The Effect of Accelerated Aging on the Characteristic Properties of Rice Bran
THE EFFECT OF ACCELERATED AGING ON THE
CHARACTERISTIC PROPERTIES OF RICE BRAN
LINGGA HERLAMBANG FEBRIANTO
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015
STATEMENT LETTER OF MANUSCRIPT AND SOURCE OF
INFORMATION*
I declare the truth that this manuscript entitled The Effect of Accelerated
Aging on the Characteristic Properties of Rice Bran is my work with guidance
of the advisors and has not been submitted in any form at any college, except Bogor
Agricultural University and Kasetsart University. Sources of information derived
or quoted from published or unpublished works of other authors mentioned in the
text and listed in the List of References at the end of this manuscript.
Hereby this statement, I bestow the copyright of my manuscript to the Bogor
Agricultural University.
Bogor, January 2015
Lingga Herlambang Febrianto
NIM F24100011
ABSTRACT
LINGGA HERLAMBANG FEBRIANTO. The Effect of Accelerated Aging on the
Characteristic Properties of Rice Bran. Supervised by TJAHJA MUHANDRI and
PINTHIP RUMPAGAPORN.
Accelerated aging process using thermal processing has been reported as an
alternative way to produce aged rice. Rice bran is a by-product of rice production
containing many bioactive compounds, which give beneficial effect to human
health. Effect of accelerated aging on functional properties of rice grain and flour
has already been discussed. However, the consequence of the accelerated aging
technique on the characteristic properties of the rice bran has to be investigated and
verified. Moreover, the investigation of accelerated aging on the rice bran is quite
limited. The objective of this research is to investigate the effect of accelerated
aging using high-temperature fluidized bed drying followed by tempering and
ventilation on the dietary fibre (insoluble and soluble dietary fibre), lipid rancidity,
and antioxidant activity properties of rice bran. Based on the experimental results it
was found that the rice bran properties after accelerated aging process namely,
alcohol-soluble and water-soluble acidity, free fatty acids content, total phenolic
content, and antioxidant activity significantly affected the aged rice bran properties.
The accelerated aging process using high-temperature could decrease acidity and
free fatty acids contents of rice bran oil. Moreover, the accelerated aging was found
to exhibit decreased of total phenolic content and reducing power of rice bran
extracts. The reducing power of rice bran extracts were associated with the total
phenolic content. However, the total dietary fibre of rice bran had no significantly
different. The accelerated aging could be used to stabilization process for rice bran
before further utilization. These process could be produce low acidity and free fatty
acid content of rice bran oil production.
Keywords: rice bran, accelerated aging, dietary fibre, acidity, antioxidant
THE EFFECT OF ACCELERATED AGING ON THE
CHARACTERISTIC PROPERTIES OF RICE BRAN
LINGGA HERLAMBANG FEBRIANTO
Manuscript
submitted as a partial fulfillment of the requirement for
degree of Sarjana Teknologi Pertanian
at
Department of Food Science and Technology
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015
PREFACE
Praise to ALLAH SWT for the mercy, the graciousness, and the guidance
throughout the research and manuscript completion. The research entitled The
Effect of Accelerated Aging on the Characteristic Properties of Rice Bran that was
carried out in Kasetsart University from May to September 2014.
By completion of this research and manuscript, the author like to express
great appreciations and sincere thanks to:
1. My lovely parents, my sister Shafa Nadira, and my big family for their
endless loves, cares, prays, and support for me.
2. Dr. Tjahja Muhandri, S.TP., MT, as academic advisor for his time, care,
patient, concern, and guidance.
3. Dr. Pinthip Rumpagaporn as advisor for her time, care, patient,
knowledge, and valuable suggestion in guiding the author to complete the
research in Kasetsart University.
4. Ir. Sutrisno Koswara, M.Si. and Dr. Fahim Muhammad Taqi, DEA, as
examiners in my final presentation for their time, valuable suggestion, care,
and helps.
5. Dr. Sashitorn Tongchitpakdee and Mr. Phu Thai who take care three of us
Indonesian exchange students.
6. All my friends in Rice and Starch laboratory (room 2106), P’Tang,
P’Bunyut, P’Fai Wata, P’Oh, P’Nu, P’Joom, P’Pui, P’Vannack and
especially P’Mook, P’Fai, and P’Cin for the helping in my research work
and the wonderful time together.
7. Kasetsart exchange student 2014: Dyah Sekar A, Indah Kurniasari, and
AIMS students 2014: Gunawan S and Elvan for togetherness,
cooperations, and helps during the research in Thailand.
8. BIDIK MISI DIKTI and AIMS program for the scholarship.
9. All Indonesian fellows in Kasetsart University, mas Iwan, mba Dwita,
mba Ida, mba Hezti, mas Wildan, mas Aidil, and kak Alfa.
10. All my friends: Agisio Alya, Dicki Aulia R, M. Jaenal Septian, M. Arif
Munandar, Bahtiar Mustakim, and all of lovely friends #ITP 47.
Last but not least, hopefully this manuscript is useful for the readers and gives
a real contribution in food science development.
