Rheological and textural properties of tef [Eragrostis tef (Zucc.) Trotter] grain flour gels

Chitosan/teff flour active films incorporated with citric acid and beetroot leaf extract: Physicochemical properties and mathematical modeling of phenolic release

Active compounds are integrated into food packaging films to enhance their food protection capabilities. Understanding the release of these components in films, particularly in crosslinking scenarios, is crucial. This study aimed to mathematically model the release of phenolic compounds from chitosan/teff flour films to understand how active compounds gradually release. Moreover, it was aimed to study the effects of incorporation of beetroot leaf extract and citric acid crosslinking. The collective observations, encompassing increased density and thermal stability, alongside concurrent reductions in moisture content, water solubility, water vapor permeability and swelling index following citric acid addition, strongly suggested the presence of crosslinking. Applying Fick's law and the finite element method revealed a substantial influence of the crosslinking agent on diffusion coefficients. The model exhibited strong agreement with experimental data, as reflected in low root mean square error values ranging from 3.02 to 8.50 mmol/m3 for films. Furthermore, the influence of citric acid crosslinking on the release of TPC was evident, as indicated by a decrease in average diffusion coefficient values from 3.499 × 10-13 m2 s-1 to 1.770 × 10-13 m2 s-1 with the formula with 1.5 % citric acid and 0.5 % beetroot leaf extract. This showcases the impact of various parameters on controlled release in food packaging.

Microwave radiation induces modifications in the protein fractions of tef flours and modulates their derived techno-functional properties

The impact of microwave (MW) treatments on the structure, solubility, and techno-functional properties of the proteins in starchy matrices is still poorly understood. This study aimed to investigate the effects of MW intensity by applying 1, 2, and 6 min of radiation on two tef flour varieties moistened at 15 % and 25 %. The fractionation method recovered ∼83 % of the total protein content in untreated flours. The interaction between treatment time and moisture content (MC) significantly influenced the extraction of protein fractions. Samples treated at 25 %MC showed significant reductions in albumins (up to -74 %), globulins (up to -79 %), and prolamins (up to -32 %). The SDS-extractable proteins of both tef flours presented similar molecular weights (12-100 kDa). SDS-PAGE analysis revealed decreased band intensity in MW-treated samples compared to untreated flours, and confocal analysis showed changes in the native state of proteins in treated samples. Shorter treatments at low MC significantly improved the emulsifying stability of tef flours, particularly in brown tef flour, with an enhancement of up to 203 %. The hydration properties significantly increased in flours treated at 25 %MC for 6 min. Pearson correlation analysis demonstrated the influence of treatment time and MC on protein recovery and functional properties of tef flours.

Hydro- and aerogels from quince seed gum and gelatin solutions

The composite hydro/aerogels were designed using gelatin and quince seed gum (QSG) at total polymer concentration (TPC) of 1, 1.5 and 2% and gelatin/QSG ratio of 1:0, 1:0.5 and 1:1. The gel syneresis decreased significantly with increase in TPC and QSG. Although, hydrogels with 2% TPC had remarkably higher gel strength and elasticity than 1% TPC ones, the addition of high levels of QSG to the gelatin (i.e., gelatin/QSG 1:1) led to a decrease in its gel strength (∼0.97-fold) and elasticity (∼3,463-fold). The temperature-sweep test showed higher melting points in gelatin/QSG hydrogels (>60 °C) compared to the gelatin ones (∼58 °C). Additionally, QSG addition to the gelatin led to more porous networks with higher gel strength, thermal stability, and crystallinity, as observed by scanning electron microscopy, differential scanning calorimetry, and X-ray diffractometer. Therefore, QSG could be used as a natural hydrocolloid to modify gelatin functionality.

Genetic diversity and population structure of selected tef core germplasm lines based on microsatellite markers

BACKGROUND

Tef is an indigenous and important food, feed, and cash crop for smallholder Ethiopian farmers. Knowledge of the natural genetic composition of the crop provides the option to further exploit its genetic potential through breeding. However, there are insufficient reports on the genetic variability of Ethiopian tef using a medium-throughput marker system. Hence, the current study was designed to evaluate the genetic variability of released and core germplasm that was collected earlier.

