Teff (Eragrostis tef (Zucc.) Trotter) is a tropical cereal and its cultivation and usage as human food are largely confined to Ethiopia. Teff cultivation is increasing globally because of the nutritional merits of teff grain. It is consumed as whole grain often fermented as injera (a staple for majority of Ethiopians) and is suitable in the diet for celiac patients because it is free of allergenic gluten proteins. This article highlights the origin, cultivation, production, storage, anatomical structure, composition, grain components, physicochemical properties, and processing of teff grain. Teff grain potential as human food, grain production limitations, and recommendations for further research to improve teff crop and grain utilization are enumerated.
Anatomy, Cultivation, Eragrostis tef, Fermentation, Gluten-free, Grain, Injera, Milling, Nutritional value, Physicochemical properties, Protein, Starch, Storage
Teff crop description, origin, cultivation, and production.
Teff grain production constraints and progress of improvement.
Teff grain morphology, anatomical structure, composition, and physicochemical and functional properties of the major constituents of teff grain.
Teff grain nutrient merits, always consumed as whole-grain, gluten-free alternative food for celiac patients, high in mineral nutrients particularly in iron with well-balanced amino acids.
Processing of teff grain flour to injera (lactic acid bacteria and yeast-fermented, soft, spongy, sour, circular flatbread, staple food for majority of Ethiopians).
Prospect for future teff productivity improvement and utilization and diversification of teff products.
Achieve understanding on teff origin, description, grain production, and constraints associated to grain production systems.
Understand and apply the knowledge of teff grain morphology, anatomical structures, nutrient compositions, and grain component functionalities for processing into various food products such as for gluten-free and whole-grain foods.
Achieve understanding on teff injera processing stages, nature of fermentation involved, characteristic of injera for global consumers, and highlights on other traditional teff grain food products.
See teff as a traditional Ethiopian grain, strongly linked to national dietary culture, but with nutritional and sensory benefits that could lead to product development in new markets.
Teff (Eragrostis tef (Zucc.) Trotter), today generally written as ‘tef,’ is a tropical cereal. Teff cultivation and usage as human food are mostly confined to Ethiopia. This article highlights the origin, cultivation of the teff plant, and production and storage of the teff grain. Teff grain structure, anatomy, chemical composition, and physicochemical properties of the major chemical components are assessed and described. Teff milling, processing of injera (the staple food of the majority of Ethiopians, a fermented, pancake-like, soft, spongy, sour, circular flatbread), and other food products made from teff are described. Lastly, teff potential, grain production limitations, and recommendations for further research to improve the teff crop and grain utilization are suggested.
- Reproduced with permission from Improved varieties of tef [Eragrostis tef (Zucc.) Trotter] release of 1970-1995. Research Bulletin 1. Debre Zeit Agricultural Research Center Ethiopia. ; ; , 1995.
Teff (Eragrostis tef (Zucc.) Trotter) belongs to the family of Poaceae, subfamily Eragrostoideae, tribe Eragrosteae, and genus Eragrostis. About 350 species are known in the genus Eragrostis of which teff is the only cultivated species. Chloridoideae is used synonymously for Eragrostoideae of teff. Vernacular names in different parts of the world are as follows:
Tef, teff, and Williams love grass: English
Xaafi/tafi/taafi: Oromo (O)/Afar/Sodo; tafe-e: Had; and t'ef, teff, and taff: Amarinya (A) and Tigrinya (T) (Ethiopian languages)
Mil èthiopien: French
Chimanganga, ndzungula (Ch), and chidzanjala (Lo): Malawi
Teff is indigenous to Ethiopia. Ethiopia is also considered the leading world center for teff genetic diversity. As of 2013, the Ethiopian Institute of Biodiversity had conserved a total of 5169 accessions and 10000 teff genotypes for varietal improvement study and to reduce loss of genetic diversity. The exact details on teff domestication are unclear. However, teff is believed to have been first domesticated by the pre-Semitic inhabitants of Ethiopia between 4000 and 1000 BCE and is assumed to have originated in northeastern Africa. Even though teff is an allotetraploid plant, to date, its diploid putative ancestors are not exactly established. But, based on the morphological data and cytological evidence, the following species have been suggested as the ancestors and contributors to teff origin:
Eragrostis aethiopica, E. atrovirens, E. longifolia, E. macilenta, E. pilosa, and E. pseudo tef as ancestor species of teff
E. aethiopica, E. bicolor, E. cilianensis, E. curvula, E. pilosa, and E. mexicana as contributor species to the origin of teff
E. aethiopica, E. barrelieri, E. bicolor, E. cilianensis, E. heteromera, E. mexicana, E. minor, E. papposa, and E. pilosa as very closely related species to teff
E. aethiopica 2 ×; E. barrelieri 6 ×; E. cilianensis 2 ×, 4 ×, and 6 ×; E. mexicana 6 ×; E. minor 2 × and 4 ×; and E. pilosa 2 × based on cytological evidence as closely related species to teff
An attempted interspecific cross between teff and some wild Eragrostis species (E. curvula, E. cilianensis (4 ×), E. pilosa (4 ×), and E. minor) was not successful. However, it was recently reported that E. tef and E. pilosa can be crossed with fertile offspring, suggesting that E. pilosa or an ancestor closely related to E. pilosa is the most probable putative ancestor of teff.
