Microstructure of Seeds,Flours, and Starches of Legumes

The microstructure of cotyledons and flours of both garbanzo beans and peas were examined by a scanning electron microscope (SEM) at low and high magnification. While the cells in the outer layer of the cotyledon were elongated and tightly packed in both garbanzo beans and peas, they were rounder and more loosely packed in the central part of the cotyledon, with many intercellular spaces. Cotyledon cells of garbanzo beans were smaller than those of the pea cultivars. Flour fractions from the inner layer of the cotyledon of garbanzo beans and pea cultivars had much finer particles; were lower in protein, lipid, ash and fiber; and contained more starch than those from the outer layer of the cotyledon. In prime starches isolated from garbanzo beans and smooth peas, protein, free lipid, and ash were lower than 0.41, 0.11, and 0.17%, respectively, indicating that the starches are highly pure. Garbanzo bean starch had smaller and smoother granules than those of smooth peas. Starch granules of wrinkled pea cv. Scout had a unique shape, with deep fissures and grooves, which could be partly responsible for difficulties encountered during the wet fractionation process.     

Characteristics of Granular Cold‐Water Gelling Starches of Cereal Grains and Legumes Prepared Using Liquid Ammonia and Ethanol

Starches of wheat, corn, smooth and wrinkled peas, and chickpeas were modified to a free‐flowing powder of granular cold‐water gelling (GCWG) starch using liquid ammonia and ethanol at 23°C and atmospheric pressure. Amylose content of starches was 26.3% in wheat, 27.1% in corn, 35.4% in chickpeas, 43.2% in smooth peas, and 79.9% in wrinkled peas. The modified starches remained in granular form with an increased number of grooves and fissures on the surface of the granules compared with native starch, while the crystallinity was mostly lost, as shown by X‐ray diffractograms and DSC endothermic enthalpies. Pasting viscosity of modified starches at 23°C was 171 BU and 305 BU in wheat and corn, respectively, and much higher in legume starches, ranging from 545 BU to 814 BU. Viscosities of modified legume starches at 23°C were at least twice as high as those of native starches determined at 92.5°C. Swelling power of modified starches at 23°C ranged from 8.7 g/g to 15.3 g/g, while swelling power of native starches heated to 92.5°C ranged from 4.8 g/g to 16.0 g/g. GCWG starches exhibited higher dextrose equivalent (DE) values of enzymatic hydrolysis, ranging from 25.2 to 27.0 compared with native starches (1.5–2.9). Modified starches from wheat, corn, smooth peas, and chickpeas formed weak gels without heat treatment and experienced no changes in gel hardness during storage, while native starch gels formed by heat treatment showed an increase in hardness by 1.1–7.5 N during 96 hr of storage at 4°C.     

Composition,Molecular Structure,Properties, and In Vitro Digestibility of Starches from Newly Released Canadian Pulse Cultivars

Pulse starches were isolated from different cultivars of pea, lentil, and chickpea grown in Canada under identical environmental conditions. The in vitro digestibility and physicochemical properties were investigated and the correlations between the physicochemical properties and starch digestibility were determined. Pulse starch granules were irregularly shaped, ranging from oval to round. The amylose content was 34.9–39.0%. The amount of short A chains (DP 6‐12) of chickpea starch was much higher than the other pulse starches, but the proportions of B1 and B2 chains (DP 13‐24 and DP 25‐36, respectively) were lower. The X‐ray pattern of all starches was of the C type. The relative crystallinity of lentil (26.2–28.3%) was higher than that of pea (24.4–25.5%) and chickpea starches (23.0–24.8%). The swelling factor (SF) in the temperature range 60–90°C followed the order of lentil ≈ chickpea > pea. The extent of amylose leaching (AML) at 60°C followed the order of pea ≈ chickpea > lentil. However, in the temperature range 70–90°C, AML followed the order of lentil > pea > chickpea. The gelatinization temperatures followed the order of lentil > pea > chickpea. The peak viscosity, setback, and final viscosity of pea starch were lower than those of the other starches. Lentil starch exhibited lower rapidly digestible starch (RDS) content, hydrolysis rate, and expected glycemic index (eGI). The resistant starch (RS) content of both lentil cultivars was nearly similar. However, pea and chickpea cultivars exhibited wide variations in their RS content. Digestibility of the pulse starches were significantly correlated (P < 0.05) with swelling factor (60°C), amylose leaching (60°C), gelatinization temperature, gelatinization enthalpy, relative crystallinity, and chain length distribution of amylopectin (A, B1, and B2 chains).     

