Digestible Starch Content Research Articles

Heat-induced amorphous aggregates assembly of soy protein modulate in vitro digestibility of potato starch

This research focused on the characteristics of amorphous aggregates derived from soy protein (SPAA), and their effects on the structural, physicochemical, and digestive properties of potato starch (PS). The SPAA induced by different heating temperatures at pH 7.0 formed an inhomogeneous spherical structure. The presence of SPAA could improve the degree of short-range order of starch, increase thermal stability, reduce pasting viscosity and breakdown, and setback viscosity values of PS. For the PS complexed with SPAAs under simulated cooking conditions, the fraction of digested starch at 300 min (C300) decreased by 6–14 %, and rapid digestible starch content (RDS) decreased by 18–25 %, while the slowly digestible starch (SDS) and resistant starch (RS) increased by 0.4–3 % and 15–23 %, respectively. The SPAA at higher temperature treatment (SPAA130) reduced digestive rate coefficient (k) values more significantly than SPAA at a lower temperature (SPAA70, SPAA90, SPAA110). And the SPAA had no inhibitory effect on α-amylase. The results of this study would significantly contribute to expanding the theoretical information about protein regulation in starch digestion and promoting the development of healthy foods with digestion-resistant properties.

Starch digestion retarded by wheat protein hydrolysates with different degrees of hydrolysis

Wheat protein hydrolysates (WPH) were prepared by pepsin hydrolysis for 30, 60, and 120 min (WPH30, WPH60, and WPH120). The mixed system of rice starch and WPH was hydrothermally treated to explore the effect of WPH with different degrees of hydrolysis on starch digestion. WPH reduced the first-order rate coefficient (k) of starch digestion. Especially, WPH30 reduced the k value the most and formed the highest slowly digestible starch content due to the entanglement of starch chains and long-chain peptides. WPH60 and WPH120 with more hydrophobic peptides and polar amino acids than WPH30 tended to form hydrogen bonds with starch molecules due to less steric hindrance. Particularly, the complexation of WPH60 promoted the formation of dense aggregate structure and hindered the enzymatic hydrolysis of starch to a certain extent, thereby increasing the resistant starch content. These findings provide significant guidance for the preparation of hypoglycemic reformed food.

Insights into the textural properties and starch digestibility on rice noodles as affected by the addition of maize starch and rice starch

The effects of maize starch (MS) and rice starch (RS) addition on rice noodle quality were investigated, aiming to develop high-quality noodles with both desirable textural properties and low starch digestibility. The results showed that the MS had more short branch chains and higher branch density when compared to RS, and the final viscosity and gel strength of rice paste decreased with its addition. The textural properties between rice noodles with less than 20% MS and without MS did not differ significantly, while the network structure of rice noodles with more MS was significantly weakened due to the steric hindrance of short branch chains. The addition of RS increased the texture quality of rice noodles. Moreover, their addition reduced the estimated glycemic index of rice noodles, because more starch promoted the arrangement of starch chains and formed ordered double helix. The MS with more short chains was conducive to the formation of double helix to reduce digestion rate, and the RS with more long chains formed stabler gel and crystal structures to reduce digestible starch content. Therefore, MS and RS addition had potential to produce rice noodles with high comprehensive quality, and MS content should be controlled below 20%.

Organoleptic, hypoglycaemic, and in vitro starch digestion effects of formulated Melon Manis Terengganu peel powder

