Microstructure Of Starch Research Articles

Poly(lactic acid)/starch composites: Effect of microstructure and morphology of starch granules on performance

ABSTRACTStarches used to develop biodegradable composites belong to different botanical sources that exhibit different microstructures and morphologies. This results in confused relationship and no comparison of data for applications. In this work, the most popular ten different starches were used as model materials to investigate the relationship between starch microstructure and the performance of poly(lactic acid) (PLA)/starch composites. It was found that: (a) composites filled with either well‐sized (small‐sized and non‐agglomerated) starch granules or those containing high amylose content (G‐50 and G‐80) improves the reinforcing ability of PLA, with least reduction in deformation; (b) aggregation tendency of small‐sized starch granules can be controlled using surface modification approach that not only reduces the phase‐separation between starch and PLA but also improves the dispersion; and (c) no discernible relationship exists between the starches, from different botanical sources, and the thermal performance of PLA/starch composites. The results provide practical guidelines to develop starch‐based biodegradable composites for commercial applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45504.

Synthesis and physicochemical properties of carboxymethyl chestnut starch

Carboxymethyl chestnut starch (CMCS) was synthesized by the reaction of chestnut starch and monosodium chloroacetate in an alkali environment. The hydroxyl groups of starch were etherized through carboxymethyl groups, and the crystallinity of starch was reduced after carboxymethylation. As degree of substitution (DS) increased from 0.22 to 0.63, the degree of amyloglucosidase hydrolysis decreased from 37.0 to 1.6%, which was markedly lower than that of native chestnut starch (NCS) (83.2%). The differential scanning calorimetry results revealed the absence of a transition peak in all CMCS samples. CMCS paste showed significant higher light transmittance and freeze-thaw stability than those of NCS, and had no water release during storage at room temperature. CMCS with middle DS showed higher viscosity than NCS at high shear rate. The results demonstrated that CMCS can be applied in the industrial processing of paste foods and frozen food as a thickening agent. Practical applications Carboxymethylated starch can be used as an alternative thickener in a wide range of industrial applications. However, there is little information on the synthesis and physicochemical properties of carboxymethylated chestnut starch till now. In the present study, the carboxymethylated chestnut starch was synthesized by the optimization of process, and the microstructure, light transmittance, and freeze-thaw stability of starch were studied. We believe that starch industry can utilize the results of this study in the synthesis and application of this modified starch.

Influence of Synthesis Parameters on the Microstructure and Mechanical Property of Thermoplastic Starch

Thermoplastic starch was prepared via compression molding in a stainless steel mold having dimensions of 150 mm x 150 mm x 2mm. Thermoplastic starch was prepared by varying the compression temperature, compression pressure and duration of compression. The starch was extracted from bitter cassava (Manihot esculenta crantz), Datu 1 variety. Tensile properties of the material were found to be dependent on the specific conditions at which molding was done. Factorial analysis showed a significant effect of the temperature-pressure interaction on the tensile strength of thermoplastic starch at 95% confidence level. Thermoplastic starch prepared using the compression molding parameters of 105°C and 6.89 MPa (1000 psi) compression pressure exhibited the highest tensile strength of 464.88 kPa. However, using the molding parameters of 105°C and 6.89 MPa (2000 psi) compression pressure exhibited the lowest tensile strength of 416.64 kPa. Introduction of gelatinizing agents and compression molding up to 105 °C and 13.79 MPa (2000 psi) has partially caused the transformation of the microstructure of starch to a more amorphous state. This is shown by the disappearance of peaks at diffraction angles (2θ) of 12.45° (d1 = 0.71 nm), 14.85° (d2 = 0.6 nm), and 17.04° (d3 = 0.52 nm) and the increase in FWHM value at diffraction angle of 22.94° (d4 = 0.39 nm) from 3.05° (starch) to 11.43° (TPS).

Effects of concurrent ball milling and octenyl succinylation on structure and physicochemical properties of starch

This work concerns the effects of concurrent ball milling (BM) and octenyl succinic anhydride (OSA) modification on the starch microstructure and physicochemical properties (swelling, emulsifying, and rheological). Unlike normal OSA-modified starches, the BM/OSA-modified starch displayed new features such as reduced viscosity and rigidity but increased paste stability during shearing, heating and cooling, regardless of the substitution degree. More interestingly, while the physicochemical properties could be regulated by simply altering the BM treatment time, BM/OSA was more efficient and effective at modulating starch properties during the initial period (approx. 10h), as seen by the rapid evolutions in starch structural disruption and OSA esterification. Thus, the BM/OSA modification can serve as a viable and cost-effective approach for producing octenyl succinate starches where low viscosity (at relatively high concentrations) and high paste stability are desired.

