The production of guava juice fortified with dietary fiber

ORIGINAL ARTICLE
The production of guava juice fortified with
dietary fiber
Woranong Thongsombat1, Anchalee Sirichote2
and Suganya Chanthachum3
Abstract
Thongsombat, W., Sirichote, A. and Chanthachum, S.
The production of guava juice fortified with dietary fiber
Songklanakarin J. Sci. Technol., March 2007, 29(Suppl. 1) : 187-196
The production of guava juice fortified with soluble dietary fiber as pectin extracted from guava
cake (peel, pulp, seeds) was conducted. The waste guava cake from juice processing plant was used for
pectin extraction using sodium hexametaphosphate method followed by pectin precipitation using acidified
ethanol method. A yield of 30.50±0.34% crude pectin was achieved. Crude pectin also contained 4.71±0.18%
moisture, 0.34±0.21% protein, 0.68±0.00% ash, 20.70±0.16 g (%dwb) soluble dietary fibers. pH of crude
pectin was 3.06±0.02. The L* a*and b* values were 81.17±0.21, 4.76±0.04 and 15.43±0.07, respectively. Water
holding capacity and bulk density were 0.90±0.01 g.water/g.solid and 0.96±0.05 g/ml, respectively. This study
found that the optimum conditions for guava juice extraction using pectinase at 45oC were 0.10 % v/v pectinase
concentration and 2 12 h incubation time. Under these optimum conditions, production of guava juice with
different ratios of total soluble solids (oBrix) to acid as citric acid content (%) including, 24.0, 28.0, 32.0, 35.0
and 40.0 oBrix-acid ratio, and product sensory evaluation were also conducted. By the consideration from the
greatest perceived scores of all sensory evaluation attributes including color, turbidity, odor, flavor and
overall acceptability, the oBrix-acid ratio of 40.0 was selected for guava juice processing. The clarified guava
juice was then fortified with pectin powder extracted from previous experiments using various pectin
1Graduate student in Food Technology, 2Ph.D.(Food Science), 3Ph.D.(Food Science), Asst. Prof., Department
of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla, 90112 Thailand.
Corresponding e-mail: anchalee.s@psu.ac.th

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
188
Thongsombat, W., et al.
concentrations: 0, 0.25, 0.50 and 0.75% (w/w). It was found that the perceived scores of the overall accept-
ability attribute decreased (p<0.05) with increasing of pectin concentration. The greatest perceived score of
the mouthfeel attribute was observed from the use of 0.25% pectin. Therefore, the optimum concentration
of 0.25% soluble dietary fiber as pectin for guava juice fortification is selected for further guava juice
processing.
Key words : guava (Psidium guajava), dietary fiber, crude pectin, pectinase, ºBrix-acid ratio
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®“°°?–?«?°“?º?‘µ?È”??—Ëß?”¡“„™â‡ªì?«—µ?ÿ¥‘?„?°“? °—¥‡æ°µ‘?¥â«¬«‘?’?’Ë„™â “??–?“¬‚´‡¥’¬¡‡Œ°´–‡¡µ“øÕ ‡øµ
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‡æ°µ‘?¬—ߪ?–°Õ?¥â«¬ª?‘¡“?§«“¡™?È? ‚ª?µ’? ‡?â“ ·?–„¬Õ“À“??–?“¬?È” ‡?à“°—??âÕ¬?– 4.71±0.18 0.34±0.21
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bulk density ‡?à“°—? 0.90±0.01 °?—¡?È”/°?—¡¢Õß·¢Áß ·?– 0.96±0.05 °?—¡/¡?. µ“¡?”¥—? ‡¡?ËÕ»÷°…“°“? °—¥?È”??—Ëß
‚¥¬°“?„™â‡Õ?‰´¡å‡æ°µ‘‡? ?’ËÕÿ?À¿Ÿ¡‘ 45oC æ?«à“  ¿“«–?’ˇÀ¡“– ¡?’Ë ÿ¥ ”À?—?°“? °—¥?È”??—Ëߧ?Õ§«“¡‡¢â¡¢â?
