Low-frequency ultrasonication modulates the impact of annealing on physicochemical and functional properties of rice flour

Ultrasound-assisted annealing treatment to improve physicochemical and digestive properties of banana flour

BACKGROUND

Banana flour can provide a solution to people with gluten intolerance, as it is gluten-free. Native banana flour may have limited functionality in certain applications. In this study, banana flour was modified by ultrasonic (US) and annealing (ANN) treatments at four incubation time spans, namely 12, 24, 36 and 72 h, separately or combined sequentially (US-ANN) to enhance the physicochemical and digestive properties.

RESULTS

US led to exposed granular surfaces and damaged non-starch components. Both treatments, at extended incubation time, increased crystallinity, resulting in a narrower starch gelatinization temperature range. The swelling power was significantly lower for ANN and US-ANN compared to US alone, providing a delay of gelatinization temperature. However, none of the treatments affected the gelatinization enthalpy. Furthermore, US increased peak viscosity, breakdown, final viscosity and setback whereas the opposite results were obtained for ANN and US-ANN. Additionally, US prior to ANN significantly increased the resistant starch (RS) content for annealing times over 24 h, especially for the US-ANN treatment for 72 h, which provided the highest RS content (49.3%) compared to ANN treatment for 72 h (44.0%) and native flour (36.3%).

CONCLUSIONS

US prior to ANN treatment offers an alternative method to improve the functional and digestive properties of banana flour, extending the range of applications. © 2024 Society of Chemical Industry.

Tailoring the physicochemical properties of starch: impact of integrated ultrasonic and ethanol pretreatment on the oil uptake of infrared fried ginkgo seeds

BACKGROUND

The structural changes of starch would have a more crucial impact on oil absorption and quality changes in starch-rich fruits and vegetables during frying process with enhanced heat transfer (such as infrared frying). In the present study, the influence of integrated ultrasonic and ethanol (US + ethanol) pretreatment on oil uptake in infrared fried (IF) ginkgo seeds was evaluated regarding modifications in the physicochemical properties of starch. The pretreatment was performed with ultrasonic (40 kHz, 300 W) and ethanol osmotic (95%, v/v) treatment individually or integrated for 40 min.

RESULTS

The mass transfer in the pretreatment was facilitated by combined ultrasound and ethanol. The swelling power, solubility, and gelatinization degree of starch was significantly increased. Low-frequency-NMR curves and images revealed that the bound water fraction in ginkgo seeds was increased and the water distribution was homogenized. The results of Fourier transform-infrared spectrum and differential scanning calorimeter revealed that the crystalline regions of starch were reduced and the thermal enthalpy was decreased after US + ethanol pretreatment. The total, surface and structural oil content in IF ginkgo seeds with US + ethanol pretreatment was reduced by 29.10%, 34.52% and 29.73%, respectively. The US + ethanol pretreatment led to a thinner crust layer with increased porosity and smaller-sized pores in the IF ginkgo seeds as observed by stereo microscopy and scanning electron microscopy.

CONCLUSION

The changes in structural and physicochemical properties of starch by combined ultrasound and ethanol affect the crust ratio and pore characteristics in fried high-starch fruits and vegetables, thereby reducing oil absorption. © 2024 Society of Chemical Industry.

Radio frequency drying on functional diversity of tiger nut flour: Effects on physicochemical, structural, and rheological properties

Tiger nut (TN) is a valuable nutrient and gluten-free tuber. To achieve high-quality TN flour as functional ingredients in food, it is essential to develop effective drying technologies for TN. Five drying methods including natural drying (Control), hot-air drying (HD), radio frequency single drying (RFSD), RF assisted hot-air drying (RFHD), and RF- vacuum drying (RFVD) were selected and compared to determine their effects on physiochemical, structural, and rheological properties of TN flour. Results showed that RF drying (RFD) significantly improved the hydration, oil-absorbing, and antioxidant activity capacity, especially for RFVD. RFHD exhibited greater color (BI = 13.80 ± 0.05 and C = 10.26 ± 0.05) and reducing sugar content (253.50 ± 2.27 mg d.b.) than RFSD and RFVD. The gelatinization temperature, enthalpy value, and particle size (57.30-269.33 μm) of TN flour were reduced. The structural property results indicated that RFD reduced the relative crystallinity and short-range ordering of the flour, altered protein secondary structure, and caused the damaged microstructure in comparison with Control and HD groups. All sample gels exhibited a weak strain overshoot behavior (type III) under large amplitude oscillations, and RFD resulted in a reduced viscoelastic behavior. RFD could be an effective method to produce functional TN flour.

