Thermal Stability Assessment of Vegetable Oils by Raman Spectroscopy and Chemometrics

Vegetable oils are widely used in culinary, e.g. in deep frying, cooking, and baking. During these processes, the oils are submitted to high temperatures, giving rise to unhealthy compounds. The risk for the health related to oil consumption resulted in a search for more healthy and stable oils, which could maintain their properties during the cooking process. The aim of this work was to evaluate the thermal stability of the most common oils used for cooking in Brazil by Raman spectroscopy. Eight types of vegetable oils (cotton, extra virgin olive oil, refined olive oil, canola, coconut, sunflower, corn, and soybean) were evaluated, heating them at temperatures ranging from 25 °C to 205 °C. The stability of oils presented high correlation with their smoke points. As expected, the more evident spectral changes were observed in the oils that present lower smoke points. The refined oils, which in general present higher smoke points, presented better stability. In this study, the more stable oils were sunflower, cotton, and canola. These results showed that Raman spectroscopy allied with chemometric tools as a fast and accurate method to evaluate the thermal stability of edible oils. At the same way, this technique could be employed to monitor and check the quality of oils used in restaurants.     

Characterization of Croatian Honeys by Right-Angle Fluorescence Spectroscopy and Chemometrics

The potential of right-angle fluorescence spectroscopy and selected chemical parameters for discrimination of botanical origin of Croatian honey types (n = 55) previously classified by physicochemical and melissopalynological analyses was evaluated. Systematic step-by-step fluorescence analysis included the measurement of complete excitation-emission matrix (EEM) in the range of excitation wavelengths from 260 to 400 nm, and emission wavelengths from 300 to 600 nm, followed by fluorescence intensity measurement at detected peaks of different excitation/emission wavelengths, and emission spectra recordings at selected specific excitation wavelengths of honey solutions in 50 mmol L^?1 phosphate buffer pH 7.0 and methanol. A total of five different sets of emission spectral data for buffer and two for methanolic honey solutions were considered for chemometric analysis of original and normalized emission spectra including principal component analysis and linear discriminant analysis. Additionally, chemical analysis of buffer and methanolic honey solutions included determination of protein, total polyphenol and reactive amino group content. Results showed that right-angle fluorescence spectroscopy of honey solutions has great potential for honey botanical origin discrimination, either by visual comparison of excitation-emission spectra landscapes, or even better, by normalized emission fluorescence spectra recordings at 260 and 280 nm of excitation. Moreover, increased honey discrimination was achieved in conjunction with chemometrics of fluorescence spectras. In addition, two rapid markers/indicators of honey authentication were found. Chestnut honey could be clearly discriminated from the other honey types by simple measurement of fluorescence intensity at 390/470 nm, while sage honeys by measurement of reactive amino group content.     

食用氢化油的用途

对食用氢化油在糖果、焙烤食品、煎炸食品、冷饮,仿乳制品、预制产品中的应用进行了综述,并对不同用途的氢油的制备方法作了简单介绍。     

Discriminant Analysis of Selected Edible Fats and Oils and Those in Biscuit Formulation Using FTIR Spectroscopy

Recently, lard adulteration has highlighted the importance of checking raw materials and food products in order to assure their authenticity. Discriminant analysis (DA) using selected frequency regions (3,050?C2,800, 1,800?C1,600, and 1,500?C650 cm^?1) was exploited for the classification of lard and other commercial vegetable oils and animal fats. As a result, the Cooman plot showed that all vegetable fats/oils and animal fats, including lard, are clustered in a distinct group. DA was also employed to assign real food samples, in particular biscuit, into one of two groups. In addition, DA is a very useful means for Halal screening technique in order to enhance the Halal authentication process.     

食品安全管理体系HACCP及其在食用植物油生产中的应用

主要研究了HACCP体系的原则和实施步骤，着重讨论了危害分析和关键控制点，并以食用植物油的生产为例说明了如何进行危害分析和关键控制点的确定，可为油脂企业制定HACCP计划提供借鉴。     

Comparison of Oxidative Stability among Edible Oils under Continuous Frying Conditions

The stability of camellia oil (saturated fatty acid: monounsaturated fatty acid: polyunsaturated fatty acid = 1:7:1) after frying potatoes was compared with palm oil (saturated fatty acid: monounsaturated fatty acid: polyunsaturated fatty acid = 4:4:1) and peanut oil (saturated fatty acid: monounsaturated fatty acid: polyunsaturated fatty acid = 2:4:4). Oil samples were evaluated for acid value, iodine value, peroxide value, p-anisidine value, total oxidation value, tocopherols content, and fatty acids composition. There was the least change in fatty acid composition in camellia oil among the three edible oils. The α-tocopherol was more vulnerable to heat degradation than γ-tocopherol and δ-tocopherol, and α-tocopherol was completely degraded before the whole frying process was done for palm and peanut oils. The oxidative stabilities of the three edible oils were in the order of camellia oil > palm oil > peanut oil. The oxidative stability was mainly determined by the calculated oxidizability value related to fatty acid composition, and when calculated oxidizability values were similar, the tocopherol contents of edible oils would be a key factor in affecting their oxidative stabilities.     

