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Journal of Food Composition and Analysis 21 (2008) 545– 552

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Journal of Food Composition and Analysis

0889-15

doi:10.1

� Corr

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Original Article

Levels of major, minor and trace elements in commercially available enset(Ensete ventricosum (Welw.), Cheesman) food products (Kocho and Bulla) inEthiopia

Minaleshewa Atlabachew, Bhagwan Singh Chandravanshi �

Department of Chemistry, Faculty of Science, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia

a r t i c l e i n f o

Article history:

Received 11 November 2007

Received in revised form

27 April 2008

Accepted 5 May 2008

Keywords:

Kocho

Bulla

Amicho

Enset

Ethiopia

FAAS

Major

Minor

Trace

Element

Ca

Fe

Zn

75/$ - see front matter & 2008 Elsevier Inc. A

016/j.jfca.2008.05.001

esponding author. Tel.: +251111239466; fax:

ail address: bhagnan@chem.aau.edu.et (B.S. C

a b s t r a c t

Kocho and Bulla are starchy foods obtained from fermenting edible part of the leaf sheath and corm of

enset plant (Ensete ventricosum (Welw.), Cheesman). In the present study, the levels of selected metals

(K, Na, Ca, Mg, Fe, Zn, Cu, Mn, Ni, Cr, Co, Cd, and Pb) in Kocho and Bulla sampled from different markets

of Woliso (Oromiya region) and Welkite (SNNPRG) of Ethiopia were analyzed. Known weight of oven-

dried Kocho and Bulla samples were wet-digested using 2 mL of (69–72%) HNO3 and 2 mL of (70%)

HClO4 for 2 h at variable temperature (120–270 1C). The contents of the minerals in the digests were

analyzed using flame atomic absorption spectrometer. The following concentrations (mean795%

confidence limit) (mg/g) were recorded in Kocho and Bulla, respectively: K (3567716) and (79274);

Na (57573) and (42274); Ca (54177) and (41674); Mg (235710) and (7471); Fe (11475) and

(48.271.3); Zn (2970.6) and (19.270.7); Cu (3.8570.25) and (2.7770.17); Mn (9.3470.28)

and (2.9970.14); Ni (p5.6170.29) and (p4.070.2); Cr (5.7370.15) and (p5.3870.22); Co

(5.870.14) and (5.4570.27). The toxic metals Cd and Pb were not detected in both types of foodstuffs.

The concentration of K was highest followed by Na, Ca, and Mg in both foodstuffs. From trace elements

analyzed, Zn was found to be highest next to Fe. Generally, Kocho contained higher concentration

compared to Bulla for the majority of the mineral nutrients determined. In general, Kocho and Bulla are

rich in Ca and Zn compared to other similar foodstuffs and contains comparable concentration of Cu, Fe,

and Mn. Besides Kocho and Bulla are free of heavy metal (Cd and Pb) contaminations compared to others.

& 2008 Elsevier Inc. All rights reserved.

1. Introduction

Humans require a suite of mineral elements in varyingamounts for proper growth, health maintenance, and generalwell-being (National Research Council (US) and Food andNutrition Board, 1989; World Health Organization (WHO) andFood and Agriculture Organization of the United Nations (FAO),1998). Plant foods can make a significant contribution to dailymineral needs at all stages of the life cycle (Dwyer, 1994).

Root and tuber crops are widely cultivated in southernEthiopia, which are supporting a considerable portion of thecountry’s population as source of food. Prominent among theseare: potato (Solanum tuberosum L.), sweet potato (Ipomoea batatas

L.), enset (Ensete ventricosum (Welw.), Cheesman), godere (Cola-

casia esculanta L.), yams (Dioscorea spp.), Ethiopian dinch (Coleus

parviflorus), koteharrie (Diaspora bulbiferous), and anchote (Cocci-

ll rights reserved.

+251111239470.

handravanshi).

nia abyssinica). Among these, enset, anchote, and some yams areendemic to Ethiopia (Addis, 2005).

Enset (E. ventricosum (Welw.), Cheesman) belongs to the familyMusaceae and the genus Ensete (Sanders, 2006; Brand et al.,1997). Enset is one of the few indigenous crops used for foodproduction and is important for about a fifth of the population ofEthiopia, mainly in the southern parts of the country (Bezuneh,1984; Addis, 2005; Brand et al., 1997; Negash et al., 2002; Tsegayeand Struik, 2002).

The major foods obtained from enset are Kocho, Bulla, andAmicho. Kocho is the bulk of the fermented starch obtained fromthe mixture of the decorticated (scraped) leaf sheaths and thegrated corm (underground stem base) whereas Bulla is the smallamount of water-insoluble starchy product that may be separatedfrom Kocho during processing by squeezing and decanting theliquid. Amicho is the fleshy inner portion of the enset corm, whichmay be cooked and eaten separately, tasting similar to potato(Pankhurst, 1996; Brand et al., 1997; Tsegaye and Struik, 2001;Pijls et al., 2006; Shank and Chernet, 1996).

