Effects of microwave heat treatment on fungal growth, functional properties, total phenolic content, and antioxidant activity of sorghum (Sorghum bicolor L.) grain

Effect of different thermal treatments on starch digestion of Tsamba (Highland barley products): Insights from starch structural properties and enzyme activity

This study elucidated the mechanisms involved in the impact of Tsamba (a highland barley product) starch digestibility by different thermal treatments. The results demonstrate that different thermal processing methods (microwave, roasting, sand frying, frying, baking, and steaming) significantly alter the polyphenol content of highland barley, which in turn affects its ability to inhibit α-amylase activity. SEM, CLSM, XRD and FTIR were used to evaluate the effects on starch microstructure and digestibility. The microstructure, short-range order, and crystalline structure of starch would modify after different thermal treatments. Notably, the starch structure with the least disruption and improvement in resistance to enzyme hydrolysis suggests that microwaves may be an effective way to produce foods with higher resistant starch content. This study provides valuable insights into dietary strategies for the management of starch digestibility in people with diabetes.

Dynamic migration of phenolics in microwaved combined cooked sorghum: Focus on the polyphenols interact with starch/protein

Based on the perspective of whole sorghum food, the polyphenols migration process was analyzed during microwave-combined cooking treatment utilizing wide metabolomics, simulated reactions, and molecular docking. Microstructure confirmed that microwave broke the grain cells, resulting in the elevated polyphenols contents. Flavonoids were significantly released by microwave (e.g. arbutin, eriodictyol-7-o-glucoside, narirutin, and naringenin-7-o-glucoside), which regulated the antioxidant activity of sorghum. Simulated co-gelatinization reaction revealed that polyphenols interacted non-covalently with starch, resulting in higher levels of polyphenols being retained during cooking (711.12 mg GAE/100 g). Molecular docking results exhibited that 6 flavonoids could also bind to the kafirin via hydrogen bonds and hydrophobic interaction during cooking. Meanwhile, the γ-mangostin also possessed stabilized root-mean-square deviation and outstanding binding free energies. The effective retention of bioactive components under synergetic microwave and cooking treatment highlights the potential of natural ingredients in food processing, promoting a more natural approach to modern cereal nutrition.

Effect of microwave energy combined with hot air on the functional properties and antioxidant activity and pasting properties of Samh (Mesembryanthemum forsskalei Hochst) seeds

The study aimed to investigate the effect of microwave heating combined with hot air (70 °C) at different application times (0, 90 &180 s,) on the colour, digestible a soluble protein, functional and pasting properties, antioxidant capacity of Samh seeds (8, 12 & 16 % moisture content). The results indicated that microwave heating caused a significant change in Samh seed's colour and enhanced the protein solubility of the seeds, and the functional properties and viscosities of the Samh seeds. Moreover, the results showed that the moisture content of the Samh seeds and application time significantly impact the seeds' quality parameters. However, the partial least square (PLS) model validated that the microwave treatments of the samh seed with (16 %, 180 s) were treated with microwave energy combined with hot air circulation Accordingly, microwaves may offer the potential of being an effective emerging technology for improving the quality and functional characteristics of Samh seeds.

Impact of Thermophysical and Biological Pretreatments on Antioxidant Properties and Phenolic Profile of Broccoli Stem Products

Fruit and vegetable industrialisation is a major contributor to food waste; thus, its integral transformation into functional powders has gained attention. Pretreatments can be incorporated into valorisation processes to generate structural or biochemical changes that improve powders' characteristics. This study deepens into the impact of biological (fermentation, FERM) and thermophysical (autoclaving, AUTO; microwaves, MW; ultrasound, US; and pasteurisation, PAST) pretreatments, combined with dehydration (hot air-drying, HAD; or freeze-drying, FD) on the characteristics of powdered products obtained from broccoli stems. The impact of pretreatments on physicochemical (moisture, water activity, total soluble solids) and antioxidant properties (phenols, flavonoids, antioxidant capacity by ABTS and DPPH) on residue and powdered products was studied, together with their impact on plant tissue structure (Cryo-SEM) and the powders' phenolic profile (HPLC). Probiotic viability was also determined on the fermented samples. The pretreatments applied, particularly the ultrasound, improved the antioxidant properties of the broccoli stems compared to the unpretreated samples, in line with microscopic observations. Dehydration did also improve the antioxidant attributes of the broccoli wastes, especially drying at 60 °C. However, pretreatments combined with dehydration did not generally lead to an improvement in the antioxidant properties of the powders. Probiotic properties were preserved in the freeze-dried products (>107 CFU/g). In conclusion, pretreatments may be applied to enhance the antioxidant attributes of broccoli wastes, but not necessarily that of dried powdered products.

