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Effect of Aging on the Quality of Glutinous Rice Crackers

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Abstract

Cereal Chem. 74(1):12-15 The experiment was conducted to study the effects of aging on the physicochemical properties of two Thai cultivars of milled gluti nous rice (RD6 and RD8). The amylose and protein content of rice samples did not change when stored from 0 to 4 months. Amylograph curves from sam- ples of milled rice stored from 0 to 8 months were analyzed. Both culti- vars gave constant gelatinization temperature during aging. The values for peak viscosity, final viscosity on cooking at 94ºC, viscosity on cool- ing to 50ºC and breakdown decreased significantly for RD6 cu ltivar, whereas the setback value and consistency were not changed signifi- cantly. For RD8 cultivar, no significant difference was observed for vis- cosity on cooling to 50ºC and consistency during aging up to 8 months. Peak viscosity and breakdown value were reduced during storage, whereas the final viscosity on cooking at 94ºC and setback value in- creased with time. Raw milled rice of both RD6 and RD8 cultivars have similar water uptake rates. Stored rice tended to have a lower water uptake rate which increased proportionately with soaking time. Samples from both rice cultivars were used to make rice crackers to st udy the effects of aging on quality. Volume expansion of rice crackers made from RD6 and RD8 cultivars tended to decrease during storage which resulted in an increase in the hardness of the crackers.
12 CEREAL CHEMISTRY
NONWHEAT GRAINS AND PRODUCTS
Effect of Aging on the Quality of Glutinous Rice Crackers
ATHAPOL NOOMHORM,1 NGAMCHUEN KONGSEREE, and MUANMAI APINTANAPONG
ABSTRACT Cereal Chem. 74(1):12–15
The experiment was conducted to study the effects of aging on the
physicochemical properties of two Thai cultivars of milled glutinous rice
(RD6 and RD8). The amylose and protein content of rice samples did not
change when stored from 0 to 4 months. Amylograph curves from sam-
ples of milled rice stored from 0 to 8 months were analyzed. Both culti-
vars gave constant gelatinization temperature during aging. The values
for peak viscosity, final viscosity on cooking at 94ºC, viscosity on cool-
ing to 50ºC and breakdown decreased significantly for RD6 cultivar,
whereas the setback value and consistency were not changed signifi-
cantly. For RD8 cultivar, no significant difference was observed for vis-
cosity on cooling to 50ºC and consistency during aging up to 8 months.
Peak viscosity and breakdown value were reduced during storage,
whereas the final viscosity on cooking at 94ºC and setback value in-
creased with time. Raw milled rice of both RD6 and RD8 cultivars have
similar water uptake rates. Stored rice tended to have a lower water uptake
rate which increased proportionately with soaking time. Samples from
both rice cultivars were used to make rice crackers to study the effects of
aging on quality. Volume expansion of rice crackers made from RD6 and
RD8 cultivars tended to decrease during storage which resulted in an
increase in the hardness of the crackers.
Glutinous rice (Oryza sativa), also called waxy or sweet rice, is
characterized chiefly by its lack of amylose in the starch (Bean et
al 1984). It has been grown in the Orient for many centuries and
has found extensive use in certain traditional pastries, confections,
and other foods in Asia (Whistler and Paschall 1967). The kernels
of all glutinous rice are sticky and adhere to one another, provid-
ing a product with a decidedly different texture when compared to
amylose-containing rice (Bean et al 1984). The preparation of
various rice desserts and sweets utilizes the sticky, soft nature of
cooked waxy rice and its slower rate of retrogradation or harden-
ing relative to cooked nonglutinous rice. Glutinous or waxy rice is
commonly used in the preparation of baked or popped snacks
because it expands readily and produces a more porous texture.
Rice cracker is one of the numerous Japanese baked snack
foods made from rice. Arare (made from glutinous rice) and Senbei
(made from nonglutinous rice) are the major and traditional rice
crackers in Japan (Li and Luh 1980). In glutinous rice cracker
processing, milled rice is washed and soaked for 16–20 hr, then
drained and crushed by rollers into a fine powder. After steaming
for 15–30 min, the resulting rice dough or cake is kneaded and
cooled to 2–5ºC for two to three days for hardening. The hard
cake is cut, dried, and baked to produce various types of glutinous
rice crackers. The soft texture and flavor of these products are
quite different from western snacks.
