Effect of extrusion cooking on chemical structure, morphology, crystallinity and thermal properties of sorghum flour extrudates

Incorporation of germinated lupin into corn-based extrudates: Focus on starch digestibility, matrix structure and physicochemical properties

The research aimed to assess the effects of incorporating germinated Lupinus angustifolius flour into corn extrudates for different periods (3, 5, and 7 days), focusing on starch digestibility, morphological structure, thermal, and pasting properties. Extrudate with germinated lupinus flour for 7 days (EG7) significantly increased the content of slowly digestible starch up to 10.56% (p < 0.05). Crystallinity increased up to 20% in extrudates with germinated flour compared to extrudates with ungerminated flour (EUG), observing changes at the molecular level by FTIR that impact the thermal and pasting properties. X-ray diffraction revealed angles of 2θ = 11.31, 16.60, 19.91, and 33.04 as a result of the germination and extrusion processes. Microstructural analysis indicated starch-protein interactions influencing changes in calorimetry, viscosity, X-ray diffraction, and digestibility. PCA allowed establishing that the addition of germinated flours significantly affected the properties and microstructural characteristics of extruded products, potentially affecting digestibility and nutritional quality.

Impact of genotypic variation and cultivation conditions on the techno-functional characteristics and chemical composition of 25 new Canadian quinoa cultivars

The utilization of quinoa in food production requires comprehensive information on its processing characteristics. Twenty-five new quinoa cultivars developed by the Northern Quinoa Breeding Program, grown in three Canadian locations over two seasons, were characterized for their proximate composition, pasting properties, thermal properties, water absorption index, water solubility index, foaming capacity, foaming stability, oil holding capacity, and emulsion activity crucial for potential food applications. Results showed significant variations in the proximate composition among the cultivars, which was also influenced by the growing location and harvest year. Significant differences (p < 0.05) were also observed in the pasting properties, thermal stability, hydration properties, foaming properties, oil holding capacity, and emulsion activity. The hierarchical cluster and principal component analyses were associated with five distinct clusters of quinoa cultivars, each with unique techno-functional attributes, suggesting their potential for different food applications. These findings emphasize the need for further research to explore the performance of quinoa flours in specific food products and their impact on end-product quality.

Valorisation of jackfruit seed flour in extrusion and bakery products: a review

Jackfruit seeds are a highly nutritious, underutilized byproduct that can combat malnutrition and promote a healthy diet. This review evaluates the effects of jackfruit seed flour (JSF) on extrusion and bakery processing, examining its nutritional, functional, and physical properties. Comprehensive analysis showed that JSF in extruded and bakery products improves their nutritional properties and increases functional properties such as bulk density and water holding capacity, whereas it decreases oil holding capacity and expansion ratio. Furthermore, the textural and colour properties became poorer with the higher concentration of JSF due to the absence of gluten. Consumer studies revealed that the overall acceptability of extruded products containing JSF was higher than that of bakery products with similar substitutions. However, optimal formulations are needed to balance nutritional enhancement with desirable textural properties, and the sustainable utilization of this byproduct can lead to the development of a variety of nutritious food products.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01665-2.

Proximate, structural, textural, sensory and microbiological properties of non-gluten extrudate using Sorghum (Sorghum bicolor L. Moench) and a sprouted legume (Phaseolus lunatus L.)

The inclusion of legumes as functional ingredients in a gluten-free extrusion process has been gaining attention in recent times. In this study, sorghum and germinated lima bean flour (100, 90:10, 80:20, 70:30, 60:40 and 50:50) was extruded (feed moisture - 18%, screw speed - 250 rpm, barrel temperatures 50 °C-120 °C-120 °C, die hole diameter - 3 mm) and analysed for functional, proximate, textural, structural, pasting, microbiological and sensory properties. With 100% sorghum used as control, lima beans addition significantly (p < 0.05) improved the loose (0.37-0.44 g/ml) and packed (0.63-0.72 g/ml) bulk density, while water (5.00-3.15 g/g) and oil (2.45-1.60 g/g) absorption capacity and expansion ratio (3.11-2.30) decreased, respectively. An increase in protein (12.77-18.00%), crude fibre (2.58-5.17%) and ash content (2.11-3.12%) were observed in the extrudate, while the (L*) colour parameter (54.49-43.62), hardness (180.04-78.36 N) and pasting viscosities reduced with addition of lima beans. The structural micrograph depicted air-trapped bubbles with thick walls after adding lima beans, while a notable decline in microbial count below approved limits was observed after 8 weeks of storage. Sensory scores showed that values obtained were above average with the 90:10 sorghum-lima bean ratio having the highest score. The economic and industrial value of underutilised legumes such as lima bean can be promoted as functional ingredients via extrusion in addressing coeliac disease and alternative sources of protein, especially in developing countries.

