Available online at http://journal-of-agroalimentary.ro
Journal of
Journal of Agroalimentary Processes and Agroalimentary Processes and
Technologies 2011, 17 (3), 214-217 Technologies
The Effect of Temperature on Soluble Dietary Fiber Fraction
in Cereals
Adrian Căpriţă1*, Rodica Căpriţă1, Vasile Octavian Simulescu2, Raluca Mădălina Drehe2
1
Banat’s University of Agricultural Sciences and Veterinary Medicine, Faculty of Food Processing Technology, Food
Quality Department, 300645-Timişoara, C. Aradului 119, Romania
2
Romanian Academy Institute of Chemistry, 300223-Timişoara, Bd. Mihai Viteazul 24, România
Received: 13 July 2011; Accepted: 11 September 2011
______________________________________________________________________________________
Abstract
Dietary fiber (DF) consists of a mixture of components with a varying degree of solubility. Wheat and
barley contain substantial amounts of both soluble and insoluble DF. Most of food processes are essentially
based on heating for a certain time. Thermal processing of plant tissues alters the physical and chemical
properties of cell wall, and modifies fiber solubilization, which modifies the water extract viscosity (WEV).
The study had in view the effect of temperature on WEV of wheat and barley flours. Thermal treatment at
100ºC produced an increase of WEVs, suggesting a conversion of the insoluble DF into soluble DF. The
increasing of relative viscosity values of water extracts was up to 21.8% for wheat, when heating at 100ºC
for 10 minutes, and up to 29.5% for barley, when heating at 100ºC for 15 minutes. Determinations of
WEVs at different time intervals after extract separation showed that heating the wheat and barley flours at
100°C for 15 minutes deactivated the endogenous hydrolytic enzymes.
Keywords: dietary fiber, wheat, barley, water extract viscosity
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1. Introduction
Food quality is mainly related to the nutritional There are 4 main components of DF: total nonstarch
quality and the effect on consumers’ health. The polysaccharides (NSPs), inulin and fructo-
interest in nutritional and therapeutic properties of oligosaccharides, resistant starch, and lignin. NSPs
food and in the relationship between food and major food sources are cereals and vegetables, which
health is growing every day. Many processed contribute approximately 40% to 50% of the DF.
foods are deprived of some substances having Total NSPs can be classified into water-soluble and
great importance for health, among which the water-insoluble fractions, which delineate their
dietary fiber (DF). DF has beneficial physiological functions and chemical structures [6-9]. NSPs
effects, such as: improving the bulk motility, blood solubility is determined by their primary structure,
cholesterol and glucose decreasing, constipation and by the way they are bound to other cell wall
and cancer preventing, prebiotic acting [1-4]. components. Water-soluble fiber fractions have
opposite effects on water binding capacity and
Dietary fiber is defined as the edible parts of plants
viscosity than the insoluble fractions [10]. The water
or analogous carbohydrates that are resistant to
insoluble fraction includes cellulose,
digestion and absorption in the human small
galactomannans, xylans, xyloglucans, and lignin,
intestine with complete or partial fermentation in
while the water-soluble fibers are the pectins,
the large intestine [5].
arabinogalactans, arabinoxylans, and β-glucans [11].
___________________________________________
Corresponding author: e-mail: adi.caprita@gmail.com
Adrian Căpriţă et. al. / Journal of Agroalimentary Processes and Technologies 2011, 17(3)
β-Glucans are linear polymers of glucose with β- The changes in the DF composition may be attributed
(1,3)(1,4) glycosidic links. Arabinoxylans consist partly to the redistribution of the insoluble and
of long backbone chains of β-(1,4) anhydro-D- soluble components of DF.
xylopyranosyl with single α-L-arabinofuranosyl
The obtained experimental results, presented in Table
residues attached at the 2- or 3-position [12].
