Determination of selenium concentration in rice and the effect of foliar application of Se-enriched fertiliser or sodium selenite on the selenium content of rice


Hu, Q.; Chen, L.; Xu, J.; Zhang, Y.; Pan, G.

Journal of the Science of Food and Agriculture 82(8): 869-872

2002


Atomic fluorescence spectrophotometry was used to determine the selenium (Se) concentration in 30 rice products of different species from Southern China. The Se level ranged from 0.015 to 0.046 mug g-1. Considering the average daily individual consumption of rice products in Southern China, the average dietary intake of Se supplied by this source is only 6-18 mug day-1 for an adult. This low Se intake from rice products is mainly responsible for the low total Se intake of inhabitants in Southern China. Foliar spraying of Se-enriched fertiliser or sodium selenite with 14-18 g Se ha-1 in the heading stage of rice growth increased the Se content to 0.178-0.421 mug g-1 in rice products. The concentration and amount of Se-enriched fertiliser can be varied to achieve an optimum concentration of Se in rice products. The authors suggest that these Se-enriched rice products can contribute an increase in Se intake of 50-100 mug day-1 on average if their Se concentration is controlled in the region of 0.15-0.50 mug g-1.

Journal
of
the
Science
of
Food
and
Agriculture
J
Sci
Food
Agric
82:869-872
(online:
2002)
DOI:
10.1002/jsfa.1115
Determination
of
selenium
concentration
in
rice
and
the
effect
of
foliar
application
of
Se
-enriched
fertiliser
or
sodium
selenite
on
the
selenium
content
of
rice
Qiuhui
Hu,'*
Licheng
Chen,'
Juan
Xu,
2
Yanling
Zhang
3
and
Genxing
Pan
3
iColle
g
e
of
Food
Science
and
Technology,
Nanjing
Agricultural
University,
Nanjing
210095,
China
2
Department
of
Biochemistry,
Changshu
College
of
Jangsu
Provice,
Changshu
215500,
China
3
College
of
Resource
and
Environment
Science,
Nanjing
Agricultural
University,
Nanjing
210095,
China
Abstract:
Atomic
fl
uorescence
spectrophotometry
was
used
to
determine
the
selenium
(Se)
concen-
tration
in
30
rice
products
of
different
species
from
Southern
China.
The
Se
level
ranged
from
0.015
to
0.046
jig
g
-1
.
Considering
the
average
daily
individual
consumption
of
rice
products
in
Southern
China,
the
average
dietary
intake
of
Se
supplied
by
this
source
is
only
6-18
µg
day
-1
for
an
adult.
This
low
Se
intake
from
rice
products
is
mainly
responsible
for
the
low
total
Se
intake
of
inhabitants
in
Southern
China.
Foliar
spraying
of
Se
-enriched
fertiliser
or
sodium
selenite
with
14-18g
Se
ha
-1
in
the
heading
stage
of
rice
growth
increased
the
Se
content
to
0.178-0.421
jig
g
-1
in
rice
products.
The
concentration
and
amount
of
Se
-enriched
fertiliser
can
be
varied
to
achieve
an
optimum
concentration
of
Se
in
rice
products.
The
authors
suggest
that
these
Se
-enriched
rice
products
can
contribute
an
increase
in
Se
intake
of
50-100
jig
day
-1
on
average
if
their
Se
concentration
is
controlled
in
the
region
of
0.15-0.50
utg
g
-1
.
(D
2002
Society
of
Chemical
Industry
Keywords:
selenium;
rice;
Se
-enriched
fertiliser;
production
of
Se
-enriched
rice
INTRODUCTION
Selenium
(Se)
is
essential
for
both
humans
and
livestock.
Se
-deficient
soils
and
crops
are
found
in
many
regions
of
the
world.
These
soils
and
crops
contain
less
than
0.6
and
0.1
µg
Se
g
-1
respectively.'
The
Se
supply
in
almost
all
European
countries,
including
Austria
and
Germany,
is
below
the
recom-
mended
daily
intake.
2
Se
deficiency
can
seriously
affect
both
human
and
animal
health.
3
Se
deficiency
causes
Keshan
and
Kashin-Beck
diseases
in
China.
4
Recently,
Se
was
found
to
be
a
cancer
-protective
agent.
5
Therefore
Se
should
be
provided
to
humans
and
animals
as
part
of
their
normal
nutritional
intake.
