Gelatinization Of Starch Granules Research Articles

Effects of microwave vacuum drying on drying characteristics, quality attributes and starch structure of germinated brown rice

Germinated brown rice (GBR) has high nutritional and health-promoting value, but the influence mechanism of microwave vacuum drying (MVD) on the quality properties of GBR is still unclear. This study investigated the effects of MVD parameters including microwave intensities (9, 12, and 15 W/g), drying temperatures (50, 60, and 70 °C), and vacuum pressures (0.03, 0.05, and 0.07 MPa) on the drying characteristics, quality attributes and starch structure of GBR. A falling-rate phase dominated the MVD process of GBR and temperature-controlled MVD significantly preserved the GABA content in GBR. MVD caused microstructural changes with rearrangement and gelatinization of starch granules in GBR. For the GBR under MVD, increasing the drying temperature resulted in a significant decrease in enthalpy (ΔH) and an increase in the degree of starch gelatinization (DSG) (P < 0.05), however, no significant effect of microwave intensity and vacuum pressure on ΔH and DSG (P > 0.05) was found. MVD reduced the relative crystallinity but hardly changed the crystal type or formed functional groups of starch molecules in GBR. Overall, temperature-controlled MVD conduced to the final quality of GBR. This study may provide a potential method to improve the quality attributes of GBR in product development applications.

Effect of exogenous protein substitution in glutinous rice cake: Batter rheology, structure, and retrogradation behavior

The investigation focused on the batter properties, baking performance, and retrogradation behavior of gluten-free sponge cakes after partial (15%, 30%, and 45%) substitution of glutinous rice flour with exogenous protein, including whey protein isolates (WPI), egg white protein (EWP), and soy protein isolate (SPI). The viscoelastic properties and apparent viscosity of batter positively correlated with substitution levels, with SPI superior to WPI and EWP. WPI could produce batter with smaller and more evenly distributed cells, contributing to an enhanced specific volume of the cake due to its stabilizing effect of gas cells to form viscoelastic films. The gelatinization of starch granules proved to be constrained by the incorporation of WPI and SPI, as evidenced by elevated gelatinization temperature and reduced enthalpy change values. The restriction could be attributed to the strengthened hydrogen bonding between the starch and protein, which subsequently alleviated the retrogradation and water redistribution of cake during storage. An unpleasant eggy or beany flavor of cake was generated at 45% substitutions of EWP and SPI. In comparison, 30% WPI contributed to an appealing aroma and mouthfeel, making it a nutritional supplement to enhance its protein content while maintaining its fine sensory attributes of gluten-free sponge cake.

Starch Characteristics and Amylopectin Unit and Internal Chain Profiles of Indonesian Rice (Oryza sativa).

Indonesia is arguably a major player in worldwide rice production. Though white rice is the most predominantly cultivated, red, brown, and red rice are also very common. These types of rice are known to have different cooking properties that may be related to differences in their starch properties. Investigating the starch properties, especially the fine structure of their amylopectin, can help understand these differences. This study aims to investigate the starch characteristics of some Indonesian rice varieties by evaluating the starch granule morphology and size, molecular characteristics, amylopectin unit and internal chain profiles, and thermal properties. Starches were extracted from white rice (long grain (IR-64) and short grain (IR-42)), brown rice, red rice, and black rice cultivated in Java Island, Indonesia. IR-42 had the highest amylose content of 39.34% whilst the black rice had the least of 1.73%. The enthalpy of gelatinization and onset temperature of the gelatinization of starch granules were between 3.2 and 16.2 J/g and 60.1 to 73.8 °C, respectively. There were significant differences between the relative molar amounts of the internal chains of the samples. The two white rice and black rice had a significantly higher amount of A-chains, but a lower amount of B-chains and fingerprint B-chains (Bfp) than the brown and red rice. The average chain length (CL), short chain length (SCL), and external chain length (ECL) were significantly longer for the red rice and the black rice in comparison to both the white rice amylopectins. The long chain length (LCL) and internal chain length (ICL) of the sample amylopectins were similar. Rice starches were significantly different in the internal structure but not as much in their amylopectin unit chain profile. These results suggest the differences in their amylopectin clusters and building blocks.

Nutritional and Technological Properties of Albino Peach Palm (Bactris gasipaes) from the Amazon: Influence of Cooking and Drying.

