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Abstract: Wheat filter flours are by-products obtained from air-classification of wheat flour. Physicochemical and rheological properties of wheat filter flours were investigated in the present study. Average values of crude protein, gluten, lipid and damaged starch content of filter flours were higher than those of standard flours for the same batch. The positive correlation of particles with size <20 μm and damaged starch was found. Moreover, the filter flours had higher water absorption, stability time except head milling filter flour samples. Short peak time and low peak viscosity were also observed. Different composition of wheat filter flours may be an important factor influencing its properties. This study is very useful for exploring the utilization of wheat filter flours in the food industry. [Copyright &y& Elsevier]

Abstract: Four fractions (100-, 50-, 20-K and permeate) from a proteolytic hydrolysate (DH=2.8%) of wheat gluten were separated using size fractionation on ultrafiltration membranes with molecular weight cut-offs of 100, 50 and 20kDa and their functional properties evaluated. Proteolysis led to a significant (P<0.05) increase in solubility of gluten fractions at pHs between 2–10 and a shift of the pI value from 6–7 to 5. The solubilities of 100-K, 50-K, 20-K and permeate fractions were significantly (P<0.05) improved compared with the untreated control and the hydrolysate. The 50-K fraction was superior to other three fractions for emulsion activity index between pH 2 and 10. The most stable foam was given by the 100-K fraction which showed 65.8% of initial foam while the control sample gave only 23% of foam, after 60min resting. Foam stability decreased as the molecular mass of hydrolysate fractions decreased. Furthermore, after proteolysis, the surface hydrophobicity (H 0) of gluten increased significantly (P<0.05) compared with the control except for the permeate fraction. The highest value of H 0 was given by the 100-K fraction, followed by the 50-K, 20-K and permeate fractions. In addition, proteolysis resulted in a decrease in the storage modulus of gels. [Copyright &y& Elsevier]

Heat-denatured wheat gluten (HDWG) degradation during freeze-thaw (FT) cycling is a key factor in the quality deterioration of pre-cooked noodles (PCNs). This study investigated the effects and underlying mechanisms of sodium chloride (NaCl) on HDWG. Adding NaCl enhanced the luminance of PCNs and reduced chromatic aberration. Scanning electron microscopy revealed that NaCl facilitated a more continuous microstructure, resulting in a reduction the average hole size of HDWG from 84.44 μm to 56.59 μm after 10 FT cycles. With the FT cycling, gluten macropolymer (GMP) depolymerization occurs, causing the collapse of HDWG network structure. However, NaCl contributed to the formation of β-sheet and gauche-gauche-gauche (g-g-g) conformations, resulting in a stronger three-dimensional structure of HDWG, thus alleviating GMP depolymerization. The analysis of intermolecular interactions shows that NaCl primarily affects hydrogen bonds, disulfide bonds, and hydrophobic interactions, and stabilizes the structural integrity of HDWG by balancing these forces. NaCl altered the three-dimensional structural composition of HDWG by influencing the intermolecular interactions, thereby fortifying the PCNs against FT cycling. This study provides a robust theoretical basis for using NaCl to regulate the quality of thermally precooked flour products. [Display omitted] • NaCl slows the depolymerization of heat-denatured wheat gluten during freeze-thaw cycles. • NaCl facilitates the formation of a continuous heat-denatured wheat gluten network. • NaCl enhances the β-sheet and g-g-g conformations in heat-denatured gluten. • NaCl raises the content of hydrogen bonds and S−S bonds in heat-denatured gluten. [ABSTRACT FROM AUTHOR]

Abstract: The phenolic contents of methanolic extracts of emblica (Phyllanthus emblica L.) fruit from six regions in China were measured in this work. The antioxidant activities of these extracts were also evaluated. Total phenolic content was ranged from 81.5 to 120.9mggallic acid equivalents (GAE)/g and the flavonoid content was varied from 20.3 to 38.7mgquecetin equivalents (QE)/g, while proanthocyanidin content was ranged from 3.7 to 18.7mgcatechin equivalents (CE)/g. Among all the methanolic extracts analyzed, the Huizhou sample exhibited a significantly higher phenolic content than other samples (P<0.05). The antioxidant activities were evaluated by in vitro experiments using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, hydroxyl radicals, and superoxide anion radicals, chelating ability of ferrous ion, reducing power, and inhibition capability of Fe (II)-induced lipid peroxidation, respectively. The Huizhou sample was found to have the strongest antioxidant activities in scavenging DPPH radicals, superoxide anion radicals, and had the highest reducing power, while the Chuxiong sample showed the best performance in chelating iron and inhibiting lipid peroxidation. Furthermore, the Chuxiong sample exhibited a stronger inhibition activity of the hydroxyl radicals compared with other samples. The high correlation coefficient was existed between the phenolic content and superoxide anion radical scavenging activity, but no significant correlation was found between the former and hydroxyl radical scavenging activity. Methanolic extracts of emblica fruit from some selected regions exhibited stronger antioxidant activities compared to those of the commercial compounds (quercetin and BHA). It might be considered as a potential plant source of antioxidants. [Copyright &y& Elsevier]

