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Edible oils are not only a major source of nutrition but also a key basic material in the food industry. Vegetable oils are increasingly important because of their high content in mono- and polyunsaturated fatty acids in comparison with animal fats. In this application note, the main ingredients of olive oil, camellia oil, arachis oil, sunflower seed oil, and colza oil are analyzed using a portable Raman spectrometer combined with chemometrics software.

The Rancimat method is a widely accepted method for the determination of the oxidation stability of natural fats and oils. Its main application is quality control in oil mills and the oil processing industry. At elevated temperatures and under the exposure of air, fatty acids are oxidized. The reaction products are absorbed in ultrapure water that is continually monitored for conductivity. After an induction period with slow reaction, the formation of volatile carboxylic acids is accelerated. At that time the conductivity begins to increase rapidly. Instead of investing weeks or months, the sample can be oxidized within a few hours.The method can also be used to determine the oxidation stability of solid foodstuffs that contain natural fats or oils. Frequently, a direct determination without extraction of the fat is possible, if the fat content exceeds a minimum level. In these cases, a simple and reliable assessment of the quality of the produced foodstuff is possible.A number of fat-containing solid foodstuffs such as almonds, peanuts, peanut-flavored puffs, potato chips, muffins, butter cookies, French fries, and instant noodles were successfully tested with the Rancimat method. The experiments revealed that the comminution of the sample is one of the most important steps. The grinding procedure of the tested samples was kept as simple as possible to avoid the use of expensive milling instrumentation.

The poster describes the development of an automated Karl Fischer method for determining the water content in different edible oils.

Thermometric titration can solve application problems that potentiometry cannot solve at all, or at least not satisfactorily.

This Application Bulletin gives an overview of the volumetric water content determination according to Karl Fischer. Amongst others, it describes the handling of electrodes, samples, and water standards. The described procedures and parameters comply with the ASTM E203.

Edible oils and fats contain natural tocopherols and, in some cases, also synthetic tocopherols added as antioxidants. The method described below allows the simple and rapid determination of the tocopherol content by voltammetry. The tocopherols are oxidized electrochemically at the glassy carbon electrode (GCE). The limit of quantitation is approximately 5 ppm (mg/kg) tocopherol.

This Application Bulletin gives an overview of the coulometric water content determination according to Karl Fischer. Amongst others, it describes the handling of electrodes, samples, and water standards. The described procedures and parameters comply with the ASTM E1064.

As the determination of the exact content of individual glycerides in fats and oils is difficult and time-consuming, several fat sum parameters or fat indices are used for the characterization and quality control of fats and oils. Fats and oils are not only essential for cooking, they are also an important ingredient in pharmaceuticals and personal care products, such as ointments and creams. Consequently, several norms and standards describe the determination of the most important quality control parameters. This Application Bulletin describes eight important analytical methods for the following fat parameters in edible oils and fats: Determination of water content in accordance with the Karl Fischer method Oxidation stability in accordance with the Rancimat method Iodine value Peroxide value Saponification value Acid value, free fatty acids (FFA) Hydroxyl number Traces of nickel using polarography Special care is taken to avoid chlorinated solvents in these methods. Also, as many of the mentioned methods as possible are automated.

This document outlines Rancimat testing for both liquid and solid food samples, including direct and PEG methods, for oxidation stability QC in the food industry.

In titration, the titrant reacts with the analyte either exothermically (gives off heat) or endothermically (absorbs heat). The Thermoprobe measures the temperature change during titration. When all of the analyte has reacted with the titrant, the temperature of the solution will change, and the endpoint of the titration is indicated by an inflection in the temperature curve. Catalytically enhanced titrations using paraformaldehyde as catalyst are based on the endothermic hydrolysis of the paraformaldehyde in the presence of excess hydroxide ions. Edible oils are dissolved in a mixture of toluene and 2-propanol (1:1) and titrated with standardized TBAH (0.01 mol/L) in 2-propanol to a catalytically enhanced endpoint.

The Rancimat method determines the oxidation stability (OSI) and antioxidant capacity (SI) of solid foods. OSI measurements are performed directly, with extracted isolated fat, or via the polyethylene glycol method. SI can be determined when the sample is mixed with a reference of antioxidant-free fat.

