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Effect of Stabilized Rice Bran Fractions on the Formation of Rice Flour Pasting Properties

Mohammed I. Saleh1, 2, Ziad Y. Abu-Waar3, Muhanad W. Akash4 and Maher Al-Dabbas1

Accepted for Publication Cereal Chemistry

8 July 2014

1Department Nutrition and Food Technology, Faculty of Agriculture, The University of Jordan, Amman-Jordan, 2Correspondent author, misaleh@ju.edu.jo, +962-6-5355000 Ext. 22426 3Department of Physics, Faculty of Science, The University of Jordan, Amman-Jordan. 4Department of Horticulture and Crop Science, Faculty of Agriculture, The University of Jordan, Amman-Jordan.

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Abstract:

Rice flour composition played a key role in determining the changes in pasting properties

of rice flour. The influence of incorporating defatted rice bran (DFRB), rice bran fiber (RBF),

rice bran proteins (RBP) and stabilized rice bran (SRB) fractions on the mechanism of rice flour

pasting viscosities was investigated.

Pasting properties of long and medium grain rice flour substituted with 5, 10, 15, 20 and

100% bran fractions resulted in a significant decrease (P<0.05) in rice flour pasting properties.

Flour substituted with rice bran proteins had the lowest pasting properties compared with

other fractions with the more percentage substituted, the lower the pasting properties. DFRB and

RBF were least affected by replacement. Results were attributed to the contribution of rice

starch in the mechanism of rice paste formation where decreasing starch in a rice flour sample, as

a result of substituting with fractions of stabilized rice bran, may have resulted in faster swelling

of starch granules to its maximum extent and increase their susceptibility to be disrupted by

shear resulting in low paste viscosities. Results also suggested that protein structural integrity

and the nature of starch–protein bonding affected rice flour pasting mechanism formation.

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Introduction:

Rice flour has gained great focus as the most suitable cereal to making gluten-free

products due to its soft taste, colorless, hypoallergenic properties, and easy digestibility (Gujral

et al., 2003). However, unlike wheat proteins (i.e., mainly gluten) that are responsible for the

elastic characteristics of dough and contributes to the texture of many baked products; rice flour

proteins lack the ability to develop viscoelastic network-like gluten. The use of gluten-free

flours, therefore, leads low quality products characterized with its poor texture, flavor, and

mouthfeel (Arendt et al., 2002). Strengthener agents including other types of starches, gums and

protein isolates and their modified products are usually added to the gluten-free flours to

overcome such negative aspects (Kang et al., 1997). Inclusions of protein isolate also increase

the nutritional quality of gluten-free products.

Rice bran is considered a rice milling by-product that includes significant amounts of

essential amino acids (Tang, et al., 2003), dietetic fibers, ash, vitamins, minerals and several

functional compounds such as oryzanol, tocopherols, and polyphenols (Cicero1 and Derosa,

2005). However, due to the quick formation of free fatty acids and development rancidity, rice

bran has to be stabilized to improve its stability before it can be used in food products. The use

of stabilized rice bran components expects to improve rice flour functionality. Furthermore,

there is a lack of research in studying the effect of added components on functional properties of

mixed rice flour systems including rice bran fractions. Developing high protein and fiber rice-

based products for gluten-free applications has a great potential to add value to rice flour and can

significantly increase rice utilization. Moreover, a thorough understanding of the physical and

chemical properties of rice flours and their interactions with other ingredients is needed in order

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to provide a research foundation for future rice research as well as for future value-added rice

products.

Pasting viscosities of flours are usually measured as an indication of food disintegration

as well as its ability to withstand heating and shearing stress during processing. Viscosity

parameters, therefore, are used as a principal measure of cooking and processing characteristics

of cereal grains (Meadows and Barton 2002).

Rice component’s variability can be an ideal model to explain structural changes

occurring to rice that influence its functional properties (Hamaker and Griffin 1990; Fitzgerald et

al., 2003 and Zhou et al., 2003). Since changes in rice functionality is usually associated with

that occurring to rice components, as well as their interactions; rice flour viscosity is considered

a key factor that determine rice flour functionality. For example, the contribution of rice

chemical composition in forming rice flour pasting properties provide an ideal understanding of

changes that can be reflected in changes occurring in rice textural characteristics (Saleh, 2006).

Furthermore, changes in the molecular weight of rice proteins can be correlated with cooked rice

stickiness (Hamaker and Griffin 1990 and Hamaker et al., 1991) where associations of miniature

amount of protein (i.e., low molecular weights) with the starch granule believed to confer rigidity

to the starch granules; thus play a role in also changing rice viscoelastic properties (Derycke et

al., 2005). The formation of protein-starch matrixes are also believed to inhibit starch maximum

swelling; increasing proteins competition for water and limiting starch leaching out during

processing (Becker et al., 2001 and Yang and Chang 1999). Martin and Fitzgerald (2002)

reported that proteins affected the pasting properties of rice flour through binding with water and

promoting the formation of a network of proteins linked by disulphide bonds. In the same

manner, Fitzgerald et al., (2003) indicated that the formation of “denatured protein’s gel matrix”

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as a result of heating rice flour can provide mechanical support, stabilize the continuous matrix

and strengthen the integrity of starch granules. Edwards et al., (2002) also suggested that the

nature of starch protein bonding of dough is the most important factor in determining the linear

viscoelastic behavior of starch molecules.

