Tartary Buckwheat Starch Research Articles

In vitro starch digestibility of buckwheat cultivars in comparison to wheat: The key role of starch molecular structure

The objective of this study was to compare the in vitro digestibility of different buckwheat and wheat starch cultivars and establish the relationship between digestibility and structure of buckwheat starch. Structure of starches were analyzed with size exclusion chromatography and fluorophore-assisted capillary electrophoresis. Results showed that the amylose content of Tartary buckwheat starch (TBS) and common buckwheat starch (CBS) was 3–4% lower than that of wheat starch. However, no significant difference in the digestibility was found between them. The fast digestion rate coefficient of TBS was negatively correlated with the amount of long amylopectin chains (24 < DP ≤ 36), and the total digested starch percentage of CBS was negatively correlated with the amount of medium-long amylopectin chains (13 < DP ≤ 24). This suggests that the digestibility of fully gelatinized starch had no association with the botanical sources but may be more influenced by starch structure.

Comparison of quercetin and rutin inhibitory influence on Tartary buckwheat starch digestion in vitro and their differences in binding sites with the digestive enzyme

Inhibitory effects of flavonoids on starch digestibility were well known, but the structural mechanism was not clear. This study was focused on the diverse effect of quercetin and rutin on digestibility of Tartary buckwheat starch. Results showed that quercetin and rutin reduced the starch digestion by altering starch structure in bound forms and inhibiting digestive enzyme activity in free forms simultaneously, and quercetin showed a stronger effect than rutin. Molecular docking and saturation transfer difference-nuclear magnetic resonance (STD-NMR) revealed different binding site of rutin from quercetin was due to its hydroxyl and hydrogen on the glycoside structure. Rutin interacted with enzymes mainly by CH and OH on the glycoside structure which induced steric hindrance and restricted the inhibitory effect of quercetin fraction. The glycoside structure weakened inhibition of rutin on digestive enzymes in free forms rather than influence its anti-digestive effects in bound forms with starch.

Physical modification on the in vitro digestibility of Tartary buckwheat starch: Repeated retrogradation under isothermal and non-isothermal conditions

The effects of repeated retrogradation (RR, range from 1 to 3 times) at different temperatures (4 °C; 4/25 °C, with a 24 h interval; 25 °C) on the in vitro digestibility and structures of Tartary buckwheat starch (TS) were investigated in this study. Results demonstrated that TS treated by RR for 1 time under 4/25 °C contained the maximum content of slowly digestible starch (SDS, 35.25%); TS treated by RR for 3 times under 25 °C contained the maximum content of resistant starch (RS, 54.92%). As the increase of RR cycle times, the value of relative crystallinity, the ratios of 1047/1022 cm−1 and 995/1022 cm−1 increased, the starch pore wall thickened, and more smooth fragments appeared (observed by scanning electron microscope), while the value of melting temperature range trended to decrease. The crystallization type of TS changed from type “A” to a mixture of “B + V” after retrogradation treatment. Pearson correlation analysis revealed that the content of rapidly digestible starch (RDS) was negatively correlated with the ratio of 995/1022 cm−1, transition temperatures, and enthalpy (P < 0.05). These results would supply a potential method for the preparation of starch with slow-digesting properties, also improve the utilization and expand the application of TS.

The effects of extruded endogenous starch on the processing properties of gluten-free Tartary buckwheat noodles

The lack of gluten in Tartary buckwheat has always been the main limiting factor of their development. This paper explored how to improve the processing quality of gluten-free Tartary buckwheat noodles (GF-TBNs) by introducing extruded starch into Tartary buckwheat flour (TBF) and the underlying mechanism was also elucidated. Extruded Tartary buckwheat starch (ETBS) was obtained under different extrusion conditions. The thermal properties, molecular weight, and viscosity of ETBS were examined to determine the key parameters closely related to the water distribution and rheological properties of the dough sheet, and tensile properties of GF-TBNs. The results showed that ETBS with a low molecular weight and high viscosity contributed greatly to the GF-TBNs with good tensile properties. It is proposed that ETBS with a low molecular weight and high viscosity might form a gel-entrapped network inside GF-TBNs, which was confirmed by the morphology of GF-TBNs.