Few authors determined the nutritional contents of Kocho andBulla. As reported by Agren and Gibbson (1968), the main feature

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M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552546

of enset foods is their high energy values (1410–1950 kJ/100 g drymatter of Kocho, 1580–1850 kJ/100 g dry matter of Bulla), derivedalmost entirely from carbohydrate. Fresh Kocho contains 47–62 gmoisture per 100 g. Per 100 g dry matter the approximatecomposition of Kocho is: protein 1.1–2.8 g, fat 0.2–0.5 g, carbohy-drates 95–98 g, fibre 2.3–6.2 g, ash 1.7 g, Ca 60 mg, P 68 mg, Fe7 mg, thiamine 0.06 mg, riboflavin 0.08 mg, and niacin 0.6 mg. Themoisture content of Bulla ranges from 44 to 55 g per 100 g freshmaterial. Per 100 g dry matter the approximate composition ofBulla is: protein 0.4–0.8 g, fat 0.2–0.4 g, carbohydrates 93–98 g,fiber 0.6–0.8 g, ash 0.2 g, Ca 91 mg, P 44 mg, Fe 5.8 mg, thiamine0.02 mg, and niacin 0.2 mg.

Pijls et al. (2006) reported that Bulla is more energy rich(850 kJ/100 g) than Kocho (650 kJ/100 g). All the foods have lowprotein content (0.4–2.2 g/100 g) and no vitamin A. Abebe et al.(2007) reported the mineral concentration of some of theelements (Fe, Zn, and Ca) in Bulla and Kocho sampled fromSidama Zone, southern part of Ethiopia.

However, information on the contents of major, minor andtrace elements in the processed food products of enset are scarcein the literature. Therefore, the purpose of this study is todetermine the major, minor and trace elements in processedcommercially available enset food products (Bulla and Kocho) andto compare the result with other similar food types. Furthermore,the findings of this study will provide adequate information onthe distribution of major, minor and trace metals and it willensure the dietary safety of the individuals in the region in termsof essential and/or non-essential elements.

Therefore, in this study the levels of 13 elements (K, Na, Ca, Mg,Fe, Zn, Cu, Mn, Ni, Cr, Co, Cd, and Pb) in the processed enset foods(Kocho and Bulla) collected from the southwestern part ofEthiopia were determined.

2. Experimental

2.1. Equipment and reagents

2.1.1. Equipments

A drying oven (DIGITHEAT, J.P. SELECTA, S.a, Spain), a blendingdevice (Moulinex, France), a Kjeldahl apparatus, and a refrigerator(Hitachi, Tokyo, Japan) were used. A BUCK SCIENTIFIC MODEL210 VGP (East Norwalk, USA) atomic absorption spectrophot-ometer was used for the analysis of metals (K, Na, Ca, Mg, Fe, Zn,Cu, Mn, Ni, Cr, Co, Cd, and Pb) using air–C2H2 flame. Na and K weredetermined in the emission mode of the spectrometer.

2.1.2. Reagents and chemicals

All the reagents used were of analytical grade. 69–72% HNO3

(Spectrosol, BDH, UK) and 70% HClO4 (Aldrich, A.C.S. Reagent,Germany) were used for digestion of Bulla and Kocho samples.Lanthanum nitrate hydrate (98%, Aldrich, USA) was used to avoidrefractory interference (for realizing calcium and magnesiumfrom their phosphates). Stock standard solutions containing1000 mg/L, in 2% HNO3, of the metals K, Na, Ca, Mg, Fe, Zn, Cu,Mn, Ni, Cr, Co, Cd, and Pb (BUCK SCIENTIFIC PURO-GRAPHICTM)were used for preparation of calibration standards and in thespiking experiments. Distilled and deionized water was usedthroughout the experiment for sample preparation, dilution, andrinsing the apparatus prior to the analysis.

2.2. Prevention of contamination

To minimize the risk of contamination, all glassware used forthe analytical methods was washed with distilled–deionized

water followed by acid-wash, and sterile disposable powder-freeplastic gloves were worn when handling the foodstuffs during thesampling and analyses stages. The digested solutions were kept inthe refrigerator until analysis.

2.3. Description of sampling sites

For the collection of Kocho and Bulla, Woliso (Oromiya region,Ethiopia) and Wolkite (Southern Nation Nationality PeopleRegional Government, SNNPRG, Ethiopia) were chosen. The reasonfor selection of these places was based on two things. First,the mineral contents of unprocessed edible part of enset(E. ventricosum) from Woliso and Wolkite was determinedand reported by Debebe (2006). Therefore, in order to relate andcompare the mineral contents of unprocessed edible part with theprocessed one, these places were selected. Second, commerciallyavailable Bulla in urban markets particularly Addis Ababa(Ethiopia) markets may not be pure, meaning that it may bemixed with wheat flour. So, in order to have precise and accurateinformation, the samples were collected from the source (produc-tion area) (Woliso and Wolkite) where the Kocho and Bullasamples are sold without mixing with wheat flour.

The two areas are located within the same latitude andlongitude. They are found under comparable climatic condition.These places are some of the major producers of Kocho and Bullaand are major exporters to the Capital City, Addis Ababa, withpure (uncontaminated with flour) Bulla flour.

