Production of inulin and high-fructose syrup from Jerusalem artichoke tuber (Helianthus tuberosus L.)

Full text

417
Annals
Agric. Sci.,
Ain Shams Univ.,
Cairo, 54(2), 417- 423, 2009
(Received October 15, 2009)
(Accepted October 22 , 2009)
PRODUCTION OF INULIN AND HIGH-FRUCTOSE SYRUP FROM
JERUSALEM ARTICHOKE TUBER (Helianthus tuberosus L.)
[32]
Safaa, S. Abozed
1
; A. Abdelrashid
2
; M. El-kalyoubi
2
and K.I. Hamad
1
1- Food Technology Dept., National Research Center, Dokki, Giza, Egypt
2- Food Science Dept., Faculty of Agric., Ain Shams Univ., Shoubra El-Kheima, Cairo, Egypt
Keywords: Helianthus tuberosus, Inulin extraction,
Acid hydrolysis, High-fructose syrup
ABSTRACT
Jerusalem artichoke (Helianthus tuberosus L.)
has been reported to have one of the highest car-
bohydrates yield. The main carbohydrate compo-
nent in Jerusalem artichoke tubers is inulin, with
high fructose content (about 94%). Inulin is a fruc-
tose polymer which has been widely investigated
for the production of high-fructose syrup by acid or
enzymatic hydrolysis. In this work, a process opti-
mization study to extract of inulin at different tem-
peratures, time and solvent solid ratio were used.
The optimal conditions for maximum inulin extrac-
tion yield were (68.70 %) at 85°C, 60min and water
solid ratios 1:20 (v/w). Precipitation of inulin by four
solvents (ethanol, propanol, acetone and acetoni-
trile) at different ratio 1:1, 2:1, 3:1 and 4:1(solvent:
supernatant v/v) were studied. Inulin precipitation
by ethanol and acetone were more than that oc-
curred using acetonitrile or propanol. The influence
of pH, type of acid, temperature and time on hydro-
lysis of inulin were investigated. The complete hy-
drolysis of the inulin was attained at pH 2.0, ad-
justed with sulphuric acid after 90min at 100°C.
INTRODUCTION
Helianthus tuberosus L. (Asteraceae), a peren-
nial plant commonly known as the Jerusalem arti-
choke. The tubers of H. tuberosus have been uti-
lized not only as a food but also as a raw material
in the bioethanol industry for its high content of
inulin, a fructan that can be easily hydrolyzed (Pan
et al 2009). Inulin acts as a dietary fiber, contribut-
ing to the growth of bifidobacteria and to the im-
provement of the overall conditions in the human
gastrointestinal (Ritsema and Smeekens, 2003).
Food and pharmaceutical industries have found
applications for inulin in the production of function-
al foods, nutritional composites and medicines.
The most stable form for the commercialization of
inulin is the powdered extract. This type of product
has more advantages for its greater facility of ma-
nipulation, transport, storage and consumption
(Molina et al 2005).
The application of inulin in the food industry, at
first, was restricted to the production of drinks simi-
lar to coffee, for its bitter taste. However, it was
recently discovered that the inulin could act as a
substitute for sugar or fat due to its very low caloric
value (Van Loo et al 1995). So, inulin was used as
an ingredient in foods with reduced or no sugar
and fat, such as chocolates, ice creams and yog-
hurts, among others also. Also, it was used in low
caloric foods, reduced fat levels, and so source of
dietary fibers, contributing to the improvement of
the gastrointestinal system conditions (Figueira et
al 2004).
Inulin is a polysaccharide, with high fructose
content reaching 94% (Saengthongpinit and Saj-
jaanantakul, 2005). High fructose syrup is a swee-
tener found in numerous foods and beverages
(starting from bread to pasta sauces to bacon to
beer) as sugar substitute because of its high quali-
ty characteristics and stability easy to store (Zhang

