Development of a Process for Producing Red Tea Syrup Using Vacuum Evaporator EVAP-50 Owner Food Machinery

DEVELOPMENT OF A PROCESS FOR PRODUCING
RED TEA SYRUP USING VACUUM EVAPORATOR EVAP-50
OWNER FOOD MACHINERY

JENNY AN NISA

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2014

STATEMENT OF MANUSCRIPT AND SOURCE OF
INFORMATION AND TRANSFER OF COPYRIGHTS*
I declare with the truth that this manuscript entitled Development of a
Process for Producing Red Tea Syrup Using Vacuum Evaporator EVAP50 Owner Food Machinery is my own work with guidance of the advisors,
and has not been submitted in any form at any college, except Bogor
Agricultural University and Mae Fah Luang University. Sources of
information derived or quoted are from published and unpublished works of
the other authors mentioned in the text and listed in the References at the end
of this manuscript.

I hereby bestow the copyrights of my papers to Bogor Agricultural
University and Mae Fah Luang University.

Bogor, February 2014

Jenny An Nisa
NIM F24090102

ABSTRACT
JENNY AN NISA. Development of a Process for Producing Red Tea Syrup
Using Vacuum Evaporator EVAP-50 Owner Food Machinery. Supervised by
NATTHAWUDDHI DONLAO, PIYAPORN CHEUMCHAITRAKUN,
YADI HARYADI
Tea is the most popular beverage next to water. Preparation of tea from
dried tea leaves require many steps and is time-consuming. The goal of this
research is to make a convenient way to prepare tea syrup with vacuum
evaporation process. In the present study the effect of vacuum evaporating
condition on the properties of tea syrup and the most suitable condition for
making tea syrup were investigated with rating hedonic approach. Dried red
tea leaves (Camellia sinenesis var. assamica) were supplied from Boon Rawd

Farm Co., Ltd in Chiang Rai. The samples were ground using hammer mill.
Samples (1720 grams) were extracted with 43 L boiled water, infused for 5
minutes with stirring. Solids were filtered. Sucrose was added to tea extract
until TSS of 26 oBrix was reached. These initial concentration was evaporated
until 68 oBrix under vacuum with various pressures (-500 mmHg and -400
mmHg) and temperatures (70 oC and 60 oC). Sensory characteristics were
evaluated for tea syrup and tea drink. There was difference in value of
sensory characteristics of tea syrup and tea drink of different treatment. Based
on panelists, the highest score of both tea syrup and tea drink were at
treatment of 70 oC/-400 mmHg/28 h 30’. The shortest time of processing was
at treatment of 70 oC/-500 mmHg/8 h 35’. Meanwhile, the treatment resulted
in the highest total polyphenol was at treatment of 60 oC/-500 mmHg/35 h 8’.
Keeping tea syrup in room temperature for around 3 weeks that had once
been opened, the growth of molds was observed. Hence, the addition of
preservative is suggested.
Keywords: formulation, sensory analysis, tea syrup, tea drink, vacuum
evaporation

DEVELOPMENT OF A PROCESS FOR PRODUCING
RED TEA SYRUP USING VACUUM EVAPORATOR EVAP-50

OWNER FOOD MACHINERY

JENNY AN NISA

BACHELOR THESIS (SKRIPSI)
Submitted as a partial fulfillment of the requirements for
the degree of
SARJANA TEKNOLOGI PERTANIAN
at the Department of Food Science and Technology
Faculty of Agricultural Engineering and Technology
Bogor Agricultural University

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2014

Title
Name

NIM

: Development of a Process for Producing Red Tea Syrup Using
Vacuum Evaporator EVAP-50 Owner Food Machinery
: Jenny An Nisa
: F24090102

Approved by

Dr Ir Yadi Haryadi, MSc
Academic Advisor in
Bogor Agricultural University

Acknowledged by

Dr Ir Feri Kusnandar, MSc
Head of Department of Food Science and Technology

Date of Graduate:

Title
Name
NIM

: Development of a Process for Producing Red Tea Syrup Using
Vacuum EYaporator EVAP-50 Owner Food Machinery
: Jenny An Nisa
: F24090l02

Approved by

Academic Advisor in
Bogor Agricultural University

Date of Graduate:

0
4 MA.R 2014

FOREWORD

Praise The Lord that He gives me His blessings and mercies so this
manuscript could be completed. The research entitled “Development of a
Process for Producing Red Tea Syrup Using Vacuum Evaporator EVAP-50
Owner Food Machinery” that was carried out in Mae Fah Luang University
from June to October 2013.
By the completion of this research and manuscript, the author would
like to express great appreciation and sincere thanks to:
1. Dr Ir Yadi Haryadi, M.Sc as academic advisor, for the advise, guidance,
time, concern, patience, care, kindness, knowledge during study in Bogor
Agricultural University.
2. Aj. Natthawuddhi Donlao as advisor for his patience, kindness, time,
knowledge to the author during completion of research in Mae Fah
Luang University
3. Dr Piyaporn Cheumchaitrakun as co-advisor for her time, patience,
knowledge and all lecturers in School of Agro-Industry who have helped
solving the problems during the research in Mae Fah Luang University.
4. Bown Rood Farm who already supported raw material for the research.
5. My lovely mama for her loves and blessings and Kiky, and also my papa
for his supports.
6. DIKTI for full financial support during the research, Ambassador RI and

