Chapter 10
Nutritional Value of Fonio (Digitaria exilis) from Senegal Downloaded by DEAKIN UNIV on October 5, 2013 | http://pubs.acs.org Publication Date (Web): October 4, 2013 | doi: 10.1021/bk-2013-1127.ch010
Adolfina R. Koroch,*,1 H. Rodolfo Juliani,2 and James E. Simon2 1Science
Department, City University of New York, Borough of Manhattan Community College, 199 Chambers Street, New York, New York 10007 2New Use Agriculture and Natural Plant Products Program, School of Biological and Natural Resources, and the New Jersey Agricultural Experiment Station (NJAES), Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901-8520 *E-mail:
[email protected].
As food production is facing many challenges due to the increased population growth and climate change, indigenous and new plants and plant products that can provide nutritionally rich foods can contribute to food security, income generating activity and the preservation of genetic materials that otherwise could be marginalized and/or displaced by other crop commodities. Fonio (Digitaria exilis) is a West African annual millet characterized by tiny seeds that is prized by local communities and enjoyed regionally. The grass is well adapted to hot, dry climates and poor soils, and thus is able to grow in areas where many other cereals are not suited. In West Africa, fonio is used in traditional medicine but more as a source offood, which is used to prepare porridges, flours, alcoholic and non-alcoholic beverages. The objective of this work is to review the literature on fonio research and provide initial nutritional information of fonio from Senegal.
Introduction: Biology, Cultivation, and Uses In recent years, considerable attention has been given to crops that not only are healthy and inexpensive to produce but also that provides income-generating opportunities for local communities and small-scale/resource limited farmers. © 2013 American Chemical Society In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.
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Fonio (Digitaria exilis Staf, Poaceae or Gramineae) is also known as white fonio, acha, hungry rice, fonyo, fundi millet, fundi and hungry millet. The genus Digitaria originated in West Africa and comprises about 230 species in tropical, subtropical and warm-temperate regions (1, 2). For more than thousands of years West Africans have been cultivating and consuming fonio, a source of food for several millions of people. It has been estimated that about 300,000 ha are cultivated each year (1, 3). Fonio is widely cultivated and used from Senegal to Chad, in Fouta Djallon (Guinea), the BauchiPlateau in Nigeria and in northwest Benin (2, 4). Fonio is an annual grass that can reach up to 80 cm height. Its inflorescence is a finger shaped panicle with racemes of 5-12 cm length. The fruits are caryopsis (grain), tiny about 0.5-1 mm diameter, 0.75 – 2 mm length (5). Fonio species can tolerate a wide range of extremes conditions. For example, it is adapted to hot and dry climates (C4 annual herbaceous plants) and tolerates well poor, shallow, sandy, rocky or acidic soils which are unsuitable for other cereals (2, 3). It is highly adapted to drought and its cultivation is concentrated in areas with an average annual rainfall between 900 and 1000 mm (2). Moreover, fonio is not attacked by nematodes, even in soils where other plants are infected with Meloidogyne sp. No pathogens have yet been reported to attack fonio species (6). There is a large diversity within the species D. exilis and based on the morphology several varieties have been identified (2, 7). For instance, certain fonio varieties have short life cycle and can mature very fast producing grains 6 to 8 weeks after planted, while, other fonio species require over 23 weeks to mature. The growing of different varieties of fonio with different maturation time increases the chance of harvesting enough food for longer periods of time, particularly important in those areas where the growing conditions are unreliable (3). Within the Digitaria genus, fonio millets (small grain cereals) are the most important economic crop. One of the advantages of this small grain is the minimal processing, high nutritional value and less labor intensive (8). Fonio has been used for different purposes as religious and cultural crop, in traditional medicine and as a source of food. Fonio has an important religious and cultural value in weddings, baptism of newborn child (1). In traditional medicine fonio has been used for meteorism, constipation, as a diuretic, treat or eliminate blood clots, treat diarrhea, loss of appetite, dysentery, chickenpox, stomach ache and asthma (1, 9). In traditional foods, this grainis consumed as thin and thick porridges steam cooked with fish, meat legumes or vegetable and used to prepare snacks, alcoholic and non-alcoholic beverages (10, 11). More recently, research has been conducted to identify local alternatives to wheat flour, while seeking a highly nutritious substitute. Fonio grains can be ground into flour to produce flour bread (12), biscuits (13), sourdough bread (14, 15) and as a good substitute for semolina (3). Biscuits made of fonio supplemented with a mixture otherflours Fonio (wheat- soybean or cowpea) have high organoleptic characteristics, good digestibility and could serve as a vehicle to increase the intake of proteins and calories (16, 17). This small grain could also be used in multi-grain breads, as an ingredient in a mixed seed product. 128
In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.
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Fonio grains are digested efficiently by different ruminant livestock (1, 3) and because of the high amounts of phosphorus, potassium and trace minerals fonio grains are reliable materials for formulating poultry and pig feed to meet the nutrient specifications of such feed (18). According to the dietary guidance around the world the inclusion of whole grains in the diet is recommended because of their associations with increased health and reduced risk of chronic diseases. The consumption of whole grains has been linked to reduced risk of obesity, cardiovascular disease, hypertension, stroke and decreased risk of cancers of the upper gut (19). Currently, nutrition and lifestyle are main components to diabetes prevention, thus, choosing foods with low glycemic index has a small but clinically useful effect on medium term glycemic control in patients with diabetes (20). Fonio has such a low glycemic index and the recommended serving size would need to be carefully adhered to be effective (21). The objective of this work is to review the uses and nutritional value of fonio and report the proximal and elemental analysis of fonio grains from Senegal to identify new uses and applications.
