Starch as a Pore‐forming and Body‐forming Agent in Ceramic Technology

Wheat and corn starch can be used for the preparation of porous alumina ceramics via the SCC (starch consolidation casting) process, resulting in porosities ranging from > 20% to approx. 50% (using nominal starch contents of 10 – 50%, v/v), with open porosity dominating (closed porosity < 6.5%). The character of porosity and the shape of the pores corresponds to the starch granules used, but the pore size is determined by a complex interplay between starch swelling (during the body‐forming step) and pore shrinkage (during sintering of the ceramic). Typically, for low starch contents (e.g. nominal starch contents of around 10%, v/v) starch swelling is a significant effect, and the pores after sintering are larger than the size of the starch granules. For higher starch contents swelling is constrained (by limited space and/ or water availability), and the matrix shrinkage during sintering overcompensates the swelling effect, so that the final pores in the ceramic can be significantly smaller than the original starch granule size. In this paper it is shown how porosity is related to pore size. In particular, it is demonstrated that the porosity indirectly determined from image analysis (via the median pore size) is closely related to the porosity directly measured via the Archimedes method. On the other hand, mercury porosimetry measures the distribution of pore throat sizes. With increasing starch content in the suspension, the pore throat size in the as‐fired ceramic materials increases, resulting in a more open microstructure.     

Estimating the Specific Heat Capacity of Starch‐Water‐Glycerol Systems as a Function of Temperature and Compositions

Increasing interests in the use of starch as biodegradable plastic materials demand, amongst others, accurate information on thermal properties of starch systems particularly in the processing of thermoplastic starch (TPS), where plasticisers (water and glycerol) are added. The specific heat capacity of starch‐water‐glycerol mixtures was determined within a temperature range of 40‐120 °C. A modulated temperature differential scanning calorimeter (MTDSC) was employed and regression equations were obtained to predict the specific heat capacity as a function of temperature, water and glycerol content for four maize starches of differing amylose content (0—85%). Generally, temperature and water content are directly proportional to the specific heat capacity of the systems, but the influence of glycerol content on the thermal property varied according to the starch type.     

Synthesis and evaluation of physicochemical properties of cross‐linked Phaseolus aconitifolius starch

Highly substituted moth bean starch (MBS) phosphate ester was synthesized using POCl₃ as cross‐linking reagent. Titrimetric and FT‐IR spectral analysis was used to characterize the substitution. The physicochemical properties of cross‐linked moth bean starch (CLMBS) were done by using X‐ray powder diffractometer (XRD), thermogravimetric analysis (TGA) and swelling study at various temperatures. The change in starch morphology was done using scanning electron micrograph (SEM), and found that it lost its crystallinity after cross‐linking. The results revealed that crystalline nature of native MBS was transformed into amorphous after cross‐linking. TGA report exhibited higher thermal stability, which make it suitable for various industrial applications. Swelling behavior showed high swelling at low temperatures (30 and 60°C) as compared to at high temperature (90°C).     

Physicochemical,crystallinity, pasting and thermal properties of heat‐moisture‐treated pinhão starch

The effect of heat‐moisture treatment (HMT) on the properties of pinhão starches under different moisture and heat conditions was investigated. The starches were adjusted to 15, 20 and 25% moisture levels and heated to 100, 110 and 120°C for 1 h. The X‐ray diffractograms, swelling power, solubility, gel hardness, pasting properties and thermal properties of the native and HMT pinhão starches were evaluated. Compared to native starch, there was an increase in the X‐ray intensity and gel hardness of HMT starches, with the exception of the 25% moisture‐treated and 120°C heat‐treated starch. HMT reduced the swelling power and solubility of the pinhão starches when compared to native starch. There was an increase in the pasting temperature, final viscosity and setback and a decrease in the peak viscosity and breakdown of HMT pinhão starches compared to native starch. HMT increases the gelatinisation temperature of native pinhão starch and reduces gelatinisation enthalpy.     

