Anthocyanins stability during processing

Compared with anthocyanins, the information available on stability of flavonols, flavanols and phenolic acids is limited. As these compounds until recently had only minor interests as food components, investigations were mostly performed for the purpose of biological screening and identification, less for studying stability during processing and storage. However, the mere definition of flavonoids and phenolic acids as antioxidants indicates that the compounds react easily and should be handled as unstable compounds. 

The stability of anthocyanins may be viewed from the perspective of their importance as endogenous components of berry fruits and their products. In addition, a number of anthocyanin extracts are used as food colorants and may be added to various products at different stages during food processing. Several reviews of anthocyanin stability have been published over the years (Markakis, 1982 Jackman et al., 1987a Henry, 1996 Jackman and Smith, 1996 Wrolstad, 2000). 

The fermentation usually is complete within 30 or 40 days. During this period additional anthocyanins are extracted from pomace and the color stabilizes due to polymerization between the anthocyanins and tannins. Winemakers call this process pomace "maturation". Moreover, due to the increasing alcohol concentration, many other metabolites are extracted from the pomace. In addition, yeast metabolites contribute to the aromatic complexity of the wine. 

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