Dioscorea Starch Research Articles

Thermal Properties and Dynamic Rheological Characterization of Dioscorea Starch Gels.

Yam (Dioscorea. sp.) is an edible starchy tuber with potential for being a commercial source of starch for industrial purposes, but yam starch is underutilized. The dynamic oscillatory and thermal properties of yam starches from sixteen varieties each of Dioscorea. rotundata, Dioscora. alata, Dioscorea. bulbifera and one variety of Dioscorea. dumetorum from Nigeria were studied to determine their potential for industrial utilization. The storage modulus, loss modulus, damping factor and complex viscosity as a function of frequency (ω) of the dioscorea gels, as well as the onset temperature (To), peak gelatinization temperature (Tp), end of gelatinization (TC), and gelatinization enthalpy of the starches were determined by standard procedures. Results showed that all the dioscorea starches showed a typical elastic behavior with the magnitude of G' greater than G″ while tan δ < 1 in all varieties. Thus, the starch gels were more elastic than viscous. All the starch gels exhibited shear thinning characteristics and showed frequency (ω) independence characteristics of weak gels. D. rotundata varieties had the lowest ∆Hgel, while D. bulbifera varieties had the highest. The diversity of the visco-elastic and thermal properties of the yam starch gels from different varieties and species can be an advantage in their utilization in both food and non-food industries.

Compositional and Functional Analyses of Dioscorea Odoratissima (Bush Yam) Flour and Starch as Influenced by Pre-Treatment

Dioscorea odoratissima (DO), an under-utilized famine crop is usually cooked, either peeled or unpeeled before consumption. Information on the effect of peeling on the nutritional attributes of D. odoratissima is scanty. In this study, nutritional and functional properties of flour and starch from peeled and unpeeled DO tuber were evaluated. Flour (UF) and starch (SU) from unpeeled yam tuber was significantly higher in starch compared to peeled yam flour (PF) and starch (PS), respectively. Crude protein content was significantly higher in UF and SU, compared to PF and PS. Alkaloids, phenolics, flavonoid, tannins, and trypsin inhibitor levels were significantly higher in UF and SU compared to PF and PS. PS exhibited significantly higher solubility, pasting clarity and swelling capacity compared to SU. In vitro starch digestibility, α-amylase and α-glucosidase activities positively correlate with amylose/amylopectin ratio in both flour and starch samples. UF and SU exhibited significantly higher antioxidant activity compared to PF and PS. These data emphasize the importance of pre-treatment with regard to applicability of DO flour and starch.

Physicochemical, Morphological, and Molecular Properties of Starch Isolated from Dioscorea and Oxalis Tubers from Hidalgo State, Mexico

AbstractStarches are isolated from tubers of Dioscorea and Oxalis tuberosa (OT) grown in Hidalgo and surrounding areas. The starch particle sizes of Dioscorea bulbifera (DB) show a bimodal distribution, whereas those of Dioscorea mexicana Schidw (DM) and OT show unimodal distributions. The Dioscorea starch granules have a round shape, while those of OT have an elongated shape. Significant differences (p &lt; 0.05) in pasting properties among the starches are observed, with DB showing the lowest viscosity value and DM showing the highest viscosity value. The peak and pasting temperatures show similar patterns, with higher values observed in the Dioscorea starches than in the OT starch. The gelatinization temperature values are low in the DB starch, compared to the DM and OT starches, which is consistent with the small granule size in DB. The interval in amylose content in the starches is 25.9% to 32.3%, classifying as normal starches. Molecular analysis reveals differences in molar mass and gyration radius between the amylopectin and amylose fractions of the starches, parameters that influence the physicochemical, pasting, and enzymatic hydrolysis characteristics of starches. The characterization of the tuber starches in this study reveals the potential of these under‐used food crops.