Teff is one of the major cereals in Ethiopia with annual grain production estimated to be ca. 3.5 × 106 t (ca. 21% of the cereal grain production). In Idaho, the United States, some teff grain is produced for the health-food market and for injera making. In South Africa, teff is widely grown as a fodder crop during the summer-rainfall season. However, the production of a combination of grain and fodder varieties has been introduced only recently. In Australia, India, Kenya, and the United States, it is cultivated as a forage crop. Teff has been started to be cultivated in the Netherlands. Teff can adapt to a wide range of environments, that is, moisture stress, high rainfall, different soil types, and a wide range of altitudes from near sea level to over 3000 m. However, the best conditions are 1800–2100 m above sea level, a temperature range of 10–27 °C during the cultivation period, an annual rainfall of 750–850 mm, and rainfall of 450–550 mm during the growing season. Teff is known to have fewer disease and pest problems in the field as compared with maize, sorghum, wheat, and barley. However, the productivity is low. Lack of high-yielding cultivars, lodging, weeds, waterlogging, low moisture, low-fertility conditions, loss of grains on harvesting, threshing, and cleaning are major factors that contribute to the low grain yield. The yields of improved varieties under improved technologies (fertilizer, weed control, appropriate harvesting, and grain threshing) on farms are in the range of 1.4–2.7 tha− 1, and for some under research-managed farms, the yield is as high as 3.6 t ha− 1. Reduction of seeding rate from traditionally recommended 25–30 kgha− 1 to 2.5 kgha− 1 had recently demonstrated a substantial grain yield increase as compared with previous grain yield recorded. Because of adaption of some of the improved technologies by teff farmers, the average national yield in Ethiopia has increased annually from about 0.84 tha− 1 in 2003 to about 1.26 tha− 1 in 2011.
Teff grain is harvested when the vegetative and reproductive parts (pedicel, lemma, palea, and glumes) turn yellow or straw color (45–60 days for very early maturing, 60–120 days for early maturing, and 120–160 days for late maturing). If harvested late, the grain loss will be significant due to shattering and the natural grain color can also fade. However, if the grain is harvested early, it may become vitreous or translucent. In Ethiopia, traditional harvesting is done manually using a sickle (Figure 2(a)). The harvested panicles are gathered in batches, either on the day harvested or after ∼ 1–3 days, and temporarily stacked (in a conical shape, with the panicles toward the center) (Figure 2(b)) outdoors, under the shade, till it is ready for threshing. Such storage duration will help the teff grain to undergo the ripening process and dormancy breaking stages.
