Insights into the effect mechanism of acidic pH condition on the in vitro starch digestion of black highland barley semi-dried noodles.

In this study, black highland barley semi-dried noodles (BHBSNs) were adjusted to acidic pH (5.0, 4.5, 4.0) with an acidity regulator (monosodium fumarate) for obtaining low glycemic index (GI) BHBSNs, and the changes in the in vitro starch digestion, free phenolic content, and α-amylase activity in BHBSNs were investigated. The estimated glycemic index (eGI) of BHBSNs decreased from 59.23 to 52.59, 53.89 and 53.61, respectively, as the pH was adjusted from 6.0 to 5.0, 4.5, 4.0. As the pH of BHBSNs decreased, the equilibrium hydrolysis (C∞) decreased, and kinetic coefficient (k) decreased and then increased. Compared to the control, the pH of the digestive fluid decreased during digestion with decreasing pH, and the α-amylase inhibition of BHBSNs with pH 5.0, 4.5, and 4.0 increased by 56.54 %, 75.18 %, and 107.98 %, respectively. In addition, as the pH of BHBSNs decreased, the free phenolic content and the content of released phenolics during digestion increased. Pearson correlations analysis showed that the increase in α-amylase inhibition and phenolic release during digestion induced by acidic pH was negatively correlated with the eGI and C∞ of BHBSNs. This study indicated that acidic pH condition could modulate starch digestion for preparing low GI BHBSNs.

Insights into the enhancement mechanism of immersion resistance of cooked noodles induced by wheat flour post-ripening: The view from protein cross-linking.

To overcome the problem that takeaway noodles possessed poor immersion resistance, in this study noodles were prepared from post-ripened wheat flour, and changes in textural properties, protein components, and water status of noodles were determined. The firmness and tensile distance of noodles were gradually increased by 7.40%-35.88% when wheat flour was post-ripened for 20-40 d. Afterwards, noodle textural qualities were slightly decreased. Compared with control groups, contents of glutenin macropolymer (GMP) and disulfide bonds were significantly (p<0.05) increased and protein network was also more compact, whereas the Glutenin/Gliadin ratio and free sulfhydryl groups content were significantly (p<0.05) reduced. Contents of sodium dodecyl sulfate extractable protein (SDSEP) were reduced by 3.22%-6.23%. Meanwhile, the decrease in A23 indicated that wheat flour post-ripening limited water-absorbing capacity of noodles during immersion. In conclusion, wheat flour post-ripening promoted the immersion resistance of noodles by inducing protein cross-linking, and the best post-ripening time was 20-40 d.

Structural changes and components' interactions alter the digestion property of in-kernel starch from thermally processed Tibetan Qingke.

Thermal processing has been applied to the property modification of the pure Tibetan Qingke (TQ) starch, but few studies attempt to elucidate the changes in physicochemical properties of in-kernel starches under whole TQ kernels thermal processing. In this study, the molecular, structural, and digestive characteristics of SUTQ, SHTQ, SMTQ, and SBTQ (starches isolated from unprocessed, heat fluidized, microwave irradiated, and baked TQ, respectively) were measured to elucidate the effects of different thermal treatments on the in-kernel starch. After TQ thermal treatments, the amylose/amylopectin ratio increased to 0.71, 0.64, and 0.68 for SHTQ, SMTQ, and SBTQ, respectively, while the molecular weight of in-kernel starches decreased by 39.29 %-82.14 %. Furthermore, the damage degree of starch surface morphology ranked as: SHTQ > SBTQ > SMTQ. The entanglement action between protein network resulting from protein polymerization and gelatinized starch aggregations exhibited most obvious in SHTQ. Moreover, the increased fluorescence intensity, newly formed dark color rings, and disrupted Maltese cross were observed in SHTQ, SMTQ, and SBTQ, and their variation trends were consistent with the damage degree of starch surface morphology. SHTQ, SMTQ, and SBTQ showed the decreased relative crystallinity (1.79 %, 15.98 %, and 14.64 %), short-range order (0.64, 0.81, and 0.80), and double helix structures (0.48, 0.61, and 0.58) and increased degree of gelatinization (100 %, 38 %, and 45.51 %), which partially transformed slowly digested starch into rapidly digested starch. In particularly, the formation of more ordered structures (V-type crystalline and interaction between protein and starch) induced by heat fluidization treatment provided the greatest thermal stability and highest resistant starch content (42.1 %) for SHTQ. Heat fluidization was a promising thermal processing for the development of TQ or TQ starch-based functional foods.