¢Õ߇Õ?‰´¡å‡æ°µ‘‡? ‡?à“°—? 0.10% ‚¥¬ª?‘¡“µ? ·?–‡«?“„?°“? °—¥ 2.50 ™—Ë«‚¡ß ‡¡?ËÕ?”°“?º?‘µ?È”??—Ëß‚¥¬„™â
 ¿“«–?’ˇÀ¡“– ¡?’Ë ÿ¥?’È ¥â«¬?È”??—Ëß?’Ë¡’Õ—µ?“ à«?ª?‘¡“?¢Õß·¢Áß?—ÈßÀ¡¥?’Ë?–?“¬?È”‰¥âµàÕª?‘¡“?°?¥?—ÈßÀ¡¥„??Ÿª
°?¥´‘µ?‘° (oBrix-acid ratio) ‡?à“°—? 24.0 28.0 32.0 35.0 ·?– 40.0 ?È”??—Ëß?’Ë ‰¥â?”ª?–‡¡‘?º??“ߪ?– “? —¡º— ?’Ë
æ‘®“??“§ÿ??—°…?– ’ §«“¡¢ÿà? °?‘Ë??  ? ™“µ‘·?–§ÿ??—°…?–‚¥¬?«¡ æ?«à“?È”??—Ëß?’ËÕ—µ?“ à«?ª?‘¡“?¢Õß·¢Áß
?—ÈßÀ¡¥?’Ë?–?“¬?È”‰¥âµàÕª?‘¡“?°?¥?—ÈßÀ¡¥ ‡?à“°—? 40 ‡ªì?Õ—µ?“ à«??’ˉ¥â?—?º?°“?ª?–‡¡‘?°“?¬Õ¡?—?¡“°?’Ë ÿ¥„?
?ÿ°§ÿ??—°…?–?“ߪ?– “? —¡º—  °“?º?‘µ?È”??—Ëß?’ˉ¥â‡¡?ËÕ‡µ‘¡‡æ°µ‘?„?ª?‘¡“?µà“ßÊ ‰¥â·°à 0.00%, 0.25%, 0.50%
·?– 0.75% ‚¥¬?È”À?—° æ?«à“§–·??°“?¬Õ¡?—?¢ÕߺŸâ?¥ Õ?™‘¡„?§ÿ??—°…?–‚¥¬?«¡®–?¥?ß (p<0.05) µ“¡
ª?‘¡“?‡æ°µ‘??’ˇµ‘¡‡æ‘Ë¡¢÷È? ‚¥¬?’˪?‘¡“?‡æ°µ‘? 0.25% ‰¥â?—?§–·??°“?¬Õ¡?—?„?§ÿ??—°…?–‡??ÈÕ —¡º— ¿“¬„?
ª“° (mouthfeel)  Ÿß?’Ë ÿ¥ ß“?«‘®—¬?’È®÷ߧ—¥‡??Õ°ª?‘¡“?„¬Õ“À“??’Ë?–?“¬‰¥â„??Ÿª‡æ°µ‘? 0.25% ‡ªì?ª?‘¡“??’Ë
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Guava (Psidium guajava L.), which belongs
low methoxylated pectin (50%) amounting to
to the Myrtaceae family, is a native of tropical
more than 10% of the dry weight. Therefore, guava
America and is widespread throughout the tropical
juice has special characteristics in its flavor and
and subtropical areas (Chopda and Barrett, 2001).
viscosity, which is popular in many tropical
Guava is consumed fresh or made into processed
countries (Yen and Lin, 1998).
products such as juice, nectar, puree, jam and jelly
Commercial guava juice processing normally
(Kashyap et al., 2001). Guava fruit not only has
involves the use of pectinase enzymes to increase
exotic flavor but also is a rich source of relatively
juice yield from pressed guava peel and pulp

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
189
Thongsombat, W., et al.
