Nutritional value of edible fruits of indigenous wild trees in Malawi

F o r e s t F~-nb-~jy and Management E LS EV I ER

Forest Ecologyand Management64 ( 1994) 245-248

Nutritional value of edible fruits of indigenous wild trees in Malawi J.D. Kalenga Saka*, J e r o m e D. M s o n t h i Departmentof Chemistry, ChancellorCollege, Universityof Malawi,P.O.Box 280, Zornba,Malawi

Abstract The edible portions of 16 edible wild fruits were analysed for moisture, protein, fat, crude fibre, ash and minerals (Ca, Mg, Fe, P, K, and Na). The total carbohydrate and energy contents were calculated. Trichilia emetica, Strychnos spinosa, Azanza garckeana, Ximenia caffra and Parinari curatellifolia gave the highest levels of protein (17.0%), fat (31.2%), fibre (45.3%), ash (11.2%) and carbohydrate (88.2%), respectively. The highest and lowest energy values were found for Strychnos spinosa ( 1923 kJ 100 g- t ) and Azanza garckeana (810 kJ 100 g- t ), respectively. Bauhinia thonningii afforded the highest dry matter content (91.6%). The highest contents of Ca, Mg, Fe, P, K and Na were found for Adansonia digitata ( 1156/zg g-t ), Syzigium guineense (2247/~g g-t), Syzigium guineense (758/zg g-t), Trichilia emetica (3164/tg g-S), Ximenia caffra ( 41 791/tg g- ' ) and Flacourtia indica (589/zg g- I ), respectively. Key words:Ediblewildfruit;Indigenousfruit tree;Nutrition

1. Introduction Like vegetables, fruits provide vitamins and minerals essential for the proper maintenance o f human health. In Malawi, indigenous fruits play an important role in people's diet (Williamson, 1975) and contribute to the economy of the rural community (Ngulube and Kananji, 1989). The identity, distribution and uses of edible wild fruits indigenous to tropical and subtropical Africa have been well documented (Jardin, 1967; Williamson, 1975; Food and Agriculture Organization (FAO), 1983; Campbell, 1987). However, information on their chemical composition is still limited (Wehmeyer, 1966; FAO, 1983; Saka et at., 1988). This study was therefore undertaken to obtain these important data for in*Correspondingauthor.

digenous fruits of Malawi. In this paper, the full chemical composition of 16 indigenous fruits is presented.

2. Materials and methods 2.1. Sampling Ripe fruits were collected from different parts of the country. Fruits o f t h e same type and common to the three regions o f Malawi were pooled and used as composite. For fruit species with an average weight of less than 50 8, 20 or 30 fruits (depending on amount and quality) were randomly selected and taken for processing. Otherwise five or ten fruits were used. About 1 kg of each fruit type was finally used for processing.

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2.2. Processing The fruits were peeled and the edible part (pulp) removed carefully from the seed. In the case of Trichilia emetica the seed is the edible portion. The edible parts were homogenised using a mortar and pestle. 2.3. Chemical analysis Analar grade chemicals and solvents were used. The edible parts were analysed for moisture, ash, crude fibre, fat, protein and mineral (Ca, P, Mg, Fe, K and Na) contents using standard procedures (Osborne and Voogt, 1978). Nitrogen was determined by the Kjeldahl method, and multiplied by a factor of 6.25 to give crude protein (Paul and Southgate, 1978). Moisture and ash were determined by the air-oven drying and dryashing methods, respectively. Crude fat was determined by using the dilute acid hydrolysis and hexane extraction technique while crude fibre was analysed by the acid and then alkaline hydrolysis method. Mineral elements were analysed on samples digested with a mixture of concentrated HNO3 and H2SO4. Phosphorus was estimated colorimetrically by the ammonium molybdate method. Ca, Mg and Fe were determined by the atomic absorption technique using a Perkin-Elmer 500 spectrophotometer, K and Na were analysed using a Coming 400 flame photometer. Samples for Ca analysis contained 0.5% LaCl3. The carbohydrate levels were calculated by difference and assumed 'available'. The calorific values were determined by multiplying the protein, fat and carbohydrate contents by 17, 37 and 16, respectively (Osborne and Voogt, 1978). 3. Results and discussion The chemical data for 16 edible wild fruits are presented in Table 1. The dry matter (DM) content of most of the indigenous fruits was generally low. Values varied greatly from 13 to 92%, but most values were in the range 13-30%. The energy values ranged from 810 to 1923 kJ

