Texture and digestion of noodles with varied gluten contents and cooking time: The view from protein matrix and inner structure

Changes in overall digital structure, starch properties and moisture distribution reveal how the hardness of wheat noodles evolves under different cooking status

To elucidate the relationship between the structural evolution of starch within noodles during cooking and the hardness, the panoramic and local microstructure of cooked noodles were quantitatively analyzed, and the structure of starch in noodles were measured. We found that in the case of starch within cooked noodles with a high degree of swelling, the quantitative analysis of each ring was sufficient to represent the structural differences. Changes occurring in starch inside noodles during cooking were not homogeneous. The structural modifications of starch in the outer ring were greater than in the inner ring along with the extension of cooking time. The main reason responsible for the high hardness was attributed to low swelling degree and high short-range order of starch in the center. Water migration from the periphery to the center of the noodles, which was closely related to the fine structure of amylopectin, determined the state of central starch. Wheat starch with more large amylopectin molecules and more long amylopectin chains could enhance the inhibition of water migration and decrease the swelling degree of starch in the center, in order to endow a high hardness to noodles. These results will be useful for the ingredients selection for the production of noodles with desirable quality. In addition, the analysis method established in this work promoted the realization of quantitative comparison of the cooked noodles microstructure, that is an effective tool to clarify the structural basis of macroscopic quality of noodles.

Role of Food Texture, Oral Processing Responses, Bolus Properties, and Digestive Conditions on the Nutrient Bioaccessibility of Al Dente and Soft-Cooked Red Lentil Pasta

The purpose of this study was to assess the impact of food texture, oral processing, bolus characteristics, and in vitro digestive conditions on the starch and protein digestibility of al dente and soft-cooked commercial red lentil pasta. For that, samples were cooked as suggested by the provider and their texture properties were promptly analysed. Then, normal and deficient masticated pasta boluses were produced by four healthy subjects, characterised in terms of their oral processing, bolus granulometry, texture and viscoelastic properties, and finally subjected to static in vitro digestion, according to the INFOGEST consensus for both adults and the older adult population. Normal masticated boluses exhibited greater saliva impregnation and lower proportions of large particles, hardness, and stiffness than deficient masticated boluses. Likewise, insufficiently masticated al dente-cooked pasta boluses caused a delay in oral starch digestion owing to the larger particles attained during food oral processing, while reduced intestinal conditions in the elderly only interfere with the release of total soluble proteins in all samples. This work evidences the importance of considering the initial texture of products, oral capabilities, processing behaviour, and physical and mechanical properties of food boluses in digestion studies, opening new prospects in designing pulse-based foods that meet the nutritional requirements of the world's population.

Review of formation mechanisms and quality regulation of chewiness in staple foods: Rice, noodles, potatoes and bread

Staple foods serve as vital nutrient sources for the human body, and chewiness is an essential aspect of food texture. Age, specific preferences, and diminished eating functions have broadened the chewiness requirements for staple foods. Therefore, comprehending the formation mechanism of chewiness in staple foods and exploring approaches to modulate it becomes imperative. This article reviewed the formation mechanisms and quality control methods for chewiness in several of the most common staple foods (rice, noodles, potatoes and bread). It initially summarized the chewiness formation mechanisms under three distinct thermal processing methods: water medium, oil medium, and air medium processing. Subsequently, proposed some effective approaches for regulating chewiness based on mechanistic changes. Optimizing raw material composition, controlling processing conditions, and adopting innovative processing techniques can be utilized. Nonetheless, the precise adjustment of staple foods' chewiness remains a challenge due to their diversity and technical study limitations. Hence, further in-depth exploration of chewiness across different staple foods is warranted.