Bogor, January 2015
Lingga Herlambang Febrianto
TABLE OF CONTENT
LIST OF TABLE
vi
LIST OF FIGURE
vi
LIST OF APPENDICES
vi
INTRODUCTION
1
Background
1
Research Objective
2
LITERATURE REVIEW
2
Rice Aging
2
Accelerated Aging
3
Rice Bran
3
Rice Bran Oil
4
Antioxidant
4
METHODOLOGY
5
Material
5
Equipment
5
Procedure
5
Method of Analysis
7
RESULT AND DISCUSSION
Accelerated Aging of Rice Bran
9
9
Total, Soluble, and Insoluble Dietary Fibre of Rice Bran
11
Acidity of Rice Bran Oil
13
Free Fatty Acids Content
15
Total Phenolic Content
16
Reducing Power
18
CONCLUSION AND RECOMMENDATION
19
Conclusion
19
Recommendation
19
REFERENCES
19
APPENDICES
23
AUTHOR BIOGRAPHY
35
LIST OF TABLE
1 Schematic model of the aging process in rice (Zhou et al. 2002a)
2 Total, soluble, and insoluble dietary fiber of rice bran samples
3 Total phenolic content of rice bran sample
2
11
17
LIST OF FIGURE
1
2
3
4
Alcohol-soluble acidity of rice bran for several treatment
Water-soluble acidity of rice bran for several treatment
Free fatty acid content of rice bran sample
Antioxidant activity of rice bran by reducing power method
13
14
15
18
LIST OF APPENDICES
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Scheme of experimental design
Sample preparation of dry-mill paddy
Analytical scheme for soluble and insoluble dietary fibre
determination procedure
Freshly harvested, naturally aged, and accelerated aged rice bran
sample
The result of iodine test rice bran samples
The fluidized bed dryer machine and specification
The rice mill machine
Data of corrected protein using kjeldahl method for dietary fibre
analysis
Standard curve of BHT by total phenolic content assay.
Statistical analysis of total, soluble, and insoluble dietary fibre
rice bran
Statistical analysis of acidity rice bran oil.
Statistical analysis of free fatty acid content
Statistical analysis of total phenolic content rice bran extract
Statistical analysis of antioxidant activity by reducing power
method
23
24
25
26
26
27
27
28
28
29
31
32
33
34
INTRODUCTION
Background
Rice is a dominant staple food which has been consumed people in many
parts of the world, especially in Asia, where it supports approximately one-half of
the world population. The cooking quality of rice is one important factors
influencing the acceptability of consumers. Cooked rice that is generally preferred
and by people in some Asian countries, including Thailand, is that large volume and
is non-sticking. The desirable properties of cooked rice are generally obtained by
storing paddy for a certain period of time before further processing, the process that
is known as aging (Soponronnarit et al. 2008). Aging of rice is a normal step
between harvest and consumption. The freshly harvested paddy is less suitable both
for processing and consumption, whereas adequate aging brings about the desirable
properties (Rayaguru et al. 2011). The physicochemical properties of aged rice is
change during storage. The changes of aged rice are caused by changes in lipid,
protein, and other subtances produce from enzyme activities and oxygen (Charstil
1994). The changes perhaps altered to physicochemical properties of rice bran. The
naturally or conventional aging process is time-consuming, takes a long time,
approximately 4-6 months. This aging method also requires much space for storage
paddy and high operating cost. It is therefore necessary to explore other techniques
that can reduce the aging time and operating cost while, at the same time, can
maintain the rice properties such as appearance and texture to be similar to those
obtained by the naturally aging process. The accelerated aging of paddy could be
used as means to alter the rice characteristics. Accelerated aging process using
thermal processing has been reported as an alternative way to produce aged rice.
Rice bran is a by-product of rice production containing many bioactive
compounds, for instance, dietary fibres, antioxidant, essential fatty acids, and
phytosterols, which give beneficial effect to human health. It contains 34.1-52.3%
carbohydrate, 15-22% lipid, 10-16% protein, 7-11.4% fibre, and 6.6-9.9% ash
(Fabian and Ju 2011). Rice bran oil has been extracted and commercialized as high
quality of cooking oil, which is high in poly- and mono-unsaturated fatty acids. The
naturally aging method can undergo lipid oxidation by lipase activity, if we storing
rice in longer time. Heat treatment can deactivate lipase and this can slow down the
rate of lipid oxidation (Jaisut et al. 2009). Accelerated aging with heat treatment
maybe can protect the rice bran oil functional properties. Moreover, the accelerated
aging might be can produce low acidity of rice bran oil.
Effect of accelerated aging on functional properties of rice grain and flour has
already been discussed. However, the consequence of the accelerated aging
technique on the characteristic properties of the rice bran has to be investigated and
verified. Moreover, the investigation of accelerated aging on the rice bran, is quite
limited. This study thus elucidated the alteration of rice bran during aging.
Therefore, the objective of this work was to investigate the effect of accelerated
aging by fluidized bed drying on the rice bran. The quality was considered dietary
fibre contents, lipid rancidity, and antioxidant content of aged rice bran. All the
mentioned quality parameter of rice bran obtained from fluidized bed drying were
2
compared to those properties of the sample undergo naturally aging process and
freshly harvested of rice bran.
Research Objective
The objective of this research is to investigate the effect of accelerated aging
using high-temperature fluidized bed drying followed by tempering and ventilation
on the dietary fibre (insoluble and soluble dietary fibre), lipid rancidity, and
antioxidant activity properties of rice bran.
LITERATURE REVIEW
Rice Aging
Freshly harvested rice is less preferred by consumer because of poor cooking
properties like less kernel elongation and volume expansion with more solids loss
and softer gel consistency. Aging brings about progressive desirable changes in the
grain (Rayaguru et al. 2011). Aging is natural and spontaneous phenomenon that
commences after harvesting and continues as a temperature-, time-, and moisturedependent index (Likitwattanasade 2009). During the aging or storage, there are
physicochemical interaction among starch, lipid, protein, and enzymes reactions,
although the overall starch, lipid, and protein content in rice grain remain essentially
unchanged. It is apparent that aging is a complicated process involving physical,
chemical, and biological change. The model for aging process shows in Table 1.
Table 1 Schematic model of the aging process in rice (Zhou et al. 2002a)
Substrate
Starch
Lipid
Storage Change
Increasing of
strength of micelle
binding
1
2
Protein
Cooking Effect
Inhibit swelling of
starch granule
Sensory Effect
Texture
Fatty acid-amylose
Texture
Hydrolysis
Complex
Free fatty acid
oxidation
Aroma
Oxidation
Hydroperoxides,
carbonyl compounds
Oxidation
-SH
S-S
Increase of
volatile carbonyl
compounds
Decrease
sulphur volatile
compounds
Aroma
3
Aging is one the factors responsible for textural changes in cooked rice and
the properties, especially pasting properties of rice flour. The properties of cooked
rice become harder and less sticky than freshly harvested rice (Ohno and Ohisa
2005). The aged rice was found to exhibit an increased volume expansion and water
absorption during the cooking process. The minimum storage period for major
changes to occur in the hardness of cooked rice in conventional aging was 3 months
(Katekhong and Charoenrein 2012). The natural aging of rice takes approximately
4-6 months and also requires much more storage for paddy. This can increases
operating cost. Moreover, paddy is susceptible to insect damages, as well as
microorganisms and rodents during storage (Soponronnarit et al. 2008). It is
therefore necessary to explore other techniques that can reduce the aging time and
operating cost while, at the same time, can maintain the rice properties such as
appearance and texture to be similar to those obtained by the naturally aging process.