Insight into the relationship between the starch crystalline structure and textural quality and physicochemical properties of reconstituted rice: Influence of feed moisture content

Reconstituted rice was prepared by extrusion with different feed moistures (30 %, 33 %, 36 %, 39 % and 42 %), and the relationship between the crystalline structure, physicochemical properties, and textual quality of reconstituted rice was studied. The results revealed that, with the feed moisture increased (33 %-36 %), the gelatinization degree reached 97.28 % and the bound water content increased by 23.58 %. The water absorption index and swelling power index reached 8.35 g/g and 9.46 g/g, respectively, and the texture properties were close to those of native rice. Higher extrusion feed moisture (39 %-42 %) increased the setback value (206.00 cP) and breakdown value (721.33 cP) of starch, and the hardness and gumminess of reconstituted rice were also increased (p < 0.05). The starch crystalline structure was disrupted by extrusion and changed to a surface fractal structure, the relative crystallinity decreased from 26.87 % to 6.68 %, and the degree of order decreased from 1.680 to 1.006. Correlation analysis revealed that the crystalline structure of starch and water distribution would affect the textural and hydration properties of reconstituted rice. The results provide theoretical references and data support for improving the edibility and quality of reconstituted rice and enhancing the utilization rate of broken rice.

Technology for Blending Recombined Flour: Substitution of Extruded Rice Flour, Quantity of Addition, and Impact on Dough

In a previous study, rice bread was prepared using a combination of rice-wheat mixed flour. To investigate the impact of the partial adoption of extruded rice flour (ERF) on mixed flour (MF) and mixed dough (MD), the effects of adding ERF on the pasting, mixing characteristics, texture, and water retention of the MF and MD were examined by a rapid visco analyzer (RVA), Mixolab, texture profile analysis (TPA), and a low-field nuclear magnetic resonance analyzer (LF-NMR). The PV, TV, BD, FV, and SV of the MF declined as the incorporated amount of ERF increased. There was no significant difference in the PT at the 5-15% addition level (p < 0.05), but it showed an increasing trend at the 20-30% level (p < 0.05). The incorporation of ERF led to a significant increase in the water absorption (WA) of the MD, while the DT, ST, C2, C3, C4, and C5 exhibited a declining trend. The texture analysis revealed a significant decrease in the dough hardness with the addition of ERF, with a 55% reduction in the hardness of the 30% improved mixed dough (IMD), and the cohesiveness increased significantly (p < 0.05). The IMD was mainly composed of weakly bound water. The content of weakly bound water increased with the ERF amount.

Peruvian fava beans for health and food innovation: physicochemical, morphological, nutritional, and techno-functional characterization

Peruvian fava beans (PFB) are used in traditional cuisine as a nutrient-rich, flavorful, and textural ingredient; however, little is known about their industrial properties. This study evaluated the physicochemical, nutritional, and techno-functional characteristics of PFB varieties: Verde, Quelcao, and Peruanita. PFB exhibited distinct physical characteristics, quality parameters, and morphology. The color patterns of the seed coat and the hardness were the main parameters for distinguishing them. Nutritionally, all three samples exhibited high protein (23.88-24.88 g/100 g), with high proportion of essential amino acids, high dietary fiber (21.74-25.28 g/100 g), and mineral content. They also contain polyphenols (0.79-1.25 mg GAE/g) and flavonoids (0.91-1.06 mg CE/g) with antioxidant potential (16.60-21.01 and 4.68-5.17 µmol TE/g for ABTS and DPPH assays, respectively). Through XRD measurements, the semi-crystalline nature of samples was identified, belonging to the C-type crystalline form. Regarding techno-functionality, PFB flours displayed great foaming capacity, with Verde variety being the most stable. Emulsifying capacity was similar among samples, although Peruanita was more stable during heating. Upon heating with water, PFB flours reached peak viscosities between 175 and 272 cP, and final viscosities between 242 and 384 cP. Quelcao and Verde formed firmer gels after refrigeration. Based on these results, PFB would be useful to developing innovative, nutritious, and healthy products that meet market needs.

