浅析影响食品饮料中糖分检测的因素

糖类是食品饮料中的重要组成部分。糖类物质是食品工业的主要原料和辅助材料。食品饮料中的糖分的高低不仅影响产品的口感、风味,而且会影响到产品的保质期。因此,食品生产企业必须严格控制食品饮料中的糖分的高低并且能够有效地检测出它的含量。本文从食品饮料中糖分的检测方法出发,主要论述了食品饮料中微量糖分检测的技术要领及其检验中的关键步骤,以实用性强,检测结果准确可靠为宗旨。特别是对于加工低糖、"无糖"食品及干型、半干型葡萄酒、黄酒、果酒的企业来说,提供一种检测技术以指导企业的生产。

食品饮料中糖分检测的重要性及影响检测的因素分析

本文介绍了在食品饮料生产中,糖分检测的重要性及其检测的主要方法和影响食品饮料中糖分检测准确性的主要因素,要依据食品饮料的糖分形式、含糖量选择合适的检测方法,要注意沉淀剂的选择和斐林氏溶液的保存、标定。在滴定法检测中要严格遵循规定进行操作,保证检测结果的准确、可靠。

基于便携式近红外光谱仪的樱桃番茄糖分快速分析模型

为实现对樱桃番茄糖分的现场快速无损检测,应用便携式近红外光谱仪器AMBERⅡ对所采集樱桃番茄的近红外光谱数据进行建模分析。实验样本共172个,利用Kennard-Stone(K-S)算法以3∶1比例划分样本集。光谱预处理选用Savitzky-Golay卷积平滑和标准归一化(standard normal variate,SNV),分别使用无信息变量消除法(uniformative variable elimination,UVE)、连续投影算法(successive projections algorithm,SPA)和无信息变量消除结合连续投影算法(UVE-SPA)3种算法进行特征波长提取,用偏最小二乘(partial least squares,PLS)方法建模,最终使用UVE-SPA算法提取得到12个特征波长点进行PLS建模的结果最佳,建模集和预测集的决定系数R^(2)分别为0.9385和0.9347,建模集和预测集的均方根误差分别为0.1305和0.1744,相对分析误差(relative percent deviation,RPD)为2.81。研究表明,利用以上方法提取的特征波长点所建立的模型预测效果较好,说明便携式近红外光谱仪器可以应用于对樱桃番茄糖分的现场快速无损检测。

基于太赫兹光谱的奶粉中葡萄糖及蔗糖定性定量检测方法

奶粉富含人体所需的五大营养物质,是婴幼儿主要的营养来源之一,奶粉中的营养成分对婴幼儿的生长发育具有重要影响,除乳糖外的糖类含量超标可能对婴幼儿健康产生不良影响。由于奶粉成分复杂,目前的色谱法和近红外光谱法检测技术都难以满足奶粉糖分快速无损检测的要求,因此亟须探索一种奶粉中葡萄糖、蔗糖含量快速无损检测方法。太赫兹波对不同大分子物质的吸收峰具有“指纹”特性,可利用该特性对不同的大分子物质进行识别。应用太赫兹时域光谱技术(THz-TDS)并结合化学计量学方法对奶粉中葡萄糖、蔗糖两种糖分的定性定量检测方法进行了研究。实验装置采用TAS7500TS太赫兹光谱系统,实验样品为不含糖的婴幼儿奶粉和纯度大于99%的葡萄糖、蔗糖晶体及不同梯度浓度的奶粉-葡萄糖、奶粉-蔗糖混合物,实验分别采集了3种纯品样品及15种不同梯度浓度的奶粉-葡萄糖、奶粉-蔗糖混合物样品的太赫兹时域信号,每个样品采集三次并取平均值作为其时域光谱信号,经快速傅里叶变换(FFT)得到各样品的太赫兹频域信号,再根据Dorney提出的光学参数提取公式计算得到各样品的吸收系数谱和折射率谱。最后分别基于两组混合物样品的吸收系数谱和折射率谱数据,采用偏最小二乘法(PLS)建立相应的定量分析模型,校正集和预测集样品比例为2∶1。实验结果表明,奶粉在太赫兹波段无明显特征吸收峰,葡萄糖和蔗糖分别在1.45, 1.8, 1.98, 2.7 THz和1.5, 1.9, 2.6 THz频率处有较强的特征吸收峰,可根据两种物质的太赫兹指纹特征峰进行定性分析。不同梯度浓度的两组混合物的整体吸收峰位置与葡萄糖、蔗糖纯品太赫兹吸收峰位置基本一致,具有稳定的吸收特性。基于吸收系数谱和折射率谱数据建立偏最小二乘法模型,均可实现奶粉中葡萄糖和蔗糖的定量分析,且由折射率谱建立的葡萄糖、蔗糖定量回归模型效果均优于由吸收系数谱建立的模型效果,其中,奶粉-葡萄糖混合物中葡萄糖含量PLS模型的校正集相关系数( R c)及均方根误差(RMSEC)分别为0.99和0.18%,预测集 R P及RMSEP分别为0.96和0.66%,奶粉-蔗糖混合物中蔗糖含量PLS模型的校正集 R c及RMSEC分别为0.96和0.55%,预测集 R P及RMSEP分别为0.99和0.25%,葡萄糖和蔗糖定量模型的预测效果均较为理想。研究结果表明THz-TDS技术可有效用于奶粉中葡萄糖和蔗糖定性定量分析,为运用THz-TDS技术开展奶粉掺假及品质快速检测方法研究提供参考。

