Catalytic flash pyrolysis for recovery of gasoline-range hydrocarbons from electric cable residue using a low-cost natural catalyst: An analytical Py-GC/MS study.

This investigation's novelty and objective reside in exploring catalytic flash pyrolysis of cross-linked polyethylene (XLPE) plastic residue in the presence of kaolin, with the perspective of achieving sustainable production of gasoline-range hydrocarbons. Through proximate analysis, thermogravimetric analysis, and heating value determination, this study also assessed the energy-related characteristics of cross-linked polyethylene plastic residue, revealing its potential as an energy source (44.58 MJ kg-1) and suitable raw material for pyrolysis due to its low ash content and high volatile matter content. To understand the performance as a low-cost catalyst in the flash pyrolysis of cross-linked polyethylene plastic residue, natural kaolin was subjected to characterization through thermogravimetric analysis, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). Cross-linked polyethylene plastic residue was subjected to thermal and catalytic pyrolysis in an analytical microreactor coupled to gas chromatography-mass spectrometry (Py-GC/MS system), operating at 500 °C, to characterize the distribution and composition of volatile reaction products. The application of kaolin as a catalyst resulted in a decline of the relative concentration of hydrocarbons in the diesel range (C8-C24) from approximately 87 % to 28 %, and a reduction in lubricating oils (C14-C50) from about 70 % to 13 %, while concomitantly increasing the relative concentration of lighter hydrocarbons in the gasoline range (C8-C12) from around 28 % to 87 %. Therefore, catalytic flash pyrolysis offers the potential for converting this plastic waste into a new and abundant chemical source of gasoline-range hydrocarbons. This process can be deemed viable and sustainable for managing and valorizing cross-linked polyethylene plastic residue.

Artificial neural network-assisted thermogravimetric analysis of thermal degradation in combustion reactions: A study across diverse organic samples.

During gasification the kinetic and thermodynamic parameter depend on both the feedstock and the process conditions. As a result, one needs to enhance the understanding of how to model numerically these parameters using thermogravimetric analyzer. Consequently, there exists a pressing need to computationally devise gasification model that can efficiently account to thermodynamic and kinetic parameter from thermogravimetric data. In this study, we numerically model gasification process kinetic and thermodynamic parameters, which vary with feedstock and operational conditions. Our novel approach involves creating an ANN model in MATLAB using a carefully optimized 8-20-20-10-1 architecture. Based on thermogravimetric analyzer (TGA) data, this model uniquely predicts critical kinetic (activation energy, pre-exponential factor) and thermodynamic parameters (entropy, enthalpy, Gibbs free energy, ignition index, boiling temperature). Our ANN model, trained on over 80 diverse samples with the Levenberg-Marquardt algorithm, excels at prediction, with an MSE of 6.185e-6 and an R2 value exceeding 0.9996, ensuring highly accurate estimates. Based on time, temperature, heating rate, and elemental composition, it accurately predicts thermal degradation. The model can predict TGA curves for many materials, demonstrating its versatility. For instance, it accurately estimates the activation energy for pure glycerol at 73.84 kJ/mol, crude glycerol at 67.55 kJ/mol, 12.12 kJ/mol for coal, and 111.3 kJ/mol for wood. These results, particularly for Kissinger-validated glycerol, demonstrate the model's versatility and efficacy in various gasification scenarios, making it a valuable tool for thermochemical conversion studies.

Encapsulation of benznidazole in nanostructured lipid carriers and increased trypanocidal activity in a resistant Trypanosoma cruzi strain

Abstract Chagas disease is a neglected parasitic disease caused by Trypanosoma cruzi, whose treatment has remained unsatisfactory for over 50 years, given that it is limited to two drugs. Benznidazole (BZN) is an efficient antichagasic drug used as the first choice, although its poor water-solubility, irregular oral absorption, low efficacy in the chronic phase, and various associated adverse effects are limiting factors for treatment. Incorporating drugs with such characteristics into nanostructured lipid carriers (NLC) is a promising alternative to overcome these limiting obstacles, enhancing drug efficacy and bioavailability while reducing toxicity. Therefore, this study proposed NLC-BZN formulations in different compositions prepared by hot-melt homogenization followed by ultrasound, and the optimized formulation was characterized by FTIR, DRX, DSC, and thermogravimetry. Biological activities included in vitro membrane toxicity (red blood cells), fibroblast cell cytotoxicity, and trypanocidal activity against epimastigotes of the Colombian strain of T. cruzi. The optimized NLC-BZN had a small size (110 nm), negative zeta potential (-18.0 mV), and high encapsulation (1.64% of drug loading), as shown by infrared spectroscopy, X-ray diffraction, and thermal analysis. The NLC-BZN also promoted lower in vitro membrane toxicity (<3% hemolysis), and 50% cytotoxic concentration (CC50) for NLC-BZN in L929 fibroblast cells (110.7 µg/mL) was twice the value as the free BZN (51.3 µg/mL). Our findings showed that the NLC-BZN had higher trypanocidal activity than free BZN against the epimastigotes of the resistant Colombian strain, and this novel NLC-BZN formulation proved to be a promising tool in treating Chagas disease and considered suitable for oral and parenteral administration

