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Pea starch was pre-cooked before being subjected to different drying treatments including oven-drying, infrared-drying, microwave-drying and freeze-drying. Different dried pea starch samples were then anaerobically fermented by human gut microbiota. Their structural features, morphological changes, the synthesis of short-chain fatty acids, as well as the microbiological responses during the 24 h in vitro human fecal fermentation were determined. Oven-dried pea starch (ODPS) displayed relatively stronger fluorescence intensity on the confocal laser scanning microscopic images, which was in qualitative agreement with its significantly highest crystallinities obtained from X-ray diffractogram (XRD) and 13 C cross-polarization magic angle spinning ( 13 C CP/MAS) NMR. The obtained results demonstrated that the significant differences in structural and morphological features observed for these four dried starch samples originate from different evaporation patterns of water molecules. Changes in R 1047/1022 and R 995/1022 C CP/MAS NMR measurements, suggesting an increase in the molecular order upon starch utilization by the gut bacteria. The correlation analysis indicated that the dried starch with higher degree of short-range ordered structure was beneficial for the growth of Firmicutes, whereas starch substrate with a relatively loose granular structure would be beneficial for the growth of Bacteroides. The significantly highest operational taxonomic unit level of in vitro species after the fermentation of ODPS corresponded well with its highest propionate and butyrate concentration. The results obtained are expected to help food processors to tailor the drying method during the manufacture of processed starch samples with desirable structural features and prebiotic properties.13 C CP/MAS NMR measurements, suggesting an increase in the molecular order upon starch utilization by the gut bacteria. The correlation analysis indicated that the dried starch with higher degree of short-range ordered structure was beneficial for the growth of Firmicutes, whereas starch substrate with a relatively loose granular structure would be beneficial for the growth of Bacteroides. The significantly highest operational taxonomic unit level of Bifidobacterium species after the fermentation of ODPS corresponded well with its highest propionate and butyrate concentration. The results obtained are expected to help food processors to tailor the drying method during the manufacture of processed starch samples with desirable structural features and prebiotic properties.

