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JOURNAL OF FOOD COMPOSITION AND ANALYSIS (2000) 13, 859 }864
doi:10.1006/jfca.2000.0936
Available online at http://www.idealibrary.com on
SHORT COMMUNICATION
Nutrient Composition of Taro Corms and Breadfruit
A. S. Huang*, C. A. Titchenal*, and B. A. Meilleur-
*Department of Food Science and Human Nutrition, University of Hawaii, Honolulu, HI 96822,USA; and
-Center for Plant Conservation, Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166,U.S.A.
Received February 9, 2000; and in revised form May 19, 2000
Lehua and Bun-long (Chinese) variety taro corms and Hawaiian breadfruits were collected from
major production sites in Hawaii. The macro- and micronutrients were analyzed and statistically
compared. The Bun-long taro has signi"cantly (p(0.05) higher protein, ash and macro-mineral
contents when compared to Lehua taro and breadfruit. The dietary "ber content in both taro
varieties is higher than USDA data for taro. Breadfruit has signi"cantly lower "ber content but is
higher in vitamin C than the two taro varieties. The monosaccharides, glucose and fructose, are
signi"cant in breadfruit but not in taro corms. 2000 Academic Press
Key =ords: taro; breadfruit; Lehua; Bun-long; protein; dietary "ber; mineral; ash; vitamins;
vitamin C; monosaccharides; glucose; fructose; sucrose.
INTRODUCTION
Taro (Colocasia esculenta) is grown throughout the humid tropics mainly for its
edible corms, which are enlarged underground starchy stems. In Hawaii, taro
corms are used mainly for making poi, a sticky paste still consumed as a staple
by many Hawaiians (Huang et al., 1994). There are many varieties of taro grown
in Hawaii, but the Lehua variety, planted in #ooded "elds, produces the preferred
taro corms for poi (Moy and Nip, 1983). Another major taro variety, Bun-long or
the Chinese taro, has been introduced to Hawaii and is grown mostly in irrigated
but not #ooded "elds. The production of Bun-long has increased in recent years
due to its suitability in making taro chips (Nakamoto et al., 1994). However,
both taro chips and poi manufacturers in Hawaii use the same set of USDA
nutrient data as the nutrient reference source that does not account for any varietal
di!erences.
Breadfruit (Artocarpus altilis) in Hawaii is a large tree with edible fruits. The
plant has been distributed by Polynesians throughout Oceania and is absent only
on Easter Island, Chatham Islands, and New Zealand in Polynesia. The starchy
fruits are mostly composed of water and carbohydrates (Miller and Branthoover,
1957), but previous nutrient data were limited in scope and relied on older and
less precise analytical techniques. The purpose of this study is to analyze and
statistically compare the nutrient composition of the breadfruit variety most com-
monly consumed in Hawaii with the compositions of Lehua and Bun-long taro corms.
To whom correspondence and reprint requests should be addressed. Fax: (808) 956-4024. E-mail:
ahuang@hawaii.edu
BALA Jayashree yamuna JFCA*20000936 DATE 10*7*2000.........................
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MATERIALS AND METHODS
Sample Preparation
Average full-grown taro corms and breadfruits were randomly selected at major
production sites in Hawaii. The taro corm maturity was based on corm weight. The
breadfruits were mottled but still "rm and not overripe. The sites selected to collect
breadfruit were Hilo and Keauhou (Kona). Hanalei (two samples), Haleiwa, Hilo, and
Waipio were sites for Lehua taro, and Molokai, Hilo, and Haleiwa (two samples) for
Bun-long taro. The average taro corm weight was approximately 900 g and the
breadfruits weighed between 1350 and 1800 g. The samples were washed and peeled
immediately. The breadfruits were sliced in half and the cores removed. The #esh of
individual taro corms and breadfruits was then cut approximately into 3 cm squares,
blended together and treated as individual samples. Triplicate samples were prepared
for each collection site. Each sample was placed in a triple-layered freezer bag, labeled
and frozen overnight, before being transported to the University of Hawaii at Manoa
campus located in Honolulu.
Moisture Analysis
The samples were thawed in sealed plastic bags by immersing them for approximately
30 min in a running water tank. The thawing was done within two days from sam-
ple collection to avoid excessive tissue damage to the samples. Two accurately
weighed representative portions of approximately 10 g each were dried at 1003Cto
constant weight for the determination of moisture content. The majority of the
remaining samples were freeze-dried for nutrient analysis. A small portion of approx-
imately 50 g from each sample was saved for immediate analysis of vitamin C content.
Each nutrient was analyzed in duplicate.
Macronutrient Analyses
Protein (Kjeldahl), fat (ether extract), and ash in the taro and the breadfruit were
determined by the American Association of Cereal Chemists (AACC, 1995) methods
No. 46-12, 30-25, and 08-01, respectively. The starch was determined by removing
free sugars with 10 volumes of 85% ethanol 3 times and then drying overnight at
403C. The dried powder was then enzymatically hydrolyzed as described in the Associ-
ation of O$cial Analytical Chemists (AOAC, 1995) method 979.10, employing
amyloglucosidase. The resulting glucose was quanti"ed by high-performance liquid
chromatography (HPLC) as previously described (Huang et al., 1994).