(Alkorta et al., 1998). Guava cake (peel, pulp and
1.2 The extraction of pectin
seeds) a by-product from juice production, accounts
Pectin was extracted from guava cake
for 30% of the guava fruit weight and is commonly
powder by the method of Iglesias and Lozano
used as animal feed or fertilizer. However, very
(2004) with a slight modification. The powder was
recent investigations indicate that guava peel and
washed with hot water (50 g powder: 1 L hot water)
o
pulp can also be used as a new source of dietary
at 75 C for 15 min to remove pigments, then
fiber (DF) and antioxidant phenolic compounds
filtered through cheesecloth. A solution of 0.75%
(Jimenez-Escrig et al., 2001).
sodium hexametaphosphate (Ajax-Finechem,
The DF includes plant substances that resist
NSW, Australia) was prepared and mixed with the
the action of human digestive enzymes. Total DF
washed powder at the ratio of 50 g powder to 1 L
is divided into two major fractions: water-soluble
solution. The pH of slurry was adjusted to 3.5 with
(pectin, gum) and water-insoluble (cellulose, lignin,
6 N hydrochloric acid then incubated in a water
some of the hemicellulose). The latter is mainly
bath (Model WB/OB7-45, Memmert, Schwabach,
o
credited for regulating bowl movement whereas
Germany) at a constant temperature of 75 C for
the soluble fraction is chiefly involved in lower-
1 h. During incubation period, the slurry was
ing blood cholesterol and glucose adsorption
stirred with a spatula every 15 min.
(Grigelmo-Miguel and Martin-Belloso, 1999)
After the incubation, the solution was
Therefore, guava cake may be a valuable
filtered through a Buchner funnel with a Whatman
food ingredient, especially as a supplement in
No.4 filter paper and diatomaceous earth pre-coat.
guava product itself. The objectives of this study
The filtrate was concentrated in a Rotary vacuum
o
were: (a) to study the extraction method and
evaporator (Model-1000, Eyela, Japan) at 55 C to
chemical and physical properties of crude pectin
a volume of 500 ml. The concentrated filtrate was
from guava cake; (b) to study the optimum enzyme
precipitated with acidified ethanol (Concentrated
concentration and incubation time to increase the
filtrate : 1 N HCl : 95% ethanol = 4:1:3), allowed
o
yield of guava juice; (c) to formulate the optimum
to stand overnight at 4 C, then centrifuged at 3,500
o
o
Brix to acid ratio for guava juice processing; and
xg for 15 min at 4 C with a refrigerated centrifuge
(d) to determine an acceptable concentration of
(Model RC-5B plus, Sorvall, U.S.A.). The crude
crude pectin for the fortification of guava juice.
pectin slurry was washed with 70% ethanol to
o
remove HCl and dried in a hot air oven at 50 C for
Materials and methods
24 h. The dried crude pectin was ground to powder.
The % yield of the extraction was calculated as
1. Extraction and characterization of pectin
Y = (weight of pectin after extraction/weight of
1.1 Preparation of dried guava cake
dried guava cake) x 100.
Dried guava cake was prepared by the
1.3 Determination of chemical and phy-
method of Satra (1999). Guava cake (peel, pulp and
sical properties of crude pectin
seeds) was obtained directly from a commercial
All reagents were analytical grade. The
guava juice processing plant. The guava cake was
?-amylase, protease and amyloglucosidase were
washed with water three times, wrapped in
purchased from Sigma Co. (St. Louis, MO., U.S.A.)
cheesecloth and pressed to remove liquid and dried
for soluble dietary fiber (SDF) analysis.
o
in an air dryer at 60 C for 6-8 h to obtain dried
Crude pectin powder was analyzed for
press cake with 8% moisture content. The dried
moisture, ash and protein contents according to
sample was ground using a blender at speed 1
AOAC (2000). Soluble dietary fiber content of
(National, Tokyo, Japan). The guava cake powder
crude pectin was also analyzed according to
was immediately packed in a nylon-bag, vacuum
AOAC (2000) method 993.19.
sealed with a vacuum sealer (Henkovac, Germany)
A 2% (w/v) solution of crude pectin
o
and stored at 4 C before use.
powder was prepared for pH measurement with a

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
190
Thongsombat, W., et al.
glass-electrode pH-meter (Model PB-20, Sartorius,
obtained previously were placed 40 g and 100 g
U.S.A.). The color of the powder was measured
each in twelve 250 ml beakers. Enzyme pectinase
with Hunter Colorimeter (Model ColorFlex,
(derived from Aspergillus niger, E.C.3.2.1.15, P
HunterLab, U.S.A.). Results were expressed in
4716, 25,000 PG units, Sigma Co., St Louis, MO.,
CIE L*, a*, b* values.
