制

介绍了减肥类保健食品中酚酞、西布曲明基体标准物质的研制过程。采用阴性加标的方式,向保健食品模拟基质中添加酚酞、西布曲明标准溶液,混匀后分装制成保健食品标准样品。采用高效液相色谱-三重四级杆串联质谱法对其中酚酞、西布曲明的含量进行检测,并对样品中酚酞、西布曲明含量的均匀性和稳定性进行评价,5家实验室协作定值,评估定值的不确定度。研制的减肥类保健食品中酚酞、西布曲明基体标准物质定值结果分别为(19.8±2.95)、(18.8±3.03)mg/kg,均匀性和稳定性良好。研制流程和结果符合基体标准物质定值的要求,该标准物质可用于相关基质样品检测的实验室内部质量控制。

酸奶中乙酰磺胺酸钾、苯甲酸、山梨酸和糖精钠的检测方法

[目的]建立使用高效液相色谱仪同时检测酸奶中的乙酰磺胺酸钾等4种食品添加剂的方法。[方法]酸奶样品经过蛋白沉淀剂沉淀蛋白后高速离心,经0.22μm微孔滤膜过滤后上机测定。仪器使用C18色谱柱,流动相采用甲醇与0.02 mol/L乙酸铵溶液(不需调节pH值),检测波长为227 nm。[结果]4种添加剂线性范围1.00~50.0 mg/L,相关系数均在0.999 9以上,回收率91.2%~104.8%。[结论]该方法操作简单、快速,可用于同时检测酸奶中的乙酰磺胺酸钾、苯甲酸、山梨酸和糖精钠4种食品添加剂。

超高效液相色谱-串联质谱法测定固体减肥类保健食品中的丙酮酸盐

目的建立超高效液相色谱-串联质谱法测定保健食品中丙酮酸盐的检测方法。方法保健食品经过研磨,萃取等处理步骤后,将萃取液酸化之后以游离丙酮酸的形式,采用超高效液相色谱-串联质谱仪中进行测定。结果丙酮酸钠在0.1~10.0μg/mL的范围内线性良好,丙酮酸钠的检出限为20 ng/mL,定量限为50 ng/mL;在0.25、2.50和7.50μg/mL的质量浓度条件下,回收率分别为87.36%~94.19%,相对标准偏差均小于10%(n=6)。结论本研究样品制备步骤简便、检测灵敏度高、重复性好,可用于快速准确的测定食品中的丙酮酸的含量,为丙酮酸的合理规范应用提供技术支撑。

固相萃取-液相色谱串联质谱法测定婴儿食品中的4种添加剂

本文建立了一种测定婴儿食品中4种常用食品添加剂(香豆素、香草醛、甲基香草醛和乙基香草醛)的方法。结果表明,各目标物质的质量浓度在50~5000 ng·mL^(-1)时线性关系良好,检测限和定量限分别为10μg·kg^(-1)和50μg·kg^(-1);加标浓度为50μg·kg^(-1)、100μg·kg^(-1)、500μg·kg^(-1)时,回收率为81.72%~102.13%,相对标准偏差低于10%。说明该方法精准可靠,可用于婴儿食品基质中常见添加剂的检测。

全降解纤维素食品包装的制备及保鲜性能研究

为探究纤维素在食品保鲜中的应用,通过[Emim]EDP离子液体实现纤维素均相改性,制备得到不同季铵化程度的纤维素膜,考察其抗菌、耐水、阻气、力学性能以及对草莓的保鲜效果。结果表明,当季铵化程度为0.8时,得到的纤维素膜具有优异的广谱抗菌、耐水和阻气性能,以及最佳的力学性能,抗拉强度和拉伸率分别为6.99 MPa和122%。QCL0.8膜包装的草莓分别比无包装、PE包装的草莓延长3,6 d货架期,可以在土壤中经23 d完全降解。研究为替代不可降解的石化塑料包装材料提供新的选择。

分散液液微萃取技术在液态食品分析中的应用

分散液液微萃取技术(Dispersive Liquid-Liquid Microextraction,DLLME)是一种新型的样品前处理方法,它具有有机试剂用量少、操作简便快速等优点,广泛应用于食品样品中痕量目标物的提取。本文阐述DLLME的类型,DLLME技术在液态食品分析中的应用,以期能为后续研究者在DLLME领域的进一步开发与创新提供思路。