Education and Culture Attaché RI in Thailand for their supports, and the
Committee of AIMS Program in IPB (Pak Eko, Bu Dias, Bu Antung, Pak
Pungki) for a chance to do research in Mae Fah Luang University.
7. International Affairs Division of Mae Fah Luang University; Mrs.
Warunee Kaewbunruang as a coordinator in AIMS Program 2013; all
friends in School of Agro Industry; and other friends which cannot be
mentioned one by one, for the unforgettable moments during stay in
Thailand.
8. AIMS Students 2013, i.e. Ardy, Sarida, Desi, Olga, Afi, Stella and
Ardiyansah for togetherness, cooperation, helps, care, supports, sharings
in Thailand.
9. All staffs in Labortorium S4, P’Tik, P’ Kwan, P’Sud, P’Pin, P’Nen,
staffs in Tea Institute, P’Ab, P’Fon, P’Ni, P’Wa, P’Wow, P’ Pla and also
Pak Gatot (IPB) for their helping and support during research.
10. My roomate Santika, Mazmur (Sisca, Faithy, Gloria, Meta, and Uthy),
Cicely for their supports, love, care.
11. All friends in Komisi Diaspora and ITP 46 for every moments that we
had been through for almost 4 years.
Last but not least, hopefully this manuscript is useful for the readers and
gives a real contribution in the food science development particularly in the

manufacture of tea syrup.
Bogor, February 2014
Jenny An Nisa

LIST OF CONTENT
LIST OF TABLES
LIST OF FIGURES
LIST OF APPENDICES
INTRODUCTION

1

Background

1

Objectives

2

METHOD

2

Raw Materials and Chemical Agents

2

Equipments

2

Sample Preparation

3

Determination of Processing Time

3

Analysis of the Physicochemical Characteristics of Raw Material

5

Analysis of the Physicochemical Characteristics of Tea Extract and
Tea Syrup

5

Sensory Analysis

7

RESULT AND DISCUSSION

7

Characteristics of Raw Material

7

Characteristics of Tea Extract

8

Effect of Temperature and Pressure on Processing Time

8

Effect of Processing on the Characteristics of Tea Syrup

9

Effect of Processing on the Characteristics of Tea Syrup and Tea
Drink

11

Sensory Characteristics of Tea Syrup

13

Evaluation of Machine

16

Additional Observation

17

CONCLUSION

17

SUGGESTION

17

REFERENCES

18

APPENDICES

20

VITAE

33

LIST OF TABLES
1
2
3
4
5
6
7
8
9
10
11
12
13
14

Physicochemical properties of raw material
Particle size measurement of ground-dried red tea leaves
Physicochemical properties of tea extract
Processing time of tea syrup
TSS of tea syrup
a w of tea syrup
Viscosity of tea syrup
Total polyphenol content of tea syrup
Total reducing sugar of tea syrup
pH of tea syrup and tea drink
ΔL*, Δa*, Δb* of tea syrup
Color (ΔE) of tea syrup and drink
Gallic acid calibration curve
Gallic acid concentration (µg/mL) obtained from calibration
curve
15 Total polyphenol of tea syrup

8
8
8
9
9
10
10
11
11
12
12
13
24
25
26

LIST OF FIGURES
1
2
3
4
5
6
7
8
9

Diagram of tea syrup preparation
Result of sensory analysis of tea syrup
Result of sensory analysis of tea drink
Gallic callibration curve
Hydraulic pressure
Hammer mill
Sieve Retsch
Digital viscometer Brookfield
Vacuum evaporator EVAP-50 OFM

4
14
15
24
32
32
32
32
32

LIST OF APPENDICES
1
2
3
4
5
6
7
8
9
10

Moisture content and dry matter of dried red tea leaves
Particle size measurement of ground-dried red tea leaves
Color of tea syrup
Color of tea drink
Dry matter of tea syrup
Total polyphenol content of tea syrup
Total reducing sugar of tea syrup
Sensory analysis of tea syrup
Sensory analysis of tea drink
Documentation

20
20
21
22
23
24
27
28
30
32

1

INTRODUCTION
Background
Tea is the most popular beverage next to water in the world and
consumed by a range of age groups in all levels of society. Making tea drink
involves pouring hot water on the dried leaves of the tea plant, Camellia sinensis
(Hicks 2001; Grigg 2002). Camellia have two majors varieties, Camellia
sinensis var. sinensis and Camellia sinensis var. assamica, originating from the
tropical rain forests of China and Assam, respectively. The difference of the two
varieties is Assam variety has larger leaf than pure China variety. The pure
China variety has very small leaves, only a few centimetres in length even when
mature (Clifford 1997).
There are three types of tea products based on fermentation time, i.e.
unfermented (green tea), partially fermented (oolong tea), and fully fermented
(black tea). Fermentation, in this case, refers not to a microbial process, as with
beer or wine, but the natural browning reaction catalyzed by enzymes
endogenous in the plant (Harbowy and Balentine 1997).
According to Cheevajit poll conducted on Bangkok residents in 2006
revealed that tea (54.6%) was an indispensable item that is regularly consumed
after carbonated drinks (55.7%) (Ekachampaka and Wattanamano 2007). Red
tea is popular and one of the main ingredients to make popular Thai tea. Thai tea
is a native-grown red-leafed tea, sometimes spiced with star anise seed is adde
(depends on company), which is usually brewed strong and then blended with a
rich swirl of evaporated milk and a lot of ice (Commins and Sampanvejsobha
2008). Red tea comes from full fermentation of Camellia sinensis var. assamica,
but the fermentation time is shorter than black tea.
Consumption of red tea is the same way as other teas that need to be
brewed in hot/boiled water and then filter the leaves. These steps take time, a
simple way should be provided by making tea syrup. Tea syrup a simple product
to help people consume tea drink in a convenient way and also one of new
product development of tea. Syrup is a drink product made from mixing sugar
and water with minimal 65% of sugar solution, with or without other ingredient
food, with or without food additives which is allowed by law (BSN 2013). Syrup
contains high concentration of sugar which helps to extend the shelf life. When
consumed, it needs to be added with water (Wijaya 2002).
The tea syrup is made by evaporating solution of tea extract and sugar.
When vapour pressure of the solution reaches the pressure of its surroundings,
the solution will boil (Earle and Earle 1983) and liquid phase will change into
gaseous phase. In this high temperature, sugar will caramelize and tea
polyphenol will degrade (Diaz and Clotet 1995). Boiling point can be reduced,
in this case, by a vacuum environment. Evaporation under vacuum condition
will decrease processing temperature and time. Hence, degradation of food
properties can be reduced (Naknean et al. 2013).