2.4. Collection and preparation of Kocho and Bulla samples

The squeezed out and ready to be cooked Kocho and driedBulla flour samples were collected from Woliso and Welkitemarkets. To do this, 10 markets from each sampling sites wererandomly selected. Half-kilogram (500 g) of Kocho and Bulla fromeach market area was collected. From each 500 g, 200 g was taken,oven-dried at 70 1C for 64 h (Kocho) and 24 h (Bulla) (untilconstant weight) and grinded in a blender to homogenize andreduce the size of some caked Kocho particles during drying.Finally, four bulk samples (two for Kocho and two for Bulla), i.e.,one bulk sample for each of the two food types from each of thetwo stated areas were prepared for the analysis by taking 20 gfrom each 200 g ground sample and mix thoroughly in a blenderto give homogeneous bulk sample. Three 0.5 g aliquots from eachof the two bulk samples for each food type were taken for thedigestion and analysis.

It should be noted that one bulk sample of each of Kocho andBulla from each of the two sampling areas were prepared andanalyzed because the geographical variation within the provinces(of smaller areas with similar latitude and longitude andcomparable climatic condition) was assumed to be insignificant.

2.5. Digestion of Kocho and Bulla samples

Applying the optimized procedure, 0.5 g of dried and homo-genized Kocho and Bulla samples were transferred into a 250 mLround bottomed flask. To this was added 4 mL of a mixture ofHNO3 (69–72%) and HCLO4 (70%) with a volume ratio of 1:1 andthe mixture was digested on a micro-Kjeldahl digestion apparatusby setting the temperature first to dial at 4 (120 1C) for 30 min andthen increased to dial 6 (180 1C) for the next 30 min and thenincreased to 9 (approximately 270 1C) for the remaining 1 h. Thedigested solution was allowed to cool for 10 min withoutdismantling the condenser from the flask and for 10 min afterremoving the condenser. To the cooled solution, 15 mL ofdistilled–deionized water was added to dissolve the precipitate

ARTICLE IN PRESS

Table 1Method detection limits for Kocho and Bulla samples (n ¼ 10)

Metal Wavelength

(nm)

Correlation coefficient

of calibration curves

MDL (mg/g)

K 766.5 0.9999 6

Na 589.0 0.9992 1

Ca 422.7 0.9999 6

Mg 285.2 0.9998 3

Cu 324.8 0.9999 2

Zn 213.9 0.9991 3

Mn 279.5 0.9996 1

Ni 341.5 0.9991 4

Fe 248.3 0.9995 5

Co 240.7 0.9998 5

Cr 357.9 0.9999 5

Cd 228.9 0.9999 2

Pb 283.3 0.9995 3

MDL, method detection limit.

Table 2Recovery test results for Bulla samples

Metal Concentration in

sample (mg/g)a

Amount added

(mg/g)

Concentration in

spiked sample

(mg/g)b

% Recoveryc

K 875 100 96877 92.675.4

Na 402 100 49574 93.176.2

Ca 446 100 55172.3 10573.2

Mg 89.5 20 10871.2 94.372.4

Cu 3.53 1.0 4.5070.11 96.877.3

Zn 44.3 20 63.171.77 94.177.9

M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552 547

formed on cooling and to minimize dissolution of filter paper bythe digest residue while filtering with whatmans, (110 mm;diameter), filter paper. The round bottom flask was rinsedsubsequently with 5 mL distilled–deionized water until the totalvolume reached around 45 mL. To this final solution, 1%lanthanum nitrate solution was added and the solution was filledto the mark (50 mL) with distilled–deionized water. Triplicatedigestions were carried out for each bulk sample. Ten blanksolutions were prepared following the same digestion procedureas the sample.

2.6. Recovery test

The efficiency of the optimized procedure was checked byadding known concentration of each metal in 0.5 g sample. Theprocedure was as follows: 50mg of Ca, K, and Na were spiked atonce in to 0.5 g of Bulla sample and the remaining metals (10 mg ofMg and Zn; 0.5mg of Cu; 15mg of Fe; and 0.25mg of Mn) werespiked at once in to another round bottomed flask containing 0.5 gof Bulla. Similarly, 0.5 mg of Co and Cr were spiked at one in a flaskcontaining 0.5 g of Bulla sample. For spiking Kocho sample, 250 mgof K, 0.4mg of Cr and 1mg of Co, and 0.5 mg of Cu were spiked fromstock solution of each metal in to a flask containing 0.5 g of Kochosample and the remaining metals (50 mg of Na, Ca, and Mg; 10 mgof Zn; 2.5 mg of Mn; and 25mg of Fe) were spiked at once in 0.5 g ofKocho and 0.5mg of Ni was spiked in another flask containing thesame amount of Kocho sample and the same digestion processwas followed. Each sample was analyzed for their respectivespiked metals by atomic absorption spectrophotometer. Eachrecovery test for both samples was performed in triplicates.

Mn 1.0 0.5 1.4970.07 96.779.8

Cr 5.38 1.0 6.3070.21 91.878.8

Fe 59.8 30 92.272.8 10877.9

Co 5.01 1.0 5.9270.13 91.075.6

a Average value of nine measurements (mg/g).b Values are mean7S.D. of triplicate readings of triplicate analyses.c Values are mean7S.D. of triplicate percentage recovery values of triplicate

analyses.