Effect of Thermal Treatment on the Physicochemical, Ultrastructural, and Antioxidant Characteristics of Euryale ferox Seeds and Flour.

Euryale ferox seeds (EFS) were less gelatinized, preventing the release of nutrients and functional compounds, resulting in limited applications in meals and the food industry. Nutraceutical importance of EFS includes starch, protein, lipids, 20 amino acids, minerals, and vitamins (C, E, and beta carotene). This study aimed to evaluate the effect of three different thermal treatments on EFS's physicochemical and nutritional properties and expected to improve its applicability. The results showed that the bulk density, thousand-grain weight, and hardness of thermal treated EFS were significantly decreased (p < 0.05), whereas the maximum decrease was observed in the industrial infrared heating-assisted fluidized bed (IHFH) treatment. Meanwhile, there were more crevices, fissures, and heightened porous structures in EFS between the pericarp and episperm and the endosperm after heat treatment, which facilitated grinding and water absorption. Notably, EFS's water and oil absorption capacities increased significantly (p < 0.05) with microwave and IHFH treatments. EFS ground's solubility into powder was increased significantly with thermal treatment (p < 0.05). Furthermore, the functional properties of TPC, TFC, DPPH radical scavenging activity, and reducing power were significantly increased (p < 0.05). In general, the changes in the physicochemical properties of EFS and increased bioactivity were caused by microwave and IHFH treatments. Hence, it might improve the food value of EFS while providing valuable information to researchers and food manufacturers.

Impact of thermally induced wall breakage on the structural properties of water-soluble polysaccharides in chickpeas.

The present work aimed to elucidate the influence of wall breakage induced by thermal processing on the molecular, structural, and antioxidant activities of water-soluble polysaccharides in chickpeas. Different extents of cell wall disruption were observed by fluorescence microscopy in chickpea cotyledons. Moreover, a decreasing fluorescence intensity of cell wall fragments was observed in the flour residues upon heat fluidization, autoclaving, and microwave heating, and the polysaccharide extraction rates were increased by 31.47%, 25.52%, and 9.79%, respectively. Furthermore, WPUCP, WPHCP, WPMCP, and WPACP (water-soluble polysaccharides from unprocessed, heat fluidized, microwaved, and autoclaved chickpeas, respectively) were RG-I (rhamnogalacturonan-I)-enriched pectic polysaccharides composed of galactose, arabinose, galacturonic acid, and rhamnose. After chickpea thermal processing, the degrees of branching decreased to 2.87, 3.79, and 2.53 in WPHCP, WPMCP, and WPACP, respectively, and the molecular weights were reduced by 46.46%, 24.83%, and 59.91%, respectively. Structural analysis showed that the semicrystalline regions of WPHCP, WPMCP, and WPACP were slightly damaged without changing the functional groups, but their thermal stability decreased. Interestingly, WPACP formed an ordered conformation (microporous network structure) through the formation of hydrogen bonds. Moreover, the antioxidant activities of WPHCP, WPMCP, and WPACP were enhanced, and the strongest radical scavenging activity was observed for WPHCP.

Effect of thermal processing on the molecular, structural, and antioxidant characteristics of highland barley ß-glucan.

This present work evaluated the effect of heat fluidization, microwave roasting and baking treatment of highland barley (HB) on the molecular, structural, thermal and antioxidant characteristics of ß-glucan. Fluorescence microscopy results showed that heat fluidization exhibited the greatest disruption effect on endosperm cell walls, resulting in the highest extractability (3.35 ± 0.06 g/100 g flour) and purity (92.67 ± 0.73%) of ß-glucan. After HB thermal processing, the molecular weight and polydispersity index of ß-glucan were respectively reduced by 3.68%-90.35% and 26.45%-39.83%, and its microscopic molecular morphology transformed from large sphere aggregate to alveolate gel network structure. Meanwhile, the structural elucidation by X-ray diffraction and infrared spectroscopy revealed that thermal processing induced the scission of polymeric chain and formation of lattice-type microgels without changing the primary functional groups of ß-glucan. Furthermore, thermogravimetry and antioxidant results indicated the thermal stability and antioxidant activity of ß-glucan were enhanced by thermal processing.

Effects of vacuum ultrasonic treatment on the texture of vegetarian meatloaves made from textured wheat protein.