Synthesis,characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) were prepared from cassava starch by graft copolymerization of acrylamide on to starch using ceric ammonium nitrate (CAN) as free radical initiator, followed by alkali saponification. The reaction parameters such as concentration of acrylamide, concentration of CAN, temperature, and duration of polymerization reaction were optimized for maximum water absorbency using a 4‐factor 3‐level Box‐Behnken design. The highest values of percentage grafting and absorbency obtained were 174.8% and 425.2 g/g, respectively. The polymers were characterized by determination of grafting efficiency, N‐content, acrylamide content, FTIR analysis, SEM and XRD analyses. Thermogravimetric analysis (TG) showed that the SAP has higher thermal stability. The rate of water absorbency and the swelling behaviour of the SAP under different conditions of pH, and different salts were determined. The de‐swelling pattern of the hydrogels over different time durations was also determined.     

Physico‐chemical characterization of starches extracted from potatoes of the group Phureja

Starch was extracted from twenty‐four accessions of Group Phureja cultivated diploid potatoes, and from two commercial potato (Solanum tuberosum) varieties. Extracted starch samples were characterized and compared to industrial potato starch. Starch from Phureja generally exhibited smaller granule sizes and lower phosphorus content than starch from commercial potatoes. Amylose content and thermal properties (gelatinization temperature and enthalpy) were however in the same range for both groups. Starches from Phureja displayed very distinct pasting behavior from that of commercial potato. The former exhibited lower initial pasting viscosity but higher shear resistance. This may be related to lower starch granule size, causing lower swelling power and solubility. Iodine complexation results seem to indicate that phureja potatoes have higher proportion of amylopectin long chains. Phureja thus appears to be a promising new source of starch with specific physico‐chemical and functional properties intermediate between industrial potato and cereal starches.     

Effect of miniemulsion cross‐linking and ultrasonication on properties of banana starch

Miniemulsion technique has been widely used to prepare cross‐linked starch microsphere for food application. The objective of this study was to examine the effect of miniemulsion and ultrasonic treatment on the morphological, physicochemical and thermal properties of banana starch. Results showed that the miniemulsion cross‐linked banana starch (MCBS) exhibited lower swelling power (SP) and solubility (S) but higher gelatinisation enthalpy (ΔH_gel) than native banana starch. Ultrasonic treatment conditions (amplitude and time) did not show any significant difference in SP and ΔH_gel of MCBS. Ultrasonicated MCBS showed rough surfaces and slight fragmentations without any change in particle size. At gelatinisation temperature (80 °C), the SP and S of MCBS were higher than those at 29 °C. Moreover, MCBS with ultrasonic treatment showed a lower range in the gelatinisation temperature (ΔT) than untreated. The FT‐IR spectrums revealed that MCBS were fully cross‐linked and had high extent of hydrogen bonding.     

Effects of Compositional and Granular Properties on the Pasting Viscosity of Rice Starch Blends

The changes in swelling power and pasting properties of suspensions of starch blends were studied in dependence on starch composition and at various isothermal temperatures (T_iso). Samples were prepared by mixing rice starches from Kaoshiung Sen 7 (KSS7, a high‐amylose‐content variety) and Taichung waxy 70 (TCW70, a waxy variety). Generally, mixing these starches at a comparable ratio caused significant decrements in overall swelling power, onset temperature of gelatinization or viscosity rise, and final viscosity of hot pastes after 30 min of isothermal stirring. Notable increases in the peak and conclusion temperatures of gelatinization and in the peak viscosity of the pastes were also observed. Generally, all viscosity parameters of the blends showed two linear dependencies on the starch composition, the graphs intersecting at a critical starch composition depending on the parameters concerned. The onset temperature of viscosity increase was related to the volume fraction of swollen granules when they were just closely packed in suspension. The volume fraction of KSS granules was smaller than that of TCW70. In addition, the rate of viscosity increase and the peak viscosity of the starch suspensions could be well described in terms of the swelling power (Q) when Q ≤ ∼27, and depending on the T_iso examined. From the photomicrographs of starch suspensions, the extensive shear‐induced disintegration of TCW70 granules in the co‐existence of rigid KSS7 granules was evident and in turn responsible for the reduced final viscosities of the hot pastes obtained from starch blends.     