Table 3Recovery test results for Kocho samples

Metal Concentration

in sample (mg/

g)a

Amount added

(mg/g)

Concentration

in spiked

sample (mg/g)b

%

Recoveryc

K 4380 500 4843730 92.676.3

Na 462 100 55375 91.275.4

Ca 584 100 67876 93.674.1

Mg 290 100 38274 91.873.2

Cu 3.77 1.0 4.7270.2 94.678.3

Zn 32.1 20 50.770.4 93.171.4

Mn 8.58 5.0 14.270.4 96.777.2

Ni 5.61 1.0 6.5470.3 93.176.1

Fe 135 50 18475 97.274.5

Cr 6.42 0.8 7.1570.4 90.878.9

Co 6.1 2.0 7.9370.4 91.576.3

a Average value of nine measurements (mg/g).b Values are mean7S.D. of triplicate readings of triplicate analyses.c Values are mean7S.D. of triplicate percentage recovery values of triplicate

analyses.

3. Results and discussion

3.1. Optimization of digestion procedure of Kocho and Bulla samples

Debebe (2006) has optimized different conditions by varyingdigestion time, reagent volume, volume ratio of reagents, anddigestion temperature for the unprocessed edible part of esnet(E. ventricosum). Therefore, this procedure was used as a referenceto optimize different parameters such as reagent volume ratio,digestion time, and temperature by varying one parameter at atime for the digestion of Kocho and Bulla samples.

Finally, for a complete digestion of 0.5 g of the dry sample, 2 mLHNO3 (69–72%) and 2 mL HClO4 (70%) for a total of 2 h at variableinterval was selected as optimized procedure for the digestion ofboth Kocho and Bulla samples.

3.2. Instrument calibration and method detection limit

For the present study, replicate analyses for 10 blank sampleswere performed and the pooled standard deviation of the 10reagent blank was calculated. The detection limits were obtainedby multiplying the pooled standard deviation of the reagent blankby three. The wavelengths at which analysis was done, thecorrelation coefficients of the calibration curve for each of themetals and method detection limits of each metal are given inTable 1. The results clearly show that the calibration curves withgood correlation coefficients and lower method detection limitswere obtained during the analysis.

3.3. Evaluation of analytical method

In the absence of standard reference materials for Kocho andBulla, the validity of the optimized digestion procedure for Kocho

and Bulla were checked by carrying out with a lower level oftraceability, such as spiked samples. The results are presented inTables 2 and 3. The percentage recovery of metals in Kocho andBulla samples are between 91% and 108% (10079), which arewithin the acceptable range.

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3.4. Determination of major, minor and trace metals

Three aliquots of food sample were taken from each bulksample and the data on the different aliquots was combined(n ¼ 9) to give one mean value of the particular metal for oneparticular bulk food sample. Thus, even though it is not possible totell how much of the R.S.D. in the results (Tables 4 and 5) is from

Table 4Mean concentration (X7S.D., n ¼ 9, mg/g dry weight) and relative standard

deviation (% R.S.D.) of major, minor and trace elements in Kocho samples

Metal Woliso Kocho % R.S.D. Welkite Kocho % R.S.D.

K 4380720 0.46 2753722 1

Na 46273 0.65 68875 1

Ca 58476 1.0 498711 2

Mg 290714 4.8 180711 8

Cu 4.370.36 8.4 3.470.3 7.6

Zn 27.170.9 3.3 3170.8 2.5

Mn 8.5870.35 4.1 10.170.4 4.3

Co 6.170.25 4.1 5.570.1 2.2

Fe 13579 6.4 92.574.1 4.4

Cr 6.4270.34 5.3 5.9670.3 5.0

Ni ND (o4)a – 5.6170.38 6.7

Cd ND (o2)a – ND (o2)a –

Pb ND (o3)a – ND (o3)a –

a Concentration of the tested heavy metals were below the method detection

limit given in parenthesis.

Table 5Mean concentration (X7S.D., n ¼ 9, mg/g dry weight) and relative standard

deviation (% R.S.D.) of major, minor and trace elements in Bulla samples

Metal Woliso Bulla % R.S.D. Welkite Bulla % R.S.D.

K 87575 0.60 70875 1

Na 40276 1.5 44275 1

Ca 44673 0.67 38578 4

Mg 89.571.6 1.8 58.471.2 2.1

Cu 3.5370.3 8.5 2.0170.15 7.4

Zn 16.371.1 6.7 2270.7 3.1

Mn 1.070.11 11 4.9870.25 5.0

Co 5.0170.03 5.98 5.8970.67 11.4

Fe 59.872.1 3.6 36.571.33 3.6

Cr ND (o5)a – 5.3870.28 5.2

Ni ND (o4)a – ND (o4)a –

Cd ND (o2)a – ND (o2)a –

Pb ND (o3)a – ND (o3)a –

a Concentration of the tested heavy metals were below the method detection

limit given in parenthesis.

