Sorghum Flour Characterization and Evaluation in Gluten-Free Flour Tortilla

Sorghum Flour Features Related to Dry Heat Treatment and Milling

Heat treatment of sorghum kernels has the potential to improve their nutritional properties. The goal of this study was to assess the impact of dry heat treatment at two temperatures (121 and 140 °C) and grain fractionation, on the chemical and functional properties of red sorghum flour with three different particle sizes (small, medium, and large), for process optimization. The results showed that the treatment temperature had a positive effect on the water absorption capacity, as well as the fat, ash, moisture and carbohydrate content, whereas the opposite tendency was obtained for oil absorption capacity, swelling power, emulsion activity and protein and fiber content. Sorghum flour particle size had a positive impact on water absorption capacity, emulsion activity and protein, carbohydrate and fiber content, while oil absorption capacity, swelling power and fat, ash and moisture content were adversely affected. The optimization process showed that at the treatment temperature at 133 °C, an increase in fat, ash, fiber and carbohydrate content was experienced in the optimal fraction dimension of red sorghum grains. Moreover, the antioxidant performance showed that this fraction produced the best reducing capability when water was used as an extraction solvent. Starch digestibility revealed a 22.81% rise in resistant starch, while the thermal properties showed that gelatinization enthalpy was 1.90 times higher compared to the control sample. These findings may be helpful for researchers and the food industry in developing various functional foods or gluten-free bakery products.

Sorghum Flour Application in Bread: Technological Challenges and Opportunities

Sorghum has a long history of use in the production of different types of bread. This review paper discusses different types of bread and factors that affect the physicochemical, technological, rheological, sensorial, and nutritional properties of different types of sorghum bread. The main types of bread are unleavened (roti and tortilla), flatbread with a pre-ferment (injera and kisra), gluten-free and sorghum bread with wheat. The quality of sorghum flour, dough, and bread can be improved by the addition of different ingredients and using novel and traditional methods. Furthermore, extrusion, high-pressure treatment, heat treatment, and ozonation, in combination with techniques such as fermentation, have been reported for increasing sorghum functionality.

Characterization of Sorghum Processed through Dry Heat Treatment and Milling

Sorghum grain nutritional quality can be enhanced by applying dry heat treatments. The purpose of this study was to investigate the effects of dry heat treatment at two temperatures (121 and 14 °C) with three fractionation factors (S fraction < 200 μm, M fraction 200–250 μm and, L fraction > 300 μm) on sorghum flour chemical and functional properties, to optimize processes by means of a desirability function, and to characterize the optimal products. Treatment temperature negatively affected oil- and water-absorption capacity, protein and moisture contents, while the opposite trend was obtained for hydration capacity, swelling power, emulsifying properties, fat, ash, and carbohydrate content. Sorghum flour fractions positively influenced the hydration and water-retention capacities, emulsifying properties, and protein and carbohydrate content, while oil absorption, swelling power, fat, ash, and moisture were negatively affected. The optimal processing determined for each fraction was heat treatment at 121.00 °C for S fraction, 132.11 °C for M, and 139.47 °C for L. Optimal product characterization revealed that the color, bioactive properties, and protein and starch structures of the optimal samples had changed after heat treatment, depending on the fraction. These findings could be helpful for the cereal industry, since sorghum flour could be an alternative for conventional crops for the development of new products, such as snacks, baked goods, and pasta.

Effects of Dry Heat Treatment and Milling on Sorghum Chemical Composition, Functional and Molecular Characteristics

This study aimed to highlight the effects of grains dry heat treatment, flour particle size and variety on sorghum flour nutritional, functional, and molecular characteristics. The results obtained showed that dry heat treatment led to fat, fiber and water absorption capacity increase, while the moisture, protein, ash, water retention capacity, solubility index, foaming capacity, and FT-IR absorption bands characteristic to phytic acids decreased with temperature applied raised. Particle size reduction determined lower protein, solubility index, and emulsifying activity and higher fat content, oil absorption capacity, swelling power, and foaming capacity. White sorghum flour fractions presented lower protein content, except when they were treated at 140 °C, lower carbohydrates and fibers and higher fat content compared to those made of red sorghum. Moderate significant correlations (p < 0.05) were observed between some of the functional properties and proximate composition of flours. Thus, both dry heat treatment conditions and particle size exerted significant influences of sorghum flour chemical and functional properties. These results showed the importance of particle size and dry heat treatment on sorghum flours functionality, being helpful for further optimizations and choices for bakery products use.