At present, teff grain pre- and postharvest losses are high (25–30%), largely incurred by lodging, shattering on harvest and harvest handling, threshing, and cleaning by traditional practices. Threshing is usually done by oxen feet trampling or manually by beating with sticks after spreading the dried panicles on a dry circular threshing floor. The threshing floor is prepared by smearing with cow dung, cement, or other suitable materials. The grain is traditionally winnowed by wafting in the open air with the help of a rectangular flat piece of dried leather called an afarsa or hafarsaa (O) (ca. 0.4 m width × 0.8 m length). Threshers or combine harvesters can be also used. However, grain loss is large because teff grain is very small and of light mass and can be easily blown away with the chaff. Use of mechanical threshers has recently shown an improvement in grain yield and quality. Teff productivity may be improved in the future by adaption of this technology. In Ethiopia, the grain is traditionally stored in gotera (A, T) or gotaara (O) (small hut-like stores) or pots or sacks. In comparison with other common cereals, teff grain is less prone to attacks by weevils and other storage pests. Thus, it can be safely stored under traditional storage conditions.
In local markets of Ethiopia, several small-scale grain traders distribute teff grain from major growing areas to the urban consumers and to regions of shortage in teff grain production. At Addis Ababa, teff grain is marketed in a place called Ehil berenda (Markato). Even though teff grain fetches premium price in the global cereal grain markets, at present, international teff grain export from Ethiopia is not practiced because of limited production. But when permitted, wherever the market is, companies (government-owned, joint ventures, farmers union associations, and private firms), such as Ethiopian Grain Trading Enterprise and Oromo Development Association, which export oil and pulses, have the potential to export teff grain as well.
- Physico-Chemical and Functional Properties of Grain tef [Eragrostis tef (Zucc.) Trotter] Starch. PhD thesis, University of Pretoria Pretoria South Africa. , 2003.
The proximate chemical composition of teff grain is shown in Table 1.
Carbohydrate content of teff grain is ∼ 73%, of which virtually all is starch. The teff starch properties are given in Table 2. Individual starch granules are very small (2–6 μm in diameter) (Figures 4(b)–4(f)), similar in size to rice starch granules, but larger than Amaranthus and quinoa starch granules. The shape is polygonal, smooth with no surface pores (Figure 4(f)). A few granules are essentially cubic, and at high magnification, some appear tortoise shell-shaped (Figure 4(e)). The composition of teff starch granules is similar to other normal native cereal starches, with 25–30% amylose. Gelatinization temperature is high, similar to other tropical cereal starches. The x-ray diffraction pattern of teff starch granule is A-type with crystallinity of ∼ 37% similar to rice starch granule. Pasting temperature is similar to that of maize starch, but cooking time for peak viscosity is longer. Peak, breakdown, and setback viscosities are lower than those of maize starch. The paste clarity of teff starch is opaque. The gel texture is short and smooth. α-Amylase degradation of teff starch granules is by surface erosion and endocorrosion in nature.
Because teff starch granules are very small, smooth, and of uniform size, they offer good functionality as a fat substitute and a flavor and aroma carrier, similar to other small-granule starches. Teff starch has good resistance to shear breakdown, and thus, it may find good application in high-shear processed foods. Also, because of its slow retrogradation tendency, it could have attractive applications where starch staling is preferred to be reduced (i.e., in baked and in refrigerated foods).
The fiber content of teff grain (Table 1) is apparently higher than most other common cereals, because the grain is very small and the bran is proportionally large.
Typical teff grain protein content (N × 6.25) is ∼ 11%, with a normal range of 9–13%. Thus, the protein content of teff grain is similar to other common cereals. The major amino acids are glutamic acid, alanine, proline, aspartic acid, leucine, and valine (Table 3). Methionine, phenylalanine, and histidine are slightly higher than in most other cereals, but serine and glycine are lower. Lysine and arginine are essentially higher in teff than in most other cereals, except rice and oats. The balance among essential amino acids is similar to the whole edible portion of egg protein, except for its lower lysine content. The overall amino acid profile of teff can be regarded as well balanced.
Osborne protein fractions of teff grain are shown in Table 1. Glutelins, albumins, and globulins are major fractions. The teff prolamin fractions are reported variable (low and high) depending on solvent type used in the extraction. The major prolamins of teff are somewhat similar to the α-prolamins of maize, sorghum, and Coix. Teff is different from other cereals in having higher albumins and globulins. Teff protein is essentially free of the type of gluten found in wheat. Because of this, teff grain foods are today increasingly became important for consumers allergic to wheat gluten (e.g., for celiac patients). As the main protein fractions (albumins and globulins) are the most digestible types, teff protein digestibility is also presumed high. Amino acid compositions of the various Osborne protein fractions are shown in Table 3.
