El Tef: cultivo de interés en el desarrollo de alimentos: estudio de sus características y potencial industrial

Se han estudiado las características ingenieriles y técnico-funcionales de la harina de tef [Eragrostis tef (Zucc.)Trotter] de tres variedades (DZ-01-99, DZ-Cr-37 y DZ-Cr-387), así como sus potenciales aplicaciones alimentarias. La variedad y el tipo de molino afectaron notablemente a sus características. En general presentaron peores características de flujo y más sensibilidad a cambios de humedad que las harinas de trigo y arroz. La viscoelasticidad de los geles y las propiedades texturales sugieren que las harinas de tef serían ingredientes adecuados en formulaciones de alimentos tipo gel. La incorporación de tef en masas panarias de trigo redujo ambos módulos viscoelasticos y aumentó la capacitancia mecánica de las masas, condujo a panes tipo chapata de calidad adecuada, con mayor contenido mineral y menor velocidad de digestión del almidón. Los panes con DZ-01-99 mostraron mayor contenido en flavonoides y actividad anti-radical que el resto de variedades y que el pan control

Effect of mill type and mechanical kneading conditions on fermentation kinetics of tef dough during injera making and phytate to mineral molar ratio of injera

Producción CientíficaInjera is Ethiopian traditional fermented flatbread which is made mostly from tef flour. Tef grain is milled and the flour kneaded to have batter-like dough which will ferment before injera baking. The influence of mill type: hammer mill (HM), disc mill (DM) and blade mill (BM) and mechanical kneading speed-time combinations (K1, K5, and K9) on fermentation kinetics was investigated. Phytate to mineral molar ratio (Fe, Zn and Ca) of tef injera was also investigated as affected by mill type and different kneading conditions. In both milling and kneading levels, maltose was the highest sugar concentration initially, followed by glucose and fructose. As fermentation continued, a similar trend in maltose breakdown was seen among HM, DM, and BM. However, different patterns of glucose and fructose breakdown were seen on HM than DM and BM. Similarly, HM had a different pattern in increment of lactic acid concentration than DM and BM. Similar trend in maltose concentration was seen between K1, K5, and K9. Again glucose breakdown and the increment of lactic acid in K9 were different than that of K1 and K5. Phytate/mineral molar ratio of BM was significantly different (p<0.05) from HM and DM. There was also a significant difference (p<0.05) in phytate/mineral molar ratio between K1, K5, and K9. Decreased phytate/mineral molar ratio was seen with increasing of kneading speed (rpm) for a longer period of time. The effect of mill type and kneading speed and time combinations on fermentation kinetics and phytate/mineral molar ratio were significant.Ministerio de Economía y Competitividad - FEDER (AGL2015-63849-C2-2-R)Junta de Castilla y León - FEDER (Project VA072P17

Influence of milling type on tef injera quality

Producción CientíficaInjera is an Ethiopian flat bread that is mostly made from tef flour. Injera making on an industrial scale holds a significant economic and social interest but requires a thorough study of how the process variables affect the product quality. The aim of this work was to investigate the effects of mill type (hammer, disc, and blade) on injera sensory quality and starch digestibility. The application of software for the determination of injera quality descriptors and its comparison with visual human eye evaluation was also established. Injera made with disc mill flour had higher overall acceptability (6.6) than that obtained from hammer mill (4.2) and blade mill (4.1) flours. The injera made with blade mill flour obtained the lowest rapidly available glucose and rapidly digestible starch. The outcome of introducing software for the determinations of injera number of eyes was found effective; its difference with human eye determination was insignificant.Ministerio de Economía y Competitividad - FEDER (AGL2015-63849-C2-2-R)Junta de Castilla y León - FEDER (Project VA072P17

The effect of mechanical kneading and absit preparation difference on tef injera quality

Producción CientíficaThe aim of this study was to investigate the effect of mechanical kneading and ‘absit’ preparation difference on the quality of tef injera, the staple food of Ethiopians. Standard methods were adopted to determine the starch fraction, total phenol, flavonoid, phytate and tannins of injera. Sensory injera quality was assessed using 9-point-hedonic scale. Change in kneading conditions (time/speed) did not significantly affect the free sugar (FSG), slowly digestible starch (SDS), resistant starch (RS), total starch(TS) and starch digestion rate index (SDRI). On the other hand, significant variation was observed in rapidly available glucose and rapidly digestible starch (RAG and RDS). Flavonoids, total phenolics and phytate contents varied significantly at different kneading time- speed combinations. Injera sensory quality was also significantly affected due to change in kneading conditions. Kneading condition 5 (3 min at speed 6) has the highest injera overall acceptability while kneading condition 9 (7 min at speed 12) had the lowest. In addition to kneading conditions, absit preparation (water to fermented dough ratio) was also found to affect the quality of tef injera. Absit # 3 made from 100 ml of fermented dough and 900 ml of water had the highest injera overall acceptability while, the lowest was observed on Absit # 4 made from 300 ml of fermented dough and 100 ml of water. In conclusion, both kneading and absit preparation significantly influenced starch hydrolysis, flavonoids, total phenolics and phytate contents as well as sensory quality of injera.Ministerio de Economía y Competitividad - FEDER (AGL2015- 63849-C2-2-R)Junta de Castilla y León) - FEDER (Project VA072P17