Characterization of Plant-Based Meat Treated with Hot Air and Microwave Heating

Plant-based meat is growing globally due to health, environmental, and animal welfare concerns, though there is a need for quality improvements. This study assessed how different ratios of wheat gluten (WG) to soy protein isolate (SPI) and various baking methods-hot air (HA), microwave (MW), and a combination of both (HA-MW)-affect the physicochemical properties of plant-based meat. Increasing the SPI from 0% to 40% significantly enhanced lightness, hardness, chewiness, water-holding capacity, moisture content, and lysine (an essential amino acid) (p ≤ 0.05). Hardness and chewiness ranged from 4.23 ± 1.19 N to 25.90 ± 2.90 N and 3.44 ± 0.94 N to 18.71 ± 1.85 N, respectively. Baking methods did not affect amino acid profiles. Compared to HA baking, MW and HA-MW baking increased lysine content (561.58-1132.50 mg/100 g and 544.85-1088.50 mg/100 g, respectively) while reducing fat and carbohydrates. These findings suggest that a 40% SPI and 60% WG ratio with microwave baking (360 W for 1 min) optimizes plant-based meat, offering benefits to both consumers and the food industry in terms of health and sustainability.

Microwave irradiation of guar seed flour: Effect on anti-nutritional factors, phytochemicals, in vitro protein digestibility, thermo-pasting, structural, and functional attributes

Guar seed flour (GSF) has a high amount of carbohydrates, proteins, phytochemicals, and anti-nutritional factors (ANFs), which limits its use. To address this issue, the current study was undertaken to understand the effect of microwave (MW) irradiation on ANFs, phytochemicals, in vitro protein digestibility (IVPD), and functional attributes of GSF at varying power density (Pd: 1-3 W/g) and duration (3-9 min). The ANFs were determined using a colorimetric assay and a Fourier transform infrared spectrum. At 3 Pd-9 min, the maximum reduction in ANFs (tannin, phytic acid, saponin, and trypsin inhibitor activity) was observed. Higher Pd and treatment duration increased antioxidant activity and total phenolic content, except for total flavonoid content. Furthermore, compared to the control sample (78.38%), the IVPD of the GSF samples increased to 3.28% (3 Pd-9 min). An increase in Pd and duration of MW treatment improved the thermal and pasting properties of GSF samples up to 2 Pd-9 min. Due to inter- and intramolecular hydrogen bonding degradation, the relative crystallinity of the 3 Pd-9 min treated GSF sample was 30.58%, which was lower than that of the control (40.08%). In MW-treated samples, SEM images revealed smaller clusters with rough and porous structures. However, no noticeable color (ΔE) changes were observed in MW-treated samples. Aside from water absorption capacity and water solubility index, MW treatment reduced oil absorption capacity, foaming capacity, and emulsifying capacity. As demonstrated by principal component analysis, MW irradiation with moderate Pd (2-3) was more effective in reducing ANFs, retaining nutritional contents, and improving the digestible properties of GSF, which could be a potential ingredient for developing gluten-free products.