Although the influence of rice components including proteins and lipids on rice

functional properties are documented; the mechanism by which each component influences rice

functionality is still largely unknown. The effects “nutritional-value added rice milling by-

products” to rice flour on its physical properties have yet to be reported. Therefore, the

objectives of this study are to investigate the effect of stabilized rice bran fractions as

supplements for proteins, fiber and lipids on the formation of rice flour pasting properties.

Materials and Methods:

Samples and treatment preparation:

Two milled rice cultivars, Wells (long grain) and Calrose (medium grain), obtained from

the 2011 crop (Gulf Pacific Rice Co., Inc., Houston, TX, 77041, USA) were used in this study.

Only head rice kernels of thickness range from 1.69 to 1.72 mm were used to provide uniform

composition across samples. A cyclone sample mill (UDY Corporation, 201 Rome Court, Fort

Collins, CO 80524, USA) fitted with a 100-mesh sieve was used for grinding the rice samples to

produce rice flour.

Heat stabilized rice bran (SRB) was obtained from Gulf Pacific Co., Inc., Houston, TX,

77041, USA. The defatting procedures employed are according to Wang et al., (1999). Briefly,

rice bran was defatted twice using hexane in bran to solvent ratio of 1:3 at a setting of 250 rpm in

a lab stirrer for 30 min and centrifuge at 3000 g for 10 min at room temperature (23.5oC±1). The

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defatted rice bran (DFRB) was then air dried for 24 h, grinded using the cyclone sample mill

used previously fitted with a 100-mesh sieve to produce defatted rice bran. Defatted rice bran

was then kept in Ziploc bags and stored at 7oC until use.

Rice bran protein (RBP) was extracted using iso-electric precipitation according to the

method described by Gnanasambandam and Hettiarachchy (1995). In brief, defatted rice bran

sample and distilled de-ionized water (1:10) was adjusted to pH 11.0 (using 0.2% sodium

hydroxide) and stirred 30 min at 23.5oC±1. Slurries were then centrifuged (Eppendorf, 5804,

AG, Barkhausenweg 1, 22339 Hamburg, Germany) at 3000 g for 30 min. Supernatants to

second extraction were then adjusted to pH 4.5 and centrifuged again at 3000 g for 30 min.

Precipitate (i.e., rice bran protein) was then washed and centrifuged using water (pH 7.0),

suspended in distilled de-ionized water (pH 7.0 with 1 M hydrochloric acid (HCL)) and then

freeze dried (Flexi-Dry, MP Manifold Freeze-Dryers, FD-3-55D-MP, 3538 Main Street Stone

Ridge, NY, 12484), grinded using a cyclone sample mill fitted with a 100-mesh sieve and kept in

Ziploc bags and stored at 7oC at until use. The residual product after the rice bran protein

extractions (i.e., to be called rice bran fiber in this study) (RBF) was collected, grinded as

described previously, sieved through a 100-mesh sieve and stored at 7oC until use.

Treatments of rice flour and various rice bran fractions were prepared by substituting rice

flour with DFRB, RBP, RBF or SRB forming 0, 5, 10, 20 or 100% of the sample. Treatments

were mixed thoroughly using a household kitchenAid mixer (Model KSM150PSER) before

measurements were performed.

Proximate analysis:

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Moisture content (AACC, 2000 methods 44-15.02), total lipid content (AACC, 2000

methods 30-25.01) protein content (AACC, 2000 method 46-13.01), dietary fiber (AACC, 2000

method 32-10.01) and ash content (AACC, 2000 method 08-01.01) were used to determine the

chemical composition of DFRB, RBP, RBF and SRB.

Pasting properties measurements:

A Rapid Visco-Analyzer (RVA 4500, Perten Instruments, Springfield, IL, USA)

according to RVA Rice Method (AACC, 2000 method 61-02.01), was used for measuring the

pasting properties of rice flour and treatments of rice flour samples. Approximately 3 g of rice

flour was mixed with 25 ml of distilled water; the slurry was mixed at 50°C for one min at 160

rpm before being heated from 50°C to 95°C at a heating rate of 12oC/min. The hot paste was

held at 95°C for 2.5 min and then cooled down to 50°C at a cooling rate of 12oC/min and typical

RVA parameters were extracted. Three replicated were collected and parameters recorded were

peak viscosity, trough viscosity, final viscosity, breakdown, setback, peak time and pasting

temperature.

Statistical analysis:

Analysis of variance (ANOVA) and analysis of covariance (ANCOVA) were performed

using JMP (release 10, SAS institute, Cary, NC). Least significant difference (LSD) at a 5%

level of probability was determined to separate differences in the pasting properties among

treatments.

