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

The mechanisms of thermal processing techniques on modifying structural, functional and flour-processing properties of whole-grain highland barley

The mechanisms underlying three thermal processing methods, namely hot-air drying, microwave irradiation, and heat fluidization, were systematically investigated to evaluate their effects on the structural, functional, and flour-processing properties of whole-grain highland barley. Starch granules were partially damaged when treated with hot-air drying and microwave irradiation. However, these granules were predominantly aggregated or encapsulated in proteins following heat fluidization. Accordingly, flour produced through heat fluidization exhibited the lowest relative crystallinity of 3.43 % and the greatest α → β shifts in secondary protein structures, compared to other treatments. These structural changes led to improved water/oil holding capacity, enhanced elastic property, reduced enthalpy of 4430 J/kg and breakdown viscosity of 0.24 Pa·s. Moreover, fresh noodles made from heat fluidization-treated highland barley exhibited superior textural features. Overall, heat fluidization could be a more effective method to modify the flour-processing properties of whole highland barley flour and enhance its applicability in the food industry.

Drying methods affected the fatty acids oxidation and bacterial community of traditional dry-cured ducks during processing and its relation with the aroma formation

The formation of volatile compounds in dry-cured ducks produced by hot and cold air circular drying (HCAD), hot air drying (HAD), and traditional sun drying (TSD) were analyzed by E-nose and GC-MS. The HCAD exhibited higher alcohols, aldehydes, esters, and furans than that of the other two. Six, five, and three key compounds were identified by OAV in HCAD, HAD, and TSD, respectively. Nonanal was the highest relative content of aldehydes in all groups. (E)-2-octenal was detected only in HCAD. HAD accelerated the oxidation of fatty acids. The POV and AV of HAD were 0.24 g/100 g and 2.02 mg/g when stored for 15 days, which were higher than that of HCAD and TSD. Proteobacteria, Actinobacteriota and Firmicutes were the most abundant phylum, Psychrobacter, Kocuria, and Macrococcus were the primary dominant genus. The hightest abundance of Firmicutes and Macrococcus in the HCAD-15d might contribute to the aroma formation. HCAD showed a better quality and flavor than TSD and HAD, indicating it is an innovative method for producing dry-cured duck.

The bioaccessibility and bioactivity of polyphenols from tsampa prepared from roasted highland barley flour solid-fermented by autochthonous lactic acid bacteria

Tsampa, which is abundant in polyphenols, demonstrates significant bioactivity and potential health benefit. However, the bioaccessibility and potential bioactivity of polyphenols derived from tsampa prepared from autochthonous lactic acid bacteria solid-fermented roasted highland barley flour (F-RHBF) have not been investigated. This study aimed to evaluate the bioaccessibility and bioactivity of polyphenols from tsampa prepared from F-RHBF through in vitro digestion model, and additionally, to explore the protective effects of digested tsampa extract against oxidative stress damage by establishing H2O2 -induced oxidative stress injury model of HepG2 cells. The results indicated that tsampa prepared from F-RHBF exhibited excellent bioaccessibility and bioactivity of polyphenols, including antioxidant and digestive enzymes inhibitory activity, compared to tsampa prepared from unfermented RHBF (UF-RHBF). Furthermore, the digested extract of tsampa prepared from F-RHBF was more effective in protecting HepG2 cells from oxidative damage by reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA), while enhancing the activity of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity (T-AOC). These findings suggested that fermentation and in vitro digestion can improve the bioaccessibility and bioactivity of polyphenols from tsampa. Present findings pave the way toward applying fermented highland barley flour to design tsampa and novel functional foods.

Flaking of millets and its impact on bioactivity, pasting, digestibility, structural and thermal properties

Five different millets (foxtail, little, barnyard, kodo and browntop) with and without sprouting were subjected to flaking. Phytic acid and phenolic content tends to decrease significantly, whereas antioxidant activity increased up to 77.32% on flaking of millets. A significant decrease in peak and final viscosity was observed in millet flakes. A-type diffraction pattern was predominant for unsprouted millets whereas the flaked millets showed V-type crystallinity. The protein digestibility significantly increased up to 37.77% in flakes made from sprouted millets. The mineral bioavailability upon flaking of millets increased, especially Ca (88.22% for little), Fe (43.04% for barnyard) and Zn (61.77% for kodo), which is attributed to the reduction in phytic acid. Flaking, however, led to an increase in rapidly and slowly digestible starch with a corresponding decrease in resistant starch. Among the unsprouted and sprouted millet flakes, foxtail received the highest sensory scores for overall acceptability.