METHODS AND RESULTS

Eighty-one tef genotypes collected from eight Ethiopian ecological zones and released varieties were targeted using 14 SSR markers. The study yielded a total of 122 alleles across the entire locus and population. The molecular variance analysis indicated the existence of large genetic differentiation (FIS and FIT = 0.87), with 86% and 13% of the total variation accounted for among genotypes within the population and across all genotypes used for this study, respectively. However, low genetic differentiation among the populations (FST = 0.014, which accounts for 1%) was observed. Multivariate analyses such as clustering and PCoA did not cluster genotypes into distinct groups according to their geographical areas of population. This is presumably due to gene flow among populations.

CONCLUSION

In conclusion, our findings show that there is significant genetic diversity within populations, particularly in the Jimma, Tigray, and released varieties, as well as the presence of private alleles and heterozygosity. The study also indicates the existence of genotypic admixture in the studied materials. The identification of private alleles and their differentiation will be helpful in selecting breeding materials and creating breeding plans.

Gel Rheological Properties and Storage Texture Kinetics of Starches Isolated from Anchote (Coccinia abyssinica (Lam.) Cogn.) Cultivars

Anchote is a tuber crop indigenous to Ethiopia. Starch hydration properties and important gel characteristics which include: color, gel rheological properties (at 2, 4, 6, 8, and 10% starch:water w/w) and gel texture evolution (at 10% starch:water w/w), during 0 to 192 h storage (at 4 °C), of anchote starches isolated from four anchote cultivars (Desta 01, Desta 24, white and red) were evaluated and compared with potato and cassava starches (PS and CS). The lightness (L*) and whiteness scores of the anchote starch ranged up to >95, with slight differences among the cultivars, making them pure starches. Swelling power (SP) and water solubility index (WSI) of the anchote starches increased with increasing cooking temperature (40, 50, 60, 70, 80 and 90 °C), and their rate of increase varied significantly with the control starches, as follows: CS < anchote starches < PS. Anchote starch gels resisted higher stresses before breaking their structure and showed higher elasticity with lower (tan δ)1 values than PS and CS gels. They also had greater viscoelastic moduli even at lower concentrations than the PS and CS gels, and their stability increased with increasing concentration. The study of the gels' texture evolution during storage revealed that anchote starch gels had significantly higher (≥40%) initial and final (after 192 h) hardness and were less adhesive than the PS gel. Despite some significant differences in the studied starch gel quality parameters among the starches from the anchote cultivars, the results suggested their promising potential as additional new materials in the development of food products, specifically as a functional ingredient for the formulation of gel-like products.

Changes on Techno-Functional, Thermal, Rheological, and Microstructural Properties of Tef Flours Induced by Microwave Radiation-Development of New Improved Gluten-Free Ingredients

Tef [Eragrostis tef (Zucc.) Trotter] flour is a gluten-free cereal rich in fiber, minerals, vitamins, and antioxidants, which offers a promising alternative for new food development. This study investigated the effect of microwave radiation (MW) on the techno-functional, thermal, rheological and microstructural properties of tef flours. White and brown tef grains were milled and microwaved at different moisture contents (MC) (15%, 20% and 25%) for a total irradiation time of 480 s. The morphological structure of tef flours was affected by MW treatment, and its particle size and hydration properties increased after the treatment. Lower peak, breakdown, and setback viscosities, up to 45%, 96%, and 67% below those of the control (untreated) samples, and higher pasting temperature, up to 8 °C in the 25% MC samples, were observed. From FTIR analysis a disruption of short-range molecular order was concluded, while DSC confirmed an increased stability of starch crystallites. Rheological analysis of the gels made from the treated samples revealed that MW had a structuring and stabilizing effect on all samples, leading to higher viscoelastic moduli, G' and G″, and the maximum stress the gels withstood before breaking their structure, τ_max. The MC of the flours during the MWT drove the modification of the techno-functional properties of the tef flours and the gel rheological and thermal characteristics. These results suggest that MW-treated tef flours are potential ingredients for improving the technological, nutritional and sensory quality of food products.

Lipase Inactivation Kinetics of Tef Flour with Microwave Radiation and Impact on the Rheological Properties of the Gels Made from Treated Flour

In 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.

