Impact of hydrothermal pretreatments on physicochemical characteristics and drying kinetics of starch from red rice ( Oryza sativa L.)

Improving physicochemical and nutritional attributes of rice starch through green modification techniques

Rice, has long been an inseparable part of the human diet all over the world. As one of the most rapidly growing crops, rice has played a key role in securing the food chain of low-income food-deficit countries. Starch is the main component in rice granules which other than its nutritional essence, plays a key role in defining the physicochemical attributes of rice-based products. However, rice starch suffers from weak techno-functional characteristics (e.g., retrogradability of pastes, opacity of gels, and low shear/temperature resistibility. Green modification techniques (i.e. Non-thermal methods, Novel thermal (e.g., microwave, and ohmic heating) and enzymatic approaches) were shown to be potent tools in modifying rice starch characteristics without the exertion of unfavorable chemical reagents. This study corroborated the potential of green techniques for rice starch modification and provided deep insight for their further application instead of unsafe chemical methods.

Evaluation of dual modification by high hydrostatic pressure and annealing on the physicochemical properties of bean starch

This study investigated the physical modifications by high hydrostatic pressure (HHP) at 600 MPa for 30 min/30 °C, annealing (AN) at 50 °C/24 h and the combination of both (HHP + AN and AN + HHP) applied to yellow bean starch to verify changes in morphology, X-ray diffraction, molecular order, thermal properties and pasting properties of native (NS) and modified starches. Morphological analysis showed loss of sphericity and increase in diameter with the appearance of pores on the surface after application of treatments. The AN starch showed lower values of syneresis, degree of double helix (DD), order (DO), and viscosity of the paste obtained by RVA. It exhibited a Vh-type classification with the appearance of the amylose-lipid complex. However, the gelatinization temperatures, as well as the enthalpy of gelatinization, were significantly higher. On the other hand, the starch treated with HHP showed a higher Setback (SB) value. The greatest modifications were found for the starches subjected to the combined treatments (AN + HHP) and (HHP + AN), where the order of the treatments was significant for the morpho-structural changes of yellow bean starch. According to the micrographs, the surface aspect was altered, with AN + HHP showing greater irregularities and flat yet irregular faces, as well as a larger granule diameter (147.05). The X-ray diffractogram showed a reduction in crystallinity from 28.14 % (NS) to 18.09 % (AN + HHP) and classified the starch as type "A". The double modification (HHP + AN and AN + HHP) reduced the gelatinization temperature and the enthalpy of gelatinization but had no effect on the bands of the FT-IR spectrum. There was only a reduction in the degree of order and the double helix. Finally, the treatment with AN + HHP is more effective as the gelatinization with AN facilitates the application of HHP. Both methods used are classified as physical (thermal and non-thermal), aiming to minimize environmental impacts and achieve faster and safer morpho-structural modification without leaving chemical residues in the products.

Red rice starch modification - Combination of the non-thermal method with a pulsed electric field (PEF) and enzymatic method using α-amylase

The objective of this study was to investigate the dual modification of red rice starch using pulsed electric field (PEF) and α-amylase, focusing on morpho-structural, thermal, and viscoamylographic properties. Native starch (Control) underwent various treatments: PEF at 30 kV cm-1 (PEF30), α-amylase at 9.0 U mg-1 (AA0), and a combination of both (PEF30 + α and α + PEF30). The PEF30 + α treatment exhibited the highest degree of digestion (10.66 %) and resulted in morphological changes in the starch granules, which became elongated and curved, with an increased average diameter of 50.49 μm compared to the control. The starch was classified as type A, with a maximum reduction in crystallinity of up to 21.17 % for PEF30. The deconvolution of FT-IR bands indicated an increase in the double helix degree (DDH) for PEF30 and AA0, while the degree of order (DO) was reduced for PEF30, AA0, and PEF30 + α. DSC analysis revealed significant modifications in gelatinization temperatures, particularly for PEF30, and these changes were supported by a reduction in gelatinization enthalpy (ΔH) of up to 28.05 % for AA0. These findings indicate that both individual and combined treatments promote a decrease in starch gelatinization and facilitate the process, requiring less energy. Differences were observed between the formulations subjected to single and alternating dual treatments, highlighting the influence of the order of PEF application on the structural characteristics of starch, especially when applied before the enzymatic treatment (PEF + α). Regarding the viscoamylographic parameters, it was observed that AA0 presented higher values than the control, indicating that α-amylase enhances the firmness of the paste. The double modification with PEF + α was more effective in reducing syneresis and starch retrogradation, leading to improvements in paste properties. This study provided significant insights into the modification of red rice starch using an efficient and environmentally friendly approach.

