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

All rights reserved. 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.The research was supported by the Spanish Institutions Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) (Projects AGL2012-35088 and AGL2011-22669), and Comunidad de Castilla y León (Project VA252A12-2). W. Abebe thanks the Agencia Española de Cooperación Internacional (AECID) grant and Ethiopian Institute of Agriculture for providing the tef cultivars flours.Peer Reviewe

Influence of acidification on dough viscoelasticity of gluten-free rice starch-based dough matrices enriched with exogenous protein

The impact of acid incorporation (acetic+lactic, 0.5%) into rice starch-based doughs enriched with different proteins (egg albumin, calcium caseinate, pea protein and soy protein isolates) at different doses (0, 5 and 10%) has been investigated on dough viscoelastic and pasting profiles. Oscillatory (stress and frequency sweeps) and creep-recovery tests were used to characterize the fundamental viscoelastic behaviour of the doughs, and thermomechanical assays were performed to assess dough viscometric performance. Supplementation of gluten-free doughs with proteins from vegetal sources led to more structured dough matrices (higher viscoelastic moduli and steady viscosities, and lower tan. ¿, instantaneous and retarded elastic compliances) effect being magnified with protein dose. Acid addition decreased these effects. Incorporation of proteins from animal source resulted in different viscoelastic behaviours according to the protein type, dosage and acidification, especially for casein. Acidification conferred lower dough deformation and notably higher steady viscosity and viscoelastic moduli for 5 %-casein-added dough. Protein-acid interaction favoured higher viscosity profiles, particularly for doughs with proteins of vegetable origin and lower dosage. Dough acidification decreased the pasting temperatures and the amylose retrogradation. Acidification of protein-enriched rice-starch doughs allowed manipulation of its viscometric and rheological properties which is of relevant importance in gluten-free bread development.Authors gratefully acknowledge the financial support of the Spanish Institutions Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) (Projects AGL2012-35088 and AGL2011-22669) and Comunidad de Castilla y León (Project VA252A12-2).Peer Reviewe

Significance of healthy viscous dietary fibres on the performance of gluten-free rice-based formulated breads

The impact of associated viscous dietary fibres (hydroxypropylmethylcellulose semi-firm – SFE- and weak – NE-gel forming, and barley ß-glucan, BBG) incorporated at different amounts (1.6–7.5%, flour basis) into gluten-free rice-based dough formulations on the breadmaking performance and staling behaviour of hydrated (70–110%, flour basis) fibre-flour composite blends has been investigated. Single BBG addition fails to mimic gluten visco-elasticity properly, but simultaneous incorporation of either SFE or NE contributes to bread improvement in terms of bigger volume and smoother crumb. 3.3 g of BBG (70% purity) and 104 mL of water addition to 100 g rice flour provided sensorially accepted breads (7.6/10) with a theoretical ß-glucan content of 1.24 g per 100 g GF bread that would allow a daily ß-glucan intake of 3 g provided a bread consumption of 240 g day−1. Complementary tests should be carried out to know the amount and molecular weight of ß-glucan in the final bread before assuring the nutritional benefit of this addition.Financial support of the Spanish Institutions Ministerio de Economía y Competitividad (Projects AGL2012-35088 and AGL2011-22669) and Comunidad de Castilla y León (Project VA252A12-2)Peer reviewe

Effect of tef [Eragrostis tef (Zucc.) Trotter] grain flour addition on viscoelastic properties and stickiness of wheat dough matrices and bread loaf volume

Currently, consumers’ preference toward baked goods with additional (functional and nutritional) value is increasing, leading food industries to look at natural nutrient-dense alternatives like tef grain. Impact of tef grain flour incorporation (three Ethiopian varieties: DZ-01-99, DZ-Cr-37 and DZ-Cr-387 at 10, 20, 30 and 40 % levels) on dough viscoelastic profiles and stickiness of wheat-based dough matrices were investigated. Oscillatory and creep–recovery tests together with dough stickiness were performed. Incorporation of tef flours affected the structure of the dough matrices visibly by reducing viscoelastic moduli, and the maximum stress doughs can tolerate before its structure is broken and increased dough instantaneous and retarded elastic compliances. Effect of dose was not always significant in the parameters measured. Tef grain flour incorporation up to 30 % level led to breads with higher loaf volume than the control associated with optimal consistency and higher deformability of doughs. Higher tef doses increased dough stickiness. This will affect dough handling and shaping/flattening to get continuous strands or thin sheets. On average, the DZ-Cr-37-supplemented doughs exhibited higher elastic and viscous moduli, lower compliances and higher steady-state viscosity and led to significantly lower loaf bread volumes. Hence, based on dough viscoelastic and stickiness properties, incorporation of DZ-01-99 and DZ-Cr-387 into wheat flour-based formulations could be more preferable.This research was supported by the Spanish Institutions Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) (Projects AGL2012-35088 and AGL2011-22669) and Comunidad de Castilla y León (Project VA252A12-2). W. Abebe thanks the Agencia Española de Cooperación Internacional grant and Ethiopian Institute of Agricultural Research for providing the flours of the tef varieties. Marina Villanueva thanks the Junta de Castilla y León doctorate grant.Peer reviewe