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Results and Discussion:

Chemical composition:

Table 1 presents moisture content, isolated protein, dietary fiber, total lipid and ash

content of heat stabilized rice bran (SRB) and its defatted rice bran (DFRB), rice bran proteins

(RBP) and rice bran fiber (RBF) fractions used as substitutes to create rice flour treatment.

Results illustrated the differences in chemical composition of each fraction as a result of

purification process. Defatting was able to remove most of the lipid from the heat stabilized rice

bran. For instance, rice bran protein extraction procedure resulted in 75.2% proteins in the

isolated samples. The increased protein percentage from 13.1% of stabilized rice bran to 17.4%,

when defatting, was a result of the increased contribution of proteins due to lipids removal (i.e., a

decrease in lipids content from 21.01% in stabilized rice bran to about 0.8% in the defatted rice

bran). In the same manner, protein and lipid removal resulted in the increased percentage of

fiber contribution to 32.4% of the called “rice bran fiber” compared to 8.4% in the heat stabilized

rice bran.

Effects of percent substitution of rice bran fraction on the pasting properties of rice flour:

Table 2 represents the pasting properties of long and medium grain rice flour substituted

with 5, 10, 15, 20 and 100% of DFRB, RBF, RBP and SRB. Replacement with rice bran

fractions resulted in a significant decrease (P<0.05) in rice flour pasting properties (i.e., peak,

final and setback viscosities, trough, breakdown, peak time and pasting temperature) across

cultivars used in this study. Figure 1 presents the effect of bran fractions on the overall paste

viscosity diagram of rice flour. Peak viscosity of long grain rice flour, for example, decreased

from 3638.5 (cP) of the 100% rice flour to 3180.5, 2836.5, 2437.0 and 2148.5 (cP) when 5, 10,

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15 and 20% of flour were respectively substituted with defatted rice bran. Replacing medium

grain rice flour with 5, 10, 15 and 20% rice fiber resulted in a decrease in peak viscosity to

3535.5, 3226.0, 2930.5, and 2675.5 (cP) respectively compared to 3984.0 (cP) of the 100%

medium grain rice flour. Replacing rice flour with rice bran proteins and stabilized rice bran

resulted in a similar trend.

The decrease in the pasting properties of long and medium grain rice flour as a result of

rice bran fractions substitution were related to the decreased contribution of rice starch in the

mechanism of rice paste formation. This finding was supported by the lower viscosity profiles of

rice flour substituted with fractions of stabilized rice bran as presented in Figure 1. The less

starch in a rice flour sample as a result of substituting with fractions of stabilized rice bran

resulted in fast swelling of starch granules to its maximum extent, weakening starch granules

resulting in an increasing their susceptibility be disrupted by shear (i.e. low paste viscosities).

This agrees with the findings of Derycke et al., (2005) that the keeping integrity of starch during

pasting results in greater forces required to shear the paste slurry and consequently greater paste

viscosity. It might be of significance here to indicate that during rice paste formation, proteins

and lipids tend to form an insoluble polymeric matrix surrounding starch granules conferring

rigidity to granules and also provides protection to the inregrity of the starch granules against

rupture (Grinberg and Tolstoguzov 1997 and Tester and Morrison 1990). Hamaker and Griffin

(1990) and Marshall et al., (1990) also indicated that the structure of proteins in rice kernels play

a key role in affecting rice functional properties. Substituting rice flour with rice bran proteins,

however, resulted in a decrease in rice flour pasting viscosities. These results were related to the

lack of protein’s ability to form appropriate bonding necessary for protecting swollen starch

granules integrity from rupture as well as the decrease in contribution of total starch available for

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swelling. For instance, Chrastil (1990), Chrastil and Zarins (1992) and Yang and Chang (1999)

indicated that the number of protein disulfide linkages and bound protein bodies to starch

granules significantly influence rice flour pasting properties. More specifically, Hamaker and

Griffin (1993) reported that intact protein disulfide bonds in rice flour are required for adding

strength to the gelatinized starch granules.

The decrease in pasting viscosities of flour samples substituted with RBP also suggests a

decrease in protein’s hydrophobicity. The low hydrophobicity of isolated rice proteins were

reported to limit the interaction between proteins and oils, resulting in the decrease of

emulsifying properties of added RBP (Halling 1981 and Phillips et al., 1994). This is on line

with the lower pasting viscosities observed in RBP substituted samples compared with the 100%

rice flour. Goel et al., (1999), in the same manner, presented the importance of hydrophilic

groups of proteins in the formation of starch protein cross-linkage and the protection of starch

granules from rupture. This is also in accordance with Wang et al., (1999) that native proteins

have a tendency to present their hydrophilic groups at the surface and bury their hydrophobic

groups into the core of the protein. Releasing proteins could have more hydrophilic groups on

the surface; thus lowering protein surface hydrophobicity (Saleh and Meullenet 2014). Our

results suggest that the rigidity of the formed protein-starch matrix conveyed to the increase in

pasting viscosity of rice flour. Elastic hair-like matrix (i.e., mostly fiber and proteins) could

provide evident of the rule of such matrix forming rice flour pasting viscosities. Hamaker and

Griffin (1990) also reported a potential effect of proteins on starch gelatinization. The

endosperm matrix protein and protein associated with starch granules, respectively, were

indicated to influence rice flour starch gelatinization properties. Substituting rice flour with

fractions of RBF results are in line with these findings.

