Encapsulation of Ethylene Gas into Granular Cold-Water-Soluble Starch: Structure and Release Kinetics

Transformation of native starch into V-type granular starch through ethanol-aqueous heat treatment and its swelling behavior in cold water

The poor hydrophilicity of raw starch limits its applications, resulting in increased processing complexity. Ethanol-induced V-type granular starch (EVGS), a type of cold-water swelling starch, can be prepared through ethanol-aqueous heat treatment (EAHT). Four types of native starch with three crystalline structures were used to prepare EVGS. At 70 % ethanol, the preparation process was divided into temperature gradients to explore the EVGS formation process. X-ray diffraction (XRD), DSC (Differential Scanning Calorimetry) and non-isothermal kinetics analysis revealed three stages in the formation process: destruction of the native crystalline structure, formation of composite crystalline structure, and complete formation of V-type crystalline structure. The observed "blocklets" structure of EVGS suggested that the crystalline structure transformation might be based on this structural unit. A water phase gradient dispersion method was used to monitor the cold-water swelling behavior of EVGS: as the dispersion time increased, short-chain amylose leached first, followed by long-chain amylose, accompanied by the enhanced hydrophilicity of amylopectin, the "blocklets" structure limited EVGS swelling extent and prevented complete granules rupture, contributing to its cold paste stability. Overall, this study further elucidated the formation process and the multi-scale structure of EVGS and proposed an interpretation of cold-water swelling process for EVGS.

Eco-friendly one-pot hydrothermal synthesis of cyclodextrin metal-organic frameworks for enhanced CO2 capture

Polysaccharide-based metal-organic frameworks have attracted widespread attention due to their combination of the biocompatibility and flexibility of polysaccharides. Cyclodextrin are interesting bio-ligands in the construction of polysaccharide-based MOFs. Conventional methods for preparing cyclodextrin metal-organic frameworks (CD-MOFs) are often time-consuming and inefficient. In this study, cost-effective and environmentally friendly α- and β-CD-MOFs were successfully synthesized using a hydrothermal method, with optimized incubation time and solvent ratios. The materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N₂ adsorption/desorption measurements. The CO₂ adsorption mechanism was also examined using Fourier transform infrared spectroscopy (FTIR). The results demonstrated excellent thermal and cycling stability of the materials. The CO₂ uptake capacities of α- and β-CD MOF-K were 10.8 and 11.2 cm3/g, respectively. Additionally, the CD-MOFs showed strong selectivity for CO₂ over N₂. Given the straightforward operational procedures, safety characteristics, and mild reaction conditions of CD-MOFs, it is reasonable to conclude that they are promising candidates for use as CO₂ adsorption materials.

Starch-guest complexes interactions: Molecular mechanisms, effects on starch and functionality

Starch is a natural, abundant, renewable and biodegradable plant-based polymer that exhibits a variety of functional properties, including the ability to thicken or gel solutions, form films and coatings, and act as encapsulation and delivery vehicles. In this review, we first describe the structure of starch molecules and discuss the mechanisms of their interactions with guest molecules. Then, the effects of starch-guest complexes on gelatinization, retrogradation, rheology and digestion of starch are discussed. Finally, the potential applications of starch-guest complexes in the food industry are highlighted. Starch-guest complexes are formed due to physical forces, especially hydrophobic interactions between non-polar guest molecules and the hydrophobic interiors of amylose helices, as well as hydrogen bonds between some guest molecules and starch. Gelatinization, retrogradation, rheology and digestion of starch-based materials are influenced by complex formation, which has important implications for the utilization of starch as a functional and nutritional ingredient in food products. Controlling these interactions can be used to create novel starch-based food materials with specific functions, such as texture modifiers, delivery systems, edible coatings and films, fat substitutes and blood glucose modulators.