U.S.A.) was placed 5, 10 and 15 ml in each of the
Bulk density was determined by filling
three 100 ml volumetric flasks, immediately added
a preweighted 25 ml graduate cylinder with crude
citrate buffer solution (pH 4.0) to bring total volume
powder and shaking slightly. The volume of the
to 100 ml in each volumetric flask. 1.4 ml pectinase
crude powder was recorded and the content of the
solution from each volumetric flask was added to
cylinder was weighed. The bulk density was
each of the twelve beakers containing guava cake
expressed as weight per volume. Water-Holding
sample, stirred well and incubated in a water bath
o
o
Capacity (WHC) of the crude pectin powder was
at 45 C to attain a product temperature of 45 C for
determined according to the method of Chen et al.
1.5, 2.0 and 2.5 h with occasionally stirring every
(1988) with a slight modification. A 250 mg sample
30 min. The guava cake without pectinase treat-
of crude pectin powder was placed into a 50 ml
ment was used as a control. After reaching each
centrifuge tube, distilled water was added to bring
incubation times, immediately heated the pectin-
o
the total volume to 25 ml, and stirred occasionally
ase treated sample at 90 C for 2 min with constant
with a stirring rod. The slurry was allowed to stand
stirring to stop the reaction of pectinase. The juice
for 60 min then centrifuged at 10,000 xg for 15
was then extracted from the pectinase treated
min. After centrifugation, the supernatant was
sample by pressing passed through a cheesecloth
drained and the content of the precipitate was
bag. Percent yield (w/w) was calculated by weigh-
quantitatively transferred to a moisture dish and
ing the juice obtained from pressing the pectinase-
the moisture content measured according to AOAC
treated sample.
(2000). WHC of crude pectin was expressed as
Sample pH was measured with a glass-
o
gram of water held per gram dried sample. All
electrode pH-meter; total soluble solids ( Brix)
experiments were done in triplicate.
were measured with a refractometer (N1 Brix
0~32%, Atago, Tokyo, Japan); and the color was
2. Production of guava juice with enzyme
measured with Hunter Colorimeter (Model
treatment
ColorQuest XT, HunterLab, U.S.A.) using 50 ml
2.1 Guava juice preparation
of juice and expressed in CIE L*, a*, b* values.
Guava fruits (P. guajava L.), variety
From this study, an optimum enzyme concentration
locally known as Pan Seethong with 80-90%
and incubation time were selected for subsequent
maturity, were bought from a local market in Hat
guava juice processing.
Yai, Songkhla province. The fruits were washed
2.3 Guava juice formulation
with tap water and trimmed to remove blemishs
The selected optimum enzyme concen-
then cut in half. Seeds and central seed pulp were
tration and incubation time were used to prepare
removed and the remaining unpeeled flesh was
guava juice in the same manner as described in
cut into small pieces and placed into a juice
2.2. Guava juice was formulated with five differ-
o
extractor. The extracted guava juice and cake were
ent Brix to acid ratios, including 24.0, 28.0, 32.0,
used for further studies.
35.0 and 40.0 as shown in Table 1, pasteurized at
o
o
2.2 Enzyme treatment for juice extract-
85 C for 5 min, cooled and stored at 4 C before
ion
sensory evaluation.
Enzyme treatment to optimize juice
2.4 Sensory Evaluation
production was carried out according to the
A 9-point hedonic scale (Larmond,
o
method described by Brasil et al. (1996) with a
1977) was used to determine which Brix to acid
slight modification. Sample of 40 g and 100 g cake
ratio in guava juice was most liked. Thirty panelists

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
191
Thongsombat, W., et al.
(Prince of Songkla University students) evaluated
gram of anhydrous citric acid per 100 g of sample.
o
guava juice with five different Brix to acid ratios
The color was measured as described above; turb-
as described above. Sensory evaluated attributes
idity was measured using the percent transmission
included: color, turbidity, odor, flavor and overall
at 650 nm with Hunter Colorimeter (Model
acceptability.