Melon Manis Terengganu (MMT) is comprised of 28 - 30% peel which is a by-product of food processing. The peel is a source of dietary fibre which has a potential role in glycaemic response. The present work thus aimed to develop formulated MMT peel powder, and examine its organoleptic properties, in vitro hypoglycaemic effect, and starch digestibility. The MMT peel powder was formulated as Formulations 0, 1, 2, and 3 with different sweetener ratios (0, 40, 50, and 60%), and subjected to sensory evaluations. Tukey’s post-hoc test was used to evaluate significant differences between mean values following one-way analysis of variance (ANOVA). Meanwhile, the Friedman test followed by Wilcoxon signed ranks test were performed for sensory evaluation analysis. Results demonstrated that the most acceptable formulation for consumption assessed using sensory evaluation was Formulation 3; its total, digestible, and resistant starch content were the lowest among all the formulations. The same went to the hydrolysis index and estimated glycaemic index. However, Formulation 3 was the least effective in reducing glycaemic response due to the weakest in vitro hypoglycaemic activity. On the other hand, the mentioned attributes previously were observed in Formulation 0 in an opposite manner. In summary, these findings suggested that formulated MMT peel powder had the potential to be used in blood glucose control.

Effects of moisture content on digestible fragments and molecular structures of high amylose jackfruit starch prepared by improved extrusion cooking technology

The effects of different moisture contents on the digestible fragments and molecular structures of high amylose jackfruit starch were investigated. The digestible fragments and molecular structures of rapidly digestible starch, slowly digestible starch and resistant starch of high amylose jackfruit starch with different moisture contents prepared by improved extrusion cooking technology were analyzed. Decreasing the moisture content resulted in significant decrease in slowly digestible starch and resistant starch content (24.08% and 25.99%–17.59% and 16.60%), indicating that high amylose jackfruit starch with low moisture content was easier to digest. Compared to extruded control starches, the slowly digestible starch + resistant starch fraction and resistant starch samples exhibited higher gelatinization enthalpy, relative crystallinity, and short - range molecular order, but no significant difference was showed in gelatinization temperature. It was also found that the double helix degree, crystallinity and order degree of the extruded controls, slowly digestible starch + resistant starch fractions and resistant starch samples were increased with increasing moisture content, from 1.74 J/g, 1.52% and 0.207–9.52 J/g, 32.54% and 0.779, respectively. The above results were further supported by the microstructural and porosity analysis that the extruded samples were changed from coarser surface structure to more compact structure with increasing moisture content. All these results indicate that moisture content affects the digestible fragments and molecular structures of starch. Therefore, it can provide a theoretical basis for the modification of high amylose starch, especially for the modification of resistant starch. • High amylose jackfruit starch (HA-JFSS) were prepared by improved extrusion cooking technology. • Different moistures content affected the digestible fragment and molecular structure of HA-JFSS. • Decreasing moisture content improved the in vitro digestibility of extruded HA-JFSS. • High moisture content HA-JFSS showed higher double helix, long/short-range molecular order. • The analysis of SEM demonstrated the results of the DSC, XRD and FITR.

Structure, gelatinization, and digestion characteristics of starch from Chinese wild rice

ABSTRACT Two wild rice starches were isolated from Erhai in Dali, Yunnan Province (EWR) and Xinghua in Taizhou, Jiangsu Province (XWR), China, and compared with black rice (BR) starches, its structure, gelatinization and starch digestibility in vitro were studied. The results showed that the apparent amylose content of starches in EWR and XWR was 19.82% and 20.33%, respectively. The starch granules were irregular polygons and all were A-type crystals, with relative crystallinity of 25.6%~26.65%, similar short-range ordered structure and layered structure, and the thickness of the semi-crystalline layer ranged from 9.82 nm to 9.97 nm. XWR and EWR starches had exhibited the same gelatinization temperature range, enthalpy of gelatinization (ΔHgel) and swelling power, but XWR starches was higher than EWR in the gelatinization temperature and lower than EWR in the solubility. The rapidly digestible starch (RDS) content of wild rice starches in the two regions was low, only 3.63% and 37.32%, whether it was raw starches or gelatinized starches. After gelatinization, the RDS and slowly digestible starch (SDS) content were significantly increased and the resistant starch (RS) content was decreased, but the RS content was still higher than the common grains. Therefore, the wild rice starches are more suitable for processing and producing resistant starch products. Extracting starch from Chinese wild rice can provide guidance and reference for its application in edible and non-edible products, and promote the development and utilization of Chinese wild rice. Abbreviations: EWR, wild rice from Erhai in Dali, Yunnan Province; XWR, wild rice from Xinghua in Taizhou, Jiangsu Province; RDS, rapidly digestible starch; SDS, slowly digestible starch; RS resistant starch; TS, total starch; To, onset temperature of gelatinization; Tp, peak temperature of gelatinization; Tc, conclusion temperature of gelatinization; ∆Hgel, enthalpy of gelatinization.

