Process monitoring and analysis of edible oils

edible oils
Keit IRmadillo FTIR Spectrometer

Fats, fatty acids and other elements in edible oils are essential components to track in the manufacture of food products.  Nutritional value, freshness, safety and flavour can all be affected by changes in these elements during manufacturing.

In situ process analytical technology (PAT) of chemical reactions is one of the most powerful tools in modern science to support industry. Spectroscopy-based PAT represents a very real route to saving money by allowing real-time prediction of concentrations of key chemicals and species within chemical processes.

A Solid-State FTIR (mid-infrared) Spectrometer: The IRmadillo

The Keit IRmadillo is a rugged, vibration-resistant FTIR (mid-Infrared) spectrometer designed for the continuous process environment.  As an in situ instrument, it enables real-time analysis of liquids and slurries for better monitoring and control of the manufacturing process.

  • Direct observation of oil degradation
  • Ability to detect blends of oils
  • Monitor the production and consumption of intermediates and check for contamination

Spectroscopic PAT techniques (such as Raman, FTIR and NIR) are potentially incredibly powerful as they directly monitor different species simultaneously, and can cope with a range of concentrations. However, conventional spectroscopic techniques can suffer from fragility (in the case of standard FTIR instruments), low sensitivity and specificity (in the case of NIR instruments) and poor repeatability and performance drift (in the case of Raman).  Non-spectroscopic techniques such as HPLC and GC have other challenges such as expense, time, knowledge and scope. We believe the IRmadillo FTIR provides the greatest advantage over all these other conventional techniques.

Thermal Degradation Analysis of Edible Oil

Frying cycles within industrial operations involve oil being frequently reused and reheated at elevated temperatures. Unlike with home frying, the quality of these edible fats is significantly reduced, due to decomposition products forming in deteriorated oil.

The cycling at high temperatures combined with oxygen exposure and presence of water, degrade both the oil and food components, reducing acceptability and nutritive value of food.  At frying temperatures, major chemical reactions occur, and this reduces the stability of the frying oil, impacting safety, flavour and stability of fried food.  The IRmadillo provides insight into these chemical changes.

FTIR and Analysing Oxidation

Oxidation is the main reaction in the degradation of lipids. With the risk of reduced acceptability and nutritive value of fried food, it is essential to know the composition of fatty acids in edible oil. Traditional methods of analysis (HPLC, GC, UV-Vis) do not provide the possibility to couple with any automatic control element for process control. NIR has its own limitations on spectral range, model transferability and spectral drift.

FTIR spectroscopy is a rapid and reliable technique that could precisely determine edible oil stability during processing and storage without the use of reagents and solvents. Real-time analysis with the IRmadillo FTIR spectrometer combined with chemometrics has the potential to provide a rapid screening method to monitor lipid quality and process control, as it can successfully characterise thermal degradation of edible oils.

Figure 1: FTIR spectra of thermally degraded edible oil as recorded by the IRmadillo Spectrometer with 120 s sampling time between 900 to 2000 cm-1. The arrows show key peaks and intensities.

Detection of Adulteration in Edible Oil

Cooking oil, particularly olive oil, can be adulterated with less expensive seed oil. Extra virgin olive oil contains the most health benefits due to its high nutritional value. It can be adulterated with refined oils or less expensive oils, such as Rapeseed Oil (Canola Oil) and Soybean (Soya) Oil, for financial gain.

It is one of the most commonly adulterated food products, due to its low production and higher prices. Oils are composed mainly of triacylglycerols (derived from the esterification of three fatty acid molecules with a glycerol molecule). All oils contain a different composition of fatty acids, this means that when the IRmadillo FTIR spectrometer is combined with chemometrics, these Olive Oil adulterants can be differentiated.

oil adulteration

Figure 2: Plot of predicted vs actual values of extra virgin olive oil adulterants. Combing the IRmadillo spectrometer with chemometrics has shown to be effective in identifying extra virgin olive oil as being distinct from different types of seed oil, and when adulterated. This system is also effective in differentiating between different types of seed oils, and can be utilised in analysis of contaminants, impurities and adulteration.

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