Sweet potato flour (SPF), as a functional substitute for wheat flour (WF), has gained popularity among consumers in the development of nutritious food products. However, the mechanism of SPF on gluten in dough remains unclear. Effects of SPF on the pasting characteristics, gluten aggregation properties, and the quality of dough were investigated. The results showed that SPF-WF exhibited low pasting properties, and pasting temperature increased by 22.35%–26.98%. SPF-WFs were lower in peak viscosity (62.57%–88.17%), trough viscosity (80.32%–96.67%), breakdown viscosity (11.58%–66.37%), final viscosity (70.72%–96.95%), setback viscosity (57.83%–97.33%), and peak time (16.26%–29.30%). Compared with WF dough, SPF-WF dough had higher hardness and lower elasticity. Microstructure images showed that SPF changed the pore size of the gluten network and caused starch to accumulate. SPF could accelerate gluten aggregation, decrease gluten network strength, and reduce aggregation energy, possibly due to the increase of disulfide bonds from 1.12% to 12.52% (P < 0.05). Moreover, SPF mediated medium molecular weight gluten as well as monomer gluten were polymerized into large molecular weights. In summary, SPF might mediate gluten aggregation and 10% substitution of SPF showed a significant level compared to others. • Enhanced nutrient content and bioactive potential by adding SPF. • Polyphenols in SPF induce disulfide bond formation. • SPF can be cross-linked into the gluten network structure. • The 10% substitution of SPF was determined to be the optimal substitution amount. [ABSTRACT FROM AUTHOR]

The bacterial communities of 4 dough fermentation starter samples, including Jiaozi A and D and sourdough B4 and B5 selected from Henan, Jiangsu, and Liaoning province of China were compared by high-throughput sequencing of 16S rRNA genes. The highest number of operational taxonomic units (OTUs) was found for the genus Acetobacter in Jiaozi A, but only OTUs adapted to dough conditions after 8 h (A8) and 24 h (A24) of fermentation using Jiaozi A as dough starter. Members belonging to the genus Pediococcus appeared to dominate in Jiaozi D, especially in the dough (D24) fermented for 24 h started by Jiaozi D. The genus Lactobacillus dominated in sourdough B5, A8, and A24. Weissella was the predominant genus in sourdough B4, and members of the genera Leuconostoc and Lactococcus were also identified. [ABSTRACT FROM AUTHOR]

Trehalose is widely used in the food and cosmetics industry owing to its unique stabilizing properties. In this study, we aimed to further understand the effect of trehalose on the aggregation and structural properties of gluten. We investigated changes in the aggregation and textural properties, molecular weight distribution, disulfide bond contents, secondary structure, and network structure for weak-, middle-, and strong-gluten when supplemented with trehalose. The results showed that the macromolecular aggregation of gluten proteins was impaired. The hardness, gumminess, and chewiness of dough reduced, whereas adhesiveness increased significantly. Moreover, a looser gluten network structure was obtained with increase in trehalose content. High levels of trehalose (<5%) caused a decrease in the disulfide bond content. Secondary structure analysis of gluten indicated that the α-helix content increased for weak-gluten. In strong-gluten wheat, the β-sheet content was converted to random coil. This suggests that trehalose affected the hydration level of gluten. Trehalose likely competes with gluten for the available water by disrupting the hydrogen bonds between gluten and water molecules and breaking the "loop and train" model of gluten. Thus, the decreased disulfide bond content and increased α-helix and random coil contents induced by trehalose inhibited gluten aggregation and interrupted the gluten network. The study findings improve our understanding of trehalose functionality in dough of different gluten strength. Furthermore, these data provide valuable insights into the application of trehalose in wheat flour food products. [Display omitted] • Macromolecular aggregation of gluten proteins was impaired by trehalose. • Trehalose enhanced the adhesiveness of dough for different gluten strength flour. • High levels of trehalose (exceed 5%) adding caused a decrease of S–S content of gluten. • α-helix and random coil contents of gluten increased as trehalose treated. • A discontinuous gluten network was obtained induced by trehalose. [ABSTRACT FROM AUTHOR]

