Analysis of the mechanism of resistance to enzymatic hydrolysis of RS-5 resistant starch.

RS-5 refers to the resistant starch formed by complexation of starch molecules with other molecules. In this study, the molecular mechanism of RS-5 was analysed. First, it was found, when α-amylase acted on the starch-lipid complexes, the glucose residues involved in complexation cannot be hydrolyzed by α-amylase, while the glucose residues not directly involved in complexation can be hydrolyzed. Second, lipid molecules are not necessary for the formation of RS-5 and can be replaced with small peptides or decanal molecules. Considering the multiple health hazards that may result from excessive lipid intake, small peptides composed of essential amino acids may be more desirable materials for RS-5 preparation. Third, starch-lipid complexes had strong interactions with α-amylase, which provides evidence in support of the sliding continuum hydrolysis hypothesis of α-amylase. These results revealed the mechanism of RS-5 at the molecular level, which provides a reference for the production and research of RS-5.

The role of C18 fatty acids in improving the digestion and retrogradation properties of highland barley starch.

In this study, five C18 fatty acids (FA) with different numbers of double bonds and configurations including stearic acid (SA), oleic acid (OA), elaidic acid (EA), linoleic acid (LA), and α-linolenic acid (ALA), were selected to prepare highland barely starch (HBS)-FA complexes to modulate digestibility and elaborate the underlying mechanism. The results showed that HBS-SA had the highest complex index (34.18 %), relative crystallinity (17.62 %) and single helix content (25.78 %). Furthermore, the HBS-C18 FA complexes were formed by EA (C18 FA with monounsaturated bonds) that had the highest R1047/1022 (1.0509) and lowest full width at half-maximum (FWHM, 20.85), suggesting good short-range ordered structure. Moreover, all C18 FAs could form two kinds of V-type complexes with HBS, which can be confirmed by the results of CLSM and DSC measurements, and all of them showed significantly lower digestibility. HBS-EA possessed the highest resistant starch content (20.17 %), while HBS-SA had the highest slowly digestible starch content (26.61 %). In addition, the inhibition of HBS retrogradation by fatty acid addition was further proven, where HBS-SA gel firmness (37.80 g) and aging enthalpy value were the lowest, indicating the most effective. Overall, compounding with fatty acids, especially SA, could be used as a novel way to make functional foods based on HBS.

Creating a zero amylose barley with high soluble sugar content by genome editing.

Amylose biosynthesis is strictly associated with granule-bound starch synthase I (GBSSI) encoded by the Waxy gene. Mutagenesis of single bases in the Waxy gene, which induced by CRISPR/Cas9 genome editing, caused absence of intact GBSSI protein in grain of the edited line. The amylose and amylopectin contents of waxy mutants were zero and 31.73%, while those in the wild type were 33.50% and 39.00%, respectively. The absence of GBSSI protein led to increase in soluble sugar content to 37.30% compared with only 10.0% in the wild type. Sucrose and ß-glucan, were 39.16% and 35.40% higher in waxy mutants than in the wild type, respectively. Transcriptome analysis identified differences between the wild type and waxy mutants that could partly explain the reduction in amylose and amylopectin contents and the increase in soluble sugar, sucrose and ß-glucan contents. This waxy flour, which showed lower final viscosity and setback, and higher breakdown, could provide more option for food processing.

Effects of Four Highland Barley Proteins on the Pasting Properties and Short-Term Retrogradation of Highland Barley Starch.

This study evaluated the effects of four highland barley proteins (HBPs), namely, albumin, globulin, gliadin and glutenin, on the short-term retrogradation of highland barley starch (HBS). The findings reveal that HBPs could reduce the viscosity, storage modulus and hardness of HBS, with albumin and globulin showing more prominent effects. Furthermore, with the addition of HBPs, the loss tangent (tan δ) of HBS loss increased from 0.07 to 0.10, and the enthalpy of gelatinization decreased from 8.33 to 7.23. The degree of retrogradation (DR%) of HBS was 5.57%, and the DR% decreased by 26.65%, 38.78%, 11.67% and 20.29% with the addition of albumin, globulin, gliadin and glutenin, respectively. Moreover, the relative crystallinity (RC) and the double helix structures were inhibited with the HBPs' incorporation. Meanwhile, the HBPs also could inhibit water migration and improve the structure of HBS gels. In summary, HBPs could inhibit the retrogradation behavior of HBS, which provides new theoretical insights for the production studies of highland barley foods.