Wet Fractionation of Garbanzo Bean and Pea Flours

Garbanzo bean and pea flours originating from the central part of the cotyledons were higher in starch but lower in protein and fiber than those from the outer layer of the cotyledon. These flours were fractionated by the wet process into prime starch, tailing starch, and solubles. The patented wet-fractionation method was successfully modified to reduce the total amount of water during the process. The modified process produced comparable yield and purity of separated fractions. Under the recycling water method, the yields of prime starch were 46.7, 33.6, and 41.1%, respectively, in garbanzo bean and two smooth pea cultivars (Latah and SS Alaska). Isolated prime starches were <0.4% in protein and <0.19% in ash, indicating high purity.     

Structure and Functionality of Barley Starches

Amylose contents of prime starches from nonwaxy and high-amylose barley, determined by colorimetric method, were 24.6 and 48.7%, respectively, whereas waxy starch contained only a trace (0.04%) of amylose. There was little difference in isoamylase-debranched amylopectin between nonwaxy and high-amylose barley, whereas amylopectin from waxy barley had a significantly higher percentage of fraction with degree of polymerization < 15 (45%). The X-ray diffraction pattern of waxy starch differed from nonwaxy and high-amylose starches. Waxy starch had sharper peaks at 0.58, 0.51, 0.49, and 0.38 nm than nonwaxy and high-amylose starches. The d-spacing at 0.44 nm, characterizing the amylose-lipids complex, was most evident for high-amylose starch and was not observed in waxy starch. Differential scanning calorimetry (DSC) thermograms of prime starch from nonwaxy and high-amylose barley exhibited two prominent transition peaks: the first was >60°C and corresponded to starch gelatinization; the second was >100°C and corresponded to the amylose-lipid complex. Starch from waxy barley had only one endothermic gelatinization peak of amylopectin with an enthalpy value of 16.0 J/g. The retrogradation of gelatinized starch of three types of barley stored at 4°C showed that amylopectin recrystallization rates of nonwaxy and high-amylose barley were comparable when recrystallization enthalpy was calculated based on the percentage of amylopectin. No amylopectin recrystallization peak was observed in waxy barley. Storage time had a strong influence on recrystallization of amylopectin. The enthalpy value for nonwaxy barley increased from 1.93 J/g after 24 hr of storage to 3.74 J/g after 120 hr. When gel was rescanned every 24 hr, a significant decrease in enthalpy was recorded. A highly statistically significant correlation (r = 0.991) between DSC values of retrograded starch of nonwaxy barley and gel hardness was obtained. The correlation between starch enthalpy value and gel hardness of starch concentrate indicates that gel texture is due mainly to its starch structure and functionality. The relationship between the properties of starch and starch concentrate may favor the application of barley starch concentrate without the necessity of using the wet fractionation process.     

Role of Phosphorus in Viscosity,Gelatinization, and Retrogradation of Starch

The effect of starch crystallinity and phosphorus on starch gelatinization and retrogradation were studied using wide-angle X-ray powder diffraction, cross polarization/magic angle spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR) spectroscopy, ³¹P NMR spectroscopy, Rapid Visco Analyzer (RVA) and differential scanning calorimetry (DSC). Two starches differing significantly in peak viscosity (cv. Stephens, 283 BU; cv. Crew, 560 BU) were comparable in amylose content and starch crystallinity, while differing significantly in phospholipids content. Starch of lower peak viscosity had a higher phospholipids content and showed a slower rate of retrogradation. Starch from Stephens (0.098% phosphorus) had an enthalpy value of retrograded starch of 2.2 J/g after 14 days of storage, while starch from Crew (0.062% phosphorus) had an enthalpy value as high as 4.4 J/g. Defatting with a hot n-propanol and water (3:1) mixture caused substantial changes in peak viscosity. Peak viscosity for starch from Crew decreased by 75 RVU due to defatting, while starch from Stephens decreased by as much as 125 RVU. After defatting with the hot n-propanol water mixture, the rate and extent of starch retrogradation were comparable between the prime starches, which differed significantly in peak viscosity.     

