Timeline of inquiry (in terms of my question): What affect does temperature Have on seasonal color changes For different elevations? How are anthocyanin Concentrations affected By temp. in decid. Trees? How do growing conditions for the Different kinds of Grapes used in wine- Making affect antho- Cyanin concentration? Season ended too Quickly, no Leaves on trees Too expensive What are the different Concentrations of cyanidin-3- Glucoside in wines and juice and Does that reflect it’s color?
Background- Anthocyanins • Water-soluble pigments • Responsible for pink to blue coloration in plants • Not found in the plastids like other pigments but in the vacuoles • There are over 300 structurally different anthocyanins that have been identified in nature • Have antioxidant properties • Are used as a food-colorant • Anthocyanin concentrations are affected by processing
More about anthocyanins… • The most abundant form of anthocyanin found in nature is cyanidin-3-glucoside • Has a molar absorptivity of 26,900 L/(mol·cm) • Has a molecular weight of 445 g/mol • Has maximum absorption at wavelength of 510 nm • Red wines and grape juices are believed to have the highest concentration of anthocyanins and that they therefore have higher antioxidant properties (French paradox) • Cranberries also have a relatively high concentration of anthocyanins
Initial Model Concentration of cyanidin-3-glucoside Color density of liquid (wine/juice) affects • The darker liquids will have higher concentrations of cyanidin-3-glucoside; the darkest liquid will have the highest concentration while the lightest liquid will have the least. Hypothesis:
Assumptions: • Cyanidin-3-glucoside is the most abundant form of anthocyanin in each of the 8 samples • Beer-Lambert law is an adequate equation to use to calculate the concentration of this form of anthocyanin • There are no other components/pigments interfering with the absorbance at the wavelength of 510 nm
Methods • Choose 8 samples of liquid to test, none of which have any artificial coloring added: • Red wine (Cabernet sauvignon) • White wine (Riesling) • Canned grape juice (Concord) • Frozen grape juice (Concord) • Bottled apple juice • Frozen apple juice • Cranberry juice • White Cranberry juice (white cranberry and white grape mix) • Rank liquids according to density of color
To the lab (measuring absorbance): • Set the spectrophotometer’s wavelength to 510 nm • Dilute the red wine, cranberry juice and grape juices so that the absorbance reading would be between 0 and 1 (for more accurate measurement) • Take readings for each sample • Use the following equation to determine the concentration of each sample: C(mg/L)= A____× MW(g/mol) × DF × 10³mg Ε(L/mol·cm) L(cm) A= absorbance MW=molecular weight Ε= molar absorptivity L= pathlength
Data Tables and Graphs Table 1: Color Scale: Grape juices Red wine Cranberry juice Apple juices White wine White cranberry Dark red amber purple Red golden white
All samples: Red wine has the greatest concentration of cyanidin-3-glucoside. Frozen apple juice has the smallest concentration of C-3-G. White wine and white cranberry juice have no C-3-G.
Just the wines: Red wine (cabernet sauvignon) has much more cyanidin-3-glucoside than white wine (riesling).
Grape juices: Frozen grape juice has a greater concentration of cyanidin-3-glucoside than canned grape juice.
Cranberry juices: White cranberry juice does not have any cyanidin-3-glucoside while regular cranberry juice has 9.5 mg/L.
Apple juices: Bottled apple juice has a higher concentration of cyanidin-3-glucoside than frozen apple juice.
Evidence and Final Claim • The color of the liquid doesn’t necessarily represent the amount of cyanidin-3-glucoside present • The grape juice had less anthocyanin than the red wine even though its color was darker • Neither the white wine nor the white cranberry juice had any cyanidin-3-glucoside • Even though the grape juices appeared to be the same color, their concentrations differed • The apple juices also appeared to be the same color but their concentrations also differed slightly
Revised Theory/Model Antioxidant properties ? ? Concen- Tration of Other antho- cyanins Not a direct relation Color density Of liquid + Concentration of cyanidin-3-glucoside ? ? Growing conditions: temp., UV exposure, etc. Methods used for processing
References • Clifford, M.N. Anthocyanins-nature, occurrence and dietary burden. Journal of the Science of Food and Agriculture. 80: 1063-1072 (2000) • Bancroft, W.D. The biochemistry of anthocyanins. Science. 98(2535): 98-100 (1943) • Roberts, H.F. The causes of autumn coloration. The Scientific Monthly. 45(5): 427-435 (1937) • Burns, J., Mullen, W., Landrault, N., Teissedre, P., Lean, M.E.J., Crozier, A. Variations in the profile and content of anthocyanins in wines made from cabernet sauvignon and hybrid grapes. Journal of Agricultural and Food Chemistry. 50: 4096-4102 (2002) • And many more…