2

Objectives
The objectives of this study are to evaluate the effect of vacuum
evaporating condition on the physicochemical and sensory analysis of tea syrup
and tea drink and to investigate the most suitable condition of evaporation
process for making tea syrup which has total soluble solids (TSS) of 68 oBrix.

METHOD
Raw Materials and Chemical Agents
Dried red tea leaves (Camellia sinensis var. assamica) were supplied by
Boon Rawd Farm Co., Ltd in Chiang Rai. Refined sugar was obtained from local
market. Copper (II) sulfate pentahydrate (CuSO 4· 5H 2 O), gallic acid, zinc sulfate
heptahydrate (ZnSO 4· 7H 2 O), potassium sodium tartarate tetrahydrate
(KNaC 4 H 4 O 6· 4H 2 O), sodium carbonate anhydrous (Na 2 CO 3 ), sodium
hydroxide (NaOH), K 4 Fe(CN) 6· 3H 2 O, methylene blue, Folin-Ciocalteu, aquades,
Whatman filter paper No. 5 and Advantec filter paper 5A (Whatman filter paper
No. 41) were obtained from Chemical Laboratory of Mae Fah Luang University.
Equipments
This research used vacuum evaporator EVAP-50, which have never been
used before in main research in Processing Laboratory of Mae Fah Luang
University. The type of evaporator is batch pan evaporator that has long product
residence time. The batch pan is jacketed with oil as heat transfer medium.
Heater heats oil in the jacket layer. Exposure of the food liquid to high
temperatures for long time is likely to cause changes in the color and flavor of
the liquid. In some cases such changes may be acceptable. However, in the case
of heat-sensitive liquids, such changes are undesirable. To reduce such heat
damage, the pressure above the liquid in the evaporator may be reduced below
atmospheric pressure by means of vacuum pump as suggested by Brennan
(2006).
The other equipment used were sieve Retsch Type AS200, digital
pHmeter (pH cyberscan 510), Color Quest XE/Hunter Lab, digital viscometer
Brookfield model DV-III, hand refractometers (1–32 oBrix ATAGO Model N2E and 58–90 oBrix ATAGO Model N-3E, Japan), hydraulic pressure (Owner
Food Machinery Co., Ltd Thailand), a w meter of Novasina, measurable plastic
glass pot, container, pot, filter cloth, tray, spoon, thermometer, funnel, hot plate,
beaker glass, Buchner funnel, vacuum pump, analytical weighing, weighing
(scale: 60 kg), kuvet, reaction tube, moisture can, cylinder PE, pasture, amber
glass, volumetric flask, pipette volumetric scale, stirrer rod, mortar, spatula,
erlenmeyer flask, beaker PE, glass bottle, wood stirrer, and bowl.

3

Sample Preparation
Dried red tea leaves (Camellia sinensis var. assamica) were ground with
hammer mills (to increase surface area) and kept at room temperature before use.
Ground red tea leaves (1720 g) were extracted by 43 L of boiled water for 5
minutes while stirring. Ground-dried red tea leaves extract were filtered through
4 layers of filter cloth. The residues were pressed using hydraulic pressure
machine to get more filtrate. Refined sugar was added until the concentration of
solution reached TSS of 26 oBrix. The tea extract was kept in refrigerator at
temperature of 4 oC for less than 24 hours before further processing.
Determination of Processing Time
Tea extract was evaporated using vacuum evaporator under various
conditions. Temperature of machine were set at 60 oC and 70 oC. Pressure of
machine was adjusted manually using valve to release pressure if pressure gauge
showed greater value than it should be or outlet was opened a little, to reach 400 mmHg and -500 mmHg. Hence, the combination of treatment were 60 oC/500 mmHg, 60 oC/-400 mmHg, 70 oC/-500 mmHg, and 70 oC/-400 mmHg,
thereby A, B, C, D syrup were obtained, respectively. During evaporating,
stirring was applied by turning on the agitator at the speed of 80 rpm. The
processing time to obtain tea syrup of 68 oBrix was noted. The syrup sampling
for TSS determination was done if the surface of tea syrup in the evaporator
reached the just above thermocouple. In this case, at each treatment combination,
the evaporator was opened and TSS of sample of tea syrup was determined by
means of hand refractometer ATAGO Model N-3E. The procedure was repeated
several times (3–5 times) until the TSS of tea syrup reached 68 oBrix. The total
time of process was counted from the beginning. Tea syrup was bottled with
preheated bottle and kept in refrigerator at temperature of 4 oC for further
analysis. The procedure of making tea syrup is presented in Figure 1. The tea
syrups obtained by those processing conditions were then analyzed for their
physicochemical and sensory characteristics. Hence, the parameters of the syrup
presented in this report were the results of the processing condition (temperature,
pressure, and processing time). Due to the time constraint, the experiment was
not replicated.