Accelerated Aging
The aging process may be accelerated by subjecting the grains to appropriate
environmental conditions to bring about the acceptable properties (Rayaguru et al.
2011). Accelerated aging used could be more practical commercially than the
naturally aging. The process for accelerated aging could be developed either by dry
or wet heat. Dry heat treatment is preferred since its performance is easier and
cheaper (Rayaguru et al. 2011). The importance of aging of rice with desired
cooking and organoleptic characteristic has attracted considerable attention.
Various studies indicated that heat treatment is the major factor responsible for
quality changes during aging. Few research workers further reported that the
interaction of moisture and temperature along with other factors affect the quality
of aged rice. Soponronnarit et al. (2008) investigated the characteristic of
accelerated and naturally aged rice using fluidized bed drying followed by
tempering and ventilation. The result showed that rice properties; namely
elongation ratio, whiteness, volume expansion, water uptake, solid loss, and pasting
properties changed in similar way to those of the naturally aged paddy. Nevertheless,
the head rice yield of rice undergone accelerated aging process was significant
lower than that of the naturally aged paddy (p0.05) from the freshly harvested and naturally
aged rice bran. So, the accelerated aging of rice bran using high-temperature
fluidized bed drying followed by tempering and ventilation had no significant effect
on TDF content. Moreover, TDF of accelerated aged rice bran had no changes
during high-temperature drying process. So, total dietary fibre still has beneficial
effect. However, Johansson (2012) was reported the dietary fibre of wheat and rye
bran decreased with increasing temperature and heat treatment affected the content
of TDF in the samples. The temperature used in this study was above 100 oC. This
fact could probably be due to the different temperature and drying time (thermal
heating), whereas could affect the amount of thermal heating to the grain sample.
The high-temperature fluidized bed drying process could not change the chain of
polysaccharides. Moreover, the TDF of accelerated aged rice bran was lowest than
other rice bran samples. The TDF of accelerated aged rice bran was decrease
compared with freshly harvested rice bran. The decrease of TDF with increased
12
temperature can be due to fragmentation of polysaccharides because of increased
thermal heating (Johansson 2012). These fragments of polysaccharides may not
precipitate during treatment with 95% ethanol in the dietary fibre analysis. It was
only polysaccharides that precipitate during treatment with 95% ethanol that were
detected while smaller fragments and monosaccharides were discarded (Johansson
2012). The TDF can be lost because different solubility properties of
polysaccharides in 95% ethanol in the dietary fibre analysis. This could also be the
reason for the decrease of TDF with accelerated aging treatment, even though the
decrease are not statistical significant.
The insoluble dietary fibre (IDF) of freshly harvested, naturally aged, and
accelerated aged rice bran were 26.54%, 25.39%, and 25.30% respectively. The
content of IDF from accelerated aged and naturally aged rice bran did not change
significantly compared to freshly harvested rice bran as reference. However, they
differ from the results observed by Johansson (2012) that the content of insoluble
dietary fibre decrease with increasing temperature for the wheat bran sample.
Moreover, Benitez at al. (2011) was reported that insoluble dietary fibre of onion
by-product, on applying sterilization process there was decrease. According to
Benitez et al. (2011) reductions in IDF content could be attributed to partial
degradation of cellulose and hemicelluloses into simple carbohydrates as a
consequence of heat treatment. The different result from the literature could
probably be due to the accelerated aging process could not structural modification
affecting to these polymers during the drying process. Because of the temperature
and drying time process or thermal heating to the grain were not enough for
degradation polymers. So, insoluble dietary fibre content of accelerated aged rice
bran still has beneficial effect to human consumption, because of the structure of
IDF did not change during fluidized bed drying process.
The content of soluble dietary fibre (SDF) of freshly harvested, naturally
aged, and accelerated aged rice bran were 2.88%, 3.40%, and 2.57% respectively.
The content of SDF from accelerated aged and naturally aged rice bran did not
change significantly compared to freshly harvested rice bran as reference. However,
Johansson (2012) was observed that the content of SDF of wheat bran increase with
heat treatment. IDF was relocated to soluble dietary fibre during severe extrusion
cooking, a process that heats foodstuff under pressure and high temperature. SDF
can increase due to mechanically rupture during extrusion of the glycosidic bods in
polysaccharides which release oligosaccharides leading to an increase of SDF
(Elleuch et al. 2011; Esposito et al. 2005). Moreover, heat treatment may cause
break down and degradation of these kinds polysaccharides. The breakdown of
glycosidic linkage in DF polysaccharides may result in a solubilisation of originally
insoluble fibre (Benitez et al. 2011). The different result could probably be the heat
treatment condition involved time and temperature. The temperature and drying
time process or thermal heating were not enough to breakdown and degradation of
DF polysaccharides. So, soluble dietary fibre of rice bran did not changes during
drying process and still has beneficial effect to human consumption. The content of
SDF naturally aged rice bran was higher compared to freshly harvested aged rice
bran, even though the increase are not statistical significant. This fact could
probably be due to the environmental storage condition for natural aging process of
paddy. The environmental storage condition could be affected the content of SDF
because the degradation of DF polysaccharides was occurred.
13
Acidity of Rice Bran Oil
The acidity of rice bran oil was determined according to Silva et al. (2006).