V-type granular starches prepared by maize starches with different amylose contents: An investigation in structure, physicochemical properties and digestibility

V-type granular starches (VGSs) were prepared via an ethanol-alkaline (EA) method using maize starch with different amylose contents, specifically, high amylose (HAM), normal maize starch (MS), and waxy maize starch (WS). The X-ray diffraction pattern of the native starch was completely transformed into a V-type pattern after the EA treatment, indicating a structural change in the starch granules. The VGSs prepared by HAM had highest relative crystallinity (31.8°), while the VGSs prepared by WS showed amorphous diffraction pattern. Excessive NaOH, however, would disrupt the formation of V-type structures and cause granular shape rupture. The quantity of double-helical structures, particularly those formed by amylopectin at the starch granules' periphery, significantly decreased. Conversely, single-helical structures formed by amylose increased. A notable rise in the relative crystallinity of V crystals. Four VGS samples, characterized by granular integrity, were chosen for the next investigation of physicochemical and digestive properties. VGS prepared from HAM exhibited higher granular integrity, lower cold-water swelling extent (59.0 and 161.0 cP), improved thermal stability (the value of breakdown as lower as 57.67 and 186.67 cP), and higher resistance to digestion (RS content was up to 10.38 % and 9.00 % higher than 5.86 % and 5.66 % of VGS prepared from WS and MS). The results confirmed that amylose content has a substantial impact on the microstructural and physicochemical properties of VGSs.

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.

Changes in the structure and functional properties of soybean isolate protein: Effects of different modification methods

Soybean protein isolate (SPI) is an important plant protein in food processing; however, its spherical structure prevents the exposure of its hydrophobic residues and affects its functional properties. In this study, we elucidate the effects of deamidation, phosphorylation, and glycosylation on the structure (Fourier-transform infrared spectroscopy, circular dichroism, fluorescence, and scanning electron microscopy) and functional properties (solubility, emulsifying activity index (EAI), and emulsifying stability index (ESI)) of SPI. The zeta potentials of the deamidated, phosphorylated, and glycosylated (DSPI, PSPI, and MSPI, respectively) samples decreased significantly (p < 0.05) relative to those of SPI. The functional properties of the modified SPI samples were improved, with MSPI-2 showing the best solubility (86.73 ± 0.34%), EAI (118.89 ± 0.73 m2/g), and ESI (273.33 ± 0.59 min). Moreover, the effects of the three modifications on the SPI functional properties increase in the order MSPI > PSPI > DSPI. These results provide a theoretical understanding the relationship between the modifications and SPI structure.

Pulsed Electric Field-Assisted Enzymatic and Alcoholic-Alkaline Production of Porous Granular Cold-Water-Soluble Starch: A Carrier with Efficient Zeaxanthin-Loading Capacity

In this study, porous starch was modified using pulsed electric field (PEF) pretreatment and alcoholic-alkaline treatment to prepare porous granular cold-water-soluble starch (P-GCWSS). The soluble porous starch has high adsorption capability and high cold water solubility, allowing effective encapsulation of zeaxanthin and improving zeaxanthin's water solubility, stability, and bioavailability. The physical and chemical properties of GCWSS and complex were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The results showed that the cold water solubility of the pulsed electric field-treated porous granular cold-water-soluble starch (PEF-P-GCWSS) increased by 12.81% compared to granular cold-water-soluble starch (GCWSS). The pulsed electric field treatment also increased the oil absorption of PEF-P-GCWSS was improved by 15.32% compared to porous granular cold-water-soluble starch (P-GCWSS). PEF-P-GCWSS was effective in encapsulating zeaxanthin, which provided a good protection for zeaxanthin. The zeaxanthin-saturated solubility in water of PPG-Z was increased by 56.72% compared with free zeaxanthin. The zeaxanthin embedded in PEF-P-GCWSS was able to be released slowly during gastric digestion and released rapidly during intestinal digestion.

