Resistant starch formation through intrahelical V-complexes between polymeric proanthocyanidins and amylose

Structural properties and antioxidant capacity of different aminated starch-phenolic acid conjugates

Different aminated starch (AS) [EEAS (introducing ethylenediamine into starch using cross-linking-etherification-amination method (CEA)), EPAS (introducing o-phenylenediamine using CEA), OEAS (introducing ethylenediamine using cross-linking-oxidation-amination method (COA)), and OPAS (introducing o-phenylenediamine using COA)] were synthesized. The AS-phenolic acids [gallic acid (GA), syringic acid (SA), and vanillic acid (VA)] conjugates were prepared by laccase-catalyzed reaction. The grafting efficiency of EEAS on GA, SA, and VA was 36.59%, 69.71%, and 68.85%, respectively. SA reduced the maximum depolymerization rate of EEAS. The relative crystallinity of EEAS and EPAS grafted phenolic acid increased, and their particles showed severe breakage in appearance. OEAS-phenolic acid conjugates lost its granular structure and behaved as flakes and lumps, while the surface of OPAS-phenolic acid conjugates remained smooth after grafting phenolic acid. GA increased the DPPH· scavenging efficiency of EEAS from 16.12% to 79.92%. The increased antioxidant capacity of the conjugates suggested that AS-phenolic acids conjugates have high potential for applications.

Rheological properties, multiscale structure, and in vitro digestibility of a maize starch-konjac glucomannan-bamboo leaf flavonoid complex modified by dynamic high-pressure microfluidization

The effects of dynamic high-pressure microfluidization (DHPM) treatment on the rheological properties, multiscale structure and in vitro digestibility of complex of maize starch (MS), konjac glucomannan (KGM), and bamboo leaf flavonoids (BLFs) were investigated. Compared with MS, the MS-KGM-BLF complex exhibited reduced viscosity and crystallinity, along with increased lamellar thickness to 10.26 nm. MS-KGM-BLF complex had lower viscosity after DHPM treatment. The highest ordered structure and crystallinity were observed at 50 MPa, with the α value increasing from 3.40 to 3.59 and the d value decreasing from 10.26 to 9.81 nm. However, higher DHPM pressures resulted in a decrease in the α value and an increase in the d value. The highest gelatinization enthalpy and resistant starch content were achieved at 100 MPa DHPM, while the fractal structure shifted from surface fractal to mass fractal at 150 MPa. This study presents an innovative method for enhancing the properties of MS.

Liquid nitrogen ball-milled mechanochemical modification of starches with typically selected A, B and C crystal types on multiscale structure and physicochemical properties

This study investigated the effect of liquid nitrogen ball-milled mechanochemical treatment on multiscale structure and physicochemical properties of starches with typically selected A (rice starch, ReS), B (potato starch, PtS) and C (pea starch, PeS) crystal types. The morphology of starch samples changed from integral granules to irregular fragments, and the interaction between the exposure OH bonds led to a serious agglomeration. As the treatment times extended, the crystalline structure of starch samples was gradually destroyed, and the excessive treatment approached amorphization. Moreover, the thermal stability of starch samples showed the downward tendency; and with amorphization increased, the swelling power (SP), solubility (S), water absorption capacity (WAC), oil absorption capacity (OAC) and hydrolysis rate of starch samples gradually increased. The obtained results provided a theoretical foundation for broadening the application range of ball-milled starches with different crystal types.

Research progress on the regulation of starch-polyphenol interactions in food processing

Starch is a fundamental material in the food industry. However, the inherent structural constraints of starch impose limitations on its physicochemical properties, including thermal instability, viscosity, and retrogradation. To address these obstacles, polyphenols are extensively employed for starch modification owing to their distinctive structural characteristics and potent antioxidant capabilities. Interaction between the hydroxyl groups of polyphenols and starch results in the formation of inclusion or non-inclusion complexes, thereby inducing alterations in the multiscale structure of starch. These modifications lead to changes in the physicochemical properties of starch, while simultaneously enhancing its nutritional value. Recent studies have demonstrated that both thermal and non-thermal processing exert a significant influence on the formation of starch-polyphenol complexes. This review meticulously analyzes the techniques facilitating complex formation, elucidating the critical factors that dictate this process. Of noteworthy importance is the observation that thermal processing significantly boosts these interactions, whereas non-thermal processing enables more precise modifications. Thus, a profound comprehension and precise regulation of the production of starch-polyphenol complexes are imperative for optimizing their application in various starch-based food products. This in-depth study is dedicated to providing a valuable pathway for enhancing the quality of starchy foods through the strategic integration of suitable processing technologies.

Effects of varied preparation processes on polyphenol-rice starch complexes, in vitro starch digestion, and polyphenols release

This study synthesized composite samples incorporating four representative polyphenolic structures, gallic acid (GA), quercetin (QC), resveratrol (RES), and magnolol (MN), with rice starch using various preparation processes, including the addition of polyphenols and alteration of temperature and pH, via co-gelatinization. Subsequently, the complexation rates, starch digestion properties, and polyphenol release during in vitro digestion were examined. The results indicated that both the preparation process and structural variations of polyphenols affected starch digestion and polyphenol release by modulating the complexation. All polyphenols displayed inhibitory effects on rice starch digestion, with GA being the most efficient polyphenol. Additionally, rice starch exhibited a protective effect against RES during in vitro digestion, as rice starch-coated RES reduced the damage from stomach acids. Overall, these findings may help optimize the processing conditions for the synthesis of polyphenol-rice starch-based food products.

Physiological potential of different Sorghum bicolor varieties depending on their bioactive characteristics and antioxidant potential as well as different extraction methods

A comprehensive study of sorghum bran and flour was performed to explore the secondary metabolite profiles of differently coloured genotypes and to evaluate the variability in the antioxidant properties based on differences in polarity and solubility. This research included one red variety and one white variety. Among the samples, the red variety contained significantly greater amounts of secondary metabolites than did the white variety, with total polyphenol contents of 808.04 ± 63.89 mg.100 g-1 and 81.56 ± 3.87 mg.100 g-1, respectively. High-molecular-weight condensed tannin-type flavonoid extracts with high antioxidant activity were obtained by using relatively low-polarity acetone-water solvents, which was reflected by the measured antioxidant values. Among the methods used, the electron-donating Trolox equivalent antioxidant assay provided the highest antioxidant capacity, with values ranging from 118.5 to 182.6 μmol g-1 in the case of the red variety, in accordance with the electron donor properties of condensed tannins. Key secondary metabolites were identified using MS techniques and quantified using HPLC. Catechin and procyanidin B1 were found in the red variety at concentrations of 3.20 and 96.11 mg.100 g-1, respectively, while the concentrations in the white variety were under the limit of detection. All four tocopherols were found in sorghum, with the red variety containing a higher amount than the white variety, but the vitamin B complex concentrations were higher in the white variety. Overall, the red sorghum variety proved to be a better source of secondary metabolites with potential health benefits and could be used as a nutrient-rich food source.

