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Food and Nutrition Bulletin, vol. 32, no. 1 © 2011, The United Nations University. 13
Shelf stability, sensory qualities, and bioavailability
of iron-fortified Nepalese curry powder
Abstract
Background. The prevalence of iron-deficiency anemia
in Nepal is almost 50% of the whole population. Curry
powder is a promising vehicle for fortification due to its
use in various meals.
Objective. To evaluate the bioavailability of different
iron fortificants in curry powder and their effects on the
qualities of curry powder.
Methods. The serving size of curry powder was evalu-
ated in 40 Nepalese households and 10 restaurants. The
powders were fortified with iron sources of different bio-
availability. Sources with good bioavailability of iron—
ferrous sulfate (FS), ferrous fumarate (FF), and sodium
ferric ethylenediaminetetraacetic acid (NaFeEDTA)—
were added to provide one-third of the recommended
daily intake (RDI) of iron per serving. Elemental iron
(H-reduced [HRI] and electrolytic [EEI]), which has poor
bioavailability, was added to provide two-thirds of the
RDI per serving. Both fortified and unfortified products
were packed in either commercial packs or low-density
polyethylene bags and stored at 40 ± 2°C under fluores-
cent light for 3 months. The stored products were ana-
lyzed for CIE color, peroxide value, thiobarbituric acid
reactive substances, moisture, water activity, iron, and
sensory qualities. The contents of phenolic compounds
and phytate were analyzed, and iron bioavailability was
determined by the Caco-2 cell technique.
Results. The serving size of curry powder was 4 g. Iron
fortificants did not have adverse effects on the physical,
chemical, and sensory qualities of curry powder packed
in commercial packaging. After 3 months storage, HRI
significantly affected darker colors of curry powder and
the cooked dishes prepared with curry powder. The
relative bioavailabilities of NaFeEDTA and EEI were
1.05 and 1.28 times that of FS, respectively. The cost of
fortification with EEI was similar to that with FS and 4.6
times less than that with NaFeEDTA.
Conclusions. It is feasible and economical to fortify
Nepalese curry powder packed in commercial packag-
ing with EEI.
Key words: Bioavailability, curry powder, iron forti-
cation, Nepal, sensory qualities, shelf stability
Introduction
Iron deficiency is one of the most common nutritional
deficiencies in the world. According to the World
Health Organization (WHO), 60% to 80% of the
world’s population, as many as 4 to 5 billion people,
may be iron deficient, of whom 90% live in developing
countries [1]. For infants and children, iron-deficiency
anemia can lead to poor cognitive and developmen-
tal functions, lower educational achievement, poor
working and learning performances, and impaired
mental development [2]. Infant mental retardation and
maternal and perinatal mortality are the most severe
outcomes of iron-deficiency anemia in women [3].
Iron-deficiency anemia in the general population is
associated with low work productivity [4].
As in other developing countries, iron-deficiency
anemia is the most common nutritional problem
among 50% of the whole population in Nepal, where
women and children are the most susceptible groups.
Its prevalence is 42% among pregnant women and
48% among children under age 5 [5, 6]. Such numbers
present an alarming situation for the nation.
Fortification of food with iron may be an effective
long-term approach to combat iron deficiency [7,
8]. However, the success of the fortification program
depends on the bioavailability of the iron fortificant,
its effects on the taste and appearance of the fortified
Sanjeev Kumar Karn, Visith Chavasit, Ratchanee Kongkachuichai,
and Nattapol Tangsuphoom
Sanjeev Kumar Karn, Visith Chavasit, Ratchanee Kongka-
chuichai, and Nattapol Tangsuphoom are affiliated with the
Institute of Nutrition, Mahidol University, Nakhon Pathom,
Thailand; Sanjeev Kumar Karn is also affiliated with the Min-
istry of Agriculture and Cooperatives, Kathmandu, Nepal.
Please direct queries to the corresponding author: Visith
Chavasit, Institute of Nutrition, Mahidol University, Salaya,
Phutthamonthon, Nakhon Pathom 73170, Thailand; e-mail:
nuvca@mahidol.ac.th.
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14 S. K. Karn et al.
product, and its cost. In addition, the food vehicle must
be normally consumed by the target population [9].
Several iron-fortified products consumed by the people
of Southeast Asia, such as instant noodles, soy sauce,
and dried rice, have been successfully developed by our
group for various populations [10–13].
Curry powder is a potential vehicle for iron for-
tification because it is widely consumed in South
Asian countries, including Nepal, and is used in many
plant- and animal-based dishes. Curry powder is a
flavorful and aromatic blend of spices and condiments
of varying composition according to regional prefer-
ences or tradition. Generally, curry powder in South
Asia consists of coriander, turmeric, chili, mustard,
garlic, salt, fenugreek, cumin, black pepper, Bengal
gram, onion, ginger, cloves, and cinnamon. Most of
the curry powder distributed in Nepal is produced in
only two large factories, which makes it an attractive
vehicle for fortification.