Understanding the mechanism for sodium tripolyphosphate in improving the physicochemical properties of low-moisture extrusion textured protein from rapeseed protein and soybean protein blends

Our previous experiments found that rapeseed protein (RP) has applicability in low-moisture textured proteins. The amount of RP added is limited to <20 %, but the addition of 20 % RP still brings some negative effects. Therefore, in order to improve the quality of 20%RP textured protein, this experiment added different proportions of sodium tripolyphosphate (STPP) to improve the quality of the product, and studied the physical-chemical properties and molecular structure changes of the product to explore the possible modification mechanism. The STPP not only improved the expansion characteristics of extrudates, but also increased the brightness of the extrudates, the rehydration rate. In addition, STPP increased the specific mechanical energy during extrusion, decreased the material mass flow rate. Furthermore, STPP decreased the starch digestibility, increased the content of slow-digesting starch and resistant starch. STPP increased the degree of denaturation of extrudate proteins, the proportion of β-sheets in the secondary structure of proteins, as well as the intermolecular hydrogen bonding interactions. The gelatinization degradation degree of starch molecules also decreased with the addition of STPP. STPP also increased the protein-starch interactions and enhanced the thermal stability of the extrudate. All these indicate that STPP can improve the physical-chemical properties of extrudate.

Exploring the relationship between starch structure and physicochemical properties: The impact of extrusion on highland barley flour

Highland barley (HB) is an intriguing plateau cereal crop with high nutrition and health benefits. However, abundant dietary fiber and deficient gluten pose challenges to the processing and taste of whole HB products. Extrusion technology has been proved to be effective in overcoming these hurdles, but the association between the structure and physicochemical properties during extrusion remains inadequately unexplored. Therefore, this study aims to comprehensively understand the impact of extrusion conditions on the physicochemical properties of HB flour (HBF) and the multi-scale structure of starch. Results indicated that the nutritional value of HBF were significantly increased (soluble dietary fiber and β-glucan increased by 24.05%, 19.85% respectively) after extrusion. Typical underlying mechanisms based on starch structure were established. High temperature facilitated starch gelatinization, resulting in double helices unwinding, amylose leaching, and starch-lipid complexes forming. These alterations enhanced the water absorption capacity, cold thickening ability, and peak viscosity of HBF. More V-type complexes impeded amylose rearrangement, thus enhancing resistance to retrogradation and thermal stability. Extrusion at high temperature and moisture exhibited similarities to hydrothermal treatment, partly promoting amylose rearrangement and enhancing HBF peak viscosity. Conversely, under low temperature and high moisture, well-swelled starch granules were easily broken into shorter branch-chains by higher shear force, which enhanced the instant solubility and retrogradation resistance of HBF as well as reduced its pasting viscosity and the capacity to form gel networks. Importantly, starch degradation products during this condition were experimentally confirmed from various aspects. This study provided some reference for profiting from extrusion for further development of HB functional food and "clean label" food additives.

Effect of different screw speeds on the structure and properties of starch straws

To illustrate the action mechanism of screw speed on the performance of starch-based straws during the extrusion process, starch-based straws at different screw speeds were prepared using a twin-screw extruder and the structures and characteristics were compared. The results indicated that as screw speeds improved from 3 Hz to 13 Hz, the A chain of amylopectin increased from 25.47 % to 28.87 %, and the B3 chain decreased from 6.34 % to 3.47 %. The absorption peak of hydroxyl group shifted from 3296 cm-1 to 3280 cm-1. The relative crystallinity reduced from 13.49 % to 9.89 % and the gelatinization enthalpy decreased from 3.5 J/g to 0.2 J/g. The performance of starch straws did not increase linearly with increasing screw speeds. The starch straw produced at screw speed of 7 Hz had the largest amylose content, the highest gelatinization temperature, the minimum bending strength, and the lowest water absorption rate in hot water (80 °C). Screw speed had a remarkable impact on the mechanical strength, toughness and hydrophobicity of starch-based straws. This study revealed the mechanism of screw speed on the mechanical strength and water resistance of starch straws in the thermoplastic extrusion process and created the theoretical basis for the industrial production of starch-based straws.