Fabrication and characterization of 3-dimensional electrospun poly(vinyl alcohol)/keratin/chitosan nanofibrous scaffold.

Layer-by-layer three-dimensional nanofibrous scaffolds (3DENS) were produced using the electrospinning technique. Interest in using biopolymers and application of electrospinning fabrication techniques to construct nanofibers for biomedical application has led to the development of scaffolds composed of PVA, keratin, and chitosan. To date, PVA/keratin blended nanofibers and PVA/chitosan blended nanofibers have been fabricated and studied for biomedical applications. Electrospun scaffolds comprised of keratin and chitosan have not yet been reported in published literature, thus a novel nanofibrous PVA/keratin/chitosan scaffold was fabricated by electrospinning. The resulting 3DENS were characterized using fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), differential scanning colorimetry (DSC), and thermogravimetric analysis (TGA). Physiochemical properties of the polymer solutions such as viscosity (rheology) and conductivity were also investigated. The 3DENS possess a relatively uniform fibrous structure, suitable porosity, swelling properties, and degradation which are affected by the mass ratio of keratin, and chitosan to PVA. These results demonstrate that PVA/keratin/chitosan 3DENS have the potential for biomedical applications.

Improved water dispersion and bioavailability of coenzyme Q10 by bacterial cellulose nanofibers.

The purpose of this study was to investigate the potential of bacterial cellulose nanofiber suspension (BCNs) as stabilizer in anti-solvent precipitation and its effect on improving bioavailability of coenzyme Q10. Bacterial cellulose (BC) was hydrolyzed by sulfuric acid followed by the oxidation with hydrogen peroxide to prepare BCNs. The suspension of BCNs-loaded CoQ10 (CoQ10-BCNs) were prepared by antisolvent precipitation. The zeta potential of CoQ10-BCNs was about -36.01 mV. The properties of CoQ10, BCNs and CoQ10-BCNs were studied by scanning electron microscopy, transmission electron microscope, Fourier-transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermo gravimetric analysis. The crystallinity of CoQ10 decreased in CoQ10-BCNs compared with the raw CoQ10, and CoQ10-BCNs have good physicochemical stability. In oral bioavailability studies, the area under curve (AUC) of CoQ10-BCNs was about 3.62 times higher than the raw CoQ10 in rats.

Physicochemical characterization and cosmetic applications of Passiflora nitida Kunth leaf extract

Abstract Passiflora nitida Kunth, an Amazonian Passiflora species, is little studied, although the specie's high biological potential. Herein the plant's pharmacognostic characterization, extract production, antioxidant potential evaluation, and application of this extract in cosmetic products is reported. The physical chemical parameters analyzed were particle size by sieve analysis, loss through drying, extractive yield, total ash content, laser granulometry, specific surface area and pore diameter (SBET), differential scanning calorimetry, thermogravimetry (TG), and wave dispersive X-Ray fluorescence (WDXRF). Total phenol/flavonoid content, LC-MS/MS analysis, DPPH and ABTS antioxidant radical assays, cytotoxicity, melanin, and tyrosinase inhibition in melanocytes test provided evidence to determine the content of the major constituent. P. nitida dry extract provided a fine powder with mesopores determined by SBET, with the TG curve showing five stages of mass loss. The antioxidant potential ranged between 23.5-31.5 mg∙mL-1 and tyrosinase inhibition between 400-654 µg∙mL-1. The species presented an antimelanogenic effect and an inhibitory activity of cellular tyrosinase (26.6%) at 25 µg/mL. The LC-MS/MS analysis of the spray-dried extract displayed the main and minor phenolic compounds constituting this sample. The results indicate that P. nitida extract has promising features for the development of cosmetic formulations

