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African Crop Science Journal, Vol. 8. No. 2, pp. 195-201 SHORT COMMUNICATION Chemical composition of Ricinodendron heudelotii: an indigenous fruit tree in southern Cameroon T. Tiki Manga, J. M. Fondoun, J. Kengue and C. Thiengang1 (Received 25 May, 1998; accepted 4 February, 1999) Code Number: CS00021 INTRODUCTION In Africa, tropical fruits provide essential dietary compliments. Nutritionists advise a daily intake of at least 100 g of fruit and as much variety as the season permits (Samson, 1986). In parts of East, Central and West Africa, banana, plantains and tuber crops are important parts of the diet and the daily consumption may exceed 2 kg per head. But these cannot provide all the mineral elements necessary for good human health (Jardin, 1967). Some native fruits are gathered in the forests such as durian in Malaysia and Indonesia, Sapucaia in the Guyanas and Brazil, and several palm fruits in South and Central America (de Foresta and Michon, 1994). Like vegetables, fruits provide vitamins, energy and minerals essential for human health (Saka and Msonthi, 1994). In Cameroon, wild fruit trees play an important role in the rural people’s life (Duckworth, 1966; Vivien and Faure, 1985; Campbell, 1987) as they provide substantial income to their economy (Ndoye, 1995). But it is not known to what extent these available wild fruits contribute to human dietary needs. In a farmers’ priority survey on local multipurpose trees in southern Cameroon (Mollet et al., 1995), Ricinodendron heudelotii (Bail.) was identified as one of the most important fruit species. A recent paper (Fondoun et al., 1999) documented the ethnobotany and uses of this species. This study was undertaken to provide information on chemical composition of the edible portions of the fruits. MATERIALS AND METHODS Fruit collection and fruit processing. Mature fresh fruits of R. heudelotii trees were collected from six different locations in southern Cameroon (Fig. 1). Fruit samples were collected at 40-50 km intervals along the main road network from home gardens, food crop as well as cash crop fields, bush fallow and primary forest lands. At each sampling location, 100 fruits were randomly collected under a tree chosen by farmers. A total number of forty seven accessions or tree provenances were sampled from 47 villages within the six provinces of the region. Geographical characteristics of the main city in the six regions from where collections were made are shown in Table 1.
The fruits collected from each tree provenance were kept for two weeks under ambient temperature to allow mesocarp decomposition and for seed extraction. The seeds were then boiled for 45 minutes and crushed. Kernels (the edible parts) were extracted from the seed and homogenised using a mortar and pestle. Chemical analysis. Analar grade chemicals were used for all chemical analyses (Saka and Msonthi, 1994). Crude protein, total ash, crude fibre and total sugar were analysed using Wolff’s methodology (Wolff, 1968). Total ash was determined by dry-ashing method after being oven-dried for 48 hours at 65oC. Nitrogen was determined by Kjeldahl method and multiplied by 6.25 to obtain crude protein. Crude fat was determined using dilute acid hydrolysis and hexane soxhlet extraction technique. Crude fibre was analysed by solubilisation in sulphuric acid 0.255 N and alkaline hydrolysis method (Saka and Msonthi, 1994). Protein, fat and total sugar values were multiplied by 17, 37 and 16, respectively, and summed up to obtain the calorific values (Osborne and Voogt, 1978). Total sugar was extracted by hydrolysis in hydrochloric acid (HCl 4N) and by solubilisation in 50% ethanol. No analysis was done for minerals. Fatty acid spectrum was determined by gas chromatographic technique on 100 g dry matter basis for two provenances, FTKC 27 and FTKC 32 following the procedures of Christophersen and Glass (1969) and Christie (1989). A Principal Component Factorial Analysis was done to assess the differences or similarities of the chemical composition of the provenances. RESULTS AND DISCUSSION Table 2 shows the chemical composition of the 47 provenances of edible R. heudelotii kernels, and Figure 2 presents the similarity or difference distribution of the chemical composition of the provenances. Regardless of the chemical component considered FTKC 27 and 32 had the highest and lowest values, respectively.