ColorQuest XT). 100 ml of juice was poured into
250 ml beaker, allowed to stand for 3 h, 40 ml of
3. Production of guava juice fortified with pectin
the supernatant was transferred to a glass cell, the
as dietary fiber
percent transmittance was determined using water
3.1 Preparation of guava juice fortified
as a blank. Viscosity was measured with Brookfield
with pectin
viscometer (Model DV-II+, U.S.A.) using spindles
o
Crude pectin was obtained from guava
#1 at 15 C.
cake extraction and guava juice was prepared with
3.3 Sensory evaluation of guava juice
selected optimal formulation as described in 1.2
product
and 2.3, respectively. Formulated guava juice was
To evaluate which pectin concentration
added with various amounts of crude pectin
of fortified guava juice was most liked, thirty
contents including 0.00, 0.25, 0.50 and 0.75% (w/
panelists evaluated guava juice products using a
o
w), heated to reach the temperature of 85 C at the
9-point hedonic scale with similar manner as
coldest heating point, immediately filled into 300
described in 2.4. Sensory evaluation attributes
ml glass bottles, capped and pasteurized with a
included: color, turbidity, odor, flavor, mouthfeel
steam water spray automated batch retort (FMC
and overall acceptability.
Food Tech, Belgium) at processing temperature
o
of 101 C for 7 min. Guava juice product was
4. Statistical analyses
measured chemical and physical properties,
All experiments were conducted in duplic-
sensory evaluation was also conducted.
ate. Data in 2.2 were analyzed using two-way
3.2 Measurements of chemical and phy-
analysis of variance (ANOVA). The sensory
sical properties
evaluation data conducted in 2.4 and 3.3 were
The pH and total soluble solids (ºBrix)
analyzed using randomized complete block (panel-
were measured according to the methods as
ists) design with one-way treatment structure. Data
described above. Total acidity was measured using
from 3.2 was analyzed as a completely random-
standard 1% phenolphthalein solution, titrated
ized design. Significant level was established at
against 0.1 N NaOH, the result was expressed as
p<0.05. Duncan's New Multiple Range Test
A: Dried guava press cake
B: Crude pectin powder
(peel, pulp, seeds)
Figure 1. A: Dried guava press cake B: Crude pectin powder produced from dried guava
press cake

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
192
Thongsombat, W., et al.
Table 1. Five different ºBrix to acid ratios of guava juices
Formula
Total soluble
Total acidity
oBrix -
solids (oBrix)
(as % citric acid)
acid ratio
1
12
0.5
24
2
14
0.5
28
3
16
0.5
32
4
14
0.4
35
5
16
0.4
40
Table 2. Chemical and physical properties of crude pectin powder
Chemical properties
Crude pectin**
Physical properties
Crude pectin**
Moisture
4.71±0.18
L*
81.17±0.21
Protein
0.34±0.21
a*
4.76±0.04
Ash
68.48±0.26
b*
15.43±0.07
SDF
20.70±0.16
WHC (g.water/g.solid)
0.90±0.01
pH
3.06±0.02
Bulk density (g/ml)
0.96±0.05
**Determination was done in triplicate
(DMRT) was used to determine significant differ-
pretty close to that of commercial pectin (L* =
ence between treatment means. SPSS for Window
80.57) which reported by Pattanagul et al. (2005).
Version 10.5 was used for all statistical analyses.
The particle size, chemical composition
and structure of dietary fiber influenced the water-
Results and discussion
holding capacity that had a significant effect on
fecal output and stool hardness. The WHC of
1. Extraction and characterization of crude
crude pectin was low (0.90±0.01 g water/g solid),
pectin
3
whereas, bulk density was high (0.96±0.05 g/cm ).
1.1 Chemical and physical properties of
Lario et al. (2003) reported that water holding
crude pectin
capacity depended on fiber production processing
Figure 1 shows dried guava press cake
and also on its chemical and physical structure.
and crude pectin powder from dried guava cake.