In Thailand, RD6 and RD8 (two glutinous rice cultivars) are
commonly used as raw materials in the production of rice crackers
using processing technology transferred from Japan although
many practical problems exist in the manufacture of these prod-
ucts. Some problems arising from processing conditions have
been studied and solved by experience, but those occurring from
changes in rice properties (e.g., aging effect) are still unresolved.
According to manufacturers in Thailand, crackers produced from
rice that has been stored for about one year have reduced volume
expansion. By experience, manufacturers have solved this prob-
lem by mixing aged rice with fresh rice. This practical method,
however, does not always work.
Understanding the mechanism of expansion is important in order
to produce high quality rice crackers. Investigations concerning
rice cracker expansion have focused on the effects of cultivar,
heating temperature, kneading method, rice cake moisture content,
distribution of water absorption, and uniformity of steamed rice
(Li and Luh 1980). Information concerning the effects of aging of
rice on the physicochemical properties of rice crackers is limited.
Therefore, the objectives of the present study were to determine
the effects of aging on the physicochemical properties of two spe-
cific cultivars of Thai glutinous rice (RD6 and RD8) and the
quality of the rice crackers prepared from them.
MATERIALS AND METHODS
Milled Glutinous Rice
Freshly milled Thai glutinous rice of RD6 and RD8 cultivars
from the Khon Kaen Province in the northeastern part of Thailand
were used in this experiment. For each cultivar, a stock of milled
glutinous rice was stored at ambient temperature (28–30ºC) and
samples for ten replicates were taken for study at the end of each
month for a period of four months.
Physicochemical Analysis of Milled Glutinous Rice
The moisture content of milled glutinous rice was determined
using the AOAC Standard (Oven) Method.
The method adopted by Juliano (1971) was used to determine
amylose content of rice flour samples. Flours were obtained from
the milled rice using a Brabender Quadrumat Junior Mill fitted
with a Brabender reel sifter, No. 64 grit gauge. A standard curve
was established using standard amylose obtained from the Pathum
Thani Rice Research Center, Pathum Thani province, Thailand.
The alkali digestibility test introduced by Little et al (1958) was
used in this study. The method involved incubation of ten grains
of milled rice in 27 mL of 1.7% KOH at room temperature for 24 hr
and measurement of the degree of spreading using a 7-point scale.
Gelatinization temperature and pasting properties of each sam-
ple were determined using a C.W. Brabender Amylograph
equipped with a 700 cm•g sensitivity cartridge and a cooling coil.
The method of Halick and Kelly (1959) was used which entails
heating the sample prepared as 10% slurry (50 g of rice flour in
450 mL of water) to 94ºC during which the peak viscosity was
obtained. The sample was held at 94ºC for 20 min then cooled to
50ºC. Gelatinization temperature was taken as the temperature
when the viscosity curve starts to deviate from the zero baseline.
The protein content of the rice flour was determined by the
micro-Kjeldahl method. The value for the factor used in the pro-
tein content calculation was 5.95 (Juliano 1985).
1School of Environment, Resources and Development Agricultural and Food
Engineering Program, Asian Institute of Technology, Bangkok, Thailand.
Publication no. C-1997-0101-03R.
© 1997 by the American Association of Cereal Chemists, Inc.
Vol. 74, No. 1, 1997 13
Samples of rice (20 g) were soaked in 100 mL of distilled water
at 22–24ºC for different durations up to 16 hr. After the desired
soaking period, the water was carefully drained. The increase in
weight of the drained rice was calculated as percentage absorbed
by twenty grams of rice (Bean et al 1984).