Understanding the multiscale structure and in vitro digestibility changes of corn starch-ferulic acid complexes induced by high hydrostatic pressure

High hydrostatic pressure (HHP) was used to synthesize corn starch (CS) and ferulic acid (FA) complex (CS-FA). Its effects on the structure of the complex at multiple scales and its digestibility were examined. The results demonstrated that HHP significantly influenced the digestibility of the CS-FA complex, decreasing the content of rapidly digestible starch (RDS) while increasing slowly digestible starch (SDS) and resistant starch (RS). Notably, the combined SDS and RS content in the HHP-treated CS-FA complex with 2.0 % FA addition (38.13 %) was significantly higher (p < 0.05) than those in the CS-FA complex without HHP treatment (29.21 %) and pure CS (21.72 %). The results indicated that HHP treatment reduced the enthalpy change (ΔH), number of short-range order structures, and relative crystallinity (RC) while increasing the average particle size of these CS-FA complexes. This treatment also increased the proportion of amorphous starch regions and the degree of agglomeration between the starch and FA. HHP treatment-induced CS-FA complexes exhibited a denser fractal structure and higher short-range order, affecting the interaction sites between the starch and digestive enzymes. These findings suggest the potential application of HHP treatment and FA in modulating the postprandial glycemic response to starchy food.

High-Resistant Starch Based on Amylopectin Cluster via Extrusion: From the Perspective of Chain-Length Distribution and Structural Formation

Resistant starch (RS) has the advantage of reshaping gut microbiota for human metabolism and health, like glycemic control, weight loss, etc. Among them, RS3 prepared from pure starch is green and safe, but it is hard to achieve structural control. Here, we regulate the crystal structure of starch with different chain-length distributions (CLDs) via extrusion at low/high shearing levels. The change in CLDs in extruded starch was obtained, and their effects on the fine structure (Dm, dBragg, dLorentz, degree of order and double helix, degree of crystal) of RS and its physicochemical properties were investigated by SAXS, FTIR, XRD and 13C NMR analyses. The results showed that the RS content under a 250 r/min extrusion condition was the highest at 61.52%. Furthermore, the crystalline system induced by high amylopectin (amylose ≤ 4.78%) and a small amount of amylose (amylose ≥ 27.97%) was favorable for obtaining a high content of RS3-modified products under the extruding environment. The control of the moderate proportion of the A chains (DP 6-12) in the starch matrix was beneficial to the formation of RS.

Effect of sorghum bran addition on antioxidant activities, sensory properties, and in vitro starch digestibility of Chinese southern-style steamed bread

BACKGROUND

Chinese steamed bread (CSB) is one of the most important staple foods in China and is also popular in South-East Asia. Developing functional CSB could improve people's resistance to inflammatory and non inflammatory diseases. This work investigated the effect of sorghum bran addition on antioxidant activities, sensory properties, and in vitro starch digestibility of Chinese southern-style steamed bread (CSSB).

RESULTS

In this study, the enhanced CSSB with 0-200 g kg-1 of fine black and tannin (sumac) sorghum bran addition was developed. A small change in phenol content and antioxidant activity was observed at various stages in the processing procedure before steaming. Moreover, a high retention of antioxidant phenolics CSSB with sorghum bran addition was observed. Sorghum bran addition significantly increased the total phenol content and antioxidant activity of CSSB by 4.5-10 times, on average, relative to control. Sorghum bran addition significantly also increased the content of resistant starch, and significantly decreased in vitro starch digestibility in CSSB; these effects were likely due to the joint inhibitory effect of tannins and ferulic acid on starch digestibility. Interestingly, the sorghum bran breads scored higher or similar to control in sensory color preference and overall appearance, but lower on most textural and mouthfeel attributes.

CONCLUSION

Sorghum bran addition significantly increased the antioxidant activity of CSSB and significantly decreased starch digestibility. Moreover, the color and appearance properties were maintained or improved. However, the sensorial textural attributes were negatively impacted by the sorghum bran substitutions. Strategies to improve the texture of bran-fortified breads would likely enhance their consumer acceptability. © 2024 Society of Chemical Industry.

Structural, physicochemical, and digestive properties of enzymatic debranched rice starch modified by phenolic compounds with varying structures

The physicochemical properties of starch and phenolic acid (PA) complexes largely depend on the effect of non-covalent interactions on the microstructure of starch. However, whether there are differences and commonalities in the interactions between various types of PAs and starch remains unclear. The physicochemical properties and digestive characteristics of the complexes were investigated by pre-gelatinization of 16 structurally different PAs and pullulanase-modified rice starches screened. FT-IR and XRD results revealed that PA complexed with debranched rice starch (DRS) through hydrogen bonding and hydrophobic interaction. Benzoic/phenylacetic acid with polyhydroxy groups could enter the helical cavities of the starch chains to promote the formation of V-shaped crystals, and cinnamic acid with p-hydroxyl structure acted between starch chains in a bridging manner, both of which increased the relative crystallinity of DRS, with DRS-ellagic acid increasing to 20.03 %. The digestion and hydrolysis results indicated that the acidification and methoxylation of PA synergistically decreased the enzyme activity leading to a decrease in the digestibility of the complexes, and the resistant starch content of the DRS-vanillic acid complexes increased from 28.27 % to 71.67 %. Therefore, the selection of structurally appropriate PAs can be used for the targeted preparation of starch-based foods and materials.

Structural changes of rice starch-anthocyanins complexes (V-type) and its impact on gut microbiotas and potential metabolic pathways during in vitro fermentation

This study explored the differences in the in vitro fermentation properties of rice starch (RS) and rice starch-anthocyanins complexes (RS-A). Structural characterization suggested that RS and RS-A complexes showed a V-type crystalline structure. The degree of order (DO) and degree of double helix (DD) values of RS and RS-A complexes were enhanced after fermentation. Moreover, the RS-A complexes could improve the relative abundance of Bacteroidetes, Ruminococcaceae, and up-regulate gut microbiota diversity to maintain gut homeostasis. Relative abundance of potential metabolic pathways, such as energy metabolism, digestion system, and carbohydrate degradation overexpressed in the presence of RS-A complexes. The results demonstrated that the RS-A complexes had slower fermentation rates contributing to the transport of the formed short-chain fatty acid (SCFA) to the end of the colon and that the crystallinity might be a factor influencing the utilization of the starch matrix by the gut microbiota for SCFA formation.