Palm oil is a vegetable oil that is used not only in the food industry but also for the manufacture of soaps and body care products. It is furthermore an important raw material for the generation of biodiesel. Depending on the degree of refinement, palm oil can be red, reddish or even colorless in appearance. The carotenes responsible for the color are removed during refinement and the oil becomes increasingly clear. In this Note, the chlorine and sulfur content of various palm oils are determined using Combustion IC. Keyword: pyrohydrolysis

Determination of free fatty acids (FFA) in oils.

Iodine value (IV) is a measure of the total number of double bonds present in fats and oils. It is expressed as the «number of grams of iodine that will react with the double bonds in 100 grams of fats or oils». The determination is conducted by dissolving a weighed sample in a non-polar solvent such as cyclohexane, then adding glacial acetic acid. The double bonds are reacted with an excess of a solution of iodine monochloride in glacial acetic acid («Wijs solution»). Mercuric ions are added to hasten the reaction. After completion of the reaction, the excess iodine monochloride is decomposed to iodine by the addition of aqueous potassium iodide solution, which is then titrated with standard sodium thiosulfate solution.

The water content of lemongrass oil is determined according to Karl Fischer. To prevent unwanted side reactions, special KF reagents for aldehydes and ketones are used and the determination is carried out at 0 ... 4 °C.

The water content of animal fat extract is determined according to Karl Fischer.

Determination of key quality parameters of palm oil, namely free fatty acids (FFA), iodine value (IV), moisture content, deterioration of bleachability index (DOBI), and carotene require the use of several different analytical methods, which are laborious and can lack in accuracy. This application note demonstrates that the XDS RapidLiquid Analyzer operating in the visible and near infrared spectral region (Vis-NIR) provides a cost-efficient and fast solution for the determination of these quality control parameters in palm oil. With no sample preparation or chemicals needed, Vis-NIR spectroscopy allows for the analysis of palm oil in less than a minute and can be used by anyone.

Near-infrared spectroscopy can quickly determine multiple edible oil quality parameters simultaneously without sample preparation as shown in this Application Note.

Near-infrared spectroscopy (NIRS) quickly assesses key quality parameters in palm oil such as iodine value and fatty acid profile without sample preparation.

Monitoring the iodine value in edible oil blends is crucial to produce vegetable oils with the desired properties. This Application Note displays the benefit of using the Metrohm NIRS DS2500 Liquid Analyzer for quality control in food laboratories.

Near-infrared spectroscopy (NIRS) offers a fast, solvent-free alternative to traditional methods for assessing olive oil quality and detecting potential food fraud.

NIR spectroscopy is an alternative method for olive pomace fat analysis. Unlike other conventional methods, NIRS requires no sample preparation nor chemical solvents.

Quang phổ cận hồng ngoại (NIRS) cho phép kiểm soát chất lượng ô liu nguyên quả một cách nhanh chóng và không phá hủy mẫu, hỗ trợ xác định thời điểm thu hoạch tối ưu cũng như cải thiện độ chính xác trong ước tính sản lượng dầu. NIRS cung cấp khả năng xác định nhanh hàm lượng dầu, độ ẩm và chỉ số độ chín mà không cần sử dụng hóa chất hay chuẩn bị mẫu. Hiệu năng phân tích của phương pháp này tương đương với các kỹ thuật đã được khẳng định như cộng hưởng từ hạt nhân (NMR) và chiết Soxhlet, trong khi thời gian phân tích nhanh hơn đáng kể và việc triển khai tại các nhà máy ép dầu hoặc phòng thí nghiệm kiểm soát chất lượng cũng đơn giản hơn.

Oxidation of sweet almond oil can occur over time, affecting its organoleptic characteristics. This Application Note describes the reproducible and accurate determination of oxidation stability of sweet almond oil using the 892 Professional Rancimat.

Some samples, such as cosmetics and food, cannot be measured directly with the Rancimat as no evaluable induction time is obtained. There are many reasons for this, for example a high water content, a too low fat content or various matrix effects. However, using polyethylene glycol (PEG) as carrier material, many of these samples can be directly and reproducibly measured without sample preparation. This is due to the antioxidants that are naturally present in the sample matrix, and which stabilize the induction time of the PEG. The induction time can therefore be directly related to the oxidation stability of the sample. Furthermore, with a standard addition it is possible to measure the content of antioxidants (AOC) such as vitamin E, vitamin C or an equivalent of it. The decrease of the antioxidants over time (for example, during storage of the sample) can thus be measured and evaluated. In addition, this method eliminates a costly sample preparation. A reproducible and accurate determination of the oxidation stability using the 892 Professional Rancimat can be realized.