Role of pea protein isolate in modulating pea starch digestibility: insights from physicochemical and microstructural analysis.

BACKGROUND: Understanding the interactions between protein and starch is crucial in revealing the mechanisms by which protein influences starch digestibility. The present study investigated the impact of different contents of pea protein isolate (PPI) on the physicochemical properties and digestibility of pea starch (PS). RESULTS: The results demonstrated that as the content of PPI increased from 0% to 12%, and the digestion of PS decreased by 12.3%. Rheological analysis indicated that PPI primarily interacted with molecular chains of PS through hydrogen bonds. Increasing the content of PPI resulted in a 30.6% decrease in the hardness of the composite gels, accompanied by a 10% reduction in the short-ordered structure of PS. This hindered the formation of molecular aggregation and resulted in a loose and disordered gel network structure. The microstructure confirmed that the attachment of PPI to PS served as a physical barrier, impeding starch digestibility. CONCLUSION: In summary, the primary mechanism by which PPI inhibited PS digestion involved steric hindrance exerted by PPI and its interaction with PS via hydrogen bonds. These findings contribute to a better understanding of the interaction mechanisms between PS and PPI and offer insights for the optimal utilization of pea resources. © 2024 Society of Chemical Industry.

Change of physiochemical characteristics, nutritional quality, and volatile compounds of Chenopodium quinoa Willd. during germination.

The impacts of varying germination periods (0-72 h) on morphological properties, proximate composition, amino acid profile, GABA levels, antioxidant attributes, polyphenol content (both free and bound), and volatile compounds of quinoa were evaluated. Germination significantly increased the content of fiber, amino acids, GABA, polyphenols, and in-vitro antioxidant activities in quinoa. The optimal nutritional quality and antioxidant capacity of quinoa were observed during the 36-72 h germination period. We examined the dynamics of 47 phenolic compounds in quinoa during germination and noted a substantial rise in free phenolic acids and bound flavonoids post-germination. A total of 53 and 84 volatile compounds were respectively identified in ungerminated quinoa and germinated quinoa. It was found that the germination period of 24-48 h contributed to reducing the presence of undesirable flavors. TEM analysis revealed significant structural damage to the ultrastructure and relaxation of the cell wall in germinated quinoa grains.

An investigation into the effects of various processing methods on the characteristic compounds of highland barley using a widely targeted metabolomics approach.

This study explored the influence of diverse processing methods (cooking (CO), extrusion puffing (EX), and steam explosion puffing (SE), stir-frying (SF) and fermentation (FE)) on highland barley (Qingke) chemical composition using UHPLC-MS/MS based widely targeted metabolomics. Overall, 827 metabolites were identified and categorized into 16 classes, encompassing secondary metabolites, amino acids, nucleotides, lipids, etc. There 43, 85, 131, 51 and 98 differential metabolites were respectively selected from five comparative groups (raw materials (RM) vs CO/EX/SE/SF/FE), mainly involved in amino acids, nucleotides, flavonoids, and alkaloids. Compared to other treated groups, FE group possessed the higher content of crude protein (15.12 g/100 g DW), and the relative levels of free amino acids (1.32 %), key polyphenols and arachidonic acid (0.01 %). EX group had the higher content of anthocyanins (4.22 mg/100 g DW), and the relative levels of free amino acids (2.02 %) and key polyphenols. SE group showed the higher relative levels of phenolic acids (0.14 %), flavonoids (0.20 %) and alkaloids (1.17 %), but the lowest free amino acids (0.75 %). Different processing methods all decreased Qingke's antioxidant capacity, with the iron reduction capacity (988.93 µmol/100 g DW) in SE group was the lowest. On the whole, FE and EX were alleged in improving Qingke's nutritional value. CO and SF were also suitable for Qingke processing since fewer differential metabolites were identified in CO vs RM and SF vs RM groups. Differential metabolites were connected to 14 metabolic pathways, with alanine, aspartate, and glutamate metabolism being central. This study contributed theoretical groundwork for the scientific processing and quality control of Qingke products.

Deeply analyzing dynamic fermentation of highland barley vinegar: Main physicochemical factors, key flavors, and dominate microorganisms.