Analysis of Sugar Components of Fermented Rice Wine by Ion Chromatography

[Objective] The aim was to analyze sugar components in fermented rice wine by ion chromatography. [Method] The optimal condition for chromatography system of sugar analysis was selected by measuring sugars in fermented rice wine with ion chromatography and pulsed amperometric detection. [Result] The optimal measurement conditions were as follows： Leacheate （Leachate）, consisting of NaOH and CH3COONa, was eluted by gradient concentrations, with column temperature at 35 ℃ and flow rate at 0.4 ml/min. In the condition, sugars in rice wine were ana- lyzed and the results showed that the method is featured by low detection limit, good repetition and high recovery rate. [Conclusion] The research establishes and determines the approaches and optimum conditions for sugar analysis in rice wine by ion chromatography and pulsed amperometric detection, providing references for advancement of research on quality improvement of fermented rice wine.

Analysis of Oseltamivir Resistance Substitutions in Influenza Virus Glycoprotein Neuraminidase using a Lentivirus-Based Surrogate Assay System

Influenza A virus poses a great threat to global health, and oseltamivir (trade marked as Tamiflu), which targets influenza surface glycoprotein neuraminidase (NA), is used clinically as a major anti-influenza treatment. However, certain substitutions in NA can render an influenza virus resistant to this drug. In this study, using a lentiviral pseudotyping system, which alleviates the safety concerns of studying highly pathogenic influenza viruses such as avian influenza H5N1, that utilizes influenza surface glycoproteins (hemagglutinin or HA, and NA) and an HIV-core combined with a luciferase reporter gene as a surrogate assay, we first assessed the functionality of NA by measuring pseudovirion release in the absence or presence of oseltamivir. We demonstrated that oseltamivir displays a dose-dependent inhibition on NA activity. In contrast, a mutant NA (H274Y) is more resistant to oseltamivir treatment. In addition, the effects of several previously reported substitution NA mutants were examined as well. Our results demonstrate that this lentivirus-based pseudotyping system provides a quick, safe, and effective way to assess resistance to neuraminidase inhibitors. And we believe that as new mutations appear in influenza isolates, their impact on the effectiveness of current and future anti-NA can be quickly and reliably evaluated by this assay.

Self-assembled vertically aligned gold nanorod super-lattices for ultra-high sensitive detection of molecules

We show that self-assembled vertically aligned gold nanorod （VA-GNRs） superlattices can serve as probes or substrates for ultra-high sensitive detection of various molecules. D-glucose and 2,4,6-trinitrotoluene （TNT） have been chosen as model systems due to their very low Raman cross-sections （5.6× 10-30 cm2.molecule-1.sr-1 for D-glucose and 4.9 × 10-31 cm2.molecule-1.sr-1 for TNT） to show that the VA-GNR superlattice assembly offers as low as yoctomole sensitivity. Our experiment on mixed samples of bovine serum albumin （BSA） and D-glucose solutions demonstrate sensitivity for the latter, and the possible extension to real samples. Self-assembled superlattices of VA-GNRs were achieved on a silicon wafer by depositing a drop of solvent containing the GNRs and subsequent solvent evaporation in ambient conditions. An additional advantage of the VA-GNR monolayers is their extremely high reproducible morphology accompanied by ultrahigh sensitivity which will be useful in many fields where a very small amount of analyte is available. Moreover the assembly can be reused a number of times after removing the already present molecules. The method of obtaining VA-GNRs is simple, inexpensive and reproducible. With the help of simulations of monolayers and multilayers it has been shown that superlattices can achieve better sensitivity than monolaver assembly of VA-GNRs.

Enzyme-free and multiplexed micro RNA detection using micro RNA-initiated DNA molecular motor

In this work,we have developed a sensitive,simple,and enzyme-free assay for detection of micro RNAs(mi RNAs)by means of a DNA molecular motor consisting of two stem-loop DNAs with identical stems and complementary loop domains.In the presence of mi RNA target,it can hybridize with one of the stem-loop DNA to open the stem and to produce a mi RNA/DNA hybrid and a single strand(ss)DNA,the ss DNA will in turn hybridize with another stem-loop DNA and finally form a double strand(ds)DNA to release the mi RNA.One of the stem-loop DNA is double-labeled by a fluorophore/quencher pair with efficiently quenched fluorescence.The formation of ds DNA can produced specific fluorescence signal for mi RNA detection.The released mi RNA will continuously initiate the next hybridization of the two stem-loop DNAs to form a cycle-running DNA molecular motor,which results in great fluorescence amplification.With the efficient signal amplification,as low as 1 pmol/L mi RNA target can be detected and a wide dynamic range from 1 pmol/L to 2 nmol/L is also obtained.Moreover,by designing different stem-loop DNAs specific to different mi RNA targets and labeling them with different fluorophores,multiplexed mi RNAs can be simultaneously detected in one-tube reaction with the synchronous fluorescence spectrum(SFS)technique.