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Rice flour fractions were long reported play a key role in determining changes in pasting

properties, especially during rice storage and aging (Villareal et al., 1976; Chrastil 1990 and

1992; Zhou et al., 2003 and Patindol et al., 2005). Formations of protein network were indicated

to provide protection for starch granules integrity resulting in increasing rice paste viscosity.

Results were supported by Shibuya and Iwasaki (1982) and Saleh and Meullenet (2007) findings

that disruption of such protein network, by protease treatment allowed the swollen gelatinized

granules during gelatinization to reach a maximum swelling and to rupture more readily.

The decrease breakdown of rice with the increase in percentage of rice bran proteins

substitution also supports our findings. Breakdown viscosity is usually associated with the

tendency of swollen starch granule to rupture during holding at high temperature accompanied

with continuous shearing (Fitzgerald et al., 2003 and Ribotta and Rosell 2010). Therefore, the

decrease in breakdown viscosity of flour substituted with fractions of RBP suggested that added

protein fractions were not functional enough to provide a required protection for rice starch

granules against rupture. On the contrary, added RBP resulted in increasing the amount of water

available for the total solids causing a reduction in pasting viscosities as starch granules would

have reached its maximum swelling and rupture with limited shear (Ribotta et al., 2007). Our

results agrees with Derycke et al., (2005) who reported that the amount of water available for

total solids during cooking plays a significant role in shaping rice functional properties.

In addition, substituting rice flour with defatted rice bran fraction resulted in decreasing

the net total starch content in each sample. Furthermore, lipids were long reported to form

inclusion complexes with amylose and amylopectin providing protection of starch granule's

integrity and increasing their resistance to rupture during shear (Banks and Greenwood 1975;

Vandeputte et al., 2003 and Yang and Chang 1999). The formation of these complexes was

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reported to restrict starch granule swelling during heating and prevented leaching of amylose

during gelatinization (Cui and Oats 1999 and SeneViratne and Biliaderis 1991). The decrease in

lipids contribution in paste formation (i.e., by the addition of defatted rice bran to rice flour)

apparently decreased the chances of forming such starch lipids complexes; decreased flour

pasting viscosities. These results are line with Cui and Oats (1999) and SeneViratne and

Biliaderis (1991) that starch lipids complexes play a significant role in determining flour paste

viscosity. The decrease in pasting viscosities of rice flour substituted with SRB (i.e., 21.1%

lipids) also provides support for our results. The decrease in rice paste viscosities of samples

substituted with percentages of stabilized rice bran and rice bran fiber were attributed to the

decrease in total starch content compared to rice flour samples.

Contribution of stabilized rice fractions to rice flour pasting properties:

Contributions of DFRB, RBF, RBP and SRB in the formation of rice flour pasting

properties is presented in table 3. Results showed that substituting rice flour with DFRB and

RBF produced the least change in flour pasting viscosities across cultivars and substitution ratio.

For instance, peak viscosity of long grain rice flour decreased from 3638.5 cP of the 0%

substitution to 3180.5 and 3168.5 cP when replacing 5% of rice flour with DFRB and RBF,

respectively compared with 2994.5 and 2953.5 cP when replacing with similar percentage of

RBP and SRB, respectively. A 20% substitution of medium grain rice flour with DFRB and

RBF resulted in a reduction of flour peak viscosity from 3984.0 cP to 2634.0 and 2675.5 cP of

the DFRB and RBF, respectively compared with 1786.0 and 2.241.5 cP when replacing similar

percentage of medium grain rice flour with RBP and SRB, respectively. Furthermore, for most

replacement fractions, there were no significant differences (P<0.05) between pasting properties

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of samples replaced with similar ratio of DFRB and RBF across cultivars. Pasting properties of

rice flour replaced with similar percentages of RBF and RBP, however, were significantly

different (P>0.05). Similar trends were reported form across 5, 10, 15 and 20% substitutions of

rice flour.

Table 2 also showed that substituting rice flour with isolated rice proteins resulted in the

lowest significant (P<0.05) pasting viscosities among samples substituted with rice bran

fractions. Starch, proteins, lipids and their interaction have long been reported to influence rice

functional properties (Eliasson and Gudmundsson 1996; Eliasson and Krog 1985 and Vandeputte

et al., 2003). Heating of rice flour causes protein and starch to interact forming complexes of

starch, proteins and lipids providing mechanical support for starch granules resulting in

increasing flour pasting viscosities (Derycke et al., 2005) which was further suggested that

pasting properties of flour resembles a net effect of the contribution of each component in

forming an average pasting profile. The dramatic decrease in pasting viscosities of isolated rice

bran proteins substituted samples was related to the lack of protein’s ability to form such

necessary bonding to protecting swollen starch granules integrity as discussed earlier.