Curry powder has been fortified with ethylenedi-
aminetetraacetic acid (NaFeEDTA) [14, 15], which is
known for its superior iron bioavailability in the pres-
ence of inhibitors, but it is one of the most expensive
iron fortificants, with a limited number of producers
in the world. The feasibility of using more economical
fortificants must be explored, since the cost of fortifi-
cation could play an important role in the success and
sustainability of a food fortification program in devel-
oping countries. Consequently, this study evaluated
the feasibility of fortifying Nepalese curry powder with
more economical iron fortificants, focusing mainly on
stability, acceptability, and bioavailability.
Materials and methods
Serving size evaluation
Information on the serving size of curry powder was
obtained by face-to-face interviews with local restau-
rant chefs and members of households who cook at
home with the use of open-ended questionnaires. The
household questionnaire asked the brand and type of
curry powder used, the pack size, the number of dishes
prepared per pack, the number of persons who shared
the dish, and the names of popular dishes prepared
with curry powder. The questionnaire for chefs asked
how many dishes with curry powder were served
per meal per customer and the names of the dishes.
The interviews were conducted with members of 40
households that were sampled to represent households
in Janakpur Municipality-4, Dhanusha, Nepal, and
with 10 chefs from local restaurants. Oral consent to
participate in the interview was obtained from the
participants before the interviews began.
Curry powder
Curry powder (Century Sabji Masala; Dugar Spices and
Food Products Co., Biratnagar, Nepal) was obtained
as a 50-g pack in a metalized bag (polypropylene/Al-
metalized/high-density polyethylene) covered with
a paper box (the so-called “commercial pack”). The
curry powder was kept in its original packaging in a
refrigerator at 4 ± 2°C until it was pooled and analyzed
for bioinhibitor content prior to sample preparation.
Fortificants
The five iron fortificants used in this study were anhy-
drous ferrous sulfate (FS, 33% Fe) and ferrous fumarate
(FF, 33% Fe) from Dr. Paul Lohman Company, Luneb-
urg, Germany; hydrogen-reduced elemental iron (HRI,
97% Fe) and electrolytic elemental iron (EEI, 97% Fe)
from North American Höganäs, Hollsopple, Penn-
sylvania, USA; and sodium ferric ethylenediamine-
tetraacetic acid (NaFeEDTA, 14% Fe) from Akzo Nobel
Functional Chemicals, Arnhem, the Netherlands.
Production of iron-fortified curry powder
The fortification dosage was calculated on the basis of
the results of the serving size study to provide iron at
one-third of the Thai recommended daily intake (RDI)
[16] per serving (5 mg). However, the dosages for iron
sources of low bioavailability, i.e., HRI and EEI [17, 18],
were compensated by doubling the fortification dosage
to 10 mg, or two-thirds of the Thai RDI per serving.
The iron fortificants were mixed with curry powder
with the use of a plastic spatula on a plastic tray. The
fortified curry powder was sampled in five spots to test
for iron homogeneity before being packed at 40 g in two
kinds of packaging, the commercial pack and the clear
low-density polyethylene (LDPE) bag, and heat sealed.
Shelf stability test
The packed fortified and unfortified curry powders
were stored under fluorescent light at 40 ± 2°C for 3
months. At months 0, 1, 2, and 3, the products were
sampled for physical, chemical, and sensory differ-
ence tests. For physical and chemical tests, five packs
of curry powder of the same condition were pooled
together and homogeneously mixed before the analy-
sis. At months 0 and 3, the residual iron content was
analyzed as well as the sensory acceptability of two
dishes, stir-fried potato curry and stir-fried chicken
curry, prepared with the stored fortified and unfortified
curry powders. Iron sources that resulted in fortified
products with acceptable sensory qualities were further
studied for bioavailability.
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Iron fortification of Nepalese curry powder
Physical tests
Moisture content was measured by drying the sample
in a vacuum oven at 70oC until constant weight was
achieved [19]. Water activity was analyzed on a water
activity meter (NOVASINA IC-500 Aw-Lab; Axair) at
25 ± 1°C. Color was analyzed as CIE L*a*b* on a spec-
trocolorimeter (JS-555, Color Techno System).
Chemical tests
Total iron was analyzed with an inductively coupled
plasma-optical emission spectrometer (OPTIMA 4200
DV, Perkin-Elmer) after wet digestion. The peroxide
value of methanol-chloroform extracted lipid was
measured by AOAC’s iodometric titration method with
slight modifications [19]. Thiobarbituric acid reactive
substances (TBARS) were analyzed spectrophotometri-
cally (Helios-β; Unicam) at 535 nm [20]. Bioinhibitor
(i.e., phytate) content was analyzed by the method of
Hotz and Gibson [21] with slight modification using
an HPLC with ion-pair reverse phase column and a
reflective index detector; total phenol content as gallic
acid equivalent was determined by the Folin-Ciocalteu
method with spectrophotometric measurement at 760
nm [22, 23].
Sensory evaluation
Sensory evaluation was performed at the Sensory Sci-
ence Laboratory of the Institute of Nutrition, Mahidol
University, where subjects tested samples under day-
light fluorescent lamps in individual air-conditioned
booths. The samples, which were coded with three-
digit random numbers, were randomly served to each
panelist. According to the Mahidol University Institu-
tional Review Board, ethical approval is not required
for research involving sensory evaluation of food.
