Metal(loid)s Profile of Four Traditional Ethiopian Teff Brands: Geographic Origin Discrimination.

Among the most renowned Ethiopian food crops, teff (Eragrostis tef (Zucc.)Trotter) is the most nutritious and gluten-free cereal. Because of the increase in demand for teff, it is necessary to establish geographic origin authentication of traditional teff brands based on multi-element fingerprint. For this purpose, a total of 60 teff samples were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Accuracy of the laboratory procedure was verified by the analysis of rice flour standard reference material (NIST SRM 1568b). In this context, four traditional teff brands (Ada'a, Ginchi, Gojam and Tulu Bolo) were analytically characterized using multi-element fingerprint and further treated statistically using linear discriminant analysis (LDA). Due to obvious extrinsic Fe, Al and V contamination, these elements were excluded from the discriminant model. Five elements (Cu, Mo, Se, Sr, and Zn) significantly contributed to discriminate the geographical origin of white teff. On the other hand, Mn, Mo, Se and Sr were used as discriminant variables for brown teff. LDA revealed 90 and 100% correct classifications for white and brown teff, respectively. Overall, multi-element fingerprint coupled with LDA can be considered a suitable tool for geographic origin discrimination of traditional teff brands.

Synthesis of lignin-carbohydrate complex-based catalyst from Eragrostis tef straw and its catalytic performance in xylose dehydration to furfural.

A new catalyst was successfully prepared by functionalization of the lignin-carbohydrate complex structure in the Eragrostis tef straw via simultaneous carbonization and sulfonation. The physical and chemical properties of the surface of the synthesized catalyst were checked by FTIR and XRD. The FTIR results indicate the prepared catalyst exhibited functional groups such as -SO3H, -COOH, and -OH. The synthesis conditions like the temperature and time of carbonization and sulfonation showed significant effect the amount of the strong acid doped into the carbonized lignin-carbohydrate matrix. The newly prepared catalyst was checked for dehydration of xylose to furfural and revealed of course that it has the potential. The maximum yield of furfural 62.4% was achieved and the catalyst showed excellent reusability for 5 runs without significant loss of catalystic activity. The use of catalysts prepared from Eragrostis tef straw is a green strategy for converting xylose to furfural, as these catalysts are solving the problems associated with the use of mineral acid catalysts.

Effects of different industrial processes on the phenolic composition of white and brown teff (Eragrostis tef (Zucc.) Trotter).

Teff is currently being incorporated into a range of foodstuffs, especially gluten-free flakes and extruded products. The main objective of this work was to assess the effects of different treatments (industrial milling, formation of flakes and extrusion) on the phenolic composition of two types of teff grains differing in their colour (white and brown). Fifty-nine phenolic compounds were detected by HPLC-DAD-MSn. C-glycosyl flavones accounted for more than 90% of the total phenolic contents in both teff types. White teff mostly contained apigenin-derived flavones (86-92%), whereas luteolin derivatives prevailed in brown teff (91-94%). The industrial processes, mainly flaking and extrusion, caused marked changes in the phenolic composition, some of which were dependent on the teff type. In both teff types, processing changed the phenolic profiles similarly by increasing C-monoglycosyl flavones and decreasing acylated derivatives. However, the total content was increased in flakes and extruded products made only from brown teff grains.

Phytotoxic Neocassane Diterpenes from Eragrostis plana.

Five new neocassane-like diterpenes (1-5) were isolated from the roots of Eragrostis plana. Their structures were elucidated by spectroscopic data, and the absolute configurations of the representative compounds neocassa-12(17),15-dien-3-one (2) and neocassa-12(13),15-diene-3,14-dione (5) were assigned by vibrational circular dichroism. The phytotoxic activity of compounds 3, 4, and 5 was evaluated against the germination and growth of Ipomoea grandifolia and Euphorbia heterophylla. Compound 4 exhibited the most potent activity for growth variables, resulting in the smallest radicle length of I. grandifolia and in the smallest aerial part length of E. heterophylla. Compound 5 reduced the germination speed index more effectively than the herbicide glyphosate (Roundup).

Towards coeliac-safe bread.

