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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.

This Bulletin describes potentiometric titration methods for the determination of the acidity in milk and yoghurt according to DIN 10316, ISO/TS 11869, IDF/RM 150, ISO 6091 and IDF 86, the chloride content in milk, butter and cheese according to EN ISO 5943, IDF 88, ISO 15648, IDF 179, ISO 21422, and IDF 242. Additionally the determination of the sodium content in milk using the thermometric titration is described. The determination of the oxidation stability of butter in accordance to AOCS Cd 12b-92, ISO 6886 and GB/T 21121 as well as the determination of lactose in lactose free milk by ion chromatography is also described.For the determination of the pH value in dairy products see Application Bulletin AB-086 and for the determination of calcium and magnesium see Application Bulletin AB-235.

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.

The Rancimat method is an accelerated ageing test. Air is conducted through the sample in the reaction vessel at a constantly increased temperature. The fatty acids are oxidized during this process. Volatile secondary reaction products are formed at the end of the test that are conducted by air flow into a measuring vessel, where they are absorbed by a measuring solution (distilled water). The continually recorded electrical conductivity increases as a result of the absorption of the ionic reaction products. The time up to which the secondary reaction products arise is called the induction time. It characterizes the oxidation stability of oils and fats.This Application Bulletin provides a detailed description of the method, in particular also of the required sample preparation.

This Application Bulletin describes the determination of the thermostability of PVC in accordance with ISO 182 Part 3 using the dehydrochlorination method with the 895 Professional PVC Thermomat. The instrument permits fully automatic determination of the stability time. The test is suitable for monitoring the manufacture and processing of PVC products manufactured in the injection molding process, for their final clearance, characterization and for the comparison of PVC products and for testing the effectiveness of heat stabilizers.

The effectiveness of antioxidants can be expressed as antioxidant activity. It can be readily determined using the Rancimat method. This is accomplished by first determining the induction time of a mixture made up of hog fat and the antioxidant to be investigated and then by determining the corresponding time for hog fat alone. The quotient expresses the efficiency of the respective antioxidant and is referred to as the antioxidant activity index (AAI).This Application describes the determination of the antioxidant activity index of five common antioxidants.

Determination of the oxidation stability of foods with a low fat content is a challenge. As an alternative, the oxidation stability can be specified indirectly. To accomplish this, a determination is made as to the extent that a sample that has been mixed with a fat as a standard solution, e.g., hog fat, will change the oxidation stability of that standard solution. This is accomplished by first determining the induction time of the mixture made up of hog fat and the sample and then by determining the corresponding time for the lard alone. The quotient is referred to as the stability index (SI).

The oxidation stability of fats and oils is an important parameter for quality controls in the food industry. Ideally, the determination is made with the Rancimat method, which is suitable for both liquid and solid samples. Its determination takes place directly in the sample or, in cases where this is not possible, in the extracted fat following cold extraction.

The thermostability of polyvinyl chloride (PVC) was determined using the dehydrochlorination procedure at 180 °C. Comparison of the thermostability of pure PVC polymer, blended PVC (blended with stabilizer, plasticizer, filler) and blended PVC after processing.

In this Application Note, the 893 Professional Biodiesel Rancimat measures the oxidation stability of biodiesel (or fatty acid methyl esters, FAME), an eco-friendly fuel.

The oxidation stability of biodegradable lubricating oil is determined using the Rancimat method.

Instant noodles have become very popular in many parts of the world. During the production process instant noodles are deep-fried, which enables a quick preparation for the consumer. Due to their high fat content (up to 22%), instant noodles can get rancid. The 892 Professional Rancimat can be used to determine the oxidation stability of deep-fried instant noodles without prior fat extraction.

The 892 Professional Rancimat can be used for determining the oxidation stability of fats contained in solid, non-meltable foodstuffs, such as peanuts, almonds, potato chips (crackers), cookies and french fries. The crushed samples can be used directly without extraction of the fat.

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.

Using the Rancimat method, the oxidation stability of suntan oil can be determined reproducibly and reliably.

Determination of the thermostability of polyvinyl chloride (PVC) using the dehydrochlorination procedure at 200 °C.

Wax has theoretically an unlimited shelf life, however many additives (flavor, softener, etc.) can affect it negatively. Since both synthetic and natural waxes are used in various products, such as cosmetics and foods, expiry dates have to be specified. The oxidation stability can give an approximate indication for the shelf life. A reproducible and accurate determination of the oxidation stability using the 892 Professional Rancimat can be realized.

Motor oils are exposed to high shear forces and temperatures while the motor is running. Mechanical abrasions set iron and copper free, which act as catalysts for oxidation. All of this decreases the durability of motor oils. The oxidation stability with iron and copper catalysts can give an approximate indication for the shelf life. A reproducible and accurate determination of the oxidation stability using the 892 Professional Rancimat can be realized.

Lipsticks and lip balms consist mainly of natural oils such as seed oils, palm oils or coconut oils. Many manufacturers additionally enhance their product with various vegetable fats, oils and wax. The purpose of these additives is to increase the perceived quality of the products. However, some of these oils and fats are capable to oxidize by autoxidation over time which affects the shelf life and therefore the quality of the products negatively. A reproducible and accurate determination of the oxidation stability using the 892 Professional Rancimat can be realized.Find the method explained in the Metrohm LabCast video at https://youtu.be/xdOmyeyc7Cs

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 oxidation stability is an important factor for the quality of cosmetics. It also provides information about the long-term and storage stability of the product. Most cosmetic formulations 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.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. In this Application Notes the oxidation stability of body care cream, moisturizer, body milk, body lotion, and toothpaste is determined in this way. More information on the Rancimat method can be found on the Metrohm website.

