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Study on the period of acceptability of cooked rice

Authors:
  • Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh

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The study attempts to determine the period of acceptability of cooked rice (parboiled) of Pajam variety. Cooling studies on cooked rice showed the highest cooling rate in soaked water, and successively followed by refrigeration, under fan air and at room temperature (30±2 0 C). The moisture, protein, fat, ash and total carbohydrate contents (wb) were 9.68, 4.93, 0.36, 0.32 and 84.71 % respectively in raw rice; 12.37, 8.36, 0.40, 0.57 and 78.29 % respectively in parboiled rice and 65.99, 3.24, 0.15, 0.14 and 30.47 % respectively in cooked rice (parboiled). After 24 hours of storage moisture, protein, fat, ash and carbohydrate contents were 66.47%, 5.69%, 0.13%, 0.14% and 15.73% respectively in rice at room temperature; 69.12 %, 3.64 %, 0.13 %, 0.13 % and 26.98 % respectively in refrigerated rice and 64.38 %, 3.53 %, 0.15 %, 0.15% and 31.78 % respectively in frozen rice. The cooked rice stored at room temperature for 24 hours showed 4.2x10 4 cfu/g, and the refrigerated and frozen rice showed no viable load while after another 24 hours of storage the refrigerated rice showed 6.9x10 5 cfu/g and frozen rice showed no load. The sensory evaluation revealed the 'cooked rice' and 'refrigerated and reheated rice' were equally acceptable and ranked as 'like very much' in terms of colour, taste, texture and overall acceptability. To ensure the maximum hygienic quality and desirable taste the cooked rice (parboiled) might be kept for a maximum period of 20 hours at room temperature and 48 hours in a refrigerator and reheated by microwave oven for 1 minute before serving to the consumer.
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J. Bangladesh Agril. Univ. 6(2): 401–408, 2008 ISSN 1810-3030
Study on the period of acceptability of cooked rice
M.A. Ali, S.M.K. Hasan1, M.N. Islam and M.N. Islam
Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh-
2202, Bangladesh and 1Department of Food Processing and Preservation, HSTU, Dinajpur
Abstract
The study attempts to determine the period of acceptability of cooked rice (parboiled) of Pajam variety.
Cooling studies on cooked rice showed the highest cooling rate in soaked water, and successively
followed by refrigeration, under fan air and at room temperature (30±20C). The moisture, protein, fat,
ash and total carbohydrate contents (wb) were 9.68, 4.93, 0.36, 0.32 and 84.71 % respectively in raw
rice; 12.37, 8.36, 0.40, 0.57 and 78.29 % respectively in parboiled rice and 65.99, 3.24, 0.15, 0.14 and
30.47 % respectively in cooked rice (parboiled). After 24 hours of storage moisture, protein, fat, ash and
carbohydrate contents were 66.47%, 5.69%, 0.13%, 0.14% and 15.73% respectively in rice at room
temperature; 69.12 %, 3.64 %, 0.13 %, 0.13 % and 26.98 % respectively in refrigerated rice and 64.38
%, 3.53 %, 0.15 %, 0.15% and 31.78 % respectively in frozen rice. The cooked rice stored at room
temperature for 24 hours showed 4.2x104cfu/g, and the refrigerated and frozen rice showed no viable
load while after another 24 hours of storage the refrigerated rice showed 6.9x105cfu/g and frozen rice
showed no load. The sensory evaluation revealed the ‘cooked rice’ and ‘refrigerated and reheated rice’
were equally acceptable and ranked as ‘like very much’ in terms of colour, taste, texture and overall
acceptability. To ensure the maximum hygienic quality and desirable taste the cooked rice (parboiled)
might be kept for a maximum period of 20 hours at room temperature and 48 hours in a refrigerator and
reheated by microwave oven for 1 minute before serving to the consumer.
Keywords: Period, Acceptability, Cooked rice
Introduction
Rice (Oryza sativa L., family Gramineae) is the most widely consumed basic foodstuff in the
world. In 39 countries rice is the staple diet, but the dependence on rice for food energy is
much higher in Asia than in other regions of the world. Rice provides 35 to 59 percent of
energy consumed by 2700 million people in Asia (FAO, 1984) and eaten as cooked rice.
Cooking is a gelatinization and hydro-thermal process involving with heat and mass transfer.