Effect of quercetin on the in vitro Tartary buckwheat starch digestibility

Tartary buckwheat is one of the few pseudocereals with abundant flavonoids and starch. However, there are different views on the digestibility of Tartary buckwheat starch (TBS) because of its particle size and structure. In this study, fluorescence spectrum methods and enzymatic kinetics were used to investigate the interaction between TBS /two glycosidase (α-amylase and α-glucosidase) and quercetin to explore its digestive properties and provide a perspective regarding the application of TBS in functional starch products. The results showed that the interaction between TBS and quercetin was probably weak hydrophobic force and hydrogen bonding. The inhibitory effect of quercetin on α-amylase was better than that on α-glucosidase. The half inhibitory concentrations (IC50) of quercetin to α-amylase and α- glucosidase was (270 ± 3.31) and (544 ± 9.01) μg/mL, respectively. The intrinsic fluorescence of two enzymes was statically quenched by forming a complex with quercetin. Quercetin also increased the microenvironment hydrophilicity of tryptophan residues in glycosidase. In vitro digestion experiment demonstrated that quercetin and TBS co-gelatinized together was more effective to inhibit TBS hydrolysis than quercetin itself alone. In the first-order kinetic and LOS model, quercetin-starch gel structure and quercetin inhibitory activity against enzymes had synergistic effects of the TBS digestion.

Study on the structure and digestibility of high amylose Tartary buckwheat (Fagopyrum tataricum Gaertn.) starch-flavonoid prepared by different methods.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is the only food rich in flavonoid bioactive substances in grains. Studies have shown that flavonoids interaction with amylose has an important impact on the physical and chemical properties and structure of starch. In this study, Tartary buckwheat was used as a raw material. It was then threshed with pullulanase, and a high amylose Tartary buckwheat starch flavonoid complex (HBS/BF) was prepared by physical mixing (PM), water bath treatment (WT), acid-base precipitation (AP), microwave treatment (MT), and ultrasonic treatment (UT); the physical and chemical properties were then evaluated. The results show that HBS/BF-UT and HBS/BF-MT have a higher iodine binding rate than HBS/BF-PM; X-ray diffraction results show that HBS/BF-AP has a V-type crystal form, but the relative crystallinity was reduced. Fourier infrared spectroscopy showed that there is no new covalent bond between Tartary buckwheat starch and flavonoids. In vitro digestion showed that adding flavonoid significantly increased the digestibility of Tartary buckwheat starch. PRACTICAL APPLICATION: These results will provide a theoretical basis for further starch anti-digestion mechanisms and the preparation of resistant starch. These steps will provide insights into the application of Tartary buckwheat starch and flavonoids in the food industry.

Evaluation studies on effects of quercetin with different concentrations on the physicochemical properties and in vitro digestibility of Tartary buckwheat starch

The effects of polyphenols on the physicochemical properties and in vitro digestibility of Tartary buckwheat starch (TBS) remain scarce. In this study, the rheological, thermal properties, and in vitro digestibility of pregelatinized TBS (pre-TBS) with quercetin complexation at various concentrations were characterized. It was found that quercetin complexation increased the shearing resistance and viscosity of pre-TBS. Both SEM and TGA results revealed a more compact and stable structure of starch-quercetin complex in comparison to pre-TBS. The non-inclusive complex with higher crystallinity was formed through hydrogen bonds, which showed by XRD and FT-IR results. Additionally, complexes exhibited the lower digestion rate and digestion velocity constant, and the resistant starch content of complex (with 10% quercetin addition) was the highest. Therefore, quercetin complexation could improve the thermal and rheological properties, and decrease in vitro digestibility of pre-TBS, which could provide a theoretical basis for functional food development.

Rheological, thermal and in vitro digestibility properties on complex of plasma modified Tartary buckwheat starches with quercetin

Starch-polyphenols complex with unique physicochemical and functional properties has gained research interests. As a method of physical modification, plasma treatment leads to smaller fragments of starch, which increases the possibility of binding with polyphenols. In this study, pregelatinized plasma-modified Tartary buckwheat starch (pre-TBS-P), as a new material, was combined with quercetin forming complexes (pre-TBS-P-Q). The rheological and thermal properties, and digestibility of pre-TBS-P-Q were investigated. Results show that quercetin complexation increased the consistency coefficient and decreased the flow behavior index. A more compact and stable structure after combining quercetin was observed using SEM and TGA. The results of XRD and FT-IR identified that quercetin was bound to starch through hydrogen bonds, forming the non-inclusive complex with higher crystallinity. Compared with pregelatinized Tartary buckwheat starch (pre-TBS), the digestion rate of both pre-TBS-P and pre-TBS-P-Q decreased. The velocity constant in the first-order digestion ranked as pre-TBS < pre-TBS-P < pre-TBS-P-Q. Conclusively, using the combination of plasma treatment and complexation with quercetin, the digestion velocity of pre-TBS-P-Q complex decreased due to the increased viscosity of starch solution, as well as, the enhanced crystallinity and compactness of starch granules.

