ЗВІТ З НДР 29-81 ЗА 2007 – 2009 Р

DOI: https://doi.org/10.4316/fens.2022.004

Journal homepage: www.fia.usv.ro/fiajournal

Journal of Faculty of Food Engineering,

Ştefan cel Mare University of Suceava, Romania

Volume XХI, Issue 1 - 2022, pag. 33 - 38

INFLUENCE OF THE ADDITION OF CHAMOMILE ON THE CONTENT OF

TANNINS IN TEA

Anna MAKARENKO
1
, *Mariia VOROBETS

1
, Iryna KONDRACHUK

1
, Anastasiia SACHKO

1
,

Heorhii VOROBETS
2

1Educational and scientific institute of Biology, Chemistry and Bioresources Yuriy Fedkovych Chernivtsi

National University, Ukraine, *m.vorobets@chnu.edu.ua,
2Educational and scientific institute of Physical, Technical and Computer Sciences Yuriy Fedkovych Chernivtsi

National University, Ukraine
*Corresponding author

Received 19th November 2021, accepted 25th March 2022

Abstract: In this work, the influence of chamomile on the content of tannin in the blended green and black
teas is investigated by the titrimetric method, which relies on the assessment of tannin oxidation
by potassium permanganate with the indicator indigo carmine. The standard procedure of titration was
altered in such a way that the dilution of filtrate used during the investigation was decreased by 10 times.

This modification made it possible to use the regular 250 ml flasks instead of big and inconvenient porce-

lain bowls. This way, identification of the point of equivalence became easier and more accurate. Applica-
tion of this modified method to the determination of tannin in a series of blended teas showed results that

are in good agreement with those obtained by the standard methods. They proved that the content of tannin

in tea does not depend on the added chamomile and, therefore, this herb does not depress the medical val-

ue of the investigated blended teas.

Keywords: tannins, blended tea, chamomile, medical values, modified titration, permanganatometry

1. Introduction

Tea is one of the most common beverages

in the world, which has unique taste and

specific organoleptic properties. It relieves

fatigue and headaches, increases mental

and physical activity, adsorbs harmful sub-

stances and removes them from the body

[1, 2]. The chemical composition of tea

leaves is very diverse and according to the

latest data [3], tea contains about 500 dif-

ferent substances. Tea leaves polyphenols

have antiviral, antitumor and anti-oxidant

activity. They are characterized by anti-

inflammatory, antimicrobial, hemostatic,

antispasmodic, antioxidant properties.

Having the ability to balance human blood

sugar levels, they can be used for the pre-

vention and treatment of type II diabetes

[4, 5]. There is no universal method of

quantitative analysis of tannins, because

tannins are a mixture of different classes of

polyphenols that have different structures.

The basic methods, which often used for

quantitative determination of tannins are

the next – gravimetric, photocolorimetric,

spectrophotometric, titrimetric, nephelo-

metric, tensiometric and others [3, 5–14].

Determination by gravimetric analysis is

often performed by deposition. Quantita-

tive determination of tannins by gravimet-

ric method is based on their precipitation

by gelatin, heavy metal ions, skin powder.

The disadvantage of this method is the

long-term definition. The titrimetric meth-

od is based on the oxidation of tannins by

potassium permanganate in the presence of

the indigo carmine indicator [15]. The dis-

advantage is the use of a large volume of

water during the titration, which is carried

out in a porcelain cup for evaporation and

mixing – with a glass rod creates signifi-

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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava

Volume XХI, Issue – 2022

Anna MAKARENKO, Mariia VOROBETS, Iryna KONDRACHUK, Anastasiia SACHKO, Heorhii VOROBETS,
Influence of the addition of chamomile on the content of tannins in tea, Food and Environment Safety, Volume XXI, Issue 1
– 2022, pag. 33 – 38

cant inconvenience of fixing the equiva-

lence point. Using various additives – ber-

ries, leaves, herbs, etc., tea can be enriched

with vitamins and beneficial properties.

Chamomile is one of the most valuable

medicinal plants, which constantly attracts

the attention of researchers. To date, scien-

tists have substantiated the possibility of

using herbal collection, one of the compo-

nents of which is chamomile, in anti-

cancer therapy [16]. Tannins and catechins,

as well as rutin (vitamin P) regulate the

process of collagen formation in blood

vessels, which helps to normalize blood

pressure. Tea is the main source of these

substances for the human body [7, 17].

Therefore, the study of the content of tan-

nins in various teas, in particular blended

with medicinal plants, is quite relevant.

The purpose of the work is to improve the

standard method of titrimetric determina-

tion of tannin content in tea; determine

how the different content of chamomile

supplement in blended teas based on black

/ green will affect the concentration of tan-

nins in them.

2. Materials and methods

The tea samples which were used for re-

search were: Greenfield Golden Ceylon

(1st grade, black leaf tea, loose, origin –

Ceylon, country of origin – Ukraine) and

green Ahmad Tea Chinese Green Tea (leaf

tea, Chinese). As a supplement, medicinal

chamomile was used – PJSC "Liktravy",

Ukraine. For the experiments, 2 series of

blended samples based on only black or

only green (black / green) tea with differ-

ent wt. % of chamomile additive were pre-

pared in parallel (Table 1).