Characteristics and ethylene encapsulation properties of V-type linear dextrin with different degrees of polymerisation

The objective of this research was to investigate the effects of preparation method on the characteristics and ethylene loading capacity of V-type linear dextrin (LD). LD with different degrees of polymerisation were obtained from debranched starch by gradient ethanol precipitation. X-ray diffraction (XRD) patterns of samples obtained by precipitation and anti-solvent precipitation presented A + V-type crystalline structure. However, the percentage of V-type structure of samples obtained by anti-solvent precipitation was significantly higher than for samples prepared by precipitation, which was further confirmed by nuclear magnetic resonance spectroscopy (NMR), and molecular dynamics simulation supported the XRD and NMR results. The ethylene encapsulation capabilities of samples fabricated by different methods were in range of 1.15-4.68 cm³/g. Ethylene release from V-type LD was a physical process at different storage temperatures, and the higher percentage of V-type structure, the slower release rate. Thus, a higher V-type structure content was beneficial for encapsulation of gaseous molecules.

Effect of multiple freezing/thawing cycles on the physicochemical properties and structural characteristics of starch from wheat flours with different gluten strength

The physicochemical properties and structural characteristics of starches from three wheat flours with different gluten strength (S-YM20, S-ZM27, and S-ZM366) during freezing/thawing (F/T) cycles were studied. After F/T treatment, the damaged starch content of these three starches all increased, and the lowest increment of damaged starch content after 8 F/T cycles was S-ZM366; the most serious distribution of particle surface concave hole and fracture was S-YM20, followed by S-ZM27 and S-ZM366; additionally, the results of solubility, swelling power, thermal stability and pasting properties indicated S-ZM366 exhibited the strongest resistance to F/T cycles. The differences of freezing resistance among the three starches were possibly ascribed to the differences in compositions, crystallinity and microstructure among these three starches. This study provides theoretical contribution to the development of frozen dough industry from the perspective of wheat variety.

Wheat gluten proteins phosphorylated with sodium tripolyphosphate: Changes in structure to improve functional properties for expanding applications

Poor solubility of wheat gluten proteins (WG) has negative impact on functional attributes such as gelation and emulsification, which limits it use in the food industry. In this study, WG underwent different degrees of phosphorylation using sodium tripolyphosphate (STP). Phosphoric acid groups were successfully incorporated in the WG via covalent bonding (C–N–P and C–O–P) involving hydroxyl and primary amino groups from WG. The introduction of phosphoric acid groups increased the negative charge of phosphorylation-WG, which caused the enhancement of electrostatic repulsion between proteins and reduced the droplet size in emulsions, thereby allowing proteins to be more efficiently dispersed in the solution system. The change of structure induced with phosphorylation improved hydration of protein, making the WG with higher solubility, thereby resulting in the improvement of its emulsification, foaming, thermal stability, and rheological properties. Therefore, WG can be modified by phosphorylation which caused an overall improvement of functional properties, thus facilitating the expansion of WG applications.

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Functional properties of WG were enhanced with phosphorylation (PP).

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The P2p at 133.1 eV and the bonds of C–O–P and C–N–P were found in PP-WG.

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Greater ζ-potential, solubility, viscosity, foaming in PP- WG.

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Phosphorylation increased WG thermal stability and gel properties.

Improving the cold water swelling properties of oat starch by subcritical ethanol-water treatment

The granular cold water swelling oat starch was prepared by subcritical ethanol-water, and the changes of properties and structure on oat starch were investigated. The oat starch was modified at the temperature of 95 °C and ethanol concentration of 48% and showed a higher cold water swelling ability of 22.58 g/g, whereas native oat starch was 6.73 g/g. Modified oat starch granule was kept intact, and it was swollen when dispersing in the water. The gelatinization enthalpy declined to 0 J/g. The surface of modified oat starch granules was honeycomb and porous observed by scanning electron microscope. The X-ray diffraction showed the A-type crystal decreased and the V-type crystal increased, and the result was quantitatively confirmed by solid-state ¹³C NMR spectroscopy. The ratio of 1047 cm^-1/1022 cm^-1 (determined by Fourier transform infrared spectroscopy) of modified oat starch was decreased. The molecular weight distribution of modified oat starch was slightly reduced, and the amylose content increased from 26.18% to 31.68%, and only a small amount of carbohydrates leached during the modification. Subcritical ethanol-water modification improved the cold water swelling ability of oat starch. The starch crystals changed from A-type to V-type provide a potential mechanism of subcritical ethanol-water modified oat starch.

