The document outlines a method for quantifying polyphenols, specifically tannins in apple cider using potassium permanganate titration and indigo carmine as an indicator. It details the procedure, temperature variations for testing, and formulas for calculating total polyphenol concentrations. The study highlights the effects of temperature on polyphenol levels and includes results from titrations at different temperatures.

1. Temp on polyphenol (tannins apple cider) quantification 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.
Effect of temp (15, 45, 55, 65, 75) will be studied, using water bath.
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2. Apple cider suitable for IA study due to its pale colour
Indicator change from blue to greenish yellow
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.
For apple cider, 2ml was added to centrifuge tube.
Tube was immersed into water bath at various temp for 10 mins.
After 10 mins, 2ml water 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
Temp/C Ini
vol
Final
vol
Vol (X)
KMnO4
Polyphenol
mg/L TA
15 7.1 7.7 0.6 332
45 14.9 15.4 0.5 249
55 17.2 17.6 0.4 166
65 20.4 20.8 0.4 166
75 22.8 23.3 0.5 249
Blank (Y) 4.7 4.9 0.2 --
End point
Apple cider
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
(0.6 - 0.2) x 4.157 x 0.02 x 10000 = 332mg/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
Temp on polyphenol (tannins apple cider) quantification using potassium permanganate titration (Lowenthal permanganate)

3. End point
Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000
(0.6 - 0.2) x 4.157 x 0.02 x 10000 = 332mg/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
Temp/C Ini
vol
Final
vol
Vol (X)
KMnO4
Polyphenol
mg/L TA
15 7.1 7.7 0.6 332
45 14.9 15.4 0.5 249
55 17.2 17.6 0.4 166
65 20.4 20.8 0.4 166
75 22.8 23.3 0.5 249
Blank (Y) 4.7 4.9 0.2 --
0
100
200
300
400
0 20 40 60 80
Total
polyphenol/mg/L
TA
Temp/C
Temp/C vs Total
polyphenol/mg/L TA
0
0.2
0.4
0.6
0.8
15 45 55 65 75
Vol
KMnO4
Temp/C
Temp/C vs Vol KMnO4
0
100
200
300
400
15 45 55 65 75
Polyphenol/mg/L
TA
Temp/C
Temp/C vs Polyphenol/mg/L
TA
Temp on polyphenol (tannins apple cider) quantification using potassium permanganate titration (Lowenthal permanganate)
Apple cider suitable for IA study due to its pale colour