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BULl.
PHll.
BIOCHEM.
SOC. 5,6:
31-39
(1982-83)
AMINO ACID COMPOSITION OF VEGETABLES
AND FRUITS FROM THE PHiliPPINES
Dahinog, M. Jr., * E.D. Rafols**,
V. laspinas***, H.K.F. lau* and
* .
T.R.C. Boyde
ABSTRACT
Vegetables
and
fruits
commonly
consumed
in the Philippines
were
analyzed for their amino acid composition.
In all, thirty-three
samples were
pulverized, lyophilised and then were subjected to acid and alkaline hydrolyses. On the amino acid compositional
basis, these foodstuffs would provide
a balanced source of dietary protein in general, if supplemented
by synthetic'
phenylalanine
and methionine.
The minimum amounts of proteins from these
foodstuffs
needed to provide sufficient
essential amino acids to ma'intain
nitrogen balance were computed.
The quality of proteins was also estimated
by their chemical
scores. The significance
of these results is discussed.
INTRODUCTION
Fruits and vegetables constitute
staple foodstuffs
in most Asian countries including the Philippines. Although they are thought to be good sources
of vitamins, minerals and fibre, their importance in providing a balanced diet
of protein is usually overlooked.
Ample research effort has however shown
that plant materials can also offer proteins of high nutritional value.
Soya beans and other legumes enjoy great success as major protein
sources. Leaf protein concentrates
from a variety of plants were found to
give favorable balance of essential and nonessential
amino acids, comparable
to animal products (', 2). Even the potato tuber, which is commonly
considered an "energy food", has also been found to contain protein of high
biological value (3, 41. Since the amino acid composition
and the biological
value of a protein are related, we report here the content of eighteen common
amino acids found in thirty-three
*Dep t. of Biochemistry,
native Philippine
Davao Medical School,
··Dept. of Biochemistry,
Cebu City, Philippines.
Cebu Doctors'
"·Dept.
pines.
Gullas
of Biochemistry,
:fD~Pt. of Biochemistry,
fruits and vegetables.
Da vao City, Philippines.
College of Medicine,
College of Medicine,
University
kong.
31
of Hongkong,
Mandaue
Osmena B/vd.,
City,
rhi/ip-
Sassoon Road,
Hong-
DAHINOG
et al.
MATERIALS AND METHODS
Fresh fruits and vegetables
small pieces,
samples were
before use.
the
ground
in pestle
further
flown
in from the Philippines
and mortar
pulverised
and
and lyophilized.
strained
through
were cut into
The freeze-dried
an 80-mesh
Total nitrogen content was determined
by sulfuric
presence of selenium dioxide (5) and nesslerisation
sieve
acid hydrolysis in
with a modified
Nessler reagent according to Middleton (6). Crude protein was estimated
by
multiplying 6.25 the nitrogen concentration
and is reported on an as-is basis
(lyophilized samples).
Sample hydrolysis
prior
to amino
acid
analysis
was carried
out
at
110°C with 6 M HCI for 24 hours using the heat-sealed, vacuum tube method of Savoy et al. (7). In some samples, internal standard norle·ucine was
included
recovery
in the hydrolysis
and calculation
was done on the basis of the
of norleucine.
To avoid interference
due to the large amount of
carbohydrates
present in the plant materials, all hydrolysates
were chromatographed
on a Dowex 2-X8, 200-400 mesh column in order to remove
humin (8). The column was run with 25 mM sodium citrate buffer, pH 2.2.
The column effluent containing the amino acids was lyophilized, redissolved
in enough distilled water to a volume which gave the final citrate concentration of 0.2M, and chromatographed
in an LKB 4400 automatic
amino ac.;id
analyser. The resulting chromatograms
were quantitated
by comparison
with
that obtained from a standard amino acid calibration mixture.
Trytophan,
which was destroyed
du ring acid hydrolysis,
was determined by 5 M NaOH hydrolysis,
also in a sealed, vacuum tube method according to the Method W of Spies (9).
Sulfur-containing
amino acids were not determined
separately.
They
were estimated from the acid hydrolysis chromatograms
by assum ing that the
average loss of methionine
in unoxidized
samples was 52.3% and that of
cysteine + cystine was 62.2<'10, according to the data obtained by Kaldly and
. Markakis (3).