Triggered and controlled release of active gaseous/volatile compounds for active packaging applications of agri-food products: A review

Gaseous and volatile active compounds are versatile to enhance safety and preserve quality of agri-food products during storage and distribution. However, the use of these compounds is limited by their high vapor pressure and/or chemical instability, especially in active packaging (AP) applications. Various approaches for stabilizing and controlling the release of active gaseous/volatile compounds have been developed, including encapsulation (e.g., into supramolecular matrices, polymer-based films, electrospun nonwovens) and triggered release systems involving precursor technology, thereby allowing their safe and effective use in AP applications. In this review, encapsulation technologies of gases (e.g., CO₂ , ClO₂ , SO₂ , ethylene, 1-methylcyclopropene) and volatiles (e.g., ethanol, ethyl formate, essential oils and their constituents) into different solid matrices, polymeric films, and electrospun nonwovens are reviewed, especially with regard to encapsulation mechanisms and controlled release properties. Recent developments on utilizing precursor compounds of bioactive gases/volatiles to enhance their storage stability and better control their release profiles are discussed. The potential applications of these controlled release systems in AP of agri-food products are presented as well.

Starch inclusion complex for the encapsulation and controlled release of bioactive guest compounds

The linear component of starch, especially amylose, is capable of forming inclusion complex (IC) with various small molecules. It could significantly modify the structure and properties of starch, and it could bring beneficial effects when bioactive compounds can be encapsulated. This review discusses the formation and characterization of the starch-guest IC and focuses on the recent developments in the use of starch ICs for the encapsulation and controlled release of bioactive guest compounds. A great number of guest compounds, such as lipids, aroma compounds, pharmaceuticals, and phytochemicals, were studied for their ability to be complexed with starch and/or amylose and some of the formed ICs were evaluated for the chemical stability improvement and the guest release regulation. Starch-guest ICs has a great potential to be a delivery system, as most existing studies demonstrated the enhancement on guest retention and the possibility of controlled release.

Preparation of V-type cold water-swelling starch by ethanolic extrusion

Ethanolic extrusion was used to prepare V-type cold water-swelling starch (VCWSS). Effects of extrusion temperature, ratio of starch to ethanol, and ratio of starch to water on the properties of VCWSS were investigated. It was found that when the extrusion temperature was 100 °C, the ratio of starch to ethanol was 1:0.30, and the ratio of starch to water was 1:0.60, the resulting VCWSS could quickly swell into paste in cold water with the highest V-type relative crystallinity (12.90%) and cold paste viscosity (3058 cP). Then the formation mechanism of cold paste viscosity of VCWSS was evaluated. The cold paste viscosity of VCWSS was positively related to its V-type relative crystallinity. Extrusion destroyed the granular morphology of native starch, and VCWSS particles exhibited rock-like morphology that is much larger than the granules of native starch. Formation of the V-amylose-ethanol complex during extrusion was the direct cause of rapid hydration of VCWSS.

In vitro fecal fermentation characteristics of bamboo shoot (Phyllostachys edulis) polysaccharide

The effects of Moso bamboo (Phyllostachys edulis) shoot polysaccharide (BSP) on the human gut microbiota composition and volatile metabolite components were investigated by in vitro fermentation. After fermentation for 48 h, BSP utilization reached 40.29% and the pH of the fermentation solution decreased from 6.89 to 4.57. Moreover, the total short-chain fatty acid concentration significantly (P < 0.05) increased from 13.46 mM (0 h) to 43.20 mM (48 h). 16S rRNA analysis revealed several differences in the gut microbiota community structure of the BSP-treated and water-treated (control) cultures. In the BSP group, the abundance of Firmicutes, Actinobacteria, and Proteobacteria was significantly increased, while that of Bacteroidetes and Fusobacteria significantly decreased. Moreover, the concentrations of benzene, its substituted derivatives, and carbonyl compounds in the volatile metabolites of the BSP-treated group decreased, while that of organic acids significantly increased after 48 h of fermentation. These results demonstrate that BSP improves gastrointestinal health.

