Determining Anti-Oxidant Levels in Foods


Determining Anti-Oxidant Levels in Foods


  25/01/2019 10:51:49

Anthocyanins are a class of antioxidants which are common in red and purple fruits and vegetables.  QIB Extra has extensive knowledge of this class of compounds and have determined the anthocyanin profiles in several foodstuffs including purple sweet potatoes, black carrots and elderberry.  
 
Determination is carried out on a powdered sample.  A simple acidic solvent extraction is efficient at removing the anthocyanins which are passed for analysis by ultra-performance liquid chromatography with diode array and mass spectrometric detection. Monitoring the chromatographic eluent at 520 nm elicits a global response for the purple coloured compounds and the mass spectrometer is used to identify which type of anthocyanin species is present.
 
Six anthocyanin aglycone types make up the backbone of all anthocyanins (cyanidin, delphinidin, pelargonidin, petunidin, peonidin and malvidin).  Glycosylation or acylation at specific sites on the anthocyanin molecule then allow for a wide variety of possible derivatives depending on what type of acidic or sugar group is associated. This can result in hundreds of possible anthocyanin molecules.  For example, for the aglycone cyanidin, a commonly found anthocyanin is cyanidin-3-O-glucoside (C3G).  So where a chromatographic peak at 520 nm is found, the mass spectrometer can then look for the common aglycone backbone and also, by its total mass, what derivative it can be. For C3G, the molecular weight is known to be 449 Da and the corresponding cyanidin backbone is 287 Da.
 
For profiling foodstuffs, the overall anthocyanin content is given by the 520 nm response compared to a known standard.  The identity of the anthocyanin from mass spectrometry relies on a growing library of known masses for derivatives compared to their associated aglycone backbone. A single foodstuff can have a varying array of anthocyanins.  For example, one variety of purple sweet potato was determined to have 13 anthocyanin derivatives. 
 
If you have a product that you would like testing for anthocyanin levels or would like to speak to one of our experts please contact the QIB Extra office on either +44 (0) 1603 255342 or info@qibextra.co.uk


 

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