Preparation of Glutinous Rice Crackers
Milled glutinous rice was washed and soaked for 16–20 hr in
water kept <20ºC. After soaking, the moisture content of the
drained rice was 38% wb. The drained rice was crushed by rollers
into fine powder and steamed in a pressure cooker at 115ºC for 20
min. The resulting dough was kneaded eight times using a screw
kneader. The kneaded cake was placed in a cake vessel and allowed
to harden for three days at 2–5ºC. Using a cutting machine, the
hard cake was cut into small pieces with approximate dimensions
of 4.5 × 1.3 × 0.4 cm. These small pieces of hard cake were dried
by hot air at 45ºC for 3–3.5 hr to a final moisture content of 20%
wb and then baked at 300ºC to obtain rice crackers.
Physical Evaluation of Glutinous Rice Crackers
The physical tests conducted on the rice cracker samples were
volume expansion before and after baking, and textural charac-
terization of rice crackers after baking. For each parameter, ten
replicates were conducted for each treatment.
Volume Expansion Determination
The length and width of rice crackers before and after baking
were measured using a Vernier caliper while the thickness was
determined using a micrometer. Volume expansion was computed
from these measurements.
Textural Determination
To eliminate the effects of varying moisture contents, samples
of the product were stored in a desiccator for a minimum of one
week before analysis. Texture was measured on an Instron univer-
sal testing machine (UTM model 1140) fitted with a cylindrical
probe. Each sample was placed on a 1.25-cm thick aluminum
plate with a 1.6-cm dia hole to allow the probe to pass through
after punching through the cracker sample. The crackers were
punched through completely, and the peak resistance force during
the test was recorded as the apparent hardness of the crackers. The
hardness was evaluated using a 4.0-mm probe with chart and
crosshead speed of 100 mm/min.
Statistical Analysis
Statistical analysis was conducted using analysis of variance
(ANOVA). Significant calculated mean values were compared
using Duncan’s multiple range test at α = 0.05 level of signifi-
cance.
RESULTS AND DISCUSSION
Effects of Aging on Physicochemical Properties of Milled
Glutinous Rice
Table I shows the physicochemical properties of RD6 and RD8
milled glutinous rice at different storage durations from 0 to 4
months. It was observed that the RD8 cultivar has significantly
higher amylose content (6.85%) when compared to RD6 with only
5.93%. During four months of storage, amylose content of the two
rice cultivars did not change significantly. Similar results during
storage were reported by some investigators (Barber 1972, Vil-
lareal et al 1976, Indudhara Swamy et al 1978, Juliano 1985),
while another reported that amylose and amylopectin fractions
changed (Barber 1972). Chrastil (1990) found that amylose con-
tent in starch from rice grains stored for 12 months increased
slightly during storage.
Protein content of both cultivars (7.18% for RD6 and 7.15% for
RD8) did not differ significantly even after storage at various du-
rations. Similar results (no change in total nitrogen content during
storage) were reported by researchers (Barber 1972, Villareal et al
1976, Juliano 1985). Even though no gross chemical composition
change in rice grain during storage was observed, Chrastil (1990)
revealed that interactions between protein and starch may occur
resulting in an increase in disulfide bonds and average molecular
weight of oryzenin (storage protein in rice grain). Furthermore,
the average molecular weight of amylose may decrease but that of
amylopectin could increase during storage. Oryzenin could have
interacted with starch by reversible binding with amylopectin or
amylose. Moreover, Juliano (1985) reported that protein oxidation
can be accelerated by free fatty acids formed from lipids which
can form a complex with amylose, carbonyl compounds, and hy-
droperoxide.
Alkali tests for the two cultivars studied yielded the same
results. The value obtained (7)indicated that both RD6 and RD8
had gelatinization temperature less than 70ºC. All in all, the alkali
test value and the amylose and protein content for RD6 and RD8
cultivars remain unchanged during storage from 0 to 4 months.