Polyphenol recovery from sorghum bran waste by microwave assisted extraction: Structural transformations as affected by grain phenolic profile

Sorghum milling waste stream (bran), contains diverse phenolic compounds with bioactive properties. The study determined the potential of microwave assisted extraction (MAE) to recover the bran phenolic compounds. Red, white, and lemon-yellow pericarp sorghum brans were subjected to MAE and phenolic yield and structural transformation vs conventional extraction (control) assessed by UPLC-MS/MS, Folin-Ciocalteu and Trolox equivalent antioxidant capacity methods. Phenols yield increased from 3.7-20.3 to 12.6-75.5 mg/g, while antioxidants capacity increased average 3.3X in MAE extracts vs controls. Hydroxycinnamic acids increased most dramatically (3.0-32X) in MAE extracts (0.08-2.64 to 2.57-8.01 mg/g), largely driven by release of cell-wall derived feruloyl- and coumaroyl-arabinose. MAE hydrolyzed flavonoid glycosides into aglycones, and depolymerized condensed flavonoid heteropolymers into flavanones, flavanols and (deoxy)anthocyanidins. Thus, MAE dramatically enhances yield of valuable phenolics from sorghum bran waste, but also alters the phenolic profile in ways that may influence their chemical and biological properties.

Persimmon leaf polyphenols as potential ingredients for modulating starch digestibility: Effect of starch-polyphenol interaction

The interaction mode between persimmon leaf polyphenols (PLP) and corn starch with different amylose content and its effect on starch digestibility was studied. Results of iodine binding test, TGA, and DSC revealed that PLP interacted with starch and reduced the iodine binding capacity and thermal stability of starch. High amylopectin corn starch (HAPS) interacted with PLP mainly via hydrogen bonds, since the FT-IR of HAPS-PLP complex showed higher intensity at 3400 cm-1 and an obvious shift of 21 cm-1 to shorter wavelength, and the chemical shifts of protons in 1H NMR and the shift of C-6 peak in 13C NMR of HAPS moved to low field with the addition of PLP. Results of 1H NMR also showed the preferential formation of hydrogen bonds between PLP and OH-3 of HAPS. Different from HAPS, PLP formed V-type inclusion complex with high amylose corn starch (HAS) because XRD of HAS-PLP complex showed characteristic feature peaks of V-type inclusion complex and C-1 signal in 13C NMR of PLP-complexed HAS shifted to low field. Interaction with PLP reduced starch digestibility and HAS-PLP complex resulted in more resistant starch production than HAPS-PLP complex. To complex PLP with starch might be a potential way to prepare functional starch with slower digestion.

Interactions between corn starch and lingonberry polyphenols and their effects on starch digestion and glucose transport

This study investigated the interaction mechanism between corn starch (CS) and lingonberry polyphenols (LBP) during starch gelatinization, focusing on their effects on starch structure and physicochemical properties. Moreover, it explored the effect of this interaction on starch digestion and glucose transport. The results indicated that LBP interacted non-covalently with CS during starch gelatinization, disrupted the short-range ordered structure of starch, decreased gelatinization enthalpy of starch, and formed a dense network structure. Furthermore, the incorporation of LBP remarkably reduced the digestibility of CS. In particular, the addition of 10 % LBP decreased the terminal digestibility (C∞) from 77.87 % to 60.43 % and increased the amount of resistant starch (RS) by 21.63 %. LBP was found to inhibit α-amylase and α-glucosidase in a mixed manner. Additionally, LBP inhibited glucose transport in Caco-2 cells following starch digestion. When 10 % LBP was added, there was a 34.17 % decrease in glucose transport compared with starch digestion without LBP. This study helps establish the foundation for the development of LBP-containing starch or starch-based healthy foods and provides new insights into the mechanism by which LBP lowers blood glucose.

Structural characteristics and in vitro starch digestibility of oil-modified cooked rice with varied addition manipulations

Lipid has crucial applications in improving the quality of starchy products during heat processing. Herein, the influence of lipid modification and thermal treatment on the physicochemical properties and starch digestibility of cooked rice prepared with varied addition manipulations was investigated. Rice bran oil (RO) and medium chain triglyceride oil (MO) manipulations were performed either before (BC) or after cooking (AC). GC-MS was applied to determine the fatty acid profiles. Nutritional quality was analyzed by quantifying total phenolics, atherogenic, and thrombogenic indices. All complexes exhibited higher surface firmness, a soft core, and less adhesive. FTIR spectrum demonstrated that the guest component affected some of the dense structural attributes of V-amylose. The kinetic constant was in the range between 0.47 and 0.86 min-1 wherein before mode presented a higher value. The lowest glucose release was observed in the RO_BC sample, whereas the highest complexing index was observed in the RO_AC sample, indicating that the dense molecular configuration of complexes that could resist enzymatic digestion was more critical than the quantity of complex formation. Despite the damage caused by mass and heat transfer, physical barrier, intact granule forms, and strengthened dense structure were the central contributors affecting the digestion characteristics of lipid-starch complexes.

Formation and Application of Starch-Polyphenol Complexes: Influencing Factors and Rapid Screening Based on Chemometrics

Understanding the nuanced interplay between plant polyphenols and starch could have significant implications. For example, it could lead to the development of tailor-made starches for specific applications, from bakinag and brewing to pharmaceuticals and bioplastics. In addition, this knowledge could contribute to the formulation of functional foods with lower glycemic indexes or improved nutrient delivery. Variations in the complexes can be attributed to differences in molecular weight, structure, and even the content of the polyphenols. In addition, the unique structural characteristics of starches, such as amylose/amylopectin ratio and crystalline density, also contribute to the observed effects. Processing conditions and methods will always alter the formation of complexes. As the type of starch/polyphenol can have a significant impact on the formation of the complex, the selection of suitable botanical sources of starch/polyphenols has become a focus. Spectroscopy coupled with chemometrics is a convenient and accurate method for rapidly identifying starches/polyphenols and screening for the desired botanical source. Understanding these relationships is crucial for optimizing starch-based systems in various applications, from food technology to pharmaceutical formulations.

Preparation of catechin-starch nanoparticles composites and its application as a Pickering emulsion stabilizer

Starch is a biopolymer commonly used for nanoparticle synthesis. Starch nanoparticles (SNPs) have potential as encapsulation agents and Pickering emulsion stabilizers. Here, we prepared SNPs by dry heating under mildly acidic conditions to encapsulate catechin. Catechin (30 mg) and SNPs (50-150 mg) were dispersed in distilled water and freeze-dried to prepare catechin-SNP composites. Isothermal titration calorimetry and Fourier-transform infrared spectroscopy revealed that the binding of catechin to SNP may involve spontaneous hydrogen bonding and hydrophobic interactions. SNPs exhibited encapsulation efficiency for catechin, with 100 % catechin retention when 150 mg of SNP was used to prepare the composites. The catechin-SNP composites had a particle size of 54.2-74.9 nm. X-ray diffraction analysis revealed the formation of small amounts of inclusion complexes in catechin-SNP composites. As the amount of SNPs added for encapsulation increased, the catechin encapsulated in the SNP composites exhibited higher water solubility and UV stability than the pure catechin. The catechin-SNP composite with 150 mg of catechin exhibited the highest contact angle (51.37°) and formed a stable emulsion without notable droplet size changes. Therefore, catechin-SNP composites improved the encapsulation efficiency, water-solubility, stability of catechins, and Pickering emulsion stability.