Gluten-free foods cannot substitute for products made from wheat flour. When wheat products are digested, the remaining peptides can trigger an autoimmune disease in 1% of the North American and European population, called coeliac disease. Because wheat proteins are encoded by a large gene family, it has been impossible to use conventional breeding to select wheat varieties that are coeliac-safe. However, one can test the properties of protein variants by expressing single genes in coeliac-safe cereals like maize. One source of protein that can be considered as coeliac-safe and has bread-making properties is teff (Eragrostis tef), a grain consumed in Ethiopia. Here, we show that teff α-globulin3 (Etglo3) forms storage vacuoles in maize that are morphologically similar to those of wheat. Using transmission electron microscopy, immunogold labelling shows that Etglo3 is almost exclusively deposited in the storage vacuole as electron-dense aggregates. Of maize seed storage proteins, 27-kDa γ-zein is co-deposited with Etglo3. Etglo3 polymerizes via intermolecular disulphide bonds in maize, similar to wheat HMW glutenins under non-reducing conditions. Crossing maize Etglo3 transgenic lines with α-, ß- and γ-zein RNA interference (RNAi) lines reveals that Etglo3 accumulation is only dramatically reduced in γ-zein RNAi background. This suggests that Etglo3 and 27-kDa γ-zein together cause storage vacuole formation and behave similar to the interactions of glutenins and gliadins in wheat. Therefore, expression of teff α-globulins in maize presents a major step in the development of a coeliac-safe grain with bread-making properties.

Glucose and Insulin Response of Aged Horses Grazing Alfalfa, Perennial Cool-Season Grass, and Teff During the Spring and Late Fall.

Spring and late fall grazing can lead to metabolic problems in horses (Equus caballus L.) as a result of elevated nonstructural carbohydrates (NSC) in pastures. Therefore, the objectives were to determine the impact of different forage species on blood glucose and insulin concentrations of horses during the spring and late fall. Research was conducted in May (spring) and October (late fall) in St. Paul, MN. Alfalfa (Medicago sativa L.) and mixed perennial cool-season grasses (CSG) were grazed in spring, and CSG and teff (Eragrostis tef [Zucc.] Trotter) were grazed in late fall by six adult horses randomly assigned to a forage in a cross-over design. Jugular catheters were inserted 1 hour before the start of grazing, and horses had access to pasture from 8 AM to 4 PM in the spring and 8 AM to 12 PM in the late fall. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2 hours intervals after turnout. Plasma and serum samples were collected and analyzed for glucose and insulin, respectively. Corresponding forage samples were taken by hand harvest. Seasons were analyzed separately, and data were analyzed using the MIXED procedure in SAS with P ≤ .05. Teff had lower NSC compared with CSG in the late fall (P ≤ .05) with subsequently lower average glucose, average insulin, and peak insulin in horses grazing teff compared with CSG (P ≤ .05). These results suggest grazing teff could lower the glucose and insulin response of horses during late fall.

Plasma Amino Acid Concentrations of Horses Grazing Alfalfa, Cool-Season Perennial Grasses, and Teff.

The impact of forage species on plasma amino acid (AA) concentrations of grazing horses (Equus caballus L.) is unknown. The objectives of this study were to determine the impact of different forage species on plasma AA concentrations and protein synthesis. Research was conducted in July in St. Paul, MN, USA. Alfalfa (Medicago sativa L.), mixed perennial cool-season grasses (CSGs), and teff (Eragrostis tef [Zucc.] Trotter) pastures were grazed by six horses randomly assigned to one of three forage types in a replicated Latin-square design. Horses had access to pasture each day. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2 and 4 hours after turnout. Corresponding forage samples were taken by hand harvest and analyzed for AA concentrations. Equine muscle satellite cell cultures were treated with sera from grazing horses to assess de novo protein synthesis. Data were analyzed using PROC MIXED in SAS. When evaluating forage, AA concentrations were generally lowest in teff and highest in CSG (P ≤ .05). Significant differences in threonine concentration in the plasma were observed; there was no effect on de novo protein synthesis of cultured equine myotubes treated with plasma obtained from the grazing horses (P ≥ .20). As a result, although there were significant differences in forage AA content, only plasma threonine concentration was different at 4 hours with no effect on protein synthesis of cultured equine satellite cells.

New Phytotoxic Cassane-like Diterpenoids from Eragrostis plana.