100 g-1 DM, the range falling within that reported for plant foods, i.e. 84-2500 kJ 100 g-t material (Duckworth, 1966). Strychnos sp: ~a gave the highest energy value while Azanza ~,rckeana had the lowest value; most values fell in the range 800-1600 kJ 100 g-~. The proximate data show that the energy values delve greatly from carbohydrate content. The fat contents for Strychnos spinosa and Trichilia emetica also contribute significantly. Ximenia caffra gave the highest ash and mineral contents, and Parinari curatellifolia the lowest; most fruits gave 3-5% ash. Syzigium guineense showed a similar total mineral level to Parinari curatellifolia. The highest and lowest protein contents were found for Trichilia emetica and Uapaca Idrkiana, respectively. Most fruits had < 5% protein on a DM basis. The African popular wild custard, Annona senegalensis had 15% protein. Plants are a cheap source of protein, hence Trichilia emetica and Annona senegalensis could be utilised for protein supplementation. The highest trade fat, crude fibre and total carbohydrate were obtained in Strychnos spinosa, Azarza garckeana and Parinari curatellifolia, respectively. The lowest levels for fat, fibre and carbohydrate were obtained in Vitex doniana, Ximenia caffra and Azanza garckeana, respectively. Generally, most fruits gave fat < 10%, fibre 5-10%, and total carbohydrate 60-90%. The proximate data seem to indicate that the fruits constitute an important source of energy while Annona senegalensis and Trichilia emetica are also useful sources of cheap plant protein. Potassium was the most abundant element, while Fe and Na were the least. The relative amounts of K and Na in plants appeared to be antagonistic. The levels of K varied from 8252 /~gg- 1in Syzigium guineense to 41 791 gg g- ~in Ximenia caffra. The range of K values showed that most fruits contained 10 000-30 000/~g g- !. The minor element, Na, ranged from 111 gg g- t in Tamarindus indica to 598 gg g- t in Flacourtia indica. No data on K and Na have been revorted for most fruits except Tamarindus indic,~. Duke and Weber ( 1981 ) reported 9299 gg K g-i and 50/~g Na g- ~, which are lower than ours. Phosphorus concentration obtained ranged

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247

Table 1 Chemicalcompositionof ediblewild fruits Fruits

Dry Ash Crude Fat Fibre Total Energy Mineral (/~gg-~) matter protein carbohydrate~ value (%) (%) (%) (%) (%) (%) (kIlOOg-') P Ca Mg

Adansonia digitata Annona senegalensis Azanza garckeana Bauhinia thonningii Flacourtia indica Parinari curatellifolia Strychnos innocua Strychnos spinosa Syzigium guineense Tamarindus indica Trichilia emetica Uapaca kirkiana Vangueria infausta Vitex doniana Ximenia eaffra Ziziphus mauritiana

86.8

5.0

29.8

5.0 15.1

3.1

4.3

8.3

Fe

K

Na

79.4

1480

450 1156 2090

58 28364 188

8.4 17.8 53.7

1426

1507 NDb 1762

84 21812 436 84 26190 202

52.8

6.3 12.0

1.1 45.3 35.2

810

1476

91.6

2.4

2.6

5.9 25.8 63.3

1276

979

983 1245 ND 22312 348 354 1380 734 24281 589

19.2

5.7

4.2

3.6

5.7

80.7

1290

1057

27.1

!.8

3.0

1.5

5.5

88.2

1517

339

21.8

3.7 11.5

6.0 17.9 61.0

1390

2106

22.1

4.1

5.4

31.2 17.6 42.1

1923

1081

19.8

7.1 10.1

4.0 30.3 48.5

1096

303

95 1453

129

830 103 10380 252

60 1633 149

60 28670 459

430 136 19683 253

227 2247 758

8252 152

73.1

3.4

4.1

1.6

5.9

85.0

1490

1081

171 1282

68 12269 111

58.1

4.5 17.0

22.9

8.1

47.5

1897

3164

ND 1129

43 13017 146

27.4

2.2

1.8

1.1

8.4

86.5

1456

555

33 1106 431 13682 365

26.5

3.4

5.7

2.6 10.2 78.1

1445

823

132 1811 283 18208 245

27.0

4.8

2.6

0.7

5.2

86.7

1459

2837

926

17.2

11.0

7.6

5.2

2.3

78.8

1506

1674

29

459 366 41791 198

700

93 21511 278

14.8

10.1

4.1

9.5

3.4

73.0

1588

2162

135

507 ND 17318 426

Valuesare mean of three determinationsand based on dry matter (dry matter itselfon fresh weightbasis). aCalculatedby difference. bND, value not determined. from 450/~g g-~ i n Adansonia digitata to 3164 /~g g - mfor Trichilia emetica. The value for Adansonia digitata is similar to that d e t e r m i n e d for Sudanese species by N o u r et al. ( 1980): 508/zg g-re. Values obtained for P content o f Trichilia emetica, Tamarindus indica a n d Vitex doniana are similar to those reported by FAO (1983) a n d Ishola et al. (1990). However, P content of Parinari curatellifolia reported by FAO (1983) is higher t h a n ours. The highest Ca level was recorded for Adan-

sonia digitata while Xime#ia caffra gave the lowest content. Most Ca values were less t h a n 500 /~g g-~. These values are lower t h a n those reported elsewhere: Parinari curatellifolia, 1145/zg g-~ (FAO, 1983); Adansonia digitata, 6500/zg g - ~ ( N o u r et al., 1980); Tamarii~dus indica, 4658 /~g g-~ (Ishola et al., 1990) a n d Vitex doniana, 1156/zg g - ' (FAO, 1983). This m a y b e bcca-,~s¢ o f differences i n soil type a n d climate. Magnesium, a congener o f Ca, varied between 459/zg g - mi n Ximenia caffra a n d 2247 #g g - ~ i n Syzig-