Physicochemical and rheological properties of ultrasonic-assisted pregelatinized rice flour

This study evaluated the physical and rheological properties of whole rice flour treated for different sonication times (0-15 min). Ultrasonication reduces the particle size of rice flour and improves its solubility. Viscosity tests using RVA and steady shear showed a notable decrease in the viscosity of the rehydrated pregelatinized rice flour. Although no unusual patterns were observed in the XRD analysis, the FT-IR and microstructure morphology findings suggest that ultrasonication led to structural changes in the rice flour. Overall, the study indicates that ultrasonication is a practical and clean method for producing plant-based drinks from rice flour, which could expand its limited applications in the beverage industry.

Structure, properties, and resistant starch content of modified rice flour prepared using dual hydrothermal treatment

In this study, modified rice flour with high resistant starch (RS) content was prepared by dual hydrothermal treatment, which combined the heat-moisture treatment with the pressure-heat treatment method. The effects of dual hydrothermal treatment on the structure and properties of modified rice flour and their relationship with RS content were further discussed. The results showed that the RS content of modified rice flour was higher than that of rice flour (RF), and dual hydrothermal treatment was more effective than single hydrothermal treatment. Adhesion and aggregation occurred between the particles of modified rice flour. Both crystallinity and short-range ordering were increased in modified rice flour compared to RF. Moreover, the modified rice flour of dual hydrothermal treatment had higher crystallinity and a more ordered short-range structure of starch, which improved RS content to a certain extent. Compared to single hydrothermal treatment, the modified rice flour of dual hydrothermal treatment had a lower viscoelasticity and a better thermal stability. Both RF and modified rice flour gels were composed mainly of free water, with minimal amounts of bound and immobile water. The study may provide a reference for the production and application of modified rice flour.

Ultrasound-mediated hydration of finger millet: Effects on antinutrients, techno-functional and bioactive properties, with evaluation of ANN-PSO and RSM optimization methods

Finger millet, rich in nutrients, faces bioavailability limitations due to antinutrients like phytates and tannins that can be reduced by ultrasound mediated hydration (USH). Here, USH process of finger millet was optimized by varying ultrasound amplitude, water to grain ratio (W:G), treatment time, and frequency for reducing antinutrients and improving techno-functional attributes. USH resulted in a maximum reduction of 73% and 71% in phytates and tannins, respectively. The process was modeled using artificial neural network (ANN) and response surface methodology (RSM). ANN outperformed RSM in process prediction, and particle swarm optimization (ANN-PSO) suggested optimal conditions: 76% amplitude, W:G of 3.5:1, 17.5 min treatment time at 40 kHz. USH samples showed higher β-sheet, β-turn, and random coil proportions, with lower α-helix levels. Multivariate analysis also identified higher amplitude and frequency, with shorter treatment time as desirable USH conditions. USH could aid in enhancing commercial viability and nutritional quality of finger millet.

Physicochemical Characterisation of Seeds, Oil and Defatted Cake of Three Hempseed Varieties Cultivated in Spain

The increasing use of hempseed in food products highlights the need for a comprehensive database for scientific research and industrial applications. In food development, information about the techno-functional properties of raw materials plays a crucial role in determining the suitability of each product for specific applications. Thus, this study aims to characterise three hempseed varieties (Ferimon, Henola and Uso-31), comparing their physicochemical and nutritional compositions. Moreover, the study investigates the impact of hempseed varieties on the techno-functional, physical and thermal properties of the partially defatted hempseed flours (PDHFs) obtained from single screw pressing (SSP) oil extraction. The fatty acid and tocopherol profiles of the dehulled seeds and oil were also analysed. Significant variations in yield and physical properties were observed among hempseed varieties, influenced by genetics, adaptation to agro-climatic conditions and cultivation systems. Despite its lower yield (kg/ha), Uso-31 exhibited superior 1000-seed weight, dehulling yield and larger mean seed size (1.79 ± 0.02 mm). Hempseed oil was rich in unsaturated fatty acids, particularly linoleic (51.2-53.4 g/100 g oil) and α-linolenic (14.88-18.97 g/100 oil) acids, showing variations in γ- and α-tocopherols depending on the variety. The variety also influenced the least gelation concentration (LGC) and techno-functional properties such as water absorption capacity (WAC), emulsifying activity (EA) and emulsion stability (ES). SDS-PAGE and DSC measurements indicated the presence of 11S and 7S globulin proteins with denaturation temperatures above 87.8 °C. These findings confirm that the studied hempseed flours are valuable techno-functional and nutritional ingredients suitable for sustainable food formulations.