Highland barley vinegar, as a solid-state fermentation-type vinegar emerged recently, is well-known in Qinghai-Tibet plateau area of China. This work aimed to explore the main physicochemical factors, key flavor volatile compounds, and dominate microorganisms of highland barley vinegar during fermentation. The results showed that the decrease trend of reducing sugar, pH and the increase trend of amino acid nitrogen were associated with the metabolism of dominate bacteria, especially Lactobacillus and Acetobacter. Totally, 35 volatile compounds mainly including 20 esters, 10 alcohols, 2 aldehydes, 1 ketone and 2 pyrazines and 7 organic acids were identified. Especially, isoamyl acetate, acetyl methyl carbinol, ethyl caprylate, 1,2-propanediol, 3-methyl-1-butanol and ethyl isovalerate with high odor activity values were confirmed as key aroma compounds. Meanwhile, the relative average abundance of bacteria at genus level decreased significantly as fermentation time goes on. Among these microbes, Lactobacillus were the dominate bacteria at alcohol fermentation stage, Lactobacillus and Acetobacter were dominate at acetic acid fermentation stage. Furthermore, the correlations between dominate bacteria and the key volatile compounds were revealed, which highlighted Lactobacillus and Acetobacter were significantly correlated with key volatile compounds (|r| > 0.5, P < 0.01). The fundings of this study provide insights into the flavor and assist to improve the production quality of highland barley vinegar.

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.

Interaction with wheat starch affect the aggregation behavior and digestibility of gluten proteins.

Understanding the interplay between gluten and wheat starch is crucial for elucidating the digestibility mechanism of gluten in wheat-based products. However, this mechanism remains under-investigated. This study sought to elucidate the influence of starch-induced protein structural modifications on gluten digestion. Our findings revealed that starch considerably enhanced gluten digestion. In the presence of starch, gluten protein digestibility increased from 10.91 % (in the control group with a gluten-to-starch ratio of 1:0) to 14.40 % (in the complex with a gluten-to-corn starch ratio of 1:1). The diminished gluten protein digestibility due to starch may be ascribed to modifications in protein configuration and aggregation behavior. Morphological studies suggested that starch not only functioned as filler particles but also diluted the gluten matrix. A protein network assessment further affirmed that both the junction density and branching rate of gluten proteins decreased notably by 29.9 % and 25.1 %, respectively. Conversely, lacunarity increased by 1.92-fold, compromising the cohesiveness and connectivity of the gluten matrix. Elevated starch concentrations suppressed the formation of disulfide bonds, impeding gluten protein aggregation. Concurrently, gluten-starch interactions were governed by hydrogen bonds and hydrophobic associations. In summary, starch augmented gluten protein digestibility by curtailing their polymerization. This revelation might offer novel perspectives on optimizing gluten protein digestion and utilization.

Study on the Changes in Volatile Flavor Compounds in Whole Highland Barley Flour during Accelerated Storage after Different Processing Methods.

The effect of heat processing on the flavor characteristics of highland barley flour (HBF) in storage was revealed by analyzing differences in volatile compounds associated with flavor deterioration in HBF using GC-MS identification and relative odor activity values (ROAVs). Hydrocarbons were the most abundant in untreated and extrusion puffed HBFs, while heterocycles were found to be the most abundant in explosion puffed, baked, and fried HBFs. The major contributors to the deterioration of flavor in different HBFs were hexanal, hexanoic acid, 2-pentylfuran, 1-pentanol, pentanal, 1-octen-3-ol, octanal, 2-butyl-2-octanal, and (E,E)-2,4-decadienal. Amino acid and fatty acid metabolism was ascribed to the main formation pathways of these compounds. Baking slowed down the flavor deterioration in HBF, while extrusion puffing accelerated the flavor deterioration in HBF. The screened key compounds could predict the quality of HBF. This study provides a theoretical basis for the regulation of the flavor quality of barley and its products.

Recent advances in physiochemical changes, nutritional value, bioactivities, and food applications of germinated quinoa: A comprehensive review.

The production and consumption of functional foods has become an essential food industry trend. Due to its high nutritional content, quinoa is regarded as a super pseudocereal for the development of nutritious foods. However, the presence of antinutritional factors and quinoa's distinctive grassy flavor limit its food applications. Due to its benefits in enhancing the nutritional bioavailability and organoleptic quality of quinoa, germination has garnered significant interest. To date, there is no systematic review of quinoa germination and the health benefits of germinated quinoa. This review details the nutritional components and bioactivities of germinated quinoa, as well as the potential mechanisms for the accumulation of bioactive compounds during the germination process. Additionally, evidence supporting the health benefits of germinated quinoa, the current status of related product development, and perspectives for future research are presented. Thus, our research is likely to provide theoretical support for the use of germinated quinoa resources.