The cooked rice (parboiled) is highly perishable due to its high water activity. It is easily
affected by microorganisms which ferment the rice starch under room temperature. Cooked
rice is even more easily and dangerously affected by microbes which are responsible for food
poisoning and food infection (Frazier, 1995). Recent concern with pathogens in ready to cook
or ready to serve food is prompted by the considerable investigation relating to pre-harvest
and post-harvest food safety (Hubbert et al., 1996). Now-a-days people find less time to relax
and desire to get ready-to-eat foods. Accordingly, an attempt has been made to determine
the acceptable cooling methods for cooked rice and to determine the period of acceptability
of cooked rice (parboiled) using Pajam rice. Since there are only few references available on
cooked rice, it is decided to study the compositional changes of raw, parboiled and cooked
(parboiled) rice to observe the nutritional variations due to processing. The purpose of the
research work was to establish an acceptable procedure for instant supply of hygienic cooked
rice (parboiled) with a desirable taste.
Materials and Methods
In this study raw, parboiled and cooked rice (parboiled) were used as samples. Brief
descriptions of the methods followed for the study are given below:
402 Study on the period of acceptability of cooked rice
Cooking: 1 kg of parboiled rice was washed thoroughly with tap water and cooked over a
plate heater. Complete cooking required about 1.7 liter of water and about 25 minutes of
time.
Cooling: The cooked rice was cooled at room temperature (30±20C), under ceiling fan, in
refrigerator and in potable water (22±20C) using 3cm, 5cm and 7cm thick layers. When
soaked in water the rice was kept below 2cm from the water surface. The cooled rice was
kept at room temperature, in refrigerator and in freezer for 24 hours for further studies.
Proximate composition analysis: The moisture, crude protein, crude fat and ash contents
of the rice were determined by AOAC (1984) and following the methods as stated by
Ranganna (1991). Total carbohydrate content of the samples was determined by subtracting
method (Pearson, 1976). The starch content of the samples was determined by direct Acid
Hydrolysis method as described by Ranganna (1991).
Total viable count (TVC): The bacterial load in the cooked rice kept at room temperature
(30±2 0C) for 24 hours, and in refrigerator and freezer for 24 and 48 hours, was calculated by
the standard Plate Count Method as stated by Ranganna (1991).
Reheating the cooled rice: The cooled rice (kept in refrigerator and freezer for 24 hours)
was equilibrated to room temperature and reheated in a microwave oven (at auto scale-1) for
1 minute.
Sensory evaluation: The reheated rice was served to 13 panelists with curry (vegetable plus
small indigenous species of fish) and the sensory attributes such as colour, taste, texture and
overall acceptability were evaluated as per Hedonic Rating test (Ranganna, 1991).
Results and Discussion
Cooling the cooked rice: To observe the effect of thickness on cooling rate as influenced by
various cooling systems the cooked rice was spread at 3cm, 5cm and 7cm thick layers. At an
average Relative Humidity of 79% found cooling results has been shown in Table 1 which
shows that to reach a specific temperature required time is lower for lower thickness and
higher for higher thickness and for a specific thickness the cooling rate may be expressed as
follows:
Room temperature < Fan air < Refrigerator < Soaked in water.
This seems to be reasonable from the standpoint of temperature gradient and air flow
resistance and negligible external surface resistance (Heldman and Lund, 1992).
Table1. Cooling rate of the cooked rice at various cooling systems
Room Temperature
(30 ± 2 0C) Under fan air
(30 ± 2 0C) Soaked in water
(22 ± 2 0C) Refrigerator
Cooling
time (min) 3cm 5cm 7cm 3cm 5cm 7cm 3cm 5cm 7cm 3cm 5cm 7cm
0 98 98 98 98 98 98 98 98 98 98 98 98
10 67 68 68 63 67 70 28 30 31 51 58 63
20 48 51 53 47 50 52 27 26 27 37 46 53
30 44 48 49 39 40 46 25 26 26 29 39 43
35 40 44 47 36 37 42 25 25 26 26 32 32
40 39 40 41 33 35 38 24 25 25 23 25 25
45 38 39 40 32 33 35 24 24 24 21 22 22
50 38 38 39 32 32 33 24 24 24 19 20 20
55 38 38 38 32 32 32 24 24 24 18 19 19
Ali et al. 403
As the cooling at room temperature requires the highest time there is a possibility of microbial
contamination of the cooked rice. Again cooling in water is dependent on the volume and
temperature of the water. If larger volume of water at lower temperature is used the cooling
rate would be higher and vice versa. In case of a refrigerated storage, if a larger amount of
rice is used immediately after cooking for cooling it would be dangerous and risky due to
sudden increase of refrigeration load and the products would not be cooled as expected with
resultant loss in quality. Cooling rate under ceiling fan is higher than that of still air at constant
temperature and there is a less possibility of microbial contamination. So considering these
facts it may be concluded that to protect the cooked rice from the microbial contamination it
should be cooled immediately after cooking by spreading in a reasonable thick layer under
fan-air before being kept in a refrigerator.