Structure and physicochemical properties of low digestible Euryale ferox Salisb. seed starch.

Euryale ferox Salisb. is widely grown in China and Southeast Asia as a grain crop and medicinal plant. The composition, morphology, structure, physicochemical properties, thermal properties, and in vitro digestibility of North Euryale ferox seeds starch (NEFS), hybrid Euryale ferox seeds starch (HEFS), and South Euryale ferox seeds starch (SEFS) were studied. Of the varieties that were studied, the amylose content of NEFS (23.03%) was the highest. Starch granules of each variety were smooth, sharp, small, and had an average diameter of 2μm. All three varieties were A-type crystals with crystallinity ranging from 26.42% to 28.17%. The degree of double helix and the short-range order ranged from 1.9006 to 2.5324 and 1.4294 to 1.6006, respectively. The high proportion of C1 region in NEFS (17.74%) and HEFS (17.66%) were found. Thermodynamic properties inNorth Euryale ferox seeds included the highest onset temperature (To ) (71.43 °C), peak temperature (Tp ) (76.60 °C), conclusion temperature (Tc ) (82.77 °C), enthalpy of gelatinization (ΔH) (12.64 J g-1 ), and peak viscosity (1514 mPa·s). All three varieties maintained a low level of in vitro digestibility, with the highest resistant starch (RS) content (29.57%), the lowest rapidly digestible starch (RDS) content (27.07%), and the slowest hydrolysis kinetic constant (0.0303) in NEFS. The results revealed that the low digestibility of NEFS was attributable to compact granules, high crystallinity, high degree of order, and strong thermal stability. These digestive, physicochemical, and thermodynamic properties provide information for the future application of Euryale ferox seed starch in the food industry. © 2022 Society of Chemical Industry.

Effect of Heat–Moisture Treatment on the Physicochemical Properties, Structure, Morphology, and Starch Digestibility of Highland Barley (Hordeum vulgare L. var. nudum Hook. f) Flour

This study modified native highland barley (HB) flour by heat-moisture treatment (HMT) at different temperatures (90, 110, and 130 °C) and moisture contents (15%, 25%, and 35%). The effects of the treatment on the pasting, thermal, rheological, structural, and morphological properties of the native and HMT HB flour were evaluated. The results showed that HMT at 90 °C and 25% moisture content induced the highest pasting viscosity (3626-5147 cPa) and final viscosity (3734-5384 cPa). In all conditions HMT increased gelatinization temperature (To, 55.77-73.72 °C; Tp, 60.47-80.69 °C; Tc, 66.16-91.71 °C) but decreased gelatinization enthalpy (6.41-0.43 J/g) in the HMT HB flour compared with that in the native HB flour. The HB flour treated at 15% moisture content had a higher storage modulus and loss modulus than native HB flour, indicating that HMT (moisture content, 15%, 25%, and 35%) favored the strengthening of the HB flour gels. X-ray diffraction and Fourier-transform infrared spectroscopy results showed that HMT HB flour retained the characteristics of an A-type crystal structure with an increased orderly structure of starch, while the relative crystallinity could be increased from 28.52% to 41.32%. The aggregation of starch granules and the denaturation of proteins were observed after HMT, with additional breakage of the starch granule surface as the moisture content increased. HMT could increase the resistant starch content from 24.77% to 33.40%, but it also led to an increase in the rapidly digestible starch content to 85.30% with the increase in moisture content and heating temperature. These results might promote the application of HMT technology in modifying HB flour.