Synthesis and Characterization of Cross‐linked Carboxymethyl Potato Starch Ether Gels

Hydrogels were synthesized by cross‐linking of potato starch (PS) with dichloroacetic acid (DCA) in the presence of monochloroacetic acid (MCA) to form etherified carboxymethyl starch (CMS) gels, to be used for ultrasonic medical examinations. By etherification cross‐linked CMS‐hydrogels can be produced, that are stable in contrast to the in the long‐term unstable esterified gels, that were presented in the last paper. The rheological benchmarks for the CMS‐hydrogels were set in comparison with synthetic ultrasonic gels. Gels with potato starch contents in the reaction batch ranging from 12.5% to 20% showed the best compliance with the benchmark parameters. The DS values of these CMS‐hydrogels vary from 0.42 to 0.49, increasing with decreasing amount of starch in the reaction mixture. The free swelling capacities (FSC) vary between 77 g/g for the 12.5% PS‐gel and 34 g/g for 20% PS‐gel, the turbidities of the samples being in the range from 14.5 NTU (Nephelometric Turbidity Units) (12.5% PS) up to 20.5 NTU (20% PS). The variation of the PS fraction in the reaction mixture showed that with an increased amount of PS in the reaction batch the number of cross‐links of the CMS‐gels increases, too. At a higher number of cross‐links the swelling capacity is reduced and the concentration needed to form stable hydrogels is greatly increased. Thus a hydrogel of a polymer concentration of 5 mass‐% from a 12.5% PS batch was produced, that showed the best accordance with the rheological benchmark parameters such as gelatinization time, visco‐elastic and pseudoplastic properties and long‐term stability. The ultrasonic pictures taken with this CMS‐gel were not different from those taken with the synthetic gels. This hydrogel was then subjected to long‐term‐stability measurements performed over one year and to rheological temperature cycle tests. The tests showed that the long‐term stability of the gels is sufficient for their use as ultrasonic gel.     

发芽小米淀粉热分解机制及动力学研究

发芽是改善谷物品质的绿色加工方法。为了探究发芽对小米淀粉热力学性质的影响,采用差示量热扫描法、热重分析法对发芽小米淀粉的热分解机制及其动力学行为进行了研究。结果表明,小米发芽后淀粉糊化温度升高,糊化焓、回生度、回生速率均减小;未处理及发芽处理小米淀粉热分解均是一个连续的过程,热分解温度范围为295~360℃,分解速率最快的温度范围为298.49~305.01℃;发茅小米淀粉活化能、指前因子、焓值、熵值(绝对值)及吉布斯自由能均较未处理小米淀粉减小;未处理及发茅小米淀粉热分解最概然机制函数均为G(α)=lnα,最概然机制为单分子消除反应,为一级反应。     

Properties of Low‐substituted Cationic Starch Derivatives Prepared by Different Derivatisation Processes

Cationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution ¹³C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid. The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different. The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.     

Physicochemical Properties of Non‐thermally Cross‐linked Corn Starch with Phosphorus Oxychloride using Ultra High Pressure (UHP)

Corn starch (20%, w/w) was non‐thermally and conventionally cross‐linked with phosphorus oxychloride (POCl₃; 0.01, 0.05, or 0.1%, based on dry weight of starch) at 400 MPa for 5, 15 and 30 min and at 45°C for 2 h, respectively. Swelling power and solubility of both non‐thermally and conventionally cross‐linked corn starches were relatively lower than those of native corn starch. The pressure holding time did not affect the solubility and swelling power of non‐thermally cross‐linked corn starches. X‐ray diffraction patterns and relative crystallinity were not significantly altered by both conventional and non‐thermal cross‐linking. DSC thermal characteristics of both non‐thermally and conventionally cross‐linked corn starches were not significantly changed indicating that the double helical structure of amylopectin was not influenced by both conventional and non‐thermal cross‐linking reactions. Both non‐thermal and conventional cross‐linking greatly affected the Rapid Visco Analyser (RVA) pasting properties, such as increase in pasting temperature and decrease in peak viscosity compared to native starch. This result suggests that in case of cross‐linking using POCl₃, both non‐thermal and conventional methods result in similar physicochemical properties and non‐thermal cross‐linking with POCl₃ can reduce the reaction time from 2 h to 15 min. This work shows the potential and possibility of non‐thermal starch modification and provides the basic and scientific information on the physicochemical properties of non‐thermally cross‐linked corn starches with phosphorus oxychloride using UHP.     