The value of acidity rice bran oil was measured by alcohol-soluble and watersoluble acidity according to AOAC Official Method. These method was chosen
because more practical and quick to know acidity of rice bran oil compared to other
method. The alcohol-soluble and water-soluble acidity were rapid method to
determined acidity of rice bran oil. The degree acidity of rice bran oil is an important
indicator of oil quality. The acidity is expressed as the amount of KOH (in mg)
necessary to neutralize free fatty acids contained in 1 g of oil. The value of acidity
is correlated with rancidity of rice bran oil, which is develop of any amount of free
fatty acid (FFA). The high value of acidity is correlated with high amount of FFA
on the rice bran oil. The problem of rancidity in rice bran oil caused by lipases. The
hydrolytic rancidity contributes to the acidity increase.
Alcohol Soluble Acidity
(mg KOH/g bran)
1.2
a
1
0.8
b
b
Freshly Harvested
0.6
Naturally Aged
0.4
Accelerated Aged
0.2
0
Rice Bran
a-b
Mean within the same letter are not significantly different (p>0.05)
Figure 1 Alcohol-soluble acidity of rice bran for several treatment
Figure 1 shows the results for alcohol-soluble acidity of rice bran samples.
The content of alcohol-soluble acidity freshly harvested, naturally aged, and
accelerated aged rice bran were 0.69 mg KOH/g bran, 0.94 mg KOH/g bran, and
0.79 mg KOH/g bran, respectively. The alcohol-soluble acidity content of
accelerated aged did not change significantly compared with freshly harvested rice
bran. The accelerated aging using high-temperature fluidized bed drying was
effective reducing the alcohol-soluble acidity compared with natural aged rice bran.
Silva et al. (2006) was reported thermal treatment capable to reduce oxidative
reaction of rancidity on rice bran contributed to higher lipolytic enzyme inhibition.
This fact could probably be the accelerated aging using high-temperature can
deactivate lipase activity on the rice grain and slow down the rate of lipid oxidation.
The lipase inactivation caused by denaturation of lipase protein. The hightemperature during accelerated aging can cause denaturation process of lipase. So,
14
lipase will loss of biological activity. Furthermore, the alcohol-soluble acidity of
naturally aged rice bran was highly significant than those of the other rice bran
samples. The high content of alcohol-soluble acidity was correlated with free fatty
acid on rice bran oil. The decomposition of lipids (triacylglycerols) into free fatty
acids was occurred by endogenous and microbial lipase during storage (Zhou et al.
2002b).
Water Soluble Acidity
(%)
12
10
a
b
c
8
Freshly Harvested
6
Naturally Aged
4
Accelerated Aged
2
0
Rice Bran
RiceSamples
Bran
a-c
Mean within the same letter are not significantly different (p>0.05)
Figure 2 Water-soluble acidity of rice bran for several treatment
Figure 2 shows the result of water-soluble acidity of rice bran samples. The
content of water-soluble acidity of freshly harvested, naturally aged, and
accelerated aged rice bran were 10.32%, 9.06%, and 8.12%, respectively.
Accelerated aged rice bran presented lowest significantly water-soluble acidity than
those of the other rice bran samples. The similar result was reported on the alcoholsoluble acidity content. The low value of water-soluble and alcohol-soluble acidity
was correlated with low acidity of rice bran oil (low FFA content). Silva et al.
(2006) showed the toasting process with heat treatment effective in reducing the
water-soluble acidity of polished rice bran. On the other hand, the contrast result
presented on the freshly harvested rice bran. The content of water-soluble acidity
of freshly harvested highly significant than those of the other rice bran samples.
This fact could probably be correlated with solubility of free fatty acid in the water
and alcohol solution, which was used to determination of water-soluble and alcoholsoluble acidity. Probably, the length of hydrocarbon chain from free fatty acid
affected the solubility in the water. The solubility of FFA in the water was affected
by the number of carbon atoms building blocks of the fatty acids. The short chain
fatty acids are more soluble than long chain fatty acids. Moreover, the short chain
of free fatty acid and organic acids would be more soluble in the water. Freshly
harvested rice bran could probably be has higher organic acids than the other sample.
In addition, increase in water-soluble acidity probably due to formation of organic
acids other than fatty acids. Furthermore, the decrease in water soluble acidity in
the accelerated aged caused by high-temperature treatment, which was
decarboxylated or volatilized of organic acid by high-temperature.
15
Free Fatty Acids Content
Free fatty acids (FFA) content of rice bran oil was determined according to
Jaisut et al. (2009). These method to make sure the results of alcohol-soluble and
water-soluble acidity methods and to determined rice bran oil quality. The rice bran
oil was extracted with petroleum ether, which was all FFA on the rice bran oil could
be analyzed. When bran layers are removed from the endosperm during the milling
process, the lipids in rice bran come into contact with highly reactive lipases. The
lipases, which are endogenously enzyme, cause hydrolysis of neutral bran oil to
FFA and leading to development rancidity (Kim et al. 2014). In addition, FFA is
highly susceptible to oxidation which usually occurs by the action by the action of
lipoxygenase. Furthermore, the FFA undergoes further oxidation decomposition
with the generation rancid off-flavors of rice bran (Kim et al. 2014). The bran oil
with an excess 10% FFA is unsuitable for human consumption or the economical
extraction of edible oil especially high refining loss (Ramezanzadeh et al. 1999).
Inactivation of lipases activity could be prevent hydrolytic rancidity in the rice bran
10
a
Free Fatty Acid (%)
9
8
7
6
5
4
b
3
b
Freshly
Harvested
Naturally Aged
Accelerated
Aged
2
1
0
Rice Bran
RiceSamples
Bran
a-b
Mean within the same letter are not significantly different (p>0.05)
Figure 3 Free fatty acid content of rice bran sample
Free fatty acids content of accelerated aged rice bran was not significantly
different compared with freshly harvested rice bran (Figure 3). These result was
similar with alcohol-soluble acidity result on the acidity determination. The acidity
value (alcohol-soluble and water soluble acidity) of rice bran oil was correlated with
FFA content, which was high acidity value described high FFA content. The FFA
levels of
CHARACTERISTIC PROPERTIES OF RICE BRAN
LINGGA HERLAMBANG FEBRIANTO
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015
STATEMENT LETTER OF MANUSCRIPT AND SOURCE OF
INFORMATION*
I declare the truth that this manuscript entitled The Effect of Accelerated
Aging on the Characteristic Properties of Rice Bran is my work with guidance
of the advisors and has not been submitted in any form at any college, except Bogor
Agricultural University and Kasetsart University. Sources of information derived
or quoted from published or unpublished works of other authors mentioned in the
text and listed in the List of References at the end of this manuscript.
