Copigmentation reactions and color stability of berry anthocyanins

Anthocyanin colors and factors which stabilize and enhance these labile pigments were studied in this thesis. Berry anthocyanin colors were successfully improved by phenolic acid and natural plant extract addition. The results obtained contribute to the understanding of the chemical behavior of anthocyanins. The color quality of black currant wine was improved by the addition of crowberry juice and grape skin extract. Crowberry juice enhanced the color of black currant wine and grape skin extract stabilized it. The total anthocyanin content decreased in all of the berry wines during storage. However, the decline of color intensity was not as severe as the decline in anthocyanin content, which is an indication of copigmentation reactions taking place during fermentation and storage of the black currant wines. Strawberry and raspberry juices were enhanced by the addition of plant extracts (black carrot extract, grape skin extract, and rosemary extract). The commercial color enhancers immediately increased the color intensity of these juices. During storage the improved colors were not very stable. The changes in color intensity and λmax of the pure solutions and berry juices and wine were monitored by spectrophotometer. The effect of phenolic acids on strawberry, raspberry, lingonberry, and cranberry juices was investigated. The phenolic acid enrichment improved and stabilized the juice colors during storage, which was manifested through changes in CIElab parameters and by hyperchromic effect and bathochromic shift detected by spectrophotometer. The simple cinnamic acids, sinapic and ferulic acids enhanced the color of strawberry and raspberry juices the most. The conjugated cinnamic acid, rosmarinic acid, improved and stabilized the color of lingonberry and cranberry juices the most. Novel anthocyanin derivatives formed between the simple cinnamic acids and juice anthocyanins during storage, which was detected first as new peaks in high-performance liquid chromatography (HPLC) chromatogram, and later identified as pyranoanthocyanins by liquid chromatography mass-spectrometry (LC-MS). The new anthocyanin derivatives were 4-vinylguaiacol and 4-vinylsyringol adducts of pelargonidin and cyanidin. This was the first time pelargonidin 3-glucoside based vinylphenol pyranoanthocyanins and pyranoanthocyanin with more complex glycosyl residues were found. For the first time, pyranoanthocyanins were detected in strawberry and raspberry juices. Reactions of pure anthocyanins with phenolic acids were studied for 6 months. Immediate intermolecular copigmentation was observed with the monoglucosidic anthocyanins, expressed as hyperchromic effect and bathochromic shift. The strongest color enhancement on the day of preparation was observed with rosmarinic acid and ferulic acid. During storage, ferulic and caffeic acids improved the monoglucosidic anthocyanin colors the most. The color enhanced by rosmarinic acid was not very stabile in the course of time. The trisaccharidic and acylated trisaccharidic cyanidin did not exhibit color enhancement, although they had the best color stability as such during storage.