This study aimed to subject the albino peach palm to cooking and drying processes and characterize the raw pulp (RP), cooked pulp (CP), raw pulp flour (RPF), and cooked pulp flour (CPF). The product's chemical composition, bioactive compounds, and physicochemical, color, thermal, morphological, and functional-technological properties were evaluated. The proximate composition showed that carbohydrates were the main constituents of all the products (69.59-72.08 g/100 g). The cooking process decreased the lipids (10.21 to 8.63 g/100 g), dietary fiber (13.64 to 12.81 g/100 g), and total sugar content (59.18 to 49.10 g/100 g) of the CP. The colorimetric parameters indicated a significant browning of the CP and CPF, which can be attributed to the Maillard reaction and lipid oxidation. After cooking, the total phenolic compound and ascorbic acid content decreased in the pulp. The RPF and CPF displayed different thermogravimetric behaviors. The spectral patterns in the infrared region showed the characteristic bands of organic compounds that are present in the structure of starches. The scanning electron microscopy showed amyloplast and fiber bundles with starches in the RP and gelatinized starch granules in the CP and CPF. The RPF presented small and heterogeneous starch granules with isolated amyloplast. The RPF and CPF showed different granulometric patterns and technological indices. The results suggest that the pulp and flour from the pulp of albino peach palms can be exploited by the food, pharmaceutical, and biotechnological industries.

Designing a Specific Pretreatment on Corn Starch to Facilitate Enzymatic Rearrangement of Glycosidic Bonds for Efficiently Reducing Starch Digestibility.

Bacterial 1,4-α-glucan branching enzymes (GBEs) provide a viable strategy for glycosidic bond rearrangement in starch and regulation of its digestion rate. However, the exponential increase in paste viscosity during starch gelatinization has a detrimental effect on the catalytic action of GBEs, thereby limiting productivity and product performance. Here, we designed an enzymatic treatment on corn starch granules by the GBE from Rhodothermus obamensis STB05 (Ro-GBE) prior to the glycosidic bond rearrangement of gelatinized starch catalyzed using the GBE from Geobacillus thermoglucosidans STB02 (Gt-GBE). Specifically, a moderate amount of Ro-GBE was required for the pretreatment stage. The dual GBE modification process enabled the treatment of more concentrated starch slurry (up to 20%, w/w) and effectively reduced starch digestibility. The resulting product contained a rapidly digestible starch fraction of 66.0%, which was 11.4% lower than that observed in the single Gt-GBE-modified product. The mechanistic investigation showed that the Ro-GBE treatment promoted swelling and gelatinization of starch granules, reduced starch paste viscosity, and increased the mobility of water molecules in the starch paste. It also created a preferable substrate for Gt-GBE. These changes improved the transglycosylation efficiency of Gt-GBE. These findings provide useful guidance for designing an efficient process to regulate starch digestibility.

Physicochemical characteristics and retardation effects on in vitro starch digestibility of non-starch polysaccharides in jelly-fig (Ficus pumila L. var. awkeotsang)

The non-starch polysaccharides (NSPs) of two jelly-fig cultivars were extracted to compare their effects on the delay of glucose release and in vitro starch digestion with those of commercial agar. The ability of jelly-fig NSPs to retard glucose diffusion was investigated. The NSPs of both jelly-fig cultivars regulated glucose absorption. The Hongjiu cultivar had the highest rate of α-amylase inhibition (63.17 ± 0.04%). Jelly-fig NSPs reduced amylose leaching by 19–32%. The Hongjiu cultivar showed stronger cholesterol absorption ability compared with other NSPs. In vitro starch digestion indicated that jelly-fig NSPs were beneficial to the retardation of glucose release. The viscosity of jelly-fig NSPs was similar to those in in vitro starch digestion, indicating that the effects of jelly-fig on glucose release were strongly associated with viscosity. Scanning electron microscopy (SEM) indicated that jelly-fig NSP-treated starch granules were densely packed with smooth surfaces. The Hongjiu cultivar starch granules (34.93 μm) were substantially smaller than those of the control group (115 μm), indicating that starch granule gelatinization and swelling were attenuated. The NSPs of Hongjiu cultivar demonstrate potential in retarding glucose release in combination with starch sources to lower their glycemic index. This provides a novel natural source for blood glucose-controlling component in food products.

Effects of Steam and Water Blanching on Drying Characteristics, Water Distribution, Microstructure, and Bioactive Components of Gastrodia Elata.