The difference-from-control test [24] was performed
by 24 panelists, who were institute faculty, staff, and
graduate students, by comparing curry powders (both
fortified and unfortified) that were stored in different
packaging during the storage periods with a reference
sample (unfortified curry powder that was stored at
4oC in a commercial pack). The five-point difference-
from-control scale (1 = no difference, 3 = moderate
difference, 5 = extreme difference) was used to rate
general appearance and odor, and the bipolar 9-point
difference-from-control scale (1 = extremely lighter,
5 = no difference, 9= extremely darker) was used to rate
color. Twenty Nepalese graduate students in Thailand
performed sensory acceptability tests at months 0 and
3 on stir-fried potato and stir-fried chicken prepared
with fortified and unfortified curry powders stored in
commercial packs. The stir-fried potato was prepared
by frying boiled potato, tomato, onion, garlic, ginger,
red chili, cumin seed, coriander leaves, and salt with
the curry powder (1.5% of total recipe weight) in
soybean oil; chicken was used instead of potato for the
stir-fried chicken recipe. A five-point hedonic scale
(1 = dislike very much, 3 = neither like not dislike, 5 = like
very much) was used to rate general appearance and
overall acceptability, and a 5-point just-about-right
scale (1 = much too light/weak, 3 = just about right,
5 = much too dark/strong) was used to rate color and
odor. The panelists were also asked to rate the degree
of rancid odor using a 15-cm unstructured line scale
(1 cm = none, 14 cm = extremely strong). Between each
tasting of a sample, the subjects rinsed their mouths
with softened drinking water.
Iron bioavailability test
The bioavailability of iron in the fortified products was
determined by the tissue culture technique described
by Wortley et al. [25]. Samples were digested in vitro
with pepsin followed by pancreatin-bile extract. The
digested sample was inoculated in cultures of Caco-2
cells, a cell line developed from a human adenocarci-
noma. Cell ferritin formation was used as the biomar-
ker for iron uptake. The bioavailability of a fortificant
relative to the ferritin concentration of the FS sample
was calculated by the following equation: relative bio-
availability (%RBV) = ferritin concentration of fortifi-
cant × 100/ferritin concentration of FS.
Cost estimation
The additional cost of fortification was estimated based
on the market prices of the iron fortificants. Costs of
labor and instruments were not required, since the for-
tification process could be merged into the dry mixing
process of herbs and spices in the normal production
of curry powder. Fortification cost of a fortificant
was reported relative to the fortification cost of FS as
relative cost and relative cost based on relative bio-
availability (RBV), where the relative bioavailability of
fortificant was calculated as compared to the analyzed
bioavailability of ferrous sulfate (as 100%) by using the
following equations:
Relative cost = additional cost of fortification/addi-
tional cost of fortification due to FS
Relative cost based on RBV = relative cost × 100/RBV
Statistical analysis
Statistical analyses were performed with SPSS for Win-
dows, version 16.0. The differences between means of
the results of the sensory evaluation and bioavailability
tests were tested at a significance level of p = .05 by one-
way analysis of variance (ANOVA) and compared by
Tukey’s and Duncan’s tests, respectively.
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16 S. K. Karn et al.
Results and discussion
Fortification
The fortification levels aimed for one-third and two-
thirds of the RDI of iron per serving for sources with
good and poor bioavailability of iron, respectively [17,
18]. An effective food fortification program must be
based on appropriate serving sizes that provide the
most efficient result in the population with minimum
harm. According to our study, the average consump-
tion of curry powder per meal by Nepalese people was
approximately 4.5 g (range, 4.0 to 6.9 g). The amount con-
sumed at the 20th percentile, 4.0 g, was selected for fur-
ther study to provide adequate iron for at least 80% of
the population. This dosage level should not adversely
affect the consumers, even those at the 95th percentile
of consumption (20 mg of iron from elemental iron per
meal), since it does not exceed the no observed adverse
effect level (NOAEL) of 65 mg/day [26].
Shelf life of fortified curry powder
Since the shelf life of curry powder in its commercial
pack is 1 year, the product for the shelf-life study was
packed under a worst-case scenario condition in clear
LDPE plastic bags. The condition of elevated tempera-
ture (40°C) under fluorescent light aimed to accelerate
the deterioration rate. The homogeneity of the fortified
iron was around 10% coefficient of variation (CV).
The fortified iron as well as naturally found iron could
contribute almost 40% of the RDI per serving, whereas
elemental iron contributed up to 72% of the RDI (unre-
ported data), which was 36% based on the assumption
of 50% bioavailability. Regardless of packaging, very
low iron losses (> 90% retention) were found during
storage (unreported data). Slight changes in moisture
content and water activity could be detected during
storage (unreported data); however, they remained
lower than 0.6, which indicated no risk of microbial
growth [27]. The moisture contents of the stored prod-
ucts (5.3% to 6.4%) were below the Nepalese standard
for curry powder of 14% [28].