The rates of overall change in pasting viscosities of rice flour substituted with 0, 5, 15

and 20% of each of the rice bran fractions were calculated and presented in Figure 3. Results

showed significance (P<0.05) pasting viscosity rate reductions with the substitution of various

fractions of rice bran. Analysis of covariance (ANCOVA) also showed a significant effect of the

substitution for fraction used in this study (Table 4). The greatest negative slopes of pasting

viscosities were reported when substituting flour with rice bran proteins. As discussed

previously, results suggested a net effect of the total starch reduction in each fraction resulting in

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the inability of isolated proteins in forming starch-protein matrix that protect swollen starch

granules integrity.

No significance (P>0.05) were reported for long grain flour breakdown, setback

viscosities as well as for pasting temperature and time when substituting with SRB fraction.

Significance:

Chemical composition as well as structural interaction of rice flour components plays a

critical role in determining rice flour pasting properties. Although considered minor flour

components; lipids and proteins that surround starch granules influence starch granules strength

during pasting that determine rice flour functionality. Results of this study support the

hypothesis that the formation of protein-starch and lipid-starch matrixes determines the

viscoelastic properties of rice flour paste.

Results indicated that not only protein-starch matrix but also the matrix rigidity

constituted to the net pasting viscosities of flour. It is believed that in a native rice starch

granules, the formation of such network contributed to protecting starch granules from rupture;

resulting in increasing rice paste resistance to shear and thus increasing its viscosity.

Furthermore, our results suggest that the disruption of proteins functionality during protein

extractions resulted in rendering protein unavailable to form starch matrixes increasing the

amount of water available for starch.

Acknowledgment:

The authors would like to thank Dr. George Ondier, Gulf Pacific Rice Co., Inc, Houston, TX for providing samples

and Mr. Waddah F. Mahmoud, The University of Jordan, Amman, Jordan for the kind help in data collection.

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Villareal, R. M., Resurreccion, A. P., Suzuki, L. B. and Juliano, B. O. 1976. Changes in

physicochemical properties of rice during storage. Starch/Stärke, 28: 88-94.

Wang, M., Hettiarchchy, N. S., Qi, M., Burks, W. and Siebenmorgen, T. 1999. Preparation and

functional properties of rice bran protein isolate. J. Agric. Food Chem. 47: 411-416.

Yang, C. H, Chang, W. H. 1999. Effects of protein and lipid binding to starch on the

physicochemical and pasting properties of rice flour. Food Sci. Agric. Chem. 1(3):277-85.

19

Zhou, Z., Robards, K., Helliwell, S., and Blanchard, C. 2003. Effect of rice storage on pasting

properties of rice flour. Food Res. International: 36: 625-634.

20

Figure 1: Pasting profile of long (LGRF) and medium (MGRF) rice flour substituted with 10% (left) and 15% (right) of Defatted rice bran (DFRB), Rice bran fiber (RBF), Rice bran proteins (RBP) and Stabilized rice bran (SRB).

0

1000

2000

3000

4000

5000

6000

7000

0 100 200 300 400 500 600 700 800 900

Time in seconds

Vis

cosi

ty (c

P)

LGRF

DFRB

RBF

RBP

SRB

0

1000

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4000

5000

6000

7000

0 100 200 300 400 500 600 700 800 900

Time in seconds

Vis

cosi

ty (c

P)

LGRF

DFRB

RBF

RBP

SRB

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3500

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4500

0 100 200 300 400 500 600 700 800 900

Time in seconds

Vis

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ty (c

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MGRF

DFRB

RBF

RBP

SRB

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1500

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4500

0 100 200 300 400 500 600 700 800 900

Time in seconds

Vis

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ty (c

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MGRFRBF

RBP

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DFRB

21

Figure 2: Rate of decrease in pasting properties of long and medium grain rice flour substituted with 0, 5, 10, 15, 20 and 100% of defatted rice bran (DFRB), rice bran fiber (RBF), rice bran proteins (RBP) and stabilized rice bran (SRB).

-160

-140

-120

-100

-80

-60

-40

-20

0RBP SRB DFRB RBF

Rice Fractions Replacement

Slop

e

Long grain rice flourMedium grain rice flour

Final Viscosity

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

RBP SRB DFRB RBF

Rice Fractions Replacement

Slop

e

Long grain rice flourMedium grain rice flour

Pasting Temperature

-120

-100

-80

-60

-40

-20

0RBP SRB DFRB RBF

Rice Fractions ReplacementSl

ope

Long grain rice flourMedium grain rice flour

Peak Viscosity

-70

-60

-50

-40

-30

-20

-10

0RBP SRB DFRB RBF

Rice Fractions Replacement

Slop

e

Long grain rice flourMedium grain rice flour

Trough Viscosity

-120

-100

-80

-60

-40

-20

0RBP SRB DFRB RBF

Rice Fractions Replacement

Slop

e

Long grain rice flourMedium grain rice flour

Breakdown Viscosity

-160

-140

-120

-100

-80

-60

-40

-20

0RBP SRB DFRB RBF

Rice Fractions Replacement

Slop

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Long grain rice flourMedium grain rice flour