To improve the quality of vegetarian meatloaves (VMs) made from textured wheat protein, the effects of different treatments (Vacuum, ultrasound and vacuum ultrasound) were compared in terms of texture, moisture distribution, microstructure and chemical bonding interactions. After vacuum, ultrasonic, and vacuum ultrasonic treatments, the hardness of VMs increased by 78%, 66%, 176% respectively. Scanning electron microscopy (SEM) showed that surface of VMs was smoother and the structure was tighter after vacuum ultrasonic treatment. In addition, magnetic resonance imaging (MRI) analysis showed that the moisture in VMs was evenly distributed after vacuum ultrasonic treatment. According to the optical maps observed by spectrofluorimetry and Fourier transform infrared spectroscopy (FT-IR), the fluorescence value and relative content of ß-sheet increased after vacuum ultrasonic treatment. Furthermore, the protein was cross-linked and hydrophobic interactions increased after vacuum ultrasonic treatment. Results showed that texture of VMs after vacuum ultrasonic treatment was closer to that of beef patties.

Effect of thermal treatment on the physicochemical, ultrastructural and nutritional characteristics of whole grain highland barley.

Highland barley (HB) was subjected to three thermal treatments (heat fluidization, microwave, and baking) and assessed for physicochemical, ultrastructural and nutritional properties. After thermal treatments, the hardness, bulk density, thousand kernel weight, length/breadth ratio, and color difference decreased significantly, while puffing index increased. Meanwhile, the formation of fissure was observed in the appearance. Microstructure images illustrated that numerous micropores were evenly distributed in the endosperm structure, and aleurone layer cells were deformed by compression. Furthermore, a dramatically disruption of endosperm cell walls and slightly deformation of outer layers were observed by confocal laser scanning microscopy. Moreover, a notably decrease in total phenolics (14.02%-36.91%), total flavonoids (25.28%-44.94%), and bound phenolics (8.99%-27.53%) was detected, while free phenolics (8.81%-43.40%), ß-glucan extractability (4.71%-43.66%), antioxidant activity (71.87%-349.77%), and reducing power (3.05%-56.13%) increased significantly. Greatest increase in nutritional values was caused by heat fluidization, which possessed the potential for development of ready-to-eat functional foods.

Impact of aqueous ozone mixing on microbiological, quality and physicochemical characteristics of semi-dried buckwheat noodles.

The microbiological, microstructural, and physicochemical impact of aqueous ozone mixing (AOM) on semi-dried buckwheat noodles (SBWN) was elucidated in this study. Microbiological measurements declared that AOM reduced the initial total plate count (TPC) of SBWN significantly (P < 0.05) with a prolonged shelf-life of 2 ~ 5 days. Meanwhile, AOM reduced the cooking loss and water absorption along with the enhancement of hardness and tension force. Scanning electron microscopy (SEM) showed that the protein network of surface and cross section became continuous and compact, and wrapped starch granules more effectively. Moreover, an obvious increase in the intensity of the high molecular protein bands was observed in the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns. Furthermore, the sodium dodecyl sulfate extractable protein (SDSEP) under non-reducing condition obviously decreased, and then the SDSEP under reducing condition changed insignificantly (P > 0.05). These results indicated that AOM mainly promoted the protein cross-linking of SBWN by disulfide bond (SS) cross-links.

Shelf-life extension of semi-dried buckwheat noodles by the combination of aqueous ozone treatment and modified atmosphere packaging.

The present study investigated the combined effects of aqueous ozone treatment and modified atmosphere packaging (MAP) on prolonging the shelf-life of semi-dried buckwheat noodles [SBWN; moisture content (22.5±0.5%)] at 25°C. Firstly, the different concentrations of ozonated water were used to make SBWN. Subsequently, SBWN prepared with ozonated water were packaged under six different conditions and stored for 11days. Changes in microbial, chemical-physical, textural properties and sensorial qualities of SWBN were monitored during storage. Microbiological results indicated that adopting 2.21mg/L of ozonated water resulted in a 1.8 log10 CFU/g reduction of the initial microbial loads in SBWN. In addition, MAP suppressed the microbial growth with a concomitant reduction in the rates of acidification and quality deteriorations of SBWN. Finally, the shelf-life of sample packed under N2:CO2=30:70 was extended to 9days, meanwhile textural and sensorial characteristics were maintained during the whole storage period.