Caracterización colorimétrica del proceso termogravimétrico de la deshidroxilación de caolín hidrotermal y de toba / Colorimetric characterization of thermogravimetric process for dehydroxilation of hydrothermal and tuff kaolins

El metacaolín es el producto obtenido de la calcinación del caolín. La alta actividad puzolánica del metacaolín permite su utilización como un material sustituto del cemento en el concreto. Esta y otras propiedades fisicoquímicas se ven afectadas por las condiciones de procesamiento del caolín. Por lo tanto, este estudio tuvo como objetivo caracterizar los cambios del color y densidad de dos tipos de caolín (toba triturada e hidrotermal) por medio de un análisis termogravimétrico del proceso de calcinación. Para la evaluación de la densidad se empleó la norma ASTM C188, mientras que la valoración de los cambios de color utilizó un espectrofotómetro C I E - L* a * b* en conjunto con la norma UNE 80117. Asimismo, la pérdida de peso y la densidad se correlacionaron con las coordenadas de color mediante una regresión polinomial. Los resultados demostraron que la deshidroxi-lación de los caolines ocurrió entre 400 ºC y 650 ºC, caracterizándose por un máximo en el delta E* de 12.9 y 4.3 para el caolín hidrotermal y de toba, respectivamente. Además, el caolín de toba triturada presentó la máxima luminosidad (L* = 92.84) de todos los tratamientos a los 21 ºC. Este valor disminuyó 11.75% al incrementar la temperatura hasta 450 ºC. A partir de esta temperatura,L* incrementó linealmente hasta alcanzar un valor final de 87.3 a 900 ºC. La regresión polinomial obtenida explica en un 93% y 92% la variación del peso en función de los parámetros C I E - L* a * b* para el caolín de toba triturada e hidrotermal, respectivamente.

Metakaolin is a product of kaolin's calcination. The high pozzolanic activity of metakaolin allows its usage as supplementary cementitious material in concrete. This property and other physicochemical properties are affected by metakaolin's manufacturing conditions. Therefore, this study aims to characterize the changes in color and density of two types of kaolin (tuff and hydrothermal) through a thermogravimetric analysis of the calcina-tion process. Evaluation of density used ASTM C188, while the assessment of color changes used a CIE-L*a*b* spectrophotometer in conjunction with normative UNE 80117. In addition, weight loss and density were correlated with the color coordinates using polynomial regression. The results showed that kaolin dehydroxylation occurred at 450ºC and 650ºC, characterized by a maximum in delta E * of 12.9 and 4.3 for hydrothermal and tuff kaolin, respectively. In addition, the tuff kaolin presented the maximum luminosity (L * = 92.84) of all the treatments at 21ºC. This value decreased 11.75% during the temperature increment up to 450ºC. From this temperature, L * increased linearly until reaching a final value of 87.3 at 900ºC. The polynomial regression explained 93% and 92% of the weight variation as a function of the CIE-L*a*b* parameters for tuff and hydrothermal kaolin, respectively.

Thermogravimetric analysis of the pyrolysis and combustion kinetics of surface dead combustibles in the Daxing'an Mountains.

In boreal regions, the frequency of forest fires is increasing. In this study, thermogravimetric analysis was used to analyze the pyrolysis kinetics of dead surface combustibles in different forest types within the Daxing'an Mountains, China. The results show that the combustible material load of forest types, the Larix forest (LG) is relatively high. Base on the E of kinetic parameters, the LG, and Quercus forest (QM) forest types had relatively high combustibility values and comprehensive combustibility values for 1-, 10-, and 100-h time lags. According to the obtained P values, the pyrolysis of dead surface fuels with 1-, 10-, and 100-h time lags is relatively difficult in the Larix / Betula mixed forest (L-B) and QM forest types. Therefore, mixed forests of the LG, L-B, and QM tree species can be established as fire-resistant forests to establish a fire barrier, reduce the combustibility of forest stands, and reduce the possibility of forest fires.

Development of a guar gum film with lysine clonixinate for periodontal treatments.