Setback Viscosity

22

Table 1. Chemical composition of rice bran fractions used as substitutes to create rice

flour treatment

Component Stabilized Rice Bran1

Defatted Rice Bran

Rice Bran Proteins

Rice Bran Fiber

Moisture Content 6.3 a 4.2 c 5.1 b 4.4 c Protein 13.1 c 17.4 b 75.2 a 6.7 d Dietary Fiber

Insoluble Fiber 8.1 c 13.7 b 7.2 c 28.1 a Soluble Fiber 0.4 c 2.2 b 0.5 c 4.3 a

Total Fiber 8.5 c 15.9 b 7.7 c 32.4 a Total lipid content 21.1 a 0.8 b 0.5 b 0.5 b Ash 12.5 a 9.9 b 7.6 c 10.2 b

1Means of component of rice bran fractions with different letters are significantly (P<0.1) different according to least squares differences (LSD).

23

Table 2: Pasting properties of long and medium grain rice flour substituted with 0, 5, 10, 15, 20 and 100% of defatted rice bran, rice bran fiber, rice bran proteins and stabilized rice bran. 1, 2

Long Grain Rice Flour Medium Grain Rice Flour Replacement (%) Peak

Viscosity Trough Breakdown Final Viscosity

Setback Viscosity

Peak Time

Pasting Temp.

Peak Viscosity Trough Breakdown Final

Viscosity Setback Viscosity

Peak Time

Pasting Temp.

Defatted Rice Bran 0 3,638.5 a 2,680.0 a 958.5 a 6,289.0 a 3,609.0 a 5.7 b 82.7 c 3,984.0 a 1,759.5 a 2,224.5 a 3,072.0 a 1,312.5 a 5.7 b 76.3 d

5 3,180.5 b 2,519.0 b 661.5 b 5,588.5 b 3,069.5 b 5.8 b 84.4 b 3,475.5 b 1,661.0 ab 1,814.5 b 2,843.0 b 1,182.0 b 5.7 b 77.1 cd

10 2,836.5 c 2,361.5 c 475.0 c 4,998.5 c 2,637.0 c 5.9 b 84.8 b 3,186.5 c 1,554.0 bc 1,632.5 c 2,662.0 c 1,108.0 c 5.8 b 78.7 bc

15 2,437.0 d 2,112.5 d 324.5 d 4,363.5 d 2,251.0 d 5.9 b 86.0 a 2,817.5 d 1,429.0 cd 1,388.5 d 2,478.0 d 1,049.0 d 5.7 b 80.3 ab

20 2,148.5 e 1,888.0 e 260.5 e 3,875.0 e 1,987.0 e 5.9 b 86.4 a 2,634.0 e 1,343.5 d 1,290.5 e 2,356.5 d 1,013.0 d 5.7 b 81.1 a

100 95.5 f 87.0 f 8.5 f 215.0 f 128.0 f 6.9 a 0.0 d 95.5 f 87.0 e 8.5 f 215.0 e 128.0 e 6.9 a 0.0 e

Rice Bran Fiber 0 3,638.5 a 2,680.0 a 958.5 a 6,289.0 a 3,609.0 a 5.7 d 82.7 c 3,984.0 a 1,759.5 a 2,224.5 a 3,072.0 a 1,312.5 a 5.7 c 76.3 c

5 3,168.5 b 2,573.0 a 595.5 b 5,627.5 b 3,054.5 b 5.9 cd 84.8 b 3,535.5 b 1,759.5 a 1,776.0 b 2,979.5 b 1,220.0 b 5.8 bc 77.4 bc

10 2,871.0 c 2,368.5 b 502.5 c 4,888.0 c 2,519.5 c 6.0 bc 85.2 b 3,226.0 c 1,710.0 a 1,516.0 c 2,856.0 c 1,146.0 c 5.9 bc 79.1 b

15 2,508.0 d 2,124.0 c 384.0 d 4,232.0 d 2,108.0 d 6.0 b 86.3 a 2,930.5 d 1,598.5 b 1,332.0 d 2,689.0 d 1,090.5 d 5.9 b 82.8 a

20 2,228.0 e 1,931.5 d 296.5 e 3,752.5 e 1,821.0 e 6.0 b 86.9 a 2,675.5 e 1,515.0 b 1,160.5 e 2,523.5 e 1,008.5 e 5.9 bc 84.5 a

100 56.0 f 49.5 e 6.5 f 101.5 f 52.0 f 6.9 a 0.0 d 56.0 f 49.5 c 6.5 f 101.5 f 52.0 f 6.9 a 0.0 d

