基于拉曼光谱技术的山茶油不饱和度快速评价方法

为评价不同品种山茶油不饱和程度,有必要建立一种窄碘值范围（碘值差异小于10）的快速评价方法。本文以39组山茶油样品,10组市售油脂为研究对象,建立了一种基于线性回归、梯度下降法的高分辨拉曼光谱油脂碘值快速定量预测模型。采集不同饱和度的油脂样品在785 nm的拉曼谱图,采用平滑算法最小二乘平滑滤波（Savitzky-Golay）、多项式拟合和去卷积算法洛伦兹（Lorentzian）处理谱图信息。以筛选出的两个拉曼特征峰（1656 cm⁻¹和1440 cm⁻¹）的峰强比值（I_1656/1440）作为不饱和度评价指标,结合传统滴定法测得的碘值数据进行相关性分析,所建定量模型测试集的决定系数（R²）>0.82,均方误差（MSE）<0.73,均方根误差（RMSE）<0.85,可准确、快速地评价山茶油等油脂的不饱和度。     

食用油脂过氧化值分析检测方法研究进展

该文简要介绍食用油脂氧化过程、机理与产物,系统综述目前食用油脂过氧化值测定技术与方法,如:化学法、物理法及电分析法等研究现状、优势与存在问题;最后简述食用油过氧化值测定技术与方法发展趋势。     

Quantitative analysis of quercetin using Raman spectroscopy

Raman spectroscopy was used for the quantitative analysis of quercetin. Raman spectra were measured with an Ar ion laser at 488 nm. A 20× objective lens was used for focusing the laser beam on the sample. The back scattering light was passed into the monochrometer and detected with a CCD detector. The Raman band of a solvent (ethanol and methanol) was used as the internal standard to remove the effect of factors such as laser power and other instrumental effect. The band ratio between the Raman intensity of the sample and that of the solvent had good linearity with the analyte concentration. The equations of the calibration curve were y = 9.005x with an R² of 0.9998 and y = 11.50x with R² of 0.9999 in ethanol and methanol, respectively. The limit of detection (LOD) was 5 × 10⁻⁵ mol/L. The quantity of quercetin extracted from onion peels was determined by Raman spectroscopy. Masses in quercetins of 73 mg/100 g and 70 mg/100 g were extracted from dried onion peels by using hot ethanol and hot methanol for three hours. These values are in good agreement with results obtained by HPLC and UV–vis spectroscopy.     

石墨烯改性纤维中石墨烯含量的精确测定

目前我国石墨烯产业迅速发展,石墨烯纤维含量直接影响产品的性能和价格,但市场缺少规范统一的标准以规范石墨烯改性纤维含量的测定。文中首先采用红外光谱法对石墨烯改性纤维中主纤维成分进行定性,再通过拉曼光谱法对石墨烯成分进行定性,最终通过热重分析法精确定量出石墨烯含量。结果表明,此方法可有效应对新型纺织纤维的检测需求,促进光谱技术在新型纺织纤维鉴别上的广泛使用。     

Long-term stability of a Raman instrument determining iodine value in pork adipose tissue

The stability of a calibration model from a non-destructive Raman instrument during a period of three years was studied. A calibration model created on a dataset measuring pork adipose tissue in 2005 determining iodine value (IV), was transferred to a dataset measuring pork adipose tissue three years later in 2008. During these three years the fibre optic cable had been changed and the output of the laser was reduced to 60% compared with the power in 2005. The samples were also taken from different parts of the carcass. Aligning the peak positions and pre-processing with multiplicative scatter correction together with a selection of wavelengths/wavenumbers gave, for IV, a correlation coefficient of 0.95 for measured versus predicted IV of the 2008 samples. The accuracy expressed as root mean square error of prediction was 2.04 g iodine added to 100 g of melted fat with 6 partial least squares factors for the 2008 samples. This study shows that it is possible, with minor modifications, to transfer the model from spectra measured three years later on the same instrument. It is concluded that a quantitative use of Raman instruments are robust over time.     