Periodontal pain is a public health problem derived from different conditions, including periodontal diseases, prosthetic complications, and even extractions performed by dentist. There are various treatments to control acute dental pain, being the administration of analgesics, such as Lysine Clonixinate (LC), a common practice. Unfortunately, higher and repeated dosages are usually required. The purpose of this work was to develop a prolonged release pharmaceutical form as an alternative treatment for dental pain. Hence, we conceived a film based on guar gum and loaded different concentrations of LC. We evaluated the film's appearance, brittleness, strength, and flexibility, and then chose one formulation for adequate characteristics. Subsequently, we assessed the morphology, thermal behavior, and swelling properties of the films (LC-free and -loaded). Finally, we performed the release studies of LC from the films in vitro using a simulated saliva medium and employed several mathematical models to evaluate the release kinetics. Guar gum is a natural polymer obtained from the endosperm of Cyamopsis tetragonolobus that presents properties such as biosafety, biocompatibility, and biodegradability. Thus, it represents a potential excipient for use in pharmaceutical formulations. Moreover, our results revealed that the LC-loaded film presented a high adherence, suitable swelling behavior, high LC content, and a prolonged drug release. Therefore, the LC-loaded film may be considered a potential option to be applied as an alternative to treat dental pain.

Development of a xanthan gum film for the possible treatment of vaginal infections.

Bacterial vaginosis is a vaginal infection that affects 60% of women of reproductive age worldwide. It is mainly caused by the bacterium Gardnerella vaginalis and is a factor that increases the probability of getting sexually transmitted diseases. We aimed to develop a new pharmaceutical form for the treatment of vaginal infections. We employed the solving-casting method to fabricate a polymeric film with Xanthan gum, a natural polymer produced by the bacterium Xanthomonas campestris, and metronidazole, one of the most commonly used drugs for vaginal infections. In order to characterize the film, we measured pH, dose uniformity, dissolution profile, and the percentage of swelling. Moreover, we performed a thermogravimetric analysis and scanning electron microscopy. The results demonstrated a pH suitable for vaginal application and uniform distribution of the drug in the film. Also, the formulation exhibited a high percentage of swelling and a slow release of the drug in a simulated vaginal fluid medium. All these attributes indicated that the manufactured film has ideal characteristics to be used and administered vaginally. It could be an excellent alternative to treat bacterial vaginosis and also improve user adherence.

Physicochemical and biological characterization of a xanthan gum-polyvinylpyrrolidone hydrogel obtained by gamma irradiation.

Xanthan gum (XG) and polyvinylpyrrolidone (PVP) are two polymers with low toxicity, high biocompatibility, biodegradability, and high hydrophilicity, making them promising candidates for multiple medical aspects. The present work aimed to synthesize a hydrogel from a mixture of XG and PVP and crosslinked by gamma irradiation. We assessed the hydrogel through a series of physicochemical (FT-IR, TGA, SEM, and percentage of swelling) and biological (stability of the hydrogel in cell culture medium) methods that allowed to determine its applicability. The structural evaluation by infrared spectrum demonstrated that a crosslinked hydrogel was obtained from the combination of polymers. The calorimetric test and swelling percentage confirmed the formation of the bonds responsible for the crosslinked structure. The calorimetric test evidenced that the hydrogel was resistant to decomposition in contrast to non- irradiated material. The determination of the swelling degree showed constant behavior over time, indicating a structure resistant to hydrolysis. This phenomenon also occurred during the test of stability in a cell culture medium. Additionally, microscopic analysis of the sample revealed an amorphous matrix with the presence of porosity. Thus, the findings reveal the synthesis of a novel material that has desirable attributes for its potential application in pharmaceutical and biomedical areas.

Radiation-induced graft polymerization of elastin onto polyvinylpyrrolidone as a possible wound dressing.

The purpose of our study was to obtain new wound dressings in the form of hydrogels that promote wound healing taking advantage of the broad activities of elastin (ELT) in physiological processes. The hydrogel of ELT and polyvinylpyrrolidone (PVP; ELT-PVP) was obtained by cross-linking induced by gamma irradiation at a dose of 25 kGy. The physicochemical changes attributed to cross-linking were analyzed through scanning electron microscopy (SEM), infrared spectroscopy analysis with Fourier transform (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Furthermore, we performed a rheological study to determine the possible changes in the fluidic macroscopic properties produced by the cross-linking method. Finally, we accomplished viability and proliferation analyses of human dermal fibroblasts in the presence of the hydrogel to evaluate its biological characteristics. The hydrogel exhibited a porous morphology, showing interconnected porous with an average pore size of 16 ± 8.42 µm. The analysis of FTIR, DSC, and TGA revealed changes in the chemical structure of the ELT-PVP hydrogel after the irradiation process. Also, the hydrogel exhibited a rheological behavior of a pseudoplastic and thixotropic fluid. The hydrogel was biocompatible, demonstrating high cell viability, whereas ELT presented low biocompatibility at high concentrations. In summary, the hydrogel obtained by gamma irradiation revealed the appropriate morphology to be applied as a wound dressing. Interestingly, the hydrogel exhibited a higher percentage of cell viability compared with ELT, suggesting that the cross-linking of ELT with PVP is a suitable strategy for biological applications of ELT without generating cellular damage.

