Effect of ethanol addition on the physicochemical, structural and in vitro digestive properties of Tartary buckwheat starch-quercetin/rutin complexes.

The effects of ethanol on the physicochemical, structural and in vitro digestive properties of Tartary buckwheat starch-quercetin/rutin complexes (e-TBSQ and e-TBSR) were investigated. Ethanol restricted the gelatinization of Tartary buckwheat starch (TBS), which resulted an increase in ∆H, G' and G" as well as a decrease in apparent viscosity of e-TBSQ and e-TBSR. The particle size, scanning electron microscopy and X-ray diffraction results showed that ethanol influenced the morphological structure of TBS granules and the starch crystalline structure in e-TBSQ and e-TBSR changed from B-type to V-type when the ethanol concentration was 25%. Saturation transfer difference-nuclear magnetic resonance results revealed that ethanol weakened the binding ability of quercetin/rutin to TBS in e-TBSQ and e-TBSR, leading to a change in the binding site on the quercetin structural unit. The residual ungelatinized TBS granules in e-TBSQ and e-TBSR induced a high slowly digestible starch content, and thus displayed a "resistant-to-digestion".

Milling of buckwheat hull to cell-scale: Influences on the behaviors of protein and starch in dough and noodles.

Superfine grinding of insoluble dietary fiber (IDF) is a promising method to improve the product quality by regulating the interaction between protein and starch. In this study, the effects of buckwheat-hull IDF powder, at cell-scale (50-10 µm) and tissue-scale (500-100 µm), on the dough rheology and noodle quality were investigated. Results showed that cell-scale IDF with higher exposure of active groups increased the viscoelasticity and deformation resistance of the dough, due to the aggregation of protein-protein and protein-IDF. Compared with the control sample, the addition of tissue-scale or cell-scale IDF significantly increased the starch gelatinization rate (ß, C3-C2) and decreased the starch hot-gel stability. Cell-scale IDF increased the rigid structure (ß-sheet) of protein, thus improving the noodle texture. The decreased cooking quality of cell-scale IDF-fortified noodles was related to the poor stability of rigid gluten matrix and the weakened interaction between water and macromolecules (starch and protein) during cooking.

Multi-scale structure and digestive property of bran starch in different particle size wheat bran.

In this study, the multi-scale (granular, molecular, crystalline, lamellar and helical) structure and digestive property of starch isolated from wheat bran of different particle size, including plant scale (1110 µm), tissue scale (235 µm, 83 µm) and cell scale (19 µm), were investigated and compared with wheat flour starch. Bran milling modified bran starch to varying degrees. Tissue-scale milling of bran reduced the granule size of bran starch, but did not significantly modify its molecular, lamellar, crystalline and helical structure. However, cell-scale milling caused significant destruction of crystalline regions and double helix, and increase in starch digestibility. In addition, compared to wheat flour starch, wheat bran starch had more resistant starch and lower digestibility, which were highly correlated with its thinner lamellas, more double helix proportion and compact fractal. This study highlights the effect of supramolecular structure on bran starch digestibility and contributes to the application of bran starch.

Milling of wheat bran: Influence on digestibility, hydrolysis and nutritional properties of bran protein during in vitro digestion.

Wheat bran is a source of high-quality protein with low cost, but the accessibility of bran protein is notably limited by cell wall matrix. This study investigated the effect of milling on the distribution and profile of wheat bran protein, and explored its digestibility, hydrolysis and functional activity during in vitro digestion. It showed that superfine milling effectively released bran protein by disrupting aleurone cells and further improved its solubility and extractability. Superfine wheat bran (19 µm) had higher protein digestibility (53.1 %) and hydrolysis degree (12.7 %) compared to coarse wheat bran (84-1110 µm). Moreover, intestinal digestion promoted the release of free amino acid, mainly arginine (16.4 %), tyrosine (12.8 %) and phenylalanine (9.5 %). Superfine bran protein hydrolysate exhibited the highest antioxidant activity and starch-digestive enzyme inhibitory activity that could facilitate the application of bran as a multifunctional nutrient.

Effect of buckwheat hull particle-size on bread staling quality.

