25 jun. 2012

Olive Oil NIR/VIS Spectra - 001 (ChemoSpec)

I continue with the practicing with ChemSpec, and this time I import seven spectra of olive oil. This time I have been more careful and I have the frequency column as numeric form the CSV file. Once I have the spectra (with and offset):
Take in account the comment form Bryan in the previous post when importing CSV files into ChemSpec.

 I want to go into some details in this post about the visible part of the spectra. So let´s select just this part of the spectra:
plotSpectra(olive, title = "olive oil", which = 1:7,
xlim = c(400,800),yrange = c(0.5,3),offset = 0.3)

Here we can see the bands for the carotenoids (3 peaks in the range between 40-500 nm) and  the band for the chlorophyll  which shifts between 650 and 700 nm. These bands can be change, depending of many circumstances (starting from the quality of the extraction process),  and affects obviously the color of the oil.
These bands change during the oil storage depending of the light conditions and disappear when the oil is refined.

2 comentarios:

  1. How do you know that your olive oil sample is olive oil, not a counterfeit product?

  2. In this case I have scanned the sample provided by a company who had analyzed this samples by chromatography, so I put thye sample into a olive oil data set. But the question can be now: What quality has this olive oil sample?. It is a “lampante” , “Virgin”, …….?. Or it is adulterated with other oils, in a small or higher proportion.
    We need a lot of information to classify an olive oil sample (acidity, peroxides, waxes, erithrodiol-uvaol,…..
    Apart from that there are the organoleptic characteristics, very special for the olive oil.
    I will include more posts about this matter where spectroscopy can be a good help for classification, quantification for some fatty acids, acidity, peroxides,…
    In some cases looking to the positions of the bands we can see if the oil could be adulterated, but in many cases is not an easy task, and requires a lot of information.
    Olive Oil is classified according certain limits for a lot of constituents.