Starches Isolated from the Pulp and Seeds of Unripe Pouteria campechiana Fruits as Potential Health‐Promoting Food Additives

AbstractThe non‐conventional starch isolated from unripe fruits is an alternative to obtain this raw material with improved or different functionality and digestibility. The starch isolated from Pouteria campechiana pulp (SIP) and seeds (SIS) of unripe fruits shows similar average granule sizes and A‐type X‐ray diffraction pattern. The digestibility characteristics are related to the hierarchical structure, since the amylopectin of the SIS sample has the highest crystallinity percentage and degree of polymerization (DP). These long amylopectin chains produce a thermally stable helical structure. Resistant starch (RS) in the SIP and SIS samples remains after cooking, and the cooked SIS show an increase in slowly digestible starch (SDS) content. In contrast, cooked SIP has an increased content of rapidly digestible starch (RDS). The SIP sample also shows interesting β‐carotene content values (15.4 µg g−1 dry starch) for the manufacture of potentially health‐promoting food additives in terms of anti‐inflammatory and antioxidant activities. The supramolecular structure–in vitro digestibility relationship of the SIS sample yields interesting results as a novel, low‐cost, and underutilized alternative starch source for the manufacture of potential health‐promoting starchy food additives.

In Vitro Digestibility, Pasting and Thermal Properties, and Structure of Cross‐Linked Arenga pinnata (Wurmb.) Merr. Starch

AbstractSodium trimetaphosphate (STMP) cross‐linked Arenga pinnata starch (CLAPS) with different degrees of cross‐linking (0–97.79%) are prepared and their structural characteristics and physicochemical properties are evaluated. Cross‐linking does not significantly change APS granular structure, but seems to lower the intensity of Maltese cross. With the cross‐linking degrees (CLD) increasing from 0.00% to 97.79%, the rapidly digestible starch (RDS) content of CLAPS is decreased from 66.50% to 16.34%, but the resistant starch (RS) content has the opposite trend and is increased from 29.87% to 82.77%. As the CLD increased, the solubility and swelling power of APS are significantly reduced from 10.24% and 16.52 g g−1 to 1.02% and 4.60 g g−1, respectively. Low CLD could increase viscosities of the APS, whereas high CLD significantly reduce the viscosities of the APS and the greater theCLD, the more obvious the reduction effect. Meanwhile, cross‐linked APS exhibits a high conclusion temperature and lower gelatinization enthalpy (ΔH). With the CLD increasing, short molecular ordered structure of CLAPS exhibits increasing trends. These results indicate that crosslinking with STMP can significantly alter digestibility and improve thermal stability of APS, which would provide a theoretical basis for development of APS products and could be used in low glycemic index (GI) foods.

Comparative study on bread quality and starch digestibility of normal and waxy wheat (Triticum aestivum L.) modified by maltohexaose producing α-amylases

It is highly desirable to produce bread with both acceptable texture and health benefits. In this study, maltohexaose (G6) producing amylase AmyM and its truncation AmyM-TR2 from Corallococcus sp. strain EGB were used to determine their effects to bread quality and starch physicochemical properties. During bread fermentation, AmyM or AmyM-TR2 continuously degraded the starch, resulting in more obvious decrease in relative crystallinity, the ordered structure, pasting viscosities and gelatinization enthalpy of starch than in control. The dough treated with AmyM or AmyM-TR2 increased bread volume and slowly digestible starch content, decreased bread hardness, and extended bread shelf life and as compared with control, and the dough treated with AmyM-TR2 had better improvement effects than AmyM. The volume and slowly digestible starch content of bread from the treatment of AmyM-TR2 increased by 9.74% and 7.56% in normal wheat, 1.42% and 10.28% in waxy wheat as compared with AmyM, respectively. AmyM-TR2 affected the substrate targeting, proximity and structure disruption effects, which contributed to the degradation of more starch than AmyM.

