Effect of germination on total dietary fibre and total sugar in selected legumes

Abstract

Legume is a plant in the family of Fabaceae (or Leguminosae) that is cultivated and consumed throughout the world. Legume's role in human health appears to be limited because of several limiting factors such as low protein and starch digestibility, poor mineral bioavailability and high antinutritional factors. Germination is defined as a process that occurs during seed growth that starts with uptake of water until the emergence of radicle through the surrounding structure. It has been suggested that germination is a cheaper and more effective technology that can improve the quality of legumes by increasing their nutritional value. This study was conducted to compare changes in dietary fibre and total sugar compositions after germination process in kidney, mung, soy beans and peanuts. Total dietary fibre was found to be significantly increased (p < 0.05) in all germinated samples, with significant increased (p < 0.05) of soluble and insoluble dietary fibres. For total sugar content, germination increased the level of total sugars. Glucose was the highest available sugar in samples that increased after germination while arabinose was second available sugar that increased in germinated legumes except kidney beans. Overall, germination has improved nutritional properties of legumes in terms of dietary fibre and total sugar content but the changes are influenced by the type of legumes.

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*Corresponding author.
Email: azrinaaz@upm.edu.my
Tel: 603 8947 2466; Fax: 603 8947 2466
International Food Research Journal 23(1): 257-261 (2016)
Journal homepage: http://www.ifrj.upm.edu.my
1Megat, R. M. R., 1,2,3*Azrina, A. and 1,3Norhaizan, M. E.
1Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra
Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2Laboratory of Halal Science Research, Halal Products Research Institute, Universiti Putra
Malaysia, 43400 UPM Serdang, Selangor, Malaysia
3Research Centre of Excellence, Nutrition and Non-Communicable Disease, Faculty of Medicine
and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
Effect of germination on total dietary bre and total sugar in selected
legumes
Abstract
Legume is a plant in the family of Fabaceae (or Leguminosae) that is cultivated and consumed
throughout the world. Legume’s role in human health appears to be limited because of several
limiting factors such as low protein and starch digestibility, poor mineral bioavailability and
high antinutritional factors. Germination is dened as a process that occurs during seed growth
that starts with uptake of water until the emergence of radicle through the surrounding structure.
It has been suggested that germination is a cheaper and more effective technology that can
improve the quality of legumes by increasing their nutritional value. This study was conducted
to compare changes in dietary bre and total sugar compositions after germination process in
kidney, mung, soy beans and peanuts. Total dietary bre was found to be signicantly increased
(p<0.05) in all germinated samples, with signicant increased (p<0.05) of soluble and insoluble
dietary bres. For total sugar content, germination increased the level of total sugars. Glucose
was the highest available sugar in samples that increased after germination while arabinose
was second available sugar that increased in germinated legumes except kidney beans. Overall,
germination has improved nutritional properties of legumes in terms of dietary bre and total
sugar content but the changes are inuenced by the type of legumes.
Introduction
Legume is one of important source of protein,
carbohydrates, dietary bre and oil (Tharanathan and
Mahadevamma, 2003). Several studies have shown
that consumption of legumes was linked to reduce risk
of cardiovascular disease, coronary heart disease and
diabetes, as well as lowering the cholesterol levels
(Jang et al., 2001; Khattak et al., 2007; Nöthlings
et al., 2008; Carbonaro, 2011). However, there are
several limiting factors such as low protein and starch
digestibility, poor mineral bioavailability and high
antinutritional factors (Ghavidel and Prakash, 2007;
Khattak et al., 2007; Fernandez-Orozco et al., 2008).
These limiting factors can be reduced by several
preparation techniques such as cooking, soaking,
dehulling and germination.
Germination is a process occurred during growth
period that starts with the uptake of water by the
dry seed and nished with the emergence of radical
(Vidal-Valverde et al., 2002). During this period,
storage components in seeds are degraded, use for
respiration and production of new cells to develop
new embryo (Hussein and Ghanem, 1999). Studies
show that germination can increase protein and
dietary ber, reduce tannin and phytic acid contents
and increase mineral bioavailability (Hussein
and Ghanem, 1999; Ghavidel and Prakash, 2007;
Khandelwal et al., 2010). Germination also was
reported to be associated with increase of vitamin
concentrations and bioavailability of trace elements
and minerals (El-Adawy et al., 2004; Khattak et al.,
2007; Kaushik et al., 2010).
This study uses kidney, mung, soy bean and
peanut as samples as these legumes are the most
consumed by Malaysians (APO, 2003). Peanuts are
mainly used in local dishes, as well as being processed
and produced as oil, peanut butter and margarine.
Soy beans are often being used as beverages while
other products such fermented soy bean cake, soy
bean curd and sauce are consumed as side dishes.
Mung beans can either be cooked or sprouted while
the dried beans are prepared as soup or snacks similar
as the kidney beans.
The aim of this study was to compare the effect
of germination on bre and sugar compositions
of legumes. It is hope that this study will provide
Keywords
Germination
Legume
Kidney bean
Mung bean
Soy bean
Peanut
Dietary bre
Total sugar
Article history
Received: 20 January 2015
Received in revised form:
29 April 2015
Accepted: 18 June 2015