Hereby this statement, I bestow the copyright of my manuscript to the Bogor
Agricultural University.
Bogor, January 2015
Lingga Herlambang Febrianto
NIM F24100011
ABSTRACT
LINGGA HERLAMBANG FEBRIANTO. The Effect of Accelerated Aging on the
Characteristic Properties of Rice Bran. Supervised by TJAHJA MUHANDRI and
PINTHIP RUMPAGAPORN.
Accelerated aging process using thermal processing has been reported as an
alternative way to produce aged rice. Rice bran is a by-product of rice production
containing many bioactive compounds, which give beneficial effect to human
health. Effect of accelerated aging on functional properties of rice grain and flour
has already been discussed. However, the consequence of the accelerated aging
technique on the characteristic properties of the rice bran has to be investigated and
verified. Moreover, the investigation of accelerated aging on the rice bran is quite
limited. The objective of this research is to investigate the effect of accelerated
aging using high-temperature fluidized bed drying followed by tempering and
ventilation on the dietary fibre (insoluble and soluble dietary fibre), lipid rancidity,
and antioxidant activity properties of rice bran. Based on the experimental results it
was found that the rice bran properties after accelerated aging process namely,
alcohol-soluble and water-soluble acidity, free fatty acids content, total phenolic
content, and antioxidant activity significantly affected the aged rice bran properties.
The accelerated aging process using high-temperature could decrease acidity and
free fatty acids contents of rice bran oil. Moreover, the accelerated aging was found
to exhibit decreased of total phenolic content and reducing power of rice bran
extracts. The reducing power of rice bran extracts were associated with the total
phenolic content. However, the total dietary fibre of rice bran had no significantly
different. The accelerated aging could be used to stabilization process for rice bran
before further utilization. These process could be produce low acidity and free fatty
acid content of rice bran oil production.
Keywords: rice bran, accelerated aging, dietary fibre, acidity, antioxidant
THE EFFECT OF ACCELERATED AGING ON THE
CHARACTERISTIC PROPERTIES OF RICE BRAN
LINGGA HERLAMBANG FEBRIANTO
Manuscript
submitted as a partial fulfillment of the requirement for
degree of Sarjana Teknologi Pertanian
at
Department of Food Science and Technology
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
FACULTY OF AGRICULTURAL ENGINEERING AND TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015
PREFACE
Praise to ALLAH SWT for the mercy, the graciousness, and the guidance
throughout the research and manuscript completion. The research entitled The
Effect of Accelerated Aging on the Characteristic Properties of Rice Bran that was
carried out in Kasetsart University from May to September 2014.
By completion of this research and manuscript, the author like to express
great appreciations and sincere thanks to:
1. My lovely parents, my sister Shafa Nadira, and my big family for their
endless loves, cares, prays, and support for me.
2. Dr. Tjahja Muhandri, S.TP., MT, as academic advisor for his time, care,
patient, concern, and guidance.
3. Dr. Pinthip Rumpagaporn as advisor for her time, care, patient,
knowledge, and valuable suggestion in guiding the author to complete the
research in Kasetsart University.
4. Ir. Sutrisno Koswara, M.Si. and Dr. Fahim Muhammad Taqi, DEA, as
examiners in my final presentation for their time, valuable suggestion, care,
and helps.
5. Dr. Sashitorn Tongchitpakdee and Mr. Phu Thai who take care three of us
Indonesian exchange students.
6. All my friends in Rice and Starch laboratory (room 2106), P’Tang,
P’Bunyut, P’Fai Wata, P’Oh, P’Nu, P’Joom, P’Pui, P’Vannack and
especially P’Mook, P’Fai, and P’Cin for the helping in my research work
and the wonderful time together.
7. Kasetsart exchange student 2014: Dyah Sekar A, Indah Kurniasari, and
AIMS students 2014: Gunawan S and Elvan for togetherness,
cooperations, and helps during the research in Thailand.
8. BIDIK MISI DIKTI and AIMS program for the scholarship.
9. All Indonesian fellows in Kasetsart University, mas Iwan, mba Dwita,
mba Ida, mba Hezti, mas Wildan, mas Aidil, and kak Alfa.
10. All my friends: Agisio Alya, Dicki Aulia R, M. Jaenal Septian, M. Arif
Munandar, Bahtiar Mustakim, and all of lovely friends #ITP 47.
Last but not least, hopefully this manuscript is useful for the readers and gives
a real contribution in food science development.
Bogor, January 2015
Lingga Herlambang Febrianto
TABLE OF CONTENT
LIST OF TABLE
vi
LIST OF FIGURE
vi
LIST OF APPENDICES
vi
INTRODUCTION
1
Background
1
Research Objective
2
LITERATURE REVIEW
2
Rice Aging
2
Accelerated Aging
3
Rice Bran
3
Rice Bran Oil
4
Antioxidant
4
METHODOLOGY
5
Material
5
Equipment
5
Procedure
5
Method of Analysis
7
RESULT AND DISCUSSION
Accelerated Aging of Rice Bran
9
9
Total, Soluble, and Insoluble Dietary Fibre of Rice Bran
11
Acidity of Rice Bran Oil
13
Free Fatty Acids Content
15
Total Phenolic Content
16
Reducing Power
18
CONCLUSION AND RECOMMENDATION
19
Conclusion
19
Recommendation
19
REFERENCES
19
APPENDICES
23
AUTHOR BIOGRAPHY
35
LIST OF TABLE
1 Schematic model of the aging process in rice (Zhou et al. 2002a)
2 Total, soluble, and insoluble dietary fiber of rice bran samples
3 Total phenolic content of rice bran sample
2
11
17
LIST OF FIGURE
1
2
3
4
Alcohol-soluble acidity of rice bran for several treatment
Water-soluble acidity of rice bran for several treatment
Free fatty acid content of rice bran sample
Antioxidant activity of rice bran by reducing power method
13
14
15
18
LIST OF APPENDICES
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Scheme of experimental design
Sample preparation of dry-mill paddy
Analytical scheme for soluble and insoluble dietary fibre
determination procedure
Freshly harvested, naturally aged, and accelerated aged rice bran
sample
The result of iodine test rice bran samples
The fluidized bed dryer machine and specification
The rice mill machine
Data of corrected protein using kjeldahl method for dietary fibre
analysis
Standard curve of BHT by total phenolic content assay.
