Why near infrared spectroscopy?

By Dagmar Behmer

The traditional analyses in the edible oil industry are generally carried out using standardised chemical and physical methods sanctioned by the American Oil Chemist Society (AOCS) and/or the association of Official Analytical Chemists (AOAC). Those require Kjeldahl protein analysis, Soxhlet extraction for total oil, oven methods or moisture balance for moisture analysis, gas chromatography (GC) or high performance liquid chromatography (HPLC) for fatty acid composition analysis and glucosinolates, spectrophotometry for colour analysis and many other types of analysis. These methods usually take a long time and result in sample destruction during the analysis process.

The FT-NIR technology offers a lot of advantages over classical wet-chemical and chromatographic analyses, since it is quick, cost-effective and safe, as no hazardous chemicals are used. It simply measures the absorption of near-infrared light of the sample at different wavelengths. FT-NIR also avoids the typical operator depending error sources of the classical lab methods, e.g. during the sample preparation stage. With only one measurement, multiple components can be analysed in less than one minute, saving thousands of euros on traditional reference analysis every month.

Another issue is food safety. Although NIR spectroscopy is not a technology for trace analysis like for toxins, it will help the producer to constantly monitor the quality of the goods along the production chain - from checking the incoming raw materials up to quality testing the finished product.

Analysis

NIR spectroscopy offers solutions for oil producers as well as for breeders. To optimise the oil pressing process, the oil seeds as well as the intermediate products, like expellers or extracts can be analysed for oil and moisture content in order to optimise the pressing parameters. On the other hand, breeders can obtain valuable additional information like fatty acid profiles of their seeds, including Erucic acid as well as the Glucosinolate content for rape seeds or oleic acid content for sunflower seeds.

Quality control

For edible oils and fats a wide number of quality parameters can be analysed with only one measurement. Apart from the fatty acid profile, it is possible to analyse free fatty acid (FFA) content as well as physical parameters like colour parameters. The analysis of Iodine Value (IV) by FT-NIR is today acknowledged by the AOCS (method Cd1e-01) and can substitute the time consuming Wijs method. The determination of the trans fatty acid (TFA) content in an edible oil is important for consumer health. A large amount of trans configurations in the double bonds of an oil has been identified as a risk for coronary heart disease.

Testing

A common problem not only for the olive oil industry is the adulteration of high priced oil with cheaper vegetable oils such as sunflower oil or hazelnut oil. Today's public awareness of the health benefit of olive oil makes the adulteration economically attractive. Since the different oils vary in their fatty acid profile, NIR spectroscopy can offer a valuable tool for determining other types of oil in olive oil down to a low percentage range.

Today, FT-NIR spectroscopy has the potential to substitute a wide range of classical analysis methods in the edible oil industry: it is fast, reliable and cost-efficient. Bruker Optics offers ready-to-use calibrations for edible fats and oils as well as for various oil seeds to enable a quick and efficient start. 

Biography

Dagmar Behmer has an MSc degree in Analytical Chemistry and is Head of International Support in the NIR & Process technology group of Bruker Optics in Germany. She has 20 years of experience with NIR spectroscopy, focusing on food and agricultural applications.