Black / green tea without the addition of

chamomile and chamomile without tea

were used as control samples. To deter-

mine the content of tannins in the studied

samples of blended teas, a standard method

of permanganotometric titration in the

presence of an indigo carmine indicator

was chosen [15].
Table 1

Test samples

№ sample 1 2 3 4 5 6 7 8

Tea (black /
green)

wt. %

100 90 80 60 50 40 20 0

Chamomile

wt.%
0 10 20 40 50 60 80 100

Preparation of 0.1 % solution of indigo

carmine: 0.5 g of finely ground pure indigo

carmine was dissolved in 25 cm3 of chemi-

cally pure concentrated sulfuric acid (ρ =

1.84 g/cm3); the volume was adjusted to

500 cm3 by gradually pouring the solution

into distilled water. The resulting solution

was filtered through a pleated filter.

Preparation of 0.1 mol/dm3 of potassium

permanganate solution: KMnO4 weighing

1.58 g was weighed on technical scales.

After complete dissolution of the drug, the

contents of the flask (500 cm3) were ad-

justed to the mark with distilled water. The

normality of the prepared solution was es-

tablished after 10 – 12 days.

Preparation of exactly 0.1 mol/dm3 of oxal-

ic acid H2C2O4 solution: on analytical

scales weighed the exact portion of recrys-

tallized oxalic acid weighing 1.5750 g,

transferred to a volumetric flask with a ca-

pacity of 250 cm3, dissolved it in distilled

water, adjusted to the mark with distilled

water.

Standardization of KMnO4 solution: to 10

cm3 of freshly prepared oxalic acid solu-

tion was added 15 cm3 of sulfuric acid so-

lution (1 part of concentrated H2SO4 : 5

parts of H2O), heated to a temperature of

70 – 80 °C, immediately titrated. At the

end of the titration, the solution turns pink,

which does not disappear for 1 – 2

minutes.

Titration was performed three times, find-

ing the arithmetic mean value of the vol-

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava

Volume XХI, Issue – 2022

ume of titrant consumed. The normality of

the KMnO4 solution (
4KMnO

N ) was calcu-

lated by the formula:

422422

KMnO

OCHOCH

KMnO
V

VN
N


 ,

where
422 OCH

N – normality of the H2C2O4

solution, mol/dm3;
422 OCH

V – volume of 0.1

mol/dm3 of H2C2O4 solution (10 cm
3);

4KMnO
V – volume of KMnO4 solution used

on titration, cm3.

According to the standard method, the de-

termination of the content of tannins is car-

ried out starting with the grinding of a tea

sample in a porcelain mortar; 2.5 ± 0.0002

g of crushed tea is weighed on clear glass

and transferred to a 250 cm3 flask. Then

200 cm3 of boiling distilled water is poured

into the flask and placed in a water bath for

45 minutes. The resulting extract is filtered

into a volumetric flask with a capacity of

250 cm3. The content of the flask is cooled

to 20 °C and made up to the mark using

distilled water. Using a pipette, 10 cm3 of

the filtrate is taken and placed in a cup for

evaporation, which is pre-poured with 750

cm3 of water and 25 cm3 of 0.1 % solution

of the indigo carmine indicator. Potassium

permanganate is titrated using the 0.1

mol/dm3 solution with constant stirring

with a glass rod. During this, the blue color

of the liquid gradually changes through

blue-green, dark green, light green, yellow-

green, and turns yellow with a golden

tinge. Completion of titration is determined

by the disappearance of the green hue and

the appearance of a pure stable yellow col-

or. The volume of 0.1 mol/dm3 of potassi-

um permanganate consumed solution is

fixed in cm3. Titration is performed three

times and the arithmetic mean of the con-

sumed titrant volume is calculated. Simi-

larly, the blank titration of water with indi-

go carmine 0.1 mol/dm3 solution of potas-

sium permanganate is performed. The con-

tent of tannins (X) in % is determined by

the formula:

%;100
004157,0)(

1 





Vaa
X

where X is the tannins content, %; a – vol-

ume of 0.1 mol/dm3 of KMnO4 solution,

used on titration of prepared of tea extract,

cm3; a1 – volume of 0.1 mol/dm
3 of

KMnO4 solution used on titration of water

with indigo carmine, cm3; 0.004157 – the

amount of tannins that is oxidized 1 cm3

0.1 mol/dm3 solution KMnO4, g; m – the

weight of a portion of dry tea, g; V – vol-

ume of the obtained tea extract, cm3; V1 -

volume of tea extract taken for research,

cm3.