TABLE II
Amylograph Characteristics of Fresh and Stored Milled RD6 and RD8 Glutinous Ricea
Storage Time Gelatinization Viscosity (Brabender Units)
Cultivar (months) Temperature (ºC) Peak Viscosity Final Viscosity Cool to 50ºC Setback Consistency Breakdown
RD6 0 61.12 ± 0.38a 755 ± 15a 485 ± 15a 630 ± 10a –125 ± 5a 145 ± 5a 270 ± 0a
2 59.80 ± 1.00a 595 ± 35b 470 ± 20a 545 ± 45a –50 ± 8b 75 ± 6.5a 125 ± 15b
4 60.75 ± 0.00a 510 ± 0b 440 ± 0a 570 ± 0a 60 ± 0b 130 ± 0a 70 ± 0c
8 61.50 ± 0.50a 390 ± 30c 307 ± 22.5b 422 ± 22.5b 32 ± 7.5ab 117 ± 2.5a 82 ± 7.5c
RD8 0 61.80 ± 0.30a 620 ± 10a 260 ± 0.0a 320 ± 40a –300 ± 5a 60 ± 4a 360 ± 10a
2 62.50 ± 1.00a 595 ± 15ab 300 ± 0.0b 425 ± 15b –170 ± 0b 125 ± 15a 295 ± 15b
4 62.02 ± 0.22a 555 ± 25bc 320 ± 10.0bc 440 ± 20b –115 ± 5bc 120 ± 10a 235 ± 15c
8 62.50 ± 0.50a 495 ± 5c 322 ± 2.5c 430 ± 10b –65 ± 5c 107 ± 7.5a 172 ± 2.5d
aMean values followed by the same letter in the same column are not significantly different at 5% level by Duncan’s Multiple Range Test.
TABLE I
Some Physicochemical Properties of RD6 and RD8 Glutinous Ricea
Cultivar
Storage
Time
(months)
Moisture
Content
(%)
Amylose
Content
(%)
Protein
Content
(%)
Alkali
Test
Value
RD6 0 13.28 5.77a 7.14a 7
1 13.17 6.03a 7.09a 7
2 13.22 5.93a 7.27a 7
3 13.31 5.81a 7.18a 7
4 13.53 6.09a 7.21a 7
RD8 0 13.79 6.76b 7.25a 7
1 13.78 6.76b 7.15a 7
2 13.84 6.89b 7.19a 7
3 13.84 6.89b 7.06a 7
4 13.91 6.95b 7.12a 7
aEach value is the average of three replicates. Mean values followed by the same
letter in the same column are not significantly different both at 1% and 5%
significance levels by Duncan’s Multiple Range Test.
14 CEREAL CHEMISTRY
Amylograph Characteristics
The values obtained from the amylograph (in BU) were peak
viscosity, final viscosity on cooking at 94ºC, and viscosity on
cooling to 50ºC. From these three values, breakdown is calculated
as the decrease in viscosity (in BU) during cooking at 94ºC; set-
back is the viscosity when cooled to 50ºC minus peak viscosity;
and consistency is the viscosity when cooled to 50ºC minus final
cooking viscosity at 94ºC. The values for these selected parame-
ters from the amylograph curves of rice samples of both cultivars
stored for different durations are summarized in Table II.
The average gelatinization temperature of RD6 and RD8 culti-
vars when aged from 0 to 8 months were 60.79 and 62.21ºC,
respectively. Statistical analysis showed that all samples from
each cultivar have no significant difference in gelatinization tem-
perature for different storage durations.
From the amylograph curves of milled rice samples stored from
0 to 8 months, the RD6 cultivar showed significant decrease in
peak viscosity, final viscosity on cooking at 94ºC, viscosity on
cooling to 50ºC and breakdown value, while setback and consis-
tency values were not altered significantly. On the other hand, no
significant difference was observed for viscosity on cooling to
50ºC and consistency during aging up to eight months for RD8
cultivar. Peak viscosity and breakdown value were reduced during
storage, whereas the final viscosity on cooling at 94ºC and setback
value increased with time.
The change in some of the amylograph properties during aging
0 to 8 months can be attributed to some characteristics of the
starch granules. As reported by Whistler and Paschall (1965), the
height of peak during the heating part of the cycle is a measure of
the ability of the granules to swell markedly before rupture. The
trend obtained for peak viscosity of both RD6 and RD8 cultivars
shows that the starch granules of stored rice were more resistant to
swelling than were those of fresh rice. The decrease in breakdown
value indicated that the capacity of the starch granules to rupture
after cooking was reduced significantly due to aging.