Structural modification of starch and protein: From the perspective of gelatinization degree of oat flour

To clarify the relationship between gelatinization degree and structure characteristics, oat kernels were roasted to different gelatinization degree of 15 %-90 % based on tempering water content of 22.5 %-35 %, and the structure characteristics of starch and protein were evaluated. The results showed that the increased gelatinization degree dependent on tempering water content promoted protein aggregation on the surface of starch particles, forming larger aggregates with molecular weight >100 kDa. Oat kernels presented a dense starch gel network structure induced by gelatinized starch. Partial gelatinization of starch led to a decrease in pasting viscosities (setback viscosity, 3.91 Pa·s-1.59 Pa·s) and enthalpy (5.12 J/g-0.11 J/g). With the increase of gelatinization degree, the starch crystal structure conversed from A + V type to V type, accompanied by the formation of starch-lipid complexes and a decrease of relative crystallinity (22.28 %-8.72 %). Moreover, 50 % gelatinized oat flour possessed the highest β-sheet structure (38.04 %), but a decrease in surface hydrophobicity and an increase in endogenous fluorescence intensity were found in oat flour of gelatinization degree >50 %. This study provided a theoretical reference for the application of oat flour with different gelatinization degrees to match suitable products.

Effects of Extrusion Technology on Physicochemical Properties and Microstructure of Rice Starch Added with Soy Protein Isolate and Whey Protein Isolate

In order to improve the retrogradation of rice starch (RS) and the quality of rice products, soy protein isolate (SPI), whey protein isolate (WPI), and rice flour were mixed and further extruded into mixed flour. The physicochemical properties and morphology of starch of extruded rice flour (ERS) and starch of extruded mixtures of SPI, WPI, and rice flour (SPI-WPI-ERS) were analyzed. The distribution of amylopectin chain length, molecular weight, microstructure, crystallinity, short-range ordered structure, pasting properties, and thermodynamic properties of RS, ERS, and SPI-WPI-ERS were measured. The results showed that, compared with rice starch, the proportion of long-chain starch, total starch content, and molecular weight were decreased in ERS and SPI-WPI-ERS, but the proportion of short-chain and amylose content was increased. The short-range order structure was destroyed. The water absorption of ERS and SPI-WPI-ERS was much higher than rice starch at 55 °C, 65 °C, and 75 °C, but lower than that of rice starch at 95 °C. Therefore, the retrogradation characteristics of SPI-WPI-ERS were improved. The setback of rice starch products was reduced and the setback of SPI-WPI-ERS was lower than that of ERS. Overall, the retrogradation of rice starch was delayed by adding exogenous protein and extrusion technology, and the application range of rice flour in staple food products was broadened.

Impact of Oat Supplementation on the Structure, Digestibility, and Sensory Properties of Extruded Instant Rice

The addition of oat at varying percentages (26%, 32%, 38%, 44% and 50%) was used to evaluate the structural, microstructural, and physicochemical changes in instant-extruded rice (IER). A mixture of broken rice and oat flour was extruded in a twin-screw extruder. It was found that when adding 44% oats, the gelatinization degree of the mixed powder was the lowest (89.086 ± 1.966%). The dietary fiber content increased correspondingly with the increase in oat addition. Analyses of texture properties revealed that the hardness, adhesive, and resilience values increased and then decreased with oat addition. Compared with other common instant rice (IR), the advantages of IER were evaluated in terms of microstructure, digestive performance, and flavor. IER with 44% oat addition obtained in this study had higher hardness, adhesiveness, rehydration time, and sensory score, and the content of resistant starch (RS) reached 6.06%. The electronic nose and electronic tongue analyses could distinguish the flavor of different IR efficiently. This study showed the feasibility of preparing fiber-enriched IER. The results demonstrated the potential for the development and utilization of broken rice, providing a reference for the development of IER.