258 Megat et al./IFRJ 23(1): 257-261
additional data on nutritional contents of germinated
and non-germinated legumes for further research in
future as well as developing new and improved food
functional ingredient in the market.
Materials and Methods
Samples
Dried kidney, mung, soy bean and peanut were
purchased from hypermarkets in Seri Kembangan,
Selangor, Malaysia. Legumes were stored in
refrigerator at 4°C before germination.
Germination
Legume samples were washed with 70% ethanol
for 2.5 min before further washed with sodium
hypochlorite for 15 minutes at room temperature.
Then, the samples were rinsed thoroughly until the
pH becomes neutral before being soaked in distilled
water for 6 hours. Later, the water was drained and
samples were left to germinate on wet muslin cloth
until the emergence of radical at maximum 5 mm.
After germination, legume samples were dried in
oven at 105°C and ground prior to analyses.
Total sugar analysis
Sample was vacuum evaporated to dryness and
concentrated sugars were redissolved in deionised
water and sonicated before ltered using Whatman
41 paper. Aliquot of 2 ml of ltrate was mixed with
acetonitrile and ltered through a 0.54 µm Millex
membrane prior to injection. Soluble carbohydrates
were determined by HPLC using amino bonded
column (250 mm x 4.6 mm x 5 µm), isocratic
pump and refractive index detector. A mixture of
acetonitrile:water (75:25; v/v) was used as a mobile
phase with a ow rate of 1 ml/min. A mixture of
carbohydrate standards at a concentration ranging
from 2 to 10 mg/ml containing erythrose, rhamnose,
mannose, arabinose, xylose, fructose, glucose, and
galactose was used for monosaccharide identication
and quantication (Yang et al., 2008).
Total dietary bre analysis
Legume samples (1.0 ± 0.1 g) were digested
with α-amylase (0.1 ml), protease (0.1 ml) and
amyloglucosidase (0.3 ml) in a beaker. Heated (60°C)
95% ethanol was added and the solution was left
precipitated at room temperature overnight. Digested
samples were ltrated using Fibertec machine.
Crucibles containing residues from ltration was
dried and weighed. The procedure was repeated to
obtain insoluble dietary bre percentage and hence,
soluble dietary bre percentage (Prosky et al., 1988).
Statistical analysis
Every measurement of samples was in triplicate
to obtain higher precision of data. Data was analyzed
using SPSS software version 16.0. Paired T-test
was used to compare between non-germinated
and germinated legumes. Data was considered as
signicant when p value < 0.05.
Results and Discussion
Total sugar content
Total sugar was found to increase in all germinated
legume samples. In germinated kidney beans, total
sugar increased from 118.46 to 134.75 g/kg d.w. while
in germinated mung beans, it was increased from
122.07 g/kg d.w. to 157.4 g/kg d.w. For soy beans,
germination caused total sugar to increase from
157.53 g/kg d.w. to 194.86 g/kg d.w. and for peanuts,
germination increased total sugar from 118.61 g/kg
d.w. to 160.42 g/kg d.w. Comparison of all legume
samples, the most dominant available carbohydrate
was glucose and arabinose. After germination,
glucose was increased in most samples except mung
beans (decreased) while for arabinose, germination
caused this sugar to reduce in the samples.
Urbano et al. (2005) suggested that germination
process caused the metabolic changes in legume seeds
in which carbohydrate storage in the form of starch
and oligosaccharides were hydrolysed and caused
the increase of sugar levels. Furthermore, Martin-
Cabrejas et al. (2008) also suggested that during
germination, α-galactosidase activity was increased,
causing the break of α-1,6-galatosidic linkages and
thus, increase the amount of total sugar.
Total dietary bre content
Total dietary bre (TDF) was signicantly
increased (p < 0.05) in all legumes after germination. In
germinated kidney beans, TDF increased signicantly
(p < 0.05) from 36.6% to 59.9% while in germinated
mung beans, the TDF increased signicantly from
28.5% to 32.0%. TDF in soy beans increased
signicantly from 32.0% to 72.5% after germination,
while in peanuts; germination signicantly increased
TDF percentage from 21.6% to 39.9%. Among the
samples, germination signicantly increased (p <
0.05) soluble dietary bre (SDF) content. In kidney
beans, SDF was signicantly increased from 3.9%
to 6.7% after germination while in mung beans; the
SDF was signicantly increased from 3.7% to 5.8%.
In soy beans, germination signicantly increased
SDF from 8.2% to 17.4% while in peanuts, SDF was
signicantly increased from 5.5% to 9.1%. Similarly,
germination caused insoluble dietary bre (IDF) to