Although
food
is
the
main
source
of
Se
for
humans,
the
Se
content
in
a
food
product
depends
on
the
Se
level
in
the
soil
where
the
agricultural
crop
was
grown.
In
soils
of
low
pH
with
high
contents
of
Fe
and
Al
oxides,
such
as
those
in
Southern
China,
selenite
and
selenate
form
insoluble
complexes
with
Fe
and
Al
oxides
and
become
unavailable
for
plant
uptake.
About
70%
of
soils
in
China
are
Se-deficient.
6
People
in
low
-Se
areas,
living
on
Se
-poor
food,
have
a
low
Se
intake.
The
total
human
Se
intake
was
reported
by
the
Chinese
Nutrition
Association
to
be
only
26
µg
day
-1
,
and
in
some
regions
below
10
µg
day
-
1.2,7
In
these
areas
an
endemic,
often
fatal
cardiomyopathy
affects
the
population.
Epidemiological
evidence
has
sug-
gested
that
low
Se
intake
may
increase
the
risk
of
cardiovascular
disease
and
cancer.
8-1°
The
US
Food
and
Drug
Administration
(FDA)
has
approved
sodium
selenite
and
sodium
selenate
for
supplemen-
tation
at
0.3
µg
Se
g
-1
in
animal
feeds."
However,
retention
of
organically
bound
Se
is
higher
than
that
of
inorganic
Se.
12
Grains
are
the
major
source
of
organically
bound
Se,
largely
as
selenomethionine.
13
The
recommended
average
dietary
Se
intake
is
50-200
µg
day.
2,14
Because
of
the
low
Se
intake
of
the
population
in
Se
-deficient
areas
and
the
possible
harmful
health
effects,
special
attention
has
been
given
to
enhancing
the
Se
content
of
plants.
15-18
Plants
take
up
supplemented
Se
applied
to
the
soil
or
sprayed
directly
on
the
leaves
and
metabolise
it
into
organically
bound
Se.
Plant
-based
Se
has
been
accepted
as
safe
and
effective
for
human
Se
intake.
19
In
our
previous
study
we
demonstrated
that
Se
-enriched
tea
leaves
were
a
safe
and
effective
Se
resource
to
enhance
*
Correspondence
to:
Qiuhui
Hu,
College
of
Food
Science
and
Technology,
Nanjing
Agricultural
University,
Nanjing
210095,
China
E-mail:
qiuhui@hotmail.com
Contract/grant
sponsor:
National
Key
Basic
Research
Support
Foundation;
contract/grant
number:
G1999011808-3
(Received
9
July
2001;
revised
version
received
26
November
2001;
accepted
6
February
2002)
©
2002
Society
of
Chemical
Industry.
J
Sci
Food
Agric
0022-5142/2002/$30.00
869
Q
Hu
et
al
human
Se
intake.
20
China
has
one
of
the
highest
rice
product
consumptions
in
the
world
and
rice
is
the
major
foodstuff.
However,
the
Se
content
of
rice
products
is
low
and
the
mainly
rice
-based
diet
con-
tributes
an
inadequate
amount
of
Se
for
Chinese
inhabitants.
The
objectives
of
this
study
were
to
determine
the
Se
content
in
rice
products
of
different
species
cultured
mainly
in
Southern
China,
and
the
influence
of
foliar
application
of
Se
-enriched
fertiliser
or
sodium
selenite
on
increasing
the
Se
content
of
rice
products
to
enhance
human
Se
intake.
MATERIALS
AND
METHODS
Preparation
of
Se
-enriched
fertiliser
Lobster
waste
(20%),
chicken
excreta
(30%),
silk-
worm
excreta
(15%),
pig
excreta
(34%)
and
EM
(effective
micro-organism)
bacteria
(1%)
were
mixed
and
allowed
to
ferment
for
about
2
weeks
in
a
methane
-generating
pit.
Se,
as
sodium
selenite,
and
water
were
added
to
the
mixed
fertiliser
and
well
distributed,
then
fermentation
was
allowed
to
con-
tinue
for
4
weeks.
The
fermented
solution
was
fi
ltered
and
concentrated
in
vacuo
below
50
°C.
The
fi
nal
solution
contained
50g
Se
1
-1
.
The
Se
-enriched
ferti-
liser
was
bottled
in
plastic
containers
in
volumes
of
100
ml.