Impact of whole grain highland hull-less barley on the denaturing gradient gel electrophoresis profiles of gut microbial communities in rats fed high-fat diets

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) is a traditional non-culture technique that can provide a fingerprint of the microbial community. In the field of gut microbiota analysis, PCR-DGGE still holds potential for development. In the present study, we utilized an improved nested PCR-DGGE approach targeting the V3 region of 16S ribosomal DNA to investigate the impact of whole grain highland hull-less barley (WHLB), a cereal known for its significant hypocholesterolemic effect, on the gut microbiota profiles of high-fat diet rats. Seventy-two male Sprague-Dawley rats were divided into four groups and fed a normal control diet, a high-fat diet, or a high-fat diet supplemented with a low or high dose of WHLB for 4 or 8 weeks. The results revealed that the dominant bands varied among different dose groups and further changed with different treatment times. The compositions of bacterial communities in feces and cecal content were similar, but the dominant bacterial bands differed. After performing double DGGE, extracting the bands, sequencing the DNA, and aligning the sequences, a total of 19 bands were classified under the Firmicutes and Bacteroidetes phyla, while two bands were identified as unclassified uncultured bacteria. The relative abundance of Lactobacillus gasseri, Uncultured Prevotella sp., and Clostridium sp. increased following the administration of WHLB. Illumina-based sequencing was employed to assess the reliability of DGGE, demonstrating its reliability in analyzing the dominant taxonomic composition, although it may have limitations in accurately detecting the alpha diversity of bacterial species.

IMPORTANCE

While next-generation sequencing has overshadowed polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), the latter still holds promise for advancing gut microbiota analysis due to its unique advantages. In this study, we used optimized nested PCR-DGGE to investigate the gut microbiota profile of high-fat diet rats after administering whole grain highland hull-less barley. High-throughput sequencing was employed to validate the DGGE results. Our results proved the reliability of PCR-DGGE for analyzing the dominant taxonomic composition while also providing visual evidence of a notable relationship between the composition of cecal and fecal microbial communities, highlighting substantial differences in both richness and abundance.

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.

Application of emerging thermal and nonthermal technologies for improving textural properties of food grains: A critical review

Emerging nonthermal and thermal food processing technologies are a better alternative to conventional thermal processing techniques because they offer high-quality, minimally processed food. Texture is important in the food industry because it encompasses several product attributes and plays a vital role in consumer acceptance. Therefore, it is imperative to analyze the extent to which these technologies influence the textural attributes of food grains. Physical forces produced by cavitation are attributed to ultrasound treatment-induced changes in the conformational and structural properties of food proteins. Pulsed electric field treatment causes polarization of starch granules, damaging the dense outer layer of starch granules and decreasing the mechanical strength of starch. Prolonged radio frequency heating results in the denaturation of proteins and gelatinization of starch, thus reducing binding tendency during cooking. Microwave energy induces rapid removal of water from the product surface, resulting in lower bulk density, low shrinkage, and a porous structure. However, evaluating the influence of these techniques on food grain texture is difficult owing to differences in their primary operation mode, operating conditions, and equipment design. To maximize the advantages of nonthermal and thermal technologies, in-depth research should be conducted on their effects on the textural properties of different food grains while ensuring the selection of appropriate operating conditions for each food grain type. This article summarizes all recent developments in these emerging processing technologies for food grains, discusses their potential applications and drawbacks, and presents prospects for future developments in food texture enhancement.