Safaa Abozed; Abdelrashid; El-kalyoubi and Hamad
Annals Agric. Sci., 54(2), 2009
418
et al 2004 and Rocha et al 2006). High fructose
syrup can be produced by the hydrolysis of a natu-
ral occurring fructan, inulin, which is a polymer of
β-(21) linked fructose, to yield 95% fructose.
(Barta, 1993).
The aim of this investigation was to develop a
set of optimum extraction conditions for Jerusalem
artichoke tubers in order to improving inulin extrac-
tion yield. Based on previous work, temperature,
extraction period and solvent: solid ratio were con-
sidered to be important factors affecting the extrac-
tion yield, and precipitate inulin by different con-
centrations of ethanol, acetonitril,acetone and pro-
panol. Furthermore, inulin utilization for production
of high fructose syrup by some parameters of inulin
hydrolysis was tested to obtain the highest reduc-
ing sugars yield from the selected tubers.
MATERIALS AND METHODS
Material
Jerusalem artichoke tuber (Helianthus tubero-
sus L.) was purchased from the Agriculture Re-
search Center, Dokki, Giza. , Egypt.
Methods
Jerusalem artichoke tubers were washed with
tap water and any deteriorated parts were re-
moved, than the tubers were sliced in dividedly to
the reasonable thickness by a conventional food
slicing machine. The sliced tubers were immersed
immediately in boiling water for 5 min, following by
immediate dipping in cold acetic acid solution (2%)
to inhibit polyphenoloxidase activity Tchone et al
(2005). After that the slices of tuber were dried in
electronic air oven (SHEL LAB 1370FX SHELDON
MANUFACTURI Ng, 1NC) at 60-70°C until sam-
ples reached constant weight.
Chemical composition
Proximate chemical compositions were deter-
mined in dried powdered tubers according to
A.O.A.C. (2000). Inulin was measured by using the
method of Witon and Witon (1958).
Inulin extraction
The extraction of inulin was carried out using
hot water according to Lingyun et al (2007) me-
thod. The dried powdered tubers were mixed with
water at different percentage of powder tubers /
water ratio i.e., 1:2.5, 1:5, 1:10, 1:15 and 1:20
(W/V) at different temperatures 65, 75, 85 and
95°C as well as for different periods 40, 50, 60 and
70 min.
Inulin precipitate
Inulin was precipitated according to Ku et al
(2003) method. Four different solvents (ethanol,
propanol, acetone and acetonitrile) were used at
different ratios of solvent to test sample as follows
(1:1, 2:1, 3:1 and 4:1, v/v). The inulin powder was
analyzed from moisture, ash, fat, and reducing
sugar as the method described in the A.O.A.C.
(2000).
High fructose syrup production
Sulphuric and hydrochloric acids were used to
adjust the pH of the inulin extract to 2.0, 2.5 and
3.0 for each acid. The samples were heated at 60°
C, 80°C and 100°C. The effect of hydrolysis was
followed by assaying reducing sugars increase
after 60 and 90 min for each pH, acid and tem-
perature, however, reducing sugars were esti-
mated according to A.O.A.C. (2000).The product
was decolorized with activated granular charcoal,
after that the liquid was passed through Dowex 66
and concentrated by rotary evaporation to pro-
duced high fructose syrup.
Statistically analysis
The mean values of the all obtained results
were statistically analysis. Evaluated by one-way
analysis of variance (ANOVA) and least significant
difference at 0.05 % level of probability using PC–
Stat Version IA procedures (PC- Stat, 1985).
RESULTS AND DISCUSSION
Chemical composition
Proximate chemical composition of Jerusa-
lem artichoke tubers are summarizes on dry weigh
basis as shown in Table (1). The tuber contained
6.17, 6.20, 0.58, 5.33, 2.72, 79.01 and 72.18 %
moisture, protein, fat, ash, crude fiber, total carbo-
hydrate and inulin content, respectively. These
indicate that a Jerusalem artichoke tuber was
found to be higher content of total carbohydrate
and a good source for inulin (Barta, 1993).