Proximate composition analysis: The proximate composition analyzed for moisture,
protein, fat, ash, starch and total carbohydrate contents are presented in Table 2. It shows
that the moisture content in raw milled rice (var. Pajam) was 9.68 % (wb) which is
approximately similar to that found by McCall et al. (1951) who reported 9.0-12.0 % (wb)
moisture in raw rice. The moisture content in parboiled rice was 12.37 % (wb). This result is
higher than that found by McCance and Widdowson (1995) who reported 11.4 % (wb) and
lower than the result found by Ali et al., (1992) who obtained 13.70% (wb) moisture in
parboiled milled rice. This variation might be due to the difference in initial moisture content in
paddy and subsequent storage conditions after milling operations.
Table 2. Nutritional variation of the rice (var. Pajam) due to processing and storage
Compositional
Condition of Rice %Moisture
(Wb) %Protein
(Wb) %Fat
(Wb) %Ash
(Wb) %Starch
(Wb) %Carbohydrate
(Wb)
Raw 9.68 4.93 0.36 0.32 61.36 84.71
Parboiled 12.37 8.36 0.40 0.57 44.11 78.29
Immediately Cooked 65.99 3.24 0.15 0.14 15.78 30.47
Room temp* 66.47 5.69 0.13 0.14 9.29 27.56
Refrigerated* 69.12 3.64 0.13 0.13 13.25 26.98
Frozen * 64.38 3.53 0.15 0.15 20.95 31.78
‘Wb’ means the values are given on wet weight basis.
* indicates preserved for 24 hours.
The moisture content in the cooked rice was 65.99% which indicated that the used parboiled
rice absorbed 53-54% of moisture to be completely cooked. After 24 hours the moisture
content of cooked rice (parboiled) kept at room temperature (66.47%) and in refrigerator
(69.12%) was higher and for frozen rice (64.38%) the value is lower than that of immediately
cooked rice. Immediately after cooking the temperature of rice was much higher and
consequently some moisture was evaporated and when kept in refrigerator it absorbed
moisture to be in equilibrium with the humidity in the refrigerator, since humidity within the
refrigerator was higher than the equilibrium relative humidity of the evaporated rice. Again
while kept at room temperature the cooled rice absorbed moisture from the environment and
some alcohol was produced by fermentation of starch present in the cooked rice and due to
this reason the content might increase. According to Heldman (1977) during freezing, ice
crystals are formed in the food products and when heated to room temperature these crystals
are melted as well as evaporated and consequently moisture content of the frozen rice
decreased.
404 Study on the period of acceptability of cooked rice
The protein content of the raw milled rice (4.93%) shown in Table 2 is significantly lower than
that found by Houston and Kohler (1970) who 6.7 % (wb) protein in raw rice; and for the
parboiled rice the value (8.36 %) is within the range found by Juliano (1972), who reported
that protein content of parboiled rice to be in the range of 5.6 to 13.3 % (wb). Protein content
in the cooked rice (3.24 %) is significantly lower than that of parboiled rice which might be
due to the increase in moisture content of rice and cooking effect. The protein content of the
cooked rice (5.69 %) kept at room temperature for 24 hours is comparatively higher than that
of cooked rice which might be due to the growth of microorganisms in the rice according to
the concept of Islam et al. (2002), who stated that on an average bacterial body contains
about 15 % of protein and carbohydrate is the basic source for microbial growth. The protein
content found in the refrigerated (3.64 %) and frozen rice (3.53 %) was slightly higher than
that of cooked rice which also might be due to the growth of microorganisms because certain
psychrotrophic bacteria (e.g., Pediococcus spp., Pseudomonas sp., Flavobacterium sp.,
Achromobacter sp. and Alcaligenes sp.) are able to grow at commercial refrigeration
temperatures which are responsible for the loss of quality in nonsterile refrigerated foods
(Frazier, 1995). The laboratory experiment showed that storage of cooked rice in refrigerator
for 24 hours resulted in growth of some bacteria. Slight increase in protein content in the
refrigerated rice might be due to this reason. The increase of protein content in the frozen rice
might be due to the decrease in moisture content by formation of ice crystal and evaporation
(Heldman, 1977).