Table 6Comparison of levels of some elements with the available data in literature

Food type Elements (mg/g)

Zn Fe Ca Reference

Bulla 0.7–0.9 36–65 400–470 Abebe et al. (2007)

– 58 910 Agren and Gibbson (1968)

11–77 440–650 Wu Leung et al. (1968)

16.3–22 36.5–59.8 385–446 Present study

Kocho 3.2–7.2 36–101 1400–2260 Abebe et al. (2007)

– 70 600 Agren and Gibbson (1968)

6 37 320 Amede et al. (2004)

– 53 1200 Wu Leung et al. (1968)

7.1–31 92.5–135 498–584 Present study

sample inhomogeneity and how much results from analyticalerror the over all error (resulting from sample inhomogeneity andfrom analytical error) is within the acceptable range (R.S.D.o10%).

Table 6 presents the range of some metals reported in theliterature.

3.5. Distribution pattern of metals in the processed enset foods

Plants accumulate minerals essential for their growth from theenvironment and can also accumulate metals such as Cd, Co, Ag,and Na, which have no known direct benefit to the plant (Raskinet al., 1994). As reported by Debebe (2006), enset plant is knownto accumulate essential and non-essential nutrients.

To prepare Bulla and Kocho, the corm and the false stem ofenset, is grated or decorticated, mixed, and the watery partsqueezed out to get Bulla (liquid portion) and the solid materialgives Kocho. Then these enset products allowed fermenting for aset period of time. Enset food processing follows a number ofphysicochemical processes which depends upon the weathercondition (i.e., the temperature and amount of fermented Kochoadded as a yeast), harvesting season meaning that age of the plantand variety or clone of the species (Brand et al., 1997; Tsegaye andStruik, 2001; Agricultural and Development Economics Division(ESA) Food and Agriculture Organization of the United Nations(FAO), 2003).

Therefore, the major, minor and trace metals in Kocho andBulla and their quality will be affected by different factors.Physical and chemical properties of the soil, application of natural(manure) and artificial fertilizers, storage and processing of Kochoand Bulla, age of harvested (processed) enset plant, climaticcondition of the region, and other factors are the maincontributors for the mineral contents of Kocho and Bulla.

3.5.1. Concentration of metals in Kocho

As can be seen from Tables 4 and 5, there is a variation inconcentration of macro- and micronutrients within the processedfood types (Bulla and Kocho) and there is slight variation in somemetals along with geographical location. The concentration oftoxic heavy metals, Cd and Pb, in the Kocho were below thedetection limit. The pattern of concentration of elements in Kochocollected from Woliso was decreased as K4Ca4Na4Mg4Fe4Zn4Mn4Cr4Co4Cu.

Likewise, the pattern of concentration of elements in Kochocollected from Welkite was decreased as K4Na4Ca4Mg4Fe4Zn4Mn4Cr4Ni4Co4Cu.

As can be seen from the data in Table 4, Kocho can be goodsource of major, minor and trace metals that are essential tohuman.

Kocho contains higher amount of K, followed by Na, Ca, andMg. The higher levels of K and Mg in the Kocho according toMarschner (1995) was due to the fact that nutrient elements suchas N, P, K, S, and Mg are highly mobile in the plant tissue andtrans-located from old plant tissue to new plant tissue.

From observed result, Kocho is known to contain higher Naconcentration next to K and Ca. As Grusak and Della Penna (1999)reported, Na and Cr are required by humans, but not by plants.Fortunately for humans, however, plants can acquire theseelements through non-specific influx processes using existingtransporters localized to their roots. In fact, a wide range of plant’snon-essential elements (both benign and detrimental) has beenmeasured in plant tissues, with concentrations sometimes reach-ing dramatic levels if soil availability is high.

The concentration of Fe and Zn were higher than the entiretrace metals in the samples from both sites where as Ni (inWoliso) and Cd and Pb (in both sites) were not detected in the

ARTICLE IN PRESS

0Na Ca Mg K

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Element

Con

cent

ratio

n (µ

g/g)

Woliso Bulla

Woliso Kocho

Welkite Bulla

Welkite Kocho

140

160 Woliso Bulla

Woliso Kocho

Welkite Bulla

M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552 549

sample. This may be due to low natural abundance in the soil, lowabsorption constant, and liable complexation. Of course, Cd andPb have no nutritional value for humans; their low concentrationis appreciated because of their potential toxicity.

It has been reported that Fe, Cu, and Zn are the main elementsthat plant could accumulate and be passed up the food chain.Therefore, the detection of Cu and the high concentration of Znfrom trace metals next to iron in Kocho may be because of the factthat these ions are readily transferred from the soil to plants, andaccumulate in the root and tuber of the false stem of enset plantand hence in Kocho.

Since the soil types of enset growing areas of Ethiopia aremoderately acidic to slightly basic with the pH ranges from 5.6 to7.3, the plant is expected to have a better accumulation ofmicronutrients like iron and zinc (Beyene, 1988).