Impact of long-term ultrasound treatment on structural and physicochemical properties of starches differing in granule size

Granule size is a critical parameter affecting starch processing properties. Ultrasound treatments of up to 22 h were applied on two starches differing in granule size (quinoa starch and maize starch). The two starches showed significantly different trends in both structural and physicochemical aspects affected by the ultrasound treatments. For the small granule starch (volume-weighted mean particle size of 1.79 μm), short-term ultrasonication caused an increase of swelling power. As the treatment time increased, the physicochemical properties were influenced by the degradation of amylopectin external chains. The X-ray diffraction results showed a decrease of relative crystallinity and changes of peak areas with long-term treatment. On the other hand, a balance between amylose leaching and surface damages was seen for the large granule starch (volume-weighted mean particle size of 18.3 μm). The effect of ultrasound modification on starches with different molecular and granular structures was discussed. A possible mechanism of the ultrasound effect was proposed.

Increasing Protein Content of Rice Flour with Maintained Processability by Using Granular Starch Hydrolyzing Enzyme

Rice flour (RF) has become a promising food material. In the present study, RF with higher protein content was prepared using a granular starch hydrolyzing enzyme (GSHE). Particle size, morphology, crystallinity, and molecular structures of RF and rice starch (RS) were characterized to establish a hydrolytic mechanism; thermal, pasting, and rheological properties were determined to evaluate processability using differential scanning calorimetry (DSC), rapid viscosity analysis (RVA), and rheometer, respectively. The GSHE treatment resulted in pinholes, pits, and surface erosion through sequential hydrolysis of crystalline and amorphous areas on the starch granule surface. The amylose content decreased with hydrolysis time, while the very short chains (DP < 6) increased rapidly at 3 h but decreased slightly later. After hydrolysis for 24 h, the protein content in RF increased from 8.52% to 13.17%. However, the processability of RF was properly maintained. Specifically, the data from DSC showed that the conclusion temperature and endothermic enthalpy of RS barely changed. The result of rapid RVA and rheological measurement indicated that RF paste viscosity and viscoelastic properties dropped rapidly after 1 h hydrolysis and thereafter recovered slightly. This study provided a new RF raw material useful for improving and developing RF-based foods.

Microwave Modification of Quinoa Grains at Constant and Varying Water Content Modulates Changes in Structural and Physico-Chemical Properties of the Resulting Flours

Microwave-assisted heat moisture treatment (MWT) was applied to quinoa grains, a nutritious gluten-free pseudocereal of great interest in food product development, to achieve the physical modification of the quinoa flour. The effect of treating quinoa grains at different initial water contents (WC; 10%, 20%, and 30%) in two operational systems was compared: one open at atmospheric pressure and variable WC (V system), and the other in hermetic containers at constant WC (C system). The morphological structure of the obtained flours and their techno-functional, rheological, and thermal properties were evaluated. MWT proved to be effective in modifying these properties, the main effects probably being caused by protein denaturation and aggregation, and intragranular molecular rearrangements of starch, with disruption of short-range molecular order and even the partial collapse of starch granules in the samples treated at the highest WC. The greatest differences were observed for the 20 and 30% WC treated-samples, particularly when using C system, which increased their water absorption capacity and decreased their foaming, emulsion, and gel-forming capacities. Based on these results, the control of WC and its evolution during MWT of quinoa grains appears to be a viable and effective approach to adapt flour functionality to the needs of food production, allowing a wider range of flour properties depending on the MWT conditions.

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.

Modification of the microstructure of tef [Eragrostis tef (Zucc.) Trotter] flour ultrasonicated at different temperatures. Impact on its techno-functional and rheological properties

Tef flour comes from a nutritionally-rich ancient grain gaining increasing interest in gluten-free market. Gluten-free sources are modified by different means to improve their functionality. Ultrasound treatment (US) alters flours' structure and leads to physically modified flours with a wider application range. The aim of the present work was to evaluate the impact of US treatments of moderate treatment time, 10 min, and high concentration of the aqueous flour dispersion, 25%, on the microstructural, starch damage, apparent amylose content, techno-functional, pasting and rheological properties of two tef flour varieties, white and brown. Temperature was varied (20, 40, 45, 50, and 55 °C) to modulate the impact of sonication. US treatments led to general particle fragmentation which markedly increased starch damage and lightness (L*) values. Apparent amylose content was higher after ultrasonication, as consequence of molecular fragmentation due to cavitation. Increased starch granules' exposed area led to enhanced interaction with water, promoting the water absorption index (WAI) and swelling power (SP) of treated flours. Pasting properties showed increased pasting temperatures as well as decreased viscometric profiles with lower breakdown viscosities, indicative of starch rearrangement improved by increasing temperature. Rheological properties indicated higher consistency in gels after US treatments, with improved ability to withstand stress and lower values of tan(δ)1 reflecting a higher solid-like behavior and higher strength of the gel. Temperature was found to be a crucial variable during US treatments, showing an improved degree of modification at higher temperatures in ultrasonicated tef flours, following the same trend in both varieties.