The ash content in teff grain (Table 1) is apparently higher than in wheat, rye, maize, barley, oats, rice, and millets, in part because teff grain bran is proportionally large. In particular, calcium, copper, iron, and zinc (Table 4) contents are higher compared with those in barley, wheat, and sorghum. The iron content of traditionally harvested teff grain is especially high (∼ 15.7 mg per 100 g and in some reports as high as 27 mg per 100 g), in part because of grain contamination with the soil during harvest. However, when cleaned (with water and/or dilute acid), the level (∼ 5.7 mg per 100 g) is similar to other cereals. Most teff foods such as injera are fermented. Fermentation for injera processing is known to destroy phytic acid to the extent of ∼ 90%, and such destruction is known to contribute to high iron bioavailability in diets where fermented teff foods are the staples. Because of these two factors, iron-deficiency disease anemia is rare among regular teff injera consumers in Ethiopia.
Teff grain fat (Table 1) is lower than, for example, in maize and oats. Thus, teff is different from other small-grain cereals in having low fat even though the germ is large. As in most other cereal grains, palmitic, oleic, and linoleic acids are the major fatty acids (Table 5). Linolenic acid in teff is higher than in maize, sorghum, and wheat.
In teff (Table 6), thiamin content is typically lower, when compared with that in wheat, rye, barley, oats, rice, maize, millet, and sorghum. Though riboflavin content is considered to be high, it is nevertheless lower than in rye, barley, and oats. Niacin levels are similar to those in maize.
Normally, the grain is cleaned by manual sifting and sieving.
The cleaned grain is usually dry-milled to obtain whole flour. Traditionally in Ethiopia, this was done by wafcho (A) (T) or wafcoo (O) (top and bottom hard stones). Today, milling by hand, using hard stone, has been replaced by grist mills run by electric power and, where electric power is not available, by diesel engine or water power. The grist mill is made up of two abrasive hard-disk stones. During operation, one stone is stationary, while the other is rotating. The grain, fed into the center (eye) of the upper stone, is fragmented and ground between the two stones, and flour is issued at the periphery. At present, wet milling of teff grain for chemical component extraction like starch is not carried out.
Food made from teff grain is a staple diet for many Ethiopians. Teff is considered to have a better food value than major grains, namely, wheat, barley, sorghum, and maize, as it is normally used as a whole grain, that is, the germ and bran are consumed along with the endosperm. Teff flour is used primarily for making of injera (A), caabitaa or budeena (O), and tayeta (T). Teff injera is regarded to have pre- and probiotic potentials due to dietary fiber from whole grain and fermentation, respectively. Although the lactic acid bacteria (LAB) and yeast involved in the fermentation of injera are killed during baking, their dead cells and metabolic products are consumed as part of the diet, and these were implicated as promoters of gut health. In injera-making features, teff grain flours are superior to any other cereal grain flours used. The Ethiopian diaspora is using injera from rice or blend of rice and wheat flour, although the injera suffers from staling, resilience, and plasticity losses after a day. The rice flour injera-making ability is similar to teff probably because of somewhat similar starches in both grains. The hydrophobic and less polymerized nature of teff grain protein prolamins is in part implicated as contributor to the making of superior semileavened flatbread injera when compared with sorghum injera. Teff grain flour is also used to make sweet unleavened bread called kitta (A), bixxille (O), and daguwalo (T). Kitta can be consumed as bread, or it can be used as an adjunct in traditional opaque beer (tella (A) or farsoo (O)) or local spirit (katikalla (A) or araqii (O)). Porridge (genefo (A) or marqaa (O)) can also be made from teff flour. Thin, fermented teff flour batter is used to prepare soup (muk, (A)). Unfermented teff flour dough is also used in the preparation of traditional snacks (dabo kolo (A) or hunkuroo (O)), where the dough is rolled into small balls and then roasted on a hot griddle. In the United States, teff has been promoted as a thickener for soups, stews, and gravies probably because teff flour paste gives the product a short and stiff texture. Teff grain flour imparts a slight molasses-like sweetness to food products, making its inclusion in porridges, pancakes, biscuits, cookies, cakes, stir-fry dishes, casseroles, soups, stews, and puddings desirable. Processing of teff grain in Ethiopia has been limited to the household level. To date, technologies for large-scale commercial processing of teff grain, for the preparation of foods like injera, are not well advanced. However, apart from traditional usage, recent reports indicate that teff grains, along with soybean, chickpea, and other grains, are being used in the baby food industry. Teff grain flours are used to improve dietary fiber, starch, protein, and mineral content supply in gluten-free food products and in wheat bread to improve the iron and antioxidant contents of the bread.