猪油与3种植物油二元混合体系相容性研究

油脂相容性是影响调和油脂品质及稳定性的重要因素,本文通过测定猪油（LO）、菜籽油（RO）、大豆油（SBO）和椰子油（CNO）的基本理化性质,利用碘值、固体脂肪含量等温曲线（SFC-T）及偏差曲线（ΔSFC-T）对LO与RO/SBO/CNO的二元混合体系的不饱和度及相容性进行分析研究。结果表明:RO/SBO可以提高其与LO混合油脂的不饱和度,且与两种植物油脂质量分数呈正相关性,CNO则相反;不同比例的LO与RO/SBO/CNO混合油脂在5、10℃出现轻微共晶现象,在15⁵0℃出现偏晶现象;3种植物油脂中RO/SBO与LO相容性较好,CNO较差;混合油脂比例分别为1∶9（RO∶LO）、1∶9/2∶8（SBO∶LO）及1∶9（CNO∶LO）时,ΔSFC值在-1.5%²%范围内,油脂相容性最佳。      

硅胶用于降低油脂氧化产物的研究

利用硅胶的吸附特性,以过氧化值为指标,系统考察了硅胶来源、孔径、添加量、反应温度、反应时间等因素对降低油脂过氧化物的影响.通过单因素实验确定的工艺条件为:粗孔硅胶添加量30%,反应温度80℃,反应时间1.5h.在此工艺条件下,对大豆油、菜籽油、玉米油和葵花籽油的过氧化值降低效果进行了比较和验证,同时对其二级氧化产物的指标也进行了比较,结果表明采用硅胶吸附法降低油脂的氧化产物是可行的.     

偶合化学发光法测定食用油脂碘值的研究

为建立一种测定食用油脂碘值的化学发光新方法,选用椰子油、棕榈油和无水奶油等为材料,用含一氯化碘的乙酸溶液与油脂中的不饱和脂肪酸发生加成反应,余剩的一氯化碘与碘化钾作用生成的单质碘在碱性水溶液中氧化鲁米诺(Luminol)产生波长为425 nm的可见光,利用Luminol-I2偶合化学发光体系,对样品进行了测定。通过YN-FGI化学发光仪记录其发光面积。结果表明,碘(I3-)浓度在1.30×10-5～2.60×10-4mol/L范围内与相对发光面积呈现良好的线性关系,线性方程为Y=7.004×104X,相关系数r为0.997 1,碘(I3-)液检出限为6.0×10-6mol/L。对1.30×10-5mol/L的碘(I3-)液平行测定11次,其RSD为3.0%。样品与国标法对照测定无显著性差异,用于食用油脂碘值的测定,结果令人满意。     

微小电极快速测定植物油过氧化值准确度评价

研究设计了一种检测过氧化值的新方法,即采用壳聚糖修饰丝网印刷电极经微分脉冲溶出伏安法扫描,来取代碘量法中人工滴定确定碘离子浓度变化的步骤。采用该方法对40种市售植物油的过氧化值进行测定,并与国标法(GB/T 5538—2005)的测定结果进行比对,综合偏离度与En数2项指标进行评价,结果表明:2种方法在定性判定方面结果一致,而在定量判断方面有37个结果满意,整体满意率为92.5%,其中0.016~0.075 mmol/kg区间内的结果更为准确,满意率为91.6%。研究表明,与国标法相比,新方法在操作性、安全性等方面存在一定优势,在一定过氧化值范围内,结果准确性能够得到认可。     

红外光谱法测定植物油中游离脂肪酸质量分数的方法研究

游离脂肪酸的含量是评价植物油品质的的重要指标,红外光谱法具有快速准确、灵敏度高等特点,通过分析红外光谱图中基团的特征峰与游离脂肪酸含量之间的数学关系,建立了红外光谱法测定植物油中游离脂肪酸含量的方法。结果表明：不同种类的植物油的红外光谱谱图基本相同;以菜籽油为代表的植物油游离脂肪酸含量在20%以上时,脂肪酸含量与吸光度值在1708 .7cm-1处的线性相关性较好,y = 0.3323 x +0.017,R2= 0.9994;当游离脂肪酸在20%以下时,脂肪酸含量与吸光度值在在1714cm-1处C=O振动吸收峰的吸光度存在良好的线性关系,y = 0.2449x + 0.0243,R2= 0.9969;样品取样量对对红外吸收光谱吸光度影响不大,经过方法重复性和实际样品检测验证,红外光谱法能够准确测定植物油的游离脂肪酸的含量。     