Eragrostis plana (Nees) is an allelopathic plant with invasive potential in South American pastures. To isolate and identify phytotoxic compounds from leaves and roots of E. plana, a bioassay-directed isolation of the bioactive constituents was performed. This is the first report on a new diterpene carbon skeleton, neocassane, and of three new neocassane diterpenes, neocassa-1,12(13),15-triene-3,14-dione, 1; 19-norneocassa-1,12(13),15-triene-3,14-dione, 2; and 14-hydroxyneocassa-1,12(17),15-triene-3-one, 3, identified from the roots. Compounds 1, 2, and 3 inhibited the growth of duckweed by 50% at concentrations of 109 ± 28, 200 ± 37, and 59 ± 15 µM, respectively. Compound 2 was fungicidal to Colletotrichum fragariae, Colletotrichum acutatum, and Colletotrichum gloeosporioides. The compounds identified here could explain the allelopathy of E. plana. The description of the newly discovered compounds, besides contributing to the chemical characterization of the species, may be the first step in the study of the potential of these compounds as bioherbicides.

Conversion of Eragrostis plana Nees leaves to activated carbon by microwave-assisted pyrolysis for the removal of organic emerging contaminants from aqueous solutions.

Eragrostis plana Nees leaves, abundant lignocellulosic biomass, was used as carbon source for preparation of activated carbon, by using microwave-assisted pyrolysis and chemical activation. The novel activated carbon (MWEPN) was characterised by FTIR, CHN elemental analysis, Boehm's titration method, TGA, SEM, N2 adsorption/desorption curves and pH of the point of zero charge (pHpzc). Afterwards, the adsorbent was successfully employed for adsorption of the two emerging contaminants (caffeine and 2-nitrophenol). The results indicated that MWEPN had a predominantly mesoporous structure with a high surface area of 1250 m2 g-1. FTIR analysis indicated the presence of carbonyl, hydroxyl and carboxylic groups on the surface of MWEPN. The Boehm analysis showed the existence of the high amount of acid moieties on the surface of activated carbon. Adsorption kinetic indicated that the system followed the Avrami fractional order at the optimal pH of 7. The equilibrium time was attained at 30 min. The Liu isotherm model better described the isothermal data. Based on the Liu isotherm, the maximum sorption capacities (Qmax) of caffeine and 2-nitrophenol adsorbed onto activated carbon at 25 °C were 235.5 and 255.8 mg g-1, respectively.

Structural profile of soluble and bound phenolic compounds in teff (Eragrostis tef) reveals abundance of distinctly different flavones in white and brown varieties.

Reliable data on polyphenol in teff, an increasingly important food crop, is currently lacking. This study investigated the structural and quantitative profile of soluble and bound polyphenols in white and brown teff grown in Ethiopia and USA using LC-tandem quadrupole mass spectrometry. Thirty-four phenolic compounds (32 newly identified in teff), mostly flavones and phenolic acid derivatives, were characterized. Unusually high levels of flavones were present in both white (1398-2049 µg/g), and brown (1720-1847 µg/g) teff soluble fractions. Interestingly, white teff exclusively contained apigenin derivatives, whereas brown teff contained mainly luteolin derivatives, mostly di-C-linked-glycosides. Additionally, non-extractable procyanidins (condensed tannins) were detected in brown teff only. Phenolic acids (600-728 µg/g) were mostly present in bound fractions, dominated by ferulic acid. Polyphenol profiles of Ethiopian and USA grown grains were similar. The high levels of the relatively rare flavones in teff may have important implications in chronic disease prevention.

Dietary Intakes of Minerals, Essential and Toxic Trace Elements for Adults from Eragrostis tef L.: A Nutritional Assessment.

