Helical Conformation in Crystalline Inclusion Complexes of V-Amylose: A Historical Perspective

High selectivity molecularly imprinted polymer based on short amylose as bio-based functional monomers for selective extraction of λ-cyhalothrin

Nowadays, the development of sustainable molecularly imprinted polymers (MIPs) with high selectivity is still challenging due to the limitations of bio-based functional monomers. In this study, the highly selective and porous MIPs (LC-TMIPs) were designed and prepared on short amylose (SAM) as bio-based functional monomers, λ-cyhalothrin (LC) as a template molecule, and tetrafluoroterephthalonitrile as a rigid crosslinking agent. Static, dynamic, and selective adsorption experiments were conducted to investigate the adsorption performance. The results indicated that, compared to MIPs prepared using epichlorohydrin as flexible crosslinking agents, LC-TMIPs exhibited higher imprinting factor (3.93), selectivity (5.78), and adsorption capacity (35.79 mg g-1), as well as faster adsorption/desorption kinetics. The LC-TMIPs were used as sorbents for the selective determination of LC in both apple and cucumber samples by high-performance liquid chromatography. Under the optimal extraction conditions, the recoveries of the method reached 92.1-106.1 %, with a linear range of 1.5-30 ng g-1 and a detection limit of 0.5 ng g-1. The proposed preparation method of LC-TMIPs is expected to open a new way to prepare highly selective and sustainable MIPs for hydrophobic compounds.

Molecular modulating of amylopectin's structure promoted the formation of starch-unsaturated fatty acids complexes with controlled digestibility and improved stability to oxidation

In this study, waxy corn starch (WCS) was modified by amylosucrase and pullulanase, producing linear starch chains with elongated length that favored the complexation with unsaturated fatty acids (uFAs). Compared to native WCS, the amylosucrase-modified WCS with an average chain length of 47.8 was easier to form V-type complexes with oleic acid, while increasing the degree of unsaturation impeded the formation of V-type complexes. The pullulanase treatment hydrolyzed the branching points of amylosucrase-modified WCS and the linear starch chains could forme V-type complexes with oleic acid, linoleic acid, and linolenic acid, with V-type crystallinity decreasing from 38.2 % to 20.1 %. V-type complexes had a lower thermal stability than the B-type starch crystallites, and their peak melting temperature ranged from 67.2 to 79.0 °C. The content of resistant starch in the complexes was in the range of 21.8 %-40.9 % and the formation of V-type complexes decreased the susceptibility of uFAs to oxygen.

Potato starch/naringenin complexes for high-stability Pickering emulsions: Structure, properties, and emulsion stabilization mechanism

In this study, potato starch (PS)/naringenin (NAR) complex was prepared, and its properties and emulsification behavior were evaluated. The experimental results demonstrated that NAR successfully formed a complex with PS molecules through hydrogen bonds and other non-covalent interactions. The emulsifying capacity (ROV) of PS/NAR complex with 16 % composite ratio was 0.9999, which was higher than PS (ROV = 0.3329) (p < 0.05). Based on particle property analysis and molecular dynamics simulation, the mechanism of improving the emulsification performance might be the action of the benzene ring of NAR and intermolecular hydrogen bonding. In addition, the stability of the Pickering emulsions with PS/NAR complexes as emulgators was significantly improved. The emulsifying and rheological behavior of starch-based Pickering emulsions could be adjusted by changing the proportion of the complexes. Results demonstrated that the PS/NAR complexes might be a prospective stabilizer of Pickering emulsions based on starch material and might expand the use of PS in edible products.