As mentioned before, the nutritional value of Kocho has not yetbeen analyzed except for few metals. The mineral content ofCa, Zn, and Fe were analyzed and reported by different scholars(Table 6). Except for Zn, the concentrations of the other twometals lie within the range. The variation may be attributed fromdifferent reason. The previous results were conducted on Kochofrom Sidama (southern part of Ethiopia) and Areka, which is foundin Wolayta zone (southern part of Ethiopia). As mentioned above,the mineral concentration of Kocho is affected by differentreasons, of these, age of harvested enset plant, precaution takenduring processing, physical and chemical nature of the soil and itsmineral nutrients, etc. Therefore, either of the reasons may leadsuch variations. Second, some of the authors used dry ashingtechnique as sample decomposition method, which is known tohave a problem in analyte loss. Therefore, such discrepancy maylead variation in Zn concentration.

Except for few metals, the trends for metal accumulation inKocho from the two stated areas were almost the same and forsome metals their concentrations were almost comparable. This isbecause these areas are located within the same geographicallocation. As a result of this, they will have comparable climaticconditions.

Cu Zn Mn Ni Fe Cr Co0

20

40

60

80

100

120

Element

Con

cent

ratio

n (µ

g/g)

Welkite Kocho

Fig. 1. Sitewise comparative study of average concentrations of (a) major and (b)

minor and trace metals in Bulla and Kocho from Woliso and Welkitie.

3.5.2. Concentration of metals in Bulla

As shown in Table 5, the trend of average concentration ofmetals in Bulla sampled from Woliso is K4Ca4Na4Mg4Fe4Zn4Co4Ni4Cu4Cr4Mn. Similarly, the pattern of theaverage concentration of metals in Bulla sampled from Welkiteis K4Na4Ca4Mg4Fe4Zn4Cr4Co4Mn4Cu. The concentra-tions of Cr (in Woliso Bulla), Ni, Cd, and Pb were below thedetection limit.

Except for Zn, the concentrations of Fe and Ca found in theBulla samples in the present study are within the range and followthe same pattern with the reported values. The possible reasonsfor deviation in Zn concentration are described under Section3.5.1. In this finding, the concentration patterns of the metals inBulla from both places follow the same pattern except for fewtrace metals.

Generally, the concentration of metals in Bulla from Woliso ishigher than Bulla from Welkite except for the elements Na, Zn,Mn, and Cr. But the variation is not that much significant for themajority of the elements identified. The reason is alreadymentioned under Section 3.5.1.

3.5.3. Correlations among levels of metals in Kocho and Bulla

3.5.3.1. Macroelements. The concentrations of Ca, Mg, K, and Na inKocho and Bulla collected from Woliso and Welkite are givenin Tables 4 and 5. The comparative results of these nutrients

in Kocho and Bulla within their respective site are also shown inFig. 1.

From Fig. 1, the concentration of the four metals in WolisoKocho is higher than Woliso Bulla. The same trend has beenobserved for Welkite Kocho and Bulla. From this, it is possible toconclude that the concentration of the major and minor metals inKocho is higher than in Bulla collected from both places. Whetherthe difference is significant or not, it has been discussed latter inthe section statistical analysis.

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Table 7Range of metal concentration in Kocho and Bulla from both studied areas

Metal Range of metal concentrations (mg/g) Metal Range of metal concentrations (mg/g)

Bulla Kocho Bulla Kocho

K 708–875 2753–4380 Fe 36.5–59.8 92.5–135

Na 402–442 462–688 Co 5.0–5.01 5.5–6.1

Ca 385–446 498–584 Cr p5.38 5.96–6.42

Mg 58.4–89.5 180–290 Ni ND (o4)a p5.61

Cu 2.01–3.53 3.4–4.3 Cd ND (o2)a ND (o2)a

Zn 22–44.3 31–32.1 Pb ND (o3)a ND (o3)a

Mn 1.0–4.98 8.58–10.13

a Concentration of the tested heavy metals were below the method detection limit given in parenthesis.

M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552550

The range of each metal in Kocho and Bulla excluding thesample site is shown in Table 7. Histogram in Fig. 1 clearly showsthat among the four samples Woliso Kocho contains the highestlevel of K. The concentration pattern of this metal in the foursamples could be arranged in decreasing order: Woliso Kocho4Welkite Kocho4Woliso Bulla4Welkite Bulla.

Except for Na, the same trend was followed for the Ca and Mg.But for Na the trend follows: Welkite Kocho4Woliso Kocho4Welkite Bulla4Woliso Bulla. However, Na is still higher in Kocho.As reported by Wu Leung et al. (1968) and Abebe et al. (2007), theconcentration of Ca is higher in Kocho than in Bulla.

As stated before, Bulla is obtained from squeezing anddecantation of the watery part during Kocho processing. There-fore, only small amount of water-soluble species of these metalswill pass in to Bulla and the majority of the metal ions will remainin the bulk of the decorticated and grated false stem and corm.Therefore, the pattern of metals in Kocho and Bulla follows thesame trend irrespective of the sampling site.

Kocho has relatively higher metal concentrations than Bulla.The comparative results are presented in Fig. 1. For most of themetals, Woliso Kocho has relatively higher metal concentrationand followed by Welkite Kocho and Woliso Bulla; while WelkiteBulla has the lowest metal concentration for the majority of themajor, minor and trace metals.

