NMR spectroscopy of starch systems

Preparation and properties of cationic starch-carrageenan‑sodium alginate hydrogels with pH and temperature sensitivity

In this study, cationic starch-carrageenan‑sodium alginate (CAS/CR/SA) hydrogels with different weight ratios of carrageenan and sodium alginate were prepared and their properties such as scanning electron microscopy (SEM), rheological properties, Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), and methylene blue adsorption test were measured. The results showed that the viscosity and the shear strain resistance of the CAS/CR/SA hybrid hydrogels positively correlated with their sodium alginate contents. The hybrid hydrogels with high carrageenan contents exhibited a high energy storage modulus (G') and a high loss modulus (G"). The swelling and methylene blue adsorption experiments showed that the CAS/CR/SA hydrogels had pH and temperature sensitivity. The hydrogels reached adsorption equilibrium in 12 h (alkaline conditions) and 24-36 h (acidic conditions). The adsorption kinetics of the hybrid hydrogels showed that their adsorption process was mainly controlled by chemisorption and that adsorption was exothermic (ΔH° < 0).

Deuteration of non-labile protium in starch: Biosynthesis and characterisation from yeast-derived starch granules

Deuterium labelling of the non-labile protium atoms in starch granules has been achieved for the first time, by growing genetically modified yeast on deuterated media. Mass spectrometry of the glucose monomers from digested starch showed 44 % average deuteration of the non-labile protium when grown on partially deuterated raffinose (with average deuteration 48 %); yielding starch with 26 % average overall deuteration. Non-labile deuteration was also demonstrated using D2O solvent in the culture medium. Solid-state NMR revealed that deuteration was not evenly distributed across the monomer, being highest at the C6 carbon and lowest at the C1 carbon. SANS revealed two structural features at q = 0.05 Å-1 and 0.4 Å-1, the first corresponding to a lamellar repeat of approximately 12-13 nm while the latter is consistent with B-type crystalline polymer packing. Furthermore, solvent contrast variation SANS analysis yielded a contrast match point of 66 mol% D2O indicative of approximately 30-35 % average deuteration of the bulk granules, consistent with mass spectroscopy. When coupled with the more traditional process of exchange of labile protium in the hydroxyl groups by D2O solvent exchange, the biosynthesis of highly deuterated starch opens new opportunities for neutron scattering experiments involving multicomponent starch-based systems.

Dietary fiber-rich Lentinula edodes stems influence the structure and in vitro digestibility of low-moisture extruded maize starches

Low-moisture extrusion (LME) can be used to improve the utilization of dietary fiber-rich Lentinula edodes stems (LES). The incorporation of dietary fiber can affect heat-induced interactions of starch molecules, which are critical for modifying starch characteristics via LME. In this work, a blend of LES and maize starch was extruded into a product at low moisture (30 %, w/v). The structure, physicochemical properties, and in vitro digestibility of extruded maize starches were investigated at different LES levels. The results showed that low levels (<7 %) of LES increased the crystallinity of LME-produced starch, while high levels (>7 %) did not. Because of the LES's soluble to insoluble dietary fiber ratios, the increased crystallinity of LES-added starch led to greater molecular ordering and the formation of an elastic gel after LME. At a suitable LES level (~3 %), highly crystallized starches were resistant to enzymolysis and had a high proportion of resistant starch. The obtained findings would contribute to a better understanding of how dietary fiber-rich LES affects starch extrusion and provide an alternative use for boosting the value of LES by-products.

Novel Pseudo-Two-Dimensional 19F NMR Spectroscopy for Rapid Simultaneous Detection of Amines in Complex Mixture

Rapid detection of amines in complex mixtures presents a significant challenge. Here, we introduce a novel nuclear magnetic resonance (NMR) method for amine detection utilizing a probe with two fluorine atoms in distinct chemical environments. Upon interaction with an amine, the probe generates two atomic resonance peaks, which are used to create coordinates, revealing fluorine chemical shifts on the 19F NMR spectroscopy. This innovative approach allows for the clear distinction of amine signals in a two-dimensional plane. This method has been effectively employed in analyzing amines in pharmaceuticals and amino acids in Ophiopogon japonicus and dry white wine, providing a robust and general approach for amine analysis.

The multi-scale structure and in vitro digestive kinetics of underutilized Chinese seedless breadfruit starch

In our previous research, the significant difference of physiochemistry properties for underutilized starches was showed between Chinese seedless breadfruit species and the other species. Based on this, the multiscale structure and digestion kinetics of Chinese seedless breadfruit of Spice and Beverage Research Institute species (SBS) and Xinglong species (XBS) was further researched. The SBS exhibited higher α-1,6 glycosylic bond content, free side-chain groups content, double-helix content, homogeneity, molecular weight, and V-type polymorphism, and fewer amorphous content, blocklet sizes, and a smaller semi-crystalline lamella thickness than XBS. Additionally, SBS showed higher final viscosity, pasting temperature, and gelatinization enthalpy than those of XBS. Consequently, SBS display lower rate constant (0.73 h-1) and glycemic index (65.17) than those of XBS (0.86 h-1 and 73.95). The anti-digestibility mechanism was revealed by the structure-digestibility relationship. It was found that resistant starch of SBS and XBS were significantly higher than those of starch from American and African species. This indicated that Chinese breadfruit starch could be considered as a good source of resistant starch, regulating glycemic index. In summary, XBS and XBS could be considered as a well source of resistant starch to make foods for preventing or improving type II diabetes or hyperlipemia.

