Research
Gonimbrasia belina (Lepidoptera: Saturniidae):
a Nutritional Food Source Rich in Protein,
Fatty Acids, and Minerals
Robert H. Clew, DavidJackson, Lorenzo Sena, Dorothy
Andrzej Pastuszyn, and Mark Millson
J. VanderJagt,
ABSTRACT
Larvae of the moth Gonimbrasia belina (Westwood) are used widely as food by the rural inhabitants of the semiarid
subcontinent of southern Africa. However, little is known about their nutrient content. Dry roasted larvae were vacuum-dried at 25"C,
ground to a fine powder, and analyzed for their content of total protein, individual amino acids, 14 trace minerals, and fatty acids. On a dry
weight basis, they averaged 48.3 % protein and the amino acid pattern compared favorably to that of soybean seeds and a World Health
Organization "ideal" standard. Of the 206 mg of total lipid per gram dry weight, 153 mg were contributed by fatty acids. Larvae are a good
source of essential fatty acids, linoleic acid (average, 17.5 mg/g dry weight)and a-linolenic acid (average, 58.1 mg/g dry weight. They also
contained several essential minerals in high quantities including calcium (average, 2,730 Ilg/g dry weight), iron (avetage, 304 ~lg/g), magnesium (average, 1,850 Ilg/g), manganese (average, 40.4 Ilg/g), and zinc (average, 142 Ilg/g). Overall, these data confirm that the larvae of G.
belina are, as has been assumed by those for whom it is regarded as both a staple and a delicacy, an excellent source of many nutrients
essential for the growth and development of children and the maintenance of health in people of all ages.
I
NSECTS
ARE USED AS FOOD BY INDIGENOUS
PEOPLES IN MUCH OF THE
world and their contribution to the diet may be an appreciable
proportion of the total protein and caloric intake (DeFoliart
1989). For example, in some districts in Zaire, insects furnish onethird to one-half of the animal protein consumed by the population
(Gomez et at. 1961). The misconception is widespread that insects
are used as food only during times of famine. On the contrary, when
in season or throughout the year when available, insects are consumed not only to ward off starvation but routinely as a regular
part of the diet (DeFoliart 1989). Because of their popularity as
dietary supplements, edible insects also constitute prominent items
of commerce, particularly in rural markets of sub-Saharan towns
and villages (Chavunduka 1975, Fasoranti and Ajiboye 1993).
The larva of the moth Gonimbrasia belina (Westwood) feeds on
a variety of trees including the mopane tree, Colophospermum
mopane (Kirk ex Benth) Kirk ex]. Leon. The emperor moth,1 or
mopane worm,' or 'madora' as G. be/ina is called locally by the
Shona-speaking
people of Zimbabwe, is used widely as a food
throughout its natural range in southern and tropical Africa where
it is regarded as both a dietary staple and delicacy (Chavunduka
1975). The large and spiny black and gray mottled caterpillar is
considered widely to be an important source of protein and other
essential nutrients by the rural inhabitants of the semiarid subcontinent from Namibia across Botswana, Zimbabwe, and South Africa
to Mozambique, especially during times when animal or cereal sources
of protein are scarce (Chavunduka 1975). However, information
concerning the specific nutrient content of the larva is lacking. We,
'Common name not currently among common names of insects and telated organisms approved for use by the ESA Committee on Common Names of Insects.
250
therefore, analyzed larvae gathered in Zimbabwe for their content
of 14 trace minerals; fatty acids, including the 2 that are essential
(linoleic acid and a-linolenic acid); and 18 of the common amino
acids, including those that are essential for humans. This article
presents the results of our analyses.
Materials and Methods
Approximately 40 G. belina larvae were purchased in the market
in Chidamoyo in northern Zimbabwe in March 1996 and dryroasted by local market women. They were placed in resealable plastic bags, stored at -20°C for 3-4 wk, and transported to Albuquerque, NM. The specimens were ground to a fine powder in a stainless
steel mill and dried to constant weight in a vacuum oven at 25°C. All
results are expressed in grams of dry weight.