Effect of sorghum pre-processing (roasting and germination) on the replacement level and quality of sorghum-wheat bread: bread characteristics, digestibility, consumer acceptability and microbiological analysis

Abstract

The present study was focused on the replacement of refined wheat flour (RWF) by control (CS) and processed sorghum flour [germinated (GS) and roasted (RS)] on the properties of flour/batter/dough (particle size, XRD, pasting, dynamic rheology, farinograph) and bread (physical, textural, digestibility, microbiological and sensory). Prominent variations adhered with sorghum processing, but decreasing patterns occurred for flour-water absorption, dough stability times, storage modulus, peak/final/breakdown viscosities, bread-moisture content, specific volume, porosity, and lightness. Flour's pasting temperature, dough development time, breadbulk density, hardness, gumminess, and bitterness increased. Composite flours mainly had weak nature compared to RWF. The baking loss was lower for 10-30% CS and GS incorporation than RS. Composite bread had higher in-vitro protein and starch digestibility (CS > GS > RS) than RWF. Three days storage life with acceptable quality scores was obtained for bread with CS and GS up to 20% and RS up to 30% incorporation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05810-3.

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.

Sorghum Flour and Sorghum Flour Enriched Bread: Characterizations, Challenges, and Potential Improvements

A Sorghum flour (SF) is a leading and prominent food source for humans in African countries. Recently extensive studies have been conducted on Sorghum bread (SB) or sorghum composite bread (SCB), covering various aspects. However, there are many technical challenges in the formation of SF and sorghum composite flour (SCF) that impact the quality of the bread and fail to meet the consumer's desires and expectations. This review primarily focuses on the characteristics of SF, SCF, SB, and SCB, with discussions encompassing the rheological and morphological properties of the dough, improvement strategies, and bread quality. Moreover, a comprehensive analysis has been conducted to investigate the behavior of SF and SCF along with a discussion of the challenges affecting bread quality and the strategies applied for improvement. The significant demand for nutrients-rich and gluten-free bread indicates that sorghum will become one of the most vital crops worldwide. However, further comprehensive research is highly demanded and necessary for an in-depth understanding of the key features of SF and the resulting bread quality. Such understanding is vital to optimize the utilization of sorghum grain in large-scale bread production.

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.

Total Flavonoids Extracts of Apocynum L. from the Ili River Valley Region at Different Harvesting Periods and Bioactivity Analysis

In the current study, the total content from two Apocynum species leaves (Apocynum venetum and Apocynum hendersonii) collected from the Ili River Valley Region were extracted, and their bioactivities were investigated. The results showed a significant variation in the total flavonoid contents in the leaf samples collected at different periods (June, July, August, and September), with the highest content in August (60.11 ± 0.38 mg RE/g DW for A. venetum and 56.56 ± 0.24 mg RE/g DW for A. hendersonii), and the lowest in June (22.36 ± 0.05 mg RE/g DW for A. venetum and 20.79 ± 0.02 mg RE/g DW for A. hendersonii). The total flavonoid content was comparably higher in A. venetum than in A. hendersonii. Leaves extracts from the two species demonstrated strong bioactivity, which positively correlated with the total flavonoid contents. The anti-oxidative activity of A. venetum was higher than that of A. hendersonii in tandem with its higher flavonoid contents; the antibacterial activity, however, was conversely opposite. Furthermore, a total of 83 flavonoid metabolites were identified in the two species based on UPLC-ESI-MS/MS, out of which 24 metabolites were differentially accumulated. The variability in these metabolites might be the reason for the different bioactivities displayed by the two species. The present study provides insight into the optimal harvest time for Apocynum species planted in the major distribution area of the Ili River Valley and the specific utilization of A. venetum and A. hendersonii.

Microwaving released more polyphenols from black quinoa grains with hypoglycemic effects compared with traditional cooking methods

BACKGROUND

Polyphenols were reported to exhibit inhibitory effects on digestive enzymes to regulate carbohydrates and lipid digestion. However, different cooking methods might cause differences in the composition of polyphenols in cereal grains and thus further affect their activities.