Collection
of
rice
seeds
of
different
species
cultured
in
Southern
China
Rice
seeds
of
30
of
the
most
common
species
cultured
in
Southern
China
were
obtained
from
the
Agricul-
tural
Experiment
Station
of
Suzhou,
Jiangsu
Province.
Preparation
of
Se
-enriched
rice
The
experiment
was
conducted
in
three
Se
-deficient
regions,
Ganyu
County,
Rugao
County
and
Yancheng
County,
Jiangsu
Province.
Experiment
in
Ganyu
County
The
experiment
was
conducted
at
the
Popularized
Station
of
Agricultural
Technology
in
Ganyu
County,
Jangsu
Province.
The
trial
was
carried
out
on
20
m
2
plots
in
triplicate
for
each
treatment.
The
total
Se
content
of
the
top
0-300mm
of
soil
was
0.51
µg
g
-1
.
The
pH
of
the
soil
was
7.18
in
1:5
soil/water.
The
rate
of
treatment
with
Se
-enriched
fertiliser
or
sodium
selenite
was
18
g
Se
ha
-1
at
a
concentration
of
50
mg
Se
1
-1
.
The
rice
species
used
in
the
experiment
was
Jiuyou-18,
the
most
widespread
cultured
species
in
Southern China.
The
Se
-enriched
fertiliser
and
sodium
selenite
were
evenly
sprayed
on
the
rice
leaves
on
20
August
2000
in
the
heading
stage
of
rice
growth.
The
rice
seeds
were
harvested
on
10
November
2000.
Experiment
in
Rugao
County
and
Yancheng
County:
The
experimental
fi
eld
areas
were
100
and
150
ha
in
Rugao
County
and
Yancheng
County
respectively.
The
total
Se
content
of
the
top
0-300mm
of
soil
was
0.110
µg
g
-1
in
Rugao
County
and
0.034
µg
g
-1
in
Yancheng
County.
The
Se
-enriched
fertiliser
was
dissolved
in
water
at
a
concentration
of
50
mg
Se
1
-1
and
applied
at
14
and
18g
Seha
-1
in
Rugao
County
and
Yancheng
County
respectively.
The
rice
species
used
in
the
experiment
in
Rugao
County
and
Yancheng
County
were
9915
and
Wuyujing
No
3
respectively.
The
Se
-enriched
fertiliser
was
evenly
sprayed
on
the
rice
leaves
on
28
August
2000
in
Rugao
County
and
18
August
2000
in
Yancheng
County
in
the
heading
stage
of
rice
growth.
The
rice
was
harvested
on
3
November
in
Rugao
County
and
15
October
in
Yancheng
County.
Nine
and
14
random
samples
of
rice
seed
were
collected
in
the
respective
fi
elds
as
Se
analysis
samples.
Processing
of
rice
products
The
harvested
rice
seeds
were
dried
at
room
tem-
perature.
The
husks
were
removed
and
the
seeds
were
processed
to
polished
rice
products.
Analysis
methods
Apparatus
An
atomic
fluorescence
spectrophotometer
(AF
-
6310A,
Beijing
Rayleigh
Analytical
Instrument
Cor-
poration,
Beijing,
China)
was
used
with
a
100mA
hollow
cathode
lamp.
Reagents
HNO
3
,
HC1
and
HC10
4
of
reagent
grade
and
KOH,
KBH
4
and
K
3
Fe
(CN)
3
of
analytical
reagent
grade
were
used.
Procedure
The
rice
product
samples
were
dried
at
60
°C
and
pulverised.
Two
1
g
samples
were
taken
from
each
rice
sample
for
analysis.
The
fi
ne
powder
samples
were
digested
with
10m1
of
a
4:1
mixture
of
HNO
3
and
HC10
4
at
120°C
in
a
sand
bath
for
45
min.
After
cooling,
5
ml
of
6
mol
1
-1
HC1
was
added
to
the
digest
to
reduce
Se
6-
'
to
Se
4
t
This
process
took
15
min
until
the
sample
was
completely
reduced.
When
cooled,
the
digest
was
diluted
with
deionised
water
to
50
ml.
Then
10
ml
of
the
digest
solution
was
transferred
to
a
reaction
vessel
and
2m1
of
6mo1
1
-1
HC1
and
1
mL
of
10%
(w/w)
K
3
Fe(CN)
3
were
added.
The
control
in
the
same
procedure
was
used
to
provide
a
blank
value.