Effect of Traditional Cooking on <i>In Vitro</i> Bioaccessibility and Microstructure of β-Carotene and Starch, in Yellow-Fleshed <i>Manihot esculenta</i>

Identification of traditional cooking methods of food that can be used as dietary interventions helps improve quality of life. This study evaluates the effects of different traditional preparation methods on in vitro bioaccessibility and microstructure of β-carotene and starch in yellow-fleshed manioc (YFM) found in Sri Lanka. Preparation methods included, boiling with water and cooking with coconut milk. The content of β-carotene and in vitro bioaccessibility of β-carotene were determined by high-performance liquid chromatography with photo Diode array detection (HPLC-DAD). Estimated glycaemic index (EGI) was determined as a measure of bioaccessibility of starch, using in vitro digestion procedures. Under Bright field microscopy it was observed that cooking with coconut milk has made much vigorous cell disruption, causing the release of starch and β-carotene out of the cells through disrupted cell walls. According to results β-carotene content was 1.04 μg/g DW (dry weight) in ‘Swarna’ variety of raw YFM. Content of β-carotene for boiled YFM and YFM curry were 0.34 and 1.07 μg/g DW respectively, but in vitro accessible β-carotene content was not detectable. EGI of YFM curry was higher (50.3) than the EGI of boiled YFM (24.6). Thus among above mentioned preparations, the best method of preparation for obese and diabetic population is boiled YFM and there is no benefit of consuming any of the above mentioned preparations of YFM as a source of vitamin A.

Characterizations of high purity starches isolated from five different jackfruit cultivars

Microstructure and physicochemical properties of starches isolated from five jackfruit cultivars (M1, M5, M6, M11, and BD) were investigated. The five jackfruit cultivars could become the origin of high purity starches which could reach above 99%. The amylose content, microstructure and particle size varied significantly in five cultivars starches (p < 0.05). The five starches should be medium (BD), small (M11, M6, M5), and very small (M1) with average particle size of 12.59, 10.12–6.62 and 4.28 μm, respectively. With the lowest amylose content, the BD starch showed higher swelling power, solubility, peak viscosity, breakdown, gelatinization enthalpy and crystallinity, but lower peak, setback, pasting and gelatinization temperature compared to the other starches. Pearson's correlation analysis indicated that there were significant positive correlations between swelling power (SP) and solubility (0.90, p < 0.01) based on amylose content and particle size. In addition, peak viscosity, breakdown showed positive correlation with SP (0.86, 0.86, p < 0.01) while final viscosity, setback and pasting temperature (Ptem) showed significant negative with SP (−0.87, −0.87, −0.90, p < 0.01). The DSC results were also consistent with the results obtained from the RVA data based on amylose content and particle size. All starches showed a typical A-type X-ray diffraction pattern. The analysis of crystal structure confirmed the DSC results that starch with medium particle size but the lowest amylose content showed a lower gelatinization temperature but higher enthalpy. All results showed the amylose content, microstructure and particle size had significant effect on the physicochemical properties of the starches.

Ultrasonic frequency effect on corn starch and its cavitation

With the same ultrasonic power, time and temperature, different ultrasonic frequency (20 kHz, 25 kHz and 20 kHz + 25 kHz) effects on the structure and properties of corn starch in water were studied, as well as its cavitation. Brabender viscometer and Scanning Electron Microscope (SEM) were used to determine the viscosity and microstructure of starch respectively. The experimental results indicated that the peak viscosity of starch without ultrasound was 1076.0BU, however it decreased by 18.87% and 17.66% with 25 kHz and 20 kHz, respectively. Ultrasound could significantly change the thermal stability, retrogradation, gel properties of starch, and caused depression on the surface of starch granules. Iodine release yield was used to present the cavitational yield at different frequencies of ultrasound. Compared to these with each single frequency ultrasound, the change of the above properties of corn starch granules microstructure with dual-frequency (20 kHz + 25 kHz) ultrasound were smaller, but had much more depression on their surfaces. Dual-frequency ultrasound produced more cavitation yields and caused faster collapse of bubbles than each single frequency. In conclusion, (20 kHz + 25 kHz) proved an more evident effect on corn starch structure and properties, and as a possible mechanism, it has more ultrasonic cavitations.