3. Results and discussion

As mentioned above, the standard method

for the determination of tannins in tea by

the permanganate method is not very con-

venient due to such features as the addition

of 750 cm3 of distilled water, use in the

titration of large porcelain cups and mixing

their contents with a glass rod. We modi-

fied the methodology. In particular, it is

proposed to reduce the volume of distilled

water by 10 times, which allows using or-

dinary titration flasks with a capacity of

250 cm3 instead of large and uncomforta-

ble porcelain cups and eliminates the need

to mix the contents of the flask with a glass

rod.The results of titration of extracts of

some test samples obtained by standard

and modified methods are presented in Ta-

ble 2.
Table 2

The volume of 0.1 N KMnO4 solution (ml) used

during the titration of some test samples by

standard and modified methodology

Sample №1 №3 № 4 № 5

Standard methodology 2.6 2.3 1.9 1.7

Modified methodology 2.6 2.3 1.9 1.7

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava

Volume XХI, Issue – 2022

Comparative analysis of the results (Table

2) shows that the values of the volumes of

titrant spent during titration by standard

and modified methods are absolutely the

same. In addition, as the water volume de-

creases, it is easier to observe a clear

change in color from blue to straw yellow,

i.e. the identification of the equivalence

point is more accurate. Determination of

tannins content in the studied samples was

performed using a modified method. The

obtained experimental results are presented

in Fig. 1. The data show that with decreas-

ing wt. % of green / black tea in blended

samples with chamomile medicinal content

of tannins decreases. In samples № 5 (50

wt. % Green tea and 50 wt. % Chamomile)

and № 6 (40 wt. % Green tea and 60 wt. %

Chamomile) the content of tannins is the

same. Test sample № 7 (20 wt. % Green

tea and 80 wt. % Chamomile) and control

sample № 8 (100 wt. % Chamomile) con-

tain 2.9 wt. % tannins (Fig. 1, curve 1). In

samples № 6 (40 wt. % Black tea and 60

wt. % Chamomile), № 7 (20 wt. % Black

tea and 80 wt. % Chamomile) and in the

control sample № 8 the tannins content is

almost the same and equal 2.6 – 2.7 wt. %

(Fig. 1, curve 2). There is a pattern: in

blended samples with a low content of

green / black tea, the value of the tannin

content is approximately 3 wt. %.

In general, regarding the effect of the addi-

tion of chamomile on the content of tan-

nins in blended black / green teas, it can be

stated that it does not depend on the con-

tent of chamomile. Approximation of ex-

perimental data shows a linear dependence

of tannin content on wt. % of tea in blend-

ed samples y = kx + a, where a = 0 (Fig.

1): based on green tea y = 0,104x; based on

black – y = 0,065x. However, when the

content values are less than 30 wt. % of

black / green tea, there is a deviation from

these linear dependences in the form of

some "background values" of tannin con-

tent in the range of 2.6 – 2.9 wt. %. If these

background values were characteristic of

chamomile, they should be manifested at

low wt. % chamomile in blended samples.

But under such conditions, the linear ap-

proximations would be different from the

zero value of the parameter a, in particular:

on the basis of green tea y = 0.074x +

2.92; based on black – y = 0.039x + 2.6.

According to the literature on the chemical

composition of chamomile [3, 9], tannins

are absent. Therefore, in our opinion, it is

incorrect to list the amount of potassium

permanganate used by wt. % tannins in

blended samples with a content of chamo-

mile drug more than 70 wt. %.

Fig. 1. Dependence of tannins content in blended teas on the wt. % of tea: 1 – green tea; 2 – black tea; 3 –

sensitivity limit of the method; lines on experimental graphs – linear approximation of theoretical models

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava

Volume XХI, Issue – 2022

Most likely, the reason for such results is

the relatively low sensitivity of the per-

manganatometric method to determine the

content of tannins in tea, which, according

to the literature, is equal to 3 wt. % (Fig. 1,

line 3). The content of 2.9 wt. % tannins in

the control sample № 8 can be explained

by the fact that potassium permanganate

oxidizes not only polyphenols, but also

simple phenolic compounds and other re-

ducing agents of non-phenolic nature, in

particular organic acids, vitamin C and a

number of compounds contained in cham-

omile. Theoretical modeling and quantita-

tive evaluation of the content (wt. %) of

tannins in samples of black or green tea

without the addition of chamomile were

performed to test this hypothesis. The theo-

retically calculated values correlate well

with the values of tannins content found

experimentally in the blended samples

(Fig. 2, Fig. 3).

Fig. 2. Comparative diagram of tannins content in samples № 2–7 (blended black tea),

calculated theoretically and found experimentally

Fig. 3. Comparative diagram of tannins content in samples № 2–7 (blended green tea),

calculated theoretically and found experimentally

4. Conclusions

It was found that the addition of chamo-

mile to black or green tea does not affect

the tannin content in them. Therefore, it is

possible to make blended teas with differ-

ent content of chamomile, which will have

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava

Volume XХI, Issue – 2022

medicinal properties without losing their

properties, i.e. to expand the range of teas.

The standard procedure of titration was

altered in such a way that the dilution of

filtrate used during the investigation was

decreased by 10 times. This modification

made it possible to use the regular 250 ml

flasks instead of big and inconvenient

porcelain bowls. This way, identification

of the point of equivalence became easier

and more accurate.

The proposed method for determining the

tannin content in blended black and green

teas has been tested. The results obtained

by standard and modified methods are ex-

actly the same.

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