Different treatments of autoclaving, pullulanase debranching and/or ultrasound were applied to prepare debranched lentil starch (DBLS). Their fine structures can affect the retrogradation patterns of DBLSs, which consequently could affect their potential use as delivery carrier of sensitive bioactive compounds. An attempt was made to use these DBLSs as wall materials to encapsulate rutin, aiming to improve the bioaccessibility, meanwhile to enhance the aqueous solubility and stability of rutin molecules. Their encapsulation efficiency, structural characteristics, thermal stability, morphological features, antioxidant activity and in vitro release behavior under simulated upper gastrointestinal tract environment were evaluated. The results suggested that rutin was dispersed in the DBLS polymer matrix, showing the amorphous nature that further authenticates the encapsulation and entrapment of rutin. The structural analyses of microparticles revealed that rutin could interacted with DBLS biopolymer chains by hydrogen bonds, making the starch molecular chains less susceptible to interact with themselves for reordering. The encapsulation efficiency was found to be in an opposite trend with those values obtained for relative crystallinity, melting enthalpy, degree of order/double helices of DBLS wall materials before encapsulation. The release rate results indicated that DBLS carrier with lower M w , DP n and higher molecular order was beneficial for the slower release of rutin encapsulated in the microparticles., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This work investigated the changes in multi-scale structure and retrogradation properties of native wheat starches (NS) modified by sodium alginate (AG) with and without fermentation. AG adhered on the surface of NS granules and fermentation promoted the adhesions. Compared with the addition of AG alone, dual modification by fermentation and AG together showed a greater effect to increase the weight-average molecular weight and reduce the relative crystallinity and double helix degree of NS. Small angle X-ray diffraction results showed a significant increase in amorphous region with dual modification compared with AG alone. Additionally, dual modification greatly slowed the increase of relative crystallinity and the enthalpy (ΔH) of NS paste during storage. The results of this study suggest that dual modification is a more effective approach to modify structures and properties of wheat starch than single AG treatment, and suggest its potential industrial application in starch-based foods., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Oat rice kernels were subjected to decortication (DOR), decortication and enzyme deactivation (DDOR), decortication and cooking (DCOR), as well as combined decortication, enzyme deactivation and cooking (DDCOR). The starch fractions were isolated and their structural features were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, solid-state 13 C nuclear magnetic resonance, small angle X-ray scattering (SAXS), and scanning electron microscope. In the cooked oat rice samples (DCOR and DDCOR), in addition to losing a significant amount of the A-type crystalline structure, there was an enhancement in the proportion of V-type crystallinity. The cooking process completely destroyed the periodic lamellar structure of oat starch on the SAXS profile. The M w values (1.195 × 10 7 -1.459 × 10 7 g/mol) were in the following order: DOR > DDOR > DCOR > DDCOR. The data was in line with the results for crystallinity, double helix content, degree of order, melting enthalpy, and those obtained for textural parameters, resistant starch content, and bile acid binding capacity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The anti-obesity effects of two categories of resistant starch (RS) including RS 2 (isolated from untreated lentil starch, URS) and RS 3 (isolated from autoclaved and retrograded lentil starch, ARS) on mice with high-fat (HF) diet-induced obesity and the supramolecular structure-in vivo physiological functionality relationship of RS were investigated. Following 6 consecutive weeks, the obese mice in the two RS administered groups displayed suppression of body/liver weight gain and an improvement in serum glucose/lipid profile, antioxidant status, and gut microbiota structure. Compared with the URS intervention group, the ARS administration resulted in a more pronounced effect in controlling body weight, together with a more prominent reduction in blood glucose and triglyceride concentration, as well as a significant increase in the HDL-c level in obese mice. The ARS group also showed an absolute advantage over URS in suppressing the oxidative stress and regulating the liver function induced by the HF diet. Simultaneously, the administration of URS and ARS efficiently suppressed the HF-diet induced alterations in gut microbial ecology, with an obviously decreased ratio of Firmicutes to Bacteroidetes, especially for the ARS group, suggesting its beneficial role in gastrointestinal tract health. The structural characterization results revealed that ARS and URS differed significantly in their supramolecular structural characteristics, where ARS exhibited a higher proportion of crystallinity and double helix content with an X-ray diffraction pattern of a C B type crystal polymorph and a low proportion of molecular inhomogeneity. This study suggested that the difference in the anti-obesity effect of resistant starches was a consequence of the diversity in their structural features.

Resistant starch (RS) plays a key role in providing metabolic and colonic health benefits. In particular, RS type III (RS 3 ) is of great interest because of its thermal stability and its preserved nutritional functionality. RS 3 can be prepared by physical treatment, including high hydrostatic pressure, ultrasound, extrusion, autoclaving, microwave cooking, and heat-moisture treatment. The acid and enzymatic hydrolysis can also be applied to facilitate the generation of small molecules, which increases the inherent crystallinity of RS 3 upon retrogradation. Depending on processing conditions, RS 3 with diversified structural characteristics can be formed. These structures play a key role in determining the physiological behavior of RS 3 . Therefore, a deep understanding of the structural rearrangement pattern during different processing treatment is of great importance for regulating the molecular structure of RS 3 and thereby its corresponding physiological properties. This review thus focuses on the past and current status of research into the in-depth study of RS 3 formation mechanism and the changes to RS 3 structural characteristics under different processing conditions. The objective was to provide a theoretical guidance for the rational selection of preparation methods for RS 3 and for designing RS 3 structures with specific physiological functionalities for relevant industrial applications.