Oxidation stability is an important quality criterion of chocolate as it provides information about the long-term stability of the product. Cocoa contains various flavonoids that act as antioxidants. The most important and common flavonoids are catechin, epicatechin, and procyanidin. Although the flavonoid content may vary amongst chocolate type, it can be said, the greater the cocoa content in the chocolate, the greater the antioxidant effect.Chocolate cannot be measured directly with the classical Rancimat method, as no evaluable induction time is obtained. There are many reasons for this, for example a too low fat content or various matrix effects. Traditionally, extraction of the fat from the chocolate using e.g., petroleum ether is therefore necessary.In this Application Note, the oxidation stability of white, milk and dark chocolate with varying cacao content is determined in without extraction. Instead, polyethylene glycol is used as conducting medium. More information on the Rancimat method can be found on the Metrohm website.

Oxidation stability is an important parameter to assess the quality of animal feed. It provides information about the long-term resistance to degradation of the fatty acids, which can predict the storage stability of the product. Oxidation stability of many animal feeds can be directly and reproducibly measured by the Rancimat method, if polyethylene glycol (PEG) is used as the carrier material.No sample preparation is required for this application. This Application Note describes the determination of oxidation stability of fish food and dog treats. More information on the Rancimat method can be found on the Metrohm website.

Oxidation stability is an important parameter defining the quality of tea. It also provides information about the long-term stability of the naturally included antioxidants and thus the stability of the product. However, tea cannot be measured directly with the Rancimat method, as no evaluable induction time is obtained. The reason for this is that no measurable oxidation product is formed. However, using polyethylene glycol (PEG) as carrier material, many of these samples can be directly and reproducibly measured without any sample preparation. This is due to the antioxidants that are naturally present in the sample matrix, which stabilize the induction time of the PEG. The induction time can therefore be directly related to the oxidation stability of the sample.A reproducible and accurate determination of the oxidation stability is feasible using the 892 Professional Rancimat. In this Application Notes the oxidation stability of different teas is determined in this way. More information on the Rancimat method can be found on the Metrohm website.

The freshness as well as the smell and taste of coffee depend, among other things, on the content of antioxidants. The antioxidant content is critical to set a retail price and therefore it is of great interest for manufacturers and distributors to determine it. Classically, this parameter is determined via long-term storage tests. Oxidation stability offers a fast, alternative method, which can define the quality of coffee.Using the modified Rancimat method, the oxidation stability of coffee can be determined quickly and reliably. The sample is analyzed together with polyethylene glycol (PEG). The antioxidants present in the sample matrix stabilize the induction time of the PEG. The induction time can therefore be related directly to the oxidation stability and antioxidant content of the sample.This Application Note demonstrates the feasibility of the modified Rancimat method. Using the 892 Professional Rancimat, reproducible and accurate determination of the oxidation stability of different coffees is possible.

The thermal stability of raw or processed PVC provides information about the quality of the plastic. Higher stability times can be correlated with longer lifespans. With the 895 Thermomat, the dehydrochlorination rate at elevated temperatures can be determined within a short time. Additionally, quality deviations in the purchased raw material as well as in the end products can be detected. The 895 Thermomat has been optimized for this application regarding three important points: safety, handling, and time-savings. The measurement is based on the standard EN ISO 182-3.

The determination of the oxidation stability of wine with the Rancimat is a newly developed method able to determine the antioxidant potential of wines. Different grapes as well as varied processing methods impart the color, taste, and anti-oxidative capacity for each wine blend or varietal. With the Rancimat and Polyethylene Glycol (PEG) methods, the antioxidant potential in different wines can be easily compared.The PEG method is used to compare the antioxidant capacity of different vintages and grape varieties. The induction time can be used as a quality criterion for different types of wine or different vintages. In this Application Note, the oxidation stability of different wines is determined in this way.

This Application Note demonstrates the feasibility of the Rancimat method. Reproducible and accurate determination of the oxidation stability of flavored spirits is possible with the 892 Professional Rancimat.

Determining the oxidation stability of raw materials for the cosmetic and pharmaceutical industry.

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.

This Application Note describes the determination of the oxidation stability of different sausages with the recommended method from Metrohm using an 892 Professional Rancimat.

This Application Note describes the determination of the oxidation stability of the fat in different sausages extracted with cold petroleum ether using an 892 Professional Rancimat.

Higher antioxidant levels mean longer product viability. The 892 Professional Rancimat determines antioxidant content in many products using a linear regression method.

Sustainable biodiesel can be blended with petroleum diesel. The 893 Professional Biodiesel Rancimat measures the oxidation stability of biodiesel and its blends.

Rancidity of oils and fats is a factor which can immediately reduce the sale price of these products to customers in the food and cosmetics industries. Oils which remain stable over longer periods of time are more highly valued as they lead to a higher quality end product. Rancidity is a natural process which occurs as fats and oils age and oxidize, and can be delayed or even stopped by addition of antioxidants at the right time.Determination of rancidity is possible in several ways (e.g., measuring the acid number or peroxide value), though these tests only give information about the current state of the product, with no indication about the remaining shelf life. One analytical method that can measure this time span until spoilage is the Rancimat method, which artificially ages the samples to determine whether antioxidants may be needed to help manufacturers get the full value from their oils.