Amino Acid Analysis. Larvae were analyzed in duplicate. Two to
three milligrams of each specimen were weighed and placed in I-ml
ampoules, to which the internal standard (norleucine, an amino acid
not commonly found in proteins) and 0.35 ml of 6 N HCl were
added. The ampoules were flushed with nitrogen, evacuated, sealed,
and placed in an oven for 24 h at 110°e. After hydrolysis, the acid
was removed by drying in an evaporative centrifuge. The samples
were then redissolved in 0.4 ml of 1 mM HC!. A 20-111aliquot of the
hydrolysate was withdrawn and subjected to derivatization.
Samples intended for the determination of cysteine were first
oxidized with performic acid (80% formic acid and 30% hydrogen
peroxide, 9:1) for 18 h at room temperature (Hirs 1967). Performic
acid was removed in an evaporative centrifuge and the samples were
hydrolyzed with 6 N HCI as described above.
The tryptophan content was determined in a separate analysis.
AMERICAN
ENTOMOLOGIST
•
Winter 1999
The weighed samples were placed in polypropylene
tubes and hydrolyzed for 18 h at 110°C in 4.2 M KOH containing 1 % (wt:vol)
thiodiglycol (Hugli and Moore 1972). After hydrolysis, the KOH
was neutralized with 4.2 M perchloric acid, and the supernatant was
removed and adjusted to pH 3 with dilute acetic acid. A 50-1!1 aliquot of each of the hydrolyzed samples was subjected to derivatization
as described below. Quantification
of individual amino acids was
performed using a standard amino acid calibration mixture that
was supplemented
with tryptophan.
Norleucine was the internal
standard used in all amino acid determinations.
Quality control
assurance for the tryptophan determination
was obtained by demonstrating that the method yielded the correct number of tryptophan
residues for egg white lysozyme.
Amino acids were quantified using the Pico-Tag system manufactured by Waters, Milford, MA. After hydrolysis, aliquots were dried,
mixed with 10 I!I of ethanol:water:triethylamine
(2:2:1), redried,
and derivatized with 20 I!l phenylisothiocyanate
reagent (ethanol:
water:triethylamine:phenylisothiocyanate,
7:1:1:1) for 20 min at
room temperature (Cohen and Strydom 1988). Excess reagent was
removed by evaporative centrifugation.
Derivatized samples were
dissolved in 0.1 ml of 0.14 M sodium acetate that had been adjusted
to pH 6.4 with dilute acetic acid. A 10-1!1aliquot was injected onto
the column.
Tryptophan analysis was performed using a Waters C18 reversedphase column (3.9 by 150 mm) and the solvents and gradient conditions were as described by Hariharan et al. (1993). Use of this
elution protocol was necessary to separate tryptophan from ornithine adequately, which results from the alkaline hydrolysis of arginine.
Analysis of the other amino acids was performed using a Waters
C18 column (3.9 by 150 mm) as described by Bidlingmeyer et al.
(1984). Briefly, the derivatized amino acids were separated on a C18
reversed-phase
column. The column was washed with increasing
concentrations
of organic solvent, causing individual amino acids to
be eluted at predetermined
times. Quantitation
was achieved by
monitoring the absorption of the column at 254 nm and comparing
the absorbance of individual peaks with that of the corresponding
amino acid standard. Duplicate samples of egg white lysozyme served
as controls. The data are reported in Table 1 as the mean ± SEM of
2 determinations.
Mineral Analysis. A sample (500 mg) of larvae was weighed and
wet-ashed by refluxing overnight with 15 ml of concentrated HN03
and 2.0 ml of 70% HCI04 at 150°C. The sample was dried at
120°C, and the residue was dissolved in 10 ml of 4.0 N HN03-1 %
Table 1. Comparison of the amino acid content of G. belina larvae
versus mature soybean seeds (mg/g dry weight)
G. belina
mean ± SEM
Amino acid
Mature soybeans"
mean
4.84
Tryptophan
5.62
±
Threonine
27.4
±
0.77
15.9
Isoleucine
Leucine
Lysine
21.5
31.2
±
0.98
1.41
35.8
±
1.27
17.6
28.5
23.9
Methionine
Cysteine
10.0
10.4
±
0.85
0.50
4.84
3.63
Phenylalanine
25.5
30.8
±
0.14
1.13
18.0
±
27.5
±
0.35
Tyrosine
Valine
±
±
0.13
14.3
17.7
32.0
10.7
Arginine
28.5 :l:1.41
Histidine
15.0
±
Alanine
25.2
±
1.27
17.9
Aspartate
53.0
±
2.47
46.4
Glutamate
Glycine
60.8
±
2.75
74.8
Proline
22.6:l: 0.28
24.6 :l:0.49
Serine
27.1
16.6
18.7
22.2
Total protein content
(mg/g dry weight)
±
0.14
2.61
388.5
482.7
Water content of fresh soybeans was assumed to be 67.5%
(Anonymous 1990). Mean ± SEM was not available for soybeans.
