Lower Enthalpy Change Research Articles

Effect of the addition of pregelatinized rice starch paste on the retrogradation of rice starch gel

The effect of the addition of pregelatinized rice starch paste (PRSP) on the retrogradation of rice starch (RS) gels was investigated using rheometer, X-ray diffraction (XRD), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM). A decrease in the storage modulus of RS gels after short-term storage was found after adding PRSP. The XRD results revealed that the retrogradation degree of RS gels with added PRSP was lower than in the absence of PRSP, suggesting that the addition of PRSP could restrain the long-term retrogradation of rice starch. Moreover, the lower enthalpy changes of RS gels with added PRSP after retrogradation suggested that the progress of amylopectin crystallization was delayed due to PRSP incorporation. SAXS analysis showed that adding PRSP inhibited swelling of RS and decreased the size of aggregation during storage, which suppressed starch retrogradation. In addition, CLSM images indicated that PRSP could form continuous network in which the RS granules embedded, and that gels with PRSP exhibited greater phase separation after 15 d storage. These results suggested that the addition of PRSP inhibited the retrogradation of RS gels. The inhibitory effect is mainly due to PRSP altering the gel formation type and prohibiting the excessive swelling of rice starch granules during gelatinization. This study could provide new insights for the production of rice products and for prolonging their shelf life during storage.

Effects of ethanol washing on off-flavours removal and protein functionalities of pea protein concentrate

This study investigates the effects of treating pea protein concentrate (PPC) with hydroalcoholic solutions on off-flavour removal. Increasing ethanol concentration in the hydroalcoholic solutions from 15 to 75% (v/v) enhanced the removal of volatile compounds contributing to off-flavours such as 1-hexanol, 1-octanol, 3-hexen-1-ol, 1-nonanol and trans-2-hexenal. Differential scanning calorimetry and protein solubility studies showed that higher ethanol concentration induced more protein denaturation as evidenced by the lower enthalpy change and protein solubility of the treated PPC samples. Insoluble protein aggregates formed were hypothesized to be linked by hydrogen bonding. Hydroalcoholic washing of PPC also increased its water holding capacity but reduced oil holding capacity. Ethanol concentrations deployed in the hydroalcoholic solutions influenced gelling behaviour, where increase in PPC gel strength was observed in PPC treated with lower concentrations of ethanol, i.e., 15 and 25% (v/v). However, higher ethanol concentrations, i.e., 50 and 75% (v/v) induced higher extent of insoluble aggregates which weakened the gel network and reduced gel strength. In conclusion, PPC treated with high ethanol concentrations reduced majority of volatile compounds contributing to off-flavour, but significant protein structural changes which could influence product development performance were also observed.

Acidic protic ionic liquid‐based deep eutectic solvents capturing SO2 with low enthalpy changes

AbstractWith the aim of lowering energy consumption for gas regeneration, rational design of absorbents with low absorption enthalpy changes while retaining good gas solubility is of both scientific and practical significance. Herein, we demonstrated that acidic protic ionic liquid (APIL)‐based deep eutectic solvents (DESs), which comprise N‐ethylimidazole hydrochloride ([EimH]Cl) and ethylene glycol (EG), were able to reversibly absorb SO2 with high solubility (11.60 mol kg−1) and SO2/CO2 selectivity (655) at 293.2 K and 101.3 kPa. Meanwhile, [EimH]Cl/EG DESs exhibit very low enthalpy changes (ΔrHm) ranging from −27.1 to −25.6 kJ mol−1, and thus ease of desorption at very mild temperature conditions (303.2 K) with desorption ratios up to 99.6%. Recycling experiments showed that no obvious loss in capacity was found after six absorption–desorption cycles, suggesting good regeneration performance of [EimH]Cl/EG DESs. Moreover, spectroscopic analysis revealed the charge‐transfer interaction between [EimH]Cl/EG and SO2.

Variations in the Multilevel Structure, Gelatinization and Digestibility of Litchi Seed Starches from Different Varieties.