In the current work, the effects of steam and boiling water blanching on the drying characteristics, water distribution, microstructure, and contents of bioactive substances of Gastrodia elata (G. elata) were explored. Results showed that the degree of steaming and blanching was related to the core temperature of G. elata. The steaming and blanching pretreatment increased the drying time of the samples by more than 50%. The low-field nuclear magnetic resonance (LF-NMR) of treated samples showed that the relaxation time corresponded to water molecule states (bound, immobilized, and free) and G. elata became shorter, which indicated a reduction in free moisture and increased resistance of water diffusion in the solid structure during drying. Hydrolysis of polysaccharides and gelatinization of starch granules was observed in the microstructure of treated samples, which was consistent with changes in water status and drying rates. Steaming and blanching increased gastrodin and crude polysaccharide contents and decreased p-hydroxybenzyl alcohol content. These findings will contribute to a better understanding of the effect of steaming and blanching on the drying behavior and quality attributes of G. elata.

Development of cake by using persimmon fruit (Diospyros kaki) as a fat replacer and its chemical and structural profile analysis

The burgeoning global production of processed foods high in fat, sugar, and salt; and the nutrition transition have catalysed the global burden of non-communicable diseases, which has necessitated the production of foods with limited fat, sugar, and salt content. This study investigated the feasibility of utilising Persimmon sauce (PS) as a fat replacer to develop cake and evaluated its impact on the physicochemical, functional, sensory, and structural profile of the developed cake variants (control (100g fat) and M1, M2, M3 and M4 with 25g, 50g, 75g and 100 g PS I on 100g butter basis, respectively). A significant increase in the moisture and ash content (p < 0.05), total phenolic content (from 540 to 10700 μg GAE/g), and DDPH radical scavenging activity; and linear reduction in fat content (p < 0.05) was observed with increasing Persimmon sauce I (PS I) (without added sugar and lemon) levels in cakes. High sensory acceptability of cakes was noted up to 50 g PS I incorporation level on 100g butter basis. A positive correlation between PS I incorporation level and Vitamin C; and fibre content of the cakes (p < 0.05) was also observed. The microstructural analysis of cakes exhibited a thinner and ruptured protein matrix in fat replaced cakes resulting from gelatinized starch granules. Therefore, Persimmon fruit can be considered as an effective and acceptable substitute for fat replacement and augmentation of functional properties of cake.

Thermal transitions and microstructure of starch‐apple pomace‐based systems

SummaryApple pomace (AP) is the by‐product obtained after juice extraction. It is a potential ingredient for the fibre enrichment of foods. In the present work, AP was combined in gluten free‐mixtures with cassava starch (CS), rice flour (RF), egg white (EW) and sucrose (SR) to analyse its effect on thermal transitions of starch and the batter and bread crumb microstructures. Model systems with all or part of the main ingredients (CS:RF:AP:EW:SR in 4:4:1:1:1 proportions) and a batter formulation with AP were prepared by dry mixing and then dispersing the solids in water. CLSM allowed observing the distribution of egg proteins, AP and RF particles and CS granules. The batter enriched with AP exhibited higher apparent viscosities and dilatant behaviour. Thermal transitions were analysed by DSC. Endotherms ranged between 57 and 97°C. Gluten‐free bread microstructure was analysed by SEM. A more irregular and compact crumb structure was observed when AP was used, with the air cell walls constituted by gelatinized starch granules and AP particles interpenetrating them. By measuring the firmness of crumb along storage, it could be concluded that amylopectin retrogradation was partially inhibited by the presence of AP in model systems but in bread, this inhibiting effect was not evident.

Effects of Potassium Carbonate on Quality Characteristics of Composite Starch‐Wheat Noodles and Its Mechanism

AbstractThis study is to investigate the impact of potassium carbonate on quality characteristics of composite starch‐wheat noodles (CSW). The results show that low level of potassium carbonate (0.2–0.4%) enhances the storage modulus (G') of dough and improves gel strength. The peak viscosity of composite flour is increased at low level of potassium carbonate that is confirmed by pasting properties analysis. Cooking loss of noodles decreases significantly due to the increasing hardness and resilience. The thermodynamic analysis indicates that ΔH decreases by increasing the potassium carbonate. The disulfide bonds (9.604–10.399 µmol g−1), β‐sheet (26.9–31.4%), and starch order increases at low concentration of alkali. Based on the confocal laser scanning microscopic observation, the potassium carbonate (0.2–0.4%) causes a strong protein network in composite starch‐wheat noodles and with gelatinized starch granules being well embedded in the network structure. It is observed that 0.4% potassium carbonate promotes protein aggregation and starch stabilization to improve the elasticity of composite starch‐wheat noodles.