Optimization of ultrasonic conditions for improving the characteristics of corn starch-glycyrrhiza polysaccharide composite to prepare enhanced quality lycopene inclusion complex

In this study, based on response surface optimization of ultrasound pre-treatment conditions for encapsulating lycopene, the corn starch-glycyrrhiza polysaccharide composite (US-CS-GP) was used to prepare a novel lycopene inclusion complex (US-CS-GP-Lyc). Ultrasound treatment (575 W, 25 kHz) at 35 °C for 25 min significantly enhanced the rheological and starch properties of US-CS-GP, facilitating the preparation of US-CS-GP-Lyc with an encapsulation efficiency of 76.12 ± 1.76 %. In addition, the crystalline structure, thermal properties, and microstructure of the obtained lycopene inclusion complex were significantly improved and showed excellent antioxidant activity and storage stability. The US-CS-GP-Lyc exhibited a V-type crystal structure, enhanced lycopene loading capacity, and reduced crystalline regions due to increased amorphous regions, as well as superior thermal properties, including a lower maximum thermal decomposition rate and a higher maximum decomposition temperature. Furthermore, its smooth surface with dense pores provides enhanced space and protection for lycopene loading. Moreover, the US-CS-GP-Lyc displayed the highest DPPH scavenging rate (92.20 %) and enhanced stability under light and prolonged storage. These findings indicate that ultrasonic pretreatment can boost electrostatic forces and hydrogen bonding between corn starch and glycyrrhiza polysaccharide, enhance composite properties, and improve lycopene encapsulation, which may provide a scientific basis for the application of ultrasound technology in the refined processing of starch-polysaccharides composite products.

Insights into formation and stability mechanism of V7-type short amylose-resveratrol complex using molecular dynamics simulation and molecular docking

Pre-formed V-type amylose as a kind of wall material has been reported to carry polyphenols, while the interaction mechanism between V-type amylose and polyphenol is still elusive. In this work, the formation and stability mechanism of a V7-type short amylose-resveratrol complex was investigated via isothermal titration calorimetry, molecular dynamics, and molecular docking. The results presented that two stoichiometric ratios of resveratrol to short amylose were calculated to 0.120 and 0.800, and the corresponding main driving force was hydrogen bonding and hydrophobic interaction, respectively. The folding and unfolding conformation of V7-type short amylose chains appeared alternately during the simulation. Resveratrol tended to be bound in the short amylose helix between 40 ns and 80 ns to form a more stable complex. Hydrogen bonds between resveratrol molecule and O6 at the 22nd glucose molecule/O2 at the 24th glucose molecules and hydrophobic interaction between resveratrol molecule and glucose molecules (19th, 20th, 21st and 23rd) could be found.

Effects of purple potato anthocyanins on the in vitro digestive properties of starches of different crystalline types

This study explored the potential of purple potato anthocyanins (PPAs) in regulating the digestive properties of starches of various crystalline types. In vitro digestion experiments indicated that PPAs inhibit the hydrolysis of rice starch (A-type) better than that of garden pea starch (C-type) and potato starch (B-type). Further structural assessment of different PPA-starch systems showed that PPAs and starch likely interact through non-covalent bonds, resulting in structural changes. Microstructural changes observed in the starches were consistent with the in vitro digestion results, and the chain length and proportions of short/long chains in amylopectin molecules affected the binding strengths and interaction modes between PPAs and starch. Hence, the three starches differed in their PPA loading efficiency and digestibility. These discoveries contribute to a deeper understanding of the mechanisms underlying the inhibition of starch digestibility by PPAs. They can aid the formulation of value-added products and low-glycemic-index foods.

Interactions of hsian-tsao polysaccharide with corn starch to reduce its in vitro digestibility

Hsian-tsao polysaccharide (HP) with preferable bioactivities was used to produce starchy gel foods. This study elucidated how interactions of HP (0-0.6 %, w/v) with gelatinized corn starch (CS, 6 %, w/v) reduced in vitro digestibility of CS. The CS digestibility (82.85 %, without HP) was reduced to 68.85 % (co-heated) and 74.75 % (non-co-heated) when 0.6 % HP was added, demonstrating that HP reduced the CS digestibility to a larger extent under co-heating by both HP-CS interactions and inhibiting digestive enzyme activities by HP which was dominated under non-co-heating. Moreover, when co-heated, HP bonded to the amylose of CS via physical forces with a composite index of 21.95 % (0.4 % HP), impeded CS swelling and promoted CS aggregation with the average particle size increased to 42.95 μm (0.6 % HP). Also, the HP-CS complexes formed strong association network structures that increased their apparent viscosity and digestive fluid viscosity. Additionally, HP enhanced the short-range ordered structure and crystal structure of CS. These results evidenced that HP-CS interactions significantly reduced the CS digestibility by forming physical barriers, viscosity effects, and ordered structures, to hinder the enzymes from accessing starch matrices. This laid a foundation for applying HP to starchy foods with a low predicted glycemic index.

Insight into the dynamic molecular mechanism underlying the endogenous polyphenols inhibiting the in vitro starch digestion of highland barley noodles

Highland barley is a type of grain with slow-digesting characteristics. It is worth exploring the impact of non-starch components on starch digestion. In this study, four varieties of highland barley were used to investigate the impacts of endogenous polyphenols (EP) on the relationship between starch structure, physicochemical properties, and the time course digestibility of highland barley noodles. The results showed that EP removal decreased the proportion of long-chain amylopectin and disrupted the crystalline structure, while increasing the short-range ordered structure in the residue. Significant correlations indicated that these structural changes make starch more susceptible to thermal degradation and digestion, causing a 12.60%-52.00% increase in rapidly digestible starch (RDS) and a 12.70%-25.22% decrease in resistant starch (RS). These results revealed the internal factors that affect the slow digestion characteristics of highland barley noodles from the perspective of EP and provide important reference values for a slow digestion diet.

Stabilization and release of thymol in pre-formed V-type starch: A comparative study with traditional method

Recently, pre-formed V-type starch has become popular as a versatile carrier in encapsulation systems of containing starch-guest inclusion complexes (ICs). However, the differences in stabilizing and dissociating guests between ICs prepared by either the traditional method or the pre-formed "empty" helix method have not yet been elucidated. Here, starch-thymol ICs were prepared using the traditional high temperature-water method and the pre-formed method, covering different complexation temperatures and solvents, to compare the loading capacity, crystalline structure, thermal stability, and release properties. The highest content of thymol in ICs prepared by the pre-formed and the traditional method was 74.2 and 65.3 mg/g, respectively. Different from ICs prepared by the traditional method (V7-type crystal), ICs prepared by the pre-formed method mostly exhibited a V6a structure with larger crystallinities and a better short-range ordered structure. ICs prepared at 90 °C were type II complexes and efficiently protected thymol from rapid heat loss. A slow release was observed in both cases: about 45 % and 75 % of thymol were released from ICs prepared by the pre-formed and traditional methods, respectively, after two weeks of storage at 25 °C.