Resistant Starch‐rich Powders Prepared by Autoclaving of Native and Lintnerized Banana Starch: Partial Characterization

Powdered preparations enriched in resistant starch (RS) were obtained from native and lintnerized (prolonged acid treatment) banana starches by consecutive autoclaving/cooling treatments. The preparations were tested for indigestible starch content, swelling and solubility properties, thermal analysis and pasting profile. The autoclaved samples had higher RS content than their parental counterparts, but the chemical modification (lintnerization process) allowed development of higher RS proportions (19%, dry matter basis, dmb). The autoclaved samples (RS‐enriched products) showed similar swelling values (α = 0.05) at the temperatures assessed. These RS‐rich products exhibited a lower solubility in water than the corresponding raw materials. The peak temperatures of the thermal transition were 155.5 and 145.8°C for native autoclaved and lintnerized autoclaved starch, respectively. These values indicate that RS products have a marked thermal stability. The pasting behavior of the RS products was less pronounced than that of the raw counterparts. Hence, their potential use as processed food ingredients should not impact final product viscosity. These RS‐enriched products appear suitable for the formulation of functional foods.     

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP < 14) favoured swelling. Starch pasting behaviour of 5.0 and 8.0% starch suspensions was studied using Rapid Visco Analyser (RVA). For 5.0% suspensions, increased levels of high-MW AP and decreased levels of AM molecules led to higher peak viscosity. Longer AP chains (DP > 18) depressed peak viscosity, while short chains (DP < 14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (ΔH_retro) and peak and conclusion temperatures of retrogradation (T_p,retro and T_c,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature.     

Response surface optimization and characteristics of Indica rice starch‐based fat substitute prepared by α‐amylase

Response surface methodology (RSM) was used to study the effect of enzyme to substrate ratio (11.8–23.6 U α‐amylase/g rice starch), hydrolysis temperature (90–100°C) and pH value (6.0–6.6) on the gel strength of rice starches‐based fat substitute using α‐amylase hydrolysis. The optimum conditions obtained from response surface analysis was 16.52 U/g enzyme dosage, 92°C hydrolysis temperature while the influence of pH was found insignificant in the range tested. Under these optimum conditions, the gel strength of this fat substitute was 113 g/cm², very close to the gel strength of butter of 114 g/cm², while the solubility of the substitute was 1.33 ± 0.01% and the swelling power 4.85 ± 0.02. There were no observable differences in the granular size distribution between the untreated rice starch and the hydrolyzed rice starch. Rheological properties of this rice starch‐based fat substitute implied that it is easier for the substitute to form three‐dimensional networks under 34°C.     

Pasting Properties of Non‐waxy Rice Starch‐Hydrocolloid Mixtures

The swelling and pasting properties of non‐waxy rice starch‐hydrocolloid mixtures were investigated using commercial and laboratory‐generated hydrocolloids. The swelling power of the rice starch‐hydrocolloid mixtures was generally depressed at low concentration of hydrocolloids (0–0.05%), but increased directly with increasing hydrocolloid concentrations (0.05–0.1%). In gellan gum dispersion, the swelling power at 100°C was higher than that of control. The rice starch‐hydrocolloids mixtures showed shear‐thinning flow behavior (n = 0.26–0.49). Hydrocolloids except the exopolysaccharide from S. chungbukensis (EPS‐CB) increased apparent viscosity and consistency index (K) of rice starch dispersions, but decreased the n value. Hydrocolloids enhanced the trough and final viscosity of rice starch dispersions but EPS‐CB reduced the viscosity of rice starch pastes. Hydrocolloids lowered peak viscosity but addition of guar gum resulted in high peak viscosity, apparent viscosity, and consistency index of rice starch dispersions. Total setback viscosity appeared to be not affected by hydrocolloids at low concentration (0.05%). The hot and cold paste of the starch‐gellan gum mixture exhibited the highest viscosity values in the Brookfield viscometer.     