The mechanical grinding scale of insoluble dietary fiber has an important influence on bread staling quality. We investigated the effects of buckwheat hull (BWH) powder at tissue-scale (500-100 µm) and cell-scale (50-10 µm) on the physical and structural changes of bread during storage. The addition of tissue-scale BWH had little effect on loaf volume and crumb firmness of bread, while that of cell-scale BWH significantly decreased specific volume and baking loss, and resulted in higher bread firmness, compared with the control (100 % wheat bread). The effect of cell-scale BWH on delaying amylopectin retrogradation and starch recrystallization during bread storage was superior to that of tissue-scale BWH. Tissue-scale BWH made the gas cell structure of the crumb coarse and open, promoting the evaporation of water during storage. BWH at the cell-scale had a stronger water-binding ability than tissue-scale BWH, which restricted the loss of water, inhibiting bread staling.

Different thermal treatments of highland barley kernel affect its flour physicochemical properties by structural modification of starch and protein.

Highland barley (HB) has become popular due to nutritional benefits, and thermal treatment could broaden its application. In this study, superheated steam (SS) as a novel commercially thermal treatment was compared with other traditional heating (steam and roasting). The physiochemical properties of treated HB kernels and subsequent produced flour were investigated. After thermal treatments, gelatinization enthalpy was decreased by 38.39% and the degree of gelatinization was increased by 38.40%. SS at 180 °C (SS-180) induced the highest thermal stability, lowest viscoelasticity gel and delayed the starch retrogradation compared to other treatments. Meanwhile, SS-180 caused lowest short-range order and relative crystallinity of starch along with changes in protein secondary structure. Particularly, SS-180 decreased damaged starch content by 6.44% due to starch granules closely wrapped by glue-like protein, while steam and roasting increased it by 32.92% and 21.40%, respectively. Overall, SS treatment is most effective to improve the physiochemical properties of HB.

Effect of particle size on the release behavior and functional properties of wheat bran phenolic compounds during in vitro gastrointestinal digestion.

Wheat bran is a rich source of phenolic compounds, and the health benefits of phenolic compounds depend on its bioaccessibility. The release behavior and functional properties of phenolic compounds in different particle size wheat bran during in vitro digestion were investigated. Coarse wheat bran (CWB, 1110.39 µm) was milled by airflow impact mill to produce medium wheat bran (MWB, 235.68 µm), fine wheat bran (FWB, 83.73 µm) and superfine wheat bran (SWB, 19.16 µm). The reduction in particle size increased the release of phenolic compounds, mainly ferulic acid, after digestion. The free p-coumaric acid content in SWB was nearly five times higher than that in CWB, MWB and FWB due to the complete destruction of aleurone cell walls. Moreover, SWB showed higher bioaccessible phenolic compounds content (65.51%) than CWB. The improved phenolic bioaccessibility increased the antioxidant capacities and carbohydrate-digestive enzymes inhibitory activities of SWB and significantly reduced its starch digestibility.

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.

Effect of Moisture Distribution Changes Induced by Different Cooking Temperature on Cooking Quality and Texture Properties of Noodles Made from Whole Tartary Buckwheat.

While precooking and processing have improved the quality of gluten-free noodles, the effects of different cooking temperatures on their quality-neither gluten-free noodles nor whole Tartary buckwheat noodles-have rarely been clarified. This study investigated the key role of moisture distribution induced by different cooking temperatures in improving the noodle quality of whole Tartary buckwheat. The results showed that cooking temperatures higher than 70 °C led to a sharp increase in cooking loss, flavonoid loss and the rate of broken noodles, as well as a sharp decrease in water absorption. Moreover, the noodles cooked at 70 °C showed the lowest rate of hardness and chewiness and the highest tensile strength of all cooking temperatures from 20 °C to 110 °C. The main positive attribute of noodles cooked at 70 °C might be their high uniform moisture distribution during cooking. Cooking at 70 °C for 12 min was determined as the best condition for the quality improvement of whole Tartary buckwheat noodles. This is the first study to illustrate the importance of cooking temperatures on the quality of Tartary buckwheat noodles. More consideration must also be given to the optimal cooking conditions for different gluten-free noodles made from minor coarse cereals.