The oxidative stability of sunflower oil using AOCS Cd 12b-92, EN ISO 6886, and a method based on EN ISO 6886 from Metrohm are compared. No significant differences are found.

Determination of the identity and purity of ingredients is essential for the product quality of functional foods (neutraceuticals) and cosmetics. It prevents the utilization of inferior substances in the production process and thus avoids expensive delays and out-of-spec products. This Application Note describes the identification and checking of fatty acids in functional foods and cosmetics using the Metrohm Instant Raman Analyzer MIRA P.

Fenthion is a multi-purpose insecticide used in many countries for mosquito control. To minimize human exposure and the unintentional poisoning of wildlife, the US EPA has classified fenthion as a restricted-use insecticide. However, the widespread spraying of olive orchards in Mediterranean countries results in olive oils that occasionally exceed the maximum residue limits established for olives. Misa (Metrohm Instant SERS Analyzer) easily achieves sensitive trace detection of fenthion in spiked olive oil after a simple organic solvent extraction. This Application Note presents an excellent example of how the signal from SERS substrates can compete with the target signal at very low levels of detection.

This Application Note presents a modified time-saving method to determine iodine value (IV) in edible oils based on several standards (EN ISO 3961, ASTM D5554, etc.).

This Application Note details a method to determine the peroxide value of edible fats and oils based on EN ISO 27107, EN ISO 3960, AOAC 965.33, Ph.Eur. 2.5.5, and USP<401>.

The saponification value evaluates edible oil quality by indicating the average molecular weight of fatty acids. Its titrimetric determination in canola and olive oil is described here.

This Application Note describes the titration of acid value and free fatty acids in different edible oils, based on the standards EN ISO 660, USP<401>, and Ph.Eur. 2.5.1.

The hydroxyl number (HN) is an important sum parameter for quantifying the presence of hydroxyl groups in chemicals. As a key quality parameter, it is determined in various substances. For pharmaceutical samples, USP chapter <401> and Ph. Eur. Chapter 2.5.3 describe the determination. However these methods either use toxic pyridine and require refluxing or have long reaction times. In this Application Note, an alternative method according to ASTM E1899 is presented. This method is pyridine-free and does not require refluxing or long reaction times. The determination is performed at room temperature with only a small sample size. The analysis including all preparation steps is performed with a fully automatic OMNIS system. This allows parallel analysis of multiple samples, increasing productivity in the laboratory by 50%.

Determination of Cd, Pb, Cu, Ni, and Co in soybean oil after extraction by boiling with HCl under reflux.

Edible oils comprise a significant portion of any diet, and they also have important roles in the production of foods, cosmetics, and skincare products. For these reasons, a convenient and accurate method for materials identification of a variety of fats and oils is highly desirable. Historically, authentication of fats and oils was performed through intensive laboratory techniques involving chromatographic methods. Here, Raman spectroscopy combined with Principle Component Analysis (PCA) has been used for materials identification with 16 different edible oils, with excellent results. Raman is an ideal technique for evaluation of fats, as carboncarbon double- and single-bonds give strong Raman signals. PCA analysis in combination with Raman spectroscopy is a powerful tool for qualification and verification of different fats and oils, as there are few visual differences between spectra of edible oils.

Chuẩn độ là một trong những phương pháp phân tích được sử dụng phổ biến nhất. Chuẩn độ thủ công, bán tự động và hoàn toàn tự động là những lựa chọn được biết đến rộng rãi và được xem xét chi tiết trong một số nghiên cứu học thuật. Tài liệu này tóm tắt những ưu điểm và lợi ích của chuẩn độ tự động so với chuẩn độ thủ công. Sự gia tăng độ chính xác và độ tin cậy của phép đo cũng như tiết kiệm đáng kể thời gian và chi phí được thảo luận.

This White Paper discusses the concept and benefits of NIR spectroscopy and outlines several real-life laboratory application examples with the use of OMNIS NIRS, the cutting-edge NIR spectrometer from Metrohm.

OMNIS Client/Server nâng cao hiệu suất kinh doanh nhờ khả năng quản lý máy chủ linh hoạt, giúp cắt giảm chi phí thông qua giảm phần cứng, tiêu thụ năng lượng và bảo trì tại nhiều địa điểm.