Lipase inactivation kinetics of tef flour with microwave radiation and impact on the rheological properties of the gels made from treated flour

Producción CientíficaIn recent years, many efforts are being made to produce tef-based food for its nutritive and health-promoting advantages. Tef grain is always whole milled because of its tiny grain size and whole flours contain bran (pericarp, aleurone, and germ) where major non-starch lipids could be deposited along with the lipid-degrading enzymes: lipase and lipoxygenase. As lipoxygenase shows little activity in low moisture, the inactivation of lipase is the common objective for most heat treatments to extend the shelf life of flours. In this study, tef flour lipase inactivation kinetics via hydrothermal treatments assisted using microwaves (MW) were studied. The effects of tef flour moisture level (12%, 15%, 20%, and 25%) and MW treatment time (1, 2, 4, 6, and 8 min) on flour lipase activity (LA) and free fatty acid (FFA) content were evaluated. The effects of MW treatment on flour pasting characteristics and the rheological properties of gels prepared from the treated flours were also explored. The inactivation process followed a first-order kinetic response and the apparent rate constant of thermal inactivation increased exponentially with the moisture content of the flour (M) according to the equation 0.048·exp (0.073·M) (R2 = 0.97). The LA of the flours decreased up to 90% under the studied conditions. MW treatment also significantly reduced (up to 20%) the FFA level in the flours. The rheological study confirmed the presence of significant modifications induced by the treatment, as a lateral effect of the flour stabilization process.Ministerio de Ciencia e Innovación (PID2019-110809RB-I00/AEI/10.13039/501100011033)Junta de Castilla y León/FEDER VA195P2

Tef [Eragrostis tef (Zucc.) Trotter] variety determines viscoelastic and thermal properties of gluten-free dough and bread quality

Tef flour has been considered a good alternative raw material to improve the quality of gluten-free bread due to its attractive nutritional profile. The influence of tef variety (DZ-Cr-37, DZ-Cr-387 and DZ-01-99) and incorporation level (100, 75 and 50%) on rheological and thermal properties of maize starch-based gluten-free doughs, and their impact on bread characteristics was investigated. The addition of tef brought about a structuring effect of doughs leading to higher viscoelastic moduli and steady-state viscosities and to lower tan δ values and instantaneous and retarded compliances. These effects were magnified with the increase of tef level in the dough. Tef addition led to an increase in dough gelatinization temperature and a decrease of gelatinization enthalpy, especially in the case of DZ-01-99 variety. Tef incorporation at 50 and 75% level led to well-developed bread which volume and crumb grain properties were significantly affected by the tef variety. DZ-Cr-37 variety led to the highest bread volume but to a less regular and poorer crumb grain. However, the bread made with 100% DZ-Cr-37 reached the highest overall acceptance score. This work demonstrates tef flour incorporation up to 100% level is a feasible procedure to reach technologically viable and sensory acceptable gluten-free bread.Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (AGL2015-63849-C2-2-R and AGL2015-63849-C2- 1-R)Spanish Ministerio de Ciencia e Innovación (PID2019- 110809RB-I00)Junta de Castilla y León/FEDER VA072P1

Impact of the variety of tef [Eragrostis tef (Zucc.) Trotter] on physical, sensorial and nutritional properties of gluten-free breads

Producción CientíficaTef is currently being incorporated into a wide range of foodstuff due to its high nutritional profile. This study tries to fill the information gap on the effect of tef varieties on physico-chemical, nutritional and sensorial quality of gluten-free bread. Maize starch replacement at 50, 75 and 100 g/100 g level by tef flour from three Ethiopian varieties (DZ-Cr-37, DZ-Cr-387 and DZ-01-99) resulted in viable gluten-free breads with acceptable sensory properties, higher mineral content and lower glycemic response. Tef cultivar type and blending level significantly affected bread quality. The 50% and 75% substitution levels and the DZ-Cr-37 variety led to the highest bread volumes with the lowest firmness. Breads made with DZ-01-99 variety were darker and with more reddish crust and crumb hues than those made with the other varieties. Breads from 100% DZ-Cr-37 achieved the highest hedonic scores for color, odor, taste and texture. The Ca, Fe and Mg contents of the breads made with 100% tef were 13, 40 and 30 times, respectively, higher than those of the control bread (100% maize starch), indicating tef could be used as an excellent source of these important minerals. In addition, the rapidly digestible starch content decreased up to 28% in breads fortified with tef flour.Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (grant PID2019-110809RB-I00)Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (grant VA195P20