The decrease in peak viscosity and breakdown value of the cul-
tivars studied seemed to contradict the results of some previous
studies (Villareal et al 1976, Perez and Juliano 1981, Bean et al
1984). Nevertheless, the final viscosity on cooking at 94ºC and
setback value for RD8 cultivar increased during aging which is in
agreement with the reported results of these previous studies
mentioned.
Varying trends in amylograph pasting viscosity had been
observed in previous studies during storage of both waxy and
nonwaxy rice. Some reports showed increased viscosity in stored
rice (Barber 1972, Villareal et al 1976, Indudhara Swamy et al
Fig. 2. Water uptake during soaking of milled glutinous rice (RD8) stored
for durations from 0 to 4 months.
Fig. 1. Water uptake during soaking of milled glutinous rice (RD6) stored
for durations from 0 to 4 months.
Fig. 4. Hardness of crackers made from RD6 and RD8 rice cultivars
stored for durations from 0 to 4 months. Standard error ±0.13 kg at 5%
significance level for 10 replicates.
Fig. 3. Volume expansion of crackers made from RD6 and RD8 rice
cultivars stored for durations from 0 to 4 months. Standard error ±8% at
5% significance level for 10 replicates.
Vol. 74, No. 1, 1997 15
1978, Perez and Juliano 1981, Bean et al 1984, Juliano 1985),
while others found no significant change such as in stored Japa-
nese rice (Juliano 1985) and Spanish rice (Barber 1972). On the
other hand, Juliano (1985) reported lower peak viscosity in
starches prepared from stored Taiwan rice.
As described by Juliano (1985), the aging mechanism involves
lipids, protein, and starch. Lipids form free fatty acids that can
form a complex with amylose and carbonyl compounds as well as
hydroperoxide. These complexes can accelerate protein oxidation
and condensation plus accumulation of volatile carbonyl com-
pounds. Protein oxidation, together with an increase in the
strength of micelle binding of starch, inhibits swelling of starch
granules and affects cooked rice texture. Protein oxidation also
reduces the level of volatile sulfur compounds. The relatively high
α-amylase activity in freshly harvested grain has been considered
as the possible mechanism for the pastiness of cooked freshly
harvested rice. However, α-amylase is concentrated in the bran
fraction, thus the residual α-amylase activity in milled rice is low
and cannot be considered as the cause of low amylograph
viscosity of waxy milled rice flour.
Water Uptake of Raw Milled Glutinous Rice
In Asian societies where rice is a dietary staple, rice is com-
monly soaked in water for several hours before cooking. The
water uptake during this hydration period serves as a useful crite-
rion for quality evaluation of rice cultivars. Trends of water uptake
of RD6 and RD8 cultivars are shown in Figs. 1 and 2, respectively.
The data obtained showed similar trends for the two cultivars.
Water was absorbed rapidly in the first hour and reached steady
state in about 2 hr. Freshly milled rice had the highest water uptake
rate followed by rice stored for 1, 2, 3, and 4 months, respectively.
Most of the water was taken up in 1 hr and as Bean et al (1984)
reported, equilibration of moisture throughout the kernels took
place for the remainder of the soaking period.
Stored rice takes more time to reach the same level of water
uptake as fresh rice. This phenomenon, however, does not affect
the quality of glutinous rice crackers due to the long period of
soaking (16–20 hr) done during processing. Soaking time for these
two glutinous rice cultivars (stored for 0 up to 4 months) may be
reduced to durations less than the original rice cracker process and
still achieve the desired effect since prolonging the soaking period
beyond the point when the water uptake rate becomes almost
steady-state does not significantly increase the total water uptake.
Effect of Aging on Quality of Glutinous Rice Crackers
Processing of glutinous rice crackers ends with baking at high
temperature during which the dried rice cakes expand to the desired
shape and size. The quality of the final product can be evaluated
in terms of volume expansion and hardness of the rice crackers.