Atomic
fluorescence
spectrophotometry
was
used
for
determination
of
Se
in
solution
The
detection
limit
for
Se
analysed
by
this
method
was
0.0005
µg
ml
-1
.
Reproducibility
and
accuracy
The
reproducibility
and
accuracy
of
the
Se
measure-
ments
were
determined
by
using
the
procedure
described
above
to
analyse
a
standard
reference
Se
material
(GBW
07603-GSV-2)
manufactured
by
the
National
Institute
of
Minerals
of
China.
The
certified
value
of
the
reference
material
was
0.120
±
0.020
and
the
present
study
determined
a
value
of
0.116
±
0.026
by
the
above
method.
870
y
Sci
Food
Agric
82:869-872
(online:
2002)
Selenium
concentration
in
rice
and
production
of
Se
-enriched
rice
Table
1.
Mean
Se
content
(.1g
g
-1
)
in
rice
products
of
different
species
from
Southern
China
Rice
species
Se
content
Taihu
Suo
8006
a
0.041
9920
a
0.042
96-32
a
0.015
Chang
You
99-1
a
0.030
Zheng
Dao
5171
a
0.023
Zheng
Dao
5394
a
0.043
Qinyou
Xiangqing
a
0.026
99-15
a
0.031
C
97-441
a
0.034
C
-00-8
a
0.034
You
Feng
a
0.040
Jia99-21
a
0.038
Wu
Yu
5201
a
0.038
HBD
77
a
0.023
HDD
30a
0.033
HDD
64
a
0.022
HDD
3
a
0.024
86
You
254
a
0.043
1/183001
a
0.046
I/183You-161
a
0.036
I/48You-10
a
0.033
1/23
Liang
You
a
0.019
I/99You-307
a
0.035
y
-Y0
u
242
a
0.029
Qiu
Xianggen
b
0.030
Xianggen
109
b
0.028
Xianggen
221
b
0.026
Glutinous
22
c
0.034
Glutinous
008
c
0.041
Xiang
Dao
d
0.045
a
Round
-grained
rice.
b
Fragrant
round
-grained
rice.
Glutinous
rice.
d
Long
-grained
rice.
Statistical
analysis
Statistical
analysis
was
performed
using
the
SAS
program
for
PCs.
21
Significant
differences
between
individual
treatments
were
determined
using
Duncan's
multiple
-range
test.
RESULTS
AND
DISCUSSION
Selenium
concentration
in
rice
products
of
different
species
Table
1
shows
the
mean
Se
content
in
rice
products
of
different
species
cultured
mainly
in
Southern
China;
the
average
value
was
0.033
±0.008
µg
g
-1
and
the
maximum
0.046
µg
g-
1.
Polished
round
-grained
rice
is
the
main
food
type.
Owing
to
their
wide
consumption,
rice
products
are
the
main
source
of
Se
for
inhabitants.
However,
the
contribution
of
these
rice
products
to
the
mean
Se
intake
in
Southern
China
is
estimated
to
be
only
about
10-13µg
Se
day
-1
per
person
assuming
a
mean
consumption
of
300-400g
of
rice
products.
This
low
Se
intake
from
ordinary
rice
products
is
mainly
responsible
for
the
Se
-deficient
status
of
inhabitants
in
Southern
China.
Effect
of
Se
-enriched
fertiliser
on
Se
content
in
rice
products
The
Se
concentrations
in
rice
products
after
foliar
application
of
Se
-enriched
fertiliser
and
sodium
selenite
are
given
in
Table
2.
Compared
with
the
control,
the
Se
concentration
was
significantly
in-
creased
by
Se
treatment.
There
was
no
significant
effect
on
rice
seed
yield
and
quality,
including
protein,
lipids
and
crude
ash,
between
Se
treatment
and
control.
No
significant
difference
in
Se
concentration
of
rice
products
was
found
between
treatments
with
Se
-enriched
fertiliser
and
sodium
selenite.
However,
the
Se
content
of
rice
products
sprayed
with
Se
-
enriched
fertiliser
was
marginally
greater
than
that
of
products
sprayed
with
sodium
selenite,
which
showed
that
Se
-enriched
fertiliser
had
a
greater
or
at
least
the
same
effect
on
increasing
Se
content
in
rice
products.
In
addition,
the
Se
concentration
of
rice
products
was
significantly
increased
(by
0.178
and
0.355
µg
g
-1
)
by
foliar
application
of
Se
-enriched
fertiliser
at
14
and
Table
2.
