Luis Cabrita

Colour and stability of pure anthocyanins influenced by pH including the alkaline region

This study on anthocyanin colour variation (intensity, λmax, e) over the pH range 1–9 during 60 days of storage, was conducted on petunidin 3-[6-O-(4-O-E-p-coumaroyl-O-α-l-rhamnopyranosyl)-β-d-glucopyranoside]-5-O-β-d-glucopyranoside (petanin) and cyanidin 3-O-β-d-glucopyranoside (cy3glc) at 10 and 23°C. Compared to cy3glc, petanin afforded higher colour intensity and higher or similar stability throughout the whole pH range. At pH 4.0, 84% of petanin was intact after 60 days storage at 10°C, while the corresponding solution of cy3glc was totally degraded. At pH 8.1 the colour intensity of petanin was even higher than at the lowest pH values. The visible λmax absorption of petanin after 5 days at pH 8.1 at 10°C was similar or higher than the corresponding absorptions of the fresh solutions of cy3glc at any pH. The use of anthocyanins like petanin as food colorants in slightly alkaline products (bakery, milk, egg, etc.) should therefore be considered—at least in products with limited storage time kept in a refrigerator..

Colour and stability of the six common anthocyanidin 3-glucosides in aqueous solutions

Abstract This study on anthocyanin stability and colour variation ( λ max , e ) in the pH range 1–12 during a period of 60 days storage at 10 and 23°C, was conducted on the 3-glucosides of the six common anthocyanidins. It was mostly in the alkaline region that differences in colour and stability became significant. Although it has been generally accepted that anthocyanins are stable only at low pH values, this study revealed that, for some of the anthocyanin 3-glucosides (e.g. malvidin 3-glucoside), the bluish colours were rather intense and stability relatively high in the alkaline region. Thus, they can be regarded as potential colorants for some slightly alkaline food products.

Anthocyanins in blue berries of Vaccinium padifolium

Abstract Twenty anthocyanins were isolated from the extract of the edible blue berries of Vaccinium padifolium (Uveira) by a combination of chromatographic techniques. Mainly on the basis of nuclear magnetic resonance techniques ( 1 H, COSY, TOCSY, HSQC, HMBC, SEFT) they were identified as the 3- O -β - glucopyranosides, 3- O -β-galactopyranosides, 3- O -β-arabinopyranosides and 3- O -sambubiosides (2″- O -β-xylopyranosyl- O -β-glucopyranosides) of delphinidin, cyanidin, petunidin, malvidin and peonidin. Anthocyanidin disaccharides have not been identified in the genus Vaccinium previously, and the 3-sambubiosides of peonidin, petunidin and malvidin are novel compounds.

Anthocyanin trisaccharides in blue berries of Vaccinium padifolium

Delphinidin 3-O-a-rhamnoside, malvidin 3-O-(6 00 -O-a-rhamnopyranosyl-b-glucopyranoside) and the 3-O-(6 00 -O-a-rhamnopyranosyl-2 00 -O-b-xylopyranosyl-b-glucopyranosides) of cyanidin, petunidin and peonidin were isolated by various chromatographic techniques from the edible berries of Vaccinium padifolium. Their complete structures were elucidated mainly by one- and twodimensional nuclear magnetic resonance spectroscopy. Together they account for 7% of the anthocyanin content in this species. No anthocyanidin 3-triglycoside, 3-rutinoside or 3-rhamnoside had previously been found in the genus Vaccinium. The 3-O-(6 00 -O-arhamnopyranosyl-2 00 -O-b-xylopyranosyl-b-glucopyranosides) of petunidin and peonidin are novel compounds. # 2000 Elsevier