Litchi seed starches from six varieties, as compared with maize starch, were studied for their multilevel structures, thermal and digestion properties to understand the distinct feather of each variety and provide guidance for their utilization in multi-industries. The results showed different varieties of litchi seed starch shared similar appearances with granules in oval shape and with a smooth surface. Starch granules of all the varieties exhibited typical bimodal size distributions consisting of small (<40 μm) and large granules (40–110 μm), although their relative proportions were largely dependent on variety. Huaizhi had the largest D50 value, whilst Guiwei showed the lowest. All the litchi seed starches had A-type crystalline with relative crystallinity varying from 20.67% (Huaizhi) to 26.76% (Guiwei). Similarly, the semi-crystalline structure varied apparently with variety. As to the chain-length distribution, only slight differences were observed among varieties, except Huaizhi displayed apparently higher amylose content (34.3%) and Guiwei showed the lowest (23.6%). Significant differences were also present in the gelatinization properties. Huaizhi seed starch showed significantly higher gelatinization temperatures and lower enthalpy change than the others. The digestibility of cooked litchi seed starches was only slightly different among varieties, suggesting variety is not the most critical factor regulating the digestibility of cooked litchi seed starch.

Oxidative desulfurization of a model fuel using MoO3 nanoparticles supported on carbon nanotubes catalyst: Examine most significance variables, optimization, kinetics and thermodynamics study

Molybdenum oxide nanoparticles MONP were dispersed on multiwall nanotubes MWNTs as an attempt to synthesize MONP/MWNTs catalyst, the synthesis method done by wet impregnation. The prepared catalyst was characterized by FTIR (Fourier –Transform Infrared Spectroscopy) and, XRD (X-ray diffraction), whilst the catalyst activity is done with catalytic oxidative desulfurization ODS reaction for oxidation dibenzothiophene DBT dissolved in heptane (model fuel) with hydrogen peroxide H2O2, in which catalyst activity investigation achieved via studying impact six from most affected variables on ODS reaction. The chosen variables are reaction temperature, contact time, sulfur initial sulfur concentration, stirring speed, oxidant/sulfur ratio and catalyst dosage, and then the studied variables were screened by application of Plackett-Burman design PBD to identify the more significant on response (DBT pollutant removal). DBT pollutant removal is referred to as sulfur removal efficiency. Analysis of variance ANOVA shows that the reaction temperature, oxidant/sulfur ratio, stirring speed, and sulfur initial concentration are the most significant from the chosen variables due to their F-values 37.60, 25.45, 11.62 and 6.71 respectively. Box –Behnken experimental design was used to complete the study the effect of the most significant more deeply on ODS reaction (sulfur removal efficiency),in which this part exhibited that sulfur removal efficiency at range between 51 and 93%, whilst the optimum sulfur removal efficiency was 96% at 70 °C,4.36, 957 rpm and 50 ppm for reaction temperature, oxidant/sulfur ration, stirring speed and initial sulfur concentration respectively. The study involves estimation of kinetics and thermodynamics parameters for ODS reaction; kinetics studying exhibited that ODS reaction followed pseudo-first-order reaction with activation energy (12.996 kJ/mol), while the thermodynamics study shows the low negative entropy change (-0.221 kJ /mol.K), positive enthalpy and free energy changes which confirm a high hydrate transition complex was formed.

Structural, Morphological and Thermal Properties of Nano Filler Produced from Date Palm-Based Micro Fibers (Phoenix dactylifera L.)