Acidification of protein-enriched rice starch doughs: effects on breadmaking

The impact of acid incorporation (acetic + lactic, 0.5 %) into rice starch-based doughs enriched with different proteins (egg albumin, calcium caseinate, pea and soy protein isolates) at different doses (0, 5 and 10 %) was investigated on dough proofing and thermal properties, and bread quality evaluated from physical and sensory measurements. Proteins from vegetable sources led to breads with lower-specific volume and harder crumb, effects being magnified with protein dose and reduced with acid addition. Incorporation of proteins from animal source resulted in different behaviours according to the protein type, dosage and acidification. Protein addition increased the dough pH and total titratable acidity and reduced the impact of acid addition on dough acidity. Albumin-added doughs had significantly higher temperature of gelatinization than most of the other supplemented doughs, while vegetable proteins led to significantly lower gelatinization enthalpy than the control dough. Acid addition affected dough proofing and significantly improved the volume and texture of protein-enriched breads without detriment of either odour or taste.The research was supported by the Spanish Institutions Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) (Projects AGL2012-35088 and AGL2011-22669), and Comunidad de Castilla y León (Project VA252A12-2).Marina Villanueva thanks the Junta de Castilla y León doctorate grantPeer Reviewe

Physical modification caused by acoustic cavitation improves rice flour bread-making performance

Producción CientíficaAcoustic cavitation has been shown to cause physical damage and partial starch depolymerization in ultrasound-treated flours. However, the promising effects of this modification on bread-making performance of gluten-free flour are still unexplored. Based on this hypothesis, sonicated rice flour (2–20 min) was used to replace 30% native flour in the control formulation of gluten-free bread. Breadmaking performance was characterized by doughs' pasting, thermal, and rheological properties, and physical quality of breads. Ultrasonication time presented a direct correlation with particle fragmentation. Doughs’ rheology presented reduced tan(δ)₁ values (up to −11%) and improved recovery after the application of stress (up to +14%), denoting an enhanced elastic behavior with respect to the control dough. Rheo-fermentative tests demonstrated that ultrasonication accelerated the generation of CO2 and its retention within the dough structure, as consequence of eased accessibility of yeast to simpler sugars after starch depolymerization. The small-size particles (∼10 μm) in ultrasonicated flours seem to have enhanced their Pickering emulsifying ability and led to breads with higher specific volumes (up to 24%), softer crumbs, and delayed hardening during storage. Ultrasonication, a low-cost technology, has been shown to significantly improve the fermentative and viscoelastic behavior of rice flour dough and its breadmaking performance.Ministerio de Ciencia e Innovación (PID 2019-110809RB-I00/AEI/10.1303/501100011033)Junta de Castilla y León/FEDER (VA195P20

Effect of Microwave Radiation Pretreatment of Rice Flour on Gluten-Free Breadmaking and Molecular Size of β-Glucans in the Fortified Breads

Producción CientíficaCereal β-glucan concentrates can be used in gluten-free breads to improve dough handling properties and quality of final products as well as to enhance their nutritional value; however, the presence of endogenous β-glucanases in rice flour, in combination with prolonged mixing, fermentation and proofing time, can cause a substantial reduction in β-glucan molecular weight, affecting detrimentally their efficacy for bioactivity. In this study, microwave (MIWA) heating was applied to the rice flours before breadmaking at different flour water contents (13-25%) and treatment times (0- 4min) to reduce β-glucanase activity. Gluten-free breads made from the MIWA treated rice flours were fortified with oat β-glucan concentrate to enhance their nutritional profile. The molecular weight of added β-glucan in the final products increased with increasing both flour water content and time of MIWA treatment, reflecting the magnitude of residual β-glucanase activity in the flour. Pretreatment with MIWA radiation for 4 min of the rice flour tempered at 25% moisture resulted in negligible residual β-glucanase activity and preserved to a great extent the molecular weight of β-glucans in the enriched breads. End-product quality was not affected by flour MIWA pretreatment, and even a slightly higher loaf specific volume was noted for breads made from the MIWA -treated flours (4min MIWA at 25% moisture content) compared to that of untreated flour. These findings can contribute to the improvement of nutritional value of rice-based gluten-free breads for celiac consumers as well as of any β-glucan containing yeast-leavened bakery product without altering its sensorial attributes. Additional studies are still required for further evaluation of the effect of more intense microwave treatment on rice flour and its application on breadmaking