Complexation between High-Amylose Starch and Binary Aroma Compounds of Decanal and Thymol: Cooperativity or Competition?

The use of combinations of aroma compounds is common in many food and cosmetic applications. To investigate the binding behavior between high-amylose maize starch and binary aroma combinations of decanal and thymol, starch-aroma inclusion complexes (ICs) were prepared by a one-step or two-step method with different concentrations and orders of addition. The thymol molecule induced the starch chain to form a larger helical cavity and was more likely to form hydrogen bonds with solvents. The encapsulation efficiency and loading efficiency of starch-thymol ICs were always higher than those of starch-decanal ICs, independent of the aroma concentration and addition order in binary aroma ICs. However, starch-decanal ICs prepared in the presence of thymol encapsulated more decanal than in the absence of thymol. The V_6I-type crystals formed by starch-decanal ICs and the V_6III-type crystals formed by starch-thymol ICs were both present in binary aroma ICs, resulting in a less-ordered structure and lower thermal transition temperatures. In summary, the complexation between binary aroma compounds and starch exhibited both cooperative and competitive binding behaviors. The synergistic effects between decanal and thymol provide guidance in enhancing the aroma encapsulation in starch carriers.

Preparation of V-type porous starch by amylase hydrolysis of V-type granular starch in aqueous ethanol solution

In this paper, a novel porous starch with a V-type crystalline structure and high adsorption capacity was obtained by enzymatic hydrolysis of V-type granular starch (VGS) in an aqueous ethanol solution. The effects of different starch concentrations, reaction temperatures, and ethanol concentrations on the microstructure, crystal morphology, crystallinity and adsorption properties of VGS before and after enzymatic hydrolysis were studied, and native normal corn starch (NNCS) and A-type porous starch (APS) prepared by enzymatic hydrolysis of NNCS were used as controls. The results showed that compared with NNCS, VGS was easier to hydrolyze with a higher hydrolysis degree and the corresponding V-type porous starch (VPS) had more and larger pores and thus showed better adsorption performance than APS. Under the same enzymatic hydrolysis time, temperature and rotation speed, VPS prepared with a starch concentration of 20%, reaction temperature of 140 °C and ethanol concentration of 70% showed an irregular spongelike porous structure, highest V-type relative crystallinity of 25.09%, highest oil adsorption capacity of 241.70% and water adsorption capacity of 805.59%.

Investigating the structural properties and in vitro digestion of rice flours

The physicochemical properties, swelling power, solubility, and digestibility of flour from four rice varieties (black, brown, white, and waxy rice flour) were analyzed. The results showed that the black and brown rice had high-amylose percentage (21.8% and 20.5%), a relatively low percentage of starch content (68.1% and 79.1%), and lower swelling power (6.6% and 7.6%) and solubility (13.5% and 15.7%), respectively. Waxy rice flour attributed to lower gelatinization temperatures and higher enthalpy values. Meanwhile, the brown, black, and white rice showed higher gelatinization temperature and lower enthalpy value. The black and brown rice flour exhibited lower pasting and viscosity values as compared to waxy rice flour. The results showed that all rice flour had an A-type X-ray diffraction pattern, and after cooking all rice flour showed V-type polymorphs except waxy rice flour. Brown and black rice flour after cooking have lower digestion rate than white rice and waxy rice flour, probably due to its lower expansion and solubility rates, and higher gelatinization temperature.