4

Dried red
tea leaves

1720 g of grounddried red tea leaves

ground

Steeped
T = 100 oC ± 1; t = 5 minutes

Filtered and
Pressed

Ground-dried red
tea leaves extract
12.6 kg of
refined sugar
Tea extract
(26 oBrix)

Kept in refrigeration
temperature (4 oC) before main
treatment, for less than 24 h

Evaporated
T = 60 oC, 70 oC; P = -400 mmHg,
-500 mmHg until TSS: 68 oBrix

Tea syrup (68 oBrix)
A,B,C,D

Preheated
bottle

filled

Tea syrup
in bottle

Figure 1 Diagram of tea syrup preparation

5

Analysis of the Physicochemical Characteristics of Raw Material
Moisture content and dry matter of dried red tea leaves (ISO 1980)
Around 5 g of dried red tea leaves, weighed to the nearest 0.001 g, were
placed in a moisture can and heated in an oven at 103 ± 2 oC for at least 16 h
until constant weight was reached.
Particle size distribution of ground-dried red tea leaves (Sonaye and Baxi
2012)
A representative weighed sample (1720 g of ground-dried red tea leaves)
was poured into the largest screen openings of 4 mm at the top of sieve. Each
lower sieve in the column had smaller openings than the one above. A round
pan/the receiver was at the base. Every sieve in the column was placed in a
mechanical shaker. The shaker was operated the column for 20 minutes. After
the shaking was completed, the material on each sieve was weighed. The weight
of the sample of each sieve was divided by the total weight to give a percentage
retained on each sieve. To find the percent of aggregate passing through each
sieve, found the percent retained in each sieve first. To do so, the following
equation was used:
� �����
% Retained = � ����� × 100%
% Cumulative passing = 100% – % cumulative retained
Total soluble solids of dried red tea leaves extract (Borse et al. 2002)
Total soluble solids (TSS) of dried red tea leaves extract were determined
using a refractometer after sample preparation. Dried red tea leaves (2 g) was
added to 140 mL boiling distilled water in a clean beaker and allowed to boil
(infuse) for 4 minutes. The dried red tea leaves extract was filtered through
Whatman No. 5 filter paper, using a Buchner funnel, by applying a vacuum
pump. A drop of well-mixed of cooled dried red tea leaves extract was placed on
the prism of the refractometer. Readings were taken in triplicate and an average
taken as TSS (%).
Viscosity of dried red tea leaves extract
Sixteen mL of dried red tea leaves extract was placed in the digital
viscometer Brookfield model DV-III. A suitable spindle, keeping the RPM
constant, was selected by trial and error. Readings were taken in triplicate and an
average taken as the final viscosity of the dried red tea leaves extract.
Analysis of the Physicochemical Characteristics of Tea Extract and Tea
Syrup
TSS
TSS of tea extract and tea syrup were determined by as degree Brix using
a digital hand held refractometer (ATAGO Co., Ltd Tokyo, Japan) after cooling
to 20 ± 1 oC.

6

Viscosity
Tea extract and tea syrup were conditioned in room temperature (25 ±
1 oC). Sixteen mL of tea extract was fed into viscometer with spindle ULA. Six
hundred mL of tea syrup was placed in a beaker glass (have 3 inches of inside
diameter) and rested for at least 12 hours (overnight) to release the small bubbles
to surface, so that small bubbles could be removed by spoon. Incorporation of air
to tea syrup was occurred during replacing tea syrup from evaporator. Bubbles
could affect measurement of viscosity. Tea syrup was measured its viscosity
using viscometer with the presence of guard leg and using spindle LV2.
Color measurement
Color of tea syrup and tea syrup after dilution (tea drink) were measured
by using of Color Quest XE/Hunter Lab (USA) expressed as CIE L*, a*, and b*
values. The results were calculated using ΔE formula. ΔE = (∆L*2 + ∆a*2 +
∆b*2)1/2. ∆L* = L* tea syrup/drink – L* tea extract
Total polyphenol (ISO 2005)
The total polyphenol content of tea syrup (TPC) was determined by
spectrophotometer, using gallic acid as standard, according to the method
described by the International Organization for Standardization (ISO) 14502-1
(ISO 2005). Briefly, 1.0 mL of the diluted sample extract (50–100 fold dilution)
was transferred in duplicate to separate tubes containing 5.0 mL of a 1/10
dilution of Folin-Ciocalteu’s reagent in water. Then, 4.0 mL of sodium
carbonate solution (7.5% w/v) was added. The tubes were then allowed to stand
at room temperature for 60 minutes before absorbance at 765 nm was measured
against water. The TPC was expressed as gallic acid equivalents (GAE) in g/100
g material. The concentration of polyphenols in samples was derived from a
standard curve of gallic acid ranging from 10 to 100 µg/mL,
� . � . �� .100
Total phenolic content, TPC (g GAE /100 g db) = 10000 . � . % ��

C
= gallic acid concentration (µg/mL) obtained from calibration curve
V
= volume of tea syrup solution (mL)
DF
= dilution factor
% DM = dry matter of tea syrup
W
= weight of tea syrup (g)

Water activity
Water activity of tea syrup were measured by using a w meter Novasina.
Total reducing sugar (AOAC 2000)
Accurately weighed samples (about 11–15 g of tea syrup) was
transferred to a 250 mL volumetric flask and distilled water was added to about
2/3 volume. Five mL of Carez I solution and 5 mL of Carez II solution were
added. The flask was shaken vigorously after each addition and then diluted to
the volume (V 1 = 250 mL). The solution was filtered through Whatman No. 41
filter paper into a 250 mL erlenmeyer flask. The first 5 mL of the filtrate was
discarded and the filter was collected. The sample solution that was obtained in
this step was called sample solution A. Sample solution A was filled to a 50 mL

7

burette. Ten mL of mixed Fehling’s solution was transferred into a 250 mL
erlenmeyer flask. Around 3–5 glass beads and 10 mL solution A were added to
erlenmeyer and boiled by hot plate for exactly 2 minutes. Three or four drops of
methylene blue indicator were added. Hot titration was completed by sample
solution A from burette within 3 minutes. Experiment was carried out in
duplication. Average volume of sample solution was determined.
� ×�1 ×100
Reducing sugar (% w/w) = �� ×1000 × �
F
V1
100
Va
1000
W