Diverse effects of rutin and quercetin on the pasting, rheological and structural properties of Tartary buckwheat starch

We investigated the interactions of two main phenolics, rutin and quercetin, with starch, the primary component of Tartary buckwheat. The addition of rutin or quercetin significantly affected the structural and physicochemical properties of the starch, and rutin showed a stronger effect than quercetin, particularly at a dose of 6% (w/w). Rutin better enhanced the aggregation of starch pastes and gel formation than quercetin according to our pasting, rheological and thermal property analyses. A scanning electron microscopy analysis of its morphology showed that rutin was more easily dispersed in starchy matrix than quercetin and acted as rigid fillers for gels. The nuclear magnetic resonance results showed different binding sites due to the steric hindrance of the rutin disaccharide groups (rutinose). These findings provide fundamental information about applying rutin during the whole grain processing of Tartary buckwheat.

Effects of phosphate fertiliser on the physicochemical properties of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) starch

Phosphate fertilisation affects the growth, development and quality of Tartary buckwheat. In this study, the effect of different phosphorus levels, including 0, 15, 75, and 135 kg/ha (non-, low-, medium-, and high-phosphorus levels, respectively), on the characteristics of starch from Tartary buckwheat were investigated in 2015 and 2017. With increased phosphorus level, the median diameter of starch granules and the apparent amylose content initially decreased and then increased. All starch samples showed the features of A-type X-ray diffraction patterns. Starches under medium-phosphorus treatment showed higher relative crystallinity than those under non-phosphorus treatment, as well as the highest solubility, gelatinisation enthalpy and transmittance among all starches. Starches under low-phosphorus treatment exhibited higher pasting properties than those under non-phosphorus treatment. This research revealed that phosphorus treatments and year significantly affected the physicochemical properties of Tartary buckwheat starch, and can provide information for the applications of starch in the food and non-food industries.

Regulatory Function of Buckwheat-Resistant Starch Supplementation on Lipid Profile and Gut Microbiota in Mice Fed with a High-Fat Diet.

Buckwheat-resistant starch (BRS) has shown to be a nutrient capable of lowering cholesterol and reducing obesity. In this study, the regulatory effects of tartary buckwheat starch on blood lipid level and gut microbiota (Lactobacillus, Bifidobacterium, Enterococcus, and Escherichia coli) in mice fed with a high-fat diet was investigated. Male C57BL/6 mice were separately fed with a normal diet (CON), a high-fat diet (HFD), and high-fat diet supplemented with buckwheat-resistant starch (HFD+BRS) for 6 weeks. After the feedings, lipid profile, blood glucose, plasma levels of cytokines, short-chain fatty acid content in the colon and intestinal flora of fecal were measured. Furthermore, the antioxidant indices of the liver and duodenum tissues were measured to evaluate the antioxidant capacity of mice. Significantly reduced plasma levels of total cholesterol (TC), triglyceride (TG), glucose, and cytokines were observed in the HFD+BRS group, accompanied by an increased antioxidant capacity in the liver and duodenum. In addition, supplementation with BRS significantly inhibited the increase in plasma lipopolysaccharide, tumor necrosis factor-α, and interleukin-6 levels. Gut microbiota composition was regulated by the supplement of BRS, which promoted the growth of Lactobacillus, Bifidobacterium, and Enterococcus, as well as inhibited the growth of Escherichia coli. In contrast to the HFD group, the content of short-chain fatty acids in mice colon increased in the BRS group. In conclusion, BRS benefited the cholesterol and glucose metabolism, as well as optimized gut microbiota composition in mice fed with a high-fat diet. PRACTICAL APPLICATION: This study identified the beneficial effects of tartary buckwheat-resistant starch on the regulation of blood lipids and intestinal flora in mice fed a high-fat diet. The result of this study will provide a basis for the development of probiotic products supplemented with tartary buckwheat-resistant starch and direction for further research.

Effects of nitrogen level on the physicochemical properties of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) starch.

Nitrogen is an essential nutrient for Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) because this substance affects the yield and quality of Tartary buckwheat. The physicochemical characteristics of starch represent the important parameters of Tartary buckwheat quality. The effects of different levels of nitrogen application at different levels (0, 45, 135 and 225kg/ha in 2015 and 0, 90, 180 and 270kg/ha in 2017) on the physicochemical characteristics of Tartary buckwheat starch were studied. The amylose content, particle size and retrogradation of Tartary buckwheat starch with nitrogen were lower than those of without nitrogen. The structure complexity, pasting temperature, gelatinization enthalpy, relative crystallinity, light transmittance and solubility of the former were higher than those of the latter. Nitrogen application did not change the 'A'-type crystalline pattern of Tartary buckwheat starch. This study indicated that nitrogen level and years and the interactions among nitrogen fertilizer levels and years significantly affected the physicochemical properties of Tartary buckwheat starch. These integrated results also provided information about the management of fertilization conditions to obtain starches with special properties for applications in food or nonfood industries.