Table 2 shows that fat content of the raw rice (0.36 %) is in the range as found by Grist
(1965) who reported 0.30 to 0.40 % (wb) fat in raw milled rice and Juliano (1972) also
showed the range to be from 0.30 to 2.7 % (wb). The fat content in the parboiled rice (0.40
%) is lower than that found by Houston and Kohler (1970) and similar to that found by Juliano
(1972) and those were respectively 1.9 % (wb) and 0.4 %. The fat content of cooked rice
(0.15 %) is significantly lower than that of parboiled rice which might be due to the increase of
moisture content in the cooked rice and oxidation of fat of the rice. The fat content of cooked
rice kept in refrigerator (0.13 %) and freezer (0.15 %) for 24 hours is approximately similar to
that of cooked rice. It is thus concluded that there is negligible fat loss due to refrigeration and
freezing of cooked rice (parboiled). The fat content in the cooked rice (0.13 %) kept at room
temperature for 24 hours is lower than that of parboiled rice and cooked rice, which might be
due to the oxidation of the fat present in rice as most of the plant fats are unsaturated fats,
being easily oxidized by atmospheric oxygen.
The ash content of raw rice (0.32 %) as shown in Table 2 is similar to that (0.32 % wb) found
by Platt (1939) and Grist (1965) and less than that (0.4 % wb) found by Kik and Williams
(1945) and higher than that (0.3 % wb) found by Juliano (1972). The ash content in the
parboiled rice was 0.57 % (wb) which was higher than those obtained by McCall et al. (1951),
Watt and Merrill (1963) who reported 0.45% and 0.50 % (wb) respectively and approximately
similar to that found by Ali et al. (1992) who reported 0.60 % (wb) ash in parboiled rice. The
ash content of the cooked rice (0.14 %) is significantly lower than that of parboiled rice and
the ash content for the cooked rice (parboiled) kept at room temperature, in refrigerator and
freezer for 24 hours were 0.14 %, 0.13 % and 0.15 % (wb) respectively. Comparing these
values with the ash content of parboiled rice, it is seen that storage conditions do not affect
ash content, but cooking process itself results in reduced ash content presumably because of
leaching of ash into the cooking water which is subsequently drained out.
Ali et al. 405
Table 2 shows that starch content in the raw rice (61.36 %) is lower than that of parboiled rice
(44.11%) which proves that due to boiling the starch content in rice would significantly
decrease and the value for the parboiled rice is similar to those found by Simmonds (1980)
and Kundu (2006) who reported 44.47 % and 44.75 % (wb) starch in parboiled rice
respectively. Starch content in the cooked rice decreased drastically to 15.78% from 44.11%
(parboiled) due to moisture absorption by the rice and cooking effect. Starch content in the
cooked rice kept at room temperature, in refrigerator and freezer for 24 hours was 9.29 %,
13.25 % and 20.95 % which indicates that if the cooked rice is kept at room temperature for
maximum 24 hours, most of its starch will be lost by fermentation while the rice kept in
refrigerator gives higher starch content due to reduced fermentation; and when the rice is
kept in freezer, there is no change in starch content of the cooked rice rather it increased
probably due to moisture evaporation.
The carbohydrate content of the raw rice (84.71 %) is significantly lower than that found by
Grist (1965) who reported 91.40 % (wb) carbohydrate in raw rice, and higher than those
found by Watt and Merrill (1963) and Houston and Kohler (1970) who mentioned the value
80.40 % and 80.40 % (wb) respectively. The carbohydrate content in parboiled rice (78.29 %)
is approximately similar to those found by Gopalan et al. (1980) and Ali et al. (1992) who
reported the value 78.20 % and 78.20 % (wb) carbohydrate in parboiled rice respectively.
The content for the cooked rice (30.47 %) is significantly lower than that of parboiled rice
which might be due to uptake of water during gelatinization of starch and/or cooking process.
Comparing the carbohydrate content of cooked rice with that of the cooked rice (parboiled)
kept at room temperature (27.56 %), in refrigerator (26.98 %) and freezer (31.78 %) for 24
hours, it is observed that significant amount of carbohydrate is fermented when the cooked
rice is kept at room temperature. If the rice is kept in a refrigerator carbohydrate content is
slightly fermented and there is no fermentation when it is kept at freezing temperature (at or
below -90C).
Total Viable Count (TVC): To assess the hygienic quality total viable count was conducted
using the pre-cooled (under fan) cooked rice (parboiled) kept at room temperature, in
refrigerator (5-70C) and freezer (-90C) for 24 hours, and counted load is shown in Table 3.