食用油脂中p-茴香胺值的测定

对ISO中食用油脂的p-茴香胺值测定方法进行了验证,并对影响茴香胺值测定的影响因素进行了探讨。对几种食用油脂茴香胺值的测定结果进行统计分析表明,ISO法准确性、重复性好。在茴香胺值测定过程中应注意取样量、样品、试剂含水率等因素。另外,对于低含氧酸油脂,可以用正己烷代替ISO方法中的异辛烷试剂。     

Authentication of edible vegetable oils adulterated with used frying oil by Fourier Transform Infrared Spectroscopy

The application of Fourier Transform Infrared (FTIR) Spectroscopy to authenticate edible vegetable oils (corn, peanut, rapeseed and soybean oil) adulterated with used frying oil was introduced in this paper. The FTIR spectrum of oil was divided into 22 regions which corresponded to the constituents and molecular structures of vegetable oils. Samples of calibration set were classified into four categories for corn and peanut oils and five categories for rapeseed and soybean oils by cluster analysis. Qualitative analysis of validation set was obtained by discriminant analysis. Area ratio between absorption band 19 and 20 and wavenumber shift of band 19 were treated by linear regression for quantitative analysis. For four adulteration types, LODs of area ratio were 6.6%, 7.2%, 5.5%, 3.6% and wavenumber shift were 8.1%, 9.0%, 6.9%, 5.6%, respectively. The proposed methodology is a useful tool to authenticate the edible vegetable oils adulterated with used frying oil.     

不同饱和度的三酰甘油酯的共存对胆固醇氧化的影响

为了评价三酰甘油酯的不同饱和程度对胆固醇氧化的影响,将精制的沙丁鱼油三酰甘油酯(碘价IV=182.6)、部分氢化沙丁鱼油三酰甘油酯(IV=174.5)、全氢化沙丁鱼油三酰甘油酯(IV=92.0)分别与胆固醇混合,制成CST、CTPH和CTFH三组试样,在25℃避光处诱导其氧化。研究结果表明:试样的氧化稳定性随着上述各试样的不饱和程度的增加而降低。CST的过氧化物诱导期比CTPH的短,并且在较短的诱导期内CST中组成沙丁鱼油三酰甘油酯的高度不饱和脂肪酸(PUFA)比CTPH的明显减少。各试样中生成的主要胆固醇氧化物有7-β-羟基胆固醇、7-酮基胆固醇、β-环氧化胆固醇和胆甾烷三醇。胆固醇氧化物的生成量随着过氧化物价(POV)的变化和PUFA的减少而增加。胆固醇的氧化与共存的鱼油三酰甘油酯的自动氧化有关。尽管在胆固醇氧化物生成阶段,降低鱼油三酰甘油酯的不饱和度可有效地延缓胆固醇的氧化,但是在诱导期以后胆固醇的氧化速率与CST和CTPH中PUFA的比例无关。     

自动电位滴定法测定油脂皂化值

采用电位滴定仪测定了油脂的皂化值,利用电位滴定仪能够识别多个滴定终点的特点,采用分步滴定法用盐酸分别滴定皂化液中过量的氢氧化钾和生成的钾皂,根据滴定钾皂消耗的盐酸的量可计算出样品的皂化值.分别采用全自动电位滴定法和国标GB/T 5534-2008规定的方法对3个不同菜籽油样品各平行测定6次,前者测定结果的相对标准偏差为0.16％～0.22％,优于国标方法测定结果的相对标准偏差0.36％～0.81％.     