Impact of moisture content on microstructural, thermal, and techno-functional characteristics of extruded whole-grain-based breakfast cereal enriched with Indian horse chestnut flour

The use of non-conventional seed flour is of interest in obtaining healthy breakfast cereals. The research aimed to study the physico-functional, bioactive, microstructure, and thermal characteristics of breakfast cereals using scanning electron microscopy, X-ray diffractometry, and differential scanning calorimeter. The increase in feed moisture content (16 %) enhanced the bulk density (5.24 g/mL), water absorption index (7.76 g/g), total phenolic content (9.03 mg GAE/g), and antioxidant activity (30.36 %) having desirable expansion rate (2.84 mm), water solubility index (48 %), and color attributes. The microstructure showed dense inner structures with closed air cells in extruded flours. Extrusion treatment rearranged the crystalline structure from A-type to V-type by disrupting the granular structure of starch, reducing its crystallinity, and promoting the formation of an amylose-lipid complex network. Increasing conditioning moisture enhanced the degree of gelatinization (%), peak gelatinization temperature (Tp), and starch crystallinity (%) and reduced the gelatinization enthalpy (ΔHG) and gelatinization temperature ranges. The results reported in this study will help industries to develop innovative and novel food products containing functional ingredients.

Sorghum Flour and Sorghum Flour Enriched Bread: Characterizations, Challenges, and Potential Improvements

A Sorghum flour (SF) is a leading and prominent food source for humans in African countries. Recently extensive studies have been conducted on Sorghum bread (SB) or sorghum composite bread (SCB), covering various aspects. However, there are many technical challenges in the formation of SF and sorghum composite flour (SCF) that impact the quality of the bread and fail to meet the consumer's desires and expectations. This review primarily focuses on the characteristics of SF, SCF, SB, and SCB, with discussions encompassing the rheological and morphological properties of the dough, improvement strategies, and bread quality. Moreover, a comprehensive analysis has been conducted to investigate the behavior of SF and SCF along with a discussion of the challenges affecting bread quality and the strategies applied for improvement. The significant demand for nutrients-rich and gluten-free bread indicates that sorghum will become one of the most vital crops worldwide. However, further comprehensive research is highly demanded and necessary for an in-depth understanding of the key features of SF and the resulting bread quality. Such understanding is vital to optimize the utilization of sorghum grain in large-scale bread production.

Effect of continuous instant pressure drop treatment on the rheological properties and volatile flavor compounds of whole highland barley flour

Continuous instant pressure drop (CIPD) treatment effectively reduces microbial contamination in whole highland barley flour (WHBF). Base on it, this study further investigated its effects on flour properties (especially rheological properties) and volatile compounds (VOCs) profile of WHBF, and compared it with that of ultraviolet-C (UV-C), ozone and hot air (HA) treatments. The results showed that the damaged starch content (6.0%) of CIPD-treated WHBF was increased, leading to a rough surface and partial aggregation of starch particle, thereby increasing the particle size (18.06 μm of D10, 261.46 μm of D50 and 534.44 μm of D90). Besides, CIPD treatment exerted a positive influence on the structure and rheological properties of WHBF, including an elevation in pasting temperature and viscosity. Notably, CIPD-treated WHBF exhibited higher storage modulus and loss modulus compared to the other three groups of sterilization treatments, contributing to the formulation of a better-defined and stable gel strength (tan δ = 0.38). UV-C and ozone, as cold sterilization techniques, also induced alterations in specific characteristics of WHBF. UV-C treatment led to changes in WHBF's crystallinity, while ozone treatment caused modifications in the secondary protein structure of WHBF. A total of 68 VOCs were identified in raw WHBF (including 3 acids, 19 alcohols, 25 aldehydes, 1 alkene, 8 esters, 2 ethers, 3 furans, and 7 ketones). The maximum flavor-contributing VOC in CIPD-treated WHBF remained dimethyl sulfide monomer (cabbage aroma), consistent with the raw WHBF. Conversely, in HA-treated WHBF, the maximum flavor-contributing VOC shifted to 2-furanmethanethiol monomer (roasted coffee aroma), altering the initial flavor presentation. These findings will provide strong support for the application of CIPD technology in the powdery foods industry.