The aim of this study was to clarify the influence of curdlan on the quality of frozen cooked noodles (FCN) by exploring the changes in textural properties, color profile, thermal stability, and micromorphology of FCN during cooking. Herein, an improvement in hardness, springiness, and tensile fracture distance was observed after adding 0.5% of curdlan, from 2876.82 ± 14.59 to 3371.08 ± 64.75 g, 0.85 ± 0.01 to 0.91 ± 0.02, and 90.60 ± 0.79 to 94.29 ± 1.37 mm, respectively. Combined with the decrease in weight loss and total color difference, from 9.01 ± 0.25 to 7.03 ± 0.07 and 76.00 ± 0.16 to 75.71 ± 0.24%, respectively, it can be inferred that the improved quality of FCN was mainly attributed to the stable gluten network mediated by curdlan. Moreover, results of micromorphology demonstrated that FCN with 0.5% curdlan had higher protein percentage area (35.20 ± 0.32%), junction density (5.97 ± 0.09 × 10−4), total protein length (35733.97 ± 456.84 μm), and degree of protein aggregation than those of FCN without curdlan, confirming that curdlan helped in maintaining the stability of gluten network and inhibited the depolymerization of gluten proteins induced by excessive cooking. [Display omitted] • Curdlan improved the quality of frozen cooked noodles (FCN) during cooking. • Curdlan enhanced the uniformity and thermal stability of FCN during cooking. • Curdlan strengthened the structure of the gluten network during cooking. • Curdlan inhibited the disaggregation of gluten network by hydrothermal treatment. [ABSTRACT FROM AUTHOR]

In order to understand the underlying mechanisms of curdlan on texture properties of frozen cooked noodles (FCN), this study investigated the effects of curdlan on the physicochemical and structural properties of gluten during cooking. The results showed the textural properties were obviously enhanced with 0.5% curdlan added, meanwhile, the compact and homogeneous gluten network was formed by the presence of curdlan. RP-HPLC and FTIR patterns demonstrated that curdlan delayed the increment of protein aggregation and the conformational change during heating. SDS-PAGE and chemical interaction suggested that hydrophobic interactions and steric-hindrance, rather than covalent crosslinking, were the main ways curdlan acted on gluten aggregation. While the homogeneity of the gluten network and quality of FCN were destroyed by undue gluten aggregation during heating, the addition of curdlan mitigated the extent of this undesirable change. This study provides a more comprehensive theoretical basis for FCN quality control. [Display omitted] • Curdlan improves texture properties of frozen cooked noodles (FCN) during cooking. • Curdlan enhances the formation of homogeneous gluten network of FCN during cooking. • Curdlan delays the increment of protein aggregation in FCN during cooking. • Curdlan increases the gluten tolerance to heating by hydrophobic interactions. • Extra aggregation of gluten is not conducive to the quality of FCN. [ABSTRACT FROM AUTHOR]

Abstract: Postharvest browning of longan fruit results in a short life and a reduced commercial value. The experiments were conducted to separate, then purify and finally identify the polyphenol oxidase (PPO) substrates that cause longan fruit to brown. PPO and its substrates were, respectively, extracted from longan fruit pericarp tissues. The substrate for longan PPO was separated and purified using polyamide column chromatography, Sephadex LH-20 column chromatography and silica gel column chromatography, respectively. The substrate was further identified by 0.5% FeCl3 solution and enzymatic reaction with longan PPO. On the bases of UV, 1H NMR, 13C NMR, and ESI-MS data, the direct substrate for the PPO from pericarp tissues of longan fruit was identified to be (−)-epicatechin. Furthermore, the contents of (−)-epicatechin of pericarp tissues of longan fruit of two major cultivars were determined by high performance liquid chromatography (HPLC). The HPLC analysis exhibited that the contents of (−)-epicatechin of fruit pericarp of ‘Shixia’ and ‘Chuliang’ were 0.26 and 0.56mg/g on fresh weight (FW) basis at harvest and 0.15 and 0.09mg/g FW after 3 days of storage. The more rapid decrease in the (−)-epicatechin content of ‘Chuliang’ was due to the oxidization catalyzed by PPO, which was in agreement with the higher browning index. [Copyright &y& Elsevier]