Mechanistic insights into the influence of flavonoids from dandelion on physicochemical properties and in vitro digestibility of cooked potato starch

Flavonoids extracted from a potential edible dandelion were found to exhibit a high level of pancreatic α-amylase inhibitory activity. However, the effects of dandelion flavonoids on starch physicochemical properties and in vitro digestibility have not yet been examined. This study investigated the crystalline characteristics, infrared spectrum, rheology, thermal behavior and microstructure, and enzymatic hydrolysis of cooked potato starch in the presence of dandelion flavonoids, aiming to quantify the interactions between starch and dandelion flavonoids. The textural parameters and moduli of cooked starch pastes decreased significantly with the addition of flavonoids. Compared with the pure starch paste, the starch-flavonoids complex pastes exhibited a looser gel network structure. The digestion rate coefficient ( k ) and terminal digestibility ( C ∞ ) were significantly decreased from 0.119 to 0.083 1/min and 94.6% – 75.8%, respectively, resulting in a significant increase in resistant starch (RS) content in the presence of 10% dandelion flavonoids. The decline in the rate and extent of starch hydrolysis was mainly attributed to the interaction between starch and dandelion flavonoids through non-covalent bonding, as evidenced by XRD and FT-IR data. The interaction might hinder starch digestion by limiting the availability of starch substrate to amylase, as well as restricting gelatinization of starch granules during cooking, which were supported by the increased crystallinity, higher gelatinization temperatures and enthalpy change with flavonoids addition. The present study demonstrates that dandelion flavonoids can potentially be used as a functional additive for making low glycemic index (GI) diets for managing human health. • Interactions between cooked potato starch and dandelion flavonoids were studied. • Hardness and modulus decreased in the starch pastes with the flavonoids added. • Starch hydrolysis decreased with increasing flavonoids addition. • Dandelion flavonoids protected starch from gelatinization during cooking. • The decreased starch hydrolysis mainly due to the formation of flavonoids-starch complex.

Combining robocasting and alkali-induced starch gelatinization technique for fabricating hierarchical porous SiC structures

Hierarchical porous silicon carbide (SiC) structures with total porosity in a wide range of 37.82 %− 94.34 % were achieved by combining robocasting and alkali-induced starch gelatinization technique. (i) 50 µm-2 mm sized pores, with porosities of 22.33 %− 82.13 %, were created by robocasting. (ii) 1–140 µm pores, with porosities of 20.20 %− 68.21 %, were induced by the starch template. Additionally, we firstly introduced an alkali-induced starch gelatinization technique to the gel inks for robocasting, which promoted its elastic properties (storage modulus and shear yield stress) and prolonged its preservation time to 3–7 days. The gelatinized starch granules were also used as binder, which facilitated high-velocity (3–20 mm/s) extrusion of the inks through fine (150–800 µm) nozzles. The porous SiC structures with two scales of porosity are promising for wide applications such as porous burners, liquid and gas filters, catalyst supports and so on.

Determination of the mechanical properties of gelatinized starch granule from bulk suspension characterization

Gelatinized starch granules are soft and deformable particles that are commonly used in food products as texture modifiers. Modelling the flow behavior of such suspensions during industrial processes requires the knowledge of the mechanical properties of the swollen granules; however, such data is usually lacking because of the difficulties inherent to the determination of mechanical properties of particles that are heterogeneous in terms of size and shape. We investigate here the rheological properties of dense suspensions prepared at different volume fractions and by different means (centrifugation, limited water swelling, osmotic compression) to estimate the mechanical properties of an “averaged” starch granule. Results show that starch granule exhibits a rough surface and behave as frictional particles. We compare the shear modulus value determined assuming either frictionless (previous model) or frictional interactions (as suggested by our results), the latter giving shear modulus lower by about one order of magnitude. This study also allows the first estimate of the starch granule bulk modulus, which value is corresponding to a Poisson ratio of 0.47, close to the maximum value of 0.5. The swollen granule shear modulus is also shown to be temperature independent in the range commonly found in industrial processes (20–90 ∘C). These results pave the way toward multiscale mechanistic modelling of the flow of starch suspensions, to derive macroscopic rheological properties from the description of the microscopic granule properties. Estimating starch granule mechanical properties from bulk suspension characterization