The observed yield of crude pectin was 30.50±
2. Production of guava juice with enzyme
0.34% (dried weight basis) that is not shown.
treatment
Chemical and physical properties of crude pectin
2.1 Enzyme treatment for juice extract-
powder are shown in Table 2. From the result,
ion
crude pectin contained 68.48±0.26% (dwb) ash,
The effects of enzyme treatment at
whereas a low protein content of 0.34±0.21%
different enzyme concentrations and incubation
(dwb) was observed. The CIE LAB color was
times are shown in Table 3. As enzyme concent-
studied, the following color coordinate was
rations and incubation times increased, a gradual
determined: lightness (L*), redness (a*, red-green)
o
increase in Brix was observed along with a
and yellowness (b*, yellow-blue) (Lario et al.,
decreased in pH. Similar results were obtained by
2003). L*, a* and b* values of crude pectin were
Imungi et al. (1980), Askar et al. (1992), Brasil et
81.17±0.04, 4.76±0.04 and 15.43±0.07, respect-
al. (1995) and Chopda and Barrett (2001). Pectin-
ively. The observed lightness of crude pectin was
ase enzyme which released carboxylic acids and

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
193
Thongsombat, W., et al.
Table 3. Effects of enzyme concentrations and incubation times on guava juice
Enzyme
Color
Incubation
Concentration
% Yield
pH
oBrix
time (h)
(%)
L*
a*
b*
0
0
67.56±0.31j
4.08±0.03a
9.27±0.24d
64.35±0.60a
2.18±0.08ns
25.23±0.21e
0.05
1.5
70.71±0.42i
3.84±0.03b
10.37±0.14c
33.90±0.58bc
2.10±0.17ns
27.96±0.44c
2.0
74.18±0.15h
3.78±0.02c
10.57±0.15bc 33.51±0.94bc
2.26±0.36ns
27.03±0.60d
2.5
75.42±0.27f
3.74±0.02de 10.78±0.08b
34.36±0.52bc
2.02±0.38ns
26.54±0.50d
0.10
1.5
74.71±0.15g
3.79±0.03c
10.68±0.10b
33.97±0.48bc
2.77±0.29ns
28.98±0.47ab
2.0
77.81±0.36d
3.77±0.02cd 10.78±0.16b
33.66±1.01bc
2.48±0.43ns
29.08±0.74ab
2.5
79.40±0.30b
3.73±0.02ef 11.07±0.21a
34.18±0.56bc
2.03±0.44ns
28.90±0.96ab
0.15
1.5
76.45±0.35e
3.77±0.03cd 10.68±0.08b
33.67±0.62bc
2.42±0.46ns
28.51±0.61abc
2.0
78.56±0.34c
3.73±0.02ef 10.78±0.19b
31.78±0.99d
2.80±0.82ns
29.20±0.93a
2.5
79.89±0.24a
3.70±0.03f
11.18±0.13a
33.36±0.64bc
2.33±0.28ns
29.23±0.56a
Means ± standard deviation in each column with the same letters are not significantly different (p > 0.05)
o
galacturonic acid during enzyme treatment might
acceptability of guava juice with Brix to acid ratio
contribute to a decrease in pH of guava press cake
of 40 were significant greater than those of guava
o
sample (El-Zoghbi et al., 1992).
juice with Brix to acid ratios of 24, 28, 32 and
The %yield of guava juice increased,
35. It also noted that perceived likeness scores
with increasing of pectinase concentrations and
for all attributes shown in Table 4 were in the
incubation times. Chopda and Barrett (2001)
range of like moderately to like slightly. Moreover,
o
reported that pectinase assisted in pectin hydro-
commercial guava juice contained the Brix to
lysis, which caused a reduction in pulp viscosity
acid ratio ranged from 37 to 45. This study also
o
and a significant increased in juice yield. Yields
pointed out that guava juice with the Brix to acid
of cloudy juice were significantly affected by
ratio of 40 was significantly greatest preferred in
o
temperature and time used for enzyme treatments.
the overall acceptance. Therefore, 40 Brix to acid
The results also showed that significantly high
ratio was selected for subsequent guava juice
yields of guava juice were obtained using 0.15%
processing.