Insights into impact of chlorogenic acid on multi-scale structure and digestive properties of lotus seed starch under autoclaving treatment

The interaction between polyphenols and starch is an important factor affecting the structure and function of starch. Here, the impact of chlorogenic acid on the multi-scale structure and digestive properties of lotus seed starch under autoclaving treatment were evaluated in this study. The results showed that lotus seed starch granules were destroyed under autoclaving treatment, and chlorogenic acid promoted the formation of loose gel structure of lotus seed starch. In particular, the long- and short-range ordered structure of lotus seed starch-chlorogenic acid complexes were reduced compared with lotus seed starch under autoclaving treatment. The relative crystallinity of A-LS-CA complexes decreased from 23.4 % to 20.3 %, the value of R1047/1022 reduced from 0.87 to 0.80, and the proportion of amorphous region increased from 10.26 % to 13.85 %. In addition, thermal stability, storage modulus and loss modulus of lotus seed starch-chlorogenic acid complexes were reduced, indicating that the viscoelasticity of lotus seed starch gel was weakened with the addition of chlorogenic acid. It is remarkable that chlorogenic acid increased the proportion of resistant starch from 58.25 ± 1.43 % to 63.85 ± 0.96 % compared with lotus seed starch under autoclaving treatment. Here, the research results provided a theoretical guidance for the development of functional foods containing lotus seed starch.

Synthesis and release studies on amylose-based ester prodrugs of fenamic acid NSAIDs

Aim: To achieve colon-targeted release of mefenamic acid from its ester-linked amylose prodrugs.Materials & methods: The prodrug was characterized by 1H NMR and IR spectroscopy. Drug activation and release profile was studied in enzyme enriched simulated physiological media via UV-vis spectroscopy and was validated with HPLC analysis. ELISA assay was employed for evaluating the % inhibition of COX-1 and COX-2 inhibition at different concentrations of the prodrug preincubated with ester and/ or amylose hydrolyzing enzymes. SEM studies further validated the performance of the prodrug under simulated physiological conditions.Results: Pancreatin was essential for the prodrug activation in SIM to make the ester bonds in prodrug vulnerable to hydrolysis by esterase. This evidence was confirmed by drug release studies, HPLC analysis, ELISA assay and SEM investigation where the ester conjugated prodrug showed marked stability in physiological media only to get activated in the presence of amylose degrading enzyme.Conclusion: Ester linked amylose-mefenamic acid conjugate showed both enzyme responsive activation and release in SIM.

Research on electron beam irradiation in the multiscale structure of starch and its related applications: A review

Electron beam irradiation (EBI), as a typical "green" emerging technology, can effectively alter the functional properties of starch by influencing its microstructure. This alteration enables starch to meet the current demands of consumers and the market for "health food." This paper reviews studies on modifying various starches using EBI and describes the changes in microstructure, physicochemical properties, and functional properties induced by this method. Additionally, the effects of EBI on starch-containing food products are discussed, along with issues to be addressed and research gaps in the synergistic treatment of modified starch. It is noted that the source, irradiation dose, and irradiation time all influence the effectiveness of starch modification. Given the characteristics of EBI technology, integrating physical, chemical, and biological modification methods can optimize the modification process and enhance efficiency. This technology can potentially diversify modified starch varieties and expand their applications. Furthermore, there remains significant research potential in producing modified starch using EBI technology and applying it to the food industry.

The mediation mechanism of calcium ions on black bean type 3 resistant starch: Metabolomics, structure characteristics and digestibility

The type 3 resistant starch (RS3) is beneficial for blood glucose management. A high quality RS3 was provided and its formation mechanism after calcium ion (Ca2+) treatment was investigated in this study. The metabolomics, structure and digestion properties were evaluated. Metabolomics was performed by untargeted UHPLC-Q-TOF/MS, and a total of 11 significantly different metabolites was found. The NMR, ATR-FTIR, and XRD results showed that the degree of double helix decreased from 5.34 to 1.07, crystallinity decreased from 33.58 % to 19.88 %, and the amorphous region increased from 69.76 % to 78.33 %. Large particle polymers were observed by SEM on the granule surface of starch with Ca2+ treatment. Digestion test showed that Ca2+ increased the RS3 from 9.70 % to 22.26 %. The result indicated that Ca2+ induced the formation of chelates between Ca2+ and -OH, promoted the RS3 content and regulated carbohydrate metabolism. The study provided theoretical basis for producing low-glycemic black bean foods.

Comparative study on the structure characterization and activity of RS5 made from Canna edulis native starch and high-amylose corn starch

In this study, the high amylose corn starch and Canna edulis native starch were compounded with lauric acid and fermented by human fecal inoculation in vitro. Changes in beneficial metabolite profile and microbiota composition were evaluated. The structural properties showed that both NS-12C and HAMS-12C formed V-shaped crystals under the same preparation method, but NS-12C had a higher composite index and resistance content than HAMS-12C. At the end of fermentation, the starch-lauric acid complexes prepared from the two types of starch significantly promoted the formation of short-chain fatty acids and the contents of acetic acid, butyric acid and valeric acid produced by NS-12C were higher than those of HAMS-12C(p>0.05). HAMS-12C and NS-12C both increased the relative abundance of Blautia. Notably, NS-12C also increased the relative abundance of beneficial bacteria Bifidobacterium and Meganomas, while HAMS-12C did not. These results suggested that this effect may be related to starch type and provide a basis for designing and producing functional foods to improve intestinal health in Canna edulis native starch.