Dietary Fiber
The soluble and insoluble dietary "bers were analyzed using the enzymatic gravi-
metric method described by Lee et al. (1992). The total dietary "ber content was
calculated as the sum of the amounts of soluble dietary "ber and insoluble dietary
"ber.
Measurement of Individual Sugars
The sugars (glucose, fructose, and sucrose) were extracted in duplicate using the
AOAC (1995) method 982.14C. After "ltration, the extract was treated with a C18
Seppak cartridge using a mobile phase of acetonitrile}water (82 : 18, v/v). The second
860 HUANG, TITCHENAL AND MEILLEUR
pass of the eluate was collected. The eluate was analyzed by HPLC as described by
Huang et al. (1994).
<itamin Analyses
Both vitamins A and C were analyzed with HPLC methods. Vitamin A analysis was
based on a method described by Singh and Bradbury (1988). The provitamin A in taro
and breadfruit was saponi"ed in 10% KOH in alcohol}water (50 :50, v/v) at 803C for
1 h. After "ltration the solution was extracted with hexane. Separation on the HPLC
was achieved using a 5 lm C-18 steel column with a mobile phase of methanol}
acetonitrile}water (40:40:20, v/v/v). Vitamin C was extracted in aqueous metaphos-
phoric acid (5%) as described by Bradbury and Singh (1986a). The HPLC condition
of using a micro-Bondapak-NH2 cartridge and a pH 4.6 phosphate bu!er as the
mobile phase was also adopted. The total vitamin C content equals the sum of the
amounts of ascorbic acid and dehydroascorbic acid.
Thiamin, ribo#avin and niacin were quanti"ed by methods described by Bradbury
and Singh (1986b). Thiamin was extracted in 0.1 NHCl at 1003C for 1 h. The super-
natant after centrifugation was treated with basic lead and dilute sulphuric acid and
subjected to centrifugation again. The thiamin was oxidized to #uorescent thiochrome
in alkaline solution using potassium ferricyanide. The #uorescence was measured with
an excitation wavelength of 370 nm and an emission wavelength of 455 nm. Ribo#a-
vin was extracted by homogenizing samples in acetate bu!er at pH 4.3 and then
heated at 1003C for 1 h. After centrifugation, the supernatant solution was oxidized
with potassium permanganate, and the #uorescence of the ribo#avin was measured
with an excitation wavelength of 440 nm and an emission wavelength of 530 nm.
Niacin (nicotinic acid) was extracted in 0.5 MHSOand heating at 1003C for 1 h. The
pH was adjusted to 4.5 with sodium hydroxide and the solution was "ltered. Addition
of ammonium sulphate followed by cyanogen bromide and sulphanilic acid produced
a colored compound for quanti"cation. The color intensities at 440 nm from the
sample and a blank which contained only ammonium sulphate, cyanogen bromide
and sulphanilic acid were compared following the methods of Bradbury and Singh
(1986b).
Minerals
All minerals were measured by the Agricultural Diagnostic Services of the University
of Hawaii using an inductively coupled plasma machine (ICP/6500, Perkin-Elmer
Instruments, Norwalk, CT).
Statistical
Measurements of replicate samples were averaged to obtain a single datum point.
Di!erences in averages were analyzed for statistical signi"cance using ANOVA and
Duncan's multiple-range test. Statistical analyses were conducted using the STAT-
PAK software program (Northwest Analytical Inc., Portland, OR). All the results are
expressed on as-is-basis.
RESULTS AND DISCUSSION
Table 1 compares the macro- and micronutrients in raw Lehua and Bun-long taro
corms and Hawaiian breadfruit. Water content is high in these starchy staples which
TARO CORMS AND BREADFRUIT 861
TABLE 1
Nutrient composition of breadfruit and taro corms, mean (S.D.)