1, show the effect of thermal treatment on the soluble
Almost all water-soluble polysaccharides produce fraction of DF, effect revealed by the determined
viscous solutions. The viscous properties of DF are values of the water extract viscosities. The relative
determined by several factors, including their viscosity values of water extracts from untreated
chemical composition, molecular size, and samples were 2.57 cP for wheat, and 2.95 cP for
composition of the extraction media. Wheat and barley.
barley contain substantial amounts of both soluble
and insoluble DF. The predominant water soluble Thermal treatment at 100ºC produced an increase of
DF in wheat is arabinoxylan (6-8%), while β- water extracts viscosities. The proportion of soluble
glucan is the predominant water soluble DF in DF from total DF increased, suggesting a conversion
barley (7.6%). Most of food processes are of the insoluble DF into soluble DF. An increased
essentially based on heating for a certain time, and temperature breaks weak bonds between
thermal processing of plant tissues alters the polysaccharide chains and split glycosidic linkages in
physical and chemical properties of plant cell wall the DF polysaccharides [13]. As consequence, the
and modifies fiber solubilization, which modifies architecture of the fiber matrix may be modified and
the water extract viscosity (WEV). The study had insoluble fiber solubilized [14].
in view the effect of temperature on WEV of The relative viscosity values of water extracts from
wheat and barley flours. wheat increased up to 3.13 cP (21.8% increasing)
2. Materials and Method when heating at 100ºC for 10 minutes. The relative
viscosity values of water extracts from barley
The effect of temperature on WEV (which is increased up to 3.82 cP (29.5% increasing) when
correlated with the soluble DF content) obtained heating at 100ºC for 15 minutes (Figure 1).
from wheat and barley flours was determined.
5
The influence of the time elapsed after extract 4.5
separation on WEV was also determined. cP
4
Wheat and barley samples were milled to 500 µm 3.5
3
granulation, and heated for 5, 10 and 15 minutes at 2.5
100ºC in a Froilabo AC60 forced air oven. 2
The water-soluble fractions were obtained by a 1.5
1
single extraction at a ratio 1/2 (flour/water), by 0.5
shaking the tubes at 150 rpm, for 60 minutes at 0
40ºC, using a LabTech LSB-015S water bath. 0 5 10 15
wheat barley minutes
The extracts were centrifuged for 10 minutes at
5,000 rpm and 25°C, using a Hettich 320R
Figure 1. Relative viscosity values of water extracts from
centrifuge.The dynamic viscosity was determined wheat and barley flours heated at 100ºC for 5, 10 and 15
using a cone/plate viscometer Brookfield Model minutes
DVIII Cone CP-40, at 100 rpm and 25°C,
immediately after separation, and at 30 and 60 Determinations of WEVs at different time intervals
minutes after centrifugation. The relative viscosity elapsed after extract separation, show that heating the
was calculated. wheat and barley flours at 100°C for 15 minutes
deactivated the endogenous hydrolytic enzymes. No
3. Results and Discussion significant decrease of WEV values with the time
Thermal treatment of plant tissues modifies the elapsed after extract separation was observed
physical and chemical properties of plant cell wall, (Figures 2 and 3).
and experimental data reveal the increasing of the
soluble DF fraction in wheat and barley.
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Adrian Căpriţă et. al. / Journal of Agroalimentary Processes and Technologies 2011, 17(3)
Table 1. WEV of wheat and barley flours heated at 100ºC
Sample Heating time Time after Dynamic viscosity Relative
(minutes) centrifugation (cP) viscosity
(minutes) (cP)
Wheat 5 0 2.30 2.77
30 1.86 2.24
60 1.60 2.05
10 0 2.60 3,13
30 1.96 2.51
60 1.78 2.28
15 0 2.36 2.86
30 2.08 2.66
60 1.98 2.53
Barley 5 0 2.52 3.03
30 2.30 2.77
60 1.92 2.46
10 0 3.01 3.62
30 2.84 3.42
60 2.44 3.12
15 0 3.02 3.82
30 2.99 3.67
60 2.90 3.60
4 4
cP 3.5 cP 3.5
3
3
2.5
2.5
2 2
1.5 1.5
1 1
0.5 0.5
0 0
0 5 10 15 0 5 10 15
minutes 0 30 60 minutes
0 30 60
Figure 3. WEVs of the barley samples heated at 100°C,
Figure 2. WEVs of the wheat samples heated at 100°C,
at different times after centrifugation of the extract
at different times after centrifugation of the extract
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4. Conclusions 6. Chawla, R.; Patil, G.R., Soluble dietary fiber,
Comprehensive Reviews in Food Science and Food
Thermal treatment of wheat and barley flours at Safety 2010, 9(2), 178–196, doi: 10.1111/j.1541-
100ºC produced an increase of water extracts 4337.2009.00099.x
viscosities, suggesting a conversion of the insoluble 7. Sasaki, T., Effect of water-soluble and insoluble
dietary fiber into soluble dietary fiber. non-starch polysaccharides isolated from wheat flour
on the rheological properties of wheat starch gel,
The increasing of relative viscosity values of water Carbohydrate Polymers 2004, 57(4), 451-458,
extracts was up to 21.8% for wheat, when heated at doi:10.1016/j.carbpol.2004.06.004
100ºC for 10 minutes, and up to 29.5% for barley, 8. Izydorczyk, M.S.; Biliaderis, C.G.; Bushuk, W.,
when heated at 100ºC for 15 minutes. Comparison of the structure and composition of
water-soluble pentosans from different wheat
Heating the wheat and barley flours at 100°C for 15 varieties, Cereal Chemistry 1991, 68(2), 145-150.