In this century, the development of nano-sized filler from biomass material has become the main focus of industries in achieving their final green composite product for a wide range of applications. From a commercial and environmental point of view, fragmentation and downsizing of waste lignocellulosic fibers without chemical treatments into small size particles is a viable option. In this study, an attempt was made to produce nano-sized lignocellulosic fillers from date palm micro fibers via mechanical ball milling process at intense 99 cycles run (equivalent to 25 h). The resultant nanofillers as well as the microfibers were characterized in details by various analytical techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), particle size analysis (PSA), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to assess their structure—property relationship. From microscopy examination, the nanofillers showed a heterogeneous mix of irregular shaped particles, and while having a size ranging of 30–110 nm in width and 1–10 mm length dimensions. Also, the crystallography analysis revealed the crystallinity had mildly declined from microfibers (71.8%) to nanofiller (68.9%) due to amorphization effect. As for thermal analysis, the nanofillers exhibited high heat resistance at 260.8 °C decomposition temperature. Furthermore, the nanofillers also had stable thermo-changing behavior by presenting low heat enthalpy change (40.15 J/g) in its endothermic reaction for breaking organic bonds. The thermal results suggest its suitability for composite fabrication process at high temperature. Thus, the produced nanofillers can be used as a low cost reinforcing agent in the future for versatile polymer-based composite systems.

Synthesis of Retinol-Loaded Lipid Nanocarrier via Vacuum Emulsification to Improve Topical Skin Delivery.

Retinol has been widely used as an anti-wrinkle active ingredient in cosmetic fields. However, the oxidation of retinol by air was one of the critical problems for application in the skincare field. In this study, Retinol-loaded lipid nanocarriers were prepared via the vacuum emulsification method to increase the stability of retinol vulnerable to air and optimized encapsulation conditions and to increase the penetration efficiency into skin. Optimizing the components of lipid nanocarriers, gradients of carbon chain C8-22 using various lipid species which made the amorphous structure and enough spaces to load retinol inside the capsules were estimated from the lower enthalpy change and peak shift in DSC analysis. The vacuum-assisted lipid nanocarriers (VLN) could help suppress oxidation, which could have advantages to increase the thermal stability of retinol. The retinol-loaded VLN (VLN-ROL) had narrow size distribution under 0.3 PDI value, under 200 nm scaled particle size, and fully negative surface charge of about -50 mV for the electrostatic repulsion to avoid aggregation phenomenon among the lipid nanoparticles. It maintained 90% or more retinol concentration after 4 weeks of storage at 25, 40 and 50 °C and kept stable. The VLN-ROL-containing cream showed improved penetration efficiency applied to porcine skins compared to the commercial retinol 10S from BASF. The total amount of retinol into the skin of VLN-ROL (0.1% of retinol) was enhanced by about 2.2-fold (2.86 ± 0.23 μg) higher than that in 0.1% of bare retinol (about 1.29 ± 0.09 μg). In addition, applied on a 3D Human skin model, the epidermal thickness and the relative percentage of dermal collagen area effectively increased compared to the control and retinol, respectively. Additionally, the level of secreted IL-1α was lower and epidermal damage was weaker than commercial product A. This retinol-loaded lipid nanocarrier could be a potentially superior material for cosmetics and biomedical research.

Application of KOH modified seaweed hydrochar as a biosorbent of Vanadium from aqueous solution: Characterisations, mechanisms and regeneration capacity

Abstract Vanadium exists as a mobile and toxic trace metal in many alkaline residue leachates. Its removal and recovery not only reduces a global environmental risk but is also critical to the emergence of innovative technologies and the circular economy. In parallel, the use of treated biomass feedstock is receiving increased attention as a low cost adsorbent for toxic metals in wastewater. This study investigated the adsorption of Vanadium (V) from aqueous solution by KOH modified seaweed (Ascophyllum nodosum) hydrochar (HCKOH). The results showed that HCKOH is an effective V(V) adsorbent, achieving maximum uptake of 12.3 mg g−1 at solution pH 4, 60 min contact time and temperature 293 K. The kinetics followed a pseudo second order model with film diffusion controlling the overall adsorption rate. The type I adsorption isotherm was well fitted to a Langmuir model (qm = 12.3 mg g-1, R2 = 0.970, RMSE = 0.66) and a thermodynamic study indicated that the V(V) adsorption was both exothermic and spontaneous. The low enthalpy change (-10.97 kJ mol−1) indicated a weak binding of V(V) to HCKOH pointing to the possibility of V recovery. The impact of co-existing cations on V(V) uptake was negligible for Na(I) and Ga (III) but was reduced slightly for Al(III). Desorption and re-adsorption results (3 cycles) indicated that HCKOH has reusable potential to remove and recover V(V) from waste leachates.

