Anthocyanins degradation

Tsai, P.J., Hsieh, Y.Y., and Huang, T.C., Effect of sugar on anthocyanin degradation and water mobility in a roselle anthocyanin model system using O- NMR, J. Agric. Food Chem., 52, 3097, 2004. 

For many situations, a simple total anthocyanin determination is inappropriate because of interference from polymeric anthocyanins, anthocyanin degradation products, or melanoidins from browning reactions. In those cases, the approach has been to measure the absorbance at two different pH values. The differential method measures the absorbance at two pH valnes and rehes on structural transformations of the anthocyanin chromophore as a function of pH. Anthocyanins switch from a saturated bright red-bluish color at pH 1 to colorless at pH 4.5. Conversely, polymeric anthocyanins and others retain their color at pH 4.5. Thus, measurement of anthocyanin samples at pH 1 and 4.5 can remove the interference of other materials that may show absorbance at the A is-max-... 

Sarni, P. et al.. Mechanisms of anthocyanin degradation in grape must-like model solutions. J. Sci. Food Agric. 69, 385, 1995. 

Romero, C. and Bakker, J., Effect of storage temperature and pyruvate on kinetics of anthocyanin degradation, vitisin A formation and color characteristics of model solution. J. Agric. Food Chem. 48, 2135, 2000. 

The authors have used ratios of ace-tone/chloroform varying from 1 1, 1 2, 1 2.4, to even 1 5. A greater proportion of chloroform reduces the amount of acetone in the aqueous phase and may eliminate the need for removal of acetone by rotary evaporation. This evaporative step, however, takes little time with no apparent anthocyanin degradation. Therefore, the authors favor using 1 1 or 1 2 ratios to avoid excessive use of the chloroform solvent. 

Use a temperature of 30° to 40°C during rotary evaporation to avoid anthocyanin degradation. It is also important to monitor the process to ensure that the aqueous crude extract is not suctioned into the solvent reservoir. If this is going to happen, quickly release the vacuum and transfer the extract to a larger boiling flask and/or reduce the temperature of the water bath. 

Description of the pH differential method for determination of total anthocyanins and indices for anthocyanin degradation as applied to fruit juices and wines. 

Wesche-Ebeling, R Montgomery, M.W. (1990). Strawberry polyphenoloxidase its role in anthocyanin degradation. J. Food Sci., 55, 731-734, 745. 

A detailed study of the effects of pH on anthocyanin stability has been presented by Cabrita et al. (2000). Buffered solutions in the range of pH 1-12 of the 3-glucosides of the six common anthocyanidins were stored in the dark over a 60-day period at 10°C and 23°C. Under strong acidic conditions (pH 1-3), more than 70% of the initial concentration remained after 60 days at 10°C for all anthocyanins, while considerable losses (>90%) occurred at pH 5-6 even after 8 days. Similar stability patterns occurred at the higher temperature of 23°C, although the rates of anthocyanin degradation were higher, and only 40% of the initial anthocyanins were detectable after 60 days. 

It has been known for decades that heat is one of the most destructive factors of anthocyanins in berry fruit juices (Jackman et al., 1987a). With strawberry preserves, it was shown as early as 1953 that the half-life time was 1 h at 100°C, 240 h at 38°C and 1300 h at 20°C. In a storage experiment with concentrates and dry powder of elderberry extracts, the stability increased 6-9 times when the temperature was reduced from 20°C to 4°C (Zajac et al., 1992). Anthocyanin degradation in anthocyanin solutions increased from 30% to 60% after 60 days when storage temperatures were increased from 10°C to 23°C (Cabrita et al., 2000). High-temperature short-time processing is recommended for maximum anthocyanin retention of foods containing anthocyanins (Jackman and Smith, 1996). 

The color of anthocyanins containing media depends on different factors. The most important are structure and concentration of anthocyanin pigments, pH, and presence of copigments and metallic ions, all of which influence the color shade. Also important are the temperature and presence of oxygen, phenoloxidase, ascorbic acid, and sulfur dioxide, all of which influence the anthocyanins degradation rate and color stability. 

Ascorbic acid may have a protective effect with regard to anthocyanins, since it reduces the o-quinones formed before their polymerization. However, ascorbic acid, as well as products of its degradation, increases anthocyanins degradation rate. 

The rate of anthocyanin degradation is greatly affected by pH value. Increasing acidity has a protective effect on the stability of the pigment. Figure 3 shows the relative rate of pigment loss in buffered solutions at various pH values. 

Sami, P., Fulcrand, H., Souillol, V., Souquet, J. M., Cheynier, V. Mechanisms of Anthocyanin Degradation in Grape Must-Like Model Solutions. J. Sci. FoodAgric. 69,385-91,1995. 

Umezawa T (2003) Diversity in lignan biosynthesis. Phytochem Rev 2 371-390 Vaknin H, Bar-Akiva A, Ovadia R, Nissim-Levi A, Forer I, Weiss D, Oren-Shamir M (2005) Active anthocyanin degradation in Brunfelsia calycina (yesterday-today-tomorrow) flowers. Planta 222 19-26... 

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