Comparison between the omnivorous jundiá catfish (Rhamdia quelen) and Nile tilapia (Oreochromis niloticus) on the utilization of dietary starch sources: Digestibility, enzyme activity and starch microstructure

Omnivorous fish utilize dietary carbohydrates better than carnivorous ones due to striking morphological and physiological differences in their digestive tracts. However, digestive tract morphology and physiology also varies among omnivorous fishes, which can lead to different dietary utilization of plant sources as well. Starch, energy, and dry matter apparent digestibility coefficient (ADC) of wheat bran, cassava residue, ground corn, and broken rice were compared between the omnivorous freshwater jundiá catfish (93.9 ± 34.0 g; mean ± standard deviation) and Nile tilapia (93.7 ± 51.6 g) by using 5 g kg− 1 chromic oxide as a diet marker. Starch ADCs were significantly higher in tilapia for all plant sources (92.02% to 99.74% versus 55.87% to 90.61%), except for wheat bran, which was similar to that found in jundiá. Starch-richer plant sources (ground corn and broken rice) showed the lowest starch digestibility for jundiá. However, ground corn provided significantly higher energy digestibility in jundiá (55.35%), as opposed to broken rice (86.59%) and ground corn (71.68%), in tilapia. Dry matter ADCs ranged from 22.89% for cassava residue in jundiá to 89.17% for broken rice in tilapia. Higher dry matter ADCs were registered in tilapia for all plant sources, except for wheat bran. Despite presenting lower starch and energy digestibilities, jundiá catfish showed an adaptive capacity to utilize starch sources by presenting significantly higher specific activity of amylase (58 U mg protein− 1 versus 29 U mg protein− 1) and maltase than Nile tilapia for all plant sources, except for wheat bran. Maltase activities in the gut of jundiá varied from 2.5 to 3.6 U mg protein− 1, depending on the plant source, while in tilapia it averaged 1.7 U mg protein− 1, regardless of the plant source. The scanning electron microscopy approach used to study the influence of fish digestion on the structure of starch granules from different plant sources revealed the presence of spherulites in the fish feces. Starch spherulite formation in jundiá intestines could be related to lower starch digestibility. Our findings demonstrate different carbohydrate digestion abilities among omnivores.

Studies on the effect of storage time and plasticizers on the structural variations in thermoplastic starch

Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications.

Impact of continuous or cycle high hydrostatic pressure on the ultrastructure and digestibility of rice starch granules

The effects of continuous or 2-cycle high hydrostatic pressure (HHP) treatments (200 and 600 MPa) on the microstructure and digestibility of rice starches were investigated. The morphological and structural changes were characterized using polarized light microscopy, scanning electron microscopy, atomic force microscopy, X-ray scattering and 13C CP/MAS NMR, and the starch digestibility was examined by in vitro hydrolysis. Results showed that HHP at 600 MPa significantly alters the microstructure and lowers the resistant starch (RS) compared with HHP at 200 MPa. Under the same pressure level, the two 15-min cycle treatment induced more structural disruption, gelatinization, disappearance of surface protrusion, and lower RS of rice starches than that of the continuous HHP treatment (30 min). Based on the results on RS, the two 15-min cycle HHP treatment at 200 MPa could be beneficial for improving the functionality of the rice starch.

Microcrystalline Cellulose as Reinforcement in Thermoplastic Starch/Poly(butylene adipate-co-terephthalate) Films

Lignocellulosic fibers or their derivatives may be used to reinforce packaging materials. The aim of this study was to assess the effect of adding microcrystalline cellulose (MCC) on the microstructure and properties of thermoplastic starch (TPS)/poly(butylene adipate-co-terephthalate) (PBAT) films. MCC concentrations of 0, 1, 3 and 5 g 100 g−1 TPS/PBAT were added to mixtures containing 56 g 100 g−1 of TPS and 44 g 100 g−1 of PBAT. The morphology of the film changed slightly and the storage modulus increased when MCC was added at the concentration of 3 g 100 g−1 TPS/PBAT. No differences were observed in the Fourier transform infrared spectra and in the crystallinity of the films without and with 3 g MCC 100 g−1 TPS/PBAT. The tensile strength (medium value 6.52 MPa), elongation at break (medium value 723.83 %) and water vapor permeability (WVP; medium value 5.68 × 10−11 g m−1 s−1 Pa−1) of the films with and without MCC showed no significant differences. The films with 3 and 5 g MCC 100 g−1 TPS/PBAT were stiffer than control film. The low interaction of MCC with the polymer matrix (mainly with PBAT), the processing technique, and the low concentration of MCC may have contributed to these results.

