1. Stabilizing anthocyanin loss in foods when ascorbic acid is present
Maria Aguirre
FSTC 605

2. Anthocyanins Phenolic compounds Flavonoids Anthocyanins
Is the major pigment that gives color: blue, purple, violet, magenta, red and orange.
Greek words
Antho=flower
Cyanin=blue
Health properties
Phenolic compounds are composed by a large group of organic substances, and flavonoids are an important subgroup. The flavonoid subgroup contains the anthocyanin’s, one of the most broadly naturally source of colorants including blue, purple, violet, red etc. Anthocyanin comes from two greek words Antho means flower and cyanin means blue. Additionally, it is considered as a functional ingredient due to several anthocyanins have been shown to posses health-promoting properties. On this diagram there are 7 positions labeled R. R basically means that it can be ocupied by almost any organic group like a methal group, sugar, and the number of R that are occupied by a specific substitutions would determine the color of the anthocyanin. .

3. Anthocyanins found in nature
According to research the basic colors blue, purple, red and orange have a direct relation with the number of hydroxyl groups and indirect relation with the number of methoxyl groups. Also, it has been showed that hydroxylation at position 4 changes the colors toward red tones.

4. Economic importance - Synthetic red dyes natural colorants
- Enocyanin and lees preparation approved by FDA
- Beverages and soft drinks
Instability limits their use!
Anthocyanins are of great economic importance as pigments of fruit juices and wines. One of the main claims of the food industry nowadays is for natural colorants to replace synthetic red dyes, and anthocyanins are the principal candidates, however just enocyanin and lees (sediment of the grape juice tanks) preparations are the only anthocyanin sources approved by FDA to be used for human food, while the main use is in the production of beverages and soft drinks. However, anthocyanin instability limits their use, and different preparations have been evaluated to avoid anthocyanin degradation.

5. Anthocyanins Stability
Unstable with
- pH
- oxygen
- Light
- High temperature during cooking, anthocyanins decompose
Most stable
- At low pH (acid)
- Low temperature
Anthocyanins are very sensitive to chemical and environmental factors, such as
pH,
oxygen,
Light,
And It also become less stable when exposed to heat, causing a loss of color and browning. As a result, High temperature, increased sugar level, pH, and ascorbic acid can affect the rate of destruction.
And they are stable at low pH and low temperature.

6. Anthocyanins and pH Color very pH dependent
Flavylium cation prominent <pH 3
In solution, anthocyanins molecules are present in an equilibrium between the colored cationic form and the colorless pseudobase. This equilibrium is directly influenced by pH. pH is very important for the color of anthocyanins, some anthocyanins are red in acid solutions, violet or purple in neutral solutions, and blue in alkaline pH. The reason for this is right here this structure of the anthocyanins (red circle) is called flavylium cation the reason, at low pH the cyanidin molecule is protenated and forms a + ion or a cation, as the pH increases the molecules become deprotenaited, at high pH the molecule forms a negative ion or anion.This is the reason that most colorants containing anthocyanins can only be used at pH values below four. Additionally, anthocyanins can act as pH indicators. ,

7. Grape pomace extract West and Mauer 2013
This is example of how pH and temperature storage affects the color of this compounds, the three columns represent three different storage temperatures, the left column represents refrigerated temperatures, the middle column represents room temperature and the right column represents heated temperatures. At the top of the chart is day 0 storage. The number of storage days increases as the chart moves downward. Within each column the left square represents a pH of 3 and the right square represent a pH of 4. we can see how a pH differences of 1 can have very noticeable effects.
West and Mauer 2013

8. Oxygen
Unsaturated nature susceptible to molecular oxygen (i.e. grape juice).
Effect of oxygen: processing fruit juices under nitrogen or vacuum.
Example: Deoxygenated systems remained color stable up to 10 days, but lost color after few hours in presence of oxygen. presence.
The unsaturated nature of anthocyanins structure makes it susceptible to molecular oxygen. The most common example is the grape juice, when grape juice is hot-filled into bottles, complete filling of the bottles will delay degradation of the color from purple to brown.
The positive effect of oxygen removal on retention of anthocyanin color has been further demonstrated by processing anthocyanin-pigmented fruit juices under nitrogen or vacuum.
Example: Deoxygenated systems remained color stable up to 10 days, but lost color after few hours in presence of oxygen. presence.
Timberlake, 1960; King et al., 1980