Rice Bran Proteins 0 3,638.5 a 2,680.0 a 958.5 a 6,289.0 a 3,609.0 a 5.7 b 82.7 c 3,984.0 a 1,759.5 a 2,224.5 a 3,072.0 a 1,312.5 a 5.7 b 76.3 c

5 2,994.5 b 2,511.5 b 483.0 b 5,423.5 b 2,912.0 b 5.8 b 85.5 b 3,252.5 b 1,426.0 b 1,826.5 b 2,543.5 b 1,117.5 b 5.5 c 77.9 bc

10 2,440.0 c 2,086.5 c 353.5 b 4,753.0 c 2,666.5 c 5.7 b 86.4 ab 2,751.0 c 1,281.5 c 1,469.5 c 2,296.5 c 1,015.0 c 5.5 c 79.9 b

15 1,931.0 d 1,752.5 d 178.5 c 4,015.5 d 2,263.0 d 5.9 b 86.8 ab 2,219.5 d 1,154.0 d 1,065.5 d 2,055.0 d 901.0 d 5.4 d 84.4 a

20 1,552.0 e 1,504.5 e 175.0 c 3,357.0 e 1,852.5 e 6.6 a 87.2 a 1,786.0 e 1,055.5 d 730.5 e 1,887.0 e 831.5 e 5.4 d 85.2 a

100 21.0 f 7.0 f 14.0 d 13.0 f 6.0 f 5.9 b 0.0 d 21.0 f 7.0 e 14.0 f 13.0 f 6.0 f 5.9 a 0.0 d

Stabilized Rice Bran 0 3,638.5 a 2,680.0 a 958.5 a 6,289.0 a 3,609.0 a 5.7 a 82.7 d 3,984.0 a 1,759.5 a 2,224.5 a 3,072.0 a 1,312.5 a 5.7 a 76.3 c

5 2,953.5 b 2,337.0 b 616.5 b 5,308.5 b 2,971.5 b 5.9 a 83.9 c 3,293.5 b 1,536.5 b 1,757.0 b 2,751.0 b 1,214.5 b 5.7 a 76.7 bc

10 2,491.5 c 2,086.5 c 405.0 c 4,504.5 c 2,418.0 c 5.9 a 84.4 bc 2,957.0 c 1,381.5 c 1,575.5 c 2,399.0 c 1,017.5 c 5.6 a 76.2 c

15 2,057.0 d 1,830.0 d 227.0 d 3,803.0 d 1,973.0 d 5.9 a 85.1 ab 2,596.0 d 1,231.0 d 1,365.0 d 2,148.0 d 917.0 d 5.6 a 77.4 b

20 1,761.0 e 1,595.0 e 166.0 d 3,286.0 e 1,691.0 e 5.9 a 85.6 a 2,241.5 e 1,088.0 e 1,153.5 e 1,911.5 e 823.5 e 5.6 a 79.9 a

100 22.0 f 17.5 f 4.5 e 37.0 f 19.5 f 5.0 b 0.0 e 22.0 f 17.5 f 4.5 f 37.0 f 19.5 f 5.0 b 0.0 d 1Means of pasting properties of rice flour substituted with various percentages of rice bran fractions with different letters are significantly (P<0.1) different according to least squares differences (LSD). 2 Peak, Final and Setback viscosities, Trough and Breakdown are measured in cP, Peak time in minutes and Pasting temperature in oC.

24

Table 3: Pasting properties of long and medium grain rice flour substituted with defatted rice bran (DFRB), rice bran fiber (RBF), rice bran proteins (RBP) and stabilized rice bran (SRB) at 0. 5, 10, 15, 20 and 100%. 1, 2

Long Grain Rice Flour Medium Grain Rice Flour Replacement

Type Replacement

(%) Peak Viscosity Trough Breakdown Final

Viscosity Setback Viscosity Peak

Viscosity Trough Breakdown Final Viscosity

Setback Viscosity

DFRB 3,180.5 a 2,519.0 a 661.5 a 5,588.5 ab 3,069.5 a 3,475.5 a 1,661.0 a 1,814.5 ab 2,843.0 b 1,182.0 ab

RBF 3,168.5 a 2,573.0 a 595.5 a 5,627.5 a 3,054.5 ab 3,535.5 a 1,759.5 a 1,776.0 bc 2,979.5 a 1,220.0 a

RBP 2,994.5 b 2,511.5 a 483.0 a 5,423.5 ab 2,912.0 c 3,252.5 b 1,426.0 c 1,826.5 a 2,543.5 c 1,117.5 b

SRB

5

2,953.5 b 2,337.0 a 616.5 a 5,308.5 b 2,971.5 bc

3,293.5 b 1,536.5 b 1,757.0 c 2,751.0 b 1,214.5 a

DFRB 2,836.5 a 2,361.5 a 475.0 ab 4,998.5 a 2,637.0 a 3,186.5 a 1,554.0 b 1,632.5 a 2,662.0 b 1,108.0 a

RBF 2,871.0 a 2,368.5 a 502.5 a 4,888.0 ab 2,519.5 b 3,226.0 a 1,710.0 a 1,516.0 ab 2,856.0 a 1,146.0 a