RESULTS AND DISCUSSION
The total
determinations
protein
showed
content
on a dry weight
a range of 11.6% (sayote)
basis as ar. average
to 47.7%
(kangkong)
of two
with
·a me.an value of 24.9% (Table 1). Although on a wet weight basis the total
percentage of protein is normally quite small, the process of lyophilisation
obviously concentrated
the protein. This was borne out in the potato tuber,
whose apparent protein concentration
was increased six-fold in one study,
from 1.9% to 11.2% (12) or about five·fold from 2.1% to 10.3% in another
stu dy (3).
32
AMI NO ACt DS OF FRUI TS AND VE GET AB LE S
In all the foodstuffs tested, the amounts of glutamic
acid dominated
all other amino acids. With the exception
acid and aspartic
of alugbati, cab-
bage, iba, squash and sayote, aspartic acid constituted
more than 10% of the
total am ino acids of each sample. Glutamic acid constituted
more than 10%
in all samples other than kangkong,
On the contrary,
katuray,
sulfur-containing
saluyot
amino
and sampaloc.
acids were present
at much·
lower levels. The essential amino acid methionine
was especially poor in almost all samples tested. In fact, the amount of methionine
in cabbage, camote
tops, eggplant, malunggay fruit, pechay and sampaloc fruit was extremely
small, less than one percent
of t:::>talamino
acid in each case. Methionine
also been found to be limiting in many plant foodstuffs
leaf protein concentrates
(14) and potato (3).
The nex t essential
amino
has
such as legumes (13),
acid that seemed to be present
in low amount
was phenylalanine.
The deficiencies
of methionine
and phenylalanine
were
not apparent in terms of percentage of total amino acids as shown in Table 1.
However, when the daily amounts of proteins needed to maintain nitrogen
balance are computed
as shown in Table 2, it was obvious that meth ionine
as well as phenylalanine
supplementation
would be needed, in general, to
give a balanced protein diet. Exceptions
were found in cadyos and mongo·
where tryptophan
was limiting,
in sampaloc
fruit and singkamas where
isoleucine was limiting and in bamboo shoots where lysine w?s limiting.
This was in addition to methionine
deficiencies in the said materiiJls.
Although
the computations
given in Table 2 indicated
obvious
deficien-
cies in the foodstuffs
tested, their biological values could be compared
in a
different manner. The quality of the proteins and therefore the first approximation of their biological values was scored as a "percentage
of adequacy"
against a reference "ideal protein" recommended
by FAO/WHO and is given
in Table 3. Tyrosine and cysteine + cystine were included because of their
sparing oction on phenylalanine
and methionine,
respectively.
The protein
score, based on the limiting amino acids, was very widely spread between
17 for upo, and 100 for alugbati and sayote. The deficient amounts of
methionine
could not be compensated
for by cysteine + cystine and therefore limited
the biological
value of most samples
tested.
On the other
hand,
tyrosine did indeed correct some limitations due to phenylalanine.
In addition some inadequacies
in lysine, or leucine could be demonstrated
using
calculations of this kind. For comparison,
we cite other protein scores fro~
the same FAO/WHO Report: whole egg, 100; human milk, 100; cow's·mi1k
95; soya bean 74, sesame 50, groundnut
65, cottonseed
81, maize 49, millet
63, polished rice 67 and whole wheat, 53. Therefore, it could be seen that
many of the fru its and vegetables listed in Table 3 compared favorably
in
terms of their protein scores.