minutes deactivated the endogenous hydrolytic 9. Izydorczyk, M.S.; Macri, L.J.; MacGregor, A.W.,
enzymes, so no significant decrease of WEV values Structure and physicochemical properties of barley
with the time elapsed after extract separation was non-starch polysaccharides. I. Water-extractable β-
observed. glucans and arabinoxylans, Carbohydrate Polymers
1998, 35(3-4), 249-258, doi:10.1016/S0144-
Acknowledgements
8617(97)00137-9
This work was supported by CNCSIS–UEFISCSU,
10. Sasaki, T.; Yasui, T.; Matsuki, J., Effects of amylose
project number 1055/2009 PNII–IDEI code 898/2008
content on gelatinization, retrogradation, and pasting
References properties of starches from waxy and nonwaxy
wheat and their F1 seeds, Cereal Chemistry 2000,
1. Thomson, P., White breads can also be high fiber,
77(1), 58-63, doi: 10.1094/CCHEM.2000.77.1.58
Wellness Foods Europe, 2005, 34, 30-33.
11. Johnson, I.T., New food components and
2. Shrivastva, S.; Goyal, G.K., Therapeutic benefits of
gastrointestinal health, Proceedings of the Nutrition
pro and prebiotics: a review, Indian Food Industry
Society 2001, 60, 481-488,
2007, 26(2), 41-49.
doi:10.1079/PNS2001106
3. Caprita, A.; Caprita, R.; Simulescu, V.O.; Drehe,
12. Lineback, D.R.; Rasper, V.F., Wheat Carbohydrates,
R.M., Dietary fiber: chemical and functional
In: Wheat: Chemistry and Technology, vol. 1,
properties, Journal of Agroalimentary Processes and
Pomeranz, Y. (ed.), Am. Assoc. Cereal Chem., St.
Technologies 2010, 16(4), 406-410.
Paul, 1998, 277-371.
4. Viuda-Martos, M.; Lopez-Marcos, M.C.; Fernandez-
13. Selvendran, R.R.; Robertson, J.A., Dietary Fiber in
Lopez, J.; Sendra, E.; Lopez-Vargas, J.H.; Perez-
Foods: Amount And Type, In: COST-92, Metabolic
Alvarez, J.A., Role of fiber in cardiovascular
and Physiological Aspects of Dietary Fiber in Food,
diseases: a review, Comprehensive Reviews in Food
Amado, R. et al. (eds.), Commision of the European
Science and Food Safety 2010, 9(2), 240-258, doi:
Communities, Luxembourg, 1994, 11-19.
http://dx.doi.org/10.1111/j.1541-4337.2009.00102.x.
14. Margareta, E.; Nyman, G.-L., Importance of
5. Tungland, B.C.; Meyer, D., Non-digestible oligo-
processing for physico-chemical and physiological
and polysaccharides (dietary fiber): their physiology
properties of dietary fibre, Proceedings of the
and role in human health and food, Comprehensive
Nutrition Society 2003, 62, 187-192,
Reviews in Food Science and Food Safety, 2002
doi:10.1079/PNS2002227
1(3), 73–77, doi:10.1111/j.1541-
4337.2002.tb00009.x
217