Synthesis and Characteristics of Graft Copolymerization of Starch-G-PAM Using A Twin-Roll Mixer as Reactor for Cornstarch with Different Amylose/Amylopectin Ratios

Abstract Starch-based superabsorbent polymers (SAPs) were produced by graft copolymerization of starch-g-acrylamide using a twin-roll mixer as reactor. This work focused on the effect of starch microstructure (amylose/amylopectin contents) from the same source (corn starch) on the graft ratio (GR), graft efficiency (GE) and Add-on (AO), as well as water absorption capability (WAC) of the SAPs, which were investigated by FTIR, NMR, gravimetric and TGA. The torque variation represented all the processing in the reactor, including compress, gelatinization, graft reaction and crosslinking. Results showed that all the starches were successfully grafted with acrylamide then crosslinked by N.N′-methylene-bisacrylamide through this technology. Both AO and GR increased with increasing amylose content. But the GE decreased with increasing amylose content, which is different from the results in the solution reaction. The higher WAC of high amylose starch-based SAP corresponds with higher AO and GR, while the higher WAC of waxy-based SAP corresponds with higher GE.

Characterization of the Micro-Structure of Rice Starch

In this study, the micro-structure of rice starch was characterized by measuring the particle-size distribution and the water vapour sorption isotherm at ambient temperature. Because of the slow adsorption and desorption processes, the application of the Jantti extrapolation method was examined. Evaluation of the isotherm was carried out by a modified Frenkel-Halsey-Hill method. A new method describing the hysteresis loop by bond number is presented.

Thermal-oxidative degradation of high-amylose corn starch

Thermal oxidation degradation of high-amylose (80 %) cornstarch has been studied using thermogravimetry analyser coupled to Fourier transform infrared spectroscopy (TG-FTIR). The linear structure of amylose provides a modal material to understand how the starch microstructure affects on the decomposition mechanisms. Kinetics of the thermal oxidation has been studied using different methods. It is found that the thermal oxidation degradation is more complex than thermal degradation, thermal oxidation degradation kinetics of the starch can be interpreted in terms of multi-step degradation mechanism, the activation energies obtain from Flynn–Wall–Ozawa (F–W–O) method and modified Coats–Redfern method are in good agreement. TG-FTIR and FTIR results confirm that the thermal oxidation mechanism of starch is a process containing long chain scission and glowing combustion.

Microstructure and characteristics of high-amylose corn starch−chitosan film as affected by composition

Edible films composed of high-amylose corn starch and chitosan were developed by casting method. The effects of the ratio of high-amylose corn starch to chitosan, concentration of glycerol and methyl cellulose on the oxygen and carbon dioxide permeation, water vapor transmission, tensile strength and percent elongation at break values of edible composite films were investigated. Film microstructure was characterized by scanning electron microscopy. The results showed that the increase of the ratio of chitosan and content of glycerol in the film forming suspensions both made the structure of films flexible, causing the decrease of tensile strength and increase of percent elongation of composite films, while showing poor water vapor barrier properties as the water vapor transmission values increased. The addition of methyl cellulose as to reinforce the structure of matrix improved the water vapor barrier properties of the edible films with the decrease of water vapor transmission from 1946 to 1668 g/(m(2)·24 h), as well as the mechanical properties were improved as expected, which could be attributed to the differentia of the interaction between methyl cellulose and other components in the film preparation as the concentration ranged from 2% (w/w) to 8% (w/w). Films with different compositions, resulting different microstructures, showed variance in barrier and mechanical properties.

Archaeobotanical studies at the Urartian site of Ayanis in Van Province, eastern Turkey

Archaeobotanical macro remains recovered from the Ayanis fortress and the outer town of the Urartian period of the Iron Age (685-645 BC), located in the area of Van (Turkey), were investigated. Most of the remains were charred due to fire. Large quantities of Hordeum vulgare L. (hulled barley), Panicum miliaceum L. (broomcorn millet), and Setaria italica (L.) P.Beauvois (foxtail millet) were found at the study site, indicating the storage of agricultural surplus. Other types of cereal remains were also recorded, including Triticum aestivum L. (bread wheat) and Secale cereale L. (rye). Ground wheat grains were also recovered and their starch microstructure under scanning electron microscope suggests that these remains represent a bulgur-like food preparation. The data suggest that in the area of Ayanis plant-based agricultural activities were based mainly on cereals in the Iron Age. The findings also include fruits of Carum carvi L. (caraway, Persian cumin), Coriandrum sativum L. (coriander), and Petroselinum crispum (Mill.) Fuss (parsley). In view of the folkloric use of these plants, it is thought that the material from Ayanis represents condiments and/or medicinal herbs used by the Urartians in Anatolia about 2600 years ago.