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.

Probing structural features in potato starch granules at moderate hydration through the modelling of 1H->13C polarization transfer kinetics

The structural arrangement of starch polymers in presence of water is known to impact the functional properties of starchy products. In this study, the hydration of potato starch granules was investigated at the molecular level through various 1H->13C polarization transfer solid-state Nuclear Magnetic Resonance (ss-NMR) experiments. The impact of increasing the water content from 12.3 % to 45.9 % was assessed using 13C Cross Polarization Magic Angle Spinning (CPMAS), Variable Contact Time (VCT-CPMAS), Variable Spin Lock (VSL-CPMAS), and T One Rho QUEnching (TORQUE) NMR sequences. Of these, VCT-CPMAS proved to be the most promising. When applied with an optimal number of contact times, it enabled the application of several mathematical models that provided detailed insights into the structuring of protons in the hydrated potato starch granules. At low hydration (12.3 %), the models enabled various structural domains to be distinguished, which we suggest are associated with helical and amorphous structures. At moderate hydration (45.9 %), we tested two fitting models. Two pools of protons were revealed, corresponding to loosely ordered structures on the scale of tens of nanometers. These findings suggest varying water distribution during starch hydration and are likely to indicate variable hydration levels in the multilamellar amorphous structures of starch granules.

Butyryl group distribution modulates the structure and properties of butyrylated maize starch focused on amylose contents

In this study, four types of maize starch with different amylose contents (3 %, 25 %, 40 %, and 70 %) were used to prepare butyrylated starches. Based on amylose contents, the influence of butyryl group distribution on the structure, thermal and digestive properties of butyrylated maize starch was investigated. The butyrylation reaction mainly substituted butyryl groups on amylose, and the butyryl groups were most easily substituted for the hydroxyl group at the C6 position. The degree of substitution of butyrylated starch reached its maximum when the amylose content was 40 %, and the degree of substitution did not correlate linearly with the amylose content. The butyrylation reaction increased the surface roughness, decreased the crystallinity, enthalpy value and molecular weight of native starch granules, resulting in a decrease in the degree of internal order of the starch and inducing the rearrangement of the amylose molecular chains in the amorphous region of the starch. The combination of the amylose content and the substitution of butyryl groups on amylose affected the digestibility of starch and ultimately increased its resistance. The Pearson correlation coefficient further confirmed the correlation between the distribution of butyryl groups and the structure and properties of butyrylated starch.

Effects of starch multiscale structure on the physicochemical properties and digestibility of Radix Cynanchi bungei starch

Radix Cynanchi bungei (RCb) contains 40-70 % starch, yet little is known about the structure and properties of RCb starch. In this study, the multiscale structure of two cultivars of RCb starch (YW201501 and BW201001) were characterized, and the effects of starch structure on its physicochemical properties were investigated. The differences in physicochemical properties of RCb starch were influenced by its multiscale structure. The starch granules were round and irregular polygon, with sizes ranging between 2 and 14 μm. YW201501 had a higher amylose (21.81 %) and lipid (0.96 %) content, molecular weight (59.5 × 106 g/mol), and A chain proportion (27.5 %), and a lower average granule size (6.14 μm), amylopectin average chain length (19.7), and B3 chain proportion (10.3 %). Both starches were B-type crystalline, with higher crystallinity (26.3 %) and R1047/1022 (0.74) for YW201501, resulting in large gelatinization enthalpy. In addition, the higher peak viscosity and larger retrogradation degree of YW201501 were correlated to its higher amylose content. In vitro digestibility revealed that the low rapidly digestible starch and high resistant starch of BW201001 were related to the fine structure of starch. YW201501 and BW201001 had a medium glycemic index (62.6-66.0) with potential for processing into healthy starchy foods.

Effects of glycerol content on structure and molecular motion in thermoplastic starch-based nanocomposites during long storage

Thermoplastic starch-based nanocomposites with varying glycerol content and montmorillonite as a nanofiller were studied using dynamic-mechanical analysis (DMA), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) during one-year storage. DMA results showed that starch-rich and glycerol-rich domains were present in the samples and during storage for up to one year the content of the amorphous phase decreased and molecular mobility changed. 13C NMR and XRD measurements confirmed that ordered structures were formed during storage and its content was larger for samples with higher glycerol content and increased with the storage time. The data obtained from deconvolutions of 1H broad line NMR spectra indicate increased overall molecular mobility in the samples up to four months of storage, while after nine months the trends were opposite. Lower free water content compared to the total water content in the samples determined according to deconvoluted 1H MAS (magic-angle spinning) NMR spectra indicated that a part of water molecules was immobilized in the ordered structures.