248

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ium guineense. Limited data on Mg are available in the literature, and the only available value reported by Ishola et al. (1990), 720 p.g g - i for Tamarindus indica, is lower than ours. A comparison of Ca and Mg data reveals that the former is less abundant. Iron, like Ca, is a major requirement in man's daily food intake, iron composition ranged from 43/~g g - I in Trichilia emetica to 758/~g g-~ in Syzigium guineense. The concentration of 14.0/~g Fe g - ~reported for Trichi. lia emetica by FAO (1983) is much lower than ours. Except for Parinari curatellifolia the Fe values we obtained are similar to those published elsewhere: Adansonia digitata, 86 p.g g (Nour et al., 1980); Tamarindus indica, 85/~g g - : (Ishola et al., 1990); Vitex doniana, 92 ~g g-~ (FAO, 1983). Iron deficiency is a major cause of malnutrition amongst children and pregnant mothers. Consumption of the fruits studied in this work would meet this deficiency. Flacourtia indica and Syzigium guineens,~ are the best sources o f this mineral: both fruits would supply > 5 nag Fe per I00 kJ of daily energy in. take. A man's daily requirement of iron is 0.088 mg per !00 kJ of energy intake (CTA/ECSA, 1987).

4. Conclusions

The results seem to indicate that Annona senegalensis and Trichilia emetica are important sources of plant proteins. The mineral data obtained should prove useful to the nutritionists in Malawi and worldwide. All the fruits are important sources of Fe, Flacourita indica and Syzigium guineense being the best sources. Adansonia digitata, Bauhinia thonningii and Vitex doniana are excellent sources of Ca and would satisfactorily meet m a t ' s daily requirement. In our attempts to promote consumption of these fruits, the production of fruit juices from Adansonia

digitata, Annona senegalensis, Flacourita indica, Trichilia emetica and Syzigium guineense is being studied in our laboratory.

5. Acknowledgements We wish to thank the Ministry of Agriculture for funding, Agriculture Development Divisions and the Department of Forestry for assistance during fruit collection and National Herbarium and Botanic Gardens of Malawi for plant identification. We also thank Linda Saka for typing this manuscript.

6. References Campbell, B.M., 1987. The use of wild fruits in Zimbabwe. Econ. Bet., 4h 375-385. CTA/ESCA, 1987. In: C.E. West (Editors), Food Composition Table for Eastern and Southern Africa, CTA, Wageningen, Netherlands. Duckworth, R.B., 1966. Contributions to human nutrition. In: Fruits and Vegetables.Pergamon Press, London, pp. 140-169. Duke, J.A. and Weber, J.K.P., 1981. Tamarindusindica L. In: Handbook of Legumes of World Economic Importance, Plenum, New York, pp. 228-230. Food and Agriculture O.-ganization, 1983. Food and Foodbearing Forest Spe,:ies: Examplesfrom Eastern Africa. FAO Forestry Paper 41/1. Food and AgricultureOrganization, Rome, 174 pp. Ishola, M.M., Agbaji, E.B. and Agbaji,A.S., 1990. A chemical study of Tamarindusindica (Tsamiya) fruits grown in Nigeria.J. Sci. Food Agric., 5h 141-143. Jardin, C., 1967.Fruits. In: Listof FoodsUsed in Africa.Food and AgricultureOrganization,Rome, pp. 118-170. Ngulube, M.R. and Kanarji, ~., 1989.SeedProblemsof Edible IndigenousFruits in Mala vi. ForestryResearchInstitute of Malawi, Zomba, 16 pp. Nour, A.A., Magboul,B.I.and Kheiri, N.H., 1980.Chemical composition of baobab fruit (Adansoniadigitata L.). Trop. Sci., 22: 383-388. Osborne, D.R. and Voogt, P., 1978. The Analysis of Nutrients in Foods.AcademicPress, London, 251 pp. P~d, A.A. and Southgate, D.A.T., 1978. In: McCance and Widdowson'sThe Cotapositionof Foods,4th edn. HMSO, London, 7 pp. Sal~, J.D.K., Msonthi, J.D. and Sambo, E.Y., 1988. Chemical composition of some edible wild fruits of Malawi. Proceedings of Workshop on Utilization and Exploitation of Indigenousand Often NeglectedPlants and Fruits of Eastern and Southern Africa, 21-27 August, Zomba, Malawi. Wehmeyer, A.S., 1966. The nutrient composition of some edible wild fruits in the Transvaal. S. Aft. Med. J., 40: 1102-1104.

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