Volume Expansion of Glutinous Rice Crackers
As presented in Figure 3, these two cultivars (RD6 and RD8)
showed the same trend of volume expansion even at different
storage times (from 0 up to 4 months). Statistical analysis showed
that the volume expansion of crackers made from the two culti-
vars were not significantly different. Volume expansion of crack-
ers made from fresh rice (395%) and milled rice stored for two
months (376%) for RD6 cultivar were also not different signifi-
cantly. At the 95% significance level, rice stored for four months
has significantly lower volume expansion (347%) compared to
rice stored for two months. An almost similar trend was obtained
for RD8 cultivar. Fresh rice and rice stored for two months have sig-
nificantly different volume expansion (388% and 359%, respec-
tively), but rice stored for four months (345%) gave no significant
difference relative to the rice stored for two months. Volume
expansion was the most important characteristic of rice snacks
and cracker products (Li and Luh 1980). However, various cereals
and starches do not expand equally due to differences in the
quality of its component materials. The branched structure of
starches and their constituents seem to control expansion of
cereals. Chinnaswamy (1993) reported that changes in the
branched fraction of starches greatly affect volume expansion.
During aging, changes in the starch structure and components
occurred (as reported by Bean et al 1984), causing the decrease in
volume of crackers made from stored rice. Volume expansion data
for crackers made from rice stored at different durations could be
useful in setting the process conditions for manufacturing rice
crackers. To produce better quality rice crackers, appropriate
processing conditions can be modified to make use of the
desirable properties of fresh and aged milled rice, taking into
account the difference in cost of each type.
Hardness of Glutinous Rice Crackers
The hardness of crackers was determined by probing method.
As shown in Figure 4, both cultivars showed the same trend of
hardness at different storage durations. Hardness tended to increase
with storage time although the hardness of crackers made from fresh
rice and rice stored for two months were not significantly different.
Crackers made from rice stored for two and four months also gave no
significant difference in hardness at the same level of significance.
Hardness of crackers seemed to correlate negatively with its volume
expansion. Higher hardness values were observed for crackers with
less volume expansion and vice versa, thus the effect of aging influ-
enced both volume expansion and hardness of glutinous rice crackers.
The change in some amylograph properties of the stored rice
affected both the volume expansion and hardness of rice crackers.
The reduction in the peak viscosity during aging and the increased
resistance of starch granules to swelling may have affected the
volume expansion and hardness of the rice crackers.
LITERATURE CITED
BARBER, S. 1972. Milled rice and changes during aging. Pages 215-263
in: Rice: Chemistry and Technology, 1st ed. D. F. Houston, ed. Am.
Assoc. Cereal Chem.: St. Paul, MN.
BEAN, M. M., ESSER, C. A., and NISHITA, K. D. 1984. Some physico-
chemical and food application characteristics of California waxy rice
varieties. Cereal Chem. 61:475-480.
CHINNASWAMY, R. 1993. Basis of cereal starch expansion. Carbohydr.
Polym. 21:157-167.
CHRASTIL, J. 1990. Protein-starch interactions in rice grains. Influence
of storage on oryzenin and starch. J. Agric. Food Chem. 38:1804-1809.
HALICK, J. V., and KELLY, V. J. 1959. Gelatinization and pasting character-
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INDUDHARA SWAMY, Y. M., SOWBHAGYA, C. M., and BHAT-
TACHARYA, K. R. 1978. Changes in the physicochemical properties
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JULIANO, B. O. 1971. A simplified assay for milled rice amylose.
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JULIANO, B. O. 1985. Rice Chemistry and Technology. Am. Assoc.
Cereal Chem.: St. Paul, MN.
LITTLE, R. R., HILDER, G. B., and DAWSON, E. H. 1958. Differential
effect of dilute alkali on 25 varieties of milled white rice. Cereal
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LI, C.-F., and LUH, B. S. 1980. Rice snack foods. Pages 690-711 in:
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PEREZ, C. M., and JULIANO, B. O. 1981. Texture changes and storage
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JULIANO, B. O. 1976. Changes in physicochemical properties of rice
during storage. Starch/Staerke 28:88-94.
WHISTLER, R. L., and PASCHALL, E. F. 1965. Starch: Chemistry and
Technology. Vol. I. Academic Press: New York.
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[Received December 14, 1995. Accepted September 21, 1996.]