Impact of the Variety of Tef [Eragrostis tef (Zucc.) Trotter] on Physical, Sensorial and Nutritional Properties of Gluten-Free Breads

Tef 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.

Significance of milling methods on brown teff flour, dough, and bread properties

Teff (Eragrostis tef) has gained wide popularity of late mainly attributed to its gluten-free nature catering the needs of gluten sensitive population. The higher water absorption capacity and gelling properties of teff flour promote its food applications, especially in the baking sector. The nutritional and sensorial properties of teff flour have been studied by incorporating with wheat flour at different proportions, but no study has reported the impact of various milling methods on the rheological and bread-making properties of teff flour. In this regard, the present study is envisaged to assess the physical, rheological and bread-making properties of teff flour acquired over roller, hammer and pin milling. Among the milling methods, the distribution of particles was more uniform in case of roller mill, while finer particles were obtained for the pin milled flour fractions with 60% of the sample falling below 90 μm. It was observed that the protein, crude fiber and crude fat contents for all the flours were on par with each other irrespective of the milling method. Whereas, the pasting properties varied significantly between the flours obtained from different milling methods. It was observed that the pin milled flour bread was superior in quality owing to its higher loaf volume (331.67 cm³ ) with lower hardness value (5.99 N). The present study indicates the fact that, pin mill could be more suitable for milling brown teff grains owing to the better pasting and bread making properties. This article is protected by copyright. All rights reserved.

Techno-Functional and Gelling Properties of Acha (Fonio) (Digitaria exilis stapf) Flour: A Study of Its Potential as a New Gluten-Free Starch Source in Industrial Applications

Fonio (Digitaria exilis Stapf) is an ancient African cereal that represents a rich source of carbohydrate, fat, fiber, vitamins, minerals, and sulfur-containing amino acids. Processing and utilization of fonio require adequate knowledge of its structural, chemical, and nutritional characteristics. The present work evaluates the structural, techno-functional, and gelling properties of fonio and compares them to other major gluten-free cereals (rice, maize, sorghum, and millet). Fonio flour presented significantly higher water absorption index and swelling power, while it scored a lower water solubility index than the reference flours. The pasting viscosity profile of fonio was similar to that of rice, with equivalent peak viscosity but a breakdown viscosity 24% lower than rice, indicative of higher stability and resistance to shearing and heating. Rheological properties demonstrated that fonio generates gels with remarkably strong structures. At 15% concentration, fonio gel withstood stress 579% higher than those observed in the reference flours without breaking its structure. Fonio flour presented the highest gelatinization enthalpy (11.45 J/g) and a narrow gelatinization temperature range (9.96 °C), indicative of a better-packed starch structure than the other analyzed flours. The texture of the gels made with fonio showed higher firmness over the evaluated period. These combined results suggest that fonio is a suitable ingredient for gel-like food formulations.

Nutritional Composition and Health Benefits of Teff (Eragrostis tef (Zucc.) Trotter)

Teff (Eragrostis tef (Zucc.) Trotter) (Poaceae) is an annual crop with a very tiny grain. The crop is mainly cultivated in Ethiopia and Eritrea where it is used in preparing a pancake-like staple food called injera. Teff grain is the smallest of all whole flour grains in the world with a length of about 1.0 mm and a width of about 0.60 mm. The popularity of the crop is rapidly increasing throughout the world because of its attractive nutritional and functional properties. Thus, the crop is being successfully introduced and cultivated in many parts of the world including the USA, Canada, Australia, Switzerland, and the Netherlands. The growing global demand for the grain is due to its gluten-free nature, high level of essential amino acids (EAA), high mineral content, low glycemic index (GI), high crude fiber content, longer shelf life, and slow staling of its bread products compared to that of wheat, sorghum, rice, barley, and maize. The grain is linked to several health benefits including prevention and treatment of diseases such as celiac disease, diabetes, and anemia. These call for huge research opportunities to explore the nutritional and functional properties of the grain.