Taro (Lehua) Taro (Bun-Long) Breadfruit
Nutrients (n"15) (n"12) (n"6)
Proximates (g/100 g)
Moisture 72.4 (6.2) 65.8 (8.4) 73.5 (5.6)
Protein 1.1 (0.1) 1.9 (0.2) 1.2 (0.1)
Fat 0.2 (0.02) 0.2 (0.02) 0.3 (0.02)
Ash 1.0 (0.2) 1.8 (0.2) 0.9 (0.2)
Starch 19.2 (2.6) 23.1 (3.4) 20.1 (2.2)
Total "ber 3.6 (0.3) 3.8 (0.3) 0.9 (0.1)
Soluble 1.3 (0.1) 0.8 (0.1) 0.2 (0.02)
Energy (kJ)372.6 468.0 416.5
Sugars (g/100 g)
Sucrose 1.3 (0.1) 2.0 (0.2) 1.7 (0.1)
Fructose 0.1 (0.01) 0.2 (0.02) 0.6 (0.07)
Glucose 0.1 (0.02) 0.2 (0.04) 0.6 (0.05)
<itamins (mg/100 g)
Vitamin A (LOD(LOD(LOD
Thiamin 0.05 (0.01) 0.07 (0.01) 0.28 (0.03)
Ribo#avin 0.06 (0.01) 0.05 (0.01) 0.10 (0.01)
Niacin 0.64 (0.07) 0.82 (0.06) 1.70 (0.10)]
Vitamin C 15 (2) 12 (1) 21 (2)
Minerals (mg/100 g)
Calcium 38 (7) 65 (6) 28 (7)
Phosphorus 87 (8) 124 (15) 28 (2)
Magnesium 41 (5) 69 (8) 34 (7)
Sodium 11 (2) 25 (3) 7 (3)
Potassium 354 (48) 861 (79) 289 (43)
Iron 1.71 (0.18) 1.44 (0.16) 0.40 (0.06)
Zinc 0.17 (0.03) 0.21 (0.03) 0.09 (0.01)
Copper 0.12 (0.02) 0.10 (0.01) 0.08 (0.02)
Boron 0.12 (0.02) 0.09 (0.01) 0.52 (0.02)
Estimated energy content calculated from available carbohydrates, protein, and fat using 16.74, 16.74
and 37.67 kJ/g, respectively.
LOD: less than limit of detection (0.005 mg/100 g).
on average ranges between 65.8% for the Bun-long taro to 73.5% for the breadfruit.
The protein content in Bun-long corms is signi"cantly ( P(0.05) higher than those in
Lehua taro and Hawaiian breadfruits. This protein content is approximately the same
as raw potatoes and may be one of the reasons why it is the taro variety commonly
used for making chips. The protein content of taro in the USDA database (SR-12,
1998) is listed as 1.9%, which is the same as we found in the Bun-long variety but
higher than that in the Lehua taro. The USDA data on breadfruit protein are
approximately the same as that found in our samples. All these starchy staples are low
in fat content, which also agrees with the USDA data.
The ash content in Bun-long was signi"cantly higher than in Lehua taro and
Hawaiian breadfruit, and was also higher than the USDA data for both taro and
breadfruits. The mineral pro"le we analyzed with ICP indicated signi"cantly higher
amounts of all major minerals (calcium, magnesium, phosphorus, sodium and potas-
sium) in Bun-long corms than in Lehua taro and Hawaiian breadfruit. Since our
862 HUANG, TITCHENAL AND MEILLEUR
samples for both taro and breadfruit came from several production areas in Hawaii,
the statistical di!erences can be attributed to varietal rather than geographical factors
Another clear di!erence between our data and USDA data is the dietary "ber
content in taro. The "ber content of taro corms in the USDA database is 0.9 g/100 g,
which is much lower than our data for both Lehua and Bun-long taro. The enzy-
matic/gravimetric method we used was recently adopted by the AOAC and di!ers
greatly from the acid digestion method used in the past. Based on our dietary "ber
data, when taro is used as a staple with an estimated consumption of 1 lb (454 g) per
meal by Paci"c Islanders, it alone can provide the common recommended dietary
"ber of 25 g per day. A similar high "ber content was previously reported by
Holloway et al. (1985) who analyzed taro collected in Tonga and found the total "ber
content to be 4.1% on a fresh weight basis. This result is close to our total dietary "ber
data in Table 1.
Among the vitamins analyzed, the vitamin C content in breadfruit is signi"cantly
higher than that in taro varieties. A 300 g portion of raw breadfruit contributes60 mg,
equivalent to the adult RDA (10th edn., National Research Council, 1989). When
consumed as a staple, the cooked breadfruits would still provide a substantial amount
of the daily vitamin C needs because ascorbic acid is retained well after cooking in
starchy foods. It has been documented (Abbott, 1992) that breadfruit was a signi"cant
trade item between native Hawaiians and European sailors in the late 18th and early
19th centuries which might have been an important source of vitamin C for Paci"c
explorers who had spent extended periods of time living at sea on preserved foods.
Among the three simple sugars analyzed, sucrose predominates in the taro varieties
and in the breadfruit. The sucrose content in Lehua taro is signi"cantly lower than in
the Bun-long taro and the Hawaiian breadfruit. The monosaccharides glucose and
fructose are signi"cant in the breadfruit but not in the taro varieties.
Our results identi"ed signi"cant di!erences in protein, minerals, and sucrose
content between the two taro varieties. Signi"cant di!erences in dietary "ber and
vitamin C content between Hawaiian breadfruit and the taro varieties were also
found. When consumed as staples by Paci"c Islanders, these di!erences could be
nutritionally signi"cant.
ACKNOWLEDGEMENT
The authors wish to thank Kealakekua Ranch, Ltd., for a grant to B. A. Meilleur for research on the
Hawaiian breadfruit, some of the results of which contributed to this paper.
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864 HUANG, TITCHENAL AND MEILLEUR