Optimization of barley flour and inulin addition for pasta formulation using mixture design approach

The aim of the present work was to optimize the formulation of a new functional pasta containing durum wheat semolina, whole barley flour, and inulin ingredients to enhance both the technological and textural properties of this product using the mixture design approach. Optimally formulated pasta with acceptable technological and textural properties as close as possible to those of control pasta was studied. The microstructure analysis of cooked and uncooked pasta was performed. Cox response trace plots revealed that the increasing amounts of whole barley flour and durum wheat semolina resulted in an increase in the cooking quality parameters and yellowness. However, pasta firmness was negatively influenced by inulin and whole barley flour addition. The ingredient composition of the optimally formulated pasta, which leads to the best technological and textural properties, was 94.8% durum wheat semolina, 3.7% whole barley flour, and 1.5% inulin. This optimal formulation had an optimal cooking time of 335.24 s, a swelling index of 2.15%, and a cooking loss of 10.44%. The firmness values and the color parameters were also satisfactory. The microstructure of the optimally formulated cooked pasta showed the presence of few not gelatinized starch granules incorporated into the protein matrix as compared to the control pasta. PRACTICAL APPLICATION: Three ingredients, durum wheat semolina, whole barley flour, and inulin, were used for the production of new functional pasta using a mixture design approach. The obtained optimally formulated pasta, with good technological and textural properties, was rich in several dietary fibers. This allows the application of whole barley flour and inulin in the cereal industry and can be of interest to the human diet.

Effects of psyllium fiber on in vitro digestion and structure of different types of starches.

Starch digestibility in foods strongly depends on the structure, other ingredients and processing conditions used. This study aimed to investigate the effect of psyllium fiber on gelatinization, crystallinity and in vitro digestibility of starches having different crystalline structures (A, B and C). Wheat, potato and tapioca starches with and without added psyllium fiber were heated at 90 °C for 10min at three different solid:water (w:v) ratios (1:1, 1:2 and 1:5). The added fiber content was 50% (dry base) in the solid fraction for the fiber-added samples. Wheat, potato and tapioca starches showed different structural, morphological and starch digestibility properties. The effect of cooking and fiber addition on starch digestion differed for the starch types, mainly wheat starch. Psyllium addition during cooking decreased the rapidly digestible starch (RDS) fractions while increasing the slowly digestible starch (SDS) and remaining/resistant starch (RS) fractions. The effect of psyllium fiber addition was not limited to restricting the swelling and gelatinization of starch granules during heating. Psyllium fiber effectively restricted the mobility of digestive enzymes during digestion. Understanding the relationship between psyllium and starch digestibility for different types of starch could assist in designing food formulations with lower starch digestibility. These in vitro data, however, should be confirmed by in vivo studies. © 2021 Society of Chemical Industry.

Structuring wheat dough using a thermomechanical process, from liquid food to 3D-printable food material

In extrusion printing, the printability of food materials depends on the rheology of the food under shearing when extruded, and at rest, post-deposition. Piloting food microstructure to provide rheological properties compatible with 3D extrusion printing is a major challenge. Microstructure, rheology, and printability of wheat-flour based materials with varying concentrations of flour, sugar, oil, and water were studied. Materials were obtained by heating and shearing doughs with a moisture content above 55% (wb). The processed doughs were structured as closely-packed particles made of swollen gelatinized starch granules glued in a denatured proteins network. These materials were easily extruded in self-supporting layers by a 3D food-printer and formed stable objects with precise dimensions. The water/flour ratio played a crucial role in the structure of the wheat materials, impacting the storage modulus (G’), tan δ and printability. This work highlights the importance of tan δ in predicting the ability of food materials to hold its 3D structure. • Thermomechanical processing of doughs produced wheat-based printable materials. • Dough particles were made of swollen starch glued by denatured proteins. • In excess of water, oil and sugar had no effect on the rheology or printability. • The water/flour ratio is an important parameter to pilot a material's printability. • Tan δ is a relevant indicator to predict the self-supporting ability of materials.