Effect of b-glucan molecular weight on rice flour dough rheology, quality parameters of breads and in vitro starch digestibility

Producción CientíficaThe study aimed at investigating the effects of molecular weight(peak molecular weight, Mp, 83, 192 and 650 kDa) and level (1.3, 2.6 and 3.9 g/100 g flour basis) of enriched in β-glucan (BG) concentrates (from oat and barley) added into rice flour gluten-free (GF) doughs on their viscoelastic and pasting properties, as well as the quality parameters of bread and the in vitro starch digestibility. A purification process of a commercial BG concentrate, followed by an acid hydrolysis step were employed to reduce the content of interfering excipients (e.g. maltodextrins) and obtain preparations with a range of molecular weights. BG-enriched GF breads of improved quality, that can fulfil the EFSA claims (ingest of 3 g of BG per day with a daily bread intake of ∼200 g of bread), were obtained, exhibiting slower starch digestibility (in vitro assay) dependent on the molecular weight and concentration of BG. With the higher Mp BG used, showing the largest impact on dough rheology characteristics and having a greater potential for health benefits, higher specific volume and lower bread crumb hardness were noted among the GF breads. The medium and lowest Mp BG also had an influence on dough rheological behavior and bread quality attributes. The rapidly available glucose of the bread decreased from 81g/100 g to 72g/100 g as result of the 3.9g/100 g addition of the highest Mp BG in the GF formulations

Rice flour physically modified by microwave radiation improves viscoelastic behavior of doughs and its bread-making performance

Producción CientíficaThe physical modification of rice flour by heat-moisture treatment assisted by microwave radiation and its effect on the rheological and pasting properties of gluten-free doughs and the physical quality of their resulting bread was investigated. Two levels of flour initial moisture content, 20% (MW-20%) and 30% (MW-30%) and two levels of its addition (30% and 50%) to the dough were evaluated to assess the potential of the physical treatment to modify dough viscoelasticity and bread-making ability. MW-30% treated rice flour showed the most notable results. It provided enhanced dough viscoelasticity vs the control (100% native rice flour), increasing the dough G1′ modulus up to 69% and 135% for the treated flour additions of 30% and 50% of MW-30% respectively. The treated flour increased the resistance of doughs to deformation and enhanced their elastic behavior and recovery capacity up to 170% when compared to the control dough. The major effects on pasting parameters were also obtained for the doughs formulated with MW-30% flour at the maximum substitution level (50%). It delayed the pasting temperature, decreased the peak, trough and final viscosities with respect to the control dough. Both MW-treated rice flours (MW-20% and MW-30%) led to bread with higher-specific volume, softer crumb and delayed staling. The MW assisted heat moisture treatment of rice flour seems to be a valuable procedure to improve the viscoelastic behavior and bread-making performance of gluten-free doughs.Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) - AGL2015-63849-C2-2-RJunta de Castilla y León and FEDER - VA072P17European Commission for the Individual Fellowship Grant - 706102–BreadForAl

Microwave absorption capacity of rice flour. Impact of the radiation on rice flour microstructure, thermal and viscometric properties

Producción CientíficaThe microwave radiation thermal treatment of rice flour was studied and its impact on physical and structural characteristic in relation to the initial moisture content (IMC) (20% and 30%) was evaluated. To explain the fundamentals of observed changes the microwave radiation absorption capacity of flour as well as temperature and moisture change during the treatment were evaluated. The flour particle morphological structure as well as crystallinity/amorphous region ratio changed after the treatment. The flour thermal properties also altered revealing IMC significant impact on the gelatinization temperature, that raised up to 3 C, and the amylopectin retrogradation extent that increased up to a 7% in the most intense microwave-treated flours with respect to the native flour. Lower peak, setback and breakdown viscosities - that decreased with respect to the native flour up to 42%, 34% and 86% respectively-and higher pasting temperatures -that increased up to 10 ºC- were also observed. An exceptional microwave irradiation efficiency resulting in rice flour physical changes in significantly shorter times, 4e8 min, than conventional heat-moisture treatment processes was concluded.Ministerio de Economía, Industria y Competitividad (Proyect AGL2015-63849-C2-2-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA072P17