Effects of protein morphological structures on the cereal processing, sensorial property and starch digestion: a review

In cereals, the protein body and protein matrix are usually two morphological protein structures. However, processing treatments can affect protein structures, change protein bodies into the matrix, or induce a change in the matrix structure; therefore, the processing-induced matrix was listed as the third morphological structure of the protein. Previous research on the effect of proteins was mainly based on protein content and composition, but these studies arrived at different conclusions. Studying the effect of protein morphological structures on sensorial property and starch digestion can provide a theoretical basis for selecting cultivars with high sensorial property and help produce low-glycemic index foods for people with diabetes, controlling their postprandial blood sugar. This study aimed to review the distribution and structure of protein bodies, protein matrices, and processing-induced matrices, as well as their influence on cereal sensorial property and starch digestion. Therefore, we determined the protein morphological structures in different cereal cultivars and summarized its impact. Protein bodies mainly have steric stabilization effects on starch gelatinization, whereas the protein matrix serves as a physical barrier surrounding the starch to inhibit water absorption and α-amylase. Processing can change protein morphological structures, enabling protein bodies to act as a physical matrix barrier.

Explaining the improving effect of dough crumb-sheet composite rolling on fresh noodle quality: From microstructure and moisture distribution perspective

A new technique known as dough crumb-sheet composite rolling (DC-SCR) was used to improve the quality of fresh noodles. However, there is a dearth of theoretical investigations into the optimal selection of specific parameters for this technology, and the underlying mechanisms are not fully understood. Therefore, the effects of dough crumb addition times in DC-SCR on the texture, cooking, and eating quality of fresh noodles were first studied. Then, the underlying regulation mechanism of DC-SCR technology on fresh noodles was analyzed in terms of moisture distribution and microstructure. The study demonstrated that the most significant enhancement in the quality of fresh noodles was achieved by adding dough crumbs six times. Compared with fresh noodles made without the addition of dough crumbs, the initial hardness and chewiness of fresh noodles made by adding six times of dough crumbs increased by 25.32% and 46.82%, respectively. In contrast, the cooking time and cooking loss were reduced by 28.45% and 29.69%, respectively. This quality improvement in fresh noodles made by DC-SCR came from the microstructural differences of the gluten network between the inner and outer layers of the dough sheet. A dense structure on the outside and a loose structure on the inside could endow the fresh noodles made by DC-SCR with higher hardness, a shortened cooking time, and less cooking loss. This study would provide a theoretical and experimental basis for creating high-quality fresh noodles.

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.

Impact of pre-meal immersion on multi-scale structural changes and starch digestibility of cooked dried noodles

Pre-meal immersion is a common process for both the consumption of dried noodles and development of takeaway noodles, but its impact on the structure and digestibility of dried noodles is still unclear. In this study, dried noodles cooked for the optimal time were immersed at 80 °C for different time durations. Multi-scale structural changes, including texture, molecular structure, microstructure, and in vitro starch digestibility were studied using a combination of kinetic (first-order exponential decay function, the Peleg model, and LOS plots), physicochemical, and microscopic analysis. The relationship between multi-scale structural changes and starch digestibility was derived. As the immersion progressed, the hardness first rapidly decayed and then reached equilibrium. The decay rate in the initial stage depended on the gluten content. In most cases, the immersion process caused depolymerization of gluten proteins and further gelatinization of starch granules, which was observed from an increase in the free -SH content and decrease in the short-range ordered structure, although there were fluctuations over immersion time. Structural changes resulted in the corresponding changes in substance migration. However, a high gluten content (∼15% w/w) imparted a denser microstructure to the noodles, weakening the deterioration effects compared with a low gluten content (∼10% w/w). In vitro digestion experiments proved that samples with higher gluten content had higher starch digestion rates and lower starch digestion extent during immersion. Correlation analysis revealed that there was a negative correlation between k1 and the tightness of the gel. This study helps to reveal the structural mechanisms of starch digestibility in cooked noodles during immersion.

Low glycemic index noodle and pasta: Cereal type, ingredient, and processing

The consumption of noodles with a high glycemic index (GI) can affect health, prompting the need for dietary adjustments to manage abnormal blood glucose levels. This review delves into recent progress in low GI noodles and their potential effect for human well-being. Diverse approaches, encompassing the incorporation of soluble dietary fiber, modified starches, proteins, and plant polyphenols, have shown encouraging outcomes in diminishing the GI of noodles. Furthermore, variations in processing, storage, and cooking techniques can influence the GI of noodles, yielding both positive and negative impacts on their glycemic response. Soluble dietary fiber, protein cross-linkers, and plant polyphenols play a pivotal role in reducing the GI of noodles by hindering the interaction between digestive enzymes and starch, thereby curbing enzymatic activity. Future research spotlighting ingredients, processing methodologies, and the underlying mechanisms of low GI noodles will contribute substantively to the development of functional foods boosting enhanced nutritional profiles.

