Experiment 4 Analysis of Tea and Coffee

Siddhant Unde
J18IMT650
Experiment 4
Analysis of Tea and Coffee
Types of Tea
There are basically seven types of tea namely Green tea, Black tea, Herbal tea, Yellow tea,
Fermented tea, White tea, Oolong tea.
Manufacturing Process of Tea

Tea leaves are plucked. Withering is used to remove excess water from the leaves and allows a very
slight amount of oxidation. Bruising is a technique that breaks down the structures of leaf cells in
order to promote oxidation of tea leaves. First the raw materials are collected. Extraction is done
with the help of counter current extraction. Decanters are used for the separating large volumes of
insoluble tea leaf ccomponents from tea extracts. Volatile aroma compounds are stripped from the
extract prior or during evaporation and added back to the liquor before spray drying. Centrifuge is
used in the instant tea manufacturing process to remove fine particles from the extracted tea liquor.
The liquor coming from decreaming process is too dilute to pass directly to a drier and therefore the
liquor has to be concentrated, generally to 20-40% solids. Concentrated tea liquor is blended with
previously stripped aroma compounds before drying. Drum, spray and freeze drying can be used for
drying of concentrated tea liquor.
Color origin compounds in tea Alkaloids

The degradative products of chlorophyll (pheophytin and pheophorbide) may cause the made tea
color to become darker. Flavanols are converted to theaflavins and thearubigins during oxidation.
They are the compounds responsible for the dark color and robust flavors that are present in
oxidized teas. Flavanols, flavones, isoflavones and anthocyanins are thought to contribute to
the color of a tea's infusion and its taste
Analysis of sugar present in tea

An optical rotation detector can be used for selective detection of optically active materials.
The sugar in black and lemon teas were analysed using a combination of optical rotation
detector (OR) and refractive index detector (RI). Chromatogram of a standard sample.
Meso-erythritol is optically inactive and can only be detected by refractive index.
Chromatograms of sugar-free black tea and lemon tea. Limonene and Carvone have very
similar UV spectra, but show differences in the IR. Co-elution in the chromatogram detected
using UV as told above illustrates the inability of using UV to trigger fraction collection. IR
chromatograms at two different wave number ranges and the fractions collected using
those chromatograms. A Carvone standard and Spearmint oil were separated using HPLC
and fractions 1 and 2 were compared to confirm the separation and purity
Chlorophyll and carotenoid content in tea

The separation and identification of pigments, chlorophylls, and carotenoids of seven teas and fresh
leaf of tea (Camellia sinensis) by high-performance liquid chromatography (HPLC) are described.
HPLC was carried out using a Symmetry C (8) column with a photodiode array detector. Pigments
were eluted with a binary gradient of aqueous pyridine solution at a flow rate of 1.0 mL/min at 25
degrees C. HPLC analyses achieved the separation of more than 100 pigment peaks, and 79 pigment
species, 41 chlorophylls, and 38 carotenoids were detected. The presence of degraded chlorophylls
was a common feature, and the number and the variety of pigments differed with tea species.
Generally, the numbers of chlorophyll species tended to increase with processing steps, while
carotenoid species were decreased, especially by heating. Particularly in green teas, a change of
carotenoid structure, conversion of violaxanthin to auroxanthin, occurred. In hot water extracts of
teas, both chlorophylls and carotenoids were also detected, but the concentration of chlorophylls
was less than 2% as compared with acetone extracts. The pigment compositions were compared
between tea species, and they are discussed in terms of the differences in their manufacturing
processes.
Detection of pesticides and heavy metals in tea