Simultaneous Determination of Danofloxacin and Flumequine in Milk Based on Fluorescence Spectroscopy and Chemometrics Tools

The aim of this paper was to develop a rapid screening method to determine danofloxacin (DANO) and flumequine (FLU) in milk by fluorescence spectroscopy combined with three different chemometric tools. In this study, 2-D fluorescence data and multivariate calibration based on a partial least squares discriminant analysis (PLS-DA) regression were combined to simultaneously qualify and quantify DANO and FLU concentrations in commercial ultra-high-temperature (UHT) sterilized and pasteurized milk. Calibration sets based on the UHT whole milk from brand A were built and performed using a partial least squares (PLS) regression after deproteinization. Prediction sets based on 13 types of milk were analyzed using principal component analysis (PCA), principal PLS-DA, and PLS regression models. The multivariate calibration models were better able to determine the DANO and FLU concentrations than the univariate models, and these models could be applied to other types of milk. In contrast to the PLS-DA, which had good sensitivity and specificity, the PCA yielded less satisfactory results. In the quantitative analysis, the recoveries of the two analytes were reasonable and the root mean square error of prediction was within the acceptable range. The relative standard deviations of the predicted DANO and FLU concentrations on the various testing days were 9.2 and 6.2 %, respectively, demonstrating that the analytical method had a good reproducibility.     

几种食用油中脂肪酸含量的测定与分析

利用气相色谱法对牛油、大豆油、葵花籽油、橄榄油、核桃油、杏仁油这6种油的脂肪酸组成及含量进行分析。6种食用油主要的脂肪酸均为棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸;在这5种脂肪酸中,棕榈酸、硬脂酸、油酸含量最高的均为牛油,分别达到25.0%、31.6%、25.0%,亚油酸、亚麻酸含量最高的是大豆油,含量分别达到69.3%和9.75%,各食用油中不饱和脂肪酸的含量分别为62.084%9、3.057%、84.485%、95.524%、97.323%、97.962%;各食用油中不饱和脂肪酸的含量均较高,因而具有较高的营养价值。     

Oxidative Deterioration in Dried Fish Model Systems Assessed by Solid Sample Fluorescence Spectrophotometry

Oxidative deterioration of fish model systems stored at 25°C in the dark was investigated. Peroxide and TBA values and fluorescence intensities of organic solvent extracts did not correlate well with the extent of lipid oxidation determined by oxygen absorption. However, two types of organic solvent-insoluble fluorescences (I: ex. 370 nm, em. 460 nm; II: ex. 450 nm, em. 500 nm) were observed in fish meats by solid sample spectrofluorometry. Fluorescence II showed a high positive correlation with oxygen absorption. Measurement of protein-bound fluorescence could be useful for assessment of oxidative deterioration in freeze-dried fish muscle and other lipid foods.     

食用油脂中矿物油的定性检测方法研究

研究了皂化法、薄层色谱法及棒状薄层色谱-氢火焰离子化检测器(TLC-FID)法检测食用油脂中的矿物油。结果表明:皂化法简便、快捷,最低检测限可达0.5%,但不适用于本身含蜡质的食用油脂(如米糠油、玉米油及葵花油等);薄层色谱法(TLC)同样可对食用油脂中的矿物油进行定性检测,最低检测限可达到0.2%左右,但仍不适用于本身含蜡质的食用油脂;TLC-FID法克服了以上两种方法的缺陷,不仅适用于本身不含蜡质的食用油脂,还可对本身含蜡质的食用油脂进行矿物油的定性检测,不会出现误检,相比之下更具有优越性。     

食用油中植物甾醇测定方法的优化及含量分析

研究了食用油中植物甾醇的检测方法,并将液相色谱法与薄层色谱法、实验室优化的方法进行了比较,结果表明,优化后的方法具有分析速度快、准确性高和精密度好的优点。同时,利用此检测方法,对油脂加工过程中植物甾醇的含量进行了追踪分析,考察了油脂在精炼过程中的甾醇损失情况。另外,还对不同种类植物油的毛油和脱臭馏出物中植物甾醇的组成及含量进行了分析,为将来相关领域开发应用方面的研究提供了参考数据。     

Identification of Geographical Origin of Olive Oil Using Visible and Near-Infrared Spectroscopy Technique Combined with Chemometrics

A novel multivariate calibration method was developed to identify the geographical origin of olive oils using visible and near-infrared spectroscopy (Vis/NIRS) on the wavelength between 325 and 1,075 nm. Direct orthogonal signal correction (DOSC) preprocessing method was performed to reduce the influence of light scattering, background noise, and baseline shift during experiment. An optimization method of genetic algorithms (GAs) was used to select informative variables from the full spectrum, and 37 informative variables were selected for partial least squares (PLS) regression analysis. The prediction results indicated that the developed DOSC-GA-PLS model can be successfully employed to predict geographical origin of olive oils. Moreover, the use of GA simplified and improved the predictive ability of the model. The prediction statistical parameters were correlation coefficient ( R_\textP² R_{\text{P}}^2 ) of 0.987, relative deviation was 0.093, and the recognition ratio was 97%. It was concluded that Vis/NIRS combined with DOSC-GA-PLS method can be successfully used to determine the geographical origin of olive oils accurately and quickly.     