Thermal, structural and textural properties of amaranth and buckwheat starches.

Starches isolated from amaranth and buckwheat were analysed for thermal characteristics, crystallinity, gel textural properties and light transmittance. Buckwheat starch gels were harder with higher chewiness and springiness than amaranth starch gels. Starch from common buckwheat produced the hardest gel and amaranth starch from VL-44 cultivar produced the softest gel. Gelatinisation temperatures of amaranth and buckwheat starches differed significantly and tartary buckwheat starch showed the highest values for TP and TC. Buckwheat starches showed lower enthalpy change values than amaranth starches of both the cultivars. X-ray diffractometry confirmed 'A' type crystalline pattern for all tested starch samples and higher relative crystallinity was noticed in amaranth starches than buckwheat starches. Tartary buckwheat exhibited the lowest value of relative crystallinity and amaranth starch of Durga cultivars showed the highest value of relative crystallinity. FTIR spectrums showed band at similar wavenumbers (cm-1) with varying intensities. A declining order of paste clarity during storage at refrigeration temperature was observed for all starches.

Effect of rutin and quercetin on the physicochemical properties of Tartary buckwheat starch

Tartary buckwheat is rich in phenolics and is an excellent healthy food source. To evaluate the endogenous phenolics affecting the physicochemical properties of the starch in Tartary buckwheat products during processing, varying concentrations (0.5, 1.0, and 1.5%) of the predominant phenols, rutin and quercetin, were co‐cooked with Tartary buckwheat starch (TBS). Rutin and quercetin reduced the peak and final temperatures and enthalpy of TBS during gelatinization, lowered the aging enthalpy of retrograded TBS, and increased the trough and final viscosity of TBS paste and reduced its breakdown. The two additives also reduced the hardness and cohesiveness of TBS gels, while improving their water‐binding capacity. The morphologies of gelatinized and retrograded TBS were greatly altered with the presence of rutin and quercetin. The interaction between rutin or quercetin and TBS may be responsible for these changes, and the starch–phenolic binding force was much weaker than that in the iodine–starch complex. Our study provides insight into the physicochemical effects of the phenol–starch interactions in the Tartary buckwheat food matrix in a model system.

Differences in physicochemical properties and in vitro digestibility between tartary buckwheat flour and starch modified by heat-moisture treatment

Native tartary buckwheat starch (NTBS) and native tartary buckwheat flour (NTBF) were modified by heat-moisture treatment (HMT) with different moisture levels (200, 250, 300, and 350 g/kg) to investigate the effect of HMT on their physicochemical properties and in vitro digestibility. Compared to native samples. The onset, peak, conclusion temperatures of HMT-modified samples increased, while the pasting viscosities, enthalpy decreased. After HMT, the gel hardness of starch and flour decreased by 262 and 62.1 g, respectively. But the slowly digestible starch (SDS) content of starch and flour increased by 71.3 and 27 g/kg, respectively, meanwhile the resistant starch (RS) content of starch and flour increased by 23.8 and 41 g/kg, respectively. HMT did not change the A type crystalline pattern of NTBS and NTBF, but the relative crystallinity of NTBS and NTBF increased by 16% and 7%, respectively. HMT had a far greater effect on morphology and pasting properties on flour than on starch. The granule morphology was noticeably changed by HMT, HMT created more cavities and holes on the surface of HMT flours than HMT starches. The results showed that HMT greatly modified the physicochemical properties and in vitro digestibility of NTBS and NTBF to expand their application range.

In vitro digestibility and changes in physicochemical and textural properties of tartary buckwheat starch under high hydrostatic pressure

High hydrostatic pressure (HHP) treatment, a nonthermal processing technology, was carried out to assess how this method affects the in vitro digestibility, physicochemical properties, and textural properties of tartary buckwheat starch (TBS). Pressurization at 120–480 MPa did not change the ‘A’-type crystalline pattern of TBS. However, HHP treatment at 600 MPa contributed to a similar ‘B’-type pattern. HHP treatment resulted in TBS granules with rough surfaces. Amylose content, pasting temperature, and thermostability significantly increased with increasing pressure, while relative crystallinity, swelling power, hardness, and viscosity decreased. Compared with native starch, HHP-modified TBS had lower in vitro hydrolysis, reduced amount of rapidly digestible starch, as well as higher levels of slowly digestible starch and resistant starch. These results suggest that HHP can efficiently modify the in vitro digestibility, physicochemical properties, and textural properties of TBS.