This study aimed to isolate starch from three types of untreated and autoclaved pulse seeds including chickpea, navy bean, and yellow field pea and to characterize their multi-scale structure and the associated physicochemical properties. Autoclaving of pulse seeds tended to significantly decrease the relative crystallinity, the M w value, and degree of order of starch samples measured by X-ray diffraction, size exclusion chromatography, and FT-IR. Simultaneously, double helix content, and degree of double helix obtained from solid-state 13 CNMR and FT-IR were relatively higher (P < 0.05) for autoclaved pulse seeds than their native counterparts. The structural characteristics also corroborated well with the obtained results of resistant starch content, gelatinization behavior, swelling power, solubility, and bile acid binding capacity. This research gave insights into the structural characteristics of starch from pulses and their changes that occurred following processing of seeds, aiming to provide information for the future study on their processing-structure-function relationship., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The structural changes and retrogradation behavior of the processed pea starch stored at 4 °C and 25 °C for different length of time (6, 12, 24, 48, and 72 h) was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), solid-state 13 C nuclear magnetic resonance spectroscopy ( 13 CNMR), Fourier transform infrared spectroscopy (FT-IR), and small angle X-ray scattering (SAXS), their corresponded physicochemical properties were studied by rapid visco-analyzer (RVA). A mixture of B- and V-type crystalline polymorph was observed by XRD for all processed and retrograded pea starch. A continuous increase in the following parameters was observed during the initial retrogradation of pea starch for 6-48 h at 4 °C and for 6-24 h at 25 °C, followed by a decreased trend during the subsequent storage time from 48 h to 72 h at 4 °C, and from 24 h to 72 h at 25 °C, including the values of relative crystallinity, degree of order, and degree of double helix measured by XRD, 13 CNMR, and FT-IR, respectively. The results of this study would provide useful information for better designing of starch-based food ingredients with improved functional and health benefits., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Pea starch (S) was modified by autoclaving (A), α-amylolysis (E), and pullulanase debranching (P), the effect of pretreatments including autoclaving and α-amylolysis on the structural modifications to the pullulanase debranched starch was investigated. All processed pea starch was transformed from a C- to a B-type crystalline structure. The power law exponent (α) ranging from 1.85 to 2.64 suggested the existence of mass fractal structure. Compared with native starch, all treatments applied caused an enhanced short-range order which was reflected by the increased values of α, degree of double helix (DD), degree of order (DO), and double helix content based on SAXS, FTIR, and 13 CNMR observations. The processed starch sample of AS, and APS exhibited the highest DO, and α values, as well as the stronger absorption peak between 3000 and 3695 cm -1 on FT-IR spectrum. AEPS exhibited the significantly highest double helix content, indicating that the higher extent of degradation induced by the combined treatments of autoclaving, α-amylolysis, and pullulanase debranching would give the molecular chains a higher alignment opportunity for the evolution towards coil-to-helix transition. The results would be helpful for better understanding the structure-processing relationship and to provide theoretical foundation for the development of food ingredients with targeted functional properties., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This work focused on the structural characterization of resistant starch from untreated (UL-RS), germinated (GL-RS), fermented (FL-RS), microwaved (ML-RS), conventionally cooked (CL-RS), and autoclaved (AL-RS) lentil seeds. The size exclusion chromatography (SEC) results showed that UL-RS, RL-RS, and GL-RS (Group A samples) exhibited higher values of M w and R h ¯ than FL-RS, ML-RS, AL-RS (Group C samples), and CL-RS (Group B sample). In parallel with the SEC result, other structural characteristics followed similar trends, where Group C samples exhibited the lowest values of double helix content and crystallinity by 13 C NMR, and degree of order/double helix by FT-IR. Comparatively, Group A samples exhibited the opposite trends, and displayed large amorphous aggregates on their micrograph. The results are expected to provide information for better understanding the mechanism of resistant starch formation during different processing of lentil and to lay a theoretical foundation for the future study of their structure-function relationship., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Resistant starch (RS) is defined as the fraction of starch that escapes digestion in the small intestine due to either difficult enzyme/starch contact or to the strength of the crystalline regions formed both in native starch and in those retrograded starch. RS occurs naturally in some foods, and some may be generated in others as the results of several processing conditions. Varieties of techniques have been employed to obtain structural characteristics of RS such as their crystallinity, structural order, chain-length distribution and conformation, helicity, and double-helical structures. These structures play an important role in determining the physiological properties of RS such as their prebiotic and hypoglycaemic properties. However, such topic on structural characterization of RS and their structure-physiological function relationship have not been reviewed in previous literatures. Therefore, this review focuses on the past and current achievements of research on structural characterizations of a range of RS prepared from different sources of native starches as a result of a variety of processing conditions. The potential relationships between the structure and the physiological properties of RS, which is of paramount importance for the furtherance understanding and application of RS, are also reviewed in this study.