Enhancing Nutritional Profile of Pasta: The Impact of Sprouted Pseudocereals and Cushuro on Digestibility and Health Potential

We hypothesized that optimizing the formulation of pasta by incorporating sprouted pseudocereal flours, specifically quinoa (Chenopodium quinoa Willd) or kiwicha (Amaranthus caudatus L.) and cushuro (Nostoc sphaericum Vaucher ex Bornet & Flahault) flours, could offer the potential to simultaneously enhance nutritional quality and health-promoting properties in pasta. In this study, our objective was to optimize the formulation of composite flour (a ternary blend of wheat, sprouted pseudocereal, and cushuro flours) using a mixture composite design to maximize total soluble phenolic compounds (TSPC), γ-aminobutyric acid (GABA), antioxidant activity, and mineral bioaccesilability by reducing phytic acid (PA) content. Two optimal formulations were identified: one consisting of 79% wheat flour (WF), 13% SQF, and 8% CuF (oPQC), and the other composed of 70% WF, 15% SKF, and 15% CuF (oPKC). These optimized pastas exhibited reduced starch content and notably higher levels of total dietary fiber (1.5-3.61-fold), protein (1.16-fold), fat (1.3-1.5-fold), ash (2.2-2.7-fold), minerals (K, Na, Fe, Zn, Mg, Mn, and Ca), PA (3-4.5-fold), TSPC (1.3-1.9-fold), GABA (1.2-2.6-fold), and ORAC (6.5-8.7-fold) compared to control pasta (100% WF). Notably, the glycemic index of oPQC (59.8) was lower than that of oPKC (54.7) and control pasta (63.1). The nutritional profile of the optimized pasta was largely retained after cooking, although some significant losses were observed for soluble dietary fiber (18.2-44.0%), K (47.5-50.7%), Na (42.5-63.6), GABA (41.68-51.4%), TSPC (8-18%), and antioxidant activity (45.4-46.4%). In vitro digestion of cooked oPQC and oPKC demonstrated higher bioaccessible content of GABA (6.7-16.26 mg/100 g), TSPC (257.7-261.8 mg GAE/100 g), Ca (58.40-93.5 mg/100 g), and Fe (7.35-7.52 mg/100 g), as well as antioxidant activity (164.9-171.1 µmol TE/g) in intestinal digestates compared to control pasta. These findings suggest that the incorporation of sprouted pseudocereals and cushuro flour offers a promising approach to enhance the nutritional quality and bioactive content of wheat-based pasta, potentially providing health benefits beyond traditional formulations.

A review of starch swelling behavior: Its mechanism, determination methods, influencing factors, and influence on food quality

Swelling behavior involves the process of starch granules absorbing enough water to swell and increase the viscosity of starch suspension under hydrothermal conditions, making it one of the important aspects in starch research. The changes that starch granules undergo during the swelling process are important factors in predicting their functional properties in food processing. However, the factors that affect starch swelling and how swelling, in turn, affects the texture and digestion characteristics of starch-based foods have not been systematically summarized. Compared to its long chains, the short chains of amylose easily interact with amylopectin chains to inhibit starch swelling. Generally, reducing the swelling of starch could increase the strength of the gel while limiting the accessibility of digestive enzymes to starch chains, resulting in a reduction in starch digestibility. This article aims to conduct a comprehensive review of the mechanism of starch swelling, its influencing factors, and the relationship between swelling and the pasting, gelling, and digestion characteristics of starch. The role of starch swelling in the edible quality and nutritional characteristics of starch-based foods is also discussed, and future research directions for starch swelling are proposed.