Color
The lightness (L*) in the colors of both fortified and
unfortified curry powder did not change much during
storage, except for the powder fortified with HRI and
stored in LDPE, which became duller (lower L*) than
the others after 3 months. During storage, all products
slightly lost their redness (a*) and yellowness (b*) at the
same rate, which was found to be high in the HRI-for-
tified samples packed in LDPE (table 1). The CIE color
values indicated that FS and HRI, in combination with
the effect of light, induced the greatest color changes
in the curry powder during storage. Changes in CIE
values were larger in curry powder packed in LDPE,
which suggests that iron-fortified curry powder should
be packaged in materials that protect it from light.
Light-induced oxidation of the phenolic compounds
in curry powder with iron as a catalyst may be the
reason for the deterioration in color. Theuer [29]
demonstrated that the degree of color change in iron-
fortified cereal porridges is related to the content of
polyphenol, which combines with iron, particularly
iron from FS, and forms dark colors. Oxidation of the
fortificant itself could be another reason for the color
change. Huma et al. [30] reported that the conversion
of Fe2+ into Fe3+ was higher in wheat flour fortified
with FS than in flour fortified with FS + EDTA or with
elemental iron. Similar results were observed in nan
made with iron-fortified whole wheat flour [31] and in
sheets of raw iron-fortified dough for instant noodles
[11]. However, differences in color values were observ-
able only in the case of HRI-fortified curry powder,
in which the color was rated as significantly too dark,
especially in the light-exposed product (table 2). Basic
impurities such as carbon, magnesium, aluminum, sili-
con, phosphorus, sulfur, chromium, manganese, nickel,
and copper, many of which are present as oxides in HRI
compounds [32, 33], may adversely affect the color of
HRI-fortified curry powder.
Peroxide value and TBARS
The peroxide value of all products increased in the
3rd month, especially for those packed in LDPE. FS
resulted in the highest peroxide value in products
packed in either type of packaging. Similar effects were
also found in the case of HRI. TBARS increased in all
products of both packaging types in the 2nd and 3rd
months, but NaFeEDTA in LDPE was the most affected
(table 3). An effect of light on lipid oxidation was also
observed in the higher peroxide value of all fortificants
packed in LDPE. However, the peroxide values were
still lower than 10 mEq/kg oil, which is the Nepalese
standard for edible oil [34]. The peroxide values of
products fortified with FS, HRI, and NaFeEDTA were
higher than those of products fortified with other for-
tificants, whereas EEI resulted in the most oxidative
stable product (table 3). Commercially, EEI might be
protected by coating with inert substances.
The differences in the TBARS, which represent an
extension of rancidity processes, were not very observ-
able among different fortificants at the same period of
the same packaging. However, the odors of most fortified
products packed in LDPE were significantly stronger than
those of commercially packaged products, especially when
measured as rancid intensity (table 2), which resulted
from the promotion of hydroperoxide formation by UV
and visible light [35]. NaFeEDTA was also reported to
produce the highest peroxide value in multiple-fortified
Ultra Rice, compared with FF, ferric pyrophosphate,
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Iron fortification of Nepalese curry powder
and SunActive iron [36].
Light-protected packaging may attenuate the lipid
oxidation rate in iron-fortified curry powder. In addi-
tion, the antioxidant properties of polyphenol in curry
powder may help to suppress oxidation, even in the
presence of an iron catalyst [37]. Inhibitory effects of
culinary herbs and spices on lipid oxidation in raw and
cooked minced-meat patties during storage have been
demonstrated [38].
Sensory quality
Table 2 shows that the general appearance of the
fortified products was not significantly different from
that of the unfortified ones (p > .05), except for the
HRI-fortified product packed in LDPE. The difference
between HRI-fortified products packed in commercial
and LDPE packages was significant. This could be
due to a color difference, since the products packed
in LDPE tended to have a darker color. Differences in
odor and rancidity between fortified and unfortified
products were not significant.
Both fortified and unfortified products that had
been kept for 3 months in commercial packs were
used for cooking two Nepalese dishes. Use of most
of the fortified products resulted in dishes that were
too dark in color, especially dishes containing meat.
Stir-fried chicken dishes prepared with 3-month-old
fortified curry powder were significantly darker in
color than those prepared with unfortified 3-month-
old powder (p ≤ .05). Only the color of the stir-fried
chicken prepared with HRI-fortified curry powder
TABLE 1. Changes in L*, a*, and b* values of iron-fortified curry powders during 3 months of storage under
accelerated conditions in different packagingsa
Packaging
Period
(mo) UF FS FF HRI EEI
NaFe
EDTA
L* valueb
Commercial
pack
0 50.50 50.81 50.61 50.56 50.54 50.26
1 51.26 50.88 50.90 50.93 50.85 51.13
2 50.34 50.70 50.51 51.21 50.82 51.38
3 49.97 49.98 50.30 50.04 50.48 50.68
LDPE 0 50.50 50.81 50.61 50.56 50.54 50.26
1 51.55 51.21 51.32 50.97 51.61 51.54
2 50.94 50.87 51.11 49.66 50.91 50.83
3 50.44 49.68 50.13 47.86 50.25 50.68
a* valuec
Commercial
pack
0 11.46 11.01 11.20 11.15 11.31 11.49
1 9.99 9.44 9.84 9.97 9.91 9.92
2 10.17 9.36 9.73 9.70 9.78 9.65
3 9.85 9.35 9.48 9.44 9.56 9.42
LDPE 0 11.46 11.01 11.20 11.15 11.31 11.49
1 10.12 9.32 9.84 9.44 9.89 9.81
2 9.82 8.88 9.59 9.11 9.77 9.78
3 9.45 8.97 8.99 8.33 9.26 9.28
b* valued
Commercial
pack
0 51.08 51.57 51.78 51.40 50.71 50.17
1 52.18 51.87 51.74 50.94 50.99 51.96
2 50.39 49.32 49.52 48.94 49.69 49.57
3 50.16 48.81 49.60 49.17 49.09 49.64
LDPE 0 51.08 51.57 51.78 51.40 50.71 50.17
1 53.53 50.43 53.05 50.47 51.79 53.11
2 49.09 48.79 48.24 47.57 48.63 48.45
3 48.31 47.70 48.90 45.52 48.44 48.13
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous sulfate; HRI, H-reduced elemental iron; LDPE, low-density
polyethylene; NaFeEDTA, sodium ferric ethylenediaminetetraacetic acid; UF, unfortified
a. The data are mean values from analysis of a mixture of 5 packs.