Table 3. Total viable load found in the cooked rice kept under various storage
conditions
Counted bacterial load
Storage condition and duration After 24 hours
of incubation After 48 hours
of incubation After 72 hours
of incubation
Stored at RT for 24 hr 2.7 x 103 cfu/g 4.2 x 104 cfu/g 9.0 x 106 cfu/g
Refrigerated for 24 hr No colony found No colony found No colony found
Refrigerated for 48 hr No colony found 6.9 x 105 cfu/g Uncountable colony found
Frozen for 24 hr No colony found No colony found No colony found
Frozen for 48 hr No colony found No colony found No colony found
Table 3 shows that the bacterial load counted in the cooked rice kept at room temperature
(30±20C) was about 4.2x104 cfu /g by 48 hours of incubation, and no colony was found in the
rice kept in a refrigerator (5-70C) and freezer (-90C) by 72 hours of incubation. Again the
cooked rice was kept for another 24 hours in the refrigerator and freezer and examined for
the viable count and observed 6.9x105 cfu /g during 48 hours of incubation of the refrigerated
rice and no viable load was found for frozen rice. According to FAO/WHO expert consultation
of microbiological specifications (CAC/RCP 15, 1976) maximum 5x104 mesophilic aerobic
406 Study on the period of acceptability of cooked rice
bacteria are safe for human consumption and the values at or above 106 are unacceptable
(Frazier, 1995). However, from the result as shown in Table 3, it can be concluded that to
ensure maximum hygienic quality the cooked rice should be kept for a maximum period of 20
hours at room temperature and 48 hours in a refrigerator before reheating and consumption.
Sensory Evaluation of Reheated Rice (parboiled): To evaluate the sensory attributes such
as colour, taste, texture and overall acceptability only five samples of the cooked rice
(parboiled) such as S1 (cooked and cooled to room temperature), S2 (refrigerated for 20
hours and reheated), S3 (frozen for 20 hours reheated), S4 (refrigerated not reheated) and S5
(frozen not reheated) were selected and served to panelists who were asked to evaluate
them on a 1-9 point hedonic scale in which 1 is ‘dislike extremely’ while 9 is ‘like extremely’.
Hedonic Rating test was conducted on each one (Ranganna, 1991) and the mean scores
obtained by various samples for different sensory attributes are presented in Table 4.
Table 4. Mean scores obtained by various attributes of the cooked rice
Sensory attributes Types of samples Colour Taste Texture Overall acceptability
Sample-S17.92a8.46a7.54a7.92a
Sample-S27.92a8.23a7.46a7.85a
Sample-S37.78ab 6.92b6.08bc 6.85b
Sample-S47.31ab 5.23c6.77b6.85b
Sample-S56.85b5.15c4.62c4.92c
L.S.D.(P<0.05) 0.6725 0.8435 0.2627 0.7010
Means with same superscript within a column are not significantly different at P<0.05
S1 = Cooked and cooled to room temperature
S2 = Refrigerated and reheated
S3 = Frozen and reheated
S4 = Refrigerated not reheated
S5 = Frozen not reheated
Table 4 shows that sample-S1 (7.92), sample-S2 (7.92), sample-S3 (7.78) and sample-S4
(7.31) were equally acceptable and the first two samples secured the highest scores in terms
of colour preference while sample-S5 secured the lowest score (6.85). Among these the first
three samples are ranked as ‘like very much’ while sample-S4 (7.31) and sample-S5 (6.85)
can be ranked as ‘like moderately’.
Among the five samples it is found that sample-S1 received the highest taste score (8.46)
while sample-S2, sample-S3, sample-S4 and sample-S5 scored 8.23, 6.92, 5.23 and 5.15
respectively in terms of taste preference (Table 4). Thus sample-S1 and sample-S2 were
significantly different and better than other experimental samples in terms of taste preference
and can be ranked as ‘like very much’. From Table 4, it is also observed that in terms of
texture preference sample-S1 (7.54) and sample-S2 (7.46) were equally acceptable and
ranked as ‘like moderately’ while sample-S5 secured the lowest score (4.62) and was ranked
as ‘neither like nor dislike’.
In terms of overall acceptability, Table 4 shows that sample-S1 and S2 were equally
acceptable securing the highest score (7.92 and 7.85) and were the most acceptable product
among the experimental samples and ranked as ‘like very much’, and sample-S3 and sample-
S4 secured the equal score (6.85) and ranked as ‘like moderately’ while sample-S5 received
the lowest score (4.92) and ranked as ‘neither like nor dislike’ which might be due to
ice crystal formation, evaporation and consequent hardness of the cooked rice (parboiled).