Effect of dry heating and ionic gum on the physicochemical and release properties of starch from Dioscorea

To meet the ever increasing industrial demand for excipients with desirable properties, modified starch is regarded as an alternative to it. With this in mind, the present study focuses on the modification of starches of Dioscorea from Jharkhand (India) using dry heat treatment with and without ionic gum. Modified starches were prepared using sodium alginate (1% w/w). Native and modified starches were subjected to heat treatment at 130°C for 2h and 4h. The effect of heating and ionic gum on the properties of Dioscorea starch was investigated. The amylose content, water holding capacity, micromeritic properties, swelling power, solubility and morphology of starches were evaluated. Dry heat treatment of starches without gum showed an increment in water-holding capacity after two-hours heating, but no such increment was found after four-hours heating. Oil binding capacity of starches modified with gum varied from 62% to 78%. Strongest effect of heat treatment occurred on the morphology of starches and thereby modified starches showed distorted surface morphology. Amylose content (21.09–21.89%) found to be decreased with the addition of gum which lead to decrease in paste clarity. Starches heated with gum at high-temperature resulted in restrict swelling and slight increase in solubility. Micromeritic properties of the modified starches showed the good flow properties. Further, the modified starches were investigated for in-vitro release studies and that the thermally modified derivatives can be a good prospect in slow release formulations.

Fabrication of acetylated dioscorea starch nanoparticles: Optimization of formulation and process variables

In recent years, there has been considerable interest in developing biodegradable polymer based nanoparticles to effectively deliver a drug to a target site. Polymeric materials used for preparing nanoparticles for drug delivery must be biocompatible and preferably biodegradable. The objective of this study was to fabricate nanoparticles from acetylated dioscorea starch having particle size less than 200 nm with minimum polydispersity index (PDI). Acetylated starch was synthesized by reacting native dioscorea starch with acetic anhydride in the presence of sodium hydroxide as a catalyst. Acetylated starch nanoparticles were then fabricated by spontaneous emulsification and solvent evaporation method under high speed homogenization. A systematic investigation on independent variables revealed that solvent type, surfactant type and concentration, homogenization speed and time have significant influence on the size and polydispersity of nanoparticles. Hence, response surface methodology based on central composite design was employed to fabricate the desired nanoparticles (particle size less than 200 nm and PDI < 0.2) under optimized condition (ethyl acetate, 1.45% of Pluronic® F127, homogenization speed of ∼16,000 rpm and homogenization time of 18.25 min).

PHYSICOCHEMICAL CHARACTERIZATION OF ACID MODIFIED DIOSCOREA STARCH AND ITS EVALUATION AS DIRECTLY COMPRESSIBLE EXCIPIENT IN TABLET FORMULATION

D. abyssinica was partially hydrolyzed in 6% HCl solution at room temperature for different lengths of time, (2, 4, 8, 16, and 32 days), dried using oven- and spray- drying techniques and subsequently investigated as directly compressible excipient in paracetamol tablet formulations. Native dioscorea starch (NDS) and oven dried acid modified dioscorea starch (AMDS) exhibited poor flow characteristics, whereas spray dried AMDS was found to be free flowing powder with 21.37 ± 1.39° angle of repose and 13.24 ± 0.76 g/sec flow rate. Both swelling power and percent solubility of the starches were found to increase with increase in temperature; AMDS showed higher percent solubility of 68.53%. Lubricant sensitivity and dilution potential of spray dried NDS and spray dried AMDS were investigated by incorporating magnesium stearate and paracetamol, respectively. In tablet formulations, spray dried AMDS and Starch 1500® tablets were produced with acceptable tablet characteristics up to 1% and 0.5% magnesium stearate concentrations, respectively. The spray dried AMDS was able to accommodate up to 40% paracetamol with acceptable criteria. Thus, it can be concluded that AMDS can be used as an alternative directly compressible excipient in tablet formulations. Keywords: Dioscorea starch, acid modification, spray drying, directly compressible excipient.

Design of bilayer tablets using modified Dioscorea starches as novel excipients for immediate and sustained release of aceclofenac sodium.