Impact of superheated steam on the moisture transfer, structural characteristics and rheological properties of wheat starch

Superheated steam treatment (SST) can improve cereal-based foodstuff quality. Starch is the major component of cereal-based foodstuffs, playing a key role in food quality. For understanding the effect of SST on the moisture distribution, lamellar structure and molecular weight of wheat starch, the low-field nuclear magnetic resonance (LF-NMR), small angle X-ray scattering (SAXS) and size exclusion chromatography were employed. Compared with native starch, SST reduced the average thickness of crystalline layer and induced the depolymerization of starch molecules, which were attributed to the limited moisture transfer resulting in the partial gelatinization of starch granules. The structural variations had a synergistic effect on the rheological properties of starch samples. Upon SST, treated samples exhibited a weaker pseudoplasticity behavior and increased the deformability and mobility of gels systems. Furthermore, the lower tanδ values of treated starch samples were observed, indicating that the gels systems tended to the solid-like behaviors.

The effects of molecular fine structure on rice starch granule gelatinization dynamics as investigated by in situ small-angle X-ray scattering

Dynamic changes of rice starch granules selected for different amylose contents were analyzed in excess water while heated in-situ in a small-angle X-ray scattering (SAXS) instrument. Normal rice starch (NS) and rice starch with high amylopectin (HAP) and high amylose (HAM) were used as models. A 1D linear correlation function and a combination power-law and Gaussian function were used to extract the starch lamellar structure parameters and the fractal dimension, ordering and distribution of starch lamellae from SAXS data. For the resulting starch paste/gels, a model of two-correlation length was fitted to afford the correlation length (ξ) for the paste/gel system. The results showed that HAM exhibited higher long period (LP) and thickness of the crystalline layers (dc) values than HAP and NS. However, HAP showed the highest ordering lamellar structure. HAP granules were more thermostable than the amylose containing starches. For the gelatinized starches, HAM showed the highest correlation length values but these notably decreased with increasing temperature indicating strong chain segment interaction. This research reveals essential structural changes in lamellae of rice starch granules and rice starch gel structure, which provides potentially useful in the working of starch-based foods and materials.

Effects of partial preheated dough on its frozen characteristics: Baking, water mobility, thermal, and microstructural properties

AbstractBackground and objectivesFlour heat treatment is commonly used to improve dough and bread quality. This study creatively proposed applying partial preheated dough (PPHD) to frozen dough and evaluated bread characteristics and its internal mechanism systematically.FindingsResults suggested that moderate PPHD level presented higher specific volume, softer hardness, more appealing brown crust color and more uniform texture of frozen dough bread. Moisture status analysis showed that PPHD restricted the mobility of overall water molecules and the migration from bound water to semi‐bound water. DSC and RVA results suggested that the inter‐ and intramolecular association of starch granules, leading to abundant formation of hydrogen bonds, strengthened the gluten matrix network. Besides, gelatinized starch granules in PPHD served as a paste to promote the cross‐linking of starch and gluten, which was observed by SEM.ConclusionsPartial preheated dough inhibited ice recrystallization by restricting water migration and formed a highly networked starch–gluten structure that delayed its destruction during freezing.Significance and noveltyThis study demonstrated obvious improvement of PPHD on frozen dough quality and further explained the mechanism systematically. Moreover, the method was innovative, simple, and easy to operate, so it could help to promote the development of the frozen dough industry.

Microwave drying of germinated brown rice: Correlation of drying characteristics with the final quality

Drying characteristics influence the formation of quality including visual color and gamma-aminobutyric acid (GABA) of germinated brown rice (GBR) subjected to microwave drying. In microwave drying, microwave intensities induced microscopic pores inside GBR to enhance the drying rate in initial stage, while rising temperatures caused gelatinization of starch granules to hinder the drying rate in later stage. The higher microwave intensity resulted in the greater non-uniformity of temperature inside the grain layer, which dominated the moisture content and final quality indexes of GBR. However, the coupling effects of temperature rising and moisture reducing failed to stimulate the glutamate decarboxylase (GAD) activity for the GABA synthesis, but may cause the degradation of GABA. The non-uniformity of microwave drying influenced the evaluation of GABA content in the dried GBR, and the suitable average grain temperature of 64–67 °C may retain relatively high GABA content. The critical temperature for preventing the serious browning and charred kernels inside the grain layer was 132 °C and 170 °C, respectively. Microwave intensity of 3–4 W/g may be suitable for drying of GBR considering high drying efficiency and product quality.