Flavor-food ingredient interactions in fortified or reformulated novel food: Binding behaviors, manipulation strategies, sensory impacts, and future trends in delicious and healthy food design

With consumers gaining prominent awareness of health and well-being, a diverse range of fortified or reformulated novel food is developed to achieve personalized or tailored nutrition using protein, carbohydrates, or fat as building blocks. Flavor property is a critical factor in the acceptability and marketability of fortified or reformulated food. Major food ingredients are able to interact with flavor compounds, leading to a significant change in flavor release from the food matrix and, ultimately, altering flavor perception. Although many efforts have been made to elucidate how food matrix components change flavor binding capacities, the influences on flavor perception and their implications for the innovation of fortified or reformulated novel food have not been systematically summarized up to now. Thus, this review provides detailed knowledge about the binding behaviors of flavors to major food ingredients, as well as their influences on flavor retention, release, and perception. Practical approaches for manipulating these interactions and the resulting flavor quality are also reviewed, from the scope of their intrinsic and extrinsic influencing factors with technologies available, which is helpful for future food innovation. Evaluation of food-ingredient interactions using real food matrices while considering multisensory flavor perception is also prospected, to well motivate food industries to investigate new strategies for tasteful and healthy food design in response to consumers' unwillingness to compromise on flavor for health.

The Fluorescence Response of Four Crystalline Starches According to Ultrasound-Assisted Starch-Salicylic Acid Inclusions

Fluorescence has shown its superior performance in the fields of starch physicochemical properties, starch–based materials, and the interactions of starch with small molecules. However, it has not been well explored in the fluorescence characteristics of starch. Herein, the fluorescence properties of four crystalline starches (A–type tapioca starch, B–type potato starch, C–type pea starch, and V–type starch, prepared with corn starch and stearic acid) were investigated using salicylic acid (SA) as an indicator. The results of inverted fluorescence microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis indicated that SA could be included by starch. X–ray diffraction analysis further demonstrated that the inclusion of SA did not change the crystalline of the four crystal types of starches, which could provide a prerequisite for comparing the different fluorescence properties of the four crystal types of starches. Fluorescence enhancements of the four inclusions were 264.5 (B–type), 206 (C–type), 51.2 (V–type), and 28 (A–type). These results provide new insights for analyzing the fluorescence response of starch.

Inclusion of phenolic bioactives in high amylose corn starch for gastro-intestinal delivery

Starch is a staple food component with intricate architectures, some of which can be utilized as polysaccharidic delivery vehicles for bioactive compounds. This work describes the use of high amylose corn starch (HACS) to fabricate V-amylose inclusion complexes entrapping capsaicin or curcumin. In line with past studies, X-ray diffraction, differential scanning calorimetry, static laser scattering and scanning electron microscopy help affirm the formation of V6III-type complexes. Such HACS complexes entrap capsaicin and curcumin in structures with higher levels of crystallinity compared to HACS alone (14.61 ± 0.08%, 14.65 ± 0.08% vs. 10.24 ± 0.24%, respectively), high levels of encapsulation efficiency (88.77 ± 5.7% and 66.3 ± 0.99%, respectively) but without significant differences in colloid sizes between the various inclusion complexes (58.25 ± 1.34 μm or 58.98 ± 2.32 μm, respectively). In turn, in vitro gastro-intestinal digestion of HACS complexes with capsaicin or curcumin revealed both, phenolic bioactives significantly (p &lt; 0.05) attenuated the intestinal breakdown of HACS. Interestingly, this attenuated HACS digestibility was accompanied by high gastric retention of the payloads and their sustained release during 2 h of exposure to intestinal conditions. Altogether, this work presents starch-based delivery systems that can entrap phenolic bioactives, release the payload in the intestine and possibly attenuate starch breakdown (because of its increased crystallinity). Thus, this work offers a platform for infusing foods with bioactive phenolics and stall the breakdown of starch.