Bilayer tablets of aceclofenac sodium were developed using carboxymethylated white yam (Dioscorea rotundata) starch (CWY) for a fast release layer (2.5, 5.0, and 7.5% w/w), and acid-hydrolyzed bitter yam (Dioscorea dumetorum) starch (ABY) for a sustaining layer (27% w/w). Sodium starch glycolate (SSG) and hydroxypropyl methyl cellulose (HPMC) were used as standards. The starches were characterized using Fourier Transform Infrared spectroscopy (FT-IR), particle size, swelling power, densities and flow analyses. Mechanical properties of the tablets were evaluated using crushing strength and friability while release properties were evaluated using disintegration and dissolution times. Distinctive fingerprint differences between the native and modified starches were revealed by FT-IR. Carboxymethylation produced starches of significantly (p < 0.05) higher swelling and flow properties while acid-modification produced starches of higher compressibility. Bilayer tablets containing ABY had significantly higher crushing strength and lower friability values (p < 0.05) than those containing HPMC. Crushing strength increased while friability values decreased with increase in CWY. Generally tablets containing the modified Dioscorea starches gave faster (p < 0.05) disintegration times and produced an initial burst release to provide the loading dose of the drug from the immediate-release layer followed by sustained release (300 ± 7.56–450 ± 11.55 min). The correlation coefficient (R2) and chi-square (χ2) test were employed as error analysis methods to determine the best-fitting drug release kinetic equations. In vitro dissolution kinetics generally followed the Higuchi and Hixson-Crowell models via a non-Fickian diffusion-controlled release. Carboxymethylated white yam starch and acid-modified bitter yam starch could serve as cheaper alternative excipients in bilayer tablet formulations for immediate and sustained release of drugs respectively, particularly where high mechanical strength is required.

Physicochemical properties and in vitro digestion of starches from different Dioscorea plants

Physicochemical properties (paste clarity, water-binding capacity, swelling power, solubility and thermal properties) and in vitro digestion of starches isolated from ten different Dioscorea plants were investigated. Moisture content ranged from 7.52% to 15.75% and protein content varied between 0.010% and 0.028%. All of the starches gave a typical C-type X-ray diffraction pattern except D.BY (CA-type pattern) and Dioscorea persimilis (B-type pattern) starches. The relative crystallinity of them varied from 12.02% to 51.68%. The starches displayed significant variability in thermal transition temperatures and susceptibility to in vitro digestion, and varied in rapidly digestible starch (RDS), slowly digestible starch (SDS), resistant starch (RS) contents, hydrolysis index (HI) and glycemic index (GI). The ten Dioscorea starch samples can be classified into two major clusters by hierarchical cluster analysis: one cluster with more D.PP, D.BY and D.RC, and another cluster with D. XM, D.M-1, D.M-2, D.TG, D.H, D.CJ and D.J.

Ultrasound effects on the acetylation of dioscorea starch isolated from Dioscorea zingiberensis C.H. Wright

The objective of current work is to investigate the intensification of starch towards acetylation by acetic anhydride after ultrasound treatment. Native dioscorea starch (NDS) slurry was ultrasonically treated to produce ultrasound-treated dioscorea starch (UTDS). The effects of ultrasound-treated conditions of NDS on degree of substitution (DS) of ultrasound-treated dioscorea starch acetate (UTDSA) were examined. The influences of different acetylation conditions such as reaction time, reaction temperature and the molar ratios of H2SO4 to starch on the DS of starch acetate (SA) were also investigated by comparing the DS of UTDSA with NDSA's. The results demonstrate that a higher DS value is always observed for the acetylation of UTDS sample under the same reaction conditions. Moreover, using UTDS or NDS as material, the SAs with same DS value (0.55 and 1.75) were synthesized, and their chemical structure, crystalline structure, thermal stability, and morphological properties were characterized by the Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques.