Effect of Amylose Content on Gelatinization,Retrogradation, and Pasting Properties of Starches from Waxy and Nonwaxy Wheat and Their F1 Seeds

We studied the effect of amylose content on the gelatinization, retrogradation, and pasting properties of starch using wheat starches differing in amylose content. Starches were isolated from waxy and nonwaxy wheat and reciprocal F1 seeds by crossing waxy and nonwaxy wheat. Mixing waxy and nonwaxy wheat starch produced a mixed starch with the same amylose content as F1 seeds for comparison. The amylose content of F1 seeds ranged between waxy and nonwaxy wheat. Nonwaxy‐waxy wheat had a higher amylose content than waxy‐nonwaxy wheat. Endothermic enthalpy and final gelatinization temperature measured by differential scanning calorimetry correlated negatively with amylose content. Gelatinization onset and peak temperature clearly differed between F1 and mixed starches with the same amylose content as F1 starches. Enthalpy for melting recrystallized starches correlated negatively with amylose content. Rapid Visco Analyser measurement showed that F1 starches had a higher peak viscosity than waxy and nonwaxy wheat starches. Mixed starches showed characteristic profiles with two low peaks. Setback and final viscosity correlated highly with amylose content. Some of gelatinization and pasting properties differed between F1 starches and mixed starches.     

Comparison of Physical Properties of Wheat Starch Gels with Different Amylose Content

The effects of amylose content and other starch properties on concentrated starch gel properties were evaluated using 10 wheat cultivars with different amylose content. Starches were isolated from grains of two waxy and eight nonwaxy wheat lines. The amylose content of waxy wheat lines was 1.4–1.7% and that of nonwaxy lines was 18.5–28.6%. Starch gels were prepared from a concentrated starch suspension (30 and 40%). Gelatinized starch was cooled and stored at 5°C for 1, 8, 16, 24, and 48 hr. The rheological properties of starch gels were studied by measuring dynamic viscoelasticity with parallel plate geometry. The low‐amylose starch showed a significantly lower storage shear modulus (G′) than starches with higher amylose content during storage. Waxy starch gel had a higher frequency dependence of G′ and properties clearly different from nonwaxy starches. In 40% starch gels, the starch with lower amylose showed a faster increase in G′ during 48 hr of storage, and waxy starch showed an extremely steep increase in G′. The amylose content and concentration of starch suspension markedly affected starch gel properties.     

Properties of Starches from Near‐Isogenic Wheat Lines with Different Wx Protein Deficiencies

To determine the effect of amylose content on the starch properties, the amylose content, pasting properties, swelling power, enzymatic digestibility, and thermal properties of partial and perfect waxy types along with their wild‐type parent were analyzed. As expected, amylose content decreases differently in response to the loss of each Wx gene, showing the least response to Wx‐A1a. Most of the characteristics, except the thermal properties of the amylose‐lipid complex in differential scanning calorimetry (DSC), differed significantly among the tested types. Furthermore, the breakdown, setback, and pasting temperatures from the Rapid Visco Analyser (RVA) and the enzymatic digestibility, swelling power, peak temperature, and enthalpy of starch gelatinization from DSC showed a correlation with the amylose content. The relationships between the peak viscosity from the RVA and the onset temperature of starch gelatinization determined by DSC with amylose content of the tested materials were not clear. Waxy starch, which has no amylose, showed a contrasting behavior in starch gelatinization compared with nonwaxy starches. Among the nonwaxy starches, lower setback, lower pasting temperature, higher enzyme digestibility, higher peak temperature, higher enthalpy of starch gelatinization, and higher swelling were generally associated with low amylose starches.     

Effect of Dry Heating on Physicochemical Properties of Pregelatinized Rice Starch

Japonica and indica rice starches (10% w/w) were pregelatinized in a boiling water bath for 5 or 10 min and subsequently heat‐treated in a dry state for 0, 1, 2, or 3 h at 130°C to examine the effects of dry heating on pasting viscosity, paste clarity, thermal properties, X‐ray diffraction pattern, and gel strength of pregelatinized starches. Heat treatment obviously changed the physicochemical properties of pregelatinized rice starch. The pregelatinized rice starches had higher peak viscosity and final viscosity than the corresponding native rice starches. Heat treatment of pregelatinized rice starch for 1 h increased the peak viscosity, but treatment for 2 or 3 h decreased the peak viscosity compared with the unheated pregelatinized rice starch. The indica rice starch exhibited more substantial changes in pasting viscosity than did japonica rice starch during heat treatment. The melting enthalpy of the endothermic peak occurred at 90–110°C, and the intensity of the X‐ray diffraction peak at 20° was increased by dry heating, possibly owing to the enhanced amylose‐lipid complexes. The dry heat treatment of pregelatinized starch caused an increase in paste clarity and a decrease in gel strength.     