= invert sugar factor for 10 mL of Fehling’s solution
= Total volume of sample solution A (mL) (in this experiment = 250)
= conversion factor from 1 g to 100 g
= accurate volume of sample solution A used for titration (mL)
= conversion factor from mg to g
= weight of tea syrup(g)

Dry matter of tea syrup (AOAC 2002)
Around 2–5 g of tea syrup was dried in flat dish (Alumunium) for 12 h at
≤ 70 °C, under pressure 50 mmHg (6.7 kPa). Dish was removed from the
oven, cooled in desiccators, and weighed. (Redry 1 h and repeat process until
change in weight between successive dryings at 1 h intervals is 2 mg ).
Sensory Analysis
Sensory analysis was carried out on all samples using rating hedonic 9scale for tea syrup and tea drink in D1 canteen, Mae Fah Luang University.
Around 10 mL of tea syrup from 4 treatments were placed in plastic containers
and determined for appearance, odor, and overall acceptance by 35 untrained
panelists. The panelists were students or staffs of MFU. Each syrup was diluted
until 12 oBrix of TSS was obtained. The ratio for water and syrup could be
obtained by calculating using Pearson square. For tea drink, around 20 mL was
determined for appearance, tea aroma, tea flavor, sweetness, and overall
acceptance by 35 panelists untrained. Data from 29 panelists of 35 panelists
were analyzed. Six of them were dropped due to unacceptable data. Around 25–
50 panelists were needed in hedonic scale ratings (for the nine-point hedonic
scale) for laboratory scale (Stone and Sidel 2004).

RESULT AND DISCUSSION
Characteristics of Raw Material
Dried red tea was supported by Boon Rawd Farm for this project which
had characteristics as follow: moisture content of 6.91%, dry matter of 93.09%
(Table 1). Dried red tea extract had characteristics as follow: TSS of 0.6 oBrix,
and viscosity of 2.6 cP (Table 1). Hammer mill was used to grind dried red tea
leaves to increase surface area and also extraction rate. Ground-dried red tea
leaves had different particle size as shown in Table 2.

8

Table 1. Physicochemical properties of raw material
Physicochemical properties
Moisture of dried red tea leaves
Dry matter of dried red tea leaves
TSS of dried red tea leaves extract
Viscosity of dried red tea leaves extract

Amount
6.91%
93.09%
0.6 ºBrix
2.6 cP

Table 2. Particle size measurement of ground-dried red tea leaves
Sieve size % Cumulative Passing
4 mm
99.91
1 mm
95.95
600 µm
79.56
74.33
500 µm
250 µm
32.23
125 µm
8.41
63 µm
4.24
Characteristics of Tea Extract
The tea extract obtained before evaporation process has the characteristics
as shown in Table 3. It had pH of 4.90, viscosity of 3.34 cP, TSS of 26 ºBrix, L*
of 26.24, a* of -0.013, and b* 5.38. In the process of evaporation, it was
expected that the TSS will increase to 68 ºBrix.
Table 3. Physicochemical properties of tea extract
Physicochemical properties
Amount
pH
4.90
Viscosity
3.34 cP
TSS
26 oBrix
Color (L*, a*, b*)
26.24, -0.013, 5.38
Effect of Temperature and Pressure on Processing Time
The objective of this research is to obtain tea syrup which have total
soluble solids of 68 oBrix using vacuum evaporator EVAP-50 at temperature of
60 oC and 70 oC and pressure of -400 mmHg and -500 mmHg. Table 4 shows
processing time to obtain tea syrup of 68 oBrix. The shortest time to obtain tea
syrup of 68 oBrix was 8 h 35’, at the treatment of 70 oC/-500 mmHg.

9

Table 4 Processing time of tea syrup
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg
60 oC/-400 mmHg
70 oC/-500 mmHg
70 oC/-400 mmHg

Time (h)
35 h 08’
34 h
8 h 35’
28 h 30’

Processing time of each treatment was different. The longest processing
time was 35 h 8’, 34 h, 28 h 30’, and 8 h 35’ for A syrup at treatment of 60 oC/500 mmHg, B syrup at treatment of 60 oC/-400 mmHg, at treatment of D syrup
70 oC/-400 mmHg, and C syrup at treatment of 70 oC/-500 mmHg, respectively.
It took 30 minutes to concentrate palm sugar syrup until 40 oBrix was obtained
using vacuum evaporator at temperature of 80 oC, while 20 minutes at
temperature of 70 oC (Naknean et al. 2009). It was clear that by increasing
temperature, the processing time reduced. Similiarly, by increasing the vacuum
condition from -400 mmHg to -500 mmHg the processing time tend to reduce.
The tea syrups obtained by those processing conditions were then analyzed for
their physicochemical characteristics.
Effect of Processing on the Characteristics of Tea Syrup
Total Soluble Solids (TSS)
The TSS of tea syrup is presented in Table 5. The highest TSS was A
syrup at treatment of 60 oC/-500 mmHg/35 h 8’, 68.8 oBrix, while the lowest
TSS was D syrup at treatment of 70 oC/-400 mmHg/28 h 30’, 64 oBrix.
Table 5. TSS of tea syrup
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