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An efficient postharvest system aims to minimize the loss and obtained the good quality rice gain. This review summarizes the information regarding the postharvest processing published by various authors and outline the evidence that support the impacts of the postharvest handling on rice grain quality. Grain quality, includes a summary of the physical and chemical characteristics of rice grain. It has many components such as nutritional value, appearance, cooking and eating quality. Drying of rice mainly affects the milling quality, as most breakage of rice occurs because of grain fissuring. Rice ageing occurs during storage is responsible for the changes in pasting properties, color, flavor and chemical composition such as starch, protein, lipid etc. that affect rice quality. Therefore, research on various drying methods, storage conditions and milling methods should be maximized and maintain the desired rice grain quality. This review may contribute to understand the impacts of postharvest processes on grain quality and can increase the head rice yield.
... Therefore, brown rice is listed as a whole-grain healthy food by the U.S. Food and Drug Administration (FDA), which advocates eating it straight. Storage is a necessary stage from harvest to rice consumption and should be carefully controlled because a large number of physical, chemical and physiological changes occur during storage, which greatly affect the final quality of rice [6,7]. However, due to the loss of the protection given by the rice husk, brown rice embryos and endosperms are exposed and easily damaged by mechanical mechanisms. ...
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The effects of storage temperature on the physicochemical properties and qualities of red brown rice were investigated in this study. The samples were vacuum-packed in nylon/polyethylene pouches and stored at 15 °C, 25 °C and 35 °C for 12 weeks. The moisture content decreased as storage time was prolonged. Rice stored at 15 °C and 25 °C had a lower falling range of water content compared to the samples stored at 35 °C. Free fatty acid values increased fastest when samples were stored at a high temperature, and the rise can be effectively delayed at low temperatures. The pH of residual cooking water and adhesiveness decreased, while the heating water absorption rate and hardness increased during storage for red and brown rice. Low-field nuclear magnetic resonance results indicate that water molecules migrated, the binding force of H protons became stronger and the bonds between molecules became closer with increased storage duration. Temperature had an obvious correlation with starch granules and protein structure, characterized by a scanning electron microscope and Fourier transform infrared spectroscopy. Low temperatures significantly retarded those changes. The results indicate that storage temperature is a vital factor affecting the physicochemical properties and qualities of red brown rice and provided reference and theoretical basis for the actual storage of red brown rice.
... Rice flour is steamed, kneaded, cooled, dried, and baked. [2] A few patents have been issued for Japanese rice cracker manufacturing methods, including a technique of making senbei in different shapes, [3] a method of manufacturing non-glutinous rice crackers by milling nonglutinous rice, [4] and production of a high-amylose rice cracker with dietary fiber. [5] Western style wheat crackers can be divided into three types: saltine cracker (soda cracker), chemically leavened cracker, and enzyme cracker. ...
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Three varieties of dry-milled rice flour – Angemi (low amylose), Saemimyun, and Saegoami (high amylose) – were compared with wheat flour for cracker manufacture. A method to prepare saltine crackers with rice flour, hydroxyl propyl methyl cellulose, sugar, and controlled water addition using one-stage fermentation with gelatinization prior to lamination of fermented dough was developed. Stickiness of gelatinized laminated sheets and cracker volume and thickness were highest in Angemi (P< .05), and hardness and fracturability were highest in Saemimyun crackers. Amylose content negatively correlated with cracker volume (P< .05) and thickness (P< .05), whereas damaged starch content positively correlated with cracker moisture content (P< .01) and negatively with hardness (P< .01) and fracturability (P< .001). It was observed that both amylose and damaged starch contents of flour affect rice cracker quality.
... During storage, endosperm gets hardened decreases capacity of starch and water soluble molecules like reducing sugars and soluble proteins (Cameron and Wang, 2005;Perdon et al., 1997). Actually, storage lowers amylase leading granular starch structure crystalline resulting formation of less amounts of soluble solids like reducing sugars with consequent decrease in loss of cooking solids (Patindol and Wang, 2003;Noomhorm et al., 1997;Yasmumatsu et al., 1965). ...
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