Sample preparation for detection of pesticides
Five (5 g) of each tea sample were added 20 mL of dichloromethane and 20 mL of ethyl acetate. The
mixture was stirred followed by addition of 5 grams of sodium chloride (NaCl). Heated with
continuous stirring for about four hours. The contents of the blend were transferred to the
separating funnel. After formation of two layers, the organic layer was collected and the aqueous
layer was back extracted with DCM and ethyl acetate to collect the organic layer again. The collected
organic layers were mixed and dehydrated with anhydrous sodium sulphate and transferred to
rotary evaporator. The residue left was collected and dissolved in HPLC grade methanol (10 mL) and
stored until analysis.
HPLC-conditions, method development and quality assurance
A rapid and selective HPLC-UV gradient method was developed and validated to determine
pesticides in prepared samples of tea and pesticides standards. The Agilene 1260 Quaternary Pump
Gradient System with ODS 18 Column HPLC system was used for this study. Mobile phase was
acetonitrile: water (30:70). To achieve the development of the method optimization studies were
performed on each HPLC parameter such as solvent ratio, pH, temperature of column, sample and
injection volume, flow rate, wavelength and post time etc. For optimization, one parameter was
changed at the same time, while all others were held constant. Each sample was analyzed in
triplicate (for precision) to record the variation (if any). Calibration experiments were tested for
linearity, accuracy and precision. Limit of detection (3:1) and limit of quantification (10:1) was
calculated as signal-noise ratio.
Digestion of samples for detection of heavy metals
The digestion of the samples was done by means of a method of digestion with microwaves and, for
this purpose, the cones were optimized for the first time. 30 ml of hydrogen peroxide (H 2O2) were
added and diluted with 70 ml of distilled water. This solution was encoded as A. Subsequently, 50 ml
of nitric acid (HNO3) were extracted and diluted with 50 ml of distilled water and this solution was
encoded as B. One gram (g) of tea sample was collected in a flask of Round bottom and 10 ml of
deionized water, 5 ml of solution A and 5 ml of solution B were added. This round bottom flask was
placed in a silica gel containing beaker and its neck was sealed with a Styrofoam box. This
configuration was transferred to the microwave and irradiated for 30-40 seconds to support
complete digestion. This sample was filtered and diluted with distilled water and further analyzed in
the atomic absorption spectroscopy (Buck Scientific 210 VGP).The results of the analysis are shown
as mean/average as the data set does not allow statistical relations and correlations.
Caffeine Content
 First tea wastes are collected.
 Tea waste was placed in a beaker and 500ml distilled water was added to it.
 Mixture was digested for 15min and was filtered through funnel.
 To hot filtrate basic lead acetate solution was added drop wise to precipitate proteins and tanins
and the precipitate was allowed to settle down and was filtered.
 To the filtrate dilute sulphuric acid was added to remove lead as precipitate of lead sulphate.
 The clear solution obtained which was concentrated to 300ml and decolorized by adding animal
charcoal.
 The filtrate was shaken using 75 ml. Chloroform in a separating funnel and the chloroform layer
was collected and was evaporated on water bath to obtain crude caffeine.
 You can get caffeine testing strips that you can dip into coffee, and they'll give you an idea of
how much caffeine is in the brew. The strips have a couple of lines on them, marked D and C.
Decaffeinated beverages will only rise to the D line, caffeinated beverages will rise above it.
Water Extract
Principle
Extraction of soluble matter from a test portion of the product by means of water boiling under
reflux, filtration, evaporation of the filtrate to dryness and weighing of the residue.
Apparatus
Usual laboratory apparatus, and the following items: Constant-temperature oven. capable of being
controlled at 103 ± 2 cC, Steam bath , Desiccator, containing an efficient desiccant , Analytical
balance ,Dish fitted with a cover of capacity 50 ml, Volumetric flask of capacity 500 ml, Boiling flask
of capacity 500 mi. fitted with a reflux condenser, Pipette. Of capacity 50 ml.
Sample - Use a ground sample of known dry matter content, prepared as specified.
Procedure
Preparation of the dish
Remove the cover from the dish (5.5) and heat both for 1 h in the oven (5.1) at 103 ± 2 cC. Fit the
cover cool in the desiccator (5.3) and weigh to the nearest 0.001 g.
Test portion
Weight to the nearest 0.001 g. about 2 g of the ground sample (clause 6) into the 500 ml boiling flask
(5.7).
Determination
Add to the test portion 200 ml of hot distilled water or water of at least equivalent purity and reflux
gently for 1 h. rotating the flask occasionally. Cool to about 20 cC then transfer quantitatively into
the volumetric flask (5.6) and make up to the mark with water. Mix thoroughly and filter through dry
filter paper. Pipette 50 ml of the filtrate into the prepared dish (7.1) and evaporate to dryness on the
steam bath (5.2). Remove the cover heat the dish and contents in the oven (5.1) at 103 ± 2 "C for 2
h. replace the cover and cool in the desiccator (5.3). Heat again for 1 h. cool in the desiccator and
weigh; repeat these operations if necessary, until the difference between two successive weighing
does not exceed 0.002 g.

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Experiment 4 Analysis of Tea and Coffee

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Siddhant Unde

Manufacturing Process of Tea

Color origin compounds in tea Alkaloids

Analysis of sugar present in tea

Chlorophyll and carotenoid content in tea

Detection of pesticides and heavy metals in tea

HPLC-conditions, method development and quality assurance

Digestion of samples for detection of heavy metals

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