Probing covalent and non-covalent interactions between vanillic acid and starch and their effects on digestibility by solid-state NMR

Intermolecular interactions play a significant role on the physicochemical properties and digestibility of starchy foods. This study investigated the covalent and non-covalent interactions between vanillic acid (VA) and porous starch (PS) as well as their effects on digestibility using solid-state NMR. VA-PS conjugates and mixtures were synthesized and characterized using 1H NMR, FT-IR, SEM and XRD. 13C NMR peaks at 163 ppm and FT-IR signals at 1737 cm-1 indicated the formation of ester bond in VA-PS conjugates. While differences between covalent and non-covalent interactions were also probed by solid-state NMR. The specific binding sites between VA and PS were subsequently identified by 1H13C HETCOR spectra before assessing the impact of covalent and non-covalent interactions on digestibility through an in vitro digestion test. The results revealed 13C chemical shifts of about 2.0 ppm, indicating stronger intermolecular interactions, and reduced mobility of the VA-PS conjugate due to its covalent bonding. Overall, the results showed that the VA-PS conjugate, characterized by stronger covalent interactions, exhibited superior effects in inhibiting starch digestibility compared with non-covalent interactions.

Non-Traditional Starches, Their Properties, and Applications

This review paper focuses on the recent advancements in the large-scale and laboratory-scale isolation, modification, and characterization of novel starches from accessible botanical sources and food wastes. When creating a new starch product, one should consider the different physicochemical changes that may occur. These changes include the course of gelatinization, the formation of starch-lipids and starch-protein complexes, and the origin of resistant starch (RS). This paper informs about the properties of individual starches, including their chemical structure, the size and crystallinity of starch granules, their thermal and pasting properties, their swelling power, and their digestibility; in particular, small starch granules showed unique properties. They can be utilized as fat substitutes in frozen desserts or mayonnaises, in custard due to their smooth texture, in non-food applications in biodegradable plastics, or as adsorbents. The low onset temperature of gelatinization (detected by DSC in acorn starch) is associated with the costs of the industrial processes in terms of energy and time. Starch plays a crucial role in the food industry as a thickening agent. Starches obtained from ulluco, winter squash, bean, pumpkin, quinoa, and sweet potato demonstrate a high peak viscosity (PV), while waxy rice and ginger starches have a low PV. The other analytical methods in the paper include laser diffraction, X-ray diffraction, FTIR, Raman, and NMR spectroscopies. Native, "clean-label" starches from new sources could replace chemically modified starches due to their properties being similar to common commercially modified ones. Human populations, especially in developed countries, suffer from obesity and civilization diseases, a reduction in which would be possible with the help of low-digestible starches. Starch with a high RS content was discovered in gelatinized lily (>50%) and unripe plantains (>25%), while cooked lily starch retained low levels of rapidly digestible starch (20%). Starch from gorgon nut processed at high temperatures has a high proportion of slowly digestible starch. Therefore, one can include these types of starches in a nutritious diet. Interesting industrial materials based on non-traditional starches include biodegradable composites, edible films, and nanomaterials.

Micro-magnetic resonance imaging of ex vivo mouse embryos with potato starch suspension

Potato starch suspension (PSS) holds promise as a solution to issues, such as air bubbles and specimen motion, associated with micro-magnetic resonance imaging (micro-MRI) of ex vivo embryos. Here, we present a protocol for using PSS when scanning specimens with micro-MRI. We describe steps for preparing samples and potato starch with phosphate-buffered saline. We then detail steps for specimen immersion and micro-MRI scanning. This protocol will enable micro-MRI of not only embryos but also other specimens, such as insects. For complete details on the use and execution of this protocol, please refer to Tsurugizawa et al.1.

Digestibility, structural and physicochemical properties of microcrystalline butyrylated pea starch with different degree of substitution

In this study, microcrystalline butyrylated pea starch (MBPS) with higher contents of resistant starch (RS) was synthesized via esterification with butyric anhydride (BA) using microcrystalline pea starch (MPS) as the raw material. With the addition of BA, the new characteristic peaks appeared at 1739 cm^-1 and 0.85 ppm obtained from FTIR and ¹H NMR, respectively, and increased with the higher degree of BA substitution. Moreover, an irregular shape of MBPS, such as condensed particles and more cracks or fragments, had been observed by SEM. Further, the relative crystallinity of MPS increased then native pea starch and decreased with the reaction of esterification. MBPS had higher decomposition onset temperature (T_o) and temperature of maximum decomposition (T_max) with increasing DS values. Simultaneously, an increasing trend RS content from 63.04 % to 94.11 % and a decreasing trends in rapidly digestible starch (RDS) and slowly digestible starch (SDS) contents of MBPS were recorded with increasing DS values. MBPS samples showed higher production capacity of butyric acid ranging from 553.82 μmol/L to 892.64 μmol/L during the fermentation process. Compared with MPS, the functional properties of MBPS were significantly improved.