This study analysed the contents of thirty-six mineral and trace elements in teff (Eragrostis tef L.) grains. What is more, dietary intakes were calculated. Inductively coupled plasma mass spectrometry (ICP-MS) was used to assess mineral and trace element contents. Consequently, the appropriate Recommended Dietary Allowance (RDA) or adequate intake (AI), and provisional tolerable weekly intake (PTWI) or provisional tolerable monthly intake (PTMI) values for adults were determined according to the Food and Agriculture Organization/World Health Organization (FAO/WHO) and Institute of Medicine (IOM) regulations. Teff is a significant contributor to RDAs and AIs for females in the following order: Mn > Cu > Zn ≥ Mg > Fe ≥ P and Ca. For males, teff contributes in the order, Mn > Cu > Fe > Zn ≥ P ≥ Mg > and Ca. The concentration of arsenic (65.9 µg/kg) in brown teff originating in Bolivia exceeded the average acceptable value set by Reg. No. 1881 of 6-50 µg/kg in cereals consumed in the EU. The PTWIs or PTMIs for Al, Cd, Sn and Hg were all under 7%, which is below the limits of toxic element intake related to the body weight of 65 kg for adult females and 80 kg for males, set by the FAO/WHO. Teff grains can be recommended as a valuable and safe source of minerals and trace elements.

Analysis of volatile compounds in gluten-free bread crusts with an optimised and validated SPME-GC/QTOF methodology.

The aroma of bread crust, as one of the first characteristics perceived, is essential for bread acceptance. However, gluten-free bread crusts exhibit weak aroma. A SPME-GC/QTOF methodology was optimised with PCA and RSM and validated for the quantification of 44 volatile compounds in bread crust, extracting 0.75 g of crust at 60 °C for 51 min. LODs ranged between 3.60 and 1760 µg Kg-1, all the R2 were higher than 0.99 and %RSD for precision and %Er for accuracy were lower than 9% and 12%, respectively. A commercial wheat bread crust was quantified, and furfural was the most abundant compound. Bread crusts of wheat starch and of japonica rice, basmati rice and teff flours were also quantified. Teff flour and wheat starch crusts were very suitable for improving gluten-free bread crust aroma, due to their similar content in 2-acetyl-1-pyrroline and 4-hydroxy-2,5-dimethyl-3(2H)-furanone compared to wheat flour crust and also for their high content in pyrazines.

In vitro digestibility, free and bound phenolic profiles and antioxidant activity of thermally treated Eragrostis tef L.

BACKGROUND: Total phenolic content, phenolic profile and antioxidant activity were determined in free and bound phenolic fractions of thermally treated brown and white teff grains. RESULTS: Phenolic content in raw brown and white teff (1540 and 992 mg gallic acid equivalent kg-1 ) as well as antioxidant activity (6.3 and 5.5 mmol trolox equivalent kg-1 ) were higher in free phenolic fractions. The most significant decrease in total phenolics was observed after application of the sous-vide method (35% for brown teff and 11% for white teff). Main free phenolics of heat-treated teff were ferulic, protocatechuic, p-coumaric and ellagic acids, rutin and epigallocatechin. Main bound phenolics were ferulic, gallic, sinapic and ellagic acids, catechin and epigallocatechin. The detrimental effect on free and bound quercetin and bound cinnamic acid concentrations was also examined during heat treatment. Thermally treated brown teff showed a high level of in vitro organic matter digestibility if water cooking and rice cooker (both 99.5%) and sous-vide (96.5%) methods were applied. CONCLUSION: The sous-vide method may be recommended as the most suitable hydrothermal treatment for grains of teff when compared with water cooking and rice cooker methods. © 2017 Society of Chemical Industry.

Tef: The Rising Ancient Cereal: What do we know about its Nutritional and Health Benefits?

This review covers the nutritional significance of tef cereal as compared to other common cereals with emphasis on carbohydrate content and starch digestibility, protein content, iron and zinc bioavailability and antioxidant potentials. Tef is a gluten free cereal and contains the highest iron and calcium among other cereals. It has high micro- and macro- nutritional profile and is becoming globally popular in the healthy grain food chain. Tef starch has a high gelatinization temperature, an essential precondition in the preparation of low glycemic index foods. There are significantly conflicting reports of iron content of tef ranging from 5 to 150 mg/100 g dm. The traditional fermentation of injera reduced majority of the phytic acid but no significant change to mineral bioavailability was observed. This review indicated that studies on starch digestibility, protein characterization, amylase and protease inhibitors, mineral bioavailability and antioxidant potentials are needed to further explore the nutritional and health benefits of tef.

Eragrostis plana Nees as a novel eco-friendly adsorbent for removal of crystal violet from aqueous solutions.