Enhancement of Polyphenols and Antioxidant Activity in Germinated Black Highland Barley by Ultrasonication.

The aim of this study was to investigate the effect of ultrasonic stress germination (USG) on total phenolic contents (TPC), total flavonoid contents (TFC), the phenolic compositions, and antioxidant activities of black highland barley (BHB). The USG processing parameters, polyphenol profile, phenolic compositions, and antioxidant activities were explored after USG. Results showed that the optimal USG parameters were as follows: 350 W ultrasonic pretreatment power, 30 °C ultrasonication temperature, 25 min ultrasonication time, and 64 h germination time. Under these conditions, the total phenolic content (688.84 ± 5.30 mg/100 g) and total flavonoid content (59.23 ± 0.45 mg/100 g) of BHB were increased by 28.55% and 10.15%, respectively, compared to the untreated samples. In addition, the USG treatment could more effectively enrich bound phenolic acids and free flavonoids, among which the content of catechin was significantly increased by USG and was the main characteristic substance. Moreover, the USG treatment could improve the antioxidant activity and had a higher antioxidant potency composite index (APC index) (97.91%) of BHB. These results indicate that USG might be an effective method to enrich polyphenols and improve antioxidant activity in BHB.

Effect of fiber-bound polyphenols from highland barley on lipid oxidation products of cooked pork during in vitro gastrointestinal digestion.

BACKGROUND: The gastrointestinal (GI) tract is a major site of lipid oxidation, and the lipid oxidation products are related to an increased risk of various chronic diseases. In this study, the inhibition capacity of bound-polyphenol rich insoluble dietary fiber (BP-IDF) from highland barley (HB) to lipid oxidation was evaluated during simulated GI digestion. RESULTS: We found that the level of lipid hydroperoxides (LOOH) and aldehydes were significantly inhibited when highland barley bound-polyphenol rich insoluble dietary fiber (HBBP-IDF) co-digestion with cooked pork. The lipid oxidation products were more effectively scavenged during simulated gastric digestion, with inhibition of 77.4% for LOOH, 52.3% for malondialdehyde, 46.5% for 4-hydroxy-2-hexenal and 48.7% for 4-hydroxy-2-nonenel, respectively. The fiber-bound polyphenols are the principal scavengers of lipid oxidation products. CONCLUSION: These findings suggest that HBBP-IDF could be used as a functional ingredient able to scavenge lipid oxidation products across the GI tract. © 2023 Society of Chemical Industry.

Polyphenol Profile and In Vitro Antioxidant and Enzyme Inhibitory Activities of Different Solvent Extracts of Highland Barley Bran.

Five different solvent extracts of highland barley bran were analyzed and compared for their polyphenol profile, antioxidant activity, and α-glucosidase and α-amylase inhibitory activities. The highland barley bran acetone extract had the highest total phenolic content, total flavonoid content, and antioxidant capacity. It was followed by the methanol and ethanol extracts, while n-butanol and ethyl acetate extracts exhibited lower measured values. Diosmetin, luteolin, protocatechuic acid, vanillic acid, ferulic acid, phlorogucinol, diosmin, isoquercitrin, catechin, and isovitexin were among the most abundant phenolic compounds identified in different solvent extracts, and their concentrations varied according to the solvent used. The highest α-glucosidase and α-amylase inhibitory activity were observed in the ethyl acetate extract of highland barley bran, followed by the acetone and methanol extracts. In contrast, n-butanol and ethanol extracts exhibited lower measured values. The different solvent extracts were effective inhibitors for α-glucosidase and α-amylase with activity reaching to 34.45-94.32% and 22.08-35.92% of that of positive control acarbose, respectively. There were obvious correlations between the phenolic content and composition of different solvent extracts and their in vitro antioxidant activity, α-glucosidase inhibition activity and α-amylase inhibition activity. Black barley bran is an excellent natural raw material for developing polyphenol-rich functional foods and shows good antioxidant and hypoglycemic potential to benefit human health.

Impacts of Proanthocyanidin Binding on Conformational and Functional Properties of Decolorized Highland Barley Protein.