Comparison of the morphological, crystalline, and thermal properties of different crystalline types of starches after acid hydrolysis

AbstractA‐type maize starch, B‐type Fritillaria ussurensis, and C‐type Rhizoma dioscorea starches were hydrolyzed (32 days) with 2.2 N HCl. Regardless of the crystallinity level, starch with predominant B‐crystalline type was less susceptible to acid degradation than A‐type and C‐type starches, and initial rates of hydrolysis in B‐type was lower than others. The SEM and XRD results revealed that different types of starch displayed different hydrolysis mechanisms. The acid corrosion started from the exterior surface of A‐type and B‐type starches followed by the core of granules. However, the hydrogen ions primarily attacked the interior of the C‐type R. dioscorea starch granules and then the exterior. FT‐IR results confirmed that the amorphous regions in the starch granules were hydrolysed first. After 8–32 days of hydrolysis, the acid‐modified C‐type starch showed typical A‐type characteristics upon analysis of the XRD pattern. The average particle size of hydrolytic starch decreased with increasing hydrolysis time. The thermal results revealed that the hydrolytic starch showed lower ΔH than the native starch, while displaying higher peak width (Tc − To) value.

Characteristics of native and enzymatically hydrolyzed Zea mays L., Fritillaria ussuriensis Maxim. and Dioscorea opposita Thunb. starches

Comparative studies on glucoamylase hydrolysis of A-type Zea mays L., B-type F. ussuriensis Maxim., and C-type Dioscorea opposita Thunb. were carried out by scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectra and differential scanning calorimetry (DSC). Maize, Fritillaria, Dioscorea starches were hydrolyzed with glucoamylase for 2, 4, 8, 12 and 24 h, respectively. The SEM and XRD results revealed that A-type, B-type starch and C-type starch displayed different hydrolysis mechanisms. A-type starch was digested with enzyme penetrating into starch granules through natural pores on the surface and disrupted the interior of the starch granules. The glucoamylase worked by attacking the surface of B-type starch and forming cracks. When endo-corrosion occurred, the internal part of the granule was corroded through small cracks. However, the glucoamylase primarily attacked the interior of the C-type starch granules and then the exterior of starch granules. FT-IR confirmed that the amorphous regions in the starch granules are firstly hydrolyzed and could be hydrolyzed completely as long as the hydrolysis time is sufficient. The transition temperatures and enthalpy of gelatinization (Δ H gel) were determined using DSC. According to the gelatinization parameters, it could be further proved amorphous and crystalline structures were hydrolyzed.

Evaluation of the material and tablet formation properties of modified forms of Dioscorea starches

Starches obtained from four different Dioscorea species—namely, White yam (Dioscorea rotundata), Bitter yam (Dioscorea dumetorum), Chinese yam (Dioscorea oppositifolia), and Water yam (Dioscorea alata)—were modified by cross-linking, hydroxypropylation, and dual modification—cross-linking followed by hydroxypropylation. The physicochemical, material, and tablet properties of the modified starches were investigated with the aim of understanding their properties to determine their potential use for different applications. The tablet formation properties were assessed using 3D modeling, the Heckel equation, and force-displacement profiles. The analyzed tablet properties were elastic recovery, compactibility, and disintegration. The result indicates that the modifications generally increased the swelling power for all the starches in the rank order hydroxypropyl > hydroxypropylated cross-linked > cross-linked (CL) while the solubility did not show a clear-cut pattern. This indicates that hydroxypropylation generally showed the strongest effects on swelling. Furthermore, hydroxypropylation improved the hot water swelling of the CL starches. The modifications did not cause any detectable morphological change in the starch granules shape or size although slight rupture was observed in some granules. CL starch had the lowest water sorption capacity and hydroxypropylation increased the sorption capacity of the CL starches. The material property results indicate that hydroxypropylation and cross-linking did not significantly improve the flowability and compressibility but improved bonding, which resulted in an increased compaction and higher tablet crushing force even though they all disintegrated rapidly. Thus, the modified Dioscorea starches showed potentials for development as new excipients in solid dosage form design, and they could be useful as disintegrants or for Soft tableting.

Characterization of acid modified Dioscorea starches as direct compression excipient

Starches obtained from four different Dioscorea species namely White (D. rotundata), Bitter (D. dumetorum), Chinese (D. oppositifolia) and Water yam (D. alata), were modified by acid hydrolysis and the physicochemical, material and tablet formation properties of the starches were investigated with the aim of determining their usefulness as a direct compression excipient in pharmaceutical tablets. The results obtained indicate that the physicochemical, material and tablet properties of the acid modified Dioscorea starches varied considerably among the various species. Acid hydrolysis led to an increase in solubility but decrease in swelling of the starches. Acid modification also led to an increase in the compressibility of the starches when compared with the native forms of the starches. Acid modified Water and White formed intact stable tablets only at higher ρrel, max, while acid modified Chinese and Bitter formed tablets at all relative densities which could already be predicted from the deformation behaviour as analyzed by 3-D modeling. The result indicates that acid modified starch tablets showed higher crushing force and acceptable disintegration time and could therefore be useful as directly compressible excipient.