Eragrostis plana Nees (EPN) was used as new and eco-friendly adsorbent for the removal of crystal violet dye (CV) from aqueous solution. Specific surface area (BET), scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), point of zero charge (pHPZC), and modified Boehm titration method were used to characterize the EPN material. The effects of initial pH of solution, adsorbent mass, contact time and initial dye concentration, and temperature were studied in batch adsorption mode. Kinetic data were evaluated by pseudo-first-order and pseudo-second-order models. The result exhibited that pseudo-second-order model well described the adsorption kinetics of CV onto EPN. Langmuir, Freundlich, and Sips isotherm models were used for analysis of the isothermal data. The equilibrium data of adsorption of CV onto EPN was better fitted with the Sips isotherm. Based on the Sips isotherm model, the maximum adsorption capacity was 76.20 ± 1.20 mg g-1 at 333 K. A high desorption of CV from EPN was obtained using 1.00 mol L-1 of CH3COOH as eluent. The thermodynamic data indicated that the adsorption was spontaneous, endothermic, and physical process. EPN can be used as alternative adsorbent to remove CV from aqueous solution.

Gluten-Free Sources of Fermentable Extract: Effect of Temperature and Germination Time on Quality Attributes of Teff [Eragrostis tef (zucc.) Trotter] Malt and Wort.

This study was conducted to evaluate the behavior of a white teff variety called Witkop during malting by using different parameters (germination temperature and duration) and to identify the best malting program. Samples were evaluated for standard quality malt and wort attributes, pasting characteristics, ß-glucan and arabinoxylan content, and sugar profile. It was concluded that malting teff at 24 °C for 6 days produced acceptable malt in terms of quality attributes and sugar profile for brewing. The main attributes were 80.4% extract, 80.9% fermentability, 1.53 mPa s viscosity, 7.4 EBC-U color, 129 mg/L FAN, and 72.1 g/L of total fermentable sugars. Statistical analysis showed that pasting characteristics of teff malt were negatively correlated with some malt quality attributes, such as extract and fermentability. Witkop teff appeared to be a promising raw material for malting and brewing. However, the small grain size may lead to difficulties in handling malting process, and a bespoke brewhouse plant should be developed for the production at industrial scale.

Functionality of maize, wheat, teff and cassava starches with stearic acid and xanthan gum.

Consumer concerns to synthetic chemicals have led to strong preference for 'clean' label starches. Lipid and hydrocolloids are food friendly chemicals. This study determines the effects of stearic acid and xanthan gum alone and in combination on the functionality of maize, wheat, teff and cassava starches. An increase in viscosity was observed for all starches with stearic acid and xanthan gum compared to the controls with cassava having the least increase. A further increase in viscosity was observed for the cereal starches with combination of stearic acid and xanthan gum. Stearic acid reduced retrogradation, resulting in soft textured pastes. Combination of stearic acid and xanthan gum reduced the formation of type IIb amylose-lipid complexes, syneresis, and hysteresis in cereal starches compared to stearic acid alone. A combination of stearic acid and xanthan gum produce higher viscosity non-gelling starches and xanthan gum addition increases physical stability to freezing and better structural recovery after shear.

Phytic acid degrading lactic acid bacteria in tef-injera fermentation.

Ethiopian injera, a soft pancake, baked from fermented batter, is preferentially prepared from tef (Eragrostis tef) flour. The phytic acid (PA) content of tef is high and is only partly degraded during the fermentation step. PA chelates with iron and zinc in the human digestive tract and strongly inhibits their absorption. With the aim to formulate a starter culture that would substantially degrade PA during injera preparation, we assessed the potential of microorganisms isolated from Ethiopian household-tef fermentations to degrade PA. Lactic acid bacteria (LAB) were found to be among the dominating microorganisms. Seventy-six isolates from thirteen different tef fermentations were analyzed for phytase activity and thirteen different isolates of seven different species were detected to be positive in a phytase screening assay. In 20-mL model tef fermentations, out of these thirteen isolates, the use of Lactobacillus (L.) buchneri strain MF58 and Pediococcus pentosaceus strain MF35 resulted in lowest PA contents in the fermented tef of 41% and 42%, respectively of its initial content. In comparison 59% of PA remained when spontaneously fermented. Full scale tef fermentation (0.6L) and injera production using L. buchneri MF58 as culture additive decreased PA in cooked injera from 1.05 to 0.34±0.02 g/100 g, representing a degradation of 68% compared to 42% in injera from non-inoculated traditional fermentation. The visual appearance of the pancakes was similar. The final molar ratios of PA to iron of 4 and to zinc of 12 achieved with L. buchneri MF58 were decreased by ca. 50% compared to the traditional fermentation. In conclusion, selected LAB strains in tef fermentations can degrade PA, with L. buchneri MF58 displaying the highest PA degrading potential. The 68% PA degradation achieved by the application of L. buchneri MF58 would be expected to improve human zinc absorption from tef-injera, but further PA degradation is probably necessary if iron absorption has to be increased.