Heat-moisture treatment enhances the ordered degree of starch structure in whole chestnut flour and alters its gut microbiota modulation in mice fed with high-fat diet

Currently, chestnuts attract more attention among consumers due to its rich nutritional functions, but systematic evaluation on the effect of thermal processing on its nutritional value is still limited. In this work, based on results of microstructural properties that heat-moisture treatment (HMT) could enhance the total ordered degree of starch structure in whole chestnut flour (CN) and promote the formation of anti-enzymatic component, in vitro experiment was then conducted and confirmed that HMT could significantly reduce the predicted glycemic index (pGI) of CN from 75.6 to 64.3 and improve its dietary fiber content from 7.06 to 13.42 g/100 g (p < 0.05). Further dietary intervention studies with CN and heat-moisture treated CN (HMT-CN) supplementation on the high-fat diet (HFD) consuming mice were discussed in terms of gut microbiota and its metabolites changes. The results showed that both CN and HMT-CN significantly resisted the weight gain induced by HFD, while HMT-CN had better serum lipid regulation effect. However, they had different effects on the gut metabolism pathways, among which CN inhibited the production of stearamine by promoting the proliferation of Dubosiella, while HMT-CN contributed to the growth of Lachnoclostridium, Desulfovibrio, and Faecalibaculum which stimulated the formation of associated metabolites including jwh-018-d11, valylproline, tetranor-12(S)-HETE, and PA (3:0/18:0). Overall, these discoveries could provide basic data for the effective utilization of CN in food industry processing.

New Technologies in Cereal Processing and Their Impact on the Physical Properties of Cereal Foods

Cereal is a general term for cereal plants or food crops, covering a wide range of foods, including rice, wheat, millet, corn and other miscellaneous grains, and representiing the most important component of the human diet [...].

The Effect of Different Milling Methods on the Physicochemical and In Vitro Digestibility of Rice Flour

Preparation methods have been found to affect the physical and chemical properties of rice. This study prepared Guichao rice flour with wet, dry, semi-dry, and jet milling techniques. Differences in the particle size distribution of rice flour were investigated in order to assess their impact on pasting, thermal, gel, starch digestibility, and crystalline structure using an X-ray diffractometer (XRD) and a Rapid Visco Analyzer (RVA) across in vitro digestibility experiments. The results showed that semi-dry-milled rice flour (SRF) and wet-milled rice flour (WRF) were similar in damaged starch content, crystalline structure, and gelatinization temperature. However, compared with dry-milled rice flour (DRF) and jet-milled rice flour (JRF), SRF had less damaged starch, a higher absorption enthalpy value, and a higher gelatinization temperature. For starch digestibility, the extended glycemic index (eGI) values of WRF (85.30) and SRF (89.97) were significantly lower than those of DRF (94.47) and JRF (99.27). In general, the physicochemical properties and starch digestibility of WRF and SRF were better than those of DRF and JRF. SRF retained the advantages of WRF while avoiding the high energy consumption, high water consumption, and microbial contamination disadvantages of WRF and was able to produce better rice flour-associated products.

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.

Lipase Inactivation Kinetics of Tef Flour with Microwave Radiation and Impact on the Rheological Properties of the Gels Made from Treated Flour

In recent years, many efforts are being made to produce tef-based food for its nutritive and health-promoting advantages. Tef grain is always whole milled because of its tiny grain size and whole flours contain bran (pericarp, aleurone, and germ) where major non-starch lipids could be deposited along with the lipid-degrading enzymes: lipase and lipoxygenase. As lipoxygenase shows little activity in low moisture, the inactivation of lipase is the common objective for most heat treatments to extend the shelf life of flours. In this study, tef flour lipase inactivation kinetics via hydrothermal treatments assisted using microwaves (MW) were studied. The effects of tef flour moisture level (12%, 15%, 20%, and 25%) and MW treatment time (1, 2, 4, 6, and 8 min) on flour lipase activity (LA) and free fatty acid (FFA) content were evaluated. The effects of MW treatment on flour pasting characteristics and the rheological properties of gels prepared from the treated flours were also explored. The inactivation process followed a first-order kinetic response and the apparent rate constant of thermal inactivation increased exponentially with the moisture content of the flour (M) according to the equation 0.048·exp (0.073·M) (R² = 0.97). The LA of the flours decreased up to 90% under the studied conditions. MW treatment also significantly reduced (up to 20%) the FFA level in the flours. The rheological study confirmed the presence of significant modifications induced by the treatment, as a lateral effect of the flour stabilization process.