The impacts of interaction between proanthocyanidin (PC) and decolorized highland barley protein (DHBP) at pH 7 and 9 on the functional and conformational changes in DHBP were investigated. It was shown that PC strongly quenched the intrinsic fluorescence of DHBP primarily through static quenching. PC and DHBP were mainly bound by hydrophobic interactions. Additionally, free sulfhydryl groups and surface hydrophobicity obviously decreased in DHBP after combining with PC. The zeta potential of DHBP-PC complexes at pH 7 increased significantly. A change in the structure of DHBP was caused by interactions with PC, resulting in an increase in the number of ß-sheets, a decrease in the number of α-helixes, and a spectral shift in the amide Ⅱ band. Furthermore, the presence of PC enhanced the foaming properties and antioxidant activity of DHBP. Overall, this study suggests that DHBP-PC complexes at pH 7 could be designed as a stable additive, and illustrates the potential applications of DHBP-PC complexes in the food industry.

Effect of Thermal Treatment on the Internal Structure, Physicochemical Properties and Storage Stability of Whole Grain Highland Barley Flour.

In this study, to improve the processing performance of whole grain highland barley flour (whole grain HB flour), they were prepared by sand-roasting, far-infrared baking, steam explosion, and extrusion, and the effects of on functional properties and storage characteristics were measured. The results indicated that sand-roasting, far-infrared baking, and steam explosion all caused cracks and honeycomb structures in the outer layer and endosperm of the highland barley. The XRD analysis results indicated that highland barley starch treated by far-infrared baking exhibited typical A-type crystal structure, while sand-roasting, steam explosion, and extrusion presented the typical V-type. The results of DSC analysis revealed that the onset temperature (To), peak temperature (Tp), gelatinization enthalpy (ΔH), peak viscosity (PV), trough viscosity (TV), and final viscosity (FV) decreased significantly, while the swelling power, water-holding capacity and oil-holding capacity increased significantly. During the storage period, the moisture content and lipase activity of the whole grain HB flour after thermal treatment remained at a low level; the fatty acid value, peroxide value, and malondialdehyde value increased; finally, the cooked whole grain HB flour was unstable during storage. The functional properties of whole grain HB flour can be improved by steam explosion, and will then have better storage stability.

Evaluation of Nutritional Components, Phenolic Composition, and Antioxidant Capacity of Highland Barley with Different Grain Colors on the Qinghai Tibet Plateau.

The nutritional composition, polyphenol and anthocyanin composition, and antioxidant capacity of 52 colored highland barley were evaluated. The results showed that the protein content of highland barley in the black group was the highest, the total starch and fat contents in the blue group were the highest, the amylose content in the purple group was quite high, the fiber content in the yellow group was quite high, and the ß-glucan content of the dark highland barley (purple, blue and black) was quite high. The polyphenol content and its antioxidant capacity in the black group were the highest, while the anthocyanin content and its antioxidant capacity in the purple highland barley were the highest. Ten types of monomeric phenolic substances were the main contributors to DPPH, ABTS, and FRAP antioxidant capacity. All varieties could be divided into four categories according to nutrition or function. The grain color could not be used as an absolute index to evaluate the quality of highland barley, and the important influence of variety on the quality of highland barley also needed to be considered. In actual production, suitable raw materials must be selected according to the processing purpose and variety characteristics of highland barley.

Trapping of reactive carbonyl species by fiber-bound polyphenols from whole grains under simulated physiological conditions.

The carbonyl trapping activity of bound-polyphenol rich insoluble dietary fiber (BP-IDF) from different whole grains and underlying mechanism of these BP-IDF actions were studied under simulated physiological conditions. We found that the black highland barley BP-IDF exhibited the most pronounced effect in scavenging carbonyls by trapping 88.7%, 72.2%, 95.7%, and 31.4% for methylglyoxal, glyoxal, acrolein, and malondialdehyde within 24 h, respectively. After vitro gastrointestinal digestion, the black highland barley BP-IDF still retained considerable trapping activity for carbonyls. The carbonyl scavenging capacity was reduced by up to 93% after removing bound polyphenols from the black highland barley BP-IDF, which was consistent with the reduction in its total phenolic content. Moreover, the formation of adducts between reactive carbonyl species (RCS) and polyphenols bound to insoluble dietary fiber (IDF) was also detected. Overall, these findings confirmed that IDF-bound polyphenols were still active to trap RCS, indicating the potential benefits of BP-IDF from whole grains as functional ingredients to limit carbonyl stress across the gastrointestinal tract.