Statistical analysis of total, soluble, and insoluble dietary fibre
rice bran
Statistical analysis of acidity rice bran oil.
Statistical analysis of free fatty acid content
Statistical analysis of total phenolic content rice bran extract
Statistical analysis of antioxidant activity by reducing power
method
23
24
25
26
26
27
27
28
28
29
31
32
33
34
INTRODUCTION
Background
Rice is a dominant staple food which has been consumed people in many
parts of the world, especially in Asia, where it supports approximately one-half of
the world population. The cooking quality of rice is one important factors
influencing the acceptability of consumers. Cooked rice that is generally preferred
and by people in some Asian countries, including Thailand, is that large volume and
is non-sticking. The desirable properties of cooked rice are generally obtained by
storing paddy for a certain period of time before further processing, the process that
is known as aging (Soponronnarit et al. 2008). Aging of rice is a normal step
between harvest and consumption. The freshly harvested paddy is less suitable both
for processing and consumption, whereas adequate aging brings about the desirable
properties (Rayaguru et al. 2011). The physicochemical properties of aged rice is
change during storage. The changes of aged rice are caused by changes in lipid,
protein, and other subtances produce from enzyme activities and oxygen (Charstil
1994). The changes perhaps altered to physicochemical properties of rice bran. The
naturally or conventional aging process is time-consuming, takes a long time,
approximately 4-6 months. This aging method also requires much space for storage
paddy and high operating cost. It is therefore necessary to explore other techniques
that can reduce the aging time and operating cost while, at the same time, can
maintain the rice properties such as appearance and texture to be similar to those
obtained by the naturally aging process. The accelerated aging of paddy could be
used as means to alter the rice characteristics. Accelerated aging process using
thermal processing has been reported as an alternative way to produce aged rice.
Rice bran is a by-product of rice production containing many bioactive
compounds, for instance, dietary fibres, antioxidant, essential fatty acids, and
phytosterols, which give beneficial effect to human health. It contains 34.1-52.3%
carbohydrate, 15-22% lipid, 10-16% protein, 7-11.4% fibre, and 6.6-9.9% ash
(Fabian and Ju 2011). Rice bran oil has been extracted and commercialized as high
quality of cooking oil, which is high in poly- and mono-unsaturated fatty acids. The
naturally aging method can undergo lipid oxidation by lipase activity, if we storing
rice in longer time. Heat treatment can deactivate lipase and this can slow down the
rate of lipid oxidation (Jaisut et al. 2009). Accelerated aging with heat treatment
maybe can protect the rice bran oil functional properties. Moreover, the accelerated
aging might be can produce low acidity of rice bran oil.
Effect of accelerated aging on functional properties of rice grain and flour has
already been discussed. However, the consequence of the accelerated aging
technique on the characteristic properties of the rice bran has to be investigated and
verified. Moreover, the investigation of accelerated aging on the rice bran, is quite
limited. This study thus elucidated the alteration of rice bran during aging.
Therefore, the objective of this work was to investigate the effect of accelerated
aging by fluidized bed drying on the rice bran. The quality was considered dietary
fibre contents, lipid rancidity, and antioxidant content of aged rice bran. All the
mentioned quality parameter of rice bran obtained from fluidized bed drying were
2
compared to those properties of the sample undergo naturally aging process and
freshly harvested of rice bran.
Research Objective
The objective of this research is to investigate the effect of accelerated aging
using high-temperature fluidized bed drying followed by tempering and ventilation
on the dietary fibre (insoluble and soluble dietary fibre), lipid rancidity, and
antioxidant activity properties of rice bran.
LITERATURE REVIEW
Rice Aging
Freshly harvested rice is less preferred by consumer because of poor cooking
properties like less kernel elongation and volume expansion with more solids loss
and softer gel consistency. Aging brings about progressive desirable changes in the
grain (Rayaguru et al. 2011). Aging is natural and spontaneous phenomenon that
commences after harvesting and continues as a temperature-, time-, and moisturedependent index (Likitwattanasade 2009). During the aging or storage, there are
physicochemical interaction among starch, lipid, protein, and enzymes reactions,
although the overall starch, lipid, and protein content in rice grain remain essentially
unchanged. It is apparent that aging is a complicated process involving physical,
chemical, and biological change. The model for aging process shows in Table 1.
Table 1 Schematic model of the aging process in rice (Zhou et al. 2002a)
Substrate
Starch
Lipid
Storage Change
Increasing of
strength of micelle
binding
1
2
Protein
Cooking Effect
Inhibit swelling of
starch granule
Sensory Effect
Texture
Fatty acid-amylose
Texture
Hydrolysis
Complex
Free fatty acid
oxidation
Aroma
Oxidation
Hydroperoxides,
carbonyl compounds
Oxidation
-SH
S-S
Increase of
volatile carbonyl
compounds
Decrease
sulphur volatile
compounds
Aroma
3
Aging is one the factors responsible for textural changes in cooked rice and
the properties, especially pasting properties of rice flour. The properties of cooked
rice become harder and less sticky than freshly harvested rice (Ohno and Ohisa
2005). The aged rice was found to exhibit an increased volume expansion and water
absorption during the cooking process. The minimum storage period for major
changes to occur in the hardness of cooked rice in conventional aging was 3 months
(Katekhong and Charoenrein 2012). The natural aging of rice takes approximately
4-6 months and also requires much more storage for paddy. This can increases
operating cost. Moreover, paddy is susceptible to insect damages, as well as
microorganisms and rodents during storage (Soponronnarit et al. 2008). It is
therefore necessary to explore other techniques that can reduce the aging time and
operating cost while, at the same time, can maintain the rice properties such as
appearance and texture to be similar to those obtained by the naturally aging process.