In both Kocho and Bulla, the trend for most metals is the same.The concentration of Fe is higher in all the four samples followedby Zn. The trend for Fe is: Woliso Kocho4Welkite Kocho4WolisoBulla4Welkite Bulla. For zinc, the trend is reversed meaning thatWelkite Kocho has higher amount of Zn followed by Woliso Kochoand Welkite Bulla followed by Woliso Bulla.

For Mn, the trend is similar to that of Zn; whereas Co, Cu, andCr followed the Fe trend except the concentration of Co and Cr inWelkite Kocho and Bulla is comparable. Similarly, Pb and Cd werenot detected in all the samples. Ni was below the detection limitexcept in Welkite Kocho.

The concentration of Fe and Zn was analyzed and reported byAbebe et al. (2007) and Amede et al. (2004), and the trends ofthese metals are similar to the present study, i.e., Kocho containshigher amount of these metals compared to Bulla. The reason forthe higher concentration of these metals in Kocho is alreadymentioned in the preceding sections.

3.5.4. Comparison of minerals in enset foods and cereal flours

In those areas where enset is a staple and co-staple food,people prepare meal from Kocho or Bulla only. But some timesthey use mixture of either of the following: Kocho with flour(maize or wheat flour), Bulla with wheat flour, and Bulla withKocho (Brand et al., 1997). Depending upon the individual interest,up to 30% of wheat flour can be mixed with the starchy enset food,

Bulla. Mixture of Kocho with flour is not that much common inurban areas but some individuals mix around 10% flour in Kochoand prepare different types of meals. Therefore, comparison of themineral contents of enset food with cereal flours is crucial so as toknow the dietary habits of those individuals who rely on enset asa staple and co-staple food.

Many authors reported the concentration of selected metals incereal grain and cereal flours, which are grown in different partsof the world including Ethiopia. Abebe et al. (2007), Wojcie-chowska-Mazurek et al. (1996), Chaven and Kadam (1989), andSager and Hoesch (2005) are some of them who reported certainselected mineral nutrients in the four major food types (maize,barley, Tef, and wheat). Table 8 summarizes the comparativeresults of selected metal concentrations for which the data areavailable in the literature. From the table, it is possible to see thatthe concentration range of some metals is higher in Kocho andBulla as compared to some cereal flours. The concentration rangeof Ca in Kocho and Bulla is as good as with barley flour and wheatflour. As compared to ‘‘Keyi Tef’’ flour from Ethiopia, Kocho andBulla contains lesser amount of this mineral; whereas maize flourcontains least amount of this mineral.

The trend for Mn becomes, wheat flour4barley4Kocho4Bul-la4Maize. ‘‘Keyi Tef’’ contains the highest amount of Fe followedby Kocho; while Bulla, whole wheat, maize, and barley white flourcontains comparable Fe concentration range. White wheatcontains the least Fe concentration range.

Pb and Cd have been detected in some places in cereal floursbut their concentration was very small and not detected in Kochoand Bulla. The concentration range of Zn and Cu is almostcomparable in all the food types mentioned before except forwhite wheat flour, which contains smaller concentration of Zn.

Even though the mineral contents of plant foods are affectedby different factors, it is possible to conclude something fromresults shown in Table 8. Kocho and Bulla are rich in Ca and Zn andcontain comparable concentration of Cu, Fe, and Mn. Besides this,Kocho and Bulla are free of heavy metal contaminations likeothers do.

3.6. Statistical analysis

Analysis of variance (ANOVA) is used to test hypothesis aboutdifferences between two or more mean values. For the presentstudy, the significance of variation within sample and betweensamples has been studied using one-way ANOVA (Miller andMiller, 2000).

No significant difference (po0.05) at 95% confidence intervalwas observed in Na concentration between Woliso Bulla andWoliso Kocho, Woliso Bulla and Welkite Bulla, and Welkite Bullaand Welkite Kocho. However, a significant difference (po0.05) in

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Table 8Comparison of selected metal concentrations (mg/100 g, dry mass) in Kocho and Bulla with some reported values in barley, wheat, maize and Tef

Food type Ca (mg/100 g) Mn (mg/100 g) Cu (mg/100 g) Fe (mg/100 g) Reference

Barley, white flour 45.0 NR NR 8.4 Abebe et al. (2007)

39.5–42.1 0.9–1.5 0.28–0.5 3.1–3.8 Sager and Hoesch (2005)

Red Tef, whole grain 155.0 NR NR 4150.0 Abebe et al. (2007)

Maize, white four 12.0 NR NR 4.9 Abebe et al. (2007)

1.3–7.6 0.36–0.70 0.06–0.26 1.47–2.7 Sager and Hoesch (2005)

Whole wheat NR 4.6 0.5 4.3 Chaven and Kadam (1989)

41.4–44.4 2.41–4.6 0.32–0.62 1.9–4.1 Sager and Hoesch (2005)

White wheat flour NR 0.7 0.2 1.1 Chaven and Kadam (1989)

Whole cereal flour NR NR o2 NR Wojciechowska-Mazurek et al. (1996)

Kochoa 49.8–58.4 0.86–1.01 0.29–0.38 9.25–3.49 Present study

Bullaa 38.5–44.6 0.10–0.50 0.20–0.35 3.65–0.98 Present study

Zn (mg/100 g) Pb (mg/100 g) Cd (mg/100 g)