Ali et al. 407
The overall results and discussion show that the colour, taste and texture of ‘cooked rice’ and
‘refrigerated and reheated rice’ were significantly better than those of other experimental
samples, i.e., refrigeration (5-70C) for 48 hours and then reheating by microwave oven for 1
minute does not adversely affect the colour, taste, texture and overall acceptability of the
cooked rice (parboiled).
Conclusion
In order to save the cooking time and supply tasteful, hygienic and nutritive cooked rice
(parboiled) instantly the parboiled rice should be cooked properly and cooled to room
temperature as quickly as possible by passing air spreading in a reasonable thick layer (5-7
cm). To protect from microbial contamination the cooled rice should be transferred
immediately into a refrigerator and kept for a maximum period of 48 hours. To ensure the
original taste of cooked rice the refrigerated rice should be reheated by microwave oven for 1
minute before serving to the consumer. The study would be advantageous for hotels,
restaurants, cafeteria or institutional (hospital) supply of cooked rice as it (1) tastes similar to
the cooked rice, (2) requires less time to re-process/reheat, (3) will save much time of today’s
busy lives and (4) can be served instantly.
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Supplementary resource (1)

... On the other hand, freshly boiled rice is having relatively short shelf life. Home made cooked rice can only considered fresh up to 20 hours since cooking [3] and still considered to be suitable for consumption up to three days in nonrefrigerated condition [4]. Boiled rice is an ideal media for microbial growth due to its moisture, sugar, vitamin and mineral contents [5]. ...
... Boiled rice is an ideal media for microbial growth due to its moisture, sugar, vitamin and mineral contents [5]. Rice can be preserved by freezing, which can maintain nutritional value and flavor for 48 hour [3]. However, this method may not be suitable for preparing food for disaster area because the frozen rice needs to be thawed and steamed before consumption. ...
... According to Ref [3], rice can be considered as fresh rice with the maximum total plate count of 5x10 4 CFU/g. Based on the microbial evaluation, the microbial content of Rice-based MRE is still significantly lower than the limit. ...
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For the first response to disaster in Indonesia, food usually is supplied in the form of instant noodle, rice and biscuits [1]. In fact, food preparation in emergency kitchen is not always possible due to lack of clean water and energy. Military issued Meals-Ready-to-Eat (MRE) is highly nutritious alternative, however the appearance and taste is not suitable for most Indonesian who intuitively choose rice as their staple food. On the other hand, cooked rice is a good media for microbial growth due to its moisture content thus is having relatively low storage time. Home made cooked rice can only considered fresh up to three days in non-refrigerated condition [4]. The need to develop Rice-based MRE that is nutritious and suitable for Indonesian eating habit is important to maintain the nutrition intake and boost the morale of people in distressed condition. This study aims to develop Rice-based MRE that has longer storage time while maintaining the nutrition and palatability compared to freshly home cooked rice. The study shows that Rice-based MRE can be prepared by simultaneous cooking and sterilization process using autoclave at 121 o C for 15 minutes. This study shows that basic formula of 75 g washed rice-grain, 100 ml water and 7.5 g cooking oil mixed in hand-sealed 2 L aluminum pouch were producing rice with consistency similar to home-made steamed rice. The product is stored in natural, uncontrolled condition for more than 21 days. Microbial growth of Rice-based MRE is visible after 14 day of storage (320 CFU/g), which is significantly under the standard of 5x10 4 CFU/g [3]. Descriptive tests were conducted and panelist can point the difference only between freshly made rice compared to the Rice-based MRE that is stored for 21 days. Addition of 1.8 g garlic powder to the basic formula shows positive effect to the microbial resistance. Microbial growth is visible only after 18 days of storage (210 CFU/g).
... Total bacterial counts at 8 hrs of storage in household condition had log 3.73 and from street food vendors it was log 5.57. A study conducted by Ali et al. (2008) has shown total bacterial counts of log 4.62 at 24 hrs of storage time at ambient temperature. There are very few studies on the shelf life, but more on foodborne pathogens of cooked rice. ...
... So refrigerated foods have a limited shelf life and must be consumed quickly. A study conducted by Ali et al. (2008) has shown no viable load after 24 hrs with refrigeration but 48 hours of refrigeration showed 6.9 × 105cfu/g. Reheating of cooked food was more effective for all the foods along with refrigeration. ...