Accelerated Aging
The aging process may be accelerated by subjecting the grains to appropriate
environmental conditions to bring about the acceptable properties (Rayaguru et al.
2011). Accelerated aging used could be more practical commercially than the
naturally aging. The process for accelerated aging could be developed either by dry
or wet heat. Dry heat treatment is preferred since its performance is easier and
cheaper (Rayaguru et al. 2011). The importance of aging of rice with desired
cooking and organoleptic characteristic has attracted considerable attention.
Various studies indicated that heat treatment is the major factor responsible for
quality changes during aging. Few research workers further reported that the
interaction of moisture and temperature along with other factors affect the quality
of aged rice. Soponronnarit et al. (2008) investigated the characteristic of
accelerated and naturally aged rice using fluidized bed drying followed by
tempering and ventilation. The result showed that rice properties; namely
elongation ratio, whiteness, volume expansion, water uptake, solid loss, and pasting
properties changed in similar way to those of the naturally aged paddy. Nevertheless,
the head rice yield of rice undergone accelerated aging process was significant
lower than that of the naturally aged paddy (p0.05) from the freshly harvested and naturally
aged rice bran. So, the accelerated aging of rice bran using high-temperature
fluidized bed drying followed by tempering and ventilation had no significant effect
on TDF content. Moreover, TDF of accelerated aged rice bran had no changes
during high-temperature drying process. So, total dietary fibre still has beneficial
effect. However, Johansson (2012) was reported the dietary fibre of wheat and rye
bran decreased with increasing temperature and heat treatment affected the content
of TDF in the samples. The temperature used in this study was above 100 oC. This
fact could probably be due to the different temperature and drying time (thermal
heating), whereas could affect the amount of thermal heating to the grain sample.
The high-temperature fluidized bed drying process could not change the chain of
polysaccharides. Moreover, the TDF of accelerated aged rice bran was lowest than
other rice bran samples. The TDF of accelerated aged rice bran was decrease
compared with freshly harvested rice bran. The decrease of TDF with increased
12
temperature can be due to fragmentation of polysaccharides because of increased
thermal heating (Johansson 2012). These fragments of polysaccharides may not
precipitate during treatment with 95% ethanol in the dietary fibre analysis. It was
only polysaccharides that precipitate during treatment with 95% ethanol that were
detected while smaller fragments and monosaccharides were discarded (Johansson
2012). The TDF can be lost because different solubility properties of
polysaccharides in 95% ethanol in the dietary fibre analysis. This could also be the
reason for the decrease of TDF with accelerated aging treatment, even though the
decrease are not statistical significant.
The insoluble dietary fibre (IDF) of freshly harvested, naturally aged, and
accelerated aged rice bran were 26.54%, 25.39%, and 25.30% respectively. The
content of IDF from accelerated aged and naturally aged rice bran did not change
significantly compared to freshly harvested rice bran as reference. However, they
differ from the results observed by Johansson (2012) that the content of insoluble
dietary fibre decrease with increasing temperature for the wheat bran sample.
Moreover, Benitez at al. (2011) was reported that insoluble dietary fibre of onion
by-product, on applying sterilization process there was decrease. According to
Benitez et al. (2011) reductions in IDF content could be attributed to partial
degradation of cellulose and hemicelluloses into simple carbohydrates as a
consequence of heat treatment. The different result from the literature could
probably be due to the accelerated aging process could not structural modification
affecting to these polymers during the drying process. Because of the temperature
and drying time process or thermal heating to the grain were not enough for
degradation polymers. So, insoluble dietary fibre content of accelerated aged rice
bran still has beneficial effect to human consumption, because of the structure of
IDF did not change during fluidized bed drying process.
The content of soluble dietary fibre (SDF) of freshly harvested, naturally
aged, and accelerated aged rice bran were 2.88%, 3.40%, and 2.57% respectively.
The content of SDF from accelerated aged and naturally aged rice bran did not
change significantly compared to freshly harvested rice bran as reference. However,
Johansson (2012) was observed that the content of SDF of wheat bran increase with
heat treatment. IDF was relocated to soluble dietary fibre during severe extrusion
cooking, a process that heats foodstuff under pressure and high temperature. SDF
can increase due to mechanically rupture during extrusion of the glycosidic bods in
polysaccharides which release oligosaccharides leading to an increase of SDF
(Elleuch et al. 2011; Esposito et al. 2005). Moreover, heat treatment may cause
break down and degradation of these kinds polysaccharides. The breakdown of
glycosidic linkage in DF polysaccharides may result in a solubilisation of originally
insoluble fibre (Benitez et al. 2011). The different result could probably be the heat
treatment condition involved time and temperature. The temperature and drying
time process or thermal heating were not enough to breakdown and degradation of
DF polysaccharides. So, soluble dietary fibre of rice bran did not changes during
drying process and still has beneficial effect to human consumption. The content of
SDF naturally aged rice bran was higher compared to freshly harvested aged rice
bran, even though the increase are not statistical significant. This fact could
probably be due to the environmental storage condition for natural aging process of
paddy. The environmental storage condition could be affected the content of SDF
because the degradation of DF polysaccharides was occurred.
13
Acidity of Rice Bran Oil
The acidity of rice bran oil was determined according to Silva et al. (2006).