It might be concluded
on the basis of the amino acid compositions
obtained that most of the samples tested had proteins of high nutritional
33
~
-
% Protein
I
6.6
3.8
13.3
3.4
2.2
1.5
1.3
4.6
Val
0.4
8.9
7.7
8.5
2.1
3.6
12.5
Glu
2.5
13.5
5.6
2.4
6.7
6.3
7.4
lie
8.2
1.2
5.5
5.0
3.5
4.3
4.5'
5.0
5.9
13.5
His
Phe
0.63.19.2
8.:1
9.4
6.9
5.6
1.4
'5.2
7.1
12.722.0
0.83
2.7
11.3
3.3
3.2
0.7
6.2
7.6
2.6
7.3
5.9
5.5
6.8
15.1
5.9
5.8·i
3.9
4.2
5.5
3.5
7.3
10.4
20.1
11.1
12.6
5.8
6.1
5.6
5.4
10.5
19.2
2.8
10.0
20.2
Pro
1.8
11.9
4.5
2.0
3.0
7.5
8.6
1.9
9.1
0.8
1.1
1.0
Leu
12.7
1.8
3.2
4.6
4.4
4.5
5.2
4.7
3.0
4.1
7.0
5.0
.4Ala
C
12.9
Shoots
6.3
6.7
20.8
3.6
11.8
5.5
11.3
5.4
charantia
Bambusa
48.7
Arg
Met
Botanical
0.6
10.4
7.3
5.4
4.9
3.3
9.0
5.4
3.5
3.7
4.2
3.4
52.0
4.4
5.3
2.8
5.8
0.5
6.0
2.0
6.5
4.1
4.0
4.4
1.6
Thr
6.3
6.4
1.0
2.1
1.6
3.4
5.8
2.7
5.0
Basella
Momordica
Brassica
30.2
28.7
218.7
3.5
Tyr
2,0
...•
8.5
Solanum
blumeana
30.7
26.5
27.8
Gly
Essential bLys37.4'
Try
Ser
3.1
3.7
batatas
esculenra
cajan
Colocasia
vulgaris
Cajanus
IUnn.
IName
26.0
2.5
Cysc
Asp
esculenta
19.9
Z
:r:
Table
1. Amino
acid composition
(Takway)
Gabi
NameLeaves
Ampalaya
Potato
Leaves)
Lam.
Baguio
Beans
Phaseolus
Cucumber
Camote
Tops
Ipomoea
1.0 I
Protein Source
Non Essential
of freeze-dried
fruits and vegetables.
Amino Acids
•
~III
0
CD
C)
"
---m
'" }>
8.4
(Squash)
(continued
(Squash)
Kalabasa
Patola
en
5.3
maxima
c:
3.0
7.0
2.1
Cucurbita
2.9
3.1
4.9
2.4
1.4
1.6
4.6
.4
10.2
5.2
3.9
4.9
3.8
4.3
3.7
0.4
2.2
5.2
7.4
5.4
1.8
1.5
3.8
3.1
4.7
.8 I22.6
Abelmoschus
oleifera
Sesbania
Phaseolus
004
8.2
Averrh~
3.4
13.0
Luffa
2.7
2.9
5.7
9.6
1.9
4.8
0.8
4.4
3.9
3.2
3.5
6.4
6.6
3.9
5.4
6.7
3.3
7.5
98.6
6.7
3.6
3.4oleifera
2.1
0.7
2.6
8.9
12.6
5.0
14.1
6.9
4.0
4.1
4.6
1.5
0.6
2.0
11.6
7.2
1.3
2.3
3.1
5.8
6.8
10.6
7.0
7.0
18.2
6.0
4.2
3.9
6.2
5.3
Cucurbita
4.2
8.8
6.3
21.1
8.1
9.8
Amanthus
Ipomoea
4.8
6.9
6.5
7.5
7.9
6.2
0.9
12:3
8.2
7.3
6.4
6.7
0.23
6.8
10.2
16.8
5.6
6.0
30.5
4.7
8.3
1.0
5.0
10.5
9.5
5.1
4.1
6.3
5.9
3.0
6.1
1.7
3.7
34.9
.8
19.7
4.3
5.1
9.7
9.1
15.5
4.9
3.7
10.7
15.4
6.2
maxima
10.447.7
3.2
Iba
<
Moringa
17.8
20.5
bilimbi
23.6
linn.