pectinase concentration incubated for 2.5 h, how-
ever, the enzyme treatment of 0.10% pectinase
3. Production of guava juice fortified with
concentration incubated for 2.5 h was found to be
dietary fiber
the best suit for commercial application, regarding
3.1 Chemical and physical properties of
to the efficiency and its cost-effective. Therefore,
guava juice fortified with pectin
the selected optimum pectinase concentration and
Table 5 shows the results of chemical
incubation time for juice processing were 0.10%
and physical properties of guava juice fortified
and 2.5 h, respectively.
with pectin. It was found that the greater the pectin
2.2 Sensory Evaluation
was added (0, 0.25, 0.5, 0.75%) the lower the pH
Table 4 shows the results of sensory
and % transmittance were obtained. In contrary to
evaluation of guava juice with five different ºBrix
the total acidity and viscosity of fortified guava
to acid ratios. The perceived scores of color
juice. This may be due to the hydrolysis of guava
o
attributes from the Brix to acid ratios of 24, 32,
pectin occuring during juice processing. Wilson
35 were significantly (p<0.05) less than those
(1980) reported that hydrolyzed guava pectin
o
from Brix to acid ratios of 28 and 40. The like-
contained 72% D-galacturonic acid, 12% D-
ness scores for turbidity, odor, flavor and overall
galactose and 4% L-arabinose. The greater the

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
194
Thongsombat, W., et al.
Table 4. Sensory evaluation of guava juice with different ºBrix to acid ratio
o
Sensory attributes
Total soluble
Total acidity
Brix
Formula
solids (ºBrix)
(as % citric
to acid
Color
Turbidity
Odor
Flavor
Overall
acid)
ratio
acceptability
1
12
0.5
24
7.03±0.85b 6.57±0.90b 6.37±1.00c 5.93±1.23d 6.13±1.01c
2
14
0.5
28
7.27±0.83a 6.53±1.04b 6.57±0.97bc 6.43±0.97c 6.63±0.96b
3
16
0.5
32
7.07±1.01b 6.63±1.16b 6.67±0.84b 7.07±0.87ab 6.80±0.85b
4
14
0.4
35
7.10±0.76b 6.63±0.93b 6.50±0.68bc 6.93±0.91b 6.80±0.92b
5
16
0.4
40
7.30±0.79a 6.87±0.82a 6.80±0.71a
7.17±1.05a
7.30±0.65a
Means ± standard deviation in each column with the same letters are not significantly different (p > 0.05)
Table 5. Chemical and physical properties of fortified guava juice
Chemical and physical properties of guava juice
Pectin
(%)
pH
oBrix
Total
L*
a*
b*
%Transmittance
Viscosity
acidity (%)
(650 nm.)
(Cps.)
0
4.30±0.06a
15.80±0.37a
0.40±0.01d
24.15±1.08c
0.47±0.29b
34.17±0.59b
24.33±1.01a
14.68±0.36d
0.25
4.23±0.03b
15.50±0.15ab 0.47±0.01c
26.34±0.32a
0.18±0.03c
35.82±0.21a
22.65±0.74b
17.48±0.32c
0.50
4.20±0.05bc
15.27±0.16b
0.56±0.01b 25.69±1.07ab
0.74±0.09a 35.52 ±0.52a
22.82±0.48b
21.90±0.77b
0.75
4.14±0.04c
15.27±0.55b
0.63±0.02a 25.04±0.79bc
0.77±0.14a
35.44±0.53a
19.44±0.51c
25.32±1.37a
Means ± standard deviation in each column with the same letters are not significantly different (p > 0.05)
amount of D-galacturonic acid, the lower the pH
guava juices were more green, more red and lighter
was observed. Contrary to the pH, the greater the
than the control.
total acidity was obtained. In addition, decreasing
3.2 Sensory evaluation of fortified guava
the ratio of dissociated to nondissociated acid
juice
groups by lowering the pH rendered pectin mole-
Table 6 shows the sensory evaluation
cules reducing in hydrophilic portions, contribut-
of fortified guava juice. The sensory attributes
ing to great tendency to form gels which paid a
including color, turbidity, odor, flavor, mouthfeel
major role in increasing the viscosity of guava
and overall acceptability were evaluated by 30
juice (Wang et al., 2002). The ºBrix of fortified
panelists. It was found that the greater the amounts
juice was less than that of the control. The L*
of crude pectin were added, the less the perceived
(lightness, L* = 25.04-26.34) and b* values
scores in almost all attributes were observed.