Physicochemical and structural properties of starches isolated from quinoa varieties

Starches isolated from four quinoa varieties were analyzed for physicochemical, morphological, and structural properties. All varieties of quinoa starches (QS) have lower amylose content, ranging from 9.43% to 10.90%, than maize starch (22.58%) and potato starch (17.75%) and thus has lower water solubility index and higher swelling power. QS has lower pasting temperature and setback and breakdown than maize starch. QS has lower enthalpy change (△H) and exhibits good resistance to retrogradation. In terms of rheological properties, QS has lower degree of shear-thinning and thixotropy than maize and potato starch. Additionally, QS has irregular polygon granules with small granule diameters ranging from 1.21 μm to 1.95 μm and display the A-type X-ray diffraction pattern. The crystallinity of QS ranges from 21.00% to 29.67%, which is significantly lower than that of maize starch. Fourier-transform infrared spectroscopy showed that the QS structure is a double helix and has a lower degree of order than the structures of maize and potato starch. This study revealed the particular properties of QS with four varieties as compared with other starch varieties.

Starch structure-property relations as a function of barley germination times

Two varieties of barley samples were subjected to germination conditions to investigate the underlying mechanisms underpinning changes in molecular structure, chemical compositions and thermal properties of starch during this process. Starch thermal transitions were examined using differential scanning calorimetry, and the molecular fine structure of amylose and amylopectin were determined using size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis, respectively. Both amylose and amylopectin chains were hydrolyzed during germination, but a preferential attack of amylopectin chains was observed with concomitant increases of relative amylose content, resulting in increased gelatinization temperatures (onset, peak, conclusion) and reduction in enthalpy change. Amylolytic enzyme activities increased during germination, resulting in decreased starch content. After malting, significant degradation of amylose chains followed by the reduction of gelatinization temperatures was seen. Roasting of pale malts was found to degrade starch and protein whilst completely stopping enzyme activities. The resulting coloured malts had extremely low starch enthalpy change due to the loss of amylopectin crystallinity at high temperature. This study provides insights into starch structural changes of barley throughout malting and roasting, which are determining factors for fermentable sugar production during mashing.

Effects of cold-climate environmental factors temperature and salinity on benzotriazole adsorption and desorption in bioretention cells

Benzotriazole, a common anti-corrosion additive in vehicle antifreeze products, is a polar contaminant frequently detected in urban runoff, particularly in cold seasons. Urban low impact development systems such as bioretention cells have shown promise to mitigate traditional stormwater contaminants. However, to date, their efficiency to reduce pollution by polar trace organic chemicals is unclear. In this study, the adsorption and desorption potential of benzotriazole to bioretention soil and hardwood mulch was investigated at varying temperature and salinity levels. The lower organic matter quality of bioretention mulch than soil, likely due to the dominance of lignin in the former and proteins in the latter, resulted in a higher affinity of benzotriazole on soil than mulch. The adsorption capacity increased with decreasing temperature. The low enthalpy changes of −5.6 (soil) and −14 kJ/mol (mulch) suggested adsorption via van der Waals forces and dipole-dipole interactions, respectively. Conversely, changes in salinity showed little effect on the adsorption of benzotriazole. Desorption was observed for both bioretention substrates, but was lowest at low benzotriazole concentrations. Altogether, despite low to moderate adsorption coefficients, these results showed that bioretention cells are able to retain benzotriazole particularly in cold climate conditions.

Physicochemical Properties of Hom Nil (Oryza sativa) Rice Flour as Gluten Free Ingredient in Bread.