The effect of drought stress of sorghum grains on the textural features evaluated using machine learning

This study aimed to determine the discriminatory power of textural features to differentiate the sorghum grains subjected to normal, mild deficit, and severe deficit irrigation. The studies were carried out with the use of image processing, discrimination analysis, analysis of variance and cluster analysis using the selected texture parameters calculate for images from individual color channels L, a, b, R, G, B, U, V, S, X, Y and Z. The results indicated that different levels of irrigation can discriminate the sorghum grain with an accuracy of up to about 100%. Most of the genotypes for each level of irrigation were different in the terms of values of textural features and formed separate homogeneous groups. Drought is one of the limiting factors contributing to a decrease in sorghum grain productivity and nutritional quality, especially when it is cultivated in a marginal area. Therefore, low-quality grains produced under water stress should be recognized before they enter into the food and feed chain. The application of image analysis based on textures of sorghum grain images proved to be useful for the discrimination of sorghum grains subjected to drought stress. The applied procedure provided the fast, objective results that may be applied in practice for screening distinguishing the sorghum grains with different irrigation levels.

Domestic Processing Effects on Antioxidant Capacity, Total Phenols and Phytate Content of Sorghum

Background:

Whole grains may reduce chronic disease risks and these benefits are related to food matrix components, especially phenolic acids. However, food processing may change the total phenol content and antioxidant capacity.

Objective:

This study aims to evaluate the effect of processing on the antioxidant capacity and total phenols, tannins and phytate contents in the sorghum grain of seven genotypes.

Methods:

Antioxidant capacity (AC), total phenolic content (TPC), tannins and phytate content were evaluated in unheated sorghum grains (USG), heated sorghum grains (HSG) and popped sorghum grains (PSG) of seven genotypes.

Results:

AC ranged from 66.5% to 92.9% in USG, decreased after PSG in all genotypes, and maintained after HSG, except for BRS 506. TPC and tannins were higher in BRS 305. PSG decreased tannin content in all genotypes. TPC of HSG was higher than the USG in BRS 310, BRS 305, BR 501 and BR 700 genotypes. PSG affected TPC content mainly in BRS 305 and BR 700. AC and tannins were especially affected by the popping conditions. There was no difference in the phytate content among all genotypes, which were maintained after HSG in BRS 506, BRS 305, BR 700 and CMSXS 136.

Conclusion:

AC, TPC, tannins and phytate content were affected by the processing conditions, however, those changes may be related to the compounds type and sorghum genotype.

Characterization of white and red sorghum flour and their potential use for production of extrudate crisps

In the human food industry, the wheat-free market sales have increased over the years due to awareness of wheat gluten allergy and celiac disease. Sorghum is a gluten-free grain with great potential to address shortcomings in this market. The aim of this study was to evaluate the milling process and flour quality of one white and one red sorghum varieties and evaluate extrusion as a potential process to produce sorghum crisps. The white and red sorghum grains were milled into flour in three production cycles. Flour quality was evaluated by determination of nutritional composition, pasting, and thermal profile. Extrusion processing of white and red sorghum flour was performed, and macrostructure of final product was evaluated. The white and red sorghum used in this study yielded similar flour content (P > 0.05). Chemical analyses revealed a higher protein and lower starch content for white sorghum than red sorghum flour (P < 0.05); however, their pasting properties did not differ. Initial and peak gelatinization temperatures were higher (P < 0.05) for red sorghum compared to white sorghum flour. Regarding particle size, white sorghum flour presented lower d10 and d50 compared to the red sorghum flour (P < 0.05). However, these differences did not impact the extrusion conditions, and white and red sorghum crisps had similar macrostructure characteristics. In conclusion, although differences in nutritional, thermal, and particle size properties were observed between the sorghum flours used in this study, changes in extrusion parameters were not needed in order to produce sorghum crisps with similar characteristics.

