A short intro to FTIR analysis

23. Oct, 2018
By Richard Mills
This powerful analytical technology is well worth knowing about, particularly if you are interested in testing liquid food and agri samples such as milk and wine

Fourier Transform Infrared (FTIR) is well worth knowing about, particularly if you are interested in testing liquid food and agri samples such as milk and wine. Let’s get the basics out of the way first and then take a look at the many interesting applications for this versatile method. 


FTIR analysis:the essentials
Fourier Transform Infrared (FTIR) analysis is a spectroscopic technique that makes use of the naturally occurring electromagnetic spectrum. Specifically, the wavelengths between 2,500 nanometers (nm) and 25,000 nm are used. This is the ‘mid-infrared’ region and this is why FTIR is also sometimes referred to as Mid IR.  Generally though, it is the name of a mathematical technique used to convert measurement data into a usable result (Fourier Transform) that is popular, hence, Fourier Transform Infrared, or FTIR for short. 


The Fourier Transform was first developed by the French mathematician Jean Baptiste Joseph Fourier (1768–1830). He would no-doubt be delighted to know that his work is still being put to good use in concert with the latest developments in analytical technology today. Fourier is also credited with the discovery of the greenhouse effect, long before anyone had thought about CO2 emissions. 


FTIR analysis works as follows: 

  • Light from a broad-band light source containing the full spectrum of wavelengths to be measured is shone through a device called an interferometer
  • The interferometer modifies the light in a special way to allow for subsequent processing of the data 
  • The beam is passed through the sample where a sample-dependent absorption takes place
  • The light is detected and passed to a computer
  • The computer processes all the data to infer what the absorption is at each wavelength and generates a spectrum corresponding to the data using the Fourier Transform technique

The mid infrared spectrum 2500 nm – 25000 nm is broad in comparison to, for example, near infrared (800 – 2500 nm). Because the spectrums generated by an FTIR analyser are based on many data points, it provides a highly accurate spectral representation of the sample under analysis. In fact, the accuracy and repeatability of results is often at least as good, if not better, than traditional chemical analysis. At the same time, measurements take less than a minute and are chemical free. Tradition and technology: intelligent applications for FTIR technology


The dairy industry was the first to benefit from the convenience and speed of FTIR analysis through pioneering FOSS solutions introduced in the 1980’s. Today, FTIR analysis in the form of analysers such as the MilkoScan FT1 is invaluable as a rapid way to test milk and dairy products for parameters such as fat and protein. 


A case in point is in cheese production where maintaining a steady level of fat and protein in the milk helps cheesemakers to follow age-old recipes and produce consistent high quality products. 
FTIR analysis has also become an important tool for winemakers ever since FOSS introduced FTIR analysis to the industry in 1999 with the WineScan analyser. It is not that winemakers could not make high quality wine before, but now they can do it more consistently with objective data available to cross-reference their instincts and judgement. 


By exploiting the broad mid-infrared spectrum FTIR analysis can collect a lot of data simultaneously with many parameters measured in a single test typically taking just a few seconds. Over 20 parameters of wine and grape must can be tested in a minute or so with the WineScan including Ethanol, Glucose/Fructose, Malic Acid, Volatile Acid, Total Acid, pH to name a few. The sensitivity of FTIR has also made it useful for measuring parameters with low concentrations, for example, the phenolic compounds in grapes that contribute to the colour and flavour of wine. 

Raw Milk spectrum

FTIR analysis units can be used to screen for abnormalities, for example, in a sample of milk to check if it has been accidentilly contaminated with cleansing fluids. 


Catching unwanted things in milk
Another strength of FTIR analysis is that analysis units can be programmed to screen for abnormalities in a sample, in milk, for example, to check if it has been contaminated with traces of cleaning fluids. The screening is done at the same time as the compositional measurements are performed and no extra equipment or time is required.


It works by testing a sample of milk against a profile for normal milk. Natural raw milk has a particular infrared spectrum – a unique fingerprint. Using FTIR analysis, it is possible to program an analyser to recognise the spectra (or fingerprint) representing pure raw milk. A warning is then given if there is a mismatch. This alerts the user to the need for further testing to determine the nature of the abnormality.

The screening concept introduces a new and convenient testing option for routine milk testing, for example, to screen milk samples for a broad variety of abnormalities at the same time as routine compositional tests are performed. 


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