b. L* value represents white (100) → dark (0).
c. a* value represents red (+) → green (–).
d. b* value represents yellow (+) → blue (–).
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18 S. K. Karn et al.
had a significantly lower score for general appearance
(table 4). Dishes prepared with fortified and unforti-
fied curry powder did not differ significantly in odor
or rancidity ( p > .05). Meat contains heme iron, which
can be oxidized to the ferric form, resulting in a darker
color [39]. Furthermore, sulfur-containing amino acids
in animal protein can react with iron and darken the
food. In products fortified with HRI, the HRI became
rusty in color, which could be another cause of the
product’s becoming darker in color [40].
TABLE 2. Sensory scores for general appearance, color, odor and rancid odor intensity of iron-fortified curry powders as
compared with reference sample (refrigerated unfortified curry powder) during 3 months of storage under accelerated condi-
tion in different packagings1
Packaging
Period
(mo) UF FS FF HRI EEI NaFeEDTA
General appearance2
Commercial
pack
0 1.38 ± 0.77 1.50 ± 0.83 1.62 ± 1.06 1.50 ± 0.78 1.50 ± 0.93 1.50 ± 0.83
1 1.42 ± 0.72 1.67 ± 0.82 1.79 ± 0.93 1.50 ± 0.83 1.54 ± 0.98 1.58 ± 0.97
2 1.75 ± 0.90 1.92 ± 0.65 1.96 ± 0.91 1.88 ± 0.95 1.79 ± 0.66 1.92 ± 0.83
3 2.00 ± 1.02 2.08 ± 1.14 1.79 ± 1.02a1.62 ± 0.77*1.67 ± 0.80 1.83 ± 0.76
LDPE 0 1.38 ± 0.77 1.50 ± 0.83 1.62 ± 1.06 1.50 ± 0.78 1.50 ± 0.93 1.50 ± 0.83
1 1.50 ± 0.66 2.00 ± 1.10 1.67 ± 1.09 1.71 ± 0.91 1.54 ± 0.78 1.46 ± 0.83
2 1.50 ± 0.66a2.00 ± 0.98ab 2.00 ± 1.06ab 2.17 ± 0.87b1.67 ± 0.70ab 1.88 ± 1.04ab
3 1.71 ± 0.62a1.92 ± 0.78a1.79 ± 0.93a2.79 ± 1.14b* 1.83 ± 0.70a1.62 ± 0.57a
Color3
Commercial
pack
0 5.29 ± 1.08 5.54 ± 1.06 5.29 ± 0.55 5.12 ± 0.54 5.58 ± 0.97 5.21 ± 0.59
1 5.04 ± 0.81 5.04 ± 1.20 5.21 ± 1.10 5.04 ± 1.04 5.04 ± 1.16 4.96 ± 0.91
2 5.33 ± 1.27 5.29 ± 1.20 5.54 ± 0.98 5.08 ± 0.65*5.21 ± 1.02 5.12 ± 1.15
3 5.46 ± 1.22 5.62 ± 1.31 5.62 ± 1.10 5.75 ± 1.33*5.42 ± 1.02 5.21 ± 1.25
LDPE 0 5.29 ± 1.08 5.54 ± 1.06 5.29 ± 0.55 5.12 ± 0.54 5.58 ± 0.97 5.21 ± 0.59
1 4.88 ± 0.99 5.04 ± 1.04 5.08 ± 0.88 5.25 ± 1.03 4.96 ± 1.16 5.12 ± 1.04
2 5.29 ± 1.23 5.62 ± 1.41 5.58 ± 1.10 5.96 ± 1.30*5.75 ± 1.07 5.33 ± 0.96
3 5.75 ± 1.36a6.00 ± 1.44ab 5.50 ± 1.35a6.71 ± 1.40b* 5.50 ± 1.47a5.83 ± 1.17a
Odor2
Commercial
pack
0 1.83 ± 0.96 2.21 ± 1.10 1.58 ± 0.83 2.04 ± 1.16 2.21 ± 1.28 2.08 ± 1.25
1 1.92 ± 1.38 1.96 ± 1.22*1.71 ± 0.86 2.04 ± 0.96 1.71 ± 1.00 1.71 ± 0.62*
2 1.79 ± 0.98 1.75 ± 1.03 2.17 ± 1.09 2.08 ± 1.10 1.83 ± 1.05 1.71 ± 0.91*
3 1.67 ± 1.01 1.88 ± 1.12 1.54 ± 0.83*1.71 ± 1.08*1.71 ± 1.08*1.79 ± 1.02
LDPE 0 1.83 ± 0.96 2.26 ± 1.10 1.58 ± 0.83 2.04 ± 1.16 2.21 ± 1.28 2.08 ± 1.25
1 1.96 ± 0.91a2.71 ± 1.12b* 2.04 ± 0.96ab 2.38 ± 1.24ab 2.38 ± 1.24ab 2.38 ± 1.24ab*