In Ethiopia, injera is regarded as the national staple food. Flowcharts of the injera-making process and injera-baking process are shown in Figures 5 and 6, respectively. The process involves fermentation and then baking of the batter.
Flour is mixed with water and the dough is kneaded, usually by hand. Fermentation for injera making involves two phases that can last a total of 24–72 h. The first phase starts spontaneously when the flour is wetted, due to contaminating microorganisms. Or it can be initiated by addition of irsho (A) (T) or raacitii (O) (yellowish liquid saved from the previous batch fermentation). The initial 18–24 h is notable for vigorous gas evolution and maximum dough expansion. At about 30–33 h, an acidic yellowish liquid appears on the dough surface. This phase is characterized by a decrease in gas evolution up to 31 h, an increase in liquid volume up to 48 h, and a decrease in pH to below 5.8.
The first phase of fermentation results in a liquid/solid separation after ∼ 24 h. The layer of liquid is then removed. About 10% of the fermenting dough is mixed with water (1:3 ratio) and boiled (2–5 min), and as a result of starch gelatinization, a dough binder, called absit, is formed. The absit is cooled and added to the fermentation vat signaling the second phase of fermentation. The second phase (0.5–2 h) is characterized by a short duration of dough expansion and gas formation.
During the first phase of fermentation, the yellowish liquid that is removed contains water-soluble nutrients (amino acids, sugars, and minerals) and a large number of microorganisms involved in the fermentation. This has negative nutritional consequences. Thus, injera baked from a batter at ∼ 31 h of fermentation without discarding the liquid is recommended as being more nutritious.
A complex group of microorganisms is known to be involved in teff fermentation. A total of 107 LAB (some heterofermentative and some homofermentative) and 68 yeast strains are reported in the teff fermentation. Bacteria belonging to the Enterobacteriaceae family are thought to initiate the fermentation. During the first 18 h of fermentation, the activities of these bacteria reduce the dough pH to ∼ 5.8. A group of LAB of which major ones are Leuconostoc mesenteroides, Streptococcus faecalis, Pediococcus cerevisiae, P. pentosaceus, Lactobacillus brevis, L. plantarum, and L. fermentum are involved at the later phase of fermentation (18–72 h) in reducing the dough pH from 5.8 to 3.8. During the later phase of fermentation (22–24 h), yeasts of two genera Saccharomyces and Torulopsis are reported to be involved. In the later phase (∼ 48 h), yeasts belonging to the genera Candida and Pichia are the dominant types isolated from the yellowish liquid removed from the dough. In addition to amylases present in the grain, the bacteria species Bacillus sp. A-001 involved in the fermentation has been characterized as one of the amylase-producing bacteria involved in partially attacking the starch granules.
In the traditional teff fermentation for injera making, commercial yeast is not added externally. The source of the yeast is either from irsho or from the endogenous microflora of teff grain and its flour that grows in the batter after the flour is wetted with water. Therefore, the yeast in the fermentation of teff for injera making can be regarded as symbiotic yeast.
Injera is usually baked after ∼ 24 h of fermentation. After the fermentation, the batter is diluted slightly with water and then poured using circular motion from the outer perimeter toward the center onto a hot, round, smooth griddle called a metad (A) or eelee caabitaa (O). It is then covered with a metad lid called akambalo (A), qadaada eelee caabitaa (O) to prevent steam from escaping. The griddle is traditionally made from clay. Before pouring the batter, the metad surface is swabbed with ground oilseeds, commonly rapeseed or with animal fat in a piece of cloth. This prevents the injera from sticking to the metad surface. Depending on the batter thickness, heat intensity applied, and steaming, with the current electrically heated baking griddle, injera can be baked in 2–3 min.