TSS
68.8 oBrix
68 oBrix
68 oBrix
64 oBrix

In Thailand, standard TSS for palm sugar syrup shall not be less than
65 oBrix. In Canada have similiar rule for finished maple syrup. Finished maple
syrup shall not less than 66 oBrix in order to prevent growth of micro-organisms
during storage under room temperature (Naknean et al. 2013). TSS in this
research were suppossed to be 68 oBrix, D syrup had TSS of 64 oBrix due to
systematic error when reading at that treatment.
Water Activity (aw)
The a w of tea syrup is presented in Table 6. Concentration process are
conducted primarily for the purpose of decreasing the water content of a food,
simultaneously increasing the concentration of solutes and thereby decreasing
perishability (Fennema 1996), in this case water activity of syrup. In this
research, temperature, pressure, and time did not affect to a w. Most of a w in the
range of 0.80–0.85 for all tea syrup. In this range of a w (0.80–0.87), most molds

10

(mycotoxigenic penicillia), Staphylococcus aureus, most Saccharomyces can
grow (Fennema 1996). D syrup had the highest a w (0.85) due to the lowest TSS.
Table 6. aw of tea syrup
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

aw
0.80
0.81
0.80
0.85

Viscosity
The viscosity of tea syrup is presented in Table 7. Tea syrup had variations
of viscosity, 138.33–419.9 cP. Variation of tea syrup’s viscosity due to variation
of final TSS. The viscosity of most liquids increase as the solid content increase
during evaporation (Brennan 2006). The lowest viscosity was obtained by D
syrup at treatment of 70 oC/-400 mmHg/28 h 30’, 138.33 cP, due to the lowest
total soluble solid (64 oBrix) (Table 7).
Table 7. Viscosity of tea syrup
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

Vicosity (cP)
419.9
344.57
403.87
138.33

Total polyphenol content (TPC)
The total polyphenol content of tea syrup is presented in Table 8. The
total polyphenol content of tea syrup were compared among each other of all tea
syrup. The highest total polyphenol content (TPC) was 0.67 g/100 g db at A
syrup at treatment of 60 oC/-500 mmHg/35 h 8’ compared to others treatment
which had higher temperature (70 oC) and pressure (-400 mmHg) and shorter
processing time (below 35 h). While at the same temperature but different
pressure at B syrup at treatment of 60 oC/-400 mmHg/34 h was the second
highest TPC. Vacuum evaporation which use lower heating temperature and
lower oxygen seemed to be appropriated for preserving total phenolic
(Chaovanalikit et al. 2012). The smallest TPC was at treatment of 70 oC at every
pressure, 0.55 g/100 g db. Su et al. (2003) studied stability tea theaflavin (TF,
component that affect red color in tea extract) in black tea, the result was heating
100 oC for 3 h TF was completely degraded and heating at 70 oC for 3 h
degraded TF 56%. Heating treatment will affect to TF.

11

Table 8 Total polyphenol content of tea syrup
Syrup Treatment

TPC (g GAE /100
g db tea syrup)
60 oC/-500 mmHg/35 h 8’
0.67
o
60 C/-400 mmHg/34 h
0.63
70 oC/-500 mmHg/8 h 35’
0.55
o
70 C/-400 mmHg/28 h 30’
0.55

A
B
C
D

Tea syrup have 6 times dilution based on weight or 8 times based on
volume. It means 100 g tea drink from dilution of tea syrup have 0.112 g GAE
from tea syrup that had the highest total polyphenol in this research. In other side,
the total polyphenol in black tea according to Astill et al. 2001 was 14.4% or
14.4 g in 100 g tea extract. The difference is high, probably because application
of heat for long time.
Sucrose and other Maillard compounds in syrup will interfere the test
which use Folin-Ciocalteu by enhancing the development of the blue color so
the data certainly overestimate (Payet et al. 2006).
Total reducing sugar (TRS)
Total reducing sugar was detected in the tea syrup. Sucrose was used as
sweetener and to increase TSS. During process, sucrose was inverted to invert
sugar. Panpae et al. (2008), sucrose inversion in various sugar cane juice
samples strongly depended on temperature and pH. Increase in temperature
during heating and decrease in pH value tend to increase in rate of sucrose
inversion. The highest content of reducing sugar was obtained by D syrup at
treatment of 70 oC/-400 mmHg/28 h 30’, 0.08% w/w (Table 9). It was shown at
D syrup that had the highest content of TRS had the second lowest pH value. In
contrast, at A syrup the lowest TRS had the highest pH value. Invert sugar is not
only undesirable due to its hygroscopy so can reduce shelf life but also desirable
to prevent crystallization. Caramelization could not happen since this reaction
effectively undergo at temperature of 120 oC or above (Naknean et al. 2013).
Table 9 Total reducing sugar of tea syrup
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

TRS
0.04
0.05
0.05
0.08

Effect of Processing on the Characteristics of Tea Syrup and Tea Drink
pH
The pH of tea syrup and drink are presented in Table 10. If pH of tea
extract was 4.90 (Table 3) is compared to that of tea syrups, it was clear that
there was tendency of decrease for all treatment (Table 10). Decrease also

12

happened at tea drink. Heat and pressure might decrease acidity of tea syrup.
Furthermore, acidity of tea drink are below than that of tea syrup and tea extract.
Table 10. pH of tea syrup and tea drink
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