Structural characterization of arabinoxylans from two African plant species Eragrostis nindensis and Eragrostis tef using various mass spectrometric methods.

RATIONALE: The arabinoxylans are one of the main components of plant cell walls and are known to play major roles in plant tissues properties depending in particular on their structural features. It has been recently shown that one of the strategies developed by resurrection plants to overcome dehydration is based on cell wall composition. For this purpose, the structural characterization of arabinoxylans from desiccation-tolerant grass Eragrostis nindensis (E. nindensis) was compared with its close relative, the desiccation-sensitive Eragrostis tef (E. tef) in order to further understand mechansism of desiccation tolerance in resurrection plants. METHODS: Ion mobility spectrometry coupled to mass spectrometry (IM-MS) in combination with the conventional mass spectrometric approaches, including matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), electrospray ionization multistage tandem mass spectrometry (ESI-MS(n)) and gas chromatography/mass spectrometry (GC/MS), were used to characterize arabinoxylan fragments obtained after endo-xylanase digestion of leave extracts from E. nindensis and E. tef. RESULTS: Whole fingerprinting by MALDI-MS analysis showed the presence of various arabinoxylan fragments within leaves of E. nindensis and E. tef. The monosaccharide composition and some linkage information were determined by GC/MS experiments. Information regarding the branching and sequence details was obtained by ESI-MS(n) experiments after sample permethylation. The presence of structural isomeric ions with different collision cross sections was evidenced by IM-MS which could be differentiated using ESI-MS(n). CONCLUSIONS: We have shown that an orthogonal approach, and especially IM-MS associated to ESI-MS(n) (n = 2 to 4) and GC/MS allowed characterization of arabinoxylan fragments of E. nindensis and E. tef and revealed the presence of isomeric structures. The same arabinoxylan structures were identified for both species but in different relative abundance. Moreover, this work illustrated that IM-MS can efficiently separate isomeric structures and advantageously complements the conventional mass spectrometric methodologies used for arabinoxylan structural characterization.

Influence of sourdough on in vitro starch digestibility and predicted glycemic indices of gluten-free breads.

Gluten-free flours (buckwheat, quinoa, sorghum and teff) were fermented using obligate heterofermentative strain Weissella cibaria MG1 (Wc) and facultative heterofermentative Lactobacillus plantarum FST1.7 (Lp). Starch hydrolysis of breads with and without sourdough (controls) was analyzed in vitro using enzymatic digestion followed by dialysis (10-11 kDa). Hydrolysis indices as well as predicted glycemic indices (pGI) were calculated from reducing sugars released into the dialysate. Amounts of resistant starch (RS; % of total starch) were determined by enzymatic digestion. Upon sourdough addition, RS significantly decreased in buckwheat (Wc 1.28%, Lp 1.44%) and teff sourdough breads (Wc 0.87%, Lp 0.98%) in comparison to their controls (2.01% and 1.92%, respectively). However, no correlation was found with starch hydrolysis. Predicted GIs were reduced upon sourdough addition in wheat (ctrl 100; Wc 85; Lp 76) in comparison to control breads. This was not the case in most gluten-free breads with the exception of sorghum (ctrl 72; Lp 69) and teff sourdough breads (ctrl 74; Lp 68). In contrast, increased pGIs were found in quinoa (ctrl 95; Wc 106; Lp 103) and buckwheat sourdough breads (ctrl 80; Wc 89; Lp 86).