Multiscale structure changes and mechanism of polyphenol-amylose complexes modulated by polyphenolic structures

This study was designed to investigate the effect of polyphenolic structure on the interaction strength and process between polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) and amylose (AM). The results of Fourier transform infrared spectroscopy, isothermal titration calorimetry, X-ray photoelectron spectroscopy and molecular dynamic simulation (MD) suggested that the interactions between the three polyphenols and AM were noncovalent, spontaneous, low-energy and driven by enthalpy, which would be enhanced with increasing amounts of pyrogallol groups in the polyphenols. The results of turbidity, particle size and appearance of the complex solution showed that the interaction process between polyphenols and AM could be divided into three steps and would be advanced by increasing the number of pyrogallol groups in the polyphenols. At the same time, MD was intuitively employed to exhibit the interaction process between amylose and polyphenols, and it revealed that the interaction induced the aggregation of amylose and that the agglomeration degree of amylose increased with increasing number of pyrogallol groups at polyphenols. Last, the SEM and TGA results showed that TA/AM complexes had the tightest structure and the highest thermal stability (TA/AM˃EGCG/AM˃GA/AM), which could be attributed to TA having five pyrogallol groups.

Complexation temperature regulated the structure and digestibility of pea starch-gallic acid complexes during high pressure homogenization

Formation of starch-polyphenol complexes by high pressure homogenization (HPH) is widely used to reduce starch digestibility and delay the postprandial glycemic response, thereby benefiting obesity and associated metabolic diseases. This study investigated the effect of complexation temperature on multi-scale structures, physicochemical and digestive properties of pea starch-gallic acid (PS-GA) complexes during HPH process, while also elucidating the corresponding molecular mechanism regulating in vitro digestibility. The results demonstrated that elevating complexation temperature from 30 °C to 100 °C promoted the interaction between PS and GA and reached a peak complex index of 9.22 % at 90 °C through non-covalent binding. The enhanced interaction led to the formation of ordered multi-scale structures within PS-GA complexes, characterized by larger particles that exhibited greater thermal stability and elastic properties. Consequently, the PS-GA complexes exhibited substantially reduced digestion rates with the content of resistant starch increased from 28.50 % to 38.26 %. The potential molecular mechanism underlying how complexation temperature regulated digestibility of PS-GA complexes might be attributed to the synergistic effect of the physical barriers from newly ordered structure and inhibitory effect of GA against digestive enzymes. Overall, our findings contribute to the advancement of current knowledge regarding starch-polyphenol interactions and promote the development of functional starches with low postprandial glycemic responses.

Characterization of Various Noncovalent Polyphenol-Starch Complexes and Their Prebiotic Activities during In Vitro Digestion and Fermentation

This study explores the structural characterization of six noncovalent polyphenol-starch complexes and their prebiotic activities during in vitro digestion and fermentation. Ferulic acid, caffeic acid, gallic acid, isoquercetin, astragalin, and hyperin were complexed with sweet potato starch (SPS). The polyphenols exhibited high binding capacity (>70%) with SPS. A partial release of flavonoids from the complexes was observed via in vitro digestion, while the phenolic acids remained tightly bound. Molecular dynamics (MD) simulation revealed that polyphenols altered the spatial configuration of polysaccharides and intramolecular hydrogen bonds formed. Additionally, polyphenol-SPS complexes exerted inhibitory effects on starch digestion compared to gelatinized SPS, owing to the increase in resistant starch fraction. It revealed that the different complexes stimulated the growth of Lactobacillus rhamnosus and Bifidobacterium bifidum, while inhibiting the growth of Escherichia coli. Moreover, in vitro fermentation experiments revealed that complexes were utilized by the gut microbiota, resulting in the production of short-chain fatty acids and a decrease in pH. In addition, the polyphenol-SPS complexes altered the composition of gut microbiota by promoting the growth of beneficial bacteria and decreasing pathogenic bacteria. Polyphenol-SPS complexes exhibit great potential for use as a prebiotic and exert dual beneficial effects on gut microbiota.

Chemical structure and gelation characteristics of a purified gel derived from sword beans (Canavaliagladiata)

Herein, a new method was developed to obtain a crude extract from sword beans at a higher extraction efficiency. The crude extract formed a gel at 8 °C, which melted at 70 °C, and lyophilization of the purified gel produced a powder that could be dissolved in distilled water at a concentration of 7 % (w/w) or less. A 3 % powder solution gelled at 12 °C and melted at 60 °C. The infrared spectrum of the gel powder was consistent with that of starch. Furthermore, a 4-aminobenzoic acid ethyl ester-labeling analysis revealed that glucose was the constituent sugar in the powder, and the powder solution reacted strongly in a starch-iodine test. These observations confirmed that the gelling substance was starch. However, the melting and gelling temperatures were dissimilar to those of other starches frequently used in the food industry. Thus, our results provide valuable information for using sword bean starch as a novel food material.

Fabrication and release property of self-assembled garlic essential oil-amylose inclusion complex by pre-gelatinization coupling with high-speed shear

Our aim was to investigate the preparation of self-assembled garlic essential oil-amylose inclusion complexes (SGAs) using garlic essential oil (GEO) and corn starch (CS), and evaluated their release properties. SGAs were fabricated by pre-gelatinization coupling with high-speed shear at different GEO-CS mass ratios. When the mass ratio of GEO to pre-gelatinized corn starch was set at 15 % (SGA-15 %), with a fixed shear rate of 9000 rpm and a shear time of 30 min, the allicin content was 0.573 ± 0.023 mg/g. X-ray diffraction (XRD) results revealed a starch V-type crystalline structure in SGAs with peaks at 13.0°, 18.0°, and 20.0° (2θ). Fourier Transform Infrared (FTIR) spectra of SGAs displayed a shift in the characteristic peak of diallyl trisulfide from 987.51 cm-1 to 991.45 cm-1. Scanning electron microscope (SEM) images revealed that SGAs exhibited lamellar structures covered with small granules. SGAs exhibited higher residual mass (approximately 12 %) than other samples. The resistant starch content of SGAs increased from 10.1 % to 18.4 % as GEO contents varied from 5 % to 15 %. In vitro digestion tests showed that about 53.21 % of allicin remained in SGA-15 % after 8 h. Therefore, this dual treatment can be a new method for fabricating controlled-release inclusion complexes of guest molecules.