Chitosan-strontium chondroitin sulfate scaffolds for reconstruction of bone defects in aged rats.

Bone defects caused by trauma have become increasingly common in aged populations. Clinically, because of the relatively decreased bone healing capacity compared with the youth adults, bone defect repair in the elderly remains challenging. The development of effective biomaterials targeted at bone defects in the elderly is a key component of bone-tissue engineering strategies. However, little attention has been paid to bone regeneration in the elderly. Here, we developed a new scaffold chitosan-Strontium chondroitin sulfate (CH-SrCS) and evaluated its effect on improving bone regeneration. We find that the CH-SrCS scaffold displayed positive effects on downregulation of inflammation and osteoclastogenesis related mRNA expressions while demonstrating a significant increase in the expression level of BMP2. Finally, we show that the bone defects healing effects as assessed using an aged rats' bone defects model. Ultimately, this work also provides insights into the design of effective biomaterials targeted at bone defects in the elderly.

Effects of isolation conditions on structural and functional properties of the seed gum from Chinese quince (Chaenomeles sinensis).

Chinese quince seed gum (CQSG) extracted under water-, alkali- and acid- conditions at 25, 50, and 80 °C, were evaluated in terms of yield, monosaccharide composition, molecular distribution, thermal gravimetry, emulsifying stability, rheological properties, and free radical scavenging ability. The results showed that the yield of CQSG increased to 3.9% after water extraction at 80 °C. Alkali and acid treatments promoted the conversion of neutral sugars to the uronic acid branch. Regardless of the extraction temperature, the xylose chain was the main component (35%-40%); however, a reduction was observed as the extraction temperature increased to 80 °C. All CQSG solutions extracted under these isolation conditions exhibited non-Newtonian rheological behavior. Compared to water-extracted samples, the alkali-extracted samples showed the worst thermal stability, while the acid-treated samples showed the worst emulsifying stability. This study provides theoretical support for the potential application of CQSG polysaccharides in the food and pharmaceutical industries.

Flame Retardant Functionalization of Microcrystalline Cellulose by Phosphorylation Reaction with Phytic Acid.

The functionalization of microcrystalline cellulose (MCC) is an important strategy for broadening its application fields. In the present work, MCC was functionalized by phosphorylation reaction with phytic acid (PA) for enhanced flame retardancy. The conditions of phosphorylation reaction including PA concentration, MCC/PA weight ratio and temperature were discussed, and the thermal degradation, heat release and char-forming properties of the resulting PA modified MCC were studied by thermogravimetric analysis and pyrolysis combustion flow calorimetry. The PA modified MCC, which was prepared at 90 °C, 50%PA and 1:3 weight ratio of MCC to PA, exhibited early thermal dehydration with rapid char formation as well as low heat release capability. This work suggests a novel strategy for the phosphorylation of cellulose using PA and reveals that the PA phosphorylated MCC can act as a promising flame retardant material.

Effect of cellulose and starch fatty acid esters addition on microstructure and physical properties of arabinoxylan films.

Arabinoxylan (AX) and cellulose were extracted from wheat straw, whereas starch was extracted from potato peel. Thereafter, cellulose and starch were esterified with lauric, myristic, palmitic and stearic acids to prepare corresponding cellulose (CFAs) and starch fatty acid esters (SFAs) with DS 2.1-2.8. XRD study revealed remarkable loss of crystallinity in cellulose and starch due to fatty acid esterification. The addition of palmitate and stearate esters of cellulose and starch to AX formed laminar film microstructures which limited water vapor permeability whereas films prepared by blending AX with laurate and myristate esters of starch and cellulose were less effective as water vapor barrier due to their non-layer microstructures. The laminar structures also resulted significant reduction in mechanical strength of the composite films. Furthermore, all AX-CFAs and AX-SFAs films were thermally more stable than native composite films. These films might be used to produce industrially useful coating material for food products.

Gradient chondroitin sulfate/poly (γ-glutamic acid) hydrogels inducing differentiation of stem cells for cartilage tissue engineering.