Perspectives on Novel Technologies of Processing and Monitoring the Safety and Quality of Prepared Food Products

With the changes of lifestyles and rapid growth of prepared food industry, prepared fried rice that meets the consumption patterns of contemporary young people has become popular in China. Although prepared fried rice is convenient and nutritious, it has the following concerns in the supply chain: (1) susceptible to contamination by microorganisms; (2) rich in starch and prone to stall; and (3) vegetables in the ingredients have the issues of water loss and discoloration, and meat substances are vulnerable to oxidation and deterioration. As different ingredients are used in prepared fried rice, their food processing and quality monitoring techniques are also different. This paper reviews the key factors that cause changes in the quality of prepared fried rice, and the advantages and limitations of technologies in the processing and monitoring processes. The processing technologies for prepared fried rice include irradiation, high-voltage electric field, microwave, radio frequency, and ohmic heating, while the quality monitoring technologies include Raman spectral imaging, near-infrared spectral imaging, and low-field nuclear magnetic resonance technology. These technologies will serve as the foundation for enhancing the quality and safety of prepared fried rice and are essential to the further development of prepared fried rice in the emerging market.

A review on the identification of transgenic oilseeds and oils

Transgenic technology can increase the quantity and quality of vegetable oils worldwide. However, people are skeptical about the safety of transgenic oil-bearing crops and the oils they produce. In order to protect consumers' rights and avoid transgenic oils being adulterated or labeled as nontransgenic oils, the transgenic detection technology of oilseeds and oils needs careful consideration. This paper first summarized the current research status of transgenic technologies implemented at oil-bearing crops. Then, an inspection process was proposed to detect a large number of samples to be the subject rapidly, and various inspection strategies for transgenic oilseeds and oils were summarized according to the process sequence. The detection indicators included oil content, fatty acid, triglyceride, tocopherol, and nucleic acid. The detection technologies involved chromatography, spectroscopy, nuclear magnetic resonance, and polymerase chain reaction. It is hoped that this article can provide crucial technical reference and support for staff engaging in the supervision of transgenic food and for researchers developing fast and efficient monitoring methods in the future.

Probing molecular interactions of amylose-morin complex and their effect on antioxidant capacity by 2D solid-state NMR spectroscopy

Interaction of polyphenols and starch significantly governed the further applications on polyphenol-starchy foods. Elucidation of inter-molecular interaction is, however, a challenge because conventional characterizations could not detect the change of micro-environment caused by weak interactions. Herein, a facile strategy for molecular detection of amylose-polyphenol interactions was reported using two-dimensional solid-state NMR spectroscopy. Amylose-morin complex was prepared and characterized using ¹H NMR, FT-IR, DSC, XRD and SEM. Significantly, variation of chemical shifts, splitted peaks and peak width, monitored by ¹³C CP/MAS and ¹H NMR spectra, identified the strong inter-molecular interaction and binding sites. Furthermore, correlated signals from ¹H-¹³C HETCOR confirmed the binding sites of interactions. These findings confirmed the interaction was inter-molecular hydrogen bonds, which generated between hydroxy-3,5,7 of morin and hydroxy groups of amylose. Besides, DPPH radical scavenging and reducing power assay indicated inter-molecular hydrogen bonds are not strong enough to interfere antioxidant capacity of morin.

Enhancing traceability of wheat quality through the supply chain

With the growing global population, the need for food is expected to grow tremendously in the next few decades. One of the key tools to address such growing food demand is minimizing grain losses and optimizing food processing operations. Hence, several research studies are underway to reduce grain losses/degradation at the farm (upon harvest) and later during the milling and baking processes. However, less attention has been paid to changes in grain quality between harvest and milling. This paper aims to address this knowledge gap and discusses possible strategies for preserving grain quality (for Canadian wheat in particular) during unit operations at primary, process, or terminal elevators. To this end, the importance of wheat flour quality metrics is briefly described, followed by a discussion on the effect of grain properties on such quality parameters. This work also explores how drying, storage, blending, and cleaning, as some of the common post-harvest unit operations, could affect grain's end-product quality. Finally, an overview of the available techniques for grain quality monitoring is provided, followed by a discussion on existing gaps and potential solutions for quality traceability throughout the wheat supply chain.

Unveiling the retrogradation mechanism of a novel high amylose content starch-Pouteria campechiana seed

The research of starch retrogradation have been attracting interest. Thereby, the long-term retrogradation mechanism (0-21 days) of Pouteria campechiana seed starch (PCSS) was investigated. The results showed that crystal type was changed from A- to B + V-type during retrogradation. The retrogradation PCSS (RPCSS) exhibited faster retrogradation rate and more compact internal ultra-structure compared to rice, wheat and maize starch. Pearson correlation indicated that, as retrogradation days increased, values of α-1,4-glycosidic bond, A chains, double helix, V-type polymorphism, Mw, relative crystallinity (Rc) and short-range order gradually significantly increased, and B1 chains, B3 + chains values gradually significantly dropped (p < 0.05). These inferred an increasing peak temperature and compactness of morphology with increasing retrogradation days. Compared to native starch, RPCSS α-1.4-glycosidic bond was increased, which indicated that its quick molecules degradation including decreased Mw, B3 + chains, Rc, semicrystalline order, and ΔH. These might provide a theoretical direction for preparation of starch-basis food.