How to synchronously slow down starch digestion and retrogradation: A structural analysis study

Digestibility and retrogradation properties of starch are important for the nutrition and quality of starch-based foods. In this study, a new idea on the synchronous delay the starch digestion and retrogradation was proposed, and the regulation mechanism was explored from perspectives of structural evolution using ¹³C NMR, XRD and SAXS techniques as well as the molecular dynamics simulations. Results showed that the chestnut starch treated with hot extrusion and 8% catechins (HE-8% CA)## could reach highest anti-retrogradation rate (AR 76.63%) and lowest rapidly digestible starch content (RDS 64.55%) at day 24. The starch digestion was slowed down by increasing single/double helix, V-type crystallinity and compactness of aggregates, while retrogradation process was suppressed by inhibiting the packing of short-range ordered structure into long-range ordered structure. The hydrogen bonding and van der Waals forces were the main driving force for the interactions between flavonoid polyphenols and starch molecules. Overall, this study is instructive for further investigations on the synchronous modulation of functional properties of starch.

Resistant structure of extruded starch: Effects of fatty acids with different chain lengths and degree of unsaturation

This study investigated the formation mechanism of enzyme-resistant structures in extruded starch, specifically, fatty acid-starch complexes (FASCs). The effects of fatty acids (FAs) with different carbon-chain lengths (C12-C18) and degrees of unsaturation (C18:0-C18:2) on complex formation were evaluated, with fluorescence microscopy verifying complex formation. The complexed-lipid content and degree of relative crystallinity increased with the carbon-chain length and degree of FA unsaturation. FAs with fewer carbons were more likely to generate stable complexes (e.g., form II, melted at 100-120 °C), while FAs with more carbons tended to produce relatively unstable complexes (e.g., form I, melted at 80-100 °C). After reheating and cooling, a new amylose-lipid complex and an amylose-amylopectin network was formed in the unsaturated FASC samples, which restricted the penetration of enzymes into starch granules. A starch-linoleic acid complex exhibited the highest resistant starch content (15.7%) and lowest predicted glycaemic index (88.4).

NMR analysis and molecular dynamics conformation of α-1,6-linear and α-1,3-branched isomaltose oligomers as mimetics of α-1,6-linked dextran

The conformational preferences of several α-1,6-linear and α-1,3-branched isomalto-oligosaccharides were investigated by NMR and MD-simulations. Right-handed helical structure contributed to the solution geometry in isomaltotriose and isomaltotetraose with one nearly complete helix turn and stabilizing intramolecular hydrogen bonds in the latter by MD-simulation. Decreased helix contribution was observed in α-1,3-glucopyranosyl- and α-1,3-isomaltosyl-branched saccharide chains. Especially the latter modification was predicted to cause a more compact structure consistent with literature rheology measurements as well as with published dextranase-resistant α-1,3-branched oligosaccharides. The findings presented here are significant because they shed further light on the conformational preference of isomalto-oligosaccharides and provide possible help for the design of dextran-based drug delivery systems or for the targeted degradation of capsular polysaccharides by dextranases in multi-drug resistant bacteria.

Self-Assembly of Amphiphilic Amylose Derivatives in Aqueous Media

Six amylose derivative (C₁₂CMA) samples with hydrophobic dodecyl ether groups and hydrophilic sodium carboxymethyl groups were synthesized from an enzymatically synthesized amylose for which the weight-average molar mass is 50 kg mol^-1 to realize amylose-based amphiphilic polymer micelles. The degree of substitution of hydrophobic (DS_C12) and hydrophilic (DS_CM) groups ranges between 0.076 and 0.39 and between 0.35 and 1.83, respectively. Static and dynamic light scattering, small-angle X-ray scattering (SAXS), and fluorescence measurements with pyrene as a probe were carried out for the samples in 150 mM aqueous NaCl to characterize the higher-order structure in solution. The fluorescence from pyrene showed that all six samples have hydrophobic environment, while the hydrophobicity tends to increase with rising DS_C12. All six samples have high scattering intensity owing to the relatively large concentrated droplets ranging in the hydrodynamic radius from 50 to 110 nm, whereas the weight fraction of such large particles is substantially small except for the highest DS_C12 sample. Most polymer chains for relatively low DS_C12 of 0.076 were molecularly dispersed with a very small amount of large droplets. The dispersed chain has a slightly smaller helix pitch per residue and a more rigid main chain than those for amylose in dimethyl sulfoxide, suggesting that the amylosic main chain of C₁₂CMA has a helical structure with dodecyl groups at least locally. On the other hand, an anisotropic shaped micelle-like structure is only found for relatively high DS_C12 (0.23 and 0.39) samples, which was detected by the SAXS profile at a high scattering vector range. The micelle structure for high DS_C12 samples is consistent with the high chain stiffness.