... Total bacterial counts at 8 hrs of storage in household condition had log 3.73 and from street food vendors it was log 5.57. A study conducted by Ali et al. (2008) has shown total bacterial counts of log 4.62 at 24 hrs of storage time at ambient temperature. There are very few studies on the shelf life, but more on foodborne pathogens of cooked rice. ...
... So refrigerated foods have a limited shelf life and must be consumed quickly. A study conducted by Ali et al. (2008) has shown no viable load after 24 hrs with refrigeration but 48 hours of refrigeration showed 6.9 × 105cfu/g. Reheating of cooked food was more effective for all the foods along with refrigeration. ...
Article
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Abstract: The present study examined the differences in microbial growth of foods prepared in household and street vended conditions. Three commonly consumed foods (rice, dhal, meat) were prepared in household (HH) condition and similar food samples collected from street vendors for microbial analysis (USFDA-BAM protocol) at every 2 hrs up to 8 hrs. TBC in cooked rice appeared after 6 hrs (log 0.45 ± 0.36 cfu/g) and 2 hrs of storage (log 0.95 ± 0.94 cfu/g) from HH foods and street foods respectively. Meat samples had log 1.28 ± 1.48 cfu/g at 8 hrs and log 1.17 ± 1.35 at 4 hrs in HH and street foods respectively. Bacillus cereus and Salmonella spp. were identified in street-vended dhal samples after 4 hrs. There is a need for better understanding on shelf life of cooked foods in HH conditions and street foods.
... Due to the lake of available microbiological studies about Koshari, rice was used as reference in some discussions. A study on the cooked rice stored at refrigerator temperature (5-7ºC) for 24 hours showed no viable bacterial load, while after another 24 hours of storage, the refrigerated rice showed 6.9x10 5 cfu/g (Ali et al., 2008). According to the FAO/WHO expert consultation of microbiological specifications, a maximum of 5x10 4 cfu/g of mesophilic aerobic bacteria are safe for human consumption. ...
... The numbers of total counts in this study is much higher than those reported in the study of Ali et al. (2008) who found that the bacterial load counted in the cooked rice kept at room temperature (30±2ºC) for 24 hours was about 4.2 x 10 4 cfu/g. This may be due to the different in preparation conditions of the food since the rice prepared in their study seems to be prepared at home or in the lab, in much better conditions compared to the public restaurants. ...
... Rice is the second highest grain in the worldwide production after maize [1]. Nigeria ranked highest as both producer and consumer of rice in the sub-Saharan Africa. ...
... Rice (Oryza sativa) is an indispensable staple food for many parts (one-half) of the world especially in the east, south, southeast Asia, middle east, Latin America and West Indies. It is a good source of carbohydrate with high energy level [1,4]. Rice is however low in protein, sodium, fats and free of cholesterol which makes it useful in treating hypertension [5][6][7]. ...
Article
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This work aimed at the control of the production of protein and glucose-anabolic-enzyme (GAE) by Sac-charomyces cerevisiae during the fermentation of a Nigerian rice, Oryza sativa variety "Igbimo". The yeast was mutated with ethylmethyl sulphonate. The variants and the parental yeast were separately in-oculated into cooked rice and allowed to ferment at 27˚C for 7 days after which protein content and glu-cose-anabolic-enzyme synthesis were determined using Dinitrosalicylic acid and Biuret reagents techniques. Mutants with varying capacities to form protein and GAE were obtained. Glucose-Anabolic-Enzyme (GAE) activity ranged from 0.25 to 12.06 Units forming five groups (classes 1, 2, 3, 4 and 5) with the average ac-tivity of 0.52, 1.52, 2.28, 4.04 and 10.63 Units respec-tively compared with that (0.38 Unit) of the parent strain. All the mutants synthesized protein although many of them produced it at lower level while others at higher level than the wild-type. The highest (5.92 mg/mL) and lowest (0.10 mg/mL) levels protein pro-ducers are mutants 44 and 14 respectively. Mutants No. 4, 7, 22 and 78 formed total protein similar in concentrations (1.46, 1.46, 1.45 and 1.45 mg/mL) to that of the wild yeast (1.46 mg/mL). These three sets of protein concentration have ratios 4.1 (highest), 0.07 (lowest) and 1.0 (normal) to that of the parental yeast.
... According to the FAO/WHO expert consultation for microbiological specification (CAC/RCP 15, 1976) for egg products, maximum 10 6 mesophilic aerobic bacteria would be safe for human consumption (Frazier and Westhoff, 1995). Therefore, the JSP enriched cakes prepared in this study are microbiologically safe for human consumption (Ali et al., 2008) before 10 days of storage (25 ± 2 °C) while stored in polyethylene packages without using any externally added preservatives. ...