Effects of extrusion on physical properties of glutinous rice and its application in the improvement of quality characteristics of glutinous rice products

This study investigated the effects of extrusion on the physical properties of glutinous rice and addressed the challenges associated with its hardened texture and reduced taste in glutinous rice products by adding extruded glutinous rice to assess their anti-retrogradation effect compared with different improvers. Glutinous rice flour with different gelatinization degrees was obtained by changing the initial moisture content of glutinous rice grains before extrusion, and their physicochemical properties and the effect of adding them to rice products were analyzed. Results showed that with the increase in moisture content, the viscosity, water absorption index of extruded glutinous rice flour, and product viscosity increased, while the gelatinization degree, water solubility index, and product elasticity decreased, and the hardness of the rice products showed a trend of first decreasing and then increasing. Twenty percent moisture content of glutinous rice products showed the best properties mentioned above. The effects of adding different improvers on retrogradation degree, quality characteristics, microstructure, and moisture migration of glutinous rice products were analyzed by texture profile analysis, sensory evaluation, scanning electron microscopy, and low-field nuclear magnetic resonance. It was found that soybean polysaccharides, xanthan gum, and extruded glutinous rice flour had better anti-retrogradation effects, while colloid and soybean polysaccharides provided a tighter and more three-dimensional internal structure to the rice products. Our study showed that extruded glutinous rice flour had good anti-retrogradation properties and little effect on flavor and taste, but it would increase the roughness and viscosity of the products, which had advantages and disadvantages compared with other improvers.

Exploring the roles of amylopectin in starch modification with Limosilactobacillus reuteri 121 4,6-α-glucanotransferase via developed methods

Limosilactobacillus reuteri 121 4,6-α-glucanotransferase (GtfBΔN) modifies starch by cleaving (α1 → 4) linkages and introducing non-branched (α1 → 6) linkages to produce functional starch derivatives. Research has mainly focused on GtfBΔN converting amylose (linear substrate), whereas the conversion of amylopectin (branched substrate) has not been studied in detail. In this study, we used GtfBΔN to understand amylopectin modification and performed a set of experiments to analyze this modification pattern. The donor substrates were segments from the non-reducing ends to the nearest branch point in amylopectin as shown from the results of the chain length distribution of GtfBΔN-modified starches. Decreased and increased contents of β-limit dextrin and reducing sugars, respectively, during the incubation of β-limit dextrin with GtfBΔN indicated that the segments from the reducing end to the nearest branch point in amylopectin act as donor substrates. Dextranase was involved in the hydrolysis of the GtfBΔN conversion products of three different substrates groups, maltohexaose (G6), amylopectin, and G6 plus amylopectin. No reducing sugars were detected, therefore, amylopectin was not used as an acceptor substrate, and no non-branched (α1 → 6) linkages were introduced into it. Thus, these methods provide a reasonable and effective approach to studying GtfB-like 4,6-α-glucanotransferase in analyzing the roles and contribution of branched substrates.

Enhanced compatibility and functionality of thermoplastic cassava starch blended PBAT blown films with erythorbate and nitrite

Improved miscibility between thermoplastic starch (TPS) and polybutylene adipate-co-terephthalate (PBAT) enhances processability and properties of TPS-based biodegradable plastic packaging. This research investigated compatibility and functionality of TPS/PBAT (50/50) blends with sodium nitrite and sodium erythorbate (1-5%) via blown film extrusion. Film morphology and mechanical and barrier properties were investigated. Sodium nitrite and sodium erythorbate improved processing efficiency of TPS, modified film flexibility and enhanced physical and chemical compatibility between TPS and PBAT matrices via hydrolysis, confirmed by ¹H NMR and ATR-FTIR analyses. These chemical reactions also affected thermal and phase transition behaviors. Increased starch granule dispersion caused smoother microstructure, resulting in higher oxygen barrier. Sodium nitrite and sodium erythorbate functionalized TPS/PBAT films reduced discoloration of packaged cured meat during storage at 4 °C for 9 days. These compounds provided extra functionality and improved compatibility between TPS and PBAT biodegradable plastic blends for novel and sustainable food packaging.

Pulsed electric field-assisted esterification improves the freeze-thaw stability of corn starch gel by changing its molecular structure

The influence of pulsed electric field (PEF) combined with octenyl succinic anhydride (OSA) on the freeze-thaw stability of corn starch gel was investigated. After five freeze-thaw cycles, the syneresis value of OSA starch treated with PEF-assisted esterification for 15 min was lower by 29.5 %, while that of OSA starch without PEF treatment was lower by 10.17 %, compared to that of native starch. Low-field nuclear magnetic resonance data showed that the introduction of OSA groups greatly increased the water-holding capacity of starch. Results from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) showed that the PEF-assisted esterification markedly hindered the re-formation of the helical structure of starch during freeze-thaw cycles. Moreover, PEF-assisted esterification improved the viscoelastic properties of the starch gel. It is found that the freeze-thaw stability of the PEF-modified starch depends not only on the degree of substitution but also on the starch molecular fine structure. PEF-assisted OSA starch with a high degree of substitution, a low content of amylose, and a high content of short amylopectin chains were found to have high freeze-thaw stability. This study shows that PEF-assisted esterification is a promising technique that should be used for preserving the quality of frozen foods.

Temperature responsive crosslinked starch-kraft lignin macromolecule

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6-4.2 × 10⁵ g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films.