(yellowness, yellow to blue, b* = 35.44-35.82) of
Therefore, the amount of 0.25% crude pectin was
fortified guava juice were significantly different
selected for subsequent guava juice processing. As
than those of the control (L* = 24.15, b* = 34.17).
compared to the control (0% pectin), the results
The a* value (redness, red to green) of 0.25%
pointed out that guava juice fortified with 0.25%
pectin fortified guava juice was significantly less
crude pectin was not significantly different (p>
than that of the control. Whereas the 0.50 and
0.05) in the observed percieved scores of sensory
0.75% pectin fortified guava juices had the a*
attributes including color, flavor, mouthfeel and
values greater than that of control. The results
overall acceptability. Whereas the percieved scores
pointed out that 0.50%-0.75% pectin fortified
in turbidity and odor attributes were less signi-

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
195
Thongsombat, W., et al.
Table 6. Sensory evaluation of fortified guava juice
Sensory attributes
Treatment
Pectin (%)
Color
Turbidity
Odor
Flavor
Mouthfeel
Overall
acceptability
1
0
7.47±0.51a
7.13±0.57a
7.07±0.78a
7.27±0.78a
7.13±0.68a
7.27±0.74a
2
0.25
7.40±0.68a
6.90±0.71b
6.27±0.74b
7.33±0.66a
7.17±0.53a
7.23±0.57a
3
0.50
7.30±0.65a
6.90±0.66b
6.03±0.81c
6.63±0.56b
6.90±0.61b
6.67±0.48b
4
0.75
6.80±0.76b
6.80±0.66b
5.67±1.09d
6.77±0.86b
6.80±0.71b
6.53±0.68b
Means ± standard deviation in each column with the same letters are not significantly different (p > 0.05)
Figure 2. A: Guava juice without crude pectin fortification, B: Guava juice fortified with
crude pectin
ficantly different (p<0.05) than those of the control.
was achieved. The optimum conditions for guava
This may be due to most panelists preferred natural
juice extraction were 0.10% v/v pectinase con-
o
aroma flavor of guava juice significantly greater
centration and incubation time of 2 h at 45 C.
than those of guava juice fortified with crude
It was found that guava juice processing was
o
guava pectin. Crude pectin added into guava juice
optimized at the Brix to acid ratio of 40, followed
influenced on the likeness in flavor of fortified
by the addition of 0.25% crude pectin (soluble
o
guava juice. Figure 2 shows guava juice without
dietary fiber), and pasteurization at 110 C for 7
crude pectin fortification and guava juice fortified
min. As compared to guava juice without the
with crude pectin.
addition of crude pectin (control), there was no
significant difference in perceived sensory scores
Conclusions
from almost all evaluated attributes except the
turbidity and odor attributes. This study also
Pectin extraction from commercial guava
suggests that the process of deodorization may be
cake was performed and 30.50±0.34% yield of
needed for further commercial guava pectin
crude guava pectin containing 20.70±0.16% SDF
production and utilization.

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Songklanakarin J. Sci. Technol.
Production of guava juice fortified with dietary fiber
Vol.29 (Suppl. 1), March 2007 : Thai Herbs II
196
Thongsombat, W., et al.
Acknowledgments
Jimenez-Escrig, A., Rincom, M., Pulido, R.and Saura-
Calixto, F. 2001. Guava fruit (Psidium guajava
The authors would like to express their
L.) as a new source of antioxidant dietary fiber.
sincere thanks to Faculty of Agro-Industry, Prince
J. Agr. Food Chem. 49: 5489-5493.
of Songkla University for supporting research fund
Kashyap, D.R., Vohra, P.K., Chopra, S. and Tewari, R.
under the excellence in Agro-Industry scholarship.
2001. Application of pectinase in the commer-
cial sector: a review. Bioresource Technol. 77:
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