Structure, physicochemical, functional and in vitro digestibility properties of non-waxy and waxy proso millet starches

The structural, physicochemical, gel textural, rheological, and in vitro digestibility properties as well as their relationships of non-waxy proso millet starch (NPMS) and waxy proso millet starch (WPMS) were evaluated by taking normal corn starch (CS) and potato starch (PS) as controls. Proso millet starch was mostly polygonal or spherical, with an A-type crystalline structure. Proso millet starch contained more short-branched chains (DP 6–24) compared with CS and PS. WPMS possessed higher crystallinity and more short-range ordered structures than NPMS. NPMS displayed higher pasting temperature, retrogradation rate and shear thinning degree, and lower gelatinization temperature and enthalpy than WPMS. The hardness and chewiness of starch gel formed by NPMS were higher than those of WPMS. All starch samples exhibited shear thinning behavior in the steady-flow test and typical elastic solid behavior in the dynamic rheological test. Moreover, NPMS was considered a potential formula for functional foods, with its lower rapidly digestible starch (RDS) and higher resistant starch (RS) contents than WPMS, CS, and PS. This paper revealed the influence of amylose content and structure on the physicochemical properties of different proso millet starch.

Effect of endogenous proteins and heat treatment on the in vitro digestibility and physicochemical properties of corn flour

Starch and protein in corn flour (CF) exist in the form of coexistence, which provides an opportunity to reduce the digestibility of CF by using protein. This study aimed to investigate the effects of endogenous proteins and heat treatment during processing on CF digestibility, with emphasis on establishing relevant physicochemical mechanisms. The in vitro digestibility of CF was significantly decreased compared with that of CF without protein (CF-P); the rapidly digestible starch (RDS) content decreased from 91.37% to 77.52%, and the resistant starch (RS) content increased from 4.58% to 15.18%. Similarly, the three heat treatments could reduce starch digestibility of CF. The microstructure showed that proteins can partially or completely encapsulate starch granules to form aggregates of starch granules bound by proteins. The presence of protein and heat treatment can significantly reduce the swelling power of CF and increase the gelatinization temperature of CF, which has a certain correlation with the RS content. The existence of strong hydrogen bonds and disulfide bond (S-S) between starch and protein can improve the thermal stability and interaction force of starch and effectively protect starch granules from shearing. Protein competed with starch for water molecules that may delay the rate of water entering starch and increase the gelatinization temperature. These findings have significant implications for CF food design.

Effects of hot air and radiofrequency multi-stage drying for native potato flour processing: Functional and chemical characteristics

Native potato flour is one of the most promising food sources or additives to meet the increasing need for healthy food. Multi-stage drying is one of the most promising methods for potato drying, but the chemical and functional properties need to be evaluated. In this work, the soluble peptide, digestibility, enzyme activity, flavonoid, and odorants with multi-stage drying methods were studied. Results showed that high-temperature first stage (HTFs) treatment enhanced the slowly digestible starch content and Maillard reaction, but the highest effective concentration for 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging ratio at 50% (77.62 mg/mL), and 6.995 mg/mL of soluble peptide could be found for the 90 + 60 °C hot air dried sample. This indicated that longstanding decelerate drying stage treatment has obvious damage effects on antioxidant activity and proteins. The HTFs treatment has positive effects to enhance the drying rate and quality of native potato flour, but the second stage needs to be minimized. Moreover, radiofrequency assisted method might be a better solution.

A novel starch-based microparticle with polyelectrolyte complexes and its slow digestion mechanism