Characterization and Evaluation of Heat-Moisture-Modified Black and Red Rice Starch: Physicochemical, Microstructural, and Functional Properties

This study sought to evaluate starch from black and red rice modified by heat-moisture, investigating the extraction yield, starch and amylose content, color, and phenolic compounds. The water and oil absorption capacity, whole milk and zero lactose absorption index, syneresis index, and texture were also analyzed. Microstructural analysis included Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The heat-moisture treatment (HMT) reduced the extraction yield and the starch and amylose content, with native black rice starch having the highest values for these parameters. The modification also affected the color and phenolic compounds of the starch, making it darker and changing its appearance. The modification improved the absorption of water, oil, and milk, reducing syneresis and increasing stability during storage. The starch surface was altered, especially for modified black rice starch, with larger agglomerates. The type of starch also changed from A to Vh, with lower relative crystallinity. The textural properties of modified red rice starch were also significantly altered. The HMT proved to be a viable and economical option to modify the analyzed parameters, influencing the texture and physicochemical properties of pigmented rice starch, expanding its applications, and improving its stability during storage at temperatures above 100 °C.

Effect of enzymatic hydrolysis on digestibility and morpho-structural properties of hydrothermally pre-treated red rice starch

The objective of this work was to evaluate the effects of enzymatic hydrolysis on digestibility and morphological and structural properties of hydrothermally pre-treated (HPT) red rice starch. The pre-treatments were performed in autoclave and cooking for the modification of rice grains and native starch. In vitro starch digestibility was performed consecutively and semi-simultaneously using α-amylase and amyloglucosidase. A first-order mathematical model was used to adjust the hydrolysis kinetic data, which made it possible to calculate the surface area, hydrolysis index, and glycemic index of the starch. Scanning electron microscopy images (SEM), Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) were also performed to investigate the characteristics of the post-hydrolysis starch samples. The autoclaved starch HSS-A3, which was subjected to 121 °C/1.08 bar for 10 min, showed the highest in vitro digestibility values (80.08 %). Both starch samples showed increase of particle size and enzymatic digestibility after HPT. FTIR spectra of the starch samples showed that there was no appearance of new functional groups. However, XRD evidenced that HPT changed the intensity of the peaks and the type of crystallinity was changed for autoclaved starch (A3) from type A to Vh, with crystallinity ranging from 21.71 % to 26.42 %. The semi-simultaneous approach showed more advantages due to the highest in vitro digestibility as well as reducing the processing time and use of reagents.

Foaming characteristics and impact of ethanol pretreatment in drying behavior and physical characteristics for avocado pulp powder obtained by foam mat drying

The objective of this study was to optimize the production of powdered avocado using foam mat drying. In order to achieve this, the effect of Emustab^® (4, 6, and 8% w/w), goat's milk (10, 15, and 20% w/w), and whipping time (15, 20, and 25 min) on the foam physical properties of avocado pulp were evaluated. In addition, the influence of ethanol pretreatment on the drying kinetics, thermodynamic properties, and physicochemical characteristics of the powders was also assessed. An experimental design 2³ with three central points was used in this study and optimized foam conditions were dried at 50, 60, and 70°C, with a fixed air speed of 1.5 m/s. Empirical and diffusive models (boundary conditions of the third type) were adjusted to the experimental data to describe the drying kinetics and to determine the process activation energy and thermodynamic properties. The final products were characterized regarding their physical properties. Optimized foam mat drying conditions were achieved when avocado pulp was whipped for 15 min and 8% of Emustab^® and 20% of powdered goat milk were used as foaming agents. The use of an ethanol pretreatment and higher drying temperature (70°C) resulted in higher drying rate (1.6 × 10² /min) and shorter processing time (270 min). The ethanol pretreatment reduced the activation energy and Biot number and led to more uniform moisture distribution. The physical properties, such as water content, water activity, bulk, and tapped densities decreased with an increase in drying temperature and pretreatment with ethanol, whereas water absorption capacity increased. PRACTICAL APPLICATION: In this work, new information about the drying kinetics and mass transfer of the foam mat avocado pulp using ethanol as pretreatment is obtained. The results will contribute to the optimization production avocado foaming and powder. Ethanol pretreatment can represent an alternative to minimize the negative impacts on drying process and can be surely suggested as an industrial application.