Hom Nil (Oryza sativa), a Thai black rice, contains polyphenolic compounds which have antioxidant properties. The objective of this study was to investigate physicochemical properties of Hom Nil rice flour (HN) and its application in gluten free bread by using Hom Mali 105 rice flour (HM) as the reference. The results demonstrated that HN flour had significantly higher average particle sizes (150 ± 0.58 µm), whereas the content of amylose (17.6 ± 0.2%) was lower than HM flour (particle sizes = 140 ± 0.58 µm; amylose content = 21.3 ± 0.6%). Furthermore, HN contained higher total phenolic compounds (TPC) (2.68 ± 0.2 mg GAE/g flour), total anthocyanins (293 ± 30 mg cyanidin-3-glucoside/g flour), and the ferric reducing antioxidant power (FRAP) (73.5 ± 1.5 mM FeSO4/g) than HM flour (TPC = 0.15 mg GAE/g flour and FRAP = 2.24 mM FeSO4/g flour). In thermal properties, the onset temperature (To), the peak temperature (Tp) and the conclusion (Tc) temperature of HN flour were similar to the values of HM flour. However, HN flour had lower enthalpy change (ΔH) than HM flour. The results showed that HN flour had lower swelling power and higher solubility than HM flour at the temperature between 55 °C and 95 °C. In pasting properties, HN flour also showed lower peak, trough and breakdown viscosity than HM flour. In addition, the bread samples prepared by HN flour had higher value of hardness and lower value of cohesiveness than the bread prepared from HM flour. Taken together, the findings suggest that HN flour could be used as an alternative gluten-free ingredient for bread product.

Effect of carrier agents on the physical properties and morphology of spray-dried Monascus pigment powder

Spray drying is an economic technique used in preservation and production of Monascus pigment powder. This study was performed to encapsulate the Monascus pigment with maltodextrin using spray drying technique with three types of carrier agents: propylene glycol, mannitol and polyglycerol ester at different concentrations (0.5%, 1% and 1.5%). Analyses of particle size, the spattering behavior, microstructure, color value, and thermal profile were performed on the obtained powder. The addition of propanediol, mannitol and polyglycerol ester in combination with maltodextrin led to an increase of 17.5%, 45.8%, and 23.5% in the volume mean diameter of Monascus pigment powder, respectively. The decrease of spattering of Monascus pigment with maltodextrin was clearly evident in the case of formulations containing 1.5% polyglycerol ester. Scanning electronic microscopy analyses showed that Monascus pigment particle treated with maltodextrin exhibited microstructures that were smooth and dented, while the particles treated with carriers exhibited rough, irregular surface and adherence of smaller particles on their surfaces. UV–visible spectroscopy proved that the addition of carriers did not influence the molecular structure of Monascus pigment compared to the powder without carrier treatment. Differential scanning calorimeter analysis revealed that mannitol enhanced water vaporization during spray drying process as lower enthalpy change was observed in thermogram. The addition of an appropriate carrier (0.5%, 1.5% propanediol or 1% mannitol) improved the color values of Monascus pigment.

Effect of different reducing agents on phase formation and transformation behaviour of Ni-Ti shape memory alloy

In this study, NiTi synthesized via solid-state sintering from Ni-TiH2 powders in reducing environments using (i) CaH2 (ii) MgH2 and (iii) CaH2 and MgH2 as in situ reducing agent were investigated. The phase formation was characterized by means of scanning electron microscope (SEM), energy-dispersive spectroscope (EDS) and powder X-ray diffraction (XRD), while transformation behavior was analyzed using differential scanning calorimetry (DSC) measurement. Among these three reducing agents, synthesis in reducing environment using CaH2 as in situ reducing agent resulted in the formation of single phase NiTi with enthalpy change of 25-26 J/g, which is similar to melt-cast NiTi alloys. Specimens sintered in reducing environments using MgH2 and MgH2+CaH2 as in situ reducing agents have lower enthalpy change, ∼16-21 J/g compared to CaH2. This work established the fact that, synthesis in different reducing environment appears to have profound effects on the phase formation and transformation behavior of NiTi.