RESULTS

The present study used boiling, roasting and microwaving to cook black quinoa and extracted polyphenols from them. Their total phenolic content (TPC) and total flavonoids content were determined, and phenolic composition was analyzed via high-performance liquid chromatography-mass spectrometry (HPLC-MS). Compared with other cooking methods, phenolic extract from microwaved black quinoa (PEM) showed the highest TPC value (about 2.64 mg GAE g^-1 ). Microwaving released more phenolic acids (ferulic acid and gallic acid) from black quinoa grains. PEM also exhibited the strongest antioxidant and α-glucosidase inhibitory activities. Lineweaver-Burk plots showed that PEM inhibited α-glucosidase in an uncompetitive mode, which was supported by circular dichroism analysis. PEM further reduced about 20.04% of digested starch in an in vitro digestion model and suppressed postprandial blood glucose increases (about 16.91% reduction) in vivo.

CONCLUSION

Collectively, our data suggested that microwaving could be an ideal method to cook quinoa in regards of its polyphenols in management of postprandial blood glucose. © 2022 Society of Chemical Industry.

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 Microwave Treatment on Structure, Functional Properties and Antioxidant Activities of Germinated Tartary Buckwheat Protein

Tartary buckwheat protein (TBP) has promise as a potential source of novel natural nutrient plant protein ingredients. The modulating effects of microwave pretreatment at varying powers and times on the structure, functional properties, and antioxidant activities of germinated TBP were investigated. Compared with native germinated TBP, after microwave pretreatment, the content of free sulfhydryl groups in the germinated TBP increased, and the secondary structure changes showed a significant decrease in α-helix and an increase in random coil contents, and the intensity of the ultraviolet absorption peak increased (p < 0.05). In addition, microwave pretreatment significantly improved the solubility (24.37%), water-holding capacity (38.95%), emulsifying activity index (17.21%), emulsifying stability index (11.22%), foaming capacity (71.43%), and foaming stability (33.60%) of germinated TBP (p < 0.05), and the in vitro protein digestibility (5.56%) and antioxidant activities (DPPH (32.35%), ABTS (41.95%), and FRAP (41.46%)) of germinated TBP have also been improved. Among different treatment levels, a microwave level of 300 W/50 s gave the best results for the studied parameters. Specifically, microwave pretreatment could be a promising approach for modulating other germinated plant protein resources, as well as expanding the application of TBP.

Optimization of Flavonoid Extraction from Xanthoceras sorbifolia Bunge Flowers, and the Antioxidant and Antibacterial Capacity of the Extract

In the present work, the extraction process of total flavonoids (TFs) from X. sorbifolia flowers by ultrasound-assisted extraction was optimized under the response surface methodology (RSM) on the basis of single-factor experiments. The optimal extraction conditions were as follows: ethanol concentration of 80%, solid–liquid ratio of 1:37 (g/mL), temperature of 84 °C, and extraction time of 1 h. Under the optimized conditions, the extraction yield of the TFs was 3.956 ± 0.04%. The radical scavenging capacities of TFs against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were much greater than that of rutin. The results of antibacterial experiments indicated that the TFs displayed strong inhibitory activities on E. coli, S. aureus and Bacillus subtilis. Therefore, X. sorbifolia flowers can be used as a novel source of natural flavonoids, and the TFs have potential applications as natural antioxidants or antibacterial agents in the food and pharmaceutical industries.

Quality characteristics of sand, pan and microwave roasted pigmented wheat (Triticum aestivum)

Present study investigated the effect of sand, pan and microwave roasting on physico-chemical, functional and rheological properties of yellow (YW), purple (PW), and black wheat (BW). All roasting methods enhanced the browning index (BI), water absorption capacity (WAC) and oil absorption capacity (OAC) roasted wheat flour. Microwave roasting showed significantly higher impact on BI (58.61% for YW, 131% for BW and 83.85% for PW) and WAC (47.93% for YW, 44.63% for BW and 32.09% for PW). However, the decrease in density, emulsifying capacity (EC), foaming capacity (FC), total phenolic content (TPC), total flavonoid content (TFC), and total anthocyanin content (TAC), and antioxidant activity was observed on roasted wheat flour. Roasting also affected the pasting properties of wheat flours and peak, trough, breakdown and final viscosity decreased.