Effect
of
foliar
application
of
Se
-enriched
fertiliser
and
sodium
selenite
on
Se
content
and
grain
quality
of
rice
Treatment
Yield
(kg
per
plot)
Se
content
(µgg
-1
)
Protein
(%)
Lipids
(%)
Crude
ash
(%)
Control
9.40
±0.19a
0.002
±
0.002a
8.51
±
0.56a
5.39
±
0.18a
0.057
±
0.01a
Sodium
selenite
(18g
Se
ha
-1
)
9.65
±0.53a
0.411
±0.045b
8.24±0.03a
5.41
±0.69a
0.68±0.05a
Se
-enriched
ferti
liser
(18g
Se
ha
-1
)
9.85
±0.08a
0.442±0.080b
8.29±0.35a
5.00
±0.49a
0.68±0.04a
Within
the
same
column,
means
followed
by
a
different
letter
are
significantly
different
at
P
<
0.05.
Table
3.
Effect
of
foliar
application
of
Se
-enriched
fertiliser
on
Se
content
of
rice
products
in
different
Se
-deficient
areas
of
China
Location
Rice
species
Sample
number
Treatment
Se
content
(µg
g
1
)
Yancheng
County
Wuyujing
No
3
n=14
Control
0.003
±0.002a
Se
-enriched
ferti
liser
(14g
Se
ha
-1
)
0.178±0.072b
Ganyu
County
9915
n=9
Control
0.002±0.002a
Se
-enriched
ferti
liser
(18g
Se
ha
-1
)
0.355±0.132b
Within
the
same
column,
means
followed
by
a
different
letter
are
significantly
different
at
P<0.01.
y
sci
Food
Agric
82:869-872
(online:
2002)
871
Q
Hu
et
al
18g
Seha
-1
in
different
regions
compared
with
no
Se
treatment
(Table
3).
The
concentration
and
amount
of
Se
-enriched
fertiliser
can
be
varied
to
achieve
an
optimum
concentration
of
Se
in
rice
products.
The
authors'
previous
results
demonstrated
that
applica-
tion
of
sodium
selenite
to
soil
was
less
effective
in
increasing
the
Se
concentration
of
crops.
In
addition,
the
cost
of
the
amount
of
Se
required
is
much
greater
than
that
of
foliar
spray.
22
Foliar
spraying
was
also
found
to
be
a
safe,
effective,
convenient
and
low-cost
means
to
increase
the
Se
content
of
rice.
Contribution
of
Se
-enriched
rice
products
to
increase
in
Se
intake
There
are
many
Se
-deficient
areas
in
China.
Table
salt
fortified
with
15mg
sodium
selenite
kg
-1
is
used
as
a
daily
Se
supplement
to
reduce
the
incidence
of
primary
liver
cancer.
This
supplies
an
additional
35-50µg
Se
day
-1
to
individual
diets.
However,
the
bioavailability
of
Se
from
organic
sources
has
been
found
to
be
approximately
twice
that
from
inorganic
Se
added
as
a
dietary
supplement.
10,11
Supplemen-
tation
of
200µg
Se
day
-1
was
found
to
be
effective
in
reducing
the
incidence
of
several
types
of
cancer,
including
lung,
colon,
rectal
and
prostate
cancers,
in
patients.
23
Since
the
early
1980s,
Se
as
fertiliser
has
been
extensively
used
to
produce
appropriate
levels
of
Se
in
feed/food
crops,
notably
in
Finland
and
New
Zealand.
An
application
of
10g
Seha
-1
can
raise
feed
crop
Se
levels
sufficiently
to
meet
the
needs
of
live-
stock.
16
Foliar
spraying
of
Se
-enriched
fertiliser
can
produce
functional
rice
products
with
an
optimum
Se
concentration
acceptable
for
human
health.
The
opti-
mum
Se
content
of
rice
products
can
be
achieved
by
varying
the
concentration
and
amount
of
Se
-enriched
fertiliser.
When
the
Se
level
of
rice
products
is
con-
trolled
at
0.15-0.5
µg
g
-1
,
daily
consumption
of
350g
of
these
Se
-enriched
rice
products
can
increase
human
Se
intake
by
100
µg
day
-1
on
average.
ACKNOWLEDGEMENT
This
project
was
supported
by
the
National
Key
Basic
Research
Support
Foundation
under
grant
G1999011808-3.
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