Comparison of the generation of α-glucosidase inhibitory peptides derived from prolamins of raw and cooked foxtail millet: In vitro activity, de novo sequencing, and in silico docking

Foxtail millet prolamin has been demonstrated to have anti-diabetic effects. In this study, we compared the generation of anti-α-glucosidase peptides derived from prolamins of raw and cooked foxtail millet (PRFM and PCFM). PRFM and PCFM hydrolysates (PRFMH and PCFMH) both exhibited α-glucosidase inhibitory activity. After ultrafiltration according to molecular weight (Mw), the fraction with Mw < 3 kDa in PCFMH (PCFMH_<3) showed higher α-glucosidase inhibitory activity than that in PRFMH (PRFMH_<3). The composition of α-glucosidase inhibitory peptides identified by de novo sequencing in PCFMH_<3 and PRFMH_<3 was compared by virtual screening, combining biological activity, net charge, grand average of hydropathicity (GRAVY), and key hydrophobic amino acids (Met, Pro, Phe, and Leu). We found that the proportion of peptides with excellent α-glucosidase binding force in PCFMH_<3 was higher than in PRFMH_<3. Overall, cooking may positively affect the generation of peptides that perform well in inhibiting α-glucosidase derived from foxtail millet prolamin.

Physicochemical characteristics and structural changes of fermented faba bean extrudates prepared by twin-screw extrusion

In this study, fermented faba bean blends with different locust bean gum (LBG) contents were processed in a co-rotating twin-screw extruder. The effects of extrusion process variables and the LBG level on physicochemical, sensory and structural characteristics of expanded extrudates were investigated. The results showed that physical characteristics of extrudates including expansion, apparent density and texture were significantly affected by variation of screw speed and die temperature, but the effect of LBG level was only significant for expansion and density. FTIR-ATR analysis revealed that a significant change occurred in the protein secondary structure as well as in the short-range ordered molecular structure of starch during fermentation and extrusion. The X-ray diffraction patterns of extrudates exhibited V-type pattern. Microstructure of the extrudates analyzed by FE-SEM exhibited variations in cell size and wall thickness depending on extrusion processing conditions and LBG level, which in turn lead to different textural perceptions.

Multi-Scale Structural Insights into Enzymatically Hydrolyzed Lentil Starch Concentrates Prepared by In Vitro Method Using Different Types of Enzymes

This study was undertaken to investigate the enzymatic hydrolysis of lentil starch concentrates from conventional cooked seeds (CCLSC) by the action of different types of enzymes, including pancreatin (PC-EHSC), heat-stable α-amylase (HS-EHSC), β-amylase (βA-EHSC), amyloglucosidase (AMG-EHSC), and multi-enzymes (βA-HS-AMG-EHSC); their multi-scale structural characteristics of the enzymatic hydrolysis products of lentil starch concentrates were compared. The morphological features distinguished among different samples. The Fourier-transform infrared spectroscopy and solid-state ¹³C CP/MAS NMR spectral features indicated the possible formation of a binary and ternary complex among amylose, protein and lipids. The X-ray diffraction results revealed that the V-type characteristic diffraction peaks were more obvious for samples including PC-EHSC and βA-EHSC, which was in line with their lowest polydispersity index (DP_n). PC-EHSC and βA-EHSC also showed an increased peak intensity of the scattering maximum on the small-angle X-ray scattering spectra, whereas CCLSC exhibited an overall lower peak intensity within the studied q range of scattering. The highest XRD crystallinity and the lowest DP_n value obtained for PC-EHSC indicated that the starch polymers modified by pancreatin could produce glucan chains with a comparatively homogenous M_w distribution that are readily recrystallized by hydrogen bonding through chain aggregation. Comparatively, the lowest relative crystallinity for HS-EHSC obtained from XRD suggested that thermostable α-amylolysis was unfavorable for the formation of starch structure with a higher degree of molecular order. This study could provide useful information for the needed research to obtain a deeper understanding of the impact of different amylolysis actions on the structural organization of starch hydrolysates and to provide a theoretical foundation for the development of fermentable enzymatically hydrolyzed starch with well-tailored physiological properties.