Evaluation of Different Analysis Methods for the Encapsulation Efficiency of Amylose Inclusion Compound

Recently amylose has drawn much attention as a potential vehicle for the nanoencapsulation of different flavor molecules, and the encapsulation efficiency of the complex is an important index for the evaluation of its embedding effect. In this study, three different methods for assessing encapsulation efficiency of amylose-flavor complexes were compared. We chose heptanol and menthone as the flavor molecules, as both of them exhibit a typical odor. The complexes were prepared by the melting method, and their structures were characterized by XRD. In addition, the encapsulation efficiency was determined by thermal gravimetric analysis (TGA), potentiometric titration (PT), and headspace solid phase microextraction gas chromatography (HS-SPME-GC), respectively. The results showed that PT results were within the reported literature range while HS-SPME-GC seemed to overestimate the results and TGA results were the lowest. What is more, the operations of TGA and PT were relatively simple and the results were reproducible, while the HS-SPME-GC method displayed excellent high sensitivity. Therefore, PT method is the best method for assessing encapsulation efficiency of amylose-flavor complexes.

Microsecond kinetics in model single- and double-stranded amylose polymers

Amylose, a component of starch with increasing biotechnological significance, is a linear glucose polysaccharide that self-organizes into single- and double-helical assemblies. Starch granule packing, gelation and inclusion-complex formation result from finely balanced macromolecular kinetics that have eluded precise experimental quantification. Here, graphics processing unit (GPU) accelerated multi-microsecond aqueous simulations are employed to explore conformational kinetics in model single- and double-stranded amylose. The all-atom dynamics concur with prior X-ray and NMR data while surprising and previously overlooked microsecond helix-coil, glycosidic linkage and pyranose ring exchange are hypothesized. In a dodecasaccharide, single-helical collapse was correlated with linkages and rings transitioning from their expected syn and (4)C1 chair conformers. The associated microsecond exchange rates were dependent on proximity to the termini and chain length (comparing hexa- and trisaccharides), while kinetic features of dodecasaccharide linkage and ring flexing are proposed to be a good model for polymers. Similar length double-helices were stable on microsecond timescales but the parallel configuration was sturdier than the antiparallel equivalent. In both, tertiary organization restricted local chain dynamics, implying that simulations of single amylose strands cannot be extrapolated to dimers. Unbiased multi-microsecond simulations of amylose are proposed as a valuable route to probing macromolecular kinetics in water, assessing the impact of chemical modifications on helical stability and accelerating the development of new biotechnologies.

Characterization Methods for Starch-Based Materials: State of the Art and Perspectives

Improving starch-containing materials, whether food, animal feed, high-tech biomaterials, or engineering plastics, is best done by understanding how biosynthetic processes and any subsequent processing control starch structure, and how this structure controls functional properties. Starch structural characterization is central to this. This review examines how information on the three basic levels of the complex multi-scale structure of starch – individual chains, the branching structure of isolated molecules, and the way these molecules form various crystalline and amorphous arrangements – can be obtained from experiment. The techniques include fluorophore-assisted carbohydrate electrophoresis, multiple-detector size-exclusion chromatography, and various scattering techniques (light, X-ray, and neutron). Some examples are also given to show how these data provide mechanistic insight into how biosynthetic processes control the structure and how the various structural levels control functional properties.