Fat content. Crude fat varied from 49.3 to 63.5% for FTKC 32 and 13, respectively, showing a large difference between the provenances, probably due to environmental effects (Ladipo et al., 1996). Similar results were obtained on samples from Ebolowa (Tchiegang et al., 1997) and Madagascar (Heim et al., 1919). Pieraerts (1917) found up to 67.1% crude fat on Ricinodendron samples from Congo. R. heudelotii therefore contains higher crude fat than classical oily plants, such as cotton (35 - 40 %) and soybeans (15 -25%) (Cheftel et al., 1977). Crude protein. The highest and lowest protein contents were obtained from provenances FTKC 27 (65.2%) and FTKC 32 (49.9%), respectively. Most provenances had more than 50% crude protein, revealing that Ricinodendron kernels have high protein contents. Baumer (1995) found alkaloid traces in Ricinodendron kernels with nitrogen component that probably accounts for the high level of crude protein. Total sugar. Similar incremental difference was observed as for crude protein between provenance FTKC 27 and FTKC 32, which yielded the highest (6.4%) and the lowest (4.9%) total sugar, respectively. Compared to soybeans (15%) and cotton (10%)[Cheftel and Cheftel, 1977], R. heudelotii has low total sugar content. Crude fibre and ash. The highest levels of ash and fibre were obtained in provenances FTKC 27, (17.7 and 9.4%) while the lowest levels were in FTKC 32 (14.4% for ash and 7.4 % for fibre). In Malawi, Saka and Msonthi (1994) found higher values of ash (11.0 % for Ximenia caffra) and fibre (45.3 % for Azanza garckeana) in two eastern African edible wild fruits. Fatty acid composition. Table 3 shows the fatty acid composition of two Ricinodendron provenance kernels, FTKC 27 and FTKC 32. Linoleic acid is the most common important fatty acid found in the cotyledons, with 60.3% for provenance FTKC 27 and 59.9% for FTKC32. Traces of oleic, stearic and palmitic acids were also found in the kernels.
Energy value. The energy values varied from 2,748 to 3,558 kJ 100 g-1 DM for provenances FTKC 32 and FTKC 27, respectively. These values are very high compared to those reported for food crops, i.e., 84 to 2,500 kJ 100g-1 DM (Duckworth, 1966). These high values are mainly derived from the fat content and crude protein. Unbalanced diet is generally the main cause of malnutrition in tropical Africa as a consequence of protein, iron and minerals deficiencies. Consumption of R. heudelotii kernels can help to reduce this deficiency. Moreover, as game meat and fish are becoming more scarce in the humid forests, fruits such as Irvingia gabonensis, Ricinodendron heudelotii and Coula edulis, could partially rectify the deficiency caused by lack of animal protein. Balick and Gershoff (1981) reported up to 2,558 calories and 286 g of fat in 1 kg of Jessenia bataua. The calorific value of Ricinodendron kernels is high but the sugar content is low, thus, the fruit can be recommended as a high-energy consumption material for diabetics. Our results also revealed that Ricinodendron heudelotii is an important source of protein. In general, the highest and lowest values of crude protein, fat, total carbohydrates, crude fibre and ash were recorded for provenances FTKC 27 and 32, respectively, indicating great variability in nutrient contents of R. heudelotii. This may be due to difference in soil type and climate as observed for fruit shapes and yields (Fondoun et al., 1999). The collected provenances should be considered as genetic "ideotypes" for futher improvement studies. CONCLUSION The species contains high level of crude oil that can be used for household consumption. Mineral composition of the species, however, needs to be determined. ACKNOWLEDGEMENTS The authors acknowledge the financial support provided by the Global Environmental Facilities (GEF) through UNDP office under the Systemwide Alternatives to Slash and Burn Project led by ICRAF. We are grateful to anonymous reviewers for their comments that greatly improved the manuscript. REFERENCE
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