Encapsulation with polyelectrolyte complexes (PECs) was a novel approach to construct the starch based-microparticle with slow digestibility. In this study, sodium alginate (SA), gellan gum (GG) and chitosan (CS) were used to prepare SA/GG/CS based-PECs, while potato starch (PS) or its complex with lauric acid (PSL) were taken as the starch materials to obtain the starch based-microparticles (PSM or PSLM, respectively). The characteristic properties, morphological features, stability, and in vitro digestibility of their microparticles were investigated. From structure aspect, the PECs were steadied by the electrostatic interactions from negative and positive donors, and wrapped around starch granules to form the highly-hydroscopic hydrogel. This structure could withstand the heating treatment and in vitro simulated digestive fluid to some extent, thereby exhibiting better stability and slower digestibility than starch samples. Also, the slowly digestible starch content and the resistant starch content could be preserved at high levels, especially for PSLM. Besides, the release rate of lauric acid from PSLM was still low during the in vitro simulated digestion, which was also beneficial to health in terms of fatty acid intake. Hence, that was to say that the starch microparticle with SA/GG/CS based-PECs had the potential to be utilized in diet for hyperglycemia patients.

Effect of thermal treatments and non‐starch fraction on in vitro starch digestibility of oat bran

AbstractThe effects of removing non‐starch constituents like lipids, proteins, and β‐glucan on the in‐vitro digestibility of oat bran by steaming, microwaving, and hot air drying were investigated in this study. The results showed that the rapidly digestible starch (RDS) content of steaming oat bran decreased significantly (p < 0.05), and the glycemic index (e GI) was the lowest (66.11). The resistant starch (RS) content decreased, and in vitro digestibility, hydrolysis index, and eGI values of pretreated oat bran increased after removing the non‐starch constituents. Lipid removal increased in vitro digestibility the most, followed by β‐glucan and protein removal. The solubility of oat bran with removing protein increased significantly after steaming and microwaving treatment (p < 0.05). The relative crystallinity of oat bran decreased during steaming and increased after microwave and hot air drying. In conclusion, co‐existed components like proteins, fiber and lipids are helpful to a purpose of a low GI and slow starch digestion.Practical applicationsIn this study, high value‐added utilization of oat bran was realized, which solved the problems of resource waste and environmental pollution. Meanwhile, the steaming oat bran with intact structure is helpful for a purpose of low GI and slow starch digestion and is more beneficial to human health.

Pasting and gelation behaviors and in vitro digestibility of high-amylose maize starch blended with wheat or potato starch evaluated at different heating temperatures

Different approaches have been adopted to overcome the inherent shortcomings of native starches, and blending of different native starches has attracted much attention due to the “clean-label” feature and the low processing effort and cost. In the current study, we blended high-amylose maize starch (HA7) with wheat (WHE) or potato (POT) starch at 1:1 ratio (dry weight basis; dwb) and then comprehensively examined their thermal properties, pasting and gelling behaviors over the heating temperature range of 95–140 °C, and in vitro digestibility in comparison with three individual starches. With an excess amount of water (starch:water = 1:3), gelatinization of individual starches generally appeared to be independent in the two starch blends. An exceptionally low percentage of retrogradation was observed for gelatinized HA7-WHE blend during cold storage, which could be partially ascribed to the formation of a large amount of amylose-lipid complexes (ALC). Greater resistance to thermal degradation and thixotropic breakdown during pasting at 120 °C was found with HA7-WHE blend when compared with HA7-POT blend. Both starch blends could form gels with moderate strength (74.3–109.4 g) after cooking at 120 and 140 °C. The determined resistant starch (RS) and slowly digestible starch (SDS) contents of water-boiled HA7-WHE blend were higher than the calculated values when assuming simple additivity of the two starches. The interactions at both granular and molecular levels and the presence of ALC were responsible for the reported unique techno-functional attributes of HA7-WHE blend, which rendered it suitable for diverse food and industrial applications. • More amylose-lipid complex in high-amylose (HA7)-wheat (WHE) starch blend (1:1 dwb). • Gelatinized HA7-WHE blend had the least %retrogradation (9.2%) of all the starches. • HA7-WHE blend showed strong resistance against high-temperature cooking at 120 °C. • Starch blends had moderate gel strength (74.3–109.4 g) after 120 and 140 °C cooking. • Water-boiled HA7-WHE blend showed enhanced in vitro enzymatic resistance.