2 2.21 ± 1.02 2.21 ± 1.14 2.42 ± 1.25 2.58 ± 1.21 2.08 ± 1.21 2.25 ± 0.85*
3 2.08 ± 1.10 2.42 ± 1.06 2.42 ± 1.40*2.62 ± 1.06*2.38 ± 1.17*1.92 ± 1.10
Rancid odor intensity4
Commercial
pack
0 1.24 ± 0.73 1.69 ± 1.62 1.09 ± 0.45 1.36 ± 1.34 1.58 ± 1.60 1.09 ± 0.45
1 1.00 ± 0.00 1.58 ± 1.86*1.08 ± 0.39 1.17 ± 0.82 1.03 ± 0.16 1.06 ± 0.31
2 1.00 ± 0.00 1.26 ± 1.26 1.05 ± 0.26 1.00 ± 0.00 1.07 ± 0.36 1.00 ± 0.00
3 1.36 ± 1.21*1.35 ± 1.45*1.33 ± 1.78*1.56 ± 1.88*1.07 ± 0.33*1.13 ± 0.46*
LDPE 0 1.24 ± 0.73 1.69 ± 1.62 1.09 ± 0.45 1.36 ± 1.34 1.58 ± 1.60 1.09 ± 0.45
1 1.10 ± 0.36 1.13 ± 0.35*1.33 ± 1.16 2.07 ± 2.10 1.43 ± 1.30 1.31 ± 1.07
2 1.41 ± 1.20 1.66 ± 2.01 1.36 ± 1.32 1.20 ± 0.58 1.14 ± 0.43 1.18 ± 0.52
3 2.85 ± 3.05*2.75 ± 3.06*3.28 ± 3.47*2.85 ± 2.84*2.63 ± 2.96*2.87 ± 3.28*
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous sulfate; HRI, H-reduced elemental iron; LDPE, low-density polyethylene;
NaFeEDTA, sodium ferric ethylenediaminetetraacetic acid; UF, unfortified
1. The data are means ± SD from 24 panelists. Means with different superscripts within the same row are significantly different (p ≤ .05).
Means with asterisks within the same column at the same period of time for products with different packagings and the same sensory
quality are significantly different (p ≤ .05).
2. Difference from control: 1 = no difference, 3 = moderate difference, 5 = extreme difference.
3. Difference from control (bipolar scale): 1 = extremely lighter, 5 = no difference, 9 = extremely darker.
4. Rancid odor intensity (15-cm line scale): 1 cm = none, 14 cm = extremely strong).
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19
Iron fortification of Nepalese curry powder
TABLE 3. Peroxide value and thiobarbituric acid reactive substances of iron-fortified curry powders during 3 months of
storage under accelerated conditions in different packagingsa
Packaging
Period
(mo)
PV (mEq/kg oil) TBARS (mg MDA/kg oil)
UF FS FF HRI EEI
NaFe
EDTA UF FS FF HRI EEI
NaFe
EDTA
Commer-
cial pack
0 1.48 1.23 1.68 1.21 1.51 1.42 3.17 2.80 3.17 2.93 2.58 3.33
1 1.53 2.08 1.84 1.75 1.85 1.61 3.11 2.96 3.33 3.10 2.75 3.31
2 1.61 2.01 1.90 1.91 1.89 1.94 4.29 4.91 4.37 4.19 4.19 4.47
3 1.57 2.33 1.98 1.98 1.84 1.60 5.65 5.21 5.35 5.35 5.20 5.67
LDPE 0 1.48 1.23 1.68 1.21 1.51 1.42 3.17 2.80 3.17 2.93 2.58 3.33
1 2.36 3.05 3.94 2.82 1.98 2.10 3.50 3.04 3.27 3.31 2.95 3.63
2 2.68 3.14 3.82 4.07 2.49 3.21 5.73 5.63 5.44 5.51 5.87 5.64
3 4.39 5.28 5.89 6.55 3.79 5.99 5.88 5.49 5.53 5.71 6.02 6.49
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous sulfate; HRI, H-reduced elemental iron; LDPE, low-
density polyethylene; MDA, , malondialdehyde; NaFeEDTA, sodium ferric ethylenediaminetetraacetic acid; PV, perox-
ide value; TBARS, thiobarbituric acid reactive substances; UF, unfortied
a. e data are mean values from analysis of a mixture of 5 packs.