2019—2023年食用油、油脂及其制品国家食品安全监督抽检结果分析

目的 分析我国2019—2023年食用油、油脂及其制品的食品安全形势。方法 汇总2019年至2023年食用油、油脂及其制品的国家安全监督抽检结果, 对其整体和不合格项目等信息进行分析。结果 2019—2023年食用油、油脂及其制品不合格率总体呈下降趋势;不合格产品主要产自新疆、吉林、安徽、湖北、内蒙古、江西等地区;菜籽油、花生油、芝麻油、大豆油是2019年-2023年抽检中的主要不合格食用油品种;检出的不合格项目主要有苯并[a]芘、酸价（以KOH计）、过氧化值、溶剂残留量。结论 新疆、吉林、安徽等高不合格率省份应加强源头管控,推广规模化种植和标准化仓储,升级生产技术与监管,强化抽检和追溯机制;严格按照生产工艺标准生产,合理存储,提高食用油品质;应加强对菜籽油、花生油、芝麻油、大豆油等不合格率高的产品的抽检力度。     

脂肪酸的链长和不饱和度对脂肪酸-普通玉米淀粉复合物理化性质的影响

为探讨脂肪酸对玉米淀粉性质的影响,采用快速黏度分析仪、差示扫描量热仪及动态流变仪研究了6种不同链长和不饱和程度的脂肪酸对普通玉米淀粉糊化性质、热学性质及流变学性质的影响。研究结果表明,添加6种脂肪酸对普通玉米淀粉的糊化温度无明显影响,可使普通玉米淀粉的峰值黏度约下降8.22%~14.71%。除棕榈酸外,其余脂肪酸均能使普通玉米淀粉的糊化焓值降低,脂肪酸碳链越短,不饱和度越低,普通玉米淀粉的糊化焓值越低。共轭亚油酸-普通玉米淀粉复合物的抗老化效果最好,添加共轭亚油酸使原淀粉长期老化率约下降28.36%。随着脂肪酸不饱和度的增加,普通玉米淀粉的表观黏度逐渐增加。添加6种脂肪酸使普通玉米淀粉的tanδ降低,有利于其弹性凝胶的形成。     

加工精度对大米食用品质及风味的影响

结合留皮度和碾减率表征大米加工精度,研究加工精度对大米食用品质的影响,并采用同时蒸馏提取-气相色谱-质谱联用法分析米饭中的挥发性风味物质,为大米适度加工提供借鉴.结果表明:随碾磨时间增加,碾减率变化可用一条二次曲线(R2 =0.997 3)和一条线性方程(R2=0.992 5)拟合,留皮度可由一条函数方程(R2 =0....     

Improving the determination of moisture in edible oils by FTIR spectroscopy using acetonitrile extraction

A Fourier transform infrared (FTIR) method developed for the analysis of moisture in edible oils using dry acetonitrile as the extraction solvent was re-examined with the objective of improving its overall sensitivity and reproducibility. Quantitation was based on the H-O-H bending absorption at ～1630 cm(-1) instead of the bands in the OH stretching region, fewer interferences being an issue in the former as opposed to the latter region. In addition, a spectroscopic dilution correction procedure was developed to compensate for any miscibility of oil samples with acetonitrile, and gap-segment 2nd derivative spectra were employed to minimise the associated possibility of spectral interferences from absorptions of the oils. In comprehensive standard addition experiments using a variety of edible oils, the FTIR method was shown to recover the amounts of water quantitatively added to dry oil with an accuracy of ±20 ppm when the spectra of the acetonitrile extracts of the water-spiked oils were ratioed against the spectra of the acetonitrile extracts of the corresponding dry oils. The accuracy deteriorated substantially when the spectra of the acetonitrile extracts of the water-spiked oils were ratioed against the spectrum of the acetonitrile extraction solvent only. However, the primary variable affecting the apparent difference in the accuracy of the two approaches was determined to be the variability in the residual moisture content of the dried oils used in the standard addition experiments, as confirmed by an FTIR procedure based on H-D exchange with D(2)O. The FTIR method as structured is amenable to automation (>120 samples/h) and provides a very competitive means by which to routinely measure moisture present in a variety of hydrophobic materials that are normally the domain of Karl Fischer titration, such as edible oils, mineral oils, biodiesel and fuels.