Impact of Solubilized Substances on the Techno-Functional, Pasting and Rheological Properties of Ultrasound-Modified Rice, Tef, Corn and Quinoa Flours

The modification of flours by ultrasound (US) treatments requires excess water to suspend the sample to be treated, which must be removed after treatment to recover the ultrasonicated flour. The aim of this study was to determine the influence that the water removal method has on the final characteristics of US-treated gluten-free flours (rice, brown tef, corn and quinoa). US treatment parameters were constant, and two water removal methods were studied: freeze-drying and centrifugation + drying. The elimination of water by centrifugation resulted in the loss of solubilized compounds from the treated flours, which led to important differences between the final characteristics of US-treated flours. Ultrasonication resulted in the reduction of flours' particle size and modification of their color parameters. Techno-functional properties were modified by US treatment, where the water removal method was more influential in whole grain samples (brown tef and quinoa). Few differences were found in thermal properties among pairs of US-treated samples, indicative that the effect caused to starch was mainly attributed to ultrasonication conditions than to the drying method. The water removal method markedly influenced the pasting properties of US-treated flours, resulting in lower profiles when freeze-drying was applied and higher profiles when flours were retrieved by centrifugation. Gels made with tef, corn and quinoa presented reduced tan(δ)₁ values after sonication, while gels made with rice did not show any modification. The water removal method is a decisive step in US treatments, defining the final characteristics of the treated matter, and having a great influence in the modification attributed to ultrasonication.

The Influence of Temperature Changes on the Rice Starch Structure and Digestive Characteristics: One and Two-Step Annealing

This study investigated the effects of annealing on the structural and physicochemical properties of rice starch below the onset temperature (To) by 5 °C and 15 °C. The results revealed that annealing improved the gelatinization temperature of rice starch, decreased the swelling power, solubility, and paste viscosity of rice starch, and had no significant effects on the morphological structure and crystal configuration of rice starch. In one-step annealing, the annealing temperature of 60 °C is more conducive to the rearrangement of starch molecules, so its crystallinity, short-range ordered structure, and gelatinization temperature are higher than at 50 °C; however, its RDS, SDS, and RS contents will be increased. During the two-step annealing treatment, the temperature change is not conducive to the molecular chain rearrangement and to the formation of perfect crystalline structure, which increases the sensitivity of enzymes to starch, so the RDS content of starch increases significantly, while the RS content decreases.

Ultrasound Treatment Enhanced Semidry-Milled Rice Flour Properties and Gluten-Free Rice Bread Quality

The structural and functional properties of physical modified rice flour, including ultrasound treated rice flour (US), microwave treated rice flour (MW) and hydrothermal treated rice flour (HT) were investigated with wet-milled rice flour (WF) used as a positive control. The results showed the presence of small dents and pores on the rice flour granules of US and MW while more fragments and cracks were showed in HT. XRD and FTIR revealed that moderate ultrasonic treatment promoted the orderly arrangement of starch while hydrothermal treatment destroyed the crystalline structure of rice flour. In addition, the significant decrease of gelatinization enthalpy and the narrowing gelatinization temperature were observed in US. Compared to that of SF, adding physical modified rice flour led to a batter with higher viscoelasticity and lower tan δ. However, the batter added HT exhibited highest G' and G″ values and lowest tan δ, which led to a harder texture of bread. Texture analysis demonstrated that physical modified rice flour (except HT) reduced the hardness, cohesion, and gumminess of rice bread. Especially, the specific volume of bread with US increased by 15.6% and the hardness decreased by 17.6%. This study suggested that ultrasound treatment of rice flour could improve texture properties and appearance of rice bread.

Microstructure, Digestibility and Physicochemical Properties of Rice Grains after Radio Frequency Treatment

Radio frequency (RF) energy has been successfully applied to rice drying, sterilization, and controlling pests. However, the effects of RF treatment on the microstructure, physicochemical properties, and digestibility of rice have rarely been studied. This study investigated the alteration of a multiscale structure, pasting, rheology, and digestibility of rice grains after the RF treatment. A microstructure analysis demonstrated that the RF treatment caused starch gelatinization and protein denaturation in rice grains with an increasing treatment time. After the RF treatment, indica and japonica rice (IR and JR) remained as A-type crystals, with the formation of an amylose–lipid complex. In contrast, the crystalline structure of waxy rice (WR) was disrupted. The RF treatment led to a decrease in crystallinity and short-range ordered structures. However, the DSC results indicated that the RF treatment enhanced the T_o, T_p, and T_c of IR and JR. The RF treatment resulted in an increase in the resistant starch (RS) of IR and JR, thereby reducing the digestibility. In addition, the pasting profiles of IR and JR after RF treatment were reduced with the increase in treatment time, while the RF-treated WR showed an opposite trend. The storage modulus (G′) and loss modulus (G″) of all samples after the RF treatment obviously increased compared to the control.