Anti-diabetic effects of the soluble dietary fiber from tartary buckwheat bran in diabetic mice and their potential mechanisms.

BACKGROUND: Tartary buckwheat has beneficial effects on glucose and lipid metabolism of patients with type 2 diabetes mellitus. However, the physiological effects of a soluble dietary fiber (SDF) from tartary buckwheat have rarely been studied, especially in vivo. OBJECTIVE: This study aimed to examine the hypoglycemic and hypolipidemic effects of SDF from tartary buckwheat bran on high-fat diet/streptozotocin-induced diabetic mice. DESIGN: The SDF of tartary buckwheat bran was collected according to the Association of Official Analytical Chemists method 991.43. Diabetic mice were treated with high-fat diets supplemented with 0.5, 1, and 2% SDF for 8 weeks. Parameters related to glucose and lipid metabolism and relevant mechanisms, including the excretion of short-chain fatty acids and the glycemic signaling pathway in the liver, were investigated. In addition, the structural characterization of a purified polysaccharide from SDF of tartary buckwheat bran was illustrated. RESULT: Supplementation with SDF in the diet resulted in reduced levels of fasting blood glucose, improved oral glucose tolerance, increased levels of liver glycogen and insulin, as well as improved lipid profiles in both the serum and liver, in diabetic mice. The amelioration of glucose and lipid metabolism by SDF was accompanied by an increase in the short-chain fatty acid levels in the cecum and co-regulated by hepatic adenosine-5'-monophosphate-activated protein kinase (AMPK) phosphorylation. A neutral tartary buckwheat polysaccharide with an average molecular weight of 19.6 kDa was purified from the SDF, which consisted mainly of glucose with α-glycosidic bonds. CONCLUSIONS: The SDF of tartary buckwheat bran exhibits hypoglycemic and hypolipidemic effects in diabetic mice, contributing to the anti-diabetic mechanisms of tartary buckwheat.

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.

Combined transcriptomic and proteomic analysis of the response to bile stress in a centenarian-originated probiotic Lactobacillus salivarius Ren.

Tolerance to bile stress is a crucial property for probiotics to survive in the gastrointestinal tract and exert their beneficial effects. In this work, transcriptomic analysis combined with two-dimensional electrophoresis revealed that the transcript levels of 129 genes and the abundance of 34 proteins were significantly changed in Lactobacillus salivarius Ren when exposed to 0.75 g/L ox-bile. Notably, carbohydrate metabolism shifted to the utilization of maltose and glycerol for energy production, suggesting that L. salivarius Ren expanded carbon sources profile for gut adaptation in response to bile. Moreover, the enzymes involved in cell surface charge modification and the cell envelope-located hemolysin-like protein were overproduced, which was supposed to hinder the penetration of bile. Then, the up-regulated ABC transporters could contribute to the extrusion of bile accumulated in the cytoplasm. Additionally, proteolytic system was activated to provide more amino acids for the synthesis and repair of proteins damaged by bile. Finally, γ-glutamylcysteine with antioxidant activity and oxidoreductases for redox homeostasis were increased to cope with the bile-induced oxidative stress. These findings provide new insights into the molecular mechanisms involved in bile stress response and adaptation in L. salivarius.

Global transcriptomic analysis of Lactobacillus plantarum CAUH2 in response to hydrogen peroxide stress.

To overcome the deleterious effects of hydrogen peroxide, Lactobacillus plantarum elicits an adaptive response to oxidative stress. In this study, global transcriptomic analysis revealed that L. plantarum CAUH2 expanded its carbon source utilizing profile and enhanced glycolysis to produce more ATP to confront with H2O2 stress. Some antioxidant enzymes including NADH peroxidase, thioredoxin reductase and glutathione peroxidase were 6.11, 36.76 and 6.23-fold up-regulated at transcription level for H2O2 scavenging. Meanwhile, free ferrous iron (Fe2+) was maintained at low concentrations in the cytoplasm, which could limit Fenton reaction and reduce the production of hydroxyl radicals. To repair DNA lesion caused by H2O2, both base excision repair system and recombinational DNA repair pathway were employed by L. plantarum CAUH2. In addition, the expression of methionine sulfoxide reductases and thioredoxin were up-regulated to repair oxidized proteins. It is noteworthy that some transcriptional regulators (Spx, CcpA and MarR1) were predicted to participate in the adaptive response to H2O2 stress, suggesting that L. plantarum CAUH2 utilized a wide array of sensors to monitor oxidative stress and modulated the transcriptional regulation network under H2O2 stress. These findings provide novel insight into the protective mechanisms developed by L. plantarum to cope with oxidative stress.