The structure of C-type Rhizoma Dioscorea starch granule revealed by acid hydrolysis method

Scanning electron microscope (SEM), X-ray powder diffraction (XRD) and cross polarisation/magic-angle spinning (CP/MAS) 13C nuclear magic resonance (NMR) have been used for the structural characterisation of C-type starch granule during acid hydrolysis. SEM shows that the amorphous areas mainly locate the core part of C-type starch granules, while the crystalline areas mainly exist in the peripheral region of starch granules. XRD analysis reveals that the B-type polymorph present in the C-type starch granule are preferentially degraded or degraded faster than the A-type polymorph. NMR spectra confirm that the amorphous regions in the starch granules are firstly hydrolysed and could be hydrolysed completely as long as the hydrolysis time is sufficient. After 40 days of hydrolysis, the acid-modified starch shows typical A-type characteristics upon analysis of the XRD pattern or the 13C CP/MAS NMR spectra.

Material and tablet properties of pregelatinized (thermally modified) Dioscorea starches

The material and tablet formation properties of pregelatinized (thermally modified) forms of four Dioscorea starches have been investigated. Dioscorea starches were pregelatinized followed by either oven drying (PS) or freeze drying (FD) and used as excipient in direct compression. The physicochemical, morphological and material properties of the pregelatinized starches have been investigated. The tablet formation properties were assessed using the 3-D modeling parameters, the Heckel equation and the force–displacement profiles. The tablet properties were evaluated using the elastic recovery, compactibility plots and the disintegration test. The results indicate that pregelatinization improved the compressibility and flowability of the Dioscorea starches. The high bulk and tap densities of PS coupled with their good flowability offer a unique possibility of the starches being used as filler in capsule formulations. The modified starches generally showed differences in their time and pressure dependent deformation behaviour. PS exhibited higher elasticity during tableting. FD Chinese and FD Bitter showed higher plasticity and low fast elastic deformation than the PS forms of the starches indicating that the FD starches undergo the highest plastic deformation. However, FD starches generally showed higher compactibility compared to the PS forms of the Dioscorea starches. While FD White and FD Water showed fast disintegration time and high compactibility, FD Chinese and FD Bitter were non-disintegrating and showed high compactibility. The high compactibility observed with the FD starches appears to be as a result of material change occurring during tableting probably due to the effect of temperature or pressure or a combination of both factors. Thus, FD White and FD Water starches could be useful when high crushing force and fast disintegration are of concern while FD Chinese and FD Bitter, which were non-disintegrating, could find application as excipients for controlled drug delivery.

The partial characterization of C-type rhizoma Dioscorea starch granule during acid hydrolysis

D. BY ( Dioscorea opposita Thunb. cv. Baiyu ) starch was treated with 2.2 mol/L hydrochloric acid for different lengths of time: 2, 4, 8, 16, and 32 days. The starch yield, morphological, crystalline and particle size distribution properties were characterized by scanning electron microscope (SEM), X-ray powder diffractometer and light scattering particle size analyzer (LSPSA). The starch recovery yield decreased gradually with the hydrolysis time increasing. The SEM results showed that the inner structure of the starch granules was preferentially hydrolyzed, then the outer part. After acid hydrolysis for 16 days, the morphology of D. BY starch changed greatly, most of the starch granules have been disintegrated into smaller fragments. The crystalline type of the D. BY starch changed from C-type to A-type after 16 days of acid hydrolysis. This was firstly found in the present study. This result indicated that the B-type polymorph in the C-type D. BY starch was firstly attacked by hydrogen ion and then the A-type polymorph. The crystallinity level increased with an increase in the hydrolysis time. In addition, the particle diameter of D. BY starch decreased from 26.8 to 18.2 μm with an increase in the hydrolysis time.