Megat et al./IFRJ 23(1): 257-261 259
increase in the studied samples. In kidney beans, IDF
was signicantly increased (p < 0.05) from 32.7% to
53.3% while in mung beans; the value was increased
from 24.8% to 26.2%. Signicant IDF increment was
found in soy beans from 23.8% to 55.1% while in
germinated peanuts, IDF was signicantly increased
from 16.0% to 30.8%.
Martin-Cabrejas et al. (2003) found that total
dietary bre content was increased after germination
in daylight and without daylight. They also found
that IDF and SDF bres were also increased after
germination. The result was similar to the current
study where it was found that TDF increased after
germination, alongside insoluble and SDF.
Dietary bre was regarded as one of the most
important ingredient in human diet (Dhingra et
al., 2012). The characteristics of dietary bre
such as particle size, bulk volume, surface area
characteristics, hydration, and adsorption as well as
binding of ions and organic molecules are highly
inuential in human digestive system (Guillon et
al., 1998; Raghavendra et al., 2006; Nassar et al.,
2008; Dhingra et al., 2012). It was observed that
addition of dietary bre components in foods such
as pasta, bakeries and biscuits improved the overall
qualities such as biochemical composition, cooking
properties and textural characteristics as well as the
taste (Tudoric et al., 2002; Sudha et al., 2007; Nassar
et al., 2008). Apart from that, dietary bre can also be
used to improve texture of meat products (Chevance
et al., 2000) as well as functional ingredients in milk
products (Sendra et al., 2008).
Table 1. Sugar proles of germinated and non-germinated legume samples
1 All values are expressed as mean (standard deviation). Total sugar is presented as g/kg dry
weight.
2 (*) indicates signicant change at (p < 0.05).
3 NG: non-germinated; G: germinated.
Table 2. Dietary bre content of germinated and non-germinated legume samples
1 All values are expressed as mean (standard deviation). Total sugar is presented as g/kg
dry weight.
2 (*) indicates signicant changes at (p < 0.05).
3 NG: non-germinated; G: germinated; SDF: soluble dietary bre; IDF: insoluble dietary
bre; TDF: total dietary bre.

260 Megat et al./IFRJ 23(1): 257-261
Martin-Cabrejas et al. (2003) found that TDF
in germinated peas was increased because of the
improved SDF and IDF levels. A different nding
was found by Martin-Cabrejas et al. (2008) in which
TDF was reduced after germination in cowpea, jack
and mucuna beans. Similarly, in germinated dolichos
and soy beans, total dietary bre was reduced. They
suggested that germination inuenced TDF content
differently according to types of legumes and light
conditions of the germination process. Benitez et
al. (2013) also suggested that the increased of TDF
was due to synthesis of new polysaccharides during
germination.
Conclusion
Total dietary bre was found to be signicantly
increased in all germinated legume samples, with
signicant increase of soluble and insoluble dietary
bres found in all germinated legume samples as
well. For total sugar content, germination caused it
to be increased in all samples. Glucose was found
to be the highest available sugar in all samples and
the value was increased after germination. Arabinose
was the second highest available sugar found in all
legume samples and it was increased in mung, soy
beans and peanuts after germination while in kidney
beans, the value was decreased.
Acknowledgements
This study was nancially supported by the
Research University Grant Scheme (RUGS) (Vote
no. 9199746). The authors would also like to thank
the Department of Nutrition and Dietetics, Faculty of
Medicine and Health Sciences, as well as Department
of Food Science, Faculty of Food Science and
Technology, Universiti Putra Malaysia for granting
permission to carry out this study and providing the
facilities and materials to conduct the research.
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