Tomographical, rheological, and structural effects of soy protein concentrate in a gluten-free extruded noodle system

Global interest in high-protein foods has been rapidly increasing and the gluten-free products are no exceptions. Gluten-free extruded noodles made from rice flour were thus fortified with soy protein concentrate (SPC) (0%, 15%, 30%, and 45% by weight), and the physicochemical properties of the noodles were characterized in terms of tomographical, rheological, and structural features. SPC-rice flour blends showed higher water absorption and swelling power at room temperature with increasing levels of SPC, which were reduced upon heating. The flour blends with high-levels of SPC also had lower pasting viscosities. Thermal analysis showed lower enthalpy values and higher temperatures derived from starch gelatinization. When the SPC-rice flour blends were applied to extruded gluten-free rice noodles, the noodles tomographically showed a dense and compact structure, that could be favorably correlated with their textural changes (increased hardness and reduced extensibility). FTIR analysis presented the structural changes of the noodles containing different levels of SPC by showing higher intensity of protein-related absorption peaks and lower starch peak intensity, which could be associated with the reduced cooking loss. Moreover, there existed two water components with different mobilities in the noodles whose spin-spin relaxation times had a tendency to increase with increasing SPC content. The results obtained from this study provided fundamental insights into the processing performance of protein-rich ingredients in gluten-free extruded noodles, probably promoting the development of a wider variety of protein-fortified gluten-free products.

Degradation of starch in pasta induced by extrusion below gelatinization temperature

The structural deformation of starch during pasta extrusion leads to varied effects on pasta quality. We investigated the impact of shearing force on the starch structure of pasta and pasta quality by varying the screw speed (100, 300, 500 and 600 rpm) with a temperature range of 25 to 50 ℃ in increments of 5 ℃, from the feeding zone to the die zone. The higher screw speeds were associated with more specific mechanical energy input (157, 319, 440, and 531 kJ/kg for pasta produced at 100, 300, 500 and 600 rpm, respectively), resulting in a lower pasting viscosity (1084, 813, 522 and 480 mPa·s for pasta produced at 100, 300, 500 and 600 rpm, respectively) in the pasta due to the loss of starch molecular order and crystallinity. Size-exclusion chromatography revealed that pasta produced at 600 rpm screw speed had a lower amylopectin size distribution which indicated molecular breakdown during extrusion. Pasta produced at 600 rpm had higher in vitro starch hydrolysis (both raw and cooked) than the pasta made at 100 rpm. The research provides relationship of how the screw speed can be manipulated to design pasta with varied texture and nutritional functionality.

Effect of adding wheat (Triticum aestivum L.) farina with varied integrity of endosperm cell wall on dough characteristics, dried noodles quality and starch digestibility

The changes of intact endosperm cell wall in cereal food processing and its effect on starch digestibility are important for developing nutritious and healthy next generation foods, but their changes in the process of traditional Chinese cooking products such as noodles making have not been investigated. In this paper, the changes in endosperm cell wall in the process of making dried noodles by adding 60 % wheat farina with varied particle sizes were tracked, and the underlying mechanisms affecting the noodle quality and starch digestibility were revealed. With increasing particle size (150-800 μm) of farina, the contents of starch and protein, swelling index of glutenin, and sedimentation value decreased significantly and the dietary fiber increased sharply; moreover, water absorption, stability and extensibility of dough decline obviously while the resistance to extension and thermal stability were enhanced. In addition, noodles made with flour added larger-particle size farina had a lower hardness, springiness, and stretchability while a higher adhesiveness. Compared to the flour and other samples, the flour with the smaller-particle size farina (150-355 μm) showed better rheological properties of dough and cooking quality of noodles. Furthermore, the integrity of the endosperm cell wall increased with increasing particle size (150-800 μm), which was perfectly preserved during noodle processing and was an effective physical barrier to inhibit starch digestion. The starch digestibility of noodles made from mixed farina with low protein content (~15 %) did not significantly reduce compared to that of wheat flour noodles with high protein content (~18 %), probably due to the increased cell wall permeability of noodle processing, or the overwhelming effect of noodle structure or protein content. In conclusion, our findings will contribute to an innovative perspective for in-depth understanding of the impact of endosperm cell wall on the quality and nutrition of noodles at the cellular level, which provided a theoretical basis for the moderate processing of wheat flour and the development of healthier wheat-based food products.