Modification mechanism of protein in rice adjuncts upon extrusion and its effects on nitrogen conversion during mashing

The traditional production of wort with adjunct-introduced was achieved by double mashing procedure, which hindered the utilization of proteins in adjunct and led to a deficiency of nitrogen in wort. In this study, the modification mechanism of the extrusion pretreatment on the structure characterization of rice flour protein was investigated. The decoction mashing procedure was performed to enhance the nitrogen conversion of the extruded rice adjunct. Decreased solubility along with disrupted secondary and tertiary structures of rice protein were observed after extrusion. As a result, the total nitrogen, free amino nitrogen, and free amino acids content of wort with extruded rice adjunct-introduced were improved by 23.28 %, 34.67 %, and 7.33 %, respectively, which could be verified by the electrophoretic patterns of the wort protein. The application of extrusion as a pretreatment of adjuncts can promote the protein availability of adjuncts in the decoction mashing stage.

Effect of sorbitol on the in vitro starch digestibility in semi-dried black highland barley noodles

Sorbitol is commonly used in semi-dried noodles for holding water, thus extending the shelf life. This research analyzed the effect of sorbitol on the in vitro starch digestibility in semi-dried black highland barley noodles (SBHBN). In vitro starch digestion revealed that the hydrolysis extent and digestive rate decreased with increasing sorbitol addition, although its inhibition abated when added >2 %. Compared with the control, adding 2 % of sorbitol lowered the equilibrium hydrolysis (C_∞) significantly (P < 0.05) from 75.18 to 66.57 % and decreased the kinetic coefficient (k) significantly (P < 0.05) by 20.29 %. Adding sorbitol increased the tightness of microstructure, relative crystallinity, V-type crystal, molecular structure order, and hydrogen bond strength of starch in cooked SBHBN. Meanwhile, gelatinization enthalpy change (ΔH) of starch in raw SBHBN was increased by adding sorbitol. In addition, the swelling power and amylose leaching in SBHBN added with sorbitol were reduced. Pearson correlations analysis observed significant (P < 0.05) correlations among short-range ordered structure, ΔH, and related in vitro starch digestion indexes of SBHBN after being added with sorbitol. These results revealed that sorbitol might form hydrogen bonds with starch, making it a potential additive to lower the eGI in starchy foods.

Effects of Extrusion on Starch Molecular Degradation, Order-Disorder Structural Transition and Digestibility-A Review

Extrusion is a thermomechanical technology that has been widely used in the production of various starch-based foods and can transform raw materials into edible products with unique nutritional characteristics. Starch digestibility is a crucial nutritional factor that can largely determine the human postprandial glycemic response, and frequent consumption of foods with rapid starch digestibility is related to the occurrence of type 2 diabetes. The extrusion process involves starch degradation and order-disorder structural transition, which could result in large variance in starch digestibility in these foods depending on the raw material properties and processing conditions. It provides opportunities to modify starch digestibility by selecting a desirable combination of raw food materials and extrusion settings. This review firstly introduces the application of extrusion techniques in starch-based food production, while, more importantly, it discusses the effects of extrusion on the alteration of starch structures and consequentially starch digestibility in various foods. This review contains important information to generate a new generation of foods with slow starch digestibility by the extrusion technique.

A review of extrusion-modified underutilized cereal flour: chemical composition, functionality, and its modulation on starchy food quality

Compared with three major cereals, underutilized cereals (UCs) are those with less use but having abundant bioactive components and better functionalities after proper processing. As a productive and energy-efficient technology, extrusion has been used for UC modification to improve its technological and nutritional quality. Extrusion could induce structural and quantitative changes in chemical components of UC flour, the degree of which is affected by extrusion intensity. Based on the predominant component (starch), functionalities of extruded underutilized cereal flour (EUCF) and potential mechanisms are reviewed. Considering bioactive compounds, it also summarizes the physiological functions of EUCF. EUCF incorporation could modulate the dough rheological behavior and starchy foods quality. Controlling extrusion intensity or incorporation level of EUCF is vital to achieve sensory-appealing and nutritious products. This paper gives comprehensive information of EUCF to promote its utilization in novel staple foods.