Starch Microstructure and Starch Hydrolysis in Barley and Oat Tempe During In Vitro Digestion

Various botanical and structural characteristics of starchy foods are considered to modify the rate of starch digestion and the glycaemic responses in humans. The main objective of the study was to examine the impact of fermented barley and oat microstructure on the rate of in vitro starch hydrolysis. A dynamic gastrointestinal model was used to estimate the degree of starch hydrolysis during in vitro digestion of fermented whole grain cereal meals. Light microscopy and confocal laser scanning microscopy were used to study the microstructural changes. In parallel to the in vitro studies, the impact of fermented barley and oats on postprandial plasma glucose responses was evaluated in a human study. Micrographs were taken during in vitro digestion experiments with fermented whole grains and compared with micrographs of boiled barley (undigested). Images showed that most of the oat starch granules were degraded after 120 min of digestion, whereas barley starch granules were less degraded, even after 180 min of digestion. The findings were confirmed by faster starch hydrolysis from the fermented oat meal, measured as maltose generated during in vitro digestion. The area under the curve (AUC) was calculated from the plotted maltose curves of the meals. AUC for barley tempe (266 ± 33) was 40 % of the AUC for oat tempe (663 ± 8) and significantly different (p < 0.007) from AUC oat tempe. The in vitro data closely resembled the AUCs for plasma glucose from the parallel human study. In terms of glucose response, the mean AUC for barley tempe was 46 % of the AUC for oat tempe in the human study. The agreement between the in vitro and in vivo data indicates the potential of the in vitro method as a tool to predict the rate of starch degradation of cereal products.

Confocal laser scanning microscopy of dextran-rice starch mixtures.

The microstructure of rice starch and dextran-rice starch mixtures was studied using confocal laser scanning microscopy (CSLM) and scanning electron microscopy (SEM). Surface pores and channels of rice starch were looked for. Channels could not be found in rice starch granules after reaction with 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde (CBQCA). Fluorescein-labeled dextran was mixed with rice starch in order to locate hydrocolloid molecules in hydrocolloid-rice starch mixtures. The results showed that FITC-dextran (ave. Mw 4000; FD4) penetrated into raw rice starch granules, with the degree of penetration varying from granule to granule. FD4 could penetrate throughout cooked rice starch granules. FITC-dextran with an average Mw of more than 10,000 could not penetrate either raw or cooked rice starch granules.

Prediction of optimal cooking time for boiled potatoes by hyperspectral imaging

Cooking of potatoes causes changes in the microstructure and composition of starch. These changes affect the interaction of light with the starch granules at different regions inside the potato. In this research, the potential of hyperspectral imaging in the wavelength range 400–1000 nm in combination with chemometric tools and image processing for contactless detection of the cooking front in potatoes has been investigated. Partial least squares discriminant analysis (PLSDA) was employed to discriminate between the pixel spectra for the cooked regions and those for the remaining raw regions. In a next step image processing techniques were applied to detect the cooking front in the images obtained by the PLSDA pixel classification. From each of the resulting images with detected cooking fronts, the ratio of the remaining raw part area over the total potato area was then calculated. Finally, the effect of the cooking time on this ratio was modeled to be able to predict the optimal cooking time. The results illustrate the potential of hyperspectral imaging as a process monitoring tool for the potato processing industry.

Microstructural and Physico-Functional Characterization of Starches from Selected Cowpea (Vigna unguiculata L. Walp.) Varieties Developed for Pest and Disease Resistance

The microstructure, physico-chemical and functional properties of legume starches affect their cooking quality as well as the texture and rheological behaviour of foods processed from them. Thus, this study sought to establish the microstructural, physico-chemical and functional properties of the native starches of four cowpea varieties - Bengpla, Asetenapa, Asontem and CR-06-07, that have been developed against disease and pest infestation. The starches were extracted from the cowpeas and their gelation capacity, pasting characteristics, solubility, swelling volume and swelling power were studied using standard analytical methods. Microstructures of the starches were examined using light microscopy. Isolated starch granules from the microstructural examination showed irregular shapes with predominance of spheroid and oval forms in varying sizes. Starch granule sizes ranged from 1.9 mm in Asetenapa to 2.9 mm in Asontem. Swelling power, solubility and swelling volume at 95°C was highest in Bengpla with Asetenapa recording the lowest. However Asontem had the highest value in terms of solubility. With the exception of gelation capacity, significant differences (P ? 0.05) were observed in all the studied parameters amongst the different cowpea varieties. Thus, the cowpea starches showed wide variations in microstructure, physico-chemical and functional properties among the studied varieties and these could be used in the selection of the varieties for specific food processing applications.