Physicochemical Properties and Resistant Starch Content of Corn Tortilla Flours Refrigerated at Different Storage Times

The tortilla is a foodstuff that has a short shelf-life, causing great losses to the industry. The objective of this work was to evaluate, for the first time, the physicochemical properties and resistant starch (RS) content of flours. These were obtained from nixtamalized corn tortillas made with traditional and industrial (commercial) methods, stored at 4 °C for 7, 15, and 30 days. The flours were characterized by measuring particle size distribution, color, water absorption index (WAI), water solubility index (WSI), viscosity, calcium, and RS content. Additionally, chemical proximate analysis, scanning electron microscopy (SEM), and thermal analysis were conducted. Storage at 4 °C increased the friability of tortillas and shifted the particle size distribution toward a greater content of coarse particles in corn tortilla flours. The commercial corn tortilla flours showed higher WAI and WSI values than the traditional corn tortilla flours. On the other hand, the traditional corn tortilla flours exhibited higher RS content values than commercial corn tortilla flours as well as peak viscosity. X-ray diffractograms revealed the presence of amylose-lipid complexes (RS5) in experimental samples. The thermograms evidenced three endotherms corresponding to corn starch gelatinization and melting of type I and type II amylose-lipid complexes.

Current applications of gluten-free grains - a review

The population of Americans suffering from celiac, gluten intolerance, and wheat allergy is 1 in every 14 people. Also, many are choosing gluten-free (GF) diets nowadays because of the perception that it is a healthier option for them. Therefore, in the last decade, the GF market in the US and all over the world has seen significant growth. Globally, GF product sales reached 4.63 billion USD in 2017, and are expected to reach 6.47 billion USD by 2023, a projected compound annual growth rate of 7.6%. Several grains like millet, corn, sorghum, and pseudocereals like amaranth, quinoa, and teff are the main ingredients for a gluten diet. Though most of them have a comparable nutrient profile as common grains, the main challenge to their acceptability is the quality departure from gluten-containing counterparts and imbalance nutrients that ensue when food processing aids like starch, gums, and enzymes are used. In this review, we profiled some of the common grains, their characteristics, functionality and the various food types they are used for. We also reviewed the impact of some of the current food processing aids like starch, hydrocolloids used for improving functionality, and processing techniques like extrusion suitable for making remarkable GF foods.

Hydroxypropyl Methylcellulose and Whey Protein Concentrate as Technological Improver in Formulation of Gluten-Free Protein Rich Bread

Wheat breads contains gluten protein that is responsible for the visco-elastic properties of dough. There has recently been an increase in the prevalence of gluten-related disorders including celiac disease and non-celiac gluten sensitivity. Therefore, this study has been designed for improving bread production for gluten-free bread (sorghum and potato starch) using hydroxypropyl methylcellulose (HPMC) and whey protein concentrate (WPC-70) as technological improver and optimizing it using response surface methodology (RSM). RSM was used to investigate the influence of predictor variables (HPMC and WPC-70) on bread quality in terms of crust and crumb texture and color, flavor, porosity and overall acceptability. The HPMC level varies from 2- 3% and WPC-70 from 12-15%. Quadratic models are developed to fit with experimental data. The predictor variables had desirable effect on all the responses. Finally, 3% HPMC and 15 % WPC-70 were chosen as optimum levels. The obtained gluten-free bread can be considered as protein rich. The optimized bread was analyzed for various parameters including protein, moisture, fat, crude fiber content, acid insoluble ash and pH. The analyzed results were reported as 10.48g, 38.73g, 8.97g, 2.8g, 0.134g, 6.1 respectively. The microbiological analysis of optimized bread was performed. The total plate count was10, yeast mould was 10 and coliform count Nil. Hence, it can be stated that HPMC and WPC-70 can be efficiently used to obtain gluten-free protein rich bread.

Physical properties and estimated glycemic index of protein-enriched sorghum based chips

Sorghum is a gluten-free grain and more attention has been given to the nutritional properties and recently its usage as a wheat replacement in food products. In the present work, protein-enriched sorghum based snack chips, prepared from sorghum meal with soy protein isolates and soy flour to meet the final protein content of 35.7%, were produced. The effect of varying baking powder (1.5-2.5%), dough sheet thickness (0.7-1.7 mm), and baking time (6-12 min) on the physical properties of the snack chips was investigated using a central composite design of response surface methodology. Under baking temperature of 160 °C, with baking powder added, the water activity and puffiness of chips significantly increased. Baking time was the most significant factor for all the parameters detected except for puffiness. The optimized conditions of preparing protein-enriched sorghum chips were baking powder 2.5%, dough sheet thickness 0.7 mm, and baking time 7.66 min. The estimated glycemic index (eGI) of the protein-enriched sorghum chips (eGI = 59.8) was significantly lower than soybean-free sorghum chips. The gluten-free protein-enriched sorghum chips developed could be considered as protein rich with lower intermediate-glycemic index classified healthy snacks and potential commercialization.