Utilization of potato starch suspension for MR-microimaging in ex vivo mouse embryos

Magnetic resonance (MR) microimaging of the mouse embryo is a promising tool to noninvasively investigate the microstructure of the brain of a developing mouse. The proton-free fluid is used for the liquid surrounding the specimen in MR microimaging, but the potential issue of image quality remains due to the air bubbles on the specimen and the retained water proton in the curvature of the embryo. Furthermore, the specimen may move during the scanning, resulting in motion artifact. Here, we developed the new concept of the ex vivo microimaging protocol with the robust method using the potato starch-containing biological polymers. Potato starch suspension with PBS significantly reduced T1 and T2 signal intensity of the suspension and strongly suppressed the motion of the embryo. Furthermore, potato starch-PBS suspension is stable for long-time scanning at room temperature. These results indicate the utility of potato starch suspension for MR microimaging in mouse embryos.

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.

Effect of dual modification with citric acid combined with ultrasonication on hydrolysis kinetics, morphology and structure of corn starch dispersions

Corn starch dispersions (CSD) were hydrolyzed with citric acid and compared with CSD co-treated with citric acid combined with ultrasonication for 1 to 18 days, which are designated as single modification (CSD-SM) and dual modification (CSD-DM), respectively. The logistic functions monitor the dynamics of the hydrolysis advance (%) of the CSD-SM and CSD-DM as a function of time, where the zones most vulnerable to the single-treatment and/or co-treatment of the corn starch granules (CSG) are the amorphous or disordered regions. The characterization results of CSD-DM suggest that the structural changes caused by dual modification affected the morphology, sequence, and microstructure of the CSG. The heterogeneous changes caused by the dual modification changed the configuration of the CSG, generating a kind of destemming of the amorphous lamellae (depolymerization), an increase in the percentage of relative crystallinity of the CSD-DM and an active rearrangement of the intralamellar chains that promoted the relative amount of double helix for 18 days of double modification. The synergistic effect of the dual modification for CSD by the sequential combination of a chemical treatment followed by a physical one improved the hydrolyzed advance by 12 %, the relative crystallinity by 10 %, and the promotion of double helices by 25 % during 18 days of co-treatment.

Effect of new type extrusion modification technology on supramolecular structure and in vitro glycemic release characteristics of starches with various estimated glycemic indices

Nowadays, the highly effective modified technology to starch with various digestibility is gaining interest in food science. Here, the interactions between glycemic release characteristics and fine supramolecular structure of cassava (ECS), potato (EPS), jackfruit seed (EJFSS), maize (EMS), wheat (EWS), and rice starches (ERS) prepared with improved extrusion modification technology (IEMS) were investigated. The crystalline structures of all extruded cooking starches changed from the A-type to V-type. IEMS-treated cassava, potato, and rice starches had broken α-1.6-glycosidic amylopectin (long chains). The others sheared α-1.4-glycosidic amylopectin. The molecular weight, medium and long chain counts, and relative crystallinity decreased, whereas the number of amylopectin short chains increased. The glycemic index (GI) and digestive speed rate constant (k) of ECS, EPS, EJFSS, and EWS were improved compared to those of raw starch. Although EMS and ERS had degraded molecular structures, their particle morphology changed from looser polyhedral to more compact with less enzymolysis channels due to the rearrangement of side chain clusters of amylopectin, leading to enzyme resistance. The starch characteristics of IEMS-treated samples significantly differed. EPS had the highest amylose content, medium chains, long chains, and molecular weight but lowest GI, relative crystallinity, and k. ERS showed the opposite results. Thus, IEMS may affect starches with different GIs to varying degrees. In this investigation, we provide a basis for wider applications of conventional crop starch in the food industry corresponding to different nutrition audience.

Physiochemical and thermal characterisation of faba bean starch

The structure and physicochemical properties of starch isolated from the cotyledon and hull of faba beans and from wheat (as reference) were examined using 16 different methods. The amylose content in faba bean cotyledon and hull starch was 32% and 36%, respectively, and that in wheat starch was 21%. The faba bean cotyledon and hull starch were structurally alike both displaying C-polymorphic pattern, a similar degree of branching and similar branch chain length distributions. Wheat starch had a significantly greater prevalence of short amylopectin chains (DP < 12) and a higher degree of branching. Granules in both faba bean starches exhibited surface cracks and were more homogenous in size than the smoother wheat starch granules. Gelatinisation temperature was higher for the faba bean starches, likely as an effect of high amylose content and longer starch chains delaying granular swelling. Cotyledon starch produced pastes with the highest viscosities in all rheological measurements, probably owing to larger granules. Higher prevalence of lipids and resistant starch reduced the viscosity values for hull starch. For all starches, viscosity increased at faster heating rates. During the rheological analyses, the samples were exposed to different instruments, heating rates and temperatures ranges, differing from standard rheological procedures, which could help predict how different processing techniques effect the final starch textures.

Graphical abstract

Molecular insight into the interactions between starch and cuminaldehyde using relaxation and 2D solid-state NMR spectroscopy

The interaction between cuminaldehyde and starch mainly governed the effect of further handling on food applications of cuminaldehyde. However, little information is available about the interactions of these components. We utilized relaxation and heteronuclear correlation (HETCOR) solid-state NMR spectroscopy to investigate the interaction between cuminaldehyde and porous starch at molecular level. We found that the interactions occurred mainly through hydrogen bonds. Cuminaldehyde molecules were restricted by starch, which resulted in the limitation of their movements and the longer ¹H T₁ relaxation time. Furthermore, the well resolved correlated peaks in 2D ¹H-¹³C HETCOR spectrum confirmed the formation of hydrogen bonds. The oxygen atoms at hydroxyl-2,3 of starch were the binding sites, which combined with hydrogens of cuminaldehyde. This present work not only afford a new approach to obtain a molecular understanding of interactions, but also expanded the application of solid-state NMR to investigation of the interaction on functional components.