A New Approach for the Development and Optimization of Gluten-Free Noodles Using Flours from Byproducts of Cold-Pressed Okra and Pumpkin Seeds

The significant protein and dietary fiber content of cold-pressed pumpkin (PSF) and okra (OSF) seed byproducts are well-known. However, their impact on noodles' nutritional quality has never been studied. For the first time, noodle formulation was developed employing a genetic algorithm in the R programming language to achieve the most optimal sensory attributes as well as nutritional composition, color, cooking, and textural properties. The optimized noodle formulation was detected for OSF, PSF, gluten-free flour, salt, and egg with the following amounts: 11.5 g, 87.0 g, 0.9 g, 0.6 g, and 40 g, respectively, with 10.5 mL of water. The total protein (TP%), total fat (TF%), total carbohydrate (TC%), total dietary fiber content (TDF%), ash (%), total phenolic content (TPC mg GAE/100 g), and ABTS (%) of PSF were found to be 39%, 17%, 7%, 18%, 3%, 19%, and 48%, respectively, whereas for OSF, 33%, 8%, 21%, 32%, 5%, 16%, and 38%, respectively, were detected. In addition, TP (42.88%), TF (15.6%), ash (5.68%), TDF (40.48%), TPC (25.5 mg GAE/100 g), and ABTS (70%) values were obtained for the noodles. Consequently, the valorization of the cold oil press industry's byproducts may be used as ingredients that add high value to gluten-free protein and fiber-rich noodle production, and they may gain interest from both processors and consumers.

Precooking treatments affect the sensory and tensile properties of autoclaved recooked noodles via moisture distribution and protein structure

To improve the quality of autoclaved recooked noodles (ARNs), this study explored the effects of precooking on the sensory and tensile properties of ARNs from the perspectives of changes in protein structure and water distribution. The results showed that the ARNs of two kinds of pretreatments (Boiling 2 min, Boiling 1 min + Steaming 2 min) presented the best sensory quality (average score ≥ 7.50) and high tensile properties (tensile distance ≥ 45.24 mm). After autoclaving and recooking, the proportion of tightly bound water increased by 11.30%-12.52%, resulting in stronger water-solid interaction. The results of laser confocal microscopy (CLSM) proved that a strengthened gluten network (protein percentage area ≥ 40.28%; junction density ≥ 10.96 × 10^-4) appeared. Therefore, appropriate precooking treatment could effectively improve the sensory quality and tensile properties of ARNs by enhancing the tightly bound water ratio and strengthening the gluten network.

Effect of sanxan gel on the quality of salt-free noodles during cooking

The effect and mechanism of sanxan on the quality of salt-free noodles (SFNs) were investigated from different cooking stages (initial stage, 1 min; optimum cooking time, OCT; overcooked time, OT). The results showed significant changes in the cooking process with the addition of 1.2% sanxan. The OCT for noodles with 1.2% sanxan (experimental group, EG) was extended from 5 to 7 min compared to the non-added noodles (blank group, BG) and 1.5% salt-containing noodles (control group, CG). The hardness and adhesiveness of BG, EG, and CG all decreased significantly during cooking. In contrast, the springiness, maximum tensile strength, and tensile fracture distance trended first to increase and then to decrease. At OCT, EG had the highest hardness (3971.69 ± 94.49 g), adhesiveness (372.26 ± 33.56 g s), and maximum tensile strength (41.51 ± 2.76 g), which remained large even after overcooking. However, those in BG and CG showed a significant reduction (p < 0.05). The proportion of free water increased progressively as cooking progressed, with CG showing the largest increase, from 82.29% to 91.19%, whereas EG showed the smallest increase, from 78.34% to 86.02%. During the cooking process, the addition of sanxan delayed the water migration, whereas salt promoted it. Sensory evaluation showed that EG was smoother in appearance than BG and tasted malty with a slight stickiness. Moreover, EG had the smallest k₁ and C_∞ values. Thus, sanxan is an effective additive to enhance the quality of SFNs and can replace the role of salt in noodles in some properties, which is beneficial for the development of SFNs.