TABLE 4. Sensory score for acceptability of stir-fried potato and stir-fried chicken prepared with iron-fortified curry powder
that had been stored under accelerated conditions in commercial packaging1
Stir-fried
product
Period
(mo) UF FS FF HRI EEI NaFeEDTA
General appearance2
Potato 0 3.67 ± 0.80 3.57 ± 0.81 3.57 ± 0.75 3.81 ± 0.75 3.95 ± 0.80 3.76 ± 0.89
3 3.95 ± 0.76 3.65 ± 0.99 3.65 ± 0.88 3.85 ± 0.93 3.70 ± 0.98 3.35 ± 0.81
Chicken 0 4.10 ± 0.64b3.75 ± 0.97b3.85 ± 0.88b3.20 ± 0.89a3.95 ± 0.94b3.85 ± 0.49b
3 3.90 ± 0.64b3.60 ± 0.88ab 3.60 ± 0.68ab 3.30 ± 0.98a3.80 ± 0.70ab 3.55 ± 0.94ab
Overall acceptability2
Potato 0 3.95 ± 0.67 3.67 ± 0.66 3.76 ± 0.83 3.67 ± 0.80 3.81 ± 0.87 3.71 ± 0.78
3 3.55 ± 0.94 3.75 ± 0.79 3.60 ± 0.94 3.75 ± 1.02 3.70 ± 1.08 3.45 ± 0.83
Chicken 0 3.95 ± 0.69 3.90 ± 0.79 3.65 ± 0.99 3.90 ± 0.64 3.75 ± 0.91 3.75 ± 0.91
3 3.75 ± 0.79 3.40 ± 0.75 3.70 ± 0.73 3.50 ± 0.76 3.80 ± 0.77 3.60 ± 0.75
Color3
Potato 0 3.00 ± 0.45 3.14 ± 0.73 3.05 ± 0.67 3.10 ± 0.62 2.86 ± 0.57 3.05 ± 0.50
3 2.80 ± 0.41a3.00 ± 0.65ab 3.05 ± 0.51ab 3.25 ± 0.72b3.05 ± 0.69ab 3.10 ± 0.72ab
Chicken 0 3.00 ± 0.32a3.10 ± 0.55a3.20 ± 0.70a3.60 ± 0.50b2.90 ± 0.55a3.15 ± 0.37a
3 2.50 ± 0.69a3.30 ± 0.47cb 3.40 ± 0.88cb 3.70 ± 0.57c3.20 ± 0.62b3.10 ± 0.64b
Odor4
Potato 0 3.10 ± 0.54 3.19 ± 0.60 3.10 ± 0.70 3.10 ± 0.62 3.05 ± 0.59 2.95 ± 0.59
3 3.10 ± 0.55 3.00 ± 0.65 3.00 ± 0.46 3.00 ± 0.65 3.25 ± 0.72 2.90 ± 0.45
Chicken 0 3.10 ± 0.31 3.00 ± 0.56 3.10 ± 0.45 3.30 ± 0.73 2.95 ± 0.51 3.05 ± 0.60
3 3.00 ± 0.32 3.10 ± 0.55 3.35 ± 0.67 3.15 ± 0.49 3.05 ± 0.51 3.15 ± 0.81
Rancid odor intensity5
Potato 0 1.20 ± 0.66 1.50 ± 1.43 1.50 ± 1.51 1.10 ± 0.15 1.40 ± 1.41 1.00 ± 0.00
3 1.70 ± 2.58 1.20 ± 0.51 1.10 ± 0.36 1.41 ± 1.41 1.30 ± 1.18 1.20 ± 0.72
Chicken 0 1.20 ± 0.89 1.00 ± 0.00 1.00 ± 0.00 1.00 ± 0.00 1.00 ± 0.00 1.00 ± 0.00
3 2.00 ± 2.52 2.00 ± 2.66 1.70 ± 2.27 2.00 ± 2.47 1.90 ± 2.16 1.70 ± 1.81
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous sulfate; HRI, H-reduced elemental iron; NaFeEDTA, sodium ferric ethyl-
enediaminetetraacetic acid; UF, unfortified
1. The data are means ± SD from 20 panelists. Means with different superscripts within the same row are significantly different (p ≤ .05).
2. General appearance and overall acceptability scores: 1 = dislike very much, 3 = neither like nor dislike, 5 = like very much.
3. Color score (just-about-right scale): 1 = much too light, 3 = just about right, 5 = much too dark.
4. Odor score (just-about-right scale): 1 = much too weak, 3 = just about right, 5 = much too strong.
5. Rancidity intensity score: 15-cm line scale (1 cm = none, 14 cm = extremely strong).
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20 S. K. Karn et al.
Iron bioavailability
The total phytate and polyphenol contents of the
curry powder were 27.03 mg per serving (675.76
mg/100 g) and 13.45 mg per serving (336.4 mg/100 g),
respectively. The phytate content is less than that in
most cereal and cereal-based food products [41]. The
polyphenol content is less than that in beans, tea, and
most fruits but higher than that in cereals and berry
fruits [42]. However, the total phytate and polyphenol
contents in foods prepared with the curry powder
could be higher, since curry powder is normally used
in the preparation of plant-based foods.