Barley, white flour 3.57 NR NR Abebe et al. (2007)

1.47–2.17 NR NR Sager and Hoesch (2005)

Red Tef, whole grain 4.0 NR NR Abebe et al. (2007)

Maize, white four 2.15 NR NR Abebe et al. (2007)

1.28–1.41 NR NR Sager and Hoesch (2005)

Whole wheat 3.5 NR NR Chaven and Kadam (1989)

1.81–3.4 NR NR Sager and Hoesch (2005)

White wheat flour 0.8 NR NR Chaven and Kadam (1989)

Whole cereal flour 1.9–4.1 1.3–6.0 0.5–8.0 Wojciechowska-Mazurek et al. (1996)

Kochoa 3.1–3.21 ND ND Present study

Bullaa 2.2–4.43 ND ND Present study

NR, not reported; ND, not detected.a The range includes sample from Woliso and Welkite.

M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552 551

mean concentration of Na at 95% confidence level was observedbetween Woliso Bulla and Welkite Kocho, Woliso Kocho andWelkite Kocho, and Welkite Kocho and Woliso Bulla. This resultreveals that there is inter-site variability in mean concentration ofNa, in Kocho food and there is absence of inter-site variability ofNa in Bulla food.

Similarly, there is a significant difference (po0.05) in meanconcentrations of K, Ca, and Ni at 95% confidence interval betweenfood types, i.e., between Bulla samples, Kocho samples andbetween Kocho and Bulla samples except for Ca, and Ni for whichthere were lack of a significant difference between Woliso Bullaand Woliso Kocho and Woliso Bulla and Welkite Bulla. Likewise,absence of significant difference (po0.05) in mean concentrationof Cu and Co at 95% confidence interval in all food types sampledfrom Woliso and Welikite were observed.

For Mn and Zn, the difference in their mean concentrationbetween Woliso Bulla and Woliso Kocho, Woliso Bulla and WelkiteBulla, and Woliso Bulla and Welkite Kocho were significant(po0.05) at 95% confidence interval; whereas absence ofsignificant difference (po0.05) were observed for these metalsfor the remaining pair of analysis.

Woliso Bulla and Welkite Kocho and Welkite Kocho and WolisoBulla showed a significant difference in the mean concentration ofFe and Mg and insignificant difference for the remaining pairwiseanalysis for Fe concentration. Similarly, mean concentration of Mgshowed a significant difference when compared with Woliso Bullaand Woliso Kocho and Woliso Bulla and Welkite Bulla.

Absence of significant difference in some mineral nutrients inboth samples from Welkite and Woliso may indicate that since

these area are under the same geographical location andshare common climatic conditions. Similarly, presence of sig-nificant difference in concentration for some minerals indicatesthat either of the studied area contains higher concentration ofmineral nutrient in the soil or well-aged plant have beenharvested and well-managed precautions have been followedduring processing.

4. Conclusion

In this study, commercially available Kocho and Bulla wereanalyzed for their contents of K, Na, Ca, Mg, Fe, Zn, Cu, Mn, Ni, Cr,Co, Cd, and Pb.

The optimized wet digestion method for Kocho and Bullaanalysis was found to be efficient for the majority of the mineralsand it was evaluated through the recovery experiment and a goodpercentage recovery was obtained (100710) for the majority ofthe minerals determined.

The results of the analysis showed that both Kocho and Bullacontains appropriate concentration of major, minor and tracemetals. For the majority of the mineral nutrients, their concentra-tion was higher in Kocho compared to Bulla and for the majority ofthe elements Woliso Kocho and Bulla contained the higherconcentration. The ANOVA results suggest that there weresignificant variation in the level of some elements between thefoodstuffs within the sampling site and between the samplingsites, which could be attributed to different factors such as ageand clone (varity) of enset species processed, different precaution

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M. Atlabachew, B.S. Chandravanshi / Journal of Food Composition and Analysis 21 (2008) 545–552552

taken during processing, fermentation and storage conditions andlength of fermentation. For some elements, the variations wereinsignificant, which could be attributed to having similar climaticconditions of the sampling sites because they are located withinthe same geographical location.

Pb and Cd were not detected in both food staffs from bothplaces. Likewise, Ni was not detected in all foodstuffs except inWelkite Kocho. The results revealed that Kocho and Bullaaccumulate Ca and Na next to K. From trace elements analyzed,Fe concentration was found highest followed by Zn. Except for Zn,these results were also comparable with reported literature valuesanalyzed from other parts of the country.

For some metals, their concentration was compared withcereal flours. For some of the elements, extracted cereal flourscontains lower concentration range; while whole grain containshigher concentration range compared to Kocho and Bulla. Forsome metals, their concentration range was comparable withKocho and Bulla; while others are lower in their concentration inKocho and Bulla. Generally speaking, mineral contents of Kochoand Bulla satisfy the individuals’ need equally with cereal flours.

Acknowledgments

The authors express their gratitude to the Department ofChemistry, Addis Ababa University, Ethiopia, for providing thelaboratory facilities. Minaleshewa Atlabachew is thankful toDepartment of Chemistry, Bahir Dar University, Ethiopia, forsponsoring his study.

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