Synthesis of Starch Copolymers by Silicon Tetrachloride Plasma‐Induced Graft Polymerization

Corn starch was surface‐functionalized by 13.56 MHz RF SiCl₄‐plasma, in situ reacted with ethylenediamine for stabilization, and subsequently graft‐polymerized using dichlorodimethylsilane as monomer. SiCl₄‐plasma treatment was studied and discharge parameters were optimized. X‐ray photoelectron spectroscopy (XPS/ESCA), Fourier transformed infrared spectroscopy (FTIR), scanning electron spectroscopy (SEM), gas chromatography/mass spectroscopy (GC‐MS), and differential thermal analysis/thermal gravimetry (DTA/TG) proved the presence of a polydimethylsiloxane (PDMS) graft‐copolymer layer on the modified starch‐granule surfaces. These analyses show that the surface morphology of starch granules, the thermal properties, the swelling characteristic, and the hydrophilicity of starch were all changed due to the existence of a protective hydrophobic PDMS layer. It is suggested that the starch graft‐copolymer might find its applications as reinforcing component in silicone‐rubber materials for starch‐based composites.     

Investigations of the Great Northern Bean (Phaseolus vulgaris L.) Starch: Solubility, Swelling, Interaction with Free Fatty Acids, and Alkaline Water Retention Capacity of Blends with Wheat Flours

The solubility and swelling of Great Northern bean (Phaseolus vulgaris L.) starch was both temperature and pH dependent. Acetylation of starch decreased the solubility while oxidation increased the solubility as a function of temperature. Solubility of purified starch was highest at pH 6.0. Over a temperature range 60–90°C, acetylation increased swelling while oxidation reduced it. Both acetylation and oxidation resulted in reduced swelling of starch over a pH range 2–10. Addition of fatty acids (palmitic, stearic, and linoleic) to the purified starch reduced the Brabender Amylograph viscosity and raised the gelatinization temperature of starch. Replacement of wheat flours by starch increased the alkaline water retention capacity to a similar extent for the two flours tested.     

Production process of wood-based materials for SiC Ceramics

The possibility of fabricating SiC ceramics using special wood-based materials has been shown in previous research. To form accurate SiC bodies from wood-based green templates, special shaping techniques are necessary to fulfill the requirements on the finished ceramic products. Due to the fact that wood-based green templates undergo shrinkage during carbonization, no suitable forming processes for the wood-based green templates have been presented so far. In this publication different raw materials and 3D shaping production processes and their influence on green body properties are described. It was possible to produce green bodies with a MOR higher than 15 N/mm² and a density in the range above 0.82 g/cm³. It is shown that reduction of resin content decreases the strength significantly and a reduction to 30 mass % resin content reduces the MOR of flat pressed panels to the defined limit. The extruded samples showed a significantly lower strength (mean 18.1 N/mm², standard deviation 8.6 N/mm²). Injection molding was not applied successfully. The findings show that shape pressing and extrusion were applied successfully, but the green body properties differed significantly from the results achieved by flat pressing.     

Physical and Swelling Properties of Spray‐Dried Powders made from Starch and Poly(vinyl alcohol)

The aim of this study was to investigate whether starch and poly(vinyl alcohol) could be compatible in a powder for coating. Free films of a mixture of the polymers were produced by casting and investigated with respect to their mechanical properties and moisture uptake. The moisture uptake was substantially higher when glycerol was added and the glycerol‐containing films had a lower failure stress under tension than the corresponding glycerol‐free films. At glycerol levels of 20 wt% or above, the glycerol content resulted in a high strain to failure. Dry powders with and without glycerol were made from the starch/poly(vinyl alcohol) solutions by spray drying. The powders were investigated by differential scanning calorimetry (DSC), to determine the degree of physical ageing or crystallinity. All powders showed a broad peak indicative of the melting of crystals at 100–150°C in the first scan, but this peak disappeared almost completely after rapid cooling. The glycerol‐free powder showed a small endothermic peak at about 45°C, indicating physical ageing of the powders during storage. Suspensions of the powders in a liquid plasticiser (glycerol or poly(ethylene glycol)) showed a sharp increase in storage modulus at a certain temperature, indicating the onset of swelling. The observed swelling meant that some of the powders are good candidates for plastisol coatings.