Side-by-side and exo-pitting degradation mechanism revealed from in vitro human fecal fermentation of granular starches

The in vitro fecal fermentation characteristics and microbiota responses to A- and B-type polymorphic starches as model (whole) foods enriched with resistant starch was investigated. Marked difference in fermentation rate as well as microbial genera was observed during fermentation, the degradation pattern as well as structural evolution during fermentation was almost similar. The final butyrate concentrations of both HAMS and PS (ca. 38 mM) were significantly higher than that of WMS (23 mM) and NMS (33 mM), which was associated with the increase of the relative abundance of Roseburia, Blautia, and Lachnospiraceae. A-type polymorphic starches, on the other hand had remarkably faster fermentation rate and promoted Megamonas. X-ray diffraction and size-exclusion chromatography of residual starch during the fermentation course demonstrated the "side-by-side" fermentation pattern. Based on the structural changes observed, we conclude that in vitro fecal fermentation of starch granules predominantly controlled by the surface features rather than the molecular and supra-molecular structure.

Effect of extrusion processing and addition of purple sweet potatoes on the structural properties and in vitro digestibility of extruded rice

Recently, extruded rice as a functional ingredient has been a hot area of research in food processing. In this study, extruded rice with purple sweet potato (ERPSP) was prepared. Moreover, the effects of extrusion and added purple sweet potato on the structure and in vitro digestibility of extruded rice were studied via numerous detection methods, such as scanning electron microscopy (SEM), water absorption index (WAI), water solubility index (WSI), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). SEM results showed that there were numerous pits and bubbles in the extruded rice. In particular, compared with raw rice, the WAI and WSI of ERPSP was higher, and the thermal properties also changed noticeably. The results of XRD and FT-IR spectroscopy showed that the semicrystalline structure of extruded rice changed from A-type to A + V-type mixture, and the relative crystallinity of extruded rice changed accordingly. In addition, a significantly lower equilibrium hydrolysis (C_∞) and kinetic constant (k) were observed in ERPSP. The novel rice product made from broken rice by extrusion processing and addition of the purple sweet potato exhibited improved structural properties and reduced digestibility, which increased the potential value and application of broken rice in the food industry.

Encapsulation of caffeine into starch matrices: Bitterness evaluation and suppression mechanism

In this study, caffeine (CA) was encapsulated into food-grade starch matrices, including swelled starch (SS), porous starch (PS), and V-type starch (VS). The bitterness of the microcapsules and suppression mechanisms were investigated using an electronic tongue, molecular dynamics (MD) simulation and the in vitro release kinetics of CA. All the CA-loaded microcapsules showed a lower bitterness intensity than the control. The MD results proved that the weak interactions between starch and CA resulted in a moderate CA release rate for SS-CA microcapsules. The PS-CA microcapsule presented the longest CA release, up to 40 min, whereas the VS-CA microcapsule completely released CA in 9 min. The CA release rate was found to be related to the microcapsule structure and rehydration properties. A low CA bitterness intensity could be attributed to a delay in the CA release rate and resistance to erosion of the microcapsules. The results of this work are valuable for improving starch-based microcapsules (oral-targeted drug-delivery systems) by suppressing the bitterness of alkaloid compounds.

Fermentation of prebiotics by human colonic microbiota in vitro and short-chain fatty acids production: a critical review

Prebiotics are known for their health benefits to man, including reducing cardiovascular disease and improving gut health. This review takes a critical assessment of the impact of dietary fibres and prebiotics on the gastrointestinal microbiota in vitro. The roles of colonic organisms, slow fermentation of prebiotics, production of high butyric and propionic acids and positive modulation of the host health were taken into cognizance. Also, the short-chain fatty acids (SCFAs) molecular signalling mechanisms associated with their prebiotic substrate structural conformations and the phenotypic responses related to the gut microbes composition were discussed. Furthermore, common dietary fibres such as resistant starch, pectin, hemicelluloses, β-glucan and fructan in context of their prebiotic potentials for human health were also explained. Finally, the in vitro human colonic fermentation depends on prebiotic type and its physicochemical characteristics, which will then affect the rate of fermentation, selectivity of micro-organisms to multiply, and SCFAs concentrations and compositions.

