IA on polyphenol (tannins) quantification between green and black tea using potassium permanganate titration (Lowenthal permanganate).

1. Click here, here, here for research papers
Green vs black teas were compared.
1g tea placed into same tea bag so ensure surface area can be control.
Polyphenol (tannins) quantification between green and black tea using potassium permanganate titration (Lowenthal permanganate)
Polyphenols are antioxidants :
- found in blackberry, wines, blueberry, cranberry, grapes, cider, citrus fruits
- Tannins (TA), flavonoids, catechins, EGCG, EGC, ECG.
- quantification using potassium permanganate (titration)
- using indigo carmine indicator (blue) to green yellow
Antioxidants that can be quantified using permanganate titration
Procedure:
Potassium permanganate 0.004M (0.02N) was prepared.
0.1% (w/v) indigo carmine indicator 0.1g in 100ml acidified with H2SO4.
End point is greenish yellow.
Limitation : antioxidants like Vit C will be included
Assumption - all antioxidants esp polyphenol will be quantified.

2. Green vs black teas in 20ml hot water
at 88C for 4 mins
1 gram of each tea taken out and placed
into a bag with same surface area
Activated charcoal to absorb other antioxidants
Procedure:
Potassium permanganate 0.004M (0.02N) was prepared.
0.1% indigo carmine indicator 0.1g in 100ml acidified with H2SO4.
End point is greenish yellow.
1g tea in 20ml hot water at 88C for 4 mins.
2ml tea and 200ul of indigo carmine were added. Blue sol obtained.
Titrated with 0.004M KMnO4 until end point is seen.
Ini and final vol recorded.
Blank titration was done – 2 ml water and 200ul indicator without any antioxidants.
Activated charcoal to absorb other antioxidants, leaving EGCG/tannins behind
End point
Polyphenol (tannins) quantification between green and black tea using potassium permanganate titration (Lowenthal permanganate)
Antioxidant Ini
vol
Final
vol
Vol KMnO4
(X)
Polyphenol
/mg/L TA
Green tea 11.1 14.2 3.1 2411
Black tea 6.7 8.8 2.1 1579
Green tea +
charcoal
14.2 16.5 2.3 1745
Black tea +
charcoal
8.9 10.7 1.8 1330
Blank (Y) 16.5 16.7 0.2 --
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
(3.1 - 0.2) x 4.157 x 0.02 x 10000 = 2411mg/L
Formula that can be used. Click here for reference
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
4.157 – conversion factor to TA equivalents
10000 – conversion factor from % to mg/L of TA.
N – normality for KMnO4 which is 0.02N or 0.004M
X – Vol KMnO4 used
Y – Vol blank titration
TA – tannic acid

3. Green vs black teas in 20ml hot water
at 88C for 4 mins
1 gram of each tea taken out and placed
into a bag with same surface area
Activated charcoal to absorb other antioxidants
End point
Polyphenol (tannins) quantification between green and black tea using potassium permanganate titration (Lowenthal permanganate)
Antioxidant Ini
vol
Final
vol
Vol KMnO4
(X)
Polyphenol
/mg/L TA
Green tea 11.1 14.2 3.1 2411
Black tea 6.7 8.8 2.1 1579
Green tea +
charcoal
14.2 16.5 2.3 1745
Black tea +
charcoal
8.9 10.7 1.8 1330
Blank (Y) 16.5 16.7 0.2 --
0
1
2
3
4
Green tea Black tea Green tea +
charcoal
Black tea +
charcoal
Blank (Y)
vol
KMnO4
Teas with charcoal
Teas vs Vol KMnO4
0
1000
2000
3000
Green tea Black tea Green tea +
charcoal
Black tea +
charcoal
Polyphenol/mg/L
TA
teas with charcoal
Teas vs Polyphenol/mg/L TA
Green tea have more polyphenol compared to black tea
Tea with charcoal have lower antioxidants
some might be absorbed by charcoal.