The value of acidity rice bran oil was measured by alcohol-soluble and watersoluble acidity according to AOAC Official Method. These method was chosen
because more practical and quick to know acidity of rice bran oil compared to other
method. The alcohol-soluble and water-soluble acidity were rapid method to
determined acidity of rice bran oil. The degree acidity of rice bran oil is an important
indicator of oil quality. The acidity is expressed as the amount of KOH (in mg)
necessary to neutralize free fatty acids contained in 1 g of oil. The value of acidity
is correlated with rancidity of rice bran oil, which is develop of any amount of free
fatty acid (FFA). The high value of acidity is correlated with high amount of FFA
on the rice bran oil. The problem of rancidity in rice bran oil caused by lipases. The
hydrolytic rancidity contributes to the acidity increase.
Alcohol Soluble Acidity
(mg KOH/g bran)
1.2
a
1
0.8
b
b
Freshly Harvested
0.6
Naturally Aged
0.4
Accelerated Aged
0.2
0
Rice Bran
a-b
Mean within the same letter are not significantly different (p>0.05)
Figure 1 Alcohol-soluble acidity of rice bran for several treatment
Figure 1 shows the results for alcohol-soluble acidity of rice bran samples.
The content of alcohol-soluble acidity freshly harvested, naturally aged, and
accelerated aged rice bran were 0.69 mg KOH/g bran, 0.94 mg KOH/g bran, and
0.79 mg KOH/g bran, respectively. The alcohol-soluble acidity content of
accelerated aged did not change significantly compared with freshly harvested rice
bran. The accelerated aging using high-temperature fluidized bed drying was
effective reducing the alcohol-soluble acidity compared with natural aged rice bran.
Silva et al. (2006) was reported thermal treatment capable to reduce oxidative
reaction of rancidity on rice bran contributed to higher lipolytic enzyme inhibition.
This fact could probably be the accelerated aging using high-temperature can
deactivate lipase activity on the rice grain and slow down the rate of lipid oxidation.
The lipase inactivation caused by denaturation of lipase protein. The hightemperature during accelerated aging can cause denaturation process of lipase. So,
14
lipase will loss of biological activity. Furthermore, the alcohol-soluble acidity of
naturally aged rice bran was highly significant than those of the other rice bran
samples. The high content of alcohol-soluble acidity was correlated with free fatty
acid on rice bran oil. The decomposition of lipids (triacylglycerols) into free fatty
acids was occurred by endogenous and microbial lipase during storage (Zhou et al.
2002b).
Water Soluble Acidity
(%)
12
10
a
b
c
8
Freshly Harvested
6
Naturally Aged
4
Accelerated Aged
2
0
Rice Bran
RiceSamples
Bran
a-c
Mean within the same letter are not significantly different (p>0.05)
Figure 2 Water-soluble acidity of rice bran for several treatment
Figure 2 shows the result of water-soluble acidity of rice bran samples. The
content of water-soluble acidity of freshly harvested, naturally aged, and
accelerated aged rice bran were 10.32%, 9.06%, and 8.12%, respectively.
Accelerated aged rice bran presented lowest significantly water-soluble acidity than
those of the other rice bran samples. The similar result was reported on the alcoholsoluble acidity content. The low value of water-soluble and alcohol-soluble acidity
was correlated with low acidity of rice bran oil (low FFA content). Silva et al.
(2006) showed the toasting process with heat treatment effective in reducing the
water-soluble acidity of polished rice bran. On the other hand, the contrast result
presented on the freshly harvested rice bran. The content of water-soluble acidity
of freshly harvested highly significant than those of the other rice bran samples.
This fact could probably be correlated with solubility of free fatty acid in the water
and alcohol solution, which was used to determination of water-soluble and alcoholsoluble acidity. Probably, the length of hydrocarbon chain from free fatty acid
affected the solubility in the water. The solubility of FFA in the water was affected
by the number of carbon atoms building blocks of the fatty acids. The short chain
fatty acids are more soluble than long chain fatty acids. Moreover, the short chain
of free fatty acid and organic acids would be more soluble in the water. Freshly
harvested rice bran could probably be has higher organic acids than the other sample.
In addition, increase in water-soluble acidity probably due to formation of organic
acids other than fatty acids. Furthermore, the decrease in water soluble acidity in
the accelerated aged caused by high-temperature treatment, which was
decarboxylated or volatilized of organic acid by high-temperature.
15
Free Fatty Acids Content
Free fatty acids (FFA) content of rice bran oil was determined according to
Jaisut et al. (2009). These method to make sure the results of alcohol-soluble and
water-soluble acidity methods and to determined rice bran oil quality. The rice bran
oil was extracted with petroleum ether, which was all FFA on the rice bran oil could
be analyzed. When bran layers are removed from the endosperm during the milling
process, the lipids in rice bran come into contact with highly reactive lipases. The
lipases, which are endogenously enzyme, cause hydrolysis of neutral bran oil to
FFA and leading to development rancidity (Kim et al. 2014). In addition, FFA is
highly susceptible to oxidation which usually occurs by the action by the action of
lipoxygenase. Furthermore, the FFA undergoes further oxidation decomposition
with the generation rancid off-flavors of rice bran (Kim et al. 2014). The bran oil
with an excess 10% FFA is unsuitable for human consumption or the economical
extraction of edible oil especially high refining loss (Ramezanzadeh et al. 1999).
Inactivation of lipases activity could be prevent hydrolytic rancidity in the rice bran
10
a
Free Fatty Acid (%)
9
8
7
6
5
4
b
3
b
Freshly
Harvested
Naturally Aged
Accelerated
Aged
2
1
0
Rice Bran
RiceSamples
Bran
a-b
Mean within the same letter are not significantly different (p>0.05)
Figure 3 Free fatty acid content of rice bran sample
Free fatty acids content of accelerated aged rice bran was not significantly
different compared with freshly harvested rice bran (Figure 3). These result was
similar with alcohol-soluble acidity result on the acidity determination. The acidity
value (alcohol-soluble and water soluble acidity) of rice bran oil was correlated with
FFA content, which was high acidity value described high FFA content. The FFA
levels of