Encapsulation of menthol into cyclodextrin metal-organic frameworks: Preparation, structure characterization and evaluation of complexing capacity

Cyclodextrin (CD)-metal-organic frameworks (MOFs) are developed as a new type of food-acceptable multi-porous material, which shows a great potential for controlled volatile compound release. This study aimed to synthesize CD-MOFs from potassium nitrate, crystallized with α-cyclodextrin (α-CD), β-CD or γ-CD, and their complex capacities were further evaluated using menthol encapsulation. Compared with CD, all the CD-MOFs had highly ordered crystal structures and more regular shapes. β-CD-MOF showed better thermal stability, with an initial thermal degradation temperature of 253 °C, higher than the other two CD-MOFs. The CD-MOFs were used for menthol encapsulation and the resulting menthol concentration within the inclusion complexes (ICs) was determined. The menthol concentration in ICs followed the order: β-CD-MOF > β-CD > γ-CD-MOF > γ-CD > α-CD ≥ α-CD-MOF. The menthol content and encapsulation efficiency of β-CD-MOF were 21.76% (w/w) and 22.54% (w/w) respectively, significantly higher than those of other reported solid materials, such as amylose, CD and V-type starch.

Metal-Organic Framework Based on α-Cyclodextrin Gives High Ethylene Gas Adsorption Capacity and Storage Stability

Two metal-organic framework (MOF) materials, that is, α-cyclodextrin (α-CD)-MOF-Na and α-CD-MOF-K, were successfully synthesized and exhibited excellent adsorption capacity and storage stability for ethylene gas. The ethylene encapsulation capacity of α-CD-MOF-Na and α-CD-MOF-K reached 47.4 and 52.9% (w/w), respectively, which was significantly higher than those of other materials reported such as α-CD and V-type starch. The release characteristics of ethylene inclusion complexes (ICs) were determined under different temperatures and relative humidity conditions. The ethylene gas could be stably encapsulated in α-CD-MOF-ethylene ICs at 25 °C for up to 30 days. The crystal structure of α-CD-MOFs was determined to explain their high capacity and stability for ethylene storage. Molecular simulation was used to model the location of ethylene molecules in α-CD-MOFs. Alpha-CD-MOF-Na and α-CD-MOF-K showed "8"-shaped and spindle-shaped cavity, respectively, which effectively adsorbed and stored the ethylene gas. Accelerated ripening experiments showed that 5 mg of α-CD-MOF ICs could ripen bananas within 4 days, with an effect similar to that of free ethylene gas. We suggest that α-CD-MOF materials are an excellent material for ethylene storage with potential application in industrial and agricultural areas.

Changes in Nanoscale Chain Assembly in Sweet Potato Starch Lamellae by Downregulation of Biosynthesis Enzymes

Granule-bound starch synthase I (GBSSI) and starch-branching enzymes I and II (SBEI and SBEII) are crucial enzymes that biosynthesize starches with varied apparent amylose contents and amylopectin branching structure. With a sweet potato ( Ipomoea batatas [L.] Lam. cv. Xushu22), this work shows that downregulating GBSSI (for waxy starch) or SBE (for high-amylose starch) activity allowed the formation of new semicrystalline lamellae (named Type II) in sweet potato starch in addition to the widely reported Type I lamellae. Small-angle X-ray scattering (SAXS) results show that, compared with Type I lamellae, Type II lamellae displayed increased average thickness and thickness-distribution width, with thickened amorphous and crystalline components. The size-exclusion-chromatography (SEC) data revealed mainly two enzyme sets, (i) and (ii), synthesizing amylopectin chains. Reducing the GBSSI or SBE activity increased the amounts of amylopectin long chains (degree of polymerization (DP) ≥ 33). Combined SAXS and SEC analyses indicate that parts of these long chains from enzyme set (i) could be confined to Type II lamellae, followed by DP ≤ 32 short chains in Type I lamellae and the rest of the long chains from enzyme sets (i) and (ii) spanning more than a single lamella.