"Revised from Anonymous (1990).
HCl04 solution. The mineral content was determined by inductively
coupled argon plasma atomic emission spectroscopy
(ICP-AES,
Jarrel-Ash) as described elsewhere (Yazzie et al. 1994, Kim et al.
1997) and quantified against standard solutions of known concentrations that were analyzed concurrently.
Lipid Extraction and Fatty Acid Analysis. One milligram of an
internal standard (nonadecanoic acid) was added to 1 g of vacuumdried larva. The specimen was extracted with chloroform/methanol
(2:1, vol:vol) as described elsewhere (Chamberlain et al. 1993), and
the solid, nonlipid material was removed by filtration. Total weight
of the extracted lipid material was determined gravimetrically after
Table 2. Essential amino acid content of G. belina larvae and mature soybean seeds compared with the WHO ideal protein
G. belina
Soybeans"
Amino acid
% .of tot~I' (%
ammo aCids
amino aCid) x 100%
Ideal
%. of total (%
ammo aCids
amino aCid) x 100%
Ideal
WHO
idealb
Isoleucine
4.5
161
4.5
161
2.8
Leucine
98
128
7.3
111
6.6
Lysine
6.5
7.4
6.1
105
5.8
Methionine + Cysteine
4.2
168
2.2
88
2.5
11.7
186
8.3
132
6.3
Threonine
5.7
168
4.1
121
3.4
Tryptophan
1.2
109
1.2
109
1.1
163
4.6
131
3.5
Phenyblanine
+ Tyrosine
Valine
5.7
Water content of fresh soybeans was assumed to be 67.5% (Anonymous 1990).
"Revised from Anonymous (1990).
bWHO 1985.
'Total protein, 482.7 mg/g dry weight (see Table 1).
AMERICAN
ENTOMOLOGIST
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Volume 45, Number 4
251
Table 3. Lipid and fatty acid content of G. belitta larvae versus mature
soybean seeds (mg/g dry weight)
Fatty acid
mean", SEM
Mature soybeansa
mean
Lauric
Palmitic
Palmitoleic
Srearic
Oleic
Linoleicb
0.39", 0.09
39.0 '" 8.1
1.40",0.16
15.6 '" 1.8
20.3 '" 1.5
17.5 '" 2.5
58.1", 6.1
0.49 '" 0.12
0.19
17.6
0.34
6.47
38.8
86.9
11.6
0
Total fatty acid
(mg/g dry weight)
152.8
161.9
Total lipid'
(mg/g dry weight)
206.3
209.4
G. be/ina
a-linolenic"
Arachidic
Water content of fresh soybeans was assumed to be 67.5%
(Anonymous 1990). Mean", SEM was not available for soybeans.
"Revised from Anonymous (1990).
"This fatty acid is essential in humans.
'Total lipid content is the total amount of lipid determined
gravimetrically.
solvent removal under a stream of nitrogen. The samples then were
redissolved in anhydrous chloroform/methanol
(19:1, vol:vol) and
clarified by centrifugation at 10,000 [times] g for 10 min. Transmethylation of fatty acids in the chloroform/methanol
solvent was
performed using 14% (wt:vol) boron trifluoride in methanol
(Morrison and Smith 1964). A O.l-ml aliquot of each sample was
mixed with OJ ml of boron trifluoride reagent in a 2-ml Teflon-lined
screw-cap vial, placed in a water bath at 100°C for 25 min, and
cooled to room temperature. After the addition of 0.3 ml of water,
the transmethylated fatty acids were extracted into hexane. A calibration mixture of fatty acid standards was processed in parallel.
Aliquots of the hexane phase were analyzed by gas chromatography/mass spectometry. A Hewlett-Packard
gas chromatograph
(5890 Series II) with the Mass Selective Detector 5972A in scan
mode was used to separate and quantify fatty acids. Aliquots (1-2
~d) of the hexane phase were injected in splirless mode onto a DB225 column (30 m by 0.25 mm i.d., 0.25Ilm). The injector temperature was set at 250°C and the detector at 280°C; the oven at 70°C
for 1 min, then increased from 70 to 180°C at a rate of 20°C/min,
from 180 to 220°C at 3°C/min, and finally set at 220°C for 15 min.