pH - syrup
4.87
4.76
4.80
4.77

pH - drink
4.79
4.65
4.68
4.71

The biggest decrease (Δ/delta) of tea syrup from tea extract was 0.14,
0.13, 0.10, and 0.03 for B syrup at treatment of 60 oC/-400 mmHg/34 h, D syrup
at treatment of 70 oC/-400 mmHg/28 h 30’, C syrup at treatment of 70 oC/-500
mmHg/8 h 35’, and A syrup at treatment of 60 oC/-500 mmHg/35 h 8’,
respectively. From these data, decrease of A syrup is not as much as B, C, and D
syrup. The biggest decrease (Δ/delta) of tea drink from tea syrup was 0.12, 0.11,
0.08, and 0.06 for C, B, A, and D, respectively. It was clear that decrease in tea
syrup from tea extract was bigger than tea drink from tea syrup. Hence, the
biggest decrease between tea extract and tea drink was 0.25, 0.22, 0.19, 0.11 for
B, C, D, and A, respectively.
Tea drink had range 4.65–4.71 (Table 10). Street et al. 2006 examined
30 samples of tea samples (green tea, black tea, semi-fermented, and white tea)
from different origins. Those pH of the tea infusions, which measured by
potentiometer, were in range of 4.04–5.08 (average 4.42).
In term of temperature at 60 oC, pH syrup showed slightly decrease
compared to 70 oC. As well as at pressure of -500 mmHg pH syrup showed
slightly decrease compared to -400 mmHg. The pattern was same with pH of tea
drink.
Color
Table 11 showed ΔL*, Δa*, Δb* for tea syrup. The color differences of tea
syrup and drink are presented in Table 12.
Table 11. ΔL*, Δa*, Δb* of tea syrup
Syrup
Treatment
ΔL*
Δa*
Δb*
A
60 oC/-500 mmHg/35 h 8’
-0.45
-1.52
-0.82
B
60 oC/-400 mmHg/34 h
-1.46
-2.36
0.42
C
70 oC/-500 mmHg/8 h 35’
-4.96
-1.29
-1.53
D
70 oC/-400 mmHg/28 h 30’
-1.87
-2.18
0.89
Notes :
ΔL* : L*tea syrup – L*tea extract ; -ΔL* : darker ; ΔL* : lighter
Δa* : a*tea syrup – a*tea extract ; -Δa* : more blue ; Δa* : more red
Δb* : b*tea syrup – b*tea extract ; -Δb* : more green ; Δb* : more yellow

13

Table 12. Color (ΔE) of tea syrup and drink
Syrup
A
B
C
D

Treatment
60 oC/-500 mmHg/35 h 8’
60 oC/-400 mmHg/34 h
70 oC/-500 mmHg/8 h 35’
70 oC/-400 mmHg/28 h 30’

ΔE - syrup
1.95
3.05
5.39
3.09

ΔE - drink
2.87
3.05
2.75
3.43

Color was measured using CIE L*, a*, b* scale. Among L*, a*, b* value,
L* value had the greatest variances and this value represents light-dark spectrum.
All treatments showed decrease in ΔL* value of tea syrup. Color darkens
because of high solid content and chemical changes, especially the Maillard
reaction (Nindo et al. 2007). The highest value of ΔL* was C syrup which had
the highest temperature and the lowest pressure and processing time.
Naknean et al. (2013) studied properties changes of palm sugar syrup
produced by an open pan dan vacuum evaporator. They found palm sugar syrup
produced by open pan was the highest decrease in L* value. Decrease in L*
value of palm sugar syrup produced by vacuum evaporator at temperature of
80 oC was higher than 70 oC. It was clear that vacuum evaporator with lower
temperature helped to reduce effect of thermal degradation. Value of a* and b*
also decrease in all treatments, just a slight increase at b* value of syrup D.
These decrease indicated that color had less red and yellow component.
Total color differences (ΔE) indicated the magnitude of overall color
difference between tea extract and tea syrup, also between tea extract and tea
drink. The ΔE value of tea syrup was bigger than tea drink. Dissolving tea syrup
with addition of water (tea drink) tend to decrease the ΔE value. In other words,
color after dissolving tea syrup almost return to the tea extract. Data showed C
syrup (70 oC/-500 mmHg/8 h 35’) which had the biggest ΔE at tea syrup, had the
smallest of ΔE after diluting.
Sensory Characteristics of Tea Syrup
Appearance, odor and overall judgment by panelists of tea syrup are presented in
Figure 2, whereas appearance, tea aroma, tea flavor, sweetness, and overall of tea drink
are presented in Figure 3.

14

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

5.76

A

B

C

D

Odor - Tea syrup

Scale

Scale

Appearance - Tea syrup
7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

6.48

A

B

C

D

Scale

Overall accepatance Tea syrup
7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

6.59

A

B

C

D

Figure 2 Result of sensory analysis of tea syrup. The determined attributes
were appearance, odor, and overall acceptance (from left to the
right). A (60 oC/-500 mmHg/35 h 8’), B (60 oC/-400 mmHg/34 h),
C (70 oC/-500 mmHg/8 h 35’), D (70 oC/-400 mmHg/28 h 30’)
syrup.

Appearance - Tea drink

Tea aroma - Tea drink

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

6.86

Scale

Scale

15

B

C

A

D

B

C

D

Tea flavor - Tea drink

Sweetness - Tea drink

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0

6.72

Scale

Scale

A

6.52

A

B

C

D

6.55

A

B

C

D

Scale

Overall acceptance - Tea
drink
7.07

7.2
7.0
6.8
6.6
6.4
6.2
6.0
5.8
5.6
5.4
5.2
5.0
A

B

C

D

Figure 3 Result of sensory analysis of tea drink. The determined attributes were
appearance, tea aroma, tea flavor, sweetness and overall acceptance (from
left to the right). A (60 oC/-500 mmHg/35 h 8’), B (60 oC/-400 mmHg/34
h), C (70 oC/-500 mmHg/8 h 35’), D (70 oC/-400 mmHg/28 h 30’) syrup.