Comparison of Physicochemical Properties and Structures of Sugary‐2 Cornstarch with Normal and Waxy Cultivars

Starches from normal, waxy, and sugary‐2 (su2) corn kernels were isolated, and their structures and properties determined. The total lipid contents of normal, waxy, and su2 corn starches were 0.84, 0.00, and 1.61%, respectively. Scanning electron micrographs showed that normal and waxy corn starch granules were spherical or angular in shape with smooth surfaces. The su2 starch granules consisted of lobes that resembled starch mutants deficient in soluble starch synthases. Normal and waxy corn starches displayed A‐type X‐ray patterns. The su2 starch showed a weak A‐type pattern. The chain‐length distributions of normal, waxy, and su2 debranched amylopectins showed the first peak chain length at DP (degree of polymerization) 13, 14, and 13, respectively; second peak chain length at DP 45, 49, and 49, respectively; and highest detectable DP of 80, 72, and 76, respectively. The su2 amylopectin showed a higher percentage of chains with DP 6–12 (22.2%) than normal (15.0%) and waxy (14.6%) amylopectins. The absolute amylose content of normal, waxy, and su2 starches was 18.8, 0.0, and 27.3%, respectively. Gel‐permeation profiles of su2 corn starch displayed a considerable amount of intermediate components. The su2 corn starch displayed lower gelatinization temperature, enthalpy change, and viscosity; a significantly higher enthalpy change for melting of amylose‐lipid complex; and lower melting temperature and enthalpy change for retrograded starch than did normal and waxy corn starches. The initial rate of hydrolysis (3 hr) of the corn starches followed the order su2 > waxy > normal corn. Waxy and su2 starches were hydrolyzed to the same extent, which was higher than normal starch after a 72‐hr hydrolysis period.     

Functional properties and enzymatic digestibility of cationic and cross-linked cationic ae, wx, and normal maize starch.

The functional properties and enzymatic digestibility of cationic and cross-linked cationic ae, wx, and normal maize starches were studied. Cationization reduced the endothermic transition temperatures (T(o), T(p), and T(c)), however, it increased peak viscosity, swelling power, solubility, clarity, and digestibility of all the starches compared to the corresponding native starch. After cationization, the enthalpy of waxy and normal starches was little changed but ae starch showed a decrease. For gel texture, cationization increased the hardness, adhesiveness, and springiness of all the starches, except for the hardness and adhesiveness of normal starch which showed a decrease, and the springiness of waxy starch did not show much change compared to the corresponding control starch. Cross-linking of cationic starch increased the endothermic transition temperatures, as well as peak viscosity. However, it reduced the swelling power and solubility, clarity, and enzymatic digestibility of all the cationic starches.     

Rheological Properties of Starch Gels from Wheat Mutants with Reduced Amylose Content

Wheat lines with reduced amylose content were recently produced by single and double mutation from a low‐amylose line, Kanto 107. They are appropriate for clarifying the influence of amylose content on starch gel properties because of their similar genetic background. When measured using the concanavalin A method (ConA), the total amylose content of isolated starches from Kanto 107 and three mutants (K107Afpp4, Tanikei A6599‐4, K107Wx2) was 24.8, 18.5, 7.1, and 1.7%, respectively. Results of differential scanning calorimetry (DSC) showed that the difference in amylose content strongly affected gelatinization conclusion temperature and enthalpy. We prepared 30 and 40% starch gels and measured their dynamic shear viscoelasticity using a rheometer with parallel plate geometry. Compressive and creep‐recovery tests were conducted under uniaxial compression. The storage shear modulus correlated highly with the amylose content of starch in 30 and 40% starch gels. The creep‐recovery test showed a clear distinction in creep curves among starch samples. When the compressive force required for 50, 80, and 95% strains was compared, starch gels with lower amylose content showed lower compressive force at 50% strain. Waxy starch gel (K107Wx2) showed higher compressive force at strain >80% than other samples due to its sticky property.     