9. Ascorbic Acid and Anthocyanins
Ascorbic acid and anthocyanins disappear simultaneously in fruit juices, suggesting some direct interaction between two molecules.
Instead, ascorbic acid induced degradation of anthocyanin results indirectly from hydrogen peroxide that forms during oxidation of ascorbic acid.
It has long been known that anthocyanin's and ascorbic acid (vitamin c) are mutually destructive in the presence of oxygen.
Ascorbic acid could have a negative or positive effect, depending on the media conditions. It was once thought that Ascorbic acid and anthocyanins disappear simultaneously in fruit juices, suggesting some direct interaction between two molecules.
Instead, it is now known that ascorbic acid induced degradation of anthocyanin results indirectly from hydrogen peroxide that forms during oxidation of ascorbic acid.
And It has long been known that anthocyanin's and ascorbic acid (vitamin c) are mutually destructive in the presence of oxygen.

10. Ascorbic Acid and Anthocyanins
The mechanism behind the destruction of anthocyanins by ascorbic acid has been the subject of some debate, but the prevailing hypothesis is that the autoxidation of ascorbic acid yields free radicals, which cleave the flavylium core structure of anthocyanins.
This is the known mechanism of what is going on. Previously it was thought that vitamin C and anthocyanins degraded to each other by direct interaction of the two molecules but the prevailing hypothesis is that the autoxidation of ascorbic acid yields free radicals, which cleave the flavylium core structure of anthocyanins.

11. Stabilization of Anthocyanin
Self – association of anthocyanins and in some models the contribution of metal complexation.
Also, there is information indicating that 3′- and 4′-OH in the B ring structure are determinants for the radical scavenging potential in flavonoids with a saturated 2,3-double bond, and that different patterns of hydroxylation and glycosylation may modulate their antioxidant properties. These two hydroxyl groups are important in protecting ascorbic acid against oxidation by chelating metal ions. When the anthocyanin-metal chelate is formed, a 20- to 25-nm shift in the visible spectra is observed, which in the presence of ascorbic acid induces a further shift of 10 to 15 nm. It was proposed the formation of the stable complex anthocyanin-metal-ascorbic acid, where ascorbic acid acts as a co-pigment. Thus, improved colors are obtained with the intrinsic protection of ascorbic acid from oxidation.

12. Co-pigmentation
Flavones co-occur with anthocyanins color of the plants as co-pigments.
Role: To protect the colored flavylium cation from the nucleophilic attack of the water molecule.
Flavones co-occur with anthocyanins and participate in the color of plants as copigments
Copigments (substances that contribute to anthocyanin coloration by protecting the anthocyanin molecules), so basically the intermolecular copigmentation is one of the mechanism of stabilization of anthocyanins in nature and is also responsible for the characteristic color and stability of aged red wines.

13. Stability of Copigmented Anthocyanins and Ascorbic Acid in Muscadine Grape Juice Processed by Hydrostatic Pressure
Del Pozo el at, 2013 published an article about stability of copigmented anthocyanins and ascorbic acid using rosemary and thyme polyphenolic extracts. First they found that the copigmentation increased visual color of the juice as evidenced in decline in hue angle. And copigmentation was also effective to increase the initial antioxidant capacity of the juice.
Del Pozo et al., 2013

14. Stability of Copigmented Anthocyanins and Ascorbic Acid in Muscadine Grape Juice Processed by Hydrostatic Pressure
Additionally, losses in antioxidant capacity were greater in juices where poliphenoloxidase activation occurred, indicating oxidation of polyphenolic compounds as enzyme substrates.

15. Factors to take home
Oxygen has a negative effect on anthocyanin stability.
Factors such as low pH and temperature can help to retain the color intensity.
Co-pigmentation improve the stability and increase the initial color intensity and antioxidant
Purified extracts from rosemary and thyme can be used to increase the color retention.