Impact of whole cereals and processing on type 2 diabetes mellitus: a review.

The prevalence of type 2 diabetes mellitus (T2DM) has been increasing throughout the world. The cereals, as the high carbohydrate food and dominant portion of diet, have crucial impacts on glycemic control, especially for T2DM. Both components in whole cereals and processing are closely related to their glycemic response. The consumption of whole cereals is shown to reduce the risk of T2DM. The starch characteristic of cereal determines its hydrolysis rate and glycemic response. The soluble and insoluble dietary fiber, phenolic compounds, and other bioactive constituents may slow down the starch hydrolysis. Besides, they have other physiological mechanisms in regulation of T2DM, such as amelioration of lipid disorder, antioxidant, anti-inflammation, and regulation of gut microbiota, which contribute to further improvement of metabolic symptoms. Cereals are subjected to processing before consumption, which is involved in mechanical force, bioprocessing, thermal treatment, and cooling. The processing induces changes in nutritional composition and physical structure compared to the raw kernels. The key influences of processing on glycemic response are the starch gelatinization and starch retrogradation. However, physical structure of cereal and interactions among starch and other compounds greatly contribute to various glycemic responses of cereal products. This review highlights recent findings on the influences of both bioactive constituents and processing on the antidiabetic effects and physiological properties of cereals.

Effect of sodium tripolyphosphate incorporation on physical, structural, morphological and stability characteristics of zein and gliadin nanoparticles.

With the extensive applications of chemical means in food systems, phosphorylation has become a promising approach to modify the functionalities of proteins. In this study, effects of sodium tripolyphosphate (TPP) on physicochemical properties of gliadin and zein nanoparticles were comprehensively explored by fluorescence spectroscopy analysis, circular dichroism spectrum and Fourier transform infrared analysis. The results suggested that an increase in TPP concentration could affect the particle size and microstructures of gliadin nanoparticles through enhanced repulsion force among nanoparticles. The phosphorylation of gliadin and zein was ascribed to the interactions of phosphate groups, i.e., tryptophan and tyrosine residues, respectively. FTIR analysis revealed that the intermolecular interactions were influenced with the secondary structure altered. More specifically, both PO and PO bonds were incorporated into gliadin and zein molecules when TPP concentration was above 0.3 mg/mL, which could then improve physical stability of prolamin nanoparticles. Moreover, CNP and COP bonds were deduced to be formed only with the existence of gliadin, whose presence nevertheless enhanced the emulsifying property of nanoparticles. These profound findings could therefore expand the application of prolamin in delivery systems.

Dietary tartary buckwheat intake attenuates insulin resistance and improves lipid profiles in patients with type 2 diabetes: a randomized controlled trial.

Tartary buckwheat (TB) is rich in protein, dietary fiber, and flavonoids and has been reported to affect type 2 diabetes mellitus (T2DM) in animal experiments, but limited information on the benefit of TB as a whole food in T2DM patients is available. Thus, we tested the hypothesis that a daily replacement of a portion of the staple food with TB will improve risk factors of T2DM, including fasting glucose, insulin resistance, and lipid profile. In a parallel, randomized, open-label, controlled trial, 165 T2DM patients were randomly assigned to a control diet group (DC group; systematic diet plans and intensive nutritional education) or a TB intervention group (TB group; daily replacement of a portion of staple food with TB food). Blood samples and diet information were collected at baseline and after 4 weeks of intervention. The TB group decreased fasting insulin (2.46-2.39 Ln mU/L), total cholesterol (5.08-4.79 mmol/L), and low-density lipoprotein cholesterol (3.00-2.80 mmol/L) compared with the DC group at 4 weeks (P<.05). No significant differences in blood glucose or glycated hemoglobin levels were noted between the TB and DC groups. In addition, subgroup analyses based on daily TB intake dose showed a reduction in insulin, total cholesterol, and low-density lipoprotein cholesterol, but also insulin resistance was observed when TB intake dose was greater than 110 g/d. These results support the hypothesis that TB may improve insulin resistance and lipid profile in T2DM patients.