Improvement of in vitro digestibility and thermostability of debranched waxy maize starch by sequential ethanol fractionation

This study aimed to improve the in vitro digestibility and thermostability of debranched waxy maize starch (DWMS) by sequential fractionation. Waxy maize starch was debranched by pullulanase, followed by sequential precipitation through controlling the ratio of starch supernatants to ethanol at 1:0.5, 1:1, and 1:1.5 (v/v). Subsequently the structural, thermal, in vitro digestive properties of DWMS were investigated. In vitro digestion results showed that the secondary ethanol fractionation of 1:1 on the basis of the initial fractionation (1:0.5) induced a significant higher amount of slowly digestive starch (SDS, 30.0 %) and resistant starch (RS, 58.6 %) amongst all three fractions, along with the highest peak temperature (Tp, 106.4 °C) and the highest decomposition value (Td, 310.0 °C) in calorimetric (DSC) and thermogravimetry (TGA) measurements. Chain length distribution, surface morphology, and laser confocal micro-Raman spectroscopy (LCM-Raman) analyses revealed that medium (degree of polymerization, DP 13- 36) and long chains (DP ≥37) respectively constituting 72.0 % and 10.2 % of DWMS resulted in the formation of spheroidal crystallites with higher homogeneity and more ordered short-range structures. Overall, this work confirmed that ethanol fractionation is an efficient method for improving the in vitro digestibility and heat stability of waxy maize starch.

The interaction and physicochemical properties of the starch-polyphenol complex: Polymeric proanthocyanidins and maize starch with different amylose/amylopectin ratios

This study investigated the impact of polymeric proanthocyanidins (PPC) on the physicochemical characteristics of maize starch with varying amylose content, and their potential interaction mechanism. PPC with a lower content (1 %) reduced the viscoelasticity of the high amylose maize starch (HAM) system, inhibited amylose rearrangement, and enhanced its fluidity. However, excessive PPC restrained the interaction between PPC and amylose. In contrast to HAM, PPC improved the gelation ability of waxy maize starch (WAM) as PPC concentration was raised. PPC suppressed the recrystallization of starch during storage, and PPC had a superior inhibition influence on the retrogradation of WAM in comparison to HAM. This indicated that amylopectin was more likely to interact with PPC than amylose. Hydrogen bonds were the main driving force between PPC and starch chains, which was clarified by Fourier transform-infrared, nuclear magnetic resonance, X-ray diffraction, iodine bonding reaction, and dynamic light scattering data. Additionally, the mechanism of interaction between PPC and the two starch components may be similar, and variance in physicochemical attributes can be primarily credited to the percentage of amylose to amylopectin in starch.

Three anthocyanin-rich berry extracts regulate the in vitro digestibility of corn starch: Physicochemical properties, structure and α-amylase

This study aimed to compare the regulatory effects of blue honeysuckle anthocyanins (BHA), blueberry anthocyanins (BBA), and blackcurrant anthocyanins (BCA) on the in vitro digestibility of corn starch in terms of starch physicochemical properties and structure, as well as α-amylase inhibition. The results revealed that adding all three anthocyanins lowered digestibility in the following order: BHA > BCA > BBA. The terminal digestibility (C∞) decreased from 73.84 % to 57.3 % with the addition of 10 % BHA, while the resistant starch (RS) content increased from 4.39 % to 48.82 %. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis indicated that anthocyanins and starch interacted through noncovalent bonds. Differential scanning calorimetry (DSC) analysis showed that the gelatinization enthalpy was dramatically lowered in all three anthocyanin groups, with 10 % BHA producing a 38.58 % drop. Rheological property analysis showed that anthocyanins increased the apparent viscosity and modulus with starch. The interaction between anthocyanin and α-amylase was mainly through the formation of hydrogen bonds and hydrophobic forces. This research provides theoretical guidance for developing low glycemic index (GI) anthocyanin starch-based foods.

Synergistic modification of ultrasound and bamboo leaf flavonoid on the rheological properties, multi-scale structure, and in vitro digestibility of pea starch

In this study, the effect of ultrasonic treatment (UT), bamboo leaf flavonoid (BLF), ultrasonic treatment prior to bamboo leaf flavonoid (UT-BLF), and bamboo leaf flavonoid prior to the ultrasonic treatment (BLF-UT) on the rheological properties, multi-scale structure, and digestibility of pea starch (PS) were investigated. The morphology and crystal structure of starch granules were destroyed by UT, thereby promoting starch retrogradation and digestion. The binding between BLF and starch through hydrophobic interactions and hydrogen bonds inhibited the interaction between starch molecular chains and impaired their double helix structure, thus effectively retarding starch retrogradation. The anti-digestibility of starch was enhanced after synergistic treatment. Compared with single treatment, synergistic treatment increased the ordered structure and gelatinization enthalpy of starch. In comparison with the UT-BLF group, the viscoelastic and thermal stability of BLF-UT group were improved with the increase in ordered structure. This study could provide valuable information for PS modification.

The structural properties and resistant digestibility of maize starch-glyceride monostearate complexes

This study investigated the effects of pullulanase debranching on the structural properties and digestibility of maize starch (MS)-glyceryl monostearate (GMS) complexes. According to our results, the apparent amylose content of MS increased from 36.34 % to 95.55 % and complex index reached 93.09 % after 16 h of pullulanase debranching. The crystallinity of prepared MS-GMS complexes increased to 33.24 % with a blend of B-type and V-type crystals. The surface of prepared MS-GMS complexes granules emerged more small lamellar crystals tightly adhering to the surface of granules. The Fourier transforms infrared spectroscopy analysis showed that debranching pretreatment MS-GMS complexes exhibited higher levels of short-range orders structure. These results indicated that maize starch was favorable to form more ordered starch-lipid complexes structure after debranching pretreatment, which resulted in the restriction of starch hydrolysis. In vitro digestion data implied that resistant starch (RS) content increased with the extension of the debranching time, and the highest RS content (69.58 %) appeared with 16 h pullulanase debranching. This work suggests that debranching pretreatment could be an efficient way to produce ordered starch-lipid complexes with controllable structure and anti-digestibility.

Effect of proanthocyanidins from different sources on the digestibility, physicochemical properties and structure of gelatinized maize starch

The effect of proanthocyanidins (PAs) from Chinese bayberry leaves (BLPs), grape seeds (GSPs), peanut skins (PSPs) and pine barks (PBPs) on physicochemical properties, structure and in-vitro digestibility of gelatinized maize starch was investigated. The results showed that all PAs remarkably retarded starch digestibility, meanwhile, BLPs highlighted superiority in increasing resistant starch content from 31.29 ± 1.12 % to 68.61 ± 1.15 %. The iodine-binding affinity analysis confirmed the interaction between PAs and starch, especially the stronger binding of BLPs to amylose, which was driven by non-covalent bonds supported by XRD and FT-IR analysis. Further, we found that PAs altered the rheological properties, thermal properties and morphology structure of starch. In brief, PAs induced larger consistency, poorer flow ability, lower gelatinization temperatures and melting enthalpy change (ΔH) of starch paste. SEM and CLSM observation demonstrated that PAs facilitated starch aggregation. Our results indicated that PAs especially BLPs could be considered as potential additives to modify starch in food industry.