Reducing sodium in cereal products has become a health trend, and low-sodium salt is considered as a promising sodium substitute; however, its technical roles in dough formation have not been well understood. Effects of low-sodium salt on the physicochemical and rheological properties of dough were investigated in the present study compared with that with NaCl and KCl. Addition of low-sodium salt significantly increased stability, development time and extensional area of dough, and reduced water absorption. Wheat gluten extractability and free SH content gradually decreased with low-sodium salt additions increased, indicating that salt affected gluten macromolecular aggregation. Zeta potential measurements indicated that salt promoted the interactions between gluten molecules. Overall, low-sodium salt effectively changed physicochemical and rheological properties of dough in a manner very similar to NaCl and KCl. Therefore, addition of low-sodium salt may be a feasible approach to alleviate high sodium in the process of dough formation. [Display omitted] • Addition of low-sodium salt increase gluten strength and extensional area. • Addition of low-sodium salt decreased free SH group content. • Low-sodium salt may induce the aggregation of gluten in dough. • Low-sodium salt increases salt-gluten interaction, to some extent. [ABSTRACT FROM AUTHOR]

Abstract: The sarcoplasmic protein was extracted from the muscle of grass carp, a Chinese freshwater carp, and was hydrolyzed with five proteases to produce antioxidant peptides. Papain hydrolysate was found to have the greatest activity against lipid peroxidation. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions (including enzyme to substrate ratio, time and temperature). The minimum EC50 value (317.25μg/mL) which signified the maximum antioxidant activity was obtained at an enzyme to substrate ratio of 0.79%, an incubation time of 5.69h and an incubation temperature of 52.15°C, which was in agreement with the predicted value (313.99μg/mL) estimated by RSM within a 95% confidence interval. Also, it was found that moderate denaturation of the sarcoplasmic protein and a modest increase in the degree of hydrolysis promoted the antioxidant activities of the hydrolysates. Oligopeptides (< 3kDa) contributed more to the antioxidant activity than polypeptides. [Copyright &y& Elsevier]

Pectin is a common food additive used for enhancing the health benefits of dietary fibers, and is the most structurally and functionally complex polysaccharide, rich in galacturonic acid. In this study, we investigated changes in the aggregative property of gluten, their rheological properties, and secondary structure, as well as in the gluten network, when supplemented by apple pectin. Adding pectin was shown to enhance the macromolecular aggregation of gluten, and improved the rheological properties of dough by inducing a dense network of gluten. The presence of pectin decreased α-helix content but increased β-sheet and β-turn structure of gluten, suggesting that pectin affected the hydration level of gluten, leading to the formation of aggregated β-structures. This study provides a better understanding of pectin functionality in wheat flour dough, and is valuable for guiding in the application of pectin in wheat flour food products. [Display omitted] [ABSTRACT FROM AUTHOR]

Frozen-cooked noodles (FCN) and its components undergo quality changes during frozen storage, such as reduced textural and cooking qualities, weakened gluten network, and damaged starch properties; thus, storage condition is a critical factor affecting the final quality of FCN. In this study, in view of the thermoirreversible high-strength gel property (at ≥ 80 °C) of curdlan, strong hydrophilicity, and freeze-thawed stability of high-strength gel prepared from curdlan powder, the effect of curdlan on the quality of FCN during frozen storage was first evaluated. The results showed that curdlan was effective in reducing cooking loss, enhancing water absorption, and improving textural properties of FCN; the improving effect presented a trend of first increasing and then decreasing with the amount of increasing curdlan (0.1%–0.9%); and the addition of 0.5% curdlan was most effective in improving the quality of FCN. Thermal gravimetric analysis indicated that curdlan enhanced thermal stability of FCN, implying curdlan could strengthen the gluten network. Meanwhile, structural observations revealed that, during frozen storage, FCN with added curdlan exhibited a more continuous and compact gluten network accompanied with more uniform and smaller ice crystals. Thus, curdlan is desirable to be used as a novel gum in FCN to provide specific functionality and minimize the negative effect of frozen storage. This study provides new insights into the quality improvement of FCN and further expands the application potential of curdlan in food industry. Image 1 • Curdlan improved the quality of frozen-cooked noodles (FCN) during frozen storage. • Curdlan enhanced the thermal stability of FCN during frozen storage. • Curdlan prevented ice crystals from growth and recrystallization of FCN. • The addition of curdlan contributed to strengthening gluten network of FCN. [ABSTRACT FROM AUTHOR]