Impact of okara on quality and in vitro starch digestibility of noodles: The view based on physicochemical and structural properties

The development of cereal foods with slow starch digestibility is important for the general improvement of human health. In this study, the quality properties of noodles with added okara, in vitro starch digestibility, and the underlying mechanisms of the influence of okara on noodles were studied. Low concentrations (5 and 10 %) of okara improved the texture, cooking, and sensory properties of the noodles. Okara decreased the rapidly digestible starch (RDS) content, increased the resistant starch (RS) content, and reduced the predicted glycaemic index (pGI) of noodles. The pasting viscosity, thermal stability, and dynamic rheological results indicated that okara improved the starch crystallite stability of wheat flour and viscoelasticity of dough. Moreover, Fourier transform infrared (FTIR) spectroscopy showed that okara promoted the formation of starch-lipid complexes and improved the short-range structural order of starch. Additionally, microstructure imaging and protein network analysis (PNA) indicated that low addition of okara promoted the compactness of the okara-gluten-starch matrix, thus reducing the contact between starch and hydrolytic enzymes. These results reveal the effect of okara on the quality properties and starch digestibility in a starch-gluten complex system.

Study on the quality characteristics of hot-dry noodles by microbial polysaccharides

The effect of curdlan gum (CG), gellan gum (GG), and xanthan gum (XG) on the quality characteristics of hot-dry noodles (HDN) was investigated. The rheology properties were used to evaluate the quality of the dough, the textural, viscosity, cooking characteristics and water states were investigated to study the quality changes of HDN. Three microbial polysaccharides were found that it could improve the quality of wheat flour and significantly increase the starch viscosity of HDN and delay the water migration rate of HDN. When 0.2% CG, 0.5% GG, and 0.5% XG were added, the HDN showed the best flour swelling power, texture, and tensile properties, and the structure of gluten network was significantly improved. The flourier transform infrared spectroscopy results showed that microbial polysaccharides with appropriate concentrations changed the formation of hydrogen bond in HDN, decreased α-helix and increased β-turn content. Meanwhile, the relative continuous and complete gluten network was formed, which could be proven by microstructure observation. This study provides a reference for functionality applications of HDN with microbial polysaccharides.

Recent Advances in the Study of Wheat Protein and Other Food Components Affecting the Gluten Network and the Properties of Noodles

Upon hydrating and mixing wheat flour, wheat protein forms a network that strongly affects the structure and physicochemical properties of dough, thus affecting the properties of noodles. Different approaches have been taken to alter the gluten network structure in order to control the dough properties. In the current review, we summarize the structure and function of wheat protein, including glutenin and gliadin, and describe food components that may affect noodle quality by interacting with wheat protein. In fact, the ratio of glutenin to gliadin is closely related to the viscosity of dough, and disulfide bonds also contribute to the gluten network formation. Meanwhile, wheat protein coexists with starch and sugar in wheat dough, and thus the nature of starch may highly influence gluten formation as well. Salts, alkali, enzymes and powdered plant food can be added during dough processing to regulate the extensional properties of wheat noodles, obtaining noodles of high quality, with improved sensory and storage properties. This review describes specific methods to reinforce the wheat protein network and provides a reference for improving noodle quality.

Versatile wheat gluten: functional properties and application in the food-related industry

Gluten is a key component that allows wheat flour to form a dough, and it is also a byproduct of the production of wheat starch. As a commercial product, wheat gluten is increasingly used in the food-related industry because of its versatile functional properties and wide range of sources. Wheat gluten is manufactured industrially on a large scale through the Martin process and batter process and variants thereof. Gliadin and glutenin impart cohesiveness and elasticity properties, respectively, to wheat gluten. The formation of gluten networks and polymers depends mainly on covalent bonds (disulfide bonds) and noncovalent bonds (ionic bonds, hydrogen bonds, and hydrophobic interactions). The multifunctional properties (viscoelasticity, gelation, foamability, etc.) of wheat gluten are shown by rehydration and other processing techniques. Wheat gluten has been widely used in wheat-based products, food auxiliary agents, food packaging, encapsulation and release of food functional ingredients, food adsorption and heat insulation materials, special purpose foods, and versatile applications. In the future, wheat gluten protein will be used as an important raw material to participate in the development and preparation of various food and degradable materials, and the application potential of wheat gluten in food-related industries will be massive. This review summarizes the main manufacturing processes, composition, and structure of gluten protein, and the various functional properties that support its application in the food and related industries.