Mechanisms Underlying the Formation of Complexes between Maize Starch and Lipids.

This study aimed to reveal the mechanism of formation of complexes between native maize starch (NMS) and different types of lipids, namely palmitic acid (PA), monopalmitate glycerol (MPG), dipalmitate glycerol (DPG), and tripalmitate glycerol (TPG). The complexing index followed the order of MPG (96.3%) > PA (41.8%) > TPG (8.3%) > DPG (1.1%), indicating that MPG formed more complexes with NMS than PA, and that few complexes were formed between NMS and DPG and TPG. The NMS-PA complex presented higher thermal transition temperatures and lower enthalpy change than the NMS-MPG complex, indicating that although MPG formed more starch complexes, they had less stable crystalline structures than the complex between NMS and PA. X-ray diffraction (XRD) and Raman spectroscopy showed that both MPG and PA formed V-type crystalline structures with NMS, and confirmed that no complexes were formed between NMS and DPG and TPG. We conclude that the monoglyceride formed more starch-lipid complex with maize starch than PA, but that the monoglyceride complex had a less stable structure than that formed with PA. The di- and triglycerides did not form complexes with maize starch.

Complexation of rice starch/flour and maize oil through heat moisture treatment: Structural, in vitro digestion and physicochemical properties

This study investigated structural, in vitro digestion and physicochemical properties of normal rice starch (NRS)/flour (NRF) complexed with maize oil (MO) through heat-moisture treatment (HMT). The NRS-/NRF-MO complex displayed an increased pasting temperature and a decreased peak viscosity. After HMT, less ordered Maltese and more granule fragments were observed for NRS-/NRF-MO complex. Meanwhile, more aggregation was observed in the HMT samples with higher moisture contents. We found that higher onset temperature, lower enthalpy change and relative crystallinity of the NRS-/NRF-MO complex were associated with a higher moisture content of HMT samples. The higher moisture content of HMT was also favorable for the amylose-lipid complex formation. Differences in starch digestion properties were found for NRS-MO and NRF-MO complex. All of the NRS/NRF complexed MO after cooking showed lower rapidly digestible starch (RDS) contents compared with the control sample, therein NRS-/NRF- MO 20% exhibited the highest sum of the slowly digestible starch and resistant starch contents. In general, HMT had a greater impact on the in vitro digestion and physicochemical properties of flour samples compared with starch counterparts.

Interactions and cooperativity between P-glycoprotein structural domains determined by thermal unfolding provides insights into its solution structure and function

Structural changes in mouse P-glycoprotein (Pgp) induced by thermal unfolding were studied by differential scanning calorimetry (DSC), circular dichroism and fluorescence spectroscopy to gain insight into the solution conformation(s) of this ABC transporter that may not be apparent from current crystal structures. DSC of reconstituted Pgp showed two thermal unfolding transitions in the absence of MgATP, suggesting that each transition involved the cooperative unfolding of two or more interacting structural domains. A low calorimetric unfolding enthalpy and minimal structural changes were observed, which are hallmarks of the thermal unfolding of α-helical membrane proteins, because generally only the extramembranous regions undergo significant unfolding. Nucleotide binding increased the unfolding temperature of both transitions to the same extent, suggesting that one nucleotide binding domain (NBD) unfolds with each transition. Combined with the results from the two isolated NBDs, we propose that each DSC transition represents the cooperative unfolding of one NBD and the two contacting intracellular loops. Further, the presence of two transitions in both apo and MgATP bound wild-type Pgp suggests the NBD-dimeric conformation is transient, and that Pgp resides predominantly in the crystallographically observed inward-facing conformation with NBDs separated, even under conditions supporting continuous MgATP hydrolysis. In contrast, DSC of the vanadate-trapped MgADP·Pgp complex and the MgATP-bound catalytically inactive mutant, E552A/E1197A, show an additional transition at much higher temperature, corresponding to the unfolding of the nucleotide-trapped NBD-dimeric outward-facing conformation. The collective results indicate a strong preference for an NBD dissociated, inward-facing conformation of Pgp.