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 (DPn). 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 DPn value obtained for PC-EHSC indicated that the starch polymers modified by pancreatin could produce glucan chains with a comparatively homogenous Mw 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. [ABSTRACT FROM AUTHOR]

This study examined the effect of calcium hydroxide (Ca(OH)2, 0.6%, w/w) on structural, physicochemical and in vitro digestibility properties of the complexed system of Tartary buckwheat starch (TBS) and rutin (10%, w/w). The pre-gelatinization and co-gelatinization methods were also compared. SEM results showed that the presence of Ca(OH)2 promoted the connection and further strengthened the pore wall of the three-dimensional network structure of the gelatinized and retrograded TBS-rutin complex, indicating the complex possessed a more stable structure with the presence of Ca(OH)2, which were also confirmed by the results of textural analysis and TGA. Additionally, Ca(OH)2 reduced relative crystallinity (RC), degree of order (DO) and enthalpy, inhibiting their increase during storage, thereby retarding the regeneration of the TBS-rutin complex. A higher storage modulus (G′) value was observed in the complexes when Ca(OH)2 was added. Results of in vitro digestion revealed that Ca(OH)2 retarded the hydrolysis of the complex, resulting in an increase in values in slow-digestible starch and resistant starch (RS). Compared with pre-gelatinization, the complex process prepared with the co-gelatinization method presented lower RC, DO, enthalpy, and higher RS. The present work indicates the potential beneficial effect of Ca(OH)2 during the preparation of starch-polyphenol complex and would be helpful to reveal the mechanism of Ca(OH)2 on improving the quality of rutin riched Tartary buckwheat products. [ABSTRACT FROM AUTHOR]

Pea starches, in both native (NPS) and retrograded-autoclaved forms (RAPS), were subjected to simulated gastrointestinal (GI) digestion in vitro , their multi-scale structural characteristics, morphological features, molecular distribution and thermal properties were characterized. A gradual increase in the short−/long-range crystallinity, melting enthalpy of gelatinization on increasing digestion time was observed for both the native and retrograded-autoclaved pea starch samples based on the X-ray diffraction, Fourier-transform infrared spectra, solid-state 13CNMR and differential scanning calorimetry measurements. It was especially noticed that the growth rate of crystallinity and double helices, as well as the decrease in M w values were evidently greater for RAPS than for NPS. To investigate how different molecular fine structure of pea starch substrate affects the gut microbiota shifts and dynamic short-chain fatty acid profile, their resistant starch residues obtained from both native and retrograded-autoclaved pea starch after 8 h of simulated GI tract digestion was used as the fermentation substrate. The levels of acetate, propionate and butyrate gradually increased with the increasing fermentation time for NPS and RAPS. In comparison to the blank control (i.e. , the group without the addition of carbohydrate), the fermented NPS and RAPS obviously resulted in an increased abundance of Firmicutes and Bacteroidetes , accompanied by a decrease in Proteobacteria , Actinobacteria and Verrucomicrobia. Both NPS and RAPS promoted different shifts in the microbial community at the genus level, with an increase in the abundance of Bacteroides , Megamonas and Bifidobacterium , as well as a reduction in the abundance of Fusobacterium , Faecalibacterium and Lachnoclostridium in comparison to the blank control samples. • A gradual increase in crystallinity of pea starch residue on increasing digestion time was observed. • The increase of crystallinity was greater for autoclaved pea starch than its native form. • SCFA were overall higher for fermentable autoclaved pea starch than its native counterpart. • Taxonomy-based microbial abundance showed divergent shifts with different treatments. [ABSTRACT FROM AUTHOR]

The effect of Artemisia sphaerocephala Krasch polysaccharide (ASKP) on the gelatinization and retrogradation of wheat starch (WS) was studied. RVA results displayed that ASKP addition increased the setback values of WS, which indicated that ASKP might promote the short‐term retrogradation of WS. DSC and XRD results demonstrated that the retrogradation percentage of WS during long‐time storage significantly decreased with the addition of ASKP, suggesting the inhibition effect of ASKP on the long‐term retrogradation of WS. As shown in TPA test, ASKP addition increased the hardness of starch gel at the beginning but decreased it after 14 days' storage. Results of FT‐IR revealed that ASKP could promote the water retention and intermolecular hydrogen bonding formation. With the addition of ASKP, the spin–spin relaxation time measured by LF‐NMR decreased from 358.47 ms to 274.15 ms, illustrating that the WS paste containing ASKP had higher water retention ability. Leached amylose content results manifested the interaction between WS and ASKP. In summary, ASKP has potential to be a modifier on the retrogradation of starch in food processing. [ABSTRACT FROM AUTHOR]