... One interesting point to note was that the control samples treated at 50 • C did not have high spoilage. The reason behind this is that gelatinized/ cooked rice has a higher water activity and porosity than uncooked rice, making them more susceptible to spoilage (Ali et al., 2008). The degree of gelatinization in the 50 • C control sample was negligible, restricting the availability of soluble starch that can be used by microbes for degradation. ...
Article
Rice, consumed by most people across the world, serves as a great mode for carrying nutrients. The processed, starch-rich white rice is mostly devoid of nutrients. High-pressure processing (HPP) is a technology known to produce cold gelatinizing effects in starch. This work shows the application of HPP in fortification of two types of white rice through high pressure gelatinization. The rice grains were impregnated with vitamin B1, calcium, and zinc. HPP treatment was carried out at the temperatures of 50°C and 70°C for up to 20 min. The samples were analysed for thiamine using the fluorometric method and minerals using ICP-MS. Results showed that the transfer of nutrients increases with treatment temperature and time, producing high level of nutrient uptake. HPP-fortified rice also showed stability after storage of two months. The moderate-temperature HPP has a great potential to be used as a method to produce a ready-to-eat variety of rice.
... According to the FAO/WHO expert consultation for microbiological specification (CAC/RCP 15, 1976) for egg products, maximum 10 6 mesophilic aerobic bacteria would be safe for human consumption (Frazier and Westhoff, 1995). Therefore, the JSP enriched cakes prepared in this study are microbiologically safe for human consumption (Ali et al., 2008) before 10 days of storage (25 ± 2 °C) while stored in polyethylene packages without using any externally added preservatives. ...
Article
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The study was conducted to establish a formulation for development of jackfruit seed protein (JSP) enriched cake. After extracting from jackfruit seeds, the JSP flour was added as substitutions of wheat flour at a level of 0%, 3%, 6%, 8% and 10% to prepare protein enriched cakes. The cakes were then analyzed to find out the acceptable formulation by assessing their physicochemical properties and sensory attributes. The cakes prepared with 6% JSP isolate secured the maximum sensory scores in terms of color, flavor, taste, texture, and revealed the highest overall acceptability (7.58 ± 1.01) suggesting ‘like very much’. The proximate analysis of 6% JSP enriched cake showed 15.26%, 11.59%, 25.91%, 1.06%, 2.03%, and 44.15% moisture, crude protein, crude fat, ash, crude fiber, and carbohydrate respectively. An increase in JSP level in cake formulation decreased the volume, weight, specific volume and water activity while the baking loss showed a reverse trend. The JSP enriched cake also exhibited a reduction in vitamin A content and peroxide value, and an increased calorific value. Microbiological analysis of the JSP enriched cake showed an acceptable quality by 10 days of storage (25 ± 2 °C). Therefore, maximum 6% JSP flour could be added as a substitute of wheat flour to formulate a protein enriched cake having good preferences and overall acceptability. Ann. Bangladesh Agric. (2020) 24(1) : 17-39
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The relationship between grain morphology and chemistry and the practical realities of milling, flour yield, dough properties and baking behaviour, are stressed and explained. The quality requirements of flours intended for bread-baking, noodle-making and for other industrial purposes are listed and discussed.
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As the demand for safe, nutritious, convenient foods continues to rise, and the capabilities of molecular biology and nutritional biochemistry continue to expand, the need for up-to-date engineering information becomes ever more critical. The application of innovative engineering concepts enables scientific breakthroughs to be utilized in the manufacture of the highest quality food products at the lowest possible cost. Handbook of Food Engineering, Second Edition assembles the most recent information available for the efficient design and development of processes used in the manufacturing of food products, along with traditional background and fundamental information. In keeping with the comprehensive and informative style of the original, this second edition focuses on the thermophysical properties of food and the rate constants of change in food components during processing. It highlights the use of these properties and constants in process design. Beginning with a review of the properties of food and food ingredients and the traditional unit operations associated with food manufacture, the book moves on to discuss specific points associated with freezing, concentration, dehydration, thermal processing, and extrusion. Key chapters cover basic concepts of the transport and storage of liquids and solids, as well as important topics in packaging, cleaning, and sanitation. New information on membrane processes addresses not only liquid concentration, but also other applications for membranes in food processing. The chapters on mass transfer in foods and food packaging have been extensively revised. Delineating the concepts of engineering as they are applied to the latest advancements in food manufacture, Handbook of Food Engineering, Second Edition contributes to the evolution of food engineering as an interface between engineering and other food sciences.