Changes in physicochemical properties and in vitro digestibility of tartary buckwheat and sorghum starches induced by annealing

Annealing (ANN) was applied in this study to investigate its effects on the physicochemical properties and in vitro digestibility of tartary buckwheat starch (TBS) and sorghum starch (SS). In practice, ANN did not change the typical “A” type X‐ray diffraction pattern of TBS and SS. However, it induced increases in amylose content, relative crystallinity, water absorption capacity, gelatinization temperature, and the enthalpy of the two starches. Both solubility and swelling power were temperature dependent and progressively decreased after ANN. Meanwhile, marked reductions were observed in peak viscosity and oil absorption capacity of annealed TBS and SS. Except for these properties, both the slowly digested starch and resistant starch contents significantly increased. Decreases in rapidly digested starch content and total hydrolysis also occurred simultaneously. The results clearly indicate that ANN efficiently altered the properties of TBS and SS to improve their thermal stability and health benefits potential.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) starch, a side product in functional food production, as a potential source of retrograded starch

A starch rich fraction is a side product in Tartary buckwheat processing. This study investigated the fractions that are of technological and nutritional interest. Tartary buckwheat starch granules had a diameter of 3–14μm, and presented a typical type “A” X-ray diffraction pattern. They contained nearly 39.0% amylose. The solubility of Tartary buckwheat starch was much lower at 70–90°C (ranging within 9.9–10.4% at 90°C) than that in maize (up to 49.3%) and potato (up to 85.0%) starch. The starch of one variety of Tartary buckwheat had significantly lower solubility at 70°C and 80°C than that of common buckwheat. The starch peak viscosity and breakdown were higher and pasting time was shorter in Tartary buckwheat than in that of the starch of common buckwheat. Tartary buckwheat starch had unique pasting and physicochemical properties, and is thereby capable of being exploited as a suitable raw material of retrograded starch in food processing.

Physicochemical and textural properties of tartary buckwheat starch after heat–moisture treatment at different moisture levels

Tartary buckwheat, which has nutritional and health benefits, has been consumed in China for so many years. However, its predominant component, starch, limits the application range of tartary buckwheat in the food industry. In this study, tartary buckwheat starch (TBS) was extracted and subjected to heat–moisture treatment (HMT) at different moisture levels (20–35%). Both the solubility and swelling power of native starch significantly decreased following HMT. In HMT‐modified TBS, oil absorption capacity decreased and water absorption capacity increased with increasing moisture level. The typical A‐type X‐ray diffraction pattern of native starch was not affected by HMT. Gelatinization temperature, gelatinization temperature range, and relative crystallinity increased with increasing moisture level. However, peak viscosity, gelatinization enthalpy, hardness, and adhesiveness of starch gels significantly decreased with moisture level. These results revealed that the structure and physicochemical properties of TBS can be modified by HMT to improve its thermal stability and extend its application range.

Identification and characterization of granule bound starch synthase I (GBSSI) gene of tartary buckwheat (Fagopyrum tataricum Gaertn.)

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is increasingly considered as an important functional food material because of its rich nutraceutical compounds. Reserve starch is the major component of tartary buckwheat seed. However, the gene sequences and the molecular mechanism of tartary buckwheat starch synthesis are unknown so far. In this study, the complete genomic sequence and full-size cDNA coding tartary buckwheat granule-bound starch synthase I (FtGBSSI), which is responsible for amylose synthesis, were isolated and analyzed. The genomic sequence of the FtGBSSI contained 3947 nucleotides and was composed of 14 exons and 13 introns. The cDNA coding sequence of FtGBSSI shared 63.3%–75.1% identities with those of dicots and 56.6%–57.5% identities with monocots (Poaceae). In deduced amino acid sequence of FtGBSSI, eight motifs conserved among plant starch synthases were identified. A cleavage at the site IVC↓G of FtGBSSI protein produces the chloroplast transit sequence of 78 amino acids and the mature protein of 527 amino acids. The FtGBSSI mature protein showed an identity of 73.4%–77.8% with dicot plants, and 67.6%–70.4% with monocot plants (Poaceae). The mature protein was composed of 20 α-helixes and 16 β-strands, and folds into two main domains, N- and C-terminal domains. The critical residues which are involved in ADP and sugar binding were predicted. These results will be useful to modulate starch composition of buckwheat kernels with the aim to produce novel improved varieties in future breeding programs.