16

The highest average score of tea syrup and drink was D syrup at
treatment of 70 oC/-400 mmHg/28 h 30’ for each attribute (for tea syrup:
appearance, odor, and overall acceptance; for tea drink: appearance, tea aroma,
tea flavor, sweetness, and overall acceptance).
There were some comments from panelist during sensory analyzing. For
tea syrup: “improve appearance for consumption, attract to drink”. “The syrup
can be more diluted and if container is small will be easier and more
convenience”. “Physicochemical among samples are same, difficult to give the
score”. For tea drink: “some cups are delicious, some cups are too sweet”. “I like
tea that have combination of bitter and sweet, I like tea that have less sweet”.
“All of samples are sweet”. “Reduce sweet and increase the aroma”. “I like
sample with code of 756 (C syrup, 70 oC/-500 mmHg/8 h 35’), but never smell
aroma”.
All comments can be concluded that all tea syrups were almost same and
the appearance should be improve. Tea drink were too sweet for panelists
(Thailand) and the aroma could not be detected. In fruit juices, concentration
using evaporator would lose the aroma due to volatile compound that were
readily destroyed by heat even vacuum (MacDowell et al. 1948). This case was
same with this research. MacDowell et al. (1948) offered addition a portion of
fresh, single strength to strong concentrate (syrup), hence a concentrate of
medium strength that have subtantially portion of the original aroma, flavor, and
palatability were obtained.
Volatile compound which contribute to aroma was lost on the first hour
of processing due to valve of pressure was opened to meet setting point. In other
word, the system was open so there was mass transfer between system and
environment. In this case, volatile compound was transferred from system to
environment that cause loss of aroma. Vacuum evaporation will lose volatile
compound resulting in a concentrate with poor organoleptic qualities. Other
technologies can be used as alternative way to get a simple way of drinking tea
such as spray drying and freeze drying which result in powder form.
Evaluation of Machine
The present study was to evaluate the use of new vacuum evaporator
type EVAP-50 to make tea syrup. It was said that one of the advantages of this
new machine is shorter processing time than that of pan evaporator (at
atmospheric pressure). In addition, the process can be conducted in lower
temperature. Hence, it was expected that pleasant aroma of tea can be retained.
However, in reality, volatile compound which contribute to aroma was lost. In
this case, the opening of pressure valve of the machine causing the loss of aroma
volatile compounds. The problem may be solved by redesigning the machine,
closing the system namely valve of pressure and condensate. During evaporation
which heat was applied, volatile compound changed to gas phase and together
with water vapor went to condenser and then condensate. Condensate should be
close system and have another distillation column to change gas phase of
volatile compound to liquid phase so aroma can be preserved and return to final
product (syrup).

17

In addition to the loss of tea flavor, second disadvantage of the machine
is the lack of part for indicating the TSS of syrup inside the evaporator for TSS
determination without opening it. The third disadvantage is the lack of automatic
mechanisms to stop the vacuum pump once the vacuum condition was set as
experimental factor.
Additional Observation
Two levels of temperature and two levels of pressure were introduced in
combination to obtain tea syrup having total soluble solids (TSS) of 68 oBrix.
The aim of producing tea syrup with TSS of 68 oBrix is to have a shelf stable tea
syrup at room temperature. It was found that with different combinations, the
processing time to obtain tea syrup with TSS of 68 oBrix also varies. The
shortest time to obtain tea syrup of 68 oBrix was at the combination of 70 oC/500 mmHg (8 h 35’), whereas the longest was at the combination of 60 oC/-500
mmHg (35 h 8’). By increasing the temperature from 60 oC to 70 oC, the
processing time was reduced. Similiarly, by increasing the degree of vacuum
condition the processing time was also reduced. From this preliminary
experiment, it was found that the the combination of 70 oC/-500 mmHg
treatment was the best processing option because of the shortest processing time.
However, based on the preference of panelists, it was found that D syrup
(obtained by treatment of 70 oC/-400 mmHg/28 h 30’) was the most preferred (in
term of of odor, appearance, overall acceptance). Similiar judgment was also
obtained for tea drink (in term of appearance, tea aroma, tea flavor, sweetness,
and overall acceptance).
In the surface of tea syrup that had been kept in room temperature for
around 2–3 weeks and that had once been opened, suspected-mold was observed.
Hence, the addition of additive to increase shelf life was needed.
At A syrup which had the highest TSS (68.8 oBrix), a little crystal sugar
were observed in the bottom of bottle after keeping in refrigeration temperature
for 1 month. While others syrup, which were also kept in refrigeration
temperature, crystal sugars were not detected for 2 weeks.

CONCLUSION
The best tea syrup and drink obtained was D syrup at treatment of
70 C/-400 mmHg/28 h 30’ which had the highest score based on sensory
analysis. The highest total polyphenol content was A syrup at treatment of
60 oC/-500 mmHg/35 h 8’. Preservative was needed to make shelf life longer if
stored at room temperature. Final TSS is supposed to lower than 68.8 oBrix to
prevent crystallization. Evaporator type batch pan was not suitable for
evaporating tea due to lost of aroma.
o

SUGGESTION
Next researchers should give the same time of every treatment and do all
treatments at least two replications. Improving the design of machine should be

18

done. Preservative is needed to increase shelf life such as potassium sorbate.
Mixing with invert sugar such as glucose and fructose can prevent crystallization.
Research about how to prevent loss tea aroma is needed. Another technology to
make tea syrup is needed to make comparation which technology will give the
best procedure to make tea syrup.

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20

APPENDICES
Appendix 1 Moisture content and dry matter of dried red tea leaves
Trial
1
2
3
Mean
SD

W
5.0008
5.0008
5.0004

W1
17.2123
16.6268
16.7550

W2
12.5414
11.9778
12.1100

dried tea
4.6709
4.6490
4.6450

MC
6.60
7.04
7.11
6.91
0.28

% DM
93.40
92.96
92.89
93.09
0.276

Notes:
W : weight of sample before drying (g)
W 1 : weight of sample + dried empty cup (g)
W 2 : weight of empty cup (g)
Examp