On the basis of the Caco-2 cell model study, the
iron in EEI-fortified curry powder was the most bio-
available, and the iron in NaFeEDTA- and FS-fortified
powders had similar bioavailability (fig. 1 and table 5).
Ferritin formation in unfortified curry powder was
identical to that of cells at baseline, indicating negligi-
ble iron bioavailability (fig. 1). Since the fortification
dosage of iron from EEI was twice that of iron from
FS, FF, and NaFeEDTA, this finding, therefore, might
not be directly comparable with those of previous
studies which found that more iron from NaFeEDTA
than from other fortificants can be available in food
containing high content of bioinhibitors [43–45].
After adjustment for iron content, the amount of iron
available from EEI might be only 64% of that available
from FS. In addition, the amount of bioinhibitors in
the curry powder might not be high enough to have
a significant inhibitory effect on ferritin formation or
iron uptake by cells and significantly enhance the effect
of NaFeEDTA. A human study conducted by Hurrell et
al. [46] reported that the absorption of iron from infant
cereal and bread, which have a high phytate content,
was higher when they were fortified with NaFeEDTA
than when they were fortified with FS. However, when
fish sauce and soy sauce fortified with NaFeEDTA or FS
were added to food of low phytate content, no signifi-
cant difference in iron absorption was found between
dishes containing NaFeEDTA-fortified flavorings and
those with FS-fortified flavorings [47]. Mendoza et
al. [48] also found no difference on iron absorption
as NaFeEDTA and FS were fortified in low-phytate
maize porridge.
Fortification cost
Based on the cost of iron fortificants, the additional
cost of fortification ranged from US¢ 0.90 to 7.15 (0.68
to 5.37 NRs) per kilogram of curry powder (table 6).
HRI had the lowest cost and NaFeEDTA the highest.
When RBV is taken into account, the costs of fortification
with EEI and FS are similar (table 6). According to the
retail price of curry powder per pack (18 NRs in 2009),
the percentage cost increment due to fortification was
0.19% to 1.49% (table 6), which is similar to that of most
ongoing food fortification programs [49].
Conclusions
Fortification of Nepalese curry powder with iron using
the fortificants FS, FF, EEI, and NaFeEDTA does not
cause adverse changes in physical, chemical, or sensory
qualities. Iron from the EEI fortificant at a double
dosage had the highest bioavailability in the Caco-2
cell study. When RBV is taken into account, EEI and
FS are the most economical fortificants. Commercial
iron-fortified curry powder should be packaged in
metalized plastic bags inside paper boxes.
FIG. 1. Intracellular ferritin concentration in Caco-2 cells
incubated with unfortified curry powder and curry powder
fortified with ferrous sulfate (FS), ferrous fumarate (FF), elec-
trolytic elemental iron (EEI), and sodium ferric ethylenedi-
aminetetraacetic acid (NaFeEDTA). Filled columns represent
mean of six analyses and error bars represent standard error
of the mean. Bars with different letters represent significantly
different means (p ≤ .05)
0
20
40
60
80
100
a
a
ng ferritin / mg cell protein
Cell
baseline
Unfortified FS FF EEI NaFeEDTA
b
b
c
b
TABLE 5. Relative bioavailability and relative cost of fortifica-
tion of curry powder as compared with ferrous sulfate
Fortificant1RBV (%)1Relative cost2
Relative cost
based on
RBV3
FS 100.00a1.00 1.00
FF 78.20a1.90 2.40
EEI 128.10b1.22 1.00
NaFeEDTA 104.60a4.84 4.60
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous
sulfate; NaFeEDTA, sodium ferric ethylenediaminetetraacetic acid;
RBV, relative bioavailability
1. RBV = ferritin concentration of a fortificant × 100/ferritin concen-
tration of FS. Values with different superscripts are significantly
different (p ≤ .05).
2. Relative cost = additional cost of fortification/additional cost of
fortification due to FS.
3. Relative cost based on RBV = relative cost × 100/RBV.
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21
Iron fortification of Nepalese curry powder
TABLE 6. Additional cost of curry powder due to fortification with irona
Fortificant1
Fortificant
added (g/kg)
Cost of forti-
ficant
(US$/kg)
Additional cost of curry powder
Cost incre-
ment (%)b
US¢/kg
US¢/50-g
pack NRs/kg
NRs/50-g
pack
FS 3.7896 3.9 1.48 0.07 1.11 0.06 0.31
FF 3.7880 7.4 2.80 0.14 2.11 0.11 0.58
HRI 2.5808 3.5 0.90 0.05 0.68 0.03 0.19
EEI 2.5818 7.0 1.81 0.09 1.36 0.07 0.38
NaFeEDTA 8.9362 8.0 7.15 0.36 5.37 0.27 1.49
EEI, electrolytic elemental iron; FF, ferrous fumarate; FS, ferrous sulfate; HRI, H-reduced elemental iron; NaFeEDTA, sodium ferric ethyl-
enediaminetetraacetic acid
a. Exchange rate 24 October 2009: US$1 = 75.12 NRs.
b. Based on the product cost at 18 NR per package (50 g)
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