Abstract In order to meet industrial demands, field pea starch was modified by autoclaving (ACP), microwave cooking (MCP), and combined treatments of autoclaving with ultrasonication (UP), acid hydrolysis (AHP), or pullulanase debranching (PDP). The influence of different processing treatments on the structural and physicochemical characteristics of pea starch was investigated by X-ray diffraction (XRD), solid-state 13C nuclear magnetic resonance (13CNMR), Fourier transform infrared spectroscopy (FT-IR), small angle X-ray scattering (SAXS), differential scanning calorimeter (DSC), and scanning electron microscope. Processing of pea starch tended to decrease the long-range structural order with relatively lower values of crystallinity observed from XRD, whereas the double helical structure which is arranged at short range scale was enhanced to certain extents after different treatments. Microwave cooking was shown to be less effective than other treatments in promoting the formation of stabilized double helical structure, with the lowest values of crystallinity, degree of order (DO), double helix content, and gelatinization enthalpy obtained for MCP based on XRD, FT-IR, 13CNMR, and DSC observations. The experimental results also suggested that autoclaving had a less pronounced effect than the combined treatments of autoclaving-debranching, acid hydrolysis-autoclaving, and ultrasound-autoclaving on facilitating the formation of short-range ordered structure, with significantly lower values of DO, and double helix content obtained for ACP compared with AHP, PDP, and UP. This study was expected to provide a theoretical basis for the better understanding of the structure-processing-functionality relationship of starch polymers and to help the food industry to design novel starch materials with desirable functional properties. Graphical abstract Image 101 Highlights • Field pea starch was modified by physical, enzymatic, and acid treatments. • Processing of pea starch decreased the long-range crystallinity by X-ray diffraction. • The double helix structure arranged in short-range scale was enhanced upon processing. • The lamellar peak of the ∼9–10 nm thickness was disappeared for all processed starch. • Microwave cooking was less effective in promoting double helix structure formation. [ABSTRACT FROM AUTHOR]

The molecular structural changes of the starch isolated from untreated (ULS), roasted (RLS), germinated (GLS), fermented (FLS), microwave cooked (MLS), conventional cooked (CLS), and autoclaved (ALS) lentil seeds were investigated. All starch samples obtained were categorized by size exclusion chromatography with multi-angle laser scattering into two groups, i.e., Group A with two population of peaks appeared for samples including ULS, RLS, and GLS; and Group B with three population of peaks shown in samples including FLS, MLS, CLS and ALS. A noticeable decrease in relative crystallinity by XRD was found for all starch from the processed seeds (11.41–3.24%) compared with starch isolated from untreated seeds (15.90%), especially that a greater extent of such decreasing was observed for FLS, MLS, CLS, and ALS (Group B samples). The intensity of the absorptions related to hydrogen bonding by FT-IR (3000-3600 cm −1 , and ∼1000 cm −1 ) were markedly decreased for lentil starch isolated from processed seeds compared with native starch, and, especially for treated samples of Group B, which also exhibited the significantly higher degree of double helix and lower value of degree of order. Small angle X-ray scattering data manifested that the typical ∼9–10 nm semi-crystalline structure was disappeared for the Group B samples which were characterized with the relatively higher values of d , d a , and d c . The results suggested that the densely packed crystalline structure could be shifted within the crystallites and tended to result small new crystal structure during the processing of lentil seeds, and such effect was particularly obvious for starch samples including FLS, CLS, MLS, and ALS. [ABSTRACT FROM AUTHOR]