Enzyme inactivation induced by thermal stabilization in highland barley and impact on lipid oxidation and aroma profiles

Thermal stabilization is efficient for slowing lipid degradation and prolonging the shelf life of highland barley, but the impacts of different thermal stabilized treatments on highland barley and possible chemical reactions remain unclear. The effects of thermal stabilization treatments (bake, far-infrared, fry, microwave and steam) on the enzymes, lipids and aroma profiles of highland barley flour (HBF) were investigated in this study. Thermal stabilization significantly decreased the contents of ash and GABA. Baked HBF exhibited the lowest fatty acid value and peroxide value. Untreated HBF had higher lipase and lipoxygenase activities and fried mostly inactivated these enzymes. All thermal stabilization treatments increased the catalase activities and fried showed the higher level. Thus, fried might be an effective method to stabilize the HBF. The high temperatures during stabilizing triggered the complex reactions, leading to the loss of some volatile compounds, and in the meantime the formation of others such as furans and aldehydes. These productions contributed to the unique aroma profiles of different HBFs. Furthermore, a chemometric approach was used to analyze the changes of thermal stabilized treated HBFs and to identity six key volatile compounds, which provided important knowledge on possible chemical reactions caused by thermal stabilization. Overall, these results provide the theoretical basis for the wider application of thermal stabilization technologies in highland barley processing.

The Flavor Profiles of Highland Barley Fermented with Different Mushroom Mycelium

Highland barley was fermented with Cordyceps militaris, Stropharia rugoso-annulata, Morchella esculenta, Schizophyllum commune and Tremella sanguinea. The flavor profiles were investigated by electronic nose (E-nose), headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and sensory evaluation by train panel. Fermentation with mushroom mycelium was able to change the aroma profile of highland barley. The original strong grassy taste was reduced due to a decrease in hexanal, decanal and 2-pentylfuran, and new aromatic flavors (floral, sweet and mushroom fragrance) were acquired after fermentation. The overall flavor of the fermented highland barley varied with mushroom strains. Schizophyllum commune gave a heavier sour taste to the fermented highland barley. However, fermentation with T. sanguinea increased the content of methyl 4-methoxybenzoate making the sample difficult to accepted. Fermentation with C. militaris, M. esculenta, and S. rugoso-annulata increased the volatile contents. The high levels of 1-octen-3-ol and esters gave a strong mushroom, oily and fruity flavor. Morchella esculenta showed the best performance and the highest acceptance in the fermented highland barley. Our results suggest that fermentation with mushroom mycelium can improve the flavor of highland barley, which provides an innovative utilization of highland barley.

Physical properties, antioxidant capacity, and starch digestibility of cookies enriched with steam-exploded wheat bran

Wheat bran-based food is rich in bioactive compounds, and steam explosion enhances the nutritional properties of wheat bran. This study examined the potential utilization of steam-exploded wheat bran (SWB) in cookie formulation. The influence of steam explosion on the chemical compounds in wheat bran and the effects of SWB on the physical properties, antioxidant capacity, and starch digestibility of cookies were investigated. The results showed that steam explosion facilitated the release of reducing sugar, flavonoids, phenolic substances, and amino acid nitrogen in wheat bran, thereby improving its nutritional properties. The reduction of sugar, total flavonoids, total phenolics, and amino acid nitrogen contents of wheat bran after steam explosion increased by 34.22, 183.02, 284.09, and 93.39%, respectively, compared with those of native wheat bran. Substitution of SWB for wheat flour mainly induced higher water, sodium carbonate, and sucrose solvent retention capacities, which were positively related to the spread ratio and hardness of cookies. The cookies with more SWB substitution (30-50%) expressed a higher spread ratio and harder texture than the others. The substitution of SWB caused changes in the antioxidant properties of cookies, which were related to the phenolic content. The cookies with SWB showed a higher DPPH radical scavenging activity (16.30-30.93%) than that of the control (14.74%). SWB might form a matrix barrier to hinder starch digestion, thus reducing the digestibility of cookies. The cookies enriched with 30-50% of the SWB exhibited greater physical properties and antioxidant capacity but lower starch digestibility than those of other cookies. The results will contribute to expanding the application range and improving the quality of bran-rich flour products.