Effect of processing on the solubility and molecular size of oat β-glucan and consequences for starch digestibility of oat-fortified noodles

White wheat salted noodles containing oats have a slower digestion rate those without oats, with potential health benefits. Oat β-glucan may play an important role in this. Effects of sheeting and shearing during noodle-making and subsequent cooking on β-glucan concentration, solubility, molecular size and starch digestibility were investigated. The levels of β-glucan were reduced by 16% after cooking, due to the loss of β-glucan into the cooking water. Both the noodle-making process and cooking increased the solubility of β-glucan but did not change its average molecular size. Digestion profiles show that β-glucan in wholemeal oat flour did not change starch digestion rates compared with isolated starch, but reduced the starch digestion rate of oat-fortified wheat noodles compared to the control (wheat noodles). Confocal laser scanning microscopy suggests that interaction between β-glucan and protein contributes to the starch-protein matrix and changes noodle microstructure, and thus alters their digestibility.

Modelling multiphasic starch digestograms with multiterm exponential and non-exponential equations

The first-order kinetic and the Peleg models were respectively expanded to yield three-term exponential and non-exponential models for triphasic starch digestograms. Ten typical samples are presented, and the models suitably (r² > 0.95; p < 0.05) described their digestograms. Nonlinear regression constraints or conditions to ensure the stability, convergence, and practicability of the models are discussed. These were extended to existing two-term exponential models and an adapted two-term non-exponential model. The two-term models adequately (r² > 0.88; p < 0.05) described biphasic digestograms with practical digestion parameters, as exemplified by 10 presented digestograms. These multiterm models will add to models for describing multiphasic starch digestograms, ensuring such are properly modelled with objective predictability indices to assist researchers and for inter-laboratory comparisons. The integrals of the multiterm exponential and non-exponential models are presented to estimate or predict in vitro glycaemic indices.

Hydration and plasticization effects of maltodextrin on the structure and cooking quality of extruded whole buckwheat noodles

In order to improve the structure and cooking quality of extruded whole buckwheat noodles (EWBN), maltodextrin (MD), the homologous substances of starch, was added to buckwheat flour to prepare the EWBN. Hydrogen bonds formed between MD and buckwheat starch molecules and the crystallinity of EWBN decreased as determined by FT-IR and X-ray diffraction, which indicated plasticization effects of MD on buckwheat starch. The content of tightly bound water first increased and then decreased with the increasing amount of MD and the cooking time of EWBM decreased from 5.4 to 3.1 min due to the hydration effects of MD. The cooking loss first decreased and then increased, and showed a minimum value of 9.22% when adding 1 wt% of MD. For texture properties, the hardness, stickiness, chewiness and elongation at break of EWBN first increased and then decreased with the addition of MD, and all reached the maximum value at 3 wt% of MD. These findings showed the potential of adding MD, especially at the appropriate concentration, for improving structure and cooking quality of EWBN.

Storage temperature and time affect the enzyme resistance starch and glycemic response of cooked noodles

White-salted noodles are prepared, stored and consumed in various ways. However, relationships among cooking and storage conditions on nutritional functionality are not fully understood. The manuscript elucidates the mechanism of formation of resistant starch (RS) leading to slower digestion rate of variously cooked (boiled, steamed, stir-fried, fried and microwave heated) noodles followed by storage under different conditions (-18, 4 and 25 °C for 4, 24 and 48 h). RS content of noodles stored at 25 °C was higher than noodles stored at 4 °C, which was consistent with increases in the degree of crystallinity during storage. We showed that the residual moisture content primarily facilitated the mobility of starch chains and contributed towards the increase in RS associated with the decrease of enzyme susceptivity of noodles after storage. Evidence that supramolecular organization (helical structure and crystallinity) had a more pronounced effect than the macroscopic structure such as compactness or bulk density was also provided.

