Monomer index

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The monomer index is a dimensionless number for determining the ratio of monomeric to polymeric anthocyanins in red wine , red fruit juices and fruit juice beverages.

The principle of the measurement is based on the bleaching of monomeric anthocyanins by potassium disulfite in an acidic environment. Polymer anthocyanins, on the other hand, are not discolored due to steric hindrance.

The extinction of the sample solutions without addition of sulfite (total extinction) and the extinction after addition of potassium disulfite (extinction of the polymeric anthocyanins) are determined by means of photometric measurement at 520 nm . The difference between the two measured values ​​represents the extinction of the monomeric anthocyanins. The monomer index is obtained as the quotient of these measured values.

application

Polymeric anthocyanins are formed during storage of wine, fruit juices and concentrates through the polymerisation of monomeric anthocyanins. In addition, polymer anthocyanins have no significant bioavailability compared to monomeric anthocyanins . Therefore, with the help of the monomer index, a simple and fast quality and age check of raw materials and products can be carried out in comparison to complex HPLC methods .

literature

  • D. Bonerz, K. Würth et al: The monomer index: A quick and inexpensive method for the determination of anthocyanin adducts in colored juices, nectars, concentrates and red wines. In: Deutsche Lebensmittel-Rundschau. Volume 102, No. 5, 2006, pp. 195-201.