17.9
I4.7
3.4
}>
329.0
33.2
23.8
24.0
4.8
9.0
27.6
23.8
2.9
Malunggay
Z
1.7
029.2
-I
JJ
C)
Leaves
()
0
en
3:
CD
nextKalabasa
Linn.
page)
~
22.0
en
r~0mmZ}>
"T1
"T1
}>
.J
0
Scchium
edule
Brassica
Sitao
3.9
0.7
2.5
5.0
6.0
Tamarindus
4.6
2.1
9.9
4.4
4.1
2.0
2.3
6.0
5.2
6.6
Oochorus
3.9
15.3
5.8
3.6
6.8
5.1
5.5
0.5
3.5
13.1
6.0
1.3
3.1
10.1
0.6
03.7
4.2
5.4
4.7
2.6
6.7
8.1
5.7
7.3
5.3
2.8
16.2
9.7
1.5
8.7
4.1
7.9
7.4
2.7
8.6
8.2
15.4
4.7
7.1
6.1
4.9
0.73
7.8
7.7
1.9
12.6
4.7
5.5
16.1
4.3
3.8
6.9
1.0
6.5
3.1
8.5
0.9
3.8
6.7
14.4
5.5
6.7
4.5
2.1
9.0
1.0
19.0
8.1
13.5
7.0
19.6
12.5
2.4
0.4
9.3
5.4
15.9
3.0
10.9
2.2
1.6
2.4
4.2
19.7
5.3
4.0
11.0
10.4
6.3
6.6
8.3
22
5.8
2.1
10.8
2.7
3.2
8.8
3.3
11.7
4.7
10.6
4.3
19.8
4.6
4.4
22.3
8.4
5.0
14.2
2.5
indica
Linn
4.9
4.8
5.0I6.3
Vigna
paradiciaca
24.5
5.0
19.0
1.6
Dioscorea
4.0
4.0
15.8
27.8
21.1
(Jacq.)
Swartz
Andropogon
1 continued
Legenaria
5.0
ITable
2.4
26.6
11.6
14.1
7}
3.1
~6.7
0
(Tamarino)
Linn.
Sayote
Puso
(Banana ~
Musa
nonprotein
nitrogen
was
present,
protein
content
expressed
as total (3).
amino
Ubi (Yam)
Upo
"Old
b:.:n
I~t
during
acid
hydrolysis
to was
Kaldy
andacid
Menkakis
Sampaloc
Saluyot
differences
experimental according
error.
Since
amino
content
and notacid
totalresidues.
nitrogen limits nutritive value of crude proteins, and little
hRcQuired
by were
adult within
man (10,15).
Pechay acids
aAmino
expressed
per cent
calc~lated
from
total amino
acids recovered.
Whenbycalculations
were
basedandon62.2%
crude ofprotein
(N x 6.25).
(;11J1al
mr:thionine
contentas and
cysteine
+ cystine
content
were adjusted
respectively,
assuming that
52.3%
these amino
acids
1.6
\ 3.9
:J:
»
C')
Z
neededb
Amount AND VEGETABLES
371
32
32
125
1
2
36
31
454
100
20
146
122
115
164
45
25
43
63
31
21
60
62
44
45
42
81
71
52
94
51
7
11
54
94
51
3
50
8
1
7
1
38
33
41
37
26
24
21
118
18
144
245
104
168
550
157
33
22
34
23
42
26
24
41
30
27
20
3
35
2128
47
19
96
85
20
26
7
58
43
54
44
20
47
46
66
72
2
5
53
10
24
58
47
54
53
73
7
4
0
9
6
3
6
44
30
25
34
24
22
Met
PtE
lie·
Leu
22
314
92
22
79
63
4..2
29
116
38
29
550
75
84
83
65
100
147
10
0
37
67
49
9
13
147
18
80
9
7 "2.2
80
31
28
0.5
1.6
48
108
36
37
52
53
48
27
6
81
52
5
5
8
32
318
39
79
2
386
73
8
27
Val
Thr
Minimum
40
3
63
79
4
367
275
88
1
00
60
30
2.2
1.0
1.4
AMINO "30
ACIDS
OF FRUITS
Try
each
essential
amino
acid
to
maintain
nitrogen
balance in adult
man.
tation·assumed
.
adult
man.
Dietary
levels
according
to
Rosein (10).
methionine) to maintain nitrogen balance
adult
man. Methionine
supplemen~otal grams protein needed to provide sufficient essential amino acids (except
maintain Table
nitrogen
balance inof protein in food stuffs
Amiro
Acid,lIrecommended level of
2. Amount
providing
Grams
Ly, Per Day
. 37
nLys scores
+
·96
69
69
98
99
17
40
17
94
96
100
83
14
III
86
75
lOO
Protein
94
14
+
Scorebet al.