Production of inulin and high-fructose syrup
Annals Agric. Sci., 54(2), 2009
419
Table 1. Proximate chemical composition of
Jerusalem artichoke tuber (g/100g on
dry weight basis %)
Constituents (%)
Jerusalem artichoke
tuber
Moisture
Crud protein
Crude fat
Ash
Crude fiber
*Total carbohydrate
Inulin
6.17
6.20
0.58
5.33
2.72
79.01
72.18
*Calculated by different
Inulin extract
The effect of using different extraction methods
on % of inulin are shown in Table (2). From the
obtained data, it could be noticed that, the percen-
tage of extractable inulin was significantly in-
creased as a function of increasing solvent to
sample ratio when sample were statistically ana-
lyzed at p ≤ 0.05 .
The extraction conditions to recover the highest
yield of inulin were 1:15 for 70 min at 75°C which
produced 63.80 % of inulin, while the extraction
yield at ratio 1: 20 for 60 min at 85°C was 68.71%
of inulin. On the other hand, the extraction process
using ratio 1:10 for 60 min at 95 °C produced
67.77% of inulin. Previous data showed that their
proportion relation between extract of inulin and
extraction period, temperature and water solid ratio
which are agree with Leite et al (2007). The opti-
mum conditions for maximizing inulin extraction
yield (68.71 %) were at natural pH for 60min. at
85°C and water solid ratio of 1:20 (v/w).
Inulin precipitate
The weigh percent of inulin (g/100g) precipi-
tated using the four presentation agents at different
ratios are listed in Table (3). In general, the weight
percent of precipitation by ethanol was the highest
one among other solvents and the inulin precipitate
increased significantly with increasing solvent ratio.
In addition, the table cleared that ethanol and ace-
tone were the best agents to precipitate the inulin
from the tuber, however, the precipitation percents
were 70.25 and 68.87, respectively. On this re-
gard, Ku et al (2003) reported that acetone is the
potent solvent for precipitation of inulin.
Chemical composition of precipitated inulin
Table (4) showed that the chemical composi-
tion of inulin precipitate was 3.77, 1.59, 0.39, 95.12
and 1.67 % of moisture, ash, fat, inulin and reduc-
ing sugar content respectively these results are an
agreement with that observed by Saengthongpinit
and Sajjaanantakul (2005).
High fructose syrup production
In this manner, the acid hydrolysis was carried
out using different four parameters: acid, pH, tem-
perature and hydrolysis period, Table (5). From
this table it had been shown that the content of
reducing sugars was increased with time increase
at different acid, pH values and temperatures.
Furthermore, obtained results proved that pH value
of 2.0 adjusted with sulphuric acid gave the best
results after 60 or 90 min. reaching 81.68 and
83.54 %, respectively, of reducing sugars at 100°C
compared with hydrochloric acid at the same con-
ditions as shown in Table (5).
The presented results have indicated that the
highest of inulin percentage were observed by acid
hydrolysis at pH 2.0 and 100°C for 90 min. How-
ever, efficiency of inulin conversation to reducing
sugars were obtained using the sulphuric acid as a
hydrolyzing agent (Figure 1) these evidences are
in agreement with that obtained by Szambelan
and Nowak (2006). After filtration, the product was
decolorized with activated granular charcoal, neu-
tralized to pH 6.5-7.0 by passage through anion
exchange resin (Dowex 66), and concentrated to
78.4 % soluble solids by evaporation to produce
high fructose syrup.