Development of Cellular High-Protein Foods: Third-Generation Yellow Pea and Red Lentil Puffed Snacks

This study aimed to evaluate how extrusion cooking conditions and microwave heating play a role in enhancing physical and thermal properties of third-generation expanded cellular snacks made from yellow pea (YP) and red lentil (RL) flours for the first time. Increasing temperature and moisture content during extrusion resulted in darker, crunchier and crispier products with higher expansion index (EI). Microwave heating after extrusion led to an increase in cell size and porosity of YP and RL products when qualitatively compared to extrusion alone. Additionally, extrusion followed by microwave heating resulted in extensive damage to starch granular structure and complete denaturation of proteins. Using microwave heating, as a fast and inexpensive process, following partial cooking with extrusion was demonstrated to greatly improve the physical and thermal properties of YP and RL snacks. Microwave heating following mild extrusion, instead of severe extrusion cooking alone, can potentially benefit the development of high quality nutritionally-dense expanded cellular snacks made from pulse flours.

Development and Characterization of Extrudates Based on Rapeseed and Pea Protein Blends Using High-Moisture Extrusion Cooking

Rapeseed protein is not currently utilized for food applications, although it has excellent physicochemical, functional, and nutritional properties similar to soy protein. Thus, the goal of this study was to create new plant-based extrudates for application as high-moisture meat analogs from a 50:50 blend of rapeseed protein concentrate (RPC) and yellow pea isolate (YPI) using high-moisture-extrusion (HME) cooking with a twin-screw extruder to gain a better understanding of the properties of the protein powders and resulting extrudates. The effects of extrusion processing parameters such as moisture content (60%, 63%, 65%, 70%), screw speed (500, 700, and 900 rpm), and a barrel temperature profile of 40-80-130-150 °C on the extrudates' characteristics were studied. When compared to the effect of varying screw speeds, targeted moisture content had a larger impact on textural characteristics. The extrudates had a greater hardness at the same moisture content when the screw speed was reduced. The specific mechanical energy (SME) increased as the screw speed increased, while increased moisture content resulted in a small reduction in SME. The lightness (L*) of most samples was found to increase as the target moisture content increased from 60% to 70%. The RPC:YPI blend was equivalent to proteins produced from other sources and comparable to the FAO/WHO standard requirements.

Protein Isolates from Raw and Cooked Foxtail Millet Attenuate Development of Type 2 Diabetes in Streptozotocin-Induced Diabetic Mice

SCOPE

Millet protein has received much attention due to its beneficial role in alleviating metabolic disease symptoms. This study aims to investigate the role and molecular mechanism of foxtail millet protein isolates, including protein isolates from raw and cooked foxtail millet in alleviating diabetes, including gut microbiota and intracellular signal pathways.

METHODS AND RESULTS

Protein isolates from raw and cooked foxtail millet are orally administered to streptozotocin (STZ)-induced diabetic mice for 5 weeks before hypoglycemic effect evaluation. The results show that foxtail millet protein isolates improve glucose intolerance and insulin resistance in diabetic mice. However, only the protein isolate from cooked foxtail millet reverse the weight loss trend and alleviate lipid disorders in diabetic mice. Besides, 16S rRNA sequencing show that both raw and cooked foxtail millet protein isolates altered diabetes-induced gut dysbiosis. In addition, western blotting analysis indicated that the protein isolate from cooked foxtail millet increases the expression levels of glucagon-like peptide-1 receptor (GLP-1R), phosphoinositide 3-kinase (PI3K), and phosphoinositide-protein kinase B (p-AKT)/AKT while the protein isolate from raw foxtail millet downregulates stearoyl-coenzyme A desaturase 1 (SCD1) level.

CONCLUSION

Both raw and cooked foxtail millet protein isolates can exert hypoglycemic effects in diabetic mice through rewiring glucose homeostasis, mitigating diabetes-induced gut dysbiosis, and affecting the GLP-1R/PI3K/AKT pathway.