The Effect of Soybean Peptides on Improving Quality and the ACE Inhibitory Bioactivity of Extruded Rice

It is crucial to address the dietary problems of hypertensive patients. The effect and mechanism of different contents of soybean protein on cooking quality and angiotensin-converting enzyme (ACE) inhibitory action in the extruded rice were firstly investigated. The results showed that the extruded rice with soybean protein possessed the higher taste value (90.32 ± 2.31), hardness (2.65 ± 0.01 g), and good pasting quality (p ≤ 0.05). Meanwhile, the soybean protein notably retarded the starch digestibility; the sample with 6% soybean protein showed the fewest rapidly digestible starch (RDS) content (78.82 ± 0.01 mg g−1) and the most slowly digestible starch (SDS) content (8.97 ± 0.45 mg g−1). Importantly, the ACE inhibition rate improved from 17.09 ± 0.01% to 74.02 ± 0.65% in the 6% soybean protein sample because of the production of peptides. The peptide composition of samples were compared, which showed that the effective ACE-inhibitory peptides usually contain 2~20 amino acids, and Pro, Leu, Ile, Val, Phe, and Ala were the main components. Overall, moderate soybean protein would give a good quality and lower ACE activity in extruded food.

The formation of starch-lipid complexes in instant rice noodles incorporated with different fatty acids: Effect on the structure, in vitro enzymatic digestibility and retrogradation properties during storage

The formation of starch-lipid complexes in instant rice noodles (IRN) free from and incorporated with fatty acids (FAs) and their impacts on textural, in vitro digestive and retrogradation properties were investigated. The gelatinization enthalpy values of IRN samples (1.24–4.93 J/g) were noticeably decreased (P < 0.05) compared to rice starch samples (2.54–6.89 J/g) fortified with FAs. Additionally, long-chain saturated FAs (stearic acid (SA, C18:0)) complexes produced higher ordered structures than the shorter-chain FAs (C12:0-C16:0), for 18-carbon FAs, the unsaturated FAs (linoleic acid (LOA, C18:2)) exhibited the strongest intermolecular interactions with rice starch. The relative crystallinity of IRN (27.01%–38.47%) was lower than the rice starch-FAs complexes (38.36%–56.80%). FAs delayed the retrogradation degree of IRN storaged at 4 °C for 21 days ascribed to the formation of V-type complexes. Higher enzymatic resistance was observed in IRN added FAs with resistant starch content increased from 5.13% to 14.42% (LOA), and the sample fortified with SA exhibited the highest slowly digestible starch content (35.92%). SEM revealed that the IRN compounded with palmitic acid, SA and LOA displayed more compact and regular structures. Overall, the formation of starch-FAs complexes probably is a novel strategy in improving the textural, digestive, and retrogradation properties of IRN.

Highland Barley Polyphenol Delayed the In Vitro Digestibility of Starch and Amylose by Modifying Their Structural Properties.

Slowing starch digestibility can delay or even prevent the occurrence and development of type 2 diabetes. To explore the hypoglycemic potential of highland barley polyphenols (HBP), this study investigated the structural characteristics and starch digestibility of individual or mixed HBP-starch complexes. The results showed that a V-type structure was formed in HBP-starch complexes through non-covalent bonds, resulting in a decrease in rapidly digestible starch and an increase in resistant starch. Specially, the compounding of HBP extracted by acetone significantly reduced the rapidly digestible starch content in amylose from 41.11% to 36.17% and increased the resistant starch content from 6.15% to 13.27% (p < 0.05). Moreover, due to different contents and types of monomer phenols, the HBP extracted with acetone were more effective in inhibiting starch digestion than those extracted with methanol. Ferulic acid and catechin were two key components of HBP. Further results indicated that with the increased content of ferulic acid and catechin (from 1% to 5%), they formed a more ordered structure with amylose, resulting in the lower digestibility of the complex. Collectively, this study suggested that highland barley polyphenols could effectively delay starch digestion by forming a more ordered starch crystal structure. Highland barley polyphenols can be used as functional ingredients in regulating the digestive properties of starchy foods.