几种发酵食品生物胺含量检测与食用安全性分析

生物胺是一类人体所需、具有生物活性的小分子含氮化合物,过量摄入可造成人体出现不良反应。该研究利用高效液相色谱法对食用酱,泡菜、奶酪和腐乳等四类发酵食品进行生物胺含量检测与分析。结果表明食用酱中主要存在的生物胺种类为苯乙胺、腐胺、组胺和酪胺,生物胺总含量范围在331.40~624.42 mg/kg之间;某些腐乳产品中生物胺含量较高,总含量可达2355.32和1091.05 mg/kg。相比于食用酱和腐乳,泡菜和奶酪中检测出的生物胺含量较低,其中泡菜中生物胺含量最高的为酸豆角,总生物胺为126.65 mg/kg,最低的为泡藕节,总生物胺含量为22.32 mg/kg。另外,本研究还基于发酵食品食用特性、组胺和酪胺生物学毒理学性质,结合食用场景和危害风险评估分析食用酱和腐乳而引起的生物胺食用安全性,结果表明摄食这几种食品生物胺毒性危害风险较低,食用安全性高。该文为消费者深入了解我国传统发酵食品的食用安全性提供了重要依据。

同位素内标-超高效液相色谱-串联质谱法快速测定食品中米酵菌酸及异米酵菌酸

建立一种快速测定不同食品中米酵菌酸和异米酵菌酸的超高效液相色谱-串联质谱联用方法。样品中待测物用含0.1%氨水的甲醇-水溶液(体积比为4∶1)提取后,经过MFC335柱净化,BEH C_(18)色谱柱分离,负离子扫描,多反应监测模式检测,同位素内标法定量。两种待测物在0.5~200μg/L质量浓度范围内线性良好,相关系数均大于0.995,检出限和定量限分别为0.2、0.6μg/kg,平均回收率范围为90.6%~109.2%,测定结果的相对标准偏差为2.0%~11.2%(n=6)。该方法适用于各类食品基质中米酵菌酸和异米酵菌酸的快速筛查与公共卫生应急检测。

超高效液相色谱法测定食品接触材料中抗氧剂245的迁移量

以水、4%(体积分数,下同)乙酸溶液、10%(体积分数,下同)乙醇溶液、20%(体积分数,下同)乙醇溶液、50%(体积分数,下同)乙醇溶液、95%(体积分数,下同)乙醇溶液和异辛烷作食品模拟物,按照GB 5009.156—2003和GB 31604.1—2015进行迁移试验。前5种食品模拟物的浸泡液用0.22μm有机滤膜过滤后,滤液上机测定。分取10 mL 95%乙醇溶液浸泡液,于50℃旋蒸至近干,分两次加入8 mL 80%(体积分数,下同)甲醇溶液溶解残渣并稀释至10 mL,上机测定;分取10 mL异辛烷浸泡液,加入10 mL 80%甲醇溶液,摇动约1 min混匀,静置约30 min,收集下层相并用80%甲醇溶液稀释至10 mL,过0.22μm有机滤膜,滤液上机测定。在超高效液相色谱法分析中,采用ACQUITY UPLC BEH C_(18)色谱柱作固定相,80%甲醇溶液为流动相进行等度洗脱,在220 nm检测波长下采用二极管阵列检测器测定抗氧剂245的含量。结果显示,抗氧剂245的质量浓度在0.5~10.0 mg·L^(-1)内和峰面积呈线性关系,测定下限为0.14~0.30 mg·L^(-1)。按照标准加入法进行回收试验,回收率为86.4%~104%,测定值的相对标准偏差(n=6)为2.0%~5.4%。方法用于不同材质食品接触材料样品的分析,仅在聚甲醛(POM)盖样品中检出了抗氧剂245,在不同食品模拟物中的迁移量由大到小排序为50%乙醇溶液、95%乙醇溶液、20%乙醇溶液、10%乙醇溶液和4%乙酸溶液。

二维液相色谱技术在食品检测中的探索应用

介绍了二维液相色谱技术与高效液相色谱技术的区别,阐述了二维液相色谱技术在食品营养检测、添加剂检测、有毒有害物质检测等方面的应用。利用实例对该技术方法进行了展示,以期对食品安全检测领域提供有效的参考和借鉴。