The antioxidant activity of polysaccharides: A structure-function relationship overview

Over the last years, polysaccharides have been linked to antioxidant effects using both in vitro chemical and biological models. The reported structures, claimed to act as antioxidants, comprise chitosan, pectic polysaccharides, glucans, mannoproteins, alginates, fucoidans, and many others of all type of biological sources. The structural features linked to the antioxidant action include the polysaccharide charge, molecular weight, and the occurrence of non-carbohydrate substituents. The establishment of structure/function relationships can be, however, biased by secondary phenomena that tailor polysaccharides behavior in antioxidant systems. In this sense, this review confronts some basic concepts of polysaccharides chemistry with the current claim of carbohydrates as antioxidants. It critically discusses how the fine structure and properties of polysaccharides can define polysaccharides as antioxidants. Polysaccharides antioxidant action is highly dependent on their solubility, sugar ring structure, molecular weight, occurrence of positive or negatively charged groups, protein moieties and covalently linked phenolic compounds. However, the occurrence of phenolic compounds and protein as contaminants leads to misleading results in methodologies often used for screening and characterization purposes, as well as in vivo models. Despite falling in the concept of antioxidants, the role of polysaccharides must be well defined according with the matrices where they are involved.

Starches modification with rose polyphenols under multi-frequency power ultrasonic fields: Effect on physicochemical properties and digestion behavior

As the main source of energy for human beings, starch is widely present in people's daily diet. However, due to its high content of rapidly digestive starch, it can cause a rapid increase in blood glucose after consumption, which is harmful to the human body. In the current study, the complexes made from edible rose polyphenols (ERPs) and three starches (corn, potato and pea) with different typical crystalline were prepared separately by multi-frequency power ultrasound (MFPU). The MFPU includes single-frequency modes of 40, 60 kHz and dual-frequency of 40 and 60 kHz in sequential and simultaneous mode. The results of the amount of complexes showed that ultrasound could promote the formation of polyphenol-starch complexes for all the three starches and the amount of ERPs in complexes depended on the ultrasonic parameters including treatment power, time and frequency. Infrared spectroscopy and X-ray diffraction indicated that ERPs with or without ultrasound could interact with the three starches through non-covalent bonds to form non-V-type complexes. Scanning electron microscopy showed that the shape of starches changed obviously from round/oval to angular and the surface of the starches were no longer smooth and appeared obvious pits, indicating that the ultrasonic field destroyed the structure of starches. In addition, compared to the control group, the in vitro digestibility study with 40/60 kHz sonication revealed that ultrasonic treatment greatly improved the digestive properties of the polyphenol-starch complexes by significantly increasing the content of resistant starch (20.31%, 17.27% and 14.98%) in the three starches. Furthermore, the viscosity properties of the three starches were all decreased after ERPs addition and the effect was enhanced by ultrasound both for single- and dual-frequency. In conclusion, ultrasound can be used as an effective method for preparing ERPs-starch complexes to develop high value-added products and low glycemic index (GI) foods.

Resistant starch formation mechanism of amylosucrase-modified starches with crystalline structure enhanced by hydrothermal treatment

The aim of this study was to reveal the underlying mechanism contributing towards the formation of resistant starch (RS) in amylosucrase-modified starches with crystalline structure enhanced by hydrothermal treatment. The branch chains of waxy corn starch were continuously elongated by amylosucrase, and the retrogradation of elongated starches with weight-average chain length (CL_w¯) of 27.0-37.6 yielded B-type retrograded starches (MSs) with crystallinity increasing from 33.1 % (MS-5) to 41.4 % (MS-30). Increasing the starch crystallinity improved the content of RS from 6.7 % of MS-5 to be as much as 41.0 % of MS-30. During the hydrothermal treatment, MS-5 with CL_w¯ of 27.0 favored the B → A allomorphic transition, leading to the decreased starch digestibility. Moreover, the hydrothermal treatment facilitated the assembly of double helices to increase starch crystallinity, which further increased the content of RS. The findings of the present study may assist the preparation of functional starches with controllable digestibility.

Complexation of starch and phenolic compounds during food processing and impacts on the release of phenolic compounds

Phenolic compounds can form complexes with starch during food processing, which can modulate the release of phenolic compounds in the gastrointestinal tract and regulate the bioaccessibility of phenolic compounds. The starch-phenolic complexation is determined by the structure of starch, phenolic compounds, and the food processing conditions. In this review, the complexation between starch and phenolic compounds during (hydro)thermal and nonthermal processing is reviewed. A hypothesis on the complexation kinetics is developed to elucidate the mechanism of complexation between starch and phenolic compounds considering the reaction time and the processing conditions. The subsequent effects of complexation on the physicochemical properties of starch, including gelatinization, retrogradation, and digestion, are critically articulated. Further, the release of phenolic substances and the bioaccessibility of different types of starch-phenolics complexes are discussed. The review emphasizes that the processing-induced structural changes of starch are the major determinant modulating the extent and manner of complexation with phenolic compounds. The controlled release of complexes formed between phenolic compounds and starch in the digestive tracts can modify the functionality of starch-based foods and, thus, can be used for both the modulation of glycemic response and the targeted delivery of phenolic compounds.

Complexing curcumin and resveratrol in the starch crystalline network alters in vitro starch digestion: Towards developing healthy food materials

Starch is an abundant and common food ingredient capable of complexing with various bioactive compounds (BCs), including polyphenols. However, little information is available about using native starch network arrangement for the starch-BCs inclusion. Herein, two BCs, curcumin, and resveratrol, were undertaken to delineate the role of different starch crystalline types on their encapsulation efficiency. Four starches with different crystalline types, botanical sources, and amylose content were examined. The results suggest that B-type hexagonal packing is necessary to encapsulate curcumin and resveratrol successfully. The increase in XRD crystallinity while maintaining the FTIR band at 1048/1016 cm^-1 suggests that BCs are likely entrapped inside the starch granule than attaching to the granule surface. A significant change in starch digestion is seen only for the B-starch complexes. Embedding BCs in the starch network and controlling starch digestion could be a cost-effective and valuable approach to designing and developing novel starch-based functional food ingredients.

Effect of tea polyphenols on the physicochemical, structural and digestive properties of modified high amylose corn starch

In this study, starch-polyphenol complexes (CES-TPS complexes) were prepared using various ratios (0%, 2%, 4%, 6%, 8%, and 10%, based on starch) of tea polyphenols (TPS) and high amylose corn starch (HACS) pretreated with starch branching enzyme (SBE). It was aimed to determine the effects of TPS on the physicochemical and structural properties and digestibility of the CES-TPS complexes. Scanning electron microscopy and laser particle size analysis showed that the addition of a moderate amount of TPS will reinforce interaction force, while excessive TPS will cause a loose structural morphology, leading to an increase in starch particle size. Thermal property analysis indicated that SBE pre-treatment decreased T_O, T_P and T_C of HACS, and the gelatinization temperature was further reduced after adding TPS. The digestion of CES-TPS complexes was investigated using an Artificial Gut analyzer; the predicted glycemic index of starch samples decreased with the addition of a low concentration of TPS (2-6%), while there was a significant increment in the pGI of starch samples when a high concentration of TPS (8-10%) was added. XRD analysis showed that the relative crystallinity of the CES-TPS complexes further increased to 21.91% and then decreased to 19.38% with the increase of TPS concentration. The ratios of 1047/1022 cm^-1 presented the opposite trend to that determined by FT-IR.