Materials and Methods Fonio samples from Senegal (prepared and given by Peter Trenchard, USAID-Senegal to James E. Simon, Rutgers) were brought back into the USA, declared to APHIS and US Customs upon entry and then brought to Rutgers where the seeds were cleaned and visually inspected to remove any non-fonio seeds and debris. A sub-sample was prepared and submitted to the Agricultural Analytical Services Lab (Pennsylvania State University Soil and Plant Testing Laboratory) to determine the concentration 11 mineral elements including: phosphorus, potassium, calcium, magnesium, manganese, iron, copper, boron, aluminum, zinc and sodium using the dry ash method (22). The results were expressed for the macronutrients (phosphorus, potassium, calcium, magnesium) as g of element per 100 grams on a dry weight basis (g element/100 g DW). For the micronutrient (manganese, iron, copper, boron, aluminum, zinc and sodium), the results were expressed as mg of element per 100 grams on a dry weight basis (mg element/100 g DW). The analysis of moisture, ashes, carbohydrates, crude fat, protein, fiber and, calories were conducted at Miller Laboratories (1675 West 2750 South, Ogden UT 84401) following AOAC procedures (23).
Results and Discussions The moisture content of fonio was 9.5% (Table 1).This result agrees with previous findings of low seed moisture. The low moisture suggests that fonio loses water during storage and explains the longer shelf life of this grain (11). Moreover, because of the loss of moisture during storage, is less susceptible to attack by pests which could be particularly advantageous in tropical and subtropical regions (24). 129 In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.
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Total mineral content (ashes) was 4.3%, suggesting that the total mineral content is low. Fonio does not provide a significant amount of fats and carbohydrates though appears to be a very good source of proteins and excellent source of fiber (Table 1). Fonio showed higher levels of protein as compared with other grains (wheat, 13.6% and rye, 8%), the amount of fiber is much higher in fonio as compared with corn (7%), wheat (2%) and rye (1.6%), the mineral content of fonio was higher (6%) as compared with wheat and rye (less than 2%) (Table 1). Thus, fonio seems to be a rich source of protein and fiber, with low carbohydrate contents, 100g of fonio would provide a total of 347 calories, 21.5g are proteins, and 59.4g of fibers. The results showed that fonio is high in proteins, for example, 100 g could provide the daily dietary allowances for children 1-8 years. Starch obtained from fonio has been reported having similar structure and physicochemical properties to other conventional grains (8, 25). Fonio grains have proteins similar to white rice (26) but they are rich in the essential amino acids methionine and cysteine. High protein and fiber fonio bread could serve as a good alternative to wheat bread not only for diabetic patients but also for patients that are allergic to gluten (12).
Table 1. Proximate Analysis of Fonio (Digitaria exilis) from Senegal
*
Fonio
Corn(27, 28)
Wheat(29)
Rye(29)
Moisture (%, m/m)
9.5
10.5(27)
-
Ashes (%, m/m)
4.3
1.4(28)
1.5
1.72
Carbohydrates (%, m/m)
0.6
64(27)*
63.0
69
Crude fat (%, m/m)
0.34
4.3(28)
2.5
2.0
Protein (%, m/m)
21.5
7.7(27), 9.5(28)
13.6
7.98
Fiber (%, m/m)
59.4
9.5(2)
2.15
1.56
Calories (in 100g)
347
-
328
as total starch.
Because of the small size, fonio is minimally processed and thus consumed as a whole grain, which potentially could be an important source of nutraceuticals with different (more) heath benefits. Larger-scale processing that would be needed in any scale-up operation for fonio to become an internationally traded food grain may be challengingbecause of the small seed size and the difficulty in cleaning and separating seeds from the same/similar sized rocks and pebbles (Peter Trenchard, personal commun.). No reports have been published which answer this constraint. 130 In African Natural Plant Products Volume II: Discoveries and Challenges in Chemistry, Health, and Nutrition; Juliani, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.
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Table 2. Elemental Composition of Fonio Seeds (Digitaria exilis) Element
Fonio
Corn(30)
Wheat(30)
Rye(30)
Phosphorous (%)
0.06
0.31
0.4
0.38
Potassium (%)
0.04
0.33
0.58
0.52
Calcium (%)
0.01
0.03
0.06
0.07
Magnesium (%)
0.02
0.14
0.18
0.13
Manganese (mg/100 g)
0.3
0.6
5.5
7.5
Iron (mg/100 g)
2.1
2
6
9
Copper (mg/100 g)
0.1
0.2
0.8
0.9
Boro (mg/100 g)
0.1
-
-
-
Aluminum (mg/100 g)
1.7
-
-
-
Zinc (mg/100 g)
1.6
-
-
-
Sodium (mg/100 g)
1.4
-
-
-
In addition, compared to other African grains, fonio was found to contain high levels of calcium and phosphorous (24). Thus, this grain has been considered an excellent dietary complement to legumes, which are widely eaten in Africa (3, 31). However, the present study showed that the elemental composition of macroelements were low in Fonio (