The carrier gas was helium and the flow rate was 32 cm/s. Electronic
pressure control in the constant flow mode was used. The internal
standard (nonadecanoic acid, 19:0) and calibration standards were
used to identify and quantify fatty acids in the lipid extract.
Results
Protein Content attd Amino Acid Composition. Based on the
summation of the individual amino acids, the protein content in
larvae was high, approaching 50% of the dry weight (482.7 mg/g,
Table 1). In addition, the amino acid content of these larvae compared favorably with that of soybean seeds (Table 1) and to a World
Health Organization (WHO) standard protein for preschool children 2-5 yr old (WHO 1985) (Table 2). The WHO standard consists of 10 essential amino acids and excludes the nonessential amino
acids. As shown in Table 2, relative to the WHO reference protein
and soybean protein, the protein in larvae appears to be of high
252
quality. Particularly noteworthy is that the protein in larvae is not
deficient in tryptophan, cysteine, or methionine, essential amino acids that are wanting in many food insects (DeFoliart 1989).
Lipid and Fatty Acid Analysis. Lipids accounted for 20.6% of
the dry weight of the larvae and fatty acids accounted for most of the
mass of the crude lipid fraction (>,,75%) (Table 3). The saturated
fatty acids palmitic acid and stearic acid accounted for ",36% of the
total fatty acid content. Interestingly, at 58.1mg/g dry weight, the
essential fatty acid a-linolenic acid was the most abundant fatty acid
in larvae. The larvae also contained 17.5 mg/g dry weight of linoleic
acid, an essential fatty acid. Arachidonic acid, an important polyunsaturated fatty acid in human nutrition, was not detected in the
crude lipid fraction.
Mineral Content. Larvae contained significant amounts of several minerals that are nutritionally important (Table 4). Iron, which
is required to prevent anemia, was present at a level of 304 Ilg/g dry
weight. Calcium, an essential component of the mineral phase of the
skeleton, was present at 2,730 /lg/g dry weight. Larvae also contained appreciable quantities of magnesium and manganese (1,850
and 40.4 pg/g dry weighr, respecrively). Noreworthy, was rhe relatively high level of zinc (142 ~Ig/gdry weight). Proper zinc nutrition is
essential for the normal functioning of the immune system and,
therefore, is important in the body's defenses against infection. Although the larvae did not contain large amounts of sodium, they
were rich in potassium (15,800 Ilg/g dry weight). Selenium, an essential trace mineral and a constituent of glutathione peroxidase, was
not detectable.
Discussion
The results of this study provide yet more evidence in support of
DeFoliart's assertion that "insects can make a potentially enormous
contribution to solving problems of human nutrition" (DeFoliart
1989, 1995). Our data document that larvae of G. belina are a rich
source of essential amino acids, fatty acids, and certain trace minerals.
In many underdeveloped parts of the world, insects furnish a
large proportion of the animal protein consumed by the populaTable 4. Comparison of mineral content of G. belitta larvae versus
mature soybean seeds (mg/g dry weight)
Minerals
Arsenic
Calcium
Chromium
Copper
Iron
Potassium
Magnesium
Manganese
Molybdenum
Sodium
Nickel
Phosphorus
Selenium
Zinc
G. belina'
Soybeans"
NO
2,730
NO
7.1
304
15,800
1,850
40.4
NO
18.8
NO
6,340
ND
142
NR
6,070
NR
3.9
109
19,100
2,000
16.8
NR
462
NR
5,980
NR
30.4
Water content of fresh soybeans was assumed to be 67.5%
(Anonymous 1990). ND, not detected, level of sensitivity of method
was 5 ~g/g dry weight. NR, not reported.
aBased on a single sample.
bRevised from Anonymous (1990).
AMERICAN
ENTOMOLOGIST
•
Winter 1999
tion. For example, in 20% of the territories of Zaire (The Republic
of Congo) 22-64% of dietary protein was provided by various
insects (Gomez et at. 1961). However, although the protein content
(often 40-60%) and protein quality generally are high in most insects, the protein fraction of many food insects is deficient in methionine, cysteine, and tryptophan (Gomez et al. 1961, Defoliart
1995). In G. be/ina larvae, not only is the protein content high
(482.7 mg/g dry weight) (Table 1), the protein score is at or above
the WHO "ideal standard" in all 8 essential amino acid categories
(Table 2). In addition, the content of the essential amino acids and
their proportions in the proteins in larvae compared favorably with
those of soybean protein (Tables 1 and 2).