Stability of starch-proanthocyanidin complexes to in-vitro amylase digestion after hydrothermal processing

Proanthocyanidins (PA) form poorly digestible complexes with starch. The study examined amylase degradation mechanism and hydrothermal stability of starch-PA complexes. Sorghum-derived PA was complexed with wheat starch, reconstituted into flour (10% gluten added) and processed into crackers and pancakes. In vitro digestion profile of the complexes and products were characterized. The starch-PA complexes retained more (34-84%) fragments with degree of polymerization (DP) > 6,000 after 120 min digestion than controls (0-21%). Debranching further revealed higher retention of DP 11 - 30 chains in the digested starch-PA complexes than controls, suggesting amylopectin complexation contributed to reduced starch digestion. Starch-PA complexes retained reduced digestibility (50-56% higher resistant starch vs controls) in the cracker, but not pancake model. However, removing gluten from the pancake formulation restored the reduced digestibility of the starch-PA complexes. The starch-PA complexes are stable to hydrothermal processing, but can be disrupted by hydrophobic gluten proteins under excess moisture conditions.

Factors influencing the starch digestibility of starchy foods: A review

Starchy foods are a major energy source of the human diet, their digestion is closely related to human health. Most foods require lots of processing before eating, therefore, many factors can influence starch digestibility. The factors that affect the digestibility of starches have been widely discussed previously, but the extracted starches in those studies were different from those present within the actual food matrix. This review summarizes the factors influencing the starch digestibility in starchy foods. Endogenous non-starch components hinder the starch digestive process. Food ingredients and additives decrease starch digestibility by inhibiting the activity of digestive enzymes or hindering the contact between starch and enzymes. Storage induce the retrogradation of starch, decreasing the digestibility of foods. Therefore, preparing starchy foods with whole grains, processing them as little as possible, using food additives reasonably, and storage conditions may all be beneficial measures for the production of low GI foods.

Purple red rice bran anthocyanins reduce the digestibility of rice starch by forming V-type inclusion complexes

Purple red rice bran, a by-product of the rice polishing process, contained abundant anthocyanins. However, most of them were discarded resulting in a waste of resources. This study investigated the effects of purple red rice bran anthocyanin extracts (PRRBAE) on the physicochemical properties and digestive properties of rice starch and its mechanism of action. Infrared spectroscopy and X-ray diffraction indicated that PRRBAE could interact with rice starch through non-covalent bonds to form intrahelical V-type complexes. The DPPH and ABTS⁺ assays showed that PRRBAE could confer better antioxidant activity on rice starch. In addition, the PRRBAE could increase the resistant starch content and decrease the enzyme activities by changing the tertiary and secondary structure of starch-digesting enzymes. Further, molecular docking suggested that aromatic amino acids play a key role in the interaction of starch-digesting enzymes with PRRBAE. These findings will contribute to a better understanding of the mechanism of PRRBAE reducing starch digestibility, and to the development of high value-added products and low glycemic index (GI) foods.

An investigation into structural properties and stability of debranched starch-lycopene inclusion complexes with different branching degrees

Debranched starch (DBS) has great probability as carrier for bioactive ingredients, but effects of branching degree (DB) on the complex formation of starch remain unclear. This study investigated the potential of DBS with different DB to load lycopene and characterized the structural properties of inclusion complexes. Glutinous rice starch was debranched to get DBS with different molecular weights, where DBS with a branching degree of 11.42 % had the greatest encapsulation efficiency (64.81 %). SEM, particle size, and zeta-potential results showed that the complexes form stable spherical crystals through electrostatic interactions. The structures of complexes were resolved by FTIR, XRD, TGA, and 13C CP/MAS NMR analytical techniques, indicating that lycopene can be loaded on DBS by the self-assembly through hydrophobic and hydrogen bonding interactions. Degradation experiments revealed that retention of complexes was significantly higher than the unencapsulated one. Our study reveals the structural features of the complex between DBS and lycopene, providing theoretical guidance for developing and producing novel nutraceuticals.

Effect of protein-starch interactions on starch retrogradation and implications for food product quality

Starch retrogradation is a consequential part of food processing that greatly impacts the texture and acceptability of products containing both starch and proteins, but the effect of proteins on starch retrogradation has only recently been explored. With the increased popularity of plant-based proteins in recent years, incorporation of proteins into starch-based products is more commonplace. These formulation changes may have unforeseen effects on ingredient functionality and sensory outcomes of starch-containing products during storage, which makes the investigation of protein-starch interactions and subsequent impact on starch retrogradation and product quality essential. Protein can inhibit or promote starch retrogradation based on its exposed residues. Charged residues promote charge-dipole interactions between starch-bound phosphate and protein, hydrophobic groups restrict amylose release and reassociation, while hydrophilic groups impact water/molecular mobility. Covalent bonds (disulfide linkages) formed between proteins may enhance starch retrogradation, while glycosidic bonds formed between starch and protein during high-temperature processing may limit starch retrogradation. With these protein-starch interactions in mind, products can be formulated with proteins that enhance or delay textural changes in starch-containing products. Future work to understand the impact of starch-protein interactions on retrogradation should focus on integrating the fields of proteomics and carbohydrate chemistry. This interdisciplinary approach should result in better methods to characterize mechanisms of interaction between starch and proteins to optimize their food applications. This review provides useful interpretations of current literature characterizing the mechanistic effect of protein on starch retrogradation.

Electron beam irradiation pretreatment enhances the formation of granular starch-phenolics complexes

Starch-phenolics complex generated by the interaction between starch and phenolic acids had improved characteristics than the native starch, but the efficient preparation of such complex is still challenging. In this study, we proposed a new method for the preparation of starch-phenolics complexes under the pretreatment of electron beam irradiation (EBI). Four structurally similar monomeric phenolic acids including gallic acid (GA), 3,4-Dihydroxy-5-methoxybenzoic acid (3MGA), syringic acid (SA) and vanillic acid (VA), which naturally existed in Tartary buckwheat (TB) seeds, were complexed with native and EBI-pretreated TB starch. The results showed that the complexation between starch and 3MGA was the strongest, more than 30 mg of 3MGA was complexed with 1 g of starch. The complexation did not affect the particle morphology and A-type structure of starch, but changed the crystal structure order and promoted the strength of hydrogen bond, which may lead to the formation of granular complex. EBI pretreatment can significantly promote the complexation by enhancing hydrogen bonds as indicated by a broader band at 3500 ∼ 3100 cm^-1 in the FT-IR spectra. In addition, EBI pretreatment helped to build a tighter bond and higher crystallinity, increase the particle size and iodine binding capacity, and decrease turbidity to inhibit retrogradation of starch. The ¹H NMR of complexes indicated that EBI pretreatment could provide more accessibility for starch to interact with phenolics by creating a spacious microenvironment for ¹H (α1 → 4). Above all, EBI pretreatment enhanced the formations of starch-phenolics complexes.