Safaa Abozed; Abdelrashid; El-kalyoubi and Hamad
Annals Agric. Sci., 54(2), 2009
420
Table 2. Effect of using different solid / water ratio, and extraction period on the
inulin yield at different temperatures
Solid/water
ratio
(w/v)
Extraction periods (min)
40
50
60
70
65°C
1:2.5
22.08
d
27.17
d
33.88
c
37.54
c
1: 5
23.81
bc
31.14
c
37.92
c
39.38
bc
1:10
25.95
ab
33.27
b
38.15
b
40.29
bc
1:15
28.08
b
34.49
b
43.65
a
43.96
a
1:20
34.19
a
38.45
a
42.73
a
41.51
ab
75°C
1:2.5
42.12
c
47.01
c
49.14
c
52.52
d
1: 5
43.35
c
49.14
bc
51.29
bc
57.69
c
1:10
46.09
b
51.28
ab
53.39
ab
61.97
ab
1:15
50.48
a
54.03
a
56.17
a
63.80
a
1:20
52.19
a
52.19
ab
54.64
a
60.74
b
85°C
1:2.5
60.74
b
61.97
d
61.36
c
62.88
c
1: 5
61.05
b
64.10
c
65.93
b
67.15
ab
1:10
62.88
ab
67.46
a
67.16
ab
68.07±
a
1:15
64.40
a
66.54
ab
68.38
a
66.85
ab
1:20
64.10
a
65.02
bc
68.71
ab
65.02
bc
95°C
1:2.5
61.36
c
62.27
c
60.13
b
61.05
c
1: 5
62.27
bc
63.19
c
66.54
a
65.93
ab
1:10
64.71
a
65.69
bc
67.77
a
67.46
a
1:15
63.79
ab
67.15
a
67.15
a
65.93
ab
1:20
61.97
bc
65.93
bc
65.63
a
64.10
bc
Each value was an average of three determinations
Means which are not significantly different are followed by the same number in column,
Significance level = 0.05)
Table 3. Mean values of weight percent of inulins precipitated using
four agents at different solvent / extract ratios
Solvent / extract
ratio
Inulin weight %( g/100g)
Ethanol
Propanol
Acetone
Acetonitril
1:1
28.34
a
17.49
d
24.03
b
21.15
c
2:1
47.58
a
33.25
d
45.93
b
41.20
c
3:1
62.93
a
48.82
d
60.71
b
54.70
c
4:1
70.25
a
62. 82
d
68.87
b
65.21
c
Each value was an average of three determinations
Means within a row showing the same small letter are not significantly different
(P ≥ 0.05)

Production of inulin and high-fructose syrup
Annals Agric. Sci., 54(2), 2009
421
Table 4. The Chemical composition of precipitated inulin
(g/100g on dry weight basis %)
Constituents (%)
Proximate composition
Moisture
3.77
Ash
1.59
Fat
0.39
Inulin
95.12
Reducing sugar
1.67
Each value was an average of three determinations
Table 5. The reducing sugars content (%) in inulin extract, after hydro-
lysis with different acids for 60 and 90 min at different tem-
perature
pH
acid
Hydrolysis temperatures
60°C
80°C
100°C
Extraction period for 60 min
2.0
Sulphuric
57.51
d
73.73
a
81.68
a
Hydrochloric
41.85
c
52.92
c
71.94
b
2.5
Sulphuric
55.39
b
63.22
d
66.46
c
Hydrochloric
40.39
c
52.36
c
65.04
c
3.0
Sulphuric
39.64
cd
51. 24
c
53.26
d
Hydrochloric
35.47
d
47.66
d
51.47
e
Extraction period for 90 min
2.0
Sulphuric
65.51
a
76.19
a
83.54
a
Hydrochloric
64.73
ab
64.89
c
72.50
b
2.5
Sulphuric
61.73
b
69.43
b
72.23
b
Hydrochloric
59.24
c
62.77
d
62.09
c
3.0
Sulphuric
48.34
d
47.26
f
62.83
c
Hydrochloric
42.67
e
48.20
e
53.82
d
Each value was an average of three determinations
Means witch are not significantly different are followed by the same number in
column, (Significance level = 0.05)

Safaa Abozed; Abdelrashid; El-kalyoubi and Hamad
Annals Agric. Sci., 54(2), 2009
422
0
10
20
30
40
50
60
70
80
90
100
2 2.5 3
pH value
Reducing sugare %
sluphric acid 90min sluphric acid 60min
hydrochloric acid 90min hydrochloric acid 60min
Figure 1. Effect of pH values and different acids on inulin hydrolysis at 100°C
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