Influence of Amylose Content on Properties of Wheat Starch and Breadmaking Quality of Starch and Gluten Blends

The effects of amylose content on thermal properties of starches, dough rheology, and bread staling were investigated using starch of waxy and regular wheat genotypes. As the amylose content of starch blends decreased from 24 to 0%, the gelatinization enthalpy increased from 10.5 to 15.3 J/g and retrogradation enthalpy after 96 hr of storage at 4°C decreased from 2.2 to 0 J/g. Mixograph water absorption of starch and gluten blends increased as the amylose content decreased. Generally, lower rheofermentometer dough height, higher gas production, and a lower gas retention coefficient were observed in starch and gluten blends with 12 or 18% amylose content compared with the regular starch and gluten blend. Bread baked from starch and gluten blends exhibited a more porous crumb structure with increased loaf volume as amylose content in the starch decreased. Bread from starch and gluten blends with amylose content of 19.2–21.6% exhibited similar crumb structure to that of bread with regular wheat starch which contained 24% amylose. Crumb moisture content was similar at 5 hr after baking but higher in bread with waxy starch than in bread without waxy starch after seven days of storage at 4°C. Bread with 10% waxy wheat starch exhibited lower crumb hardness values compared with bread without waxy wheat starch. Higher retrogradation enthalpy values were observed in breads containing waxy wheat starch (4.56 J/g at 18% amylose and 5.43 J/g at 12% amylose) compared with breads containing regular wheat starch (3.82 J/g at 24% amylose).     

Evaluation of Starch Properties of Wheats Used for Chinese Yellow-Alkaline Noodles in Japan

The objective of the present research was to assess the functional properties of the starches isolated from Australian prime hard wheat (PH) and hard red winter wheat (HRW) in the United States. These wheats are favorably used in Japan for the production of Chinese yellow-alkaline noodles (YAN). Starches isolated from PH showed higher amylose content than those of noodle wheat but lower than bread wheat. Analysis of swelling power showed that PH starch had lower values than noodle wheat starches but higher values than bread wheat starches. By contrast, HRW starch showed relatively higher amylose content and lower swelling power. There were large differences in the starch pasting properties between PH and HRW. High-performance size-exclusion chromatography studies on the components leached from the starch (80°C, 20 min) showed that PH starch had a somewhat characteristic leaching profile. Its peak ratio of high molecular weight region to low molecular weight region was greater than that of HRW starch. PH starch also characterized by having lower endothermal enthalpy (ΔH) in amylose-lipid transition. The eating quality assessment for YAN revealed that PH had more elastic texture than HRW. Additional reconstitution studies showed that these quality differences could be attributable to its starch properties.     

Influence of genotype and processing on the in vitro rate of starch hydrolysis and resistant starch formation in peas (Pisum sativum L.).

The formation of resistant starch (RS) and the rate of starch hydrolysis were evaluated in vitro in a wild type of green-seeded pea genotype RRRbRb BC3 (33-Am) with 32.7% amylose content and in two mutants RRrbrb BC3 (23-Am) and rrRbRb BC3 (65-Am) with amylose contents of 23.3 and 65.1%, respectively. Pea samples were intact or homogenized and subjected either to autoclaving or to boiling at atmospheric pressure. The amount of RS (total starch basis) varied from 6.2 to 12.9% in the 23-Am products and from 31.2 to 33.4% in the 65-Am products. The RS level of the 33-Am product with a regular amylose content was 11.0%. Both the 23-Am and the 65-Am products were abundant sources of dietary fiber (39 and 34%, dry matter basis, respectively) versus 23% in the regular pea product. The amylose/amylopectin ratio was an important determinant of the rate of starch hydrolysis. The hydrolysis indices (HI) and predicted glycemic indices were lowest in the 65-Am peas (HI range = 42-59) as compared to the 23-Am peas (HI range = 53-84). It is concluded that the pea genotypes covered a wide range in starch availability, which is likely to affect nutritional parameters such as glycemic responses and colonic delivery of starch.     

Genetic Diversity in Physical Properties of Starch from a World Collection of Amaranthus

Physical and functional properties of starches isolated from 93 noncultivated genotypes of nine Amaranthus species from a world germ plasm collection and an additional 31 cultivated Amaranthus genotypes obtained from China were tested. A wide variation was found in the properties tested among the Amaranthus species and among genotypes within the same species. When comparing starches from cultivated and noncultivated genotypes, it was generally found that amylose was lower; starch pasting profiles were more consistent with higher peak viscosity, lower breakdown, and lower setback; the gelatinization temperature was lower; and energy of enthalpy was higher. Under cool storage, the hardness of cultivated starch pastes was lower and the adhesiveness was higher. As expected, amylose content was a primary factor affecting the physical and functional properties of Amaranthus starch. Compared with reference maize, rice, and wheat starches, Amaranthus starch tended to have lower hot paste viscosity and lower cool paste viscosity; and higher gelatinization temperatures and higher energy of enthalpy. Furthermore, Amaranthus starch pastes showed less change of gel hardness and adhesiveness after cold storage. The environmental effect on the different properties of starch varied among Amaranthus species. It is suggested that Amaranthus starches can be developed for a wide range of food uses.     