Met
Phe
Leu
63
61
93
58
24
94
71
96
65
89
40
80
91
7B
45
60
42
23
23
49
88
.88
11
76
23
84
73
90
74
81
78
88
10
65
.• lOO61
72
93
'98
36
91 .
81
82
85
)100
lOO
Val
93·
90
98
79
90
18
83
))} 100
lOO
100
78
Thr
68
11
95
78
15
70
.100
36
76
98
94
-))})}.1oo
100
00
74
50
14
18
50
89
811
892
14
lOO
54
91
54
}100
Try
Cys
80
80
24
81
)100
23
82
})))'})100
80
100
)70
..
~
}12
100)
)})100
100
100
94
93
85
57
16
99
69
85
51
}))100
89
95
93
.))109
)100
100
100
.,)100
lOO
,)lOO
lOO.
lOO
lOO
86
87
97
100
.')100
) )100
)}100
100
)100
100
100
69
70
)}.100
)100
}100
)100
)81
OAHINOG
1.00
.
-,i.to FAO/WHO, 1973 (11).
"most limiting
amino
acid")
according
bprotein
score
is
based
on
the
lowest
score
obtained
for
any of the essential amino acid (Le. the
rence amino acid patterna•
of freeze-dried
quality,
extent.
fruits
and vegetables
based
on refe-
if methionine. and phenylalanine
were supplemented
Although
the amino acid composition
alone does not
gical value and that digestibility
out to realize this, the present
and feeding experiments
have to be carded
study indicates that these plant foodstuffs
may be useful in helping to alleviate demand
proteins.
38
\
to a lesser
infer' biolo-
on much more expensive
animal
AMI NO ACIDS
OF FRUI TS AND VEGETABLES
ACKNOWLEDGMENT
The aut.hors would
like to thank
the technical
for running the amino aCid analyser and Andrew
gen determinations.
This research was supported
Hongkong
Researc~ Grant #335/032/0012
to
conducted during the tenures of M. Dahinog, Jr.,
V. Laspinas (1982-83) as China Medical Board
Hongkong.
LITERATURE
assistance
CITED
J. Agri.
1.
Lima, I.H., T. ~ichardson
13: 139 (1965),
2.
Hartman,
G.H., Jr., W.R. Akeson
Chem. 15: 74 (1967).
3;
Kaldy, M.S. and p. Markakis. J. Food Sci. 37: 375 (1972).
4.
Kofranyi,
E. and
1582 (1965).
5.
AOAC "Official
Analytical
Methods
Chemists,
and M.A. Stahmann.
F. Jekat.
of Analysis"
Landes
Food Chem.
J. Agr. Food
and M.A. Stahmann.
Forschber
Washington,
of P.C. Kwan
Siu for repeating the nitropartly by the University of
T. R.C.B. This research was
and E. Rafols (1981-82) and
fellows at the University of
NRhein-Westif.,
11 th Ed., Association
Nr.,
of Official
D.C. (1970).
K.R. J. A pp I. Chem. 10: 281 (1960).
6.
Middleton,
7.
Savoy, C. F., J. L. Heinis and R.G. Seals. Anal. Biochem. 68: 562 (1975),
8.
Larsen, I. and J.V. Mortensen.
9.
Spies, J.R. Anal. Chem. 39: 1412 (1967).
10.
11.
Rose, W.C. Federation Proc. 8: 546 (1949).
World
Health
lional 'Meetings
63 (1973).
12.
Anal. Biochem. 21: 466 (1967).
Harvey,
Organization
Report
Technical
Series
D. in Tables of the Amino
Commonwealth
Agricultural
Report
52. "Energy
Series
522/FAO
and Protein
Nutri·
Requirement"
Acids in Foods .and Feedingstuffs.
2nd Ed. 52 (1970).
13.
Gritton,
(1975),
G.T., Y. Pomeranz,
and
G.S.
Robbins.
14.
Gerloff,
E.D .. I.H. Lima and M.A. Stachmann.
15.
Rose W.C., R.L. Wixom,
Chem, 217: 987 (1955).
H.B. Lockhart
,39
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