Silica-coated poly(glycidyl methacrylate-ethylene dimethacrylate) beads containing organic phase change materials

Macroporous sorbents differing in size were prepared by the 2,2ʹ-azobis(isobutyronitrile) (AIBN)-initiated suspension radical polymerization of glycidyl methacrylate and ethylene dimethacrylate in the presence of an inert porogen. The microspheres were loaded with paraffin and cetyl alcohol phase change materials (PCMs) and coated with silica by sol-gel method using trimethoxy(methyl)silane hydrolysate. The energy storing capacity of the PCM-containing composite particles was monitored by differential scanning calorimetry. Accelerated thermal cycling tests were carried out to determine the thermal reliability of the microencapsulated PCMs. Paraffin and cetyl alcohol content in the microcapsules was 42.9wt.% and 48.9wt.%, respectively. The microcomposites with higher PCM content showed correspondingly higher latent heat storage capacity (melting and solidification enthalpies were 96.1J/g and 94.5J/g, respectively). However, there was low enthalpy change observed after 1000 thermal cycles of cetyl alcohol-containing capsules, which indicated that PCM leakage from the microspheres was minimal.

Effects of granule size of cross-linked and hydroxypropylated sweet potato starches on their physicochemical properties.

Sweet potato starch was modified by cross-linking, hydroxypropylation, and combined cross-linking and hydroxypropylation, and the starches were subsequently sieved to obtain differently sized granule fractions. The effects of granule size of native and modified sweet potato starch fractions and all fractions were investigated with respect to their physicochemical properties. The large-size granule fraction (27-30 μm) showed a 16-20% higher chemical phosphorylation and a 4-7% higher hydroxypropylation than the small-size granule fraction (14-16 μm). The large-size granule fractions of native and modified sweet potato starches showed lower transition temperatures (0.7-3.1 °C for peak temperature of gelatinization) and lower enthalpy changes (0.6-1.9 J/g) during gelatinization than the small-size granule fractions, making the sweet potato starch different from cereal starches. The large-size granule fraction of native starch showed a higher paste viscosity (78-244 cP) than the corresponding small-size granule fraction. In addition, cross-linking and hydroxypropylation affected the paste viscosity of the large-size granule fraction significantly more than that of the small-size granule fraction when compared to the corresponding parental starch fractions. The large-size granule fraction of native and dual-modified starches showed a lower syneresis after freeze-thaw treatments than the small-size granule fractions. The difference in swelling power between large- and small-size granule fractions was not significant. In general, the large-size granule fraction of sweet potato starch was more susceptible for cross-linking and hydroxypropylation and the physicochemical properties were changed to a higher extent compared to the corresponding small-size granule fraction.

Monitoring Early Hydration of Cement by Ex Situ and In Situ ATR‐FTIR – a Comparative Study

Diffuse Reflection Fourier Transform Infrared (DR‐FTIR) spectroscopy has previously proven to provide time‐resolved insights into early cement hydration spanning ~30 s to ~36 h after completing the mixing. Here, a previously validated ex situ freeze‐dry procedure to stop hydration at preset times is complemented by an in situ Attenuated Total Reflectance (ATR) infrared spectroscopy method. The qualitative overall agreement between ex situ freeze‐drying and in situ monitoring is demonstrated. Moreover, water conversion during hydration comes out clearly in the time‐resolved ATR‐FTIR spectra. This information is absent in DR‐FTIR where buildups of crystal water and hydroxides are observed, while quenching of the hydration process requires removal of free water prior to acquiring the spectra. The ability of the IR technique to monitor the initial rate of hydration as a function of time is validated by comparing to calorimetry. The two approaches are understood to be complementary in that the former monitors alite grain surface hydration, while the latter reflects bulk hydration. IR is complementary to the calorimetry in cases of surface processes in conjunction with low enthalpy changes, that is, initial C–S–H formation and additive related surface chemistry.