Based on the gradient distribution of structure and composition in biological cartilage tissue, we designed a gradient hydrogel scaffold by the moving photomask, using chondroitin sulfate and poly (γ-glutamic acid) as crude materials. The hydrogel scaffold had a gradient distribution of cross-linking density, which can be verified from the results of SEM and swelling behavior. Besides, the hydrogel exhibited great viscoelastic, toughness (70% strain), and strength properties (600 kPa). Additionally, the gradient hydrogel's superior cell compatibility was proved through the MTT, live/dead staining assays, and 3D cell culture experiments. Remarkably, the results of in vitro stem cell differentiation experiments showed that the duration of light directly affected the differentiation extent of stem cells, demonstrating that the gradient hydrogel scaffold can better simulate the function of natural cartilage than the homogeneous one. Due to these outstanding characteristics, this gradient hydrogel is a potential scaffold for cartilage tissue engineering.

In-situ synthesis of polypyrrole/silver for fabricating alginate fabrics with high conductivity, UV resistance and hydrophobicity.

In this research, the polypyrrole/silver (PPy/Ag) composite was first in-situ prepared on alginate fabrics by chemical oxidative polymerization of pyrrole (Py) monomer using silver nitrate as oxidant and sodium dodecyl sulfate (SDS) as the dopant. The effects of mole ratio of Py to silver nitrate, reaction time and dopant concentration on the preparation of PPy/Ag composite were optimized. It was found the optimal molar ratio of Py to silver nitrate was 1:1.5 with 0.02 M SDS under the reaction time of 10 h. Then, the microstructure and properties of resultant PPy/Ag composite were analyzed by scanning electron microscope (SEM), Fourier infrared spectrometer (FT-IR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and the thermogravimetry analysis (TGA), respectively. Finally, the influences of PPy/Ag coating on the performance of alginate fabrics including electrical conductivity, hydrophilicity, antistatic property and anti-ultraviolet capability were determined. It was found that the electrical conductivity of alginate fabric could be intensively increased after PPy/Ag coating. Meantime, the anti-ultraviolet capability and hydrophobicity could be largely improved by PPy/Ag coating especially under high Py dosage. This paper introduced a simple method for preparing PPy/Ag composite direct on alginate fabric to make it a good functional substrate which could be applied in many fields.

Characterization the structural property and degradation behavior of corn starch in KOH/thiourea aqueous solution.

Finding an efficient and eco-friendly solution for starch dissolution has attracted considerable attentions in recent years. This study investigated the structural characteristics, and degradation behavior of corn starch in KOH/thiourea aqueous solution by the comparison with DMSO/LiBr and 1-allyl-3-methylimidazolium chloride (AMIMCl). Results showed that KOH/thiourea solution was an effective solvent for corn starch dissolution (30 min with 97.01% solubility). X-ray diffraction (XRD) and 13C CP-MAS NMR spectroscopy revealed that native crystallinity of the corn starch was altered by all tested solvents, especially DMSO/LiBr and AMIMCl. Conversely, this new solvent did not change the primary molecular structure, chain-length distribution, or thermal stability of starch, compared with the native starch. Furthermore, KOH/thiourea solution was more suitable for measuring the molecular weight of corn starch, with a weight-average molecular weight (Mw) of 7.18 × 107 g/mol. Therefore, KOH/thiourea solution is a promising novel solvent for starch dissolution and structural exploration.

Manipulation of the internal structure of starch by propionyl treatment and its diverse influence on digestion and in vitro fermentation characteristics.

High amylose maize starch (HAMS) and waxy maize starch (WMS) were modified by propionylation and their corresponding physicochemical characteristics, digestion and fermentation properties were studied. The results indicated that two new peaks related to methylene (2.20 ppm) and methyl (0.97 ppm) in the NMR spectrum were formed, indicating the occurrence of propionylation, and this was further confirmed by the formation of a characteristic absorption at 1747 cm-1 in the FTIR spectrum. The propionylation led the modified starch having a lower electron density contrast between the crystalline and amorphous flakes, resulting in the formation of a more compact structure following the increased degrees of substitution (DS). The propionylated starch also had a higher thermal stability and hydrophobicity. These structural changes increased the content of resistant starch (RS) and reduced the predicted glycemic index. More importantly, the gut microbiota fermentation properties indicated that the propionylation of the starch can not only increase the yield of propionate, but also increase the concentration of total short-chain fatty acids (SCFAs). This study highlights a new approach to significantly enhance the RS content in starch, together with an increased SCFA generation capacity.