Gonimbrasia be/ina larvae contain a significant amount of lipid
(206.3 mg/g dry weight), ",75% of which (152.8 ~lg) is fatty acid
(Table 3). Thus, they can make a substantial caloric contribution to
the human diet. In addition to providing calories, these larvae also
represent an excellent source of 2 essential fatty acids, linoleic acid
and a-linolenic acid (Table 3). In comparison to soybean seeds, larvae contain one-fifth as much linoleic acid and 5 times more alinolenic acid. Interestingly, arachidonic acid, which is an n-6 polyunsaturated fatty acid crtitical to human health, was not detected in
the crude lipid extract of dried G. belina larvae.
The mineral content of G. belina was impressive. In general, the
larvae we analyzed compared favorably with soybeans and many of
the wild edible plants of the western Sahel that we have studied
(Yazzie et at. 1994, Kim et al. 1997, Sena at at. 1998). Noteworthy
were large amounts of calcium, iron, zinc, magnesium, and manganese. These minerals are integral components of human enzymes
and proteins (e.g., zinc in superoxide dismutase; copper in oxidation-reduction enzymes; iron in hemoglobin, myoglobin, and the
cytochromes) and playa critical role in numerous physiological processes, including those performed by the immune and respiratory
systems. The amounts of these minerals in the larvae are comparable
to their levels in soybeans (Table 4) and in the leaves of the baobab
tree that are consumed in many parts of sub-Saharan Africa (Yazzie
et at. 1994). We have no explanation of why the sodium content of
the larvae was so low compared with potassium.
In summary, our documentation of the presence in G. be/ina
larvae of large amounts of all of the essential amino acids, 2 essential
fatty acids (linoleic acid, a-linolenic acid), and many minerals critical
to normal growth, development, and health maintenance indicates
that this edible insect can play an important role in reducing the
incidence and severity of malnutrition that plagues the poor in southern Africa where this insect is abundant (Chavunduka 1975).
Acknowledgments
We thank Robert Borland and Sara Feresu (Biosciences Department, University of Zimbabwe) for their assistance in confirming
the identity of the G. be/ina specimens we analyzed; and Kathy
McCarty (Chidamoyo, Zimbabwe) for helping us acquire and transport the dried organisms. We are grateful to Florence V. Dunkel
(Department of Entomology, Montana State University, Bozeman)
for advice regarding the preparation of our manuscript. This study
was supported by a Minority International Research Training grant
from the Fogarty International Center of the National Institutes of
Health.
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A~IERIC:ANENTtn10l.OGIST •
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•
Robert H. Glew is Professor of Biochemistry and Molecular Biology at the
University of New Mexico School of Medicine. He has spent two sabbaticals in Nigeria and has taught and conducted research in sub-Saharan
Africa for almost 25 years on problems relating to maternal/child health in
rural populations. He is Director of a Minority International Research
Training (MIRT) grant from the Fogarty International Center of the National Institutes of Health. David Jackson received his M.D. degree in
1997 from the University of New Mexico School of Medicine. He currently
is in the second year of the Opthalmology Residency Program at Baylor
University College of Medicine. Lorenzo Sena, obtained his B.S. degree in
Biochemistry in 1998 at the University of New Mexico. He currently is
employed as an analytical chemist for the Environmental Protection Agency
in Kansas City, MO. Dorothy J. VanderJagt is a Research Assistant
Professor at the University of New Mexico School of Medicine and is Codirector of the UNM-MIRT Program. Her research interests are in the
area of maternal/child health and her expertise and training are in medical
biochemistry and nutrition. She has lectured and conducted research in
West Africa for the past eight years. Andrzej Pastuszyn is Research
Associate Professor of Biochemistry and Molecular Biology at the University of New Mexico School of Medicine where he directs the Protein
Core Facility. Mark Millson is an analytical chemist at the Nationallnstitue
of Occupational Safety and Health in Cincinnati, OH. His main research
interest is the analysis of the mineral and trace element composition of
biological materials.
253