RBP 2,440.0 b 2,086.5 b 353.5 b 4,753.0 b 2,666.5 a 2,751.0 c 1,281.5 d 1,469.5 b 2,296.5 d 1,015.0 b

SRB

10

2,491.5 b 2,086.5 b 405.0 ab 4,504.5 c 2,418.0 b

2,957.0 b 1,381.5 c 1,575.5 ab 2,399.0 c 1,017.5 b

DFRB 2,437.0 a 2,112.5 a 324.5 b 4,363.5 a 2,251.0 a 2,817.5 b 1,429.0 b 1,388.5 a 2,478.0 b 1,049.0 a

RBF 2,508.0 a 2,124.0 a 384.0 a 4,232.0 a 2,108.0 b 2,930.5 a 1,598.5 a 1,332.0 b 2,689.0 a 1,090.5 a

RBP 1,931.0 c 1,752.5 c 178.5 d 4,015.5 b 2,263.0 a 2,219.5 d 1,154.0 d 1,065.5 c 2,055.0 c 901.0 b

SRB

15

2,057.0 b 1,830.0 b 227.0 c 3,803.0 c 1,973.0 c

2,596.0 c 1,231.0 c 1,365.0 a 2,148.0 c 917.0 b

DFRB 2,148.5 a 1,888.0 a 260.5 a 3,875.0 a 1,987.0 a 2,634.0 a 1,343.5 b 1,290.5 a 2,356.5 b 1,013.0 a

RBF 2,228.0 a 1,931.5 a 296.5 a 3,752.5 a 1,821.0 b 2,675.5 a 1,515.0 a 1,160.5 b 2,523.5 a 1,008.5 a

RBP 1,552.0 c 1,504.5 c 175.0 b 3,357.0 b 1,852.5 b 1,786.0 c 1,055.5 c 730.5 c 1,887.0 c 831.5 b

SRB

20

1,761.0 b 1,595.0 b 166.0 b 3,286.0 b 1,691.0 c

2,241.5 b 1,088.0 c 1,153.5 b 1,911.5 c 823.5 b

DFRB 95.5 a 87.0 a 8.5 ab 215.0 a 128.0 a 95.5 a 87.0 a 8.5 ab 215.0 a 128.0 a

RBF 56.0 b 49.5 b 6.5 ab 101.5 b 52.0 b 56.0 b 49.5 b 6.5 ab 101.5 b 52.0 b

RBP 21.0 c 7.0 c 14.0 a 13.0 d 6.0 d 21.0 c 7.0 c 14.0 a 13.0 d 6.0 d

SRB

100

22.0 c 17.5 c 4.5 b 37.0 c 19.5 c

22.0 c 17.5 c 4.5 b 37.0 c 19.5 c 1Means of pasting properties of rice flour substituted with the same percentages of various rice bran fractions with different letters are significantly (P<0.1) different according to least squares differences (LSD). 2 Peak, Final and Setback viscosities, Trough and Breakdown are measured in cP, Peak time in minutes and Pasting temperature in oC

25

Table 4: Analysis of covariance (ANCOVA) of the substitution type and percentage of stabilized rice bran incorporated in long and medium grain rice flour

Long Grain Rice Flour Medium Grain Rice Flour Pasting Properties Effect Tests

Sum of Squares F Ratio Prob > F1 Sum of Squares F Ratio Prob > F

Substitution type 526130.2 23.43 <0.0001 695448.5 24.87 <0.0001 Substitution % 7304266.2 975.93 <0.0001 6554116.8 703.10 <0.0001 Peak Viscosity (cP) Substitution type* Substitution % 200001.7 8.91 0.0022 308362.7 11.03 0.0009 Substitution type 465593.0 15.35 0.0002 645113.7 46.12 <0.0001 Substitution % 18639076.0 1843.31 <0.0001 2009728.9 430.99 <0.0001 Final Viscosity (cP) Substitution type* Substitution % 139416.0 4.60 0.0231 177428.2 12.68 0.0005 Substitution type 85016.3 2.29 0.1299 50403.5 17.95 <0.0001 Substitution % 7727728.6 625.70 <0.0001 384846.3 411.05 <0.0001 Setback Viscosity

(cP) Substitution type* Substitution % 37426.1 1.01 0.4221 24703.0 8.80 0.0023 Substitution type 65041.8 2.30 0.1297 116073.1 5.40 0.0139 Substitution % 1357738.3 143.80 <0.0001 3107505.0 433.82 <0.0001 Breakdown

Viscosity (cP) Substitution type* Substitution % 20431.9 0.72 0.5583 127872.7 5.95 0.0100 Substitution type 237772.3 34.92 <0.0001 337675.6 49.76 <0.0001 Substitution % 2363661.3 1041.29 <0.0001 635670.2 281.04 <0.0001 Trough Viscosity

(cP) Substitution type* Substitution % 95082.2 13.96 0.0003 73784.7 10.87 0.0010

1 Probability values (F<0.05) are significant according to the LSD