Application of Autoclave Treatment for Development of a Natural Wheat Bran Antioxidant Ingredient

The study evaluated the effect of autoclaving as a hydrothermal treatment on the quality and bioactivity of wheat bran (WB) with the objective of producing a natural ingredient with enhanced healthy properties. Nutritional, antioxidant, techno-functional and sensorial parameters were studied, and temperatures of 100, 115 and 130 °C were explored. Of these, 130 °C was found to be the best treatment, resulting in an ingredient with high storage stability, antioxidant properties, a four-fold increase in the concentration of free ferulic acid (compared with non-treated WB), and increased content of apigenin-6-C-arabinoside-8-C-hexoside, a flavonoid with reported antioxidant and antifungal properties. On the other hand, the autoclave treatment enhanced water absorption capacity and reduced WB pasting viscosity, mainly at higher temperature (130 °C), which would allow incorporation of the treated WB in liquid matrices such as juices, soups or milkshakes, among others. Although the glycemic index (GI) of the autoclaved samples increased, the use of intermediate particle size of 106 to 300 µm could contribute to the reduction of the glycemic load.

Effect of feed components on quality parameters of wheat-tef-sesame-tomato based extruded products

Wheat flour is one of the principal ingredients in extruded wheat products. Wheat-based extruded products have relatively low protein and high gluten contents as well as a high glycemic index. Incorporation of nutrient-rich supplements could overcome those limitations. A D-optimal statistical experimental design was used to develop high-value and nutrient-rich extruded products by supplementing wheat flour (WF), with tef flour (TF), sesame protein concentrate (SPC) and tomato powder (TM). Effects of feed compositions on physical and functional properties of the extruded products were evaluated and modeled using an artificial neural network (ANN). SPC contributed to elevate the protein and simultaneously lower the carbohydrate content of the extruded products while TF and TM contributed to improving crude fiber and antioxidant properties. Evaluated physicochemical properties were adequately predicted by the ANN models (R2 = 0.979-0.998) with root mean square error of less than 0.008. Physical properties and sensorial evaluation correlated well and revealed that TF, SPC and TP addition to wheat flour produced distinct extruded products rich in protein and antioxidants with lowered carbohydrate and gluten contents.

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.

In vitro starch hydrolysis and estimated glycemic index of tef porridge and injera

The aim of this study was to investigate the in vitro starch digestibility of injera and porridge from seven tef varieties and to estimate their glycemic index. The total starch, free glucose, apparent amylose, resistant, slowly digestible and rapidly digestible starches of the varieties ranged between 66 and 76, 1.8 and 2.4g/100g flour dry matter (DM), 29 and 31%, 17 and 68, 19 and 53, 12 and 30g/100g starch DM, respectively. After processing into injera and porridge, the rapidly digestible starch content increased by 60-85% and 3-69%, respectively. The estimated glycemic index of porridge and injera of the varieties ranged 79-99 and 94-137 when estimated based on model of Goni et al. (1997) whereas from 69 to 100 and 94 to 161, respectively based on Granfeldtet al. (1992). Tef porridge and injera samples studied here can be classified as medium- high GI foods, not to be considered as a proper food ingredient for diabetic people and patients in weight gain control.

Impact of variety type and particle size distribution on starch enzymatic hydrolysis and functional properties of tef flours

Tef grain is becoming very attractive in the Western countries since it is a gluten-free grain with appreciated nutritional advantages. However there is little information of its functional properties and starch digestibility and how they are affected by variety type and particle size distribution. This work evaluates the effect of the grain variety and the mill used on tef flour physico-chemical and functional properties, mainly derived from starch behavior. In vitro starch digestibility of the flours by Englyst method was assessed. Two types of mills were used to obtain whole flours of different granulation. Rice and wheat flours were analyzed as references. Protein molecular weight distribution and flour structure by SEM were also analyzed to justify some of the differences found among the cereals studied. Tef cultivar and mill type exhibited important effect on granulation, bulking density and starch damage, affecting the processing performance of the flours and determining the hydration and pasting properties. The color was darker although one of the white varieties had a lightness near the reference flours. Different granulation of tef flour induced different in vitro starch digestibility. The disc attrition mill led to higher starch digestibility rate index and rapidly available glucose, probably as consequence of a higher damaged starch content. The results confirm the adequacy of tef flour as ingredient in the formulation of new cereal based foods and the importance of the variety and the mill on its functional properties.