近红外光谱技术在粮油检测中的应用

分析了近红外光谱技术的工作原理和技术特点,着重介绍近年来近红外光谱技术在粮油品质分析中的应用,并分析了该技术的发展趋势及应用前景。     

膜分离技术在食用油脱胶及溶剂回收中的应用

为解决传统的混合油浓缩和溶剂回收能耗高的问题,探索了膜分离法在混合油脱胶及溶剂回收中的应用,并考察了操作压力和质量比对膜分离过程的影响.采用截留分子量5 000的PES5超滤膜脱除混合油中的磷脂,在0.3MPa下操作,磷脂截留率为63.5%,膜渗透通量达到40.74 L/m2·h.采用ADNF-4040纳滤膜回收混合油中的正己烷,其最大截留率为81%,对应的渗透通量为0.2L/m2·h.     

食用油中甘油三酯聚合物含量测定

氧化甘油三酯和甘油三酯聚合物含量同油脂氧化程度相关联,结合极性组分分离技术和高效体积排阻色谱技术,建立了食用油中甘油三酯聚合物含量测定方法,对天津市常见42种食用油中氧化甘油三酯和甘油三酯聚合物含量进行了测定,结果显示虽然甘油三酯聚合物平均含量接近(1.43%~1.85%),但不同类食用油中甘油三酯二聚物与寡聚物含量比相差较大,以此为基础通过进一步优化方法和扩大样品数据量,所建立的深度氧化劣质食用油鉴别方法,将具有良好的应用前景。     

食用油脂中的反式脂肪酸

综述了反式脂肪酸的定义、主要的来源、分析检测方法以及反式酸对人体的危害以及在油脂加工中降低反式酸的措施     

近20年食用油中掺假的鉴别和分析方法的进展

本文评述了国内外近２０年来对食用油掺假检测方法的进展，这些方法主要是薄层色谱，气相色谱，高效液相色谱，同时论述了其它一些方法。     

Correlation of Sensory Evaluation and Instrumental Gas Chromatographic Analysis of Edible Oils

Soybean oil, hydrogenated soybean oil, and corn oil were exposed to light for various periods of time to obtain a wide range of flavor qualities. The flavor qualities of these oils were evaluated by sensory analysis and instrumental gas chromatographic analysis. The results of the correlation coefficients (r) of flavor scores between the sensory evaluation and the instrumental analysis for soybean oil, hydrogenated soybean oil, and corn oil were 0.99, 0.98, and 0.95, respectively. Therefore, the instrumental analysis can be used to determine the flavor qualities of different oils.     

食用植物油脂肪酸的高分辨气相色谱分析

提出用一种经过改进的方法制备食用植物油的脂肪酸甲酯衍生物，并利用高分辨率毛细管柱分析其中脂肪酸的组成和含量。在确定的气相色谱操作条件下，所用的毛细管柱不仅能够测定食用植物油中的主要成分，而且可测得花生油中含量低至10mg／L数量级的痕量芥酸成分。     

Application of Headspace Solid-Phase Microextraction and Multivariate Analysis for the Differentiation Between Edible Oils and Waste Cooking Oil

Waste cooking oil (WCO) can be recovered and processed into animal feed additives and bio-oils after purification. Unfortunately, edible oils (EOs) were adulterated with refining and purificating WCO, especially in China. Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) analysis has been applied for the determination of the characteristic volatile profile of pure EOs (sunflower oil, rapeseed oil, and olive oil), WCO, and their mixture. Coupling the HS-SPME/GC-MS analysis data with multivariate analysis (MVA) techniques, such as principal components analysis (PCA) and cluster analysis, it has been possible to classify EOs and WCO on the basis of different volatile compounds. Fresh EOs were characterized by a low number of volatile compounds, while WCO and its mixture are characterized by a prevalence of hexanal, (E)-2-heptenal, hexanoic acid, (E,E)-2,4-decadienal, p-allylanisole esdragol, dihydroanethole, anethole, eugenol, and curcumene. PCA showed similarities in clustering of the data obtained by GC-MS. MVA facilitates comparison of chromatographic profiles of volatile compounds characteristic for various EOs, WCO, and the different oil mixture for monitoring oil quality. MVA has been successfully applied to the analysis of adulterated EOs by the addition of cheaper WCO.