Based on the duration and nature of the fermentation involved, three common types of injera are prepared:(1) injera made from dough that does not contain absit, characterized by a soft, thin, fine appearance and a sour taste without the ‘eyes’ of injera (surface air cells); (2) injera made from partially fermented paste (12–24 h fermentation) called aflegna (A) (O) or bekuo (T), characterized by a sweet flavor, a pleasant odor, and a rusty red underside; and (3) injera made from overfermented paste called komtata injera (A) (T) or qomxoxaa caabitaa (O) that tastes very sour and is regarded as less nutritious. The thick batter used for aflegna injera is also used to prepare a slightly concave, thick flatbread called cumboo (O). Cumboo is traditionally baked on the preheated surface of a small-size concave griddle called bedde, which is placed upside down on a flat larger griddle called elle chumbo. After pouring the 12–24 h fermented thick batter onto the upside down concave bedde surface and covering with the lid, gentle heat is applied underneath of the larger griddle, and depending on the batter size and heat intensity applied, the baking time for cumboo is between 1 and 3 h.
Teff can be cultivated under harsh environmental conditions where most other cereals are less viable. It has relatively few pest and disease problems in the field. The grain is less attacked by weevils. The nutrient composition of teff grain indicates that it has good potential to be used in various diets and as functional foods in health-food markets worldwide. However, the grain yield of teff is low. The mechanized farming technologies that are used for the production of other cereal grains can be problematic for teff because the plant stems are very thin and short and the grain is very small. Manipulation of teff plant genes through research on germplasm genetic diversity, improvement of yield using molecular breeding approach, and a continuous teff production technology improvement for maximum grain production are required.
At present, the milling of teff grain is limited to cottage-type millers. Processing of teff for different foods is usually by traditional ways and mostly limited to the household level. Over the last decade, utilization of teff grain as whole grain supplements and for gluten-free markets is increased. More research on teff large-scale milling and processing of teff grain for different commercial foods is required to promote worldwide teff product utilization.
What major features distinguish teff grain (particularly its starch and protein) from other common tropical cereals like sorghum, rice, and maize?
Why is the productivity of the teff plants so low compared with that of maize and rice? Could teff be grown near where you live?
Why are teff grain products nutritionally and functionally attractive for health-food markets (e.g., for celiac patients)? Can you design and develop a novel food product utilizing teff grain?
How is injera made? Is teff grain essential for injera manufacture? Does teff injera have prebiotic and probiotic effects?
Value chain efficiency for teff productivity improvement such as high-yielding and lodge-resistant variety developments coupled with mechanized or semiautomated production technologies that suit very thin, short teff plant stems and very small grain size of light mass that would boost teff grain production and minimizes grain postharvest losses.
Development of teff grain-based composite flours for injera and other teff products.
Efficiency of teff injera processing stages and cottage and large-scale injera processing and preservation.
Teff grain-based ready to eat foods for health-food markets such as gluten-free foods for celiac patients.
Beverages from Grains: Fermentation: Foods and Nonalcoholic Beverages; Food Grains and the Consumer: Cultural Differences in Processing and Consumption; Grains and Health; Food Grains and Well-being: Functional Foods: Dietary Fibers, Prebiotics, Probiotics, and Synbiotics; Functional Foods: Overview; Food Grains: Intolerance, Allergy and Diseases: Celiac Disease; The Gluten-Free Diet; Appendix 1: Nutrient-Composition Tables for Grains and for Grain-Based Products; Grain Composition and Analysis: The Composition of Food Grains and Grain-Based Products; Grains Around the World: Grain Production and Consumption: Africa; The Basics: Grain and Plant Morphology of Cereals and how characters can be used to identify varieties; The Grain Crops: An Overview; Grain: Morphology of Internal Structure; Taxonomic Classification of Grain Species; The Cereal Grains: An Overview of the Family of Cereal Grains Prominent in World Agriculture; Millet Minor: Overview; Oats: Overview; Rice: Overview; The Legumes and Pseudocereals: Amaranth: Overview.
/tef/ noun an African cereal grass grown for its grain which yields a white flour: Eragrostis tef [ Amharic ēf ]. ...
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