Paste Properties of Modified Starches from Partial Waxy Wheats

Properties of modified starches from partial waxy wheats have not been examined. Protease digestion of cracked kernels of three hard winter wheats varying in amylose content led to 82–85% recovery of starch, whereas kneading of the flour-water doughs gave 75–83% recovery. All starches had a protein content of <0.3% and ash content of <0.01%. Granule size distributions showed that starch from Ike kernels contained 86% A-type granules with a peak size of ≈18μm, and Karl-92 starch contained 77% A-type granules with a peak size of ≈16μm. The A-type granules (82%) from Rio Blanco starch were intermediate in size. The amylose content of Karl-92 starch, determined by concanavalin-A precipitation of amylpectin, was 28%, which was 17% higher than that of Ike starch (23%). The amylose content of Rio Blanco starch was 26%. The lipid content of Karl-92 starch, determined as fatty acid methyl esters, also was 18% higher than that of Ike starch (601 vs. 488 mg/100 g of starch, respectively). Wheat starches were modified with hydroxypropyl (HP) groups to low (1.5–2.5%) and medium (≈4.0%) levels, and the HP starches were cross-linked with phosphoryl chloride at levels of 0.003–0.075%. Pasting curves (amylograms) showed that Ike starch substituted with a low level of HP and optimally cross-linked with 0.025% phosphoryl chloride (starch basis) had a greater paste consistency than low HP cross-linked Karl-92, and Rio Blanco starches. At 4% HP and optimum cross-linking (0.003% phosphoryl chloride), the paste consistencies of the modified starches were nearly the same. The clarity of unmodified Ike starch paste was higher than that of Karl-92 or Rio Blanco starch pastes, and the clarity of all three pastes decreased as cross-linking was increased. Unmodified Ike starch formed a stronger gel than unmodified Karl-92 and Rio Blanco starches, but gel properties largely converged as the starches were modified.     

Properties and Structures of Flours and Starches from Whole,Broken, and Yellowed Rice Kernels in a Model Study

The objective of this study was to compare the structure and properties of flours and starches from whole, broken, and yellowed rice kernels that were broken or discolored in the laboratory. Physicochemical properties including pasting, gelling, thermal properties, and X‐ray diffraction patterns were determined. Structure was elucidated using high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography with pulsed amperometric detection (HPAEC‐PAD). The yellowed rice kernels contained a slightly higher protein content and produced a significantly lower starch yield than did the whole or broken rice kernels. Flour from the yellowed rice kernels had a significantly higher pasting temperature, higher Brabender viscosities, increased damaged starch content, reduced amylose content, and increased gelatinization temperature and enthalpy compared with flours from the whole or the broken rice kernels. However, all starches showed similar pasting, gelling, thermal properties, and X‐ray diffraction patterns, and no structural differences could be detected among different starches by HPSEC and HPAEC‐PAD. α‐Amylase may be responsible for the decreased amylopectin fraction, decreased apparent amylose content, and increased amounts of low molecular weight saccharides in the yellowed rice flour. The increased amount of reducing sugars from starch hydrolysis promoted the interaction between starch and protein. The alkaline‐soluble fraction during starch isolation is presumed to contribute to the difference in pasting, gelling, and thermal properties among whole, broken, and yellowed rice flours.     

Characteristics of taro (Colocasia esculenta) starches planted in different seasons and their relations to the molecular structure of starch

Physico-chemical properties and molecular structure of starches from three cultivars (Dog hoof, Mein, and KS01) of taro tubers planted in summer, winter, and spring were investigated. The effects of the planting season on the physico-chemical properties and the molecular structure of starch were determined, and the relations between the physico-chemical properties and the molecular structure of starch are discussed. Results indicate that taro starches from tubers planted in summer had the largest granule size, a low uniformity of gelatinization, and a high tendency to swell and collapse when heated in water. Taro starch planted in summer also showed an elasticity during gelatinization that was higher than that of starches planted in the other seasons. In addition to the planting season and the variety, rheological and pasting properties of taro starches studied are influenced not only by the amylose content but also by the chain-length distribution of amylopectin, whereas swelling power and solubility only depend on the amylose content of starch. Taro starch with relatively high amylose content, high short-to-long-chain ratio, and long average chain length of long-chain fraction of amylopectin displayed high elasticity and strong gel during heating.