The effect of acid hydrolysis on morphological and crystalline properties of Rhizoma Dioscorea starch

Starch isolated from Rhizoma Dioscorea (Jichengerhao-JCEH) was subjected to acid hydrolysis for 2, 4, 8, 16 and 32days, respectively. The acid-thinned starch was evaluated for starch yield, morphological, crystalline and particle size distribution properties by scanning electron microscope (SEM), wide-angle X-ray powder diffractometer (WAXRD) and light scattering particle size analyzer (LSPSA). The starch yield reduced from 100% for unmodified starch to 25.5% for starch subjected to 32days of acid hydrolysis. The SEM results revealed that the hydrogen ion preferentially attacked the inner amorphous regions of the starch granules followed by the outer crystalline areas. That is why starch granules did not show any corrosions or fissures at the first stage of acid hydrolysis. The average particle size of starch decreased from 23.4 μm for unmodified starch to 19.9 μm for acid-thinned starch for 16days. Wide-angle X-ray diffraction patterns indicated that the crystalline type of starch changed from C-type to A-type after 16 days of acid hydrolysis. This result demonstrated that B-type starch present in C-type starch was firstly degraded in the process of acid hydrolysis. The degree of crystallinity of starches increased gradually following the acid thinning.

Physicochemical and Functional Properties of Starch from Two Species of Curcuma

The properties of starch extracted from two species of Curcuma viz. Curcuma zedoaria and Curcuma malabarica were studied. The starch from C. malabarica tubers was white in color, while that from C. zedoaria was slightly yellowish due to the presence of the yellow pigment, curcumin. The granule size and shape, amylose content and solubility did not show noticeable difference between starches from the two species. Both the starches possess “B” type x‐ray diffraction pattern. Curcuma zedoaria starch showed a lower peak viscosity and swelling volume when compared to C. malabarica starch. The complete removal of curcumin from C. zedoaria starch by alcohol extraction, resulted in an increase in the swelling and viscosity values close to those of C. malabarica starch. The breakdown in viscosity was quite low for both the starches and setback was higher when compared to cassava and sweet potato starches. The experiments showed that Curcuma starch resembles Dioscorea starches in most of its properties. Differential scanning calorimetry (DSC) data showed that the onset of gelatinisation was earlier for C. malabarica starch. The enthalpy of gelatinization was almost same for both the starches. The phosphorus content of Curcuma starch was quite high and similar to that of potato starch. The Curcuma starch was found to be easily digestible like arrowroot starch as seen from the in vitro α‐amylase digestibility patterns. Owing to the high viscosity stability and digestibility, it can be a potential source of starch for food and industry.

Some Physico-chemical Properties of Dioscorea Starch from Ethiopia

The chemical composition, amylose content and physio-chemical properties of dioscorea starch (Dioscorea abyssinica, Fam. Dioscoreaceae) from Ethiopia have been investigated. The proximate composition of the starch on dry weight basis was found to be 0.1% ash, 0.5% protein, 1.0% fat and 98.4% starch. The amylose content was 29.7%. Scanning electron microscopy (SEM) showed rounded granules. Particle size analysis revealed granule size distribution with a mean particle size of 29.2 μm. X-ray diffraction study showed a pattern that is typical of B-type with a distinctive maximum peak at around 17° 2 T. The moisture sorption pattern, the swelling power and the solubility values were determined and found to be lower than potato starch. Brabender viscosity curves of 6% starch paste showed a peak viscosity of 781 BU. The breakdown and retrogradation of dioscorea starch were 25 and 501 BU, respectively. DSC parameters of starch-water mixture (1:2) exhibited an onset temperature (To) of 64.2°C, a peak temperature (Tp) of 68.2°C and an endset temperature (Te) of 74.8°C. The enthalpy of gelatinization (ΔH) was 19.2 mJmg−1.

Some Physico-chemical Properties of Dioscorea Starch from Ethiopia

Some Physico-chemical Properties of Dioscorea Starch from Ethiopia