Protective effect of tartary buckwheat on renal function in type 2 diabetics: a randomized controlled trial.

Tartary buckwheat (TB) has been reported to be associated with a decreased risk of type 2 diabetes mellitus (T2DM), and T2DM has had a major impact on the development of diabetic kidney disease (DKD). Thus, the hypothesis that a daily intake of TB will improve DKD risk factors, including urinary albumin to creatinine ratio (UACR), urea nitrogen (UN), serum creatinine, and uric acid was tested. In a parallel, randomized, open-label controlled trial, 104 T2DM patients were randomly assigned to a diet control group (systematic diet plans and intensive nutritional education) or a TB intervention group (daily replacement of a portion of staple foods with TB foods). Blood samples and dietary information were collected at baseline and the end of the 4-week study. The primary outcomes were that TB significantly decreased the rela tive changes in UACR (2.43-2.35, logarithmic transformed mg/g creatinine) and UN (5.12-4.91 mmol/L) in the TB intervention group vs the diet control group at 4 weeks (P<0.05), without obvious effect on blood glucose during the 4-week study. In addition, subgroup analyses based on different DKD stages also showed a significant reduction in UACR and UN for the T2DM patients with normoalbuminuria and microalbuminuria (P<0.05). These results support the hypothesis that TB as a replacement of staple food probably alleviates renal dysfunction in T2DM patients.

Determination of rheological property and its effect on key aroma release of Shanxi aged vinegar.

The rheological property of Shanxi aged vinegar (SAV) was determined by rheometer, and its effects on release in eight key aroma components of SAV was investigated by SPME-GC-MS. In order to simulate the change of rheological property of SAV, a modified SAV system was developed from a finished SAV using carboxymethylcellulose, pectin, glucose, fructose, sodium chloride and tannic acid at indicate levels. The consistency coefficients (K) of SAV ranged from 1.09e-5 to 0.0137, which was correlated to glucose, polyphenol, acids and oBx. SAV changed from shear-thickening to Newtonian fluid during long-time ageing. In the modified SAV system, the K values increased significantly, and two modified vinegar became quasi-Newtonian fluids too. Furthermore, release of the eight key aroma compounds decreased significantly and decreased was pronounced, for acetic acid, furfural and tetramethylpyrazine. The results demonstrated rheological property correlated to the concentrate of sugar, salt, polyphenol, acids and macromolecule, which significantly affected the release of major aroma compounds.

Development of a SPME-GC-MS method for the determination of volatile compounds in Shanxi aged vinegar and its analytical characterization by aroma wheel.

A solid-phase microextraction followed by gas chromatography-mass spectrometry method was developed to determine the volatile compounds in Shanxi aged vinegar. The optimal extraction conditions were: 50 °C for 20 min with a PDMS/DVB fiber. This analytical method was validated and showed satisfactory repeatability (0.5 %

New insights into the antioxidant activity and components in crude oat oil and soybean oil.

Developing new antioxidants and using natural examples is of current interest. This study evaluated the antioxidant activities and the ability to inhibit soybean oil oxidation of oat oil obtained with different solvents. Oat oil extract obtained by ethanol extraction gave the highest antioxidant activity with a DPPH radical (1,1-diphenyl-2-picrylhydrazyl) scavenging activity of 88.2 % and a reducing power (A 700) of 0.83. Oat oil extracted by ethanol contained the highest polyphenol and α-tocopherol content. Significant correlation was observed between the total polyphenol contents, individual phenolic acid, α-tocopherol, and DPPH radical scavenging activity. Soybean oil with 2 % added oat oil showed low malondialdehyde content (8.35 mmol mL(-1)), suggesting that the added oat oil inhibited oxidation. Oat oil showed good antioxidant activity, especially when extracted with ethanol which could also retard the oxidation of soybean oil . DPPH radical scavenging activity was the best method to evaluate the antioxidant activity and components of oat oil.