The multi-scale structural order and bile acid (BA) binding capacity of resistant starch (RS) isolated from native, different processed and recrystallized pea starch samples were studied. Different treatments applied include acid hydrolysis (AHPRS), pullulanase-debranching (PDPRS), autoclaving (ACPRS), ultrasound-autoclaving (UAPRS), and microwave cooking (MCPRS). Subsequently, the native, processed and recrystallized starch were subjected to in vitro digestion using thermostable α-amylase and amyloglucosidase to obtain the isolated RS. The M w values of RS samples ranged from 2.448 × 104−9.750 × 106 g/mol, with the highest value noticed for ACPRS, and the lowest one for NPRS. The B-type and a small amount of V-type crystalline pattern was observed in all RS samples. Based on X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) measurement, the RS isolated from native pea starch, which is of type II resistant starch, exhibited the significantly lowest crystallinity and degree of order (DO), compared with RS 3 samples prepared from processed and recrystallized starch. The relative crystallinities measured by 13CNMR (16.78–18.97%) were generally higher than the values of crystallinity obtained from XRD (3.36–12.23%). The strongest absorption that is related to O-H stretching between 3000 and 3600/cm on the FT-IR spectra, the highest DO value, and the highest BA binding capacity were observed for AHPRS. • Resistant starch was isolated from native and processed starch by in vitro digestion. • Resistant starch from acid-treated starch showed highest bile acid binding capacity. • The M w values of all resistant starch samples ranged from 2.448 × 104−9.750 × 106 g/mol. • Type II resistant starch showed lower crystallinity than type III resistant starches. • All resistant starches were classified as the mass fractal structure based on SAXS. [ABSTRACT FROM AUTHOR]

• Natural fermentation is an effective method to modify wheat starch. • Wheat starch granule surface was slightly eroded during natural fermentation. • The relative crystallinity of wheat starch increased after fermentation. • Fermentation decreased the amorphous region of wheat starch granules. • Pasting properties of wheat starch were changed by natural fermentation. In this study, the effects of natural fermentation on the multi-scale structure and physicochemical properties of wheat starch were investigated. The results showed that fermentation reduced weight-average molecular weight (M w) and slightly eroded the starch granule surface. An obvious increase in relative crystallinity from X-ray diffraction was observed in all fermented starch (39.38–42.27%) when compared with native starch (37.15%). Data from small angle X-ray scattering revealed that fermentation increased the crystalline layer and decreased the amorphous region of the starch granules. The intensity of absorption related to hydrogen bonding by FT-IR (3000–3600 cm−1) also increased in fermented starch. The rapid viscosity analysis results showed that fermented starch had a lower peak viscosity and final viscosity, and a lower setback value than native starch. The present results reveal that fermentation is an effective method to modify wheat starch and suggest its potential to improve the quality of starch-based foods. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of gaseous ozone treatment on the structural, physicochemical and in vitro digestible properties of Tartary buckwheat starch (TBS). The results showed that gaseous ozone treatment increased the detectable carbonyl and carboxyl groups content, improved the amylose content, and decreased pH of TBS. The granule microstructures of native TBS and ozone-treated TBS (OTBS) were characterized by SEM, CLSM and small-angle X-ray scattering (SAXS), showing that OTBS exhibited a reduced granule smoothness and integrity, lessened coloration area of FITC fluorescent as well as decreased crystalline layer and increased amorphous region. FTIR and XRD results revealed that appropriate time of gaseous ozone treatment (2.5 and 7.5 min) enhanced short-range and long-range order structure due to the increased intermolecular oxidation cross-linking, whereas over treatment (15 and 20 min) caused degradation of the starch. With the increasing treatment time, apparent viscosity increased while breakdown viscosity, setback viscosity, swelling power and solubility decreased. OTBS exhibited a higher gelatinization enthalpy (ΔH) and a better viscoelasticity after gelation (6% OTBS gel, w/w). Additionally, OTBS-2.5 and OTBS-7.5 showed a decreased rapidly digested starch (RDS) content and increased resistant starch (RS) content, indicating that the digestible properties of two oxidized starches was decreased, which provide a feasible way to develop TBS as a new modified starch source. [Display omitted] • Gaseous ozone changed the granule morphology of Tartary buckwheat starch. • Ordered and double helices structures of starch were enhanced by moderate ozone. • The formation of more carbonyl and carboxyl groups in starch were detected. • The modified starches showed stronger gelling property and weaker retrogradation. • Moderate oxidized starch possessed lower digestibility than that of native starch. [ABSTRACT FROM AUTHOR]