Insights into the gelatinization of potato starch by in situ 1H NMR

The gelatinization of potato starch and the effect of NaCl on starch gelatinization were monitored successfully in situ by 1H NMR spectroscopy. Variable temperature (VT) 1H NMR measurement, from 316 K to 340 K, was conducted on a suspension of potato starch and deuterium water as well as a mixture of potato starch, NaCl and deuterium water. The hydration level of starch was determined with the increase of temperature. In the presence of NaCl, the initial gelatinization temperature of potato starch was decreased from 331 to 328 K. Meanwhile, in situ 1H NMR spectroscopy as a function of time was also carried out to monitor the gelatinization with a time resolution of 90 s per spectrum. Furthermore, the effect of using different processing methods during gelatinization, including varying the temperature or time duration, was investigated in detail. It was confirmed that protons from different groups of starch showed different accessibility for water during hydration of starch granules. In comparison with temperature, gelatinization time as the major factor for reaching complete gelatinization was confirmed. We expect that this research, as a continuing effort to apply NMR spectroscopy for characterizing starch, will pave a new way in the structural elucidation of starch.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Rheological Analysis of the Structuralisation Kinetics of Starch Gels

Using the method of dynamic–mechanical analysis, the structuralisation kinetics of condensed starch solutions, cooled down to the temperature of 20 °C, was investigated. A close correlation of spatial crosslinking with local processes of macromolecule associations was discovered. It was found that depending on the concentration intervals of starch solutions, equilibrium nodes of the spatial network assume the form of either single or double hexagonal structures made up of bispiral chain associates. The increase of gel crosslinking, together with the passage of time, is the result of increasing the node functionality of the spatial network.

Structure and properties of corn starch synthesized by using sulfobetaine and deoxycholic acid

Novel starch polymers (sulfobetaine-starch-deoxycholic acid) were first synthesized by grafting zwitterionic sulfobetaine and deoxycholic acid onto corn starch molecules. In order to explore the mechanism of modified starch, the chemical structure, morphological properties, thermal stability, and self-assembly performance of modified corn starch were determined. Preliminary structural characterization, using NMR, demonstrated that the glucose carbon C6 was the main etherification grafting site and C2 and C3 were the esterification grafting sites. This was confirmed using FT-IR to detect the presence of a new carbonyl signal around 1739 cm^-1. XRD, SEM, and PLM micrographs showed structural losses in the starch granule. Thermogravimetric analysis showed an increase in thermal stability with etherification and esterification in nature. Self-assembly performance analysis demonstrated that the polymer formed more thermodynamically stable micelles under highly diluted conditions. This work will help expand the space for starch application.

Preparation of rutin-loaded microparticles by debranched lentil starch-based wall materials: Structure, morphology and in vitro release behavior

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

Investigating the structure and self-assembly behavior of starch-g-VAc in starch-based adhesive by combining NMR analysis and multi-scale simulation

This work investigated the structure and self-assembly behavior of grafted starch (GS) prepared by grafting vinyl acetate (VAc) on the starch molecule. Our preliminary structure characterization, NMR, and quantum mechanical simulation demonstrated the C2 of the glucose unit as the main grafting site. The grafting frequency and chain length (starch, VAc) were calculated based on the result of gel permeation chromatography. Molecular dynamics simulation showed that, when compared with native starch, GS had less hydrogen bonding interaction, lower orderness, and higher extensibility, which were supported by the experimental results. In dissipative particle dynamics simulation, GS was shown to self-assemble into a core-shell structure (latex) and form a bridge structure with cross-linking interaction. The overall results indicate that chain entanglement and hydrogen bonding interaction of starch play a significant role in adhesive curing. This research provides a novel insight into the grafting and molecular interaction mechanism in the GS adhesive system.

Preparation of amylose-poly(methyl methacrylate) inclusion complex as a smart nanocarrier with switchable surface hydrophilicity

Amylose, as a linear biopolymer, tends to form helical inclusion complexes with suitable guest species. This is of great importance for a variety of applications, especially in the pharmaceutical and food industry. In this study, we propose an approach for the preparation of a novel inclusion complex with switchable surface hydrophilicity. For this purpose, amylose was first conjugated to ethylene diamine hydrophilic residues. Then, the short chains of the hydrophobic poly(methyl methacrylate, PMMA) were grafted onto the cavity of amylose through atom transfer radical polymerization (ATRP). According to CD spectroscopy results, the amylose-PMMA inclusion complexes displayed solvent-directed helical chirality inversion using either DMSO or water as a solvent. Fluorescence imaging, AFM and DLS techniques revealed the solvent-dependent surface hydrophilicity of the amylose-PMMA inclusion complex. Interestingly, its morphological studies displayed a central cavity, which makes it suitable for carrying cargoes in drug delivery applications. Obtaining the amylose-polymer inclusion complexes with tailorable hydrophilicity of both the exterior surface and the interior cavity can be of paramount importance for a wide variety of bio-applications.