Effects of endogenous proteins on rice digestion during small intestine (in vitro) digestion

Rices with higher protein contents are nutritionally desirable. This study investigates the effects of endosperm proteins on starch in vitro digestibility in cooked and uncooked rice, and the mechanisms underlying any changes. The composition of rice endosperm proteins and the morphologies of proteins and starch granules were determined by SDS-PAGE and confocal microscopy. Starch molecular fine structure was examined using size-exclusion chromatography. In vitro digestion showed that the digestion rate coefficients (k) of cooked rice flour were significantly lower than those of isolated starch or of a starch-protein mixture. (e.g for samples from SWR4, k is 9.6, 12.9 and 11.6 × 10^-2 min^-1 for cooked rice flour, isolated starch and starch-protein mixture, respectively). For uncooked samples, digestion rate coefficients were 1.4, 1.5 and 1.8 × 10^-2 min^-1 for flour, starch-protein mixture and starch, respectively. The digestion rates in cooked samples were higher than those in uncooked samples. This suggests that, in cooked samples, starch digestion rates are more affected by the protein physical barrier than by some chemical effect (e.g. hydrogen bonding between protein and starch), while in uncooked samples, a chemical effect from protein is more pronounced than a physical barrier from protein.

Effects of multi-frequency ultrasound on physicochemical properties, structural characteristics of gluten protein and the quality of noodle

In this study, the influence of multi-frequency ultrasound irradiation on the functional properties and structural characteristics of gluten, as well as the textural and cooking characteristics of the noodles were investigated. Results showed that the textural and cooking characteristics of noodles that contain less gluten pretreated by multi-frequency ultrasonic were ultrasonic frequency dependent. Moreover, the noodles that contain a smaller amount of sonicated gluten could achieve the textural and cooking quality of commercial noodles. There was no significant difference in the cooking and texture characteristics between commercial noodles and noodles with 12%, 11%, and 10% gluten pretreated by single-frequency (40 kHz), dual-frequency (28/40 kHz), and triple-frequency sonication (28/40/80 kHz), respectively. Furthermore, the cavitation efficiency of triple-frequency ultrasound was greater than that of dual-frequency and single-frequency. As the number of ultrasonic frequencies increased, the solubility, water holding capacity and oil holding capacity of gluten increased significantly (p < 0.05), and the particle size was reduced from 197.93 ± 5.28 nm to 110.15 ± 2.61 nm. Furthermore, compared to the control group (untreated), the UV absorption and fluorescence intensity of the gluten treated by multi-frequency ultrasonication increased. The surface hydrophobicity of gluten increased from 8159.1 ± 195.87 (untreated) to 11621.5 ± 379.72 (28/40/80 kHz). Raman spectroscopy showed that the α-helix content of all sonicated gluten protein samples decreased after sonication, while the β-sheet and β-turn content increased, and tryptophan and tyrosine residues were exposed. Through scanning electron microscope (SEM) analysis, the gluten protein network structure after ultrasonic treatment was loose, and the pore size of the gluten protein network increased from about 10 μm (untreated) to about 26 μm (28/40/80 kHz). This work elucidated the effect of ultrasonic frequency on the performance of gluten, indicating that with increasing frequency combination increases, the ultrasound effect became more pronounced and protein unfolding increased, thereby impacting the functional properties and the quality of the final product. This study provided a theoretical basis for the application of multi-frequency ultrasound technology in the modification of gluten protein and noodle processing.

RS Content and eGI Value of Cooked Noodles (I): Effect of Cooking Methods

Noodles are widely consumed in China, which can be cooked in different ways. The effects of different cooking methods (boiling, steaming, microwave heating, stir-frying and frying) on the resistance starch (RS) content and digestive properties (digestion rate, digestibility and estimated glycemic index (eGI) value) of noodles were investigated. The RS content was greatly affected by the cooking time, and it was varied when the noodles were optimally cooked using different cooking methods. The RS contents of the microwaved and stir-fried noodles were relatively high (0.59%-0.99%), but it was lower (0.43%-0.44%) in the boiled and steamed noodles. Microwaved noodles showed the slowest digestion rate and the lowest eGI. Due to the limited water within fried noodles, none RS was found in the fried noodles, whereas stir-fried noodles showed RS5 formation from the XRD and DSC results. Compared with boiled and steamed noodles, the microwaved noodles showed a more compact morphology without porous holes on the surface, whereas fried noodles showed irregular morphology. The results indicated that the digestive properties of noodles made with the same ingredients can be greatly altered by using different cooking methods, and the digestive properties of different cooked noodles are worthy of confirmation using in vivo analysis.