Effect of annealing on the semicrystalline structure of normal and waxy corn starches

The influence of amylose and amylopectin on structural reorganization occurred during annealing was studied for normal and waxy corn starches. Annealing caused an increase in crystallinity in the waxy corn starch, whereas the number of pores on the granule surface, observed by SEM, increased especially for normal corn starch. Amylose and amylopectin chains of the annealed normal corn starch were degraded to greater extension during enzymatic hydrolysis than those of the native starch. On contrary, the annealing caused a protective effect on waxy corn starch amylopectin toward the enzymatic reaction suggesting that this treatment promoted a better interaction between amylopectin chains of waxy corn starch. The amylose molecules of normal corn starch may have impaired the mobility of amylopectin molecules and restricted the reorganization of the crystalline structure during the annealing. The major increase in pores number on the granule surface of annealed normal corn starch, resulted of the endogenous amylase action during annealing, could facilitate the exogenous enzymes’ role in the degradation of the starch granules’ amorphous area.     

Insights into the relations between the molecular structures and physicochemical properties of normal and waxy wheat B-starch after repeated and continuous annealing

The effect of repeated annealing treatment (RANN) and continuous annealing treatment (CANN) on the structure, physicochemical properties and digestibility of wheat B-starch were studied. Annealing degraded the starch molecules, disrupted amylopectin and amylose structures, and decreased the molecular weight and the long chain of amylopectin. Meanwhile, the double helix structure and the crystalline and amorphous region were broken, the starch and water molecules were rearranged after RANN and CANN. As a result, annealing increased the crystallinity, gelatinisation temperature, resistant starch and slowly digestible starch content, while decreased the solubility, swelling power and pasting viscosity. The different changes of structural and physicochemical properties for normal and waxy B-starch upon annealing treatment were because of the different amylose contents and amylopectin chain mobility. The RANN exhibited greater advantages than CANN in the modification of the structural, physicochemical, and digestible properties of normal B-starch; while CANN significantly affected properties of waxy B-starch.     

Effects of annealing on the physicochemical properties and enzymatic susceptibility of rice starches with different amylose contents

This study investigated the effects of annealing (ANN) on the properties of rice starches with high, medium and low-amylose contents. The starches were heated with excess water at 45 °C, 50 °C and 55 °C for 16 h. The swelling power, solubility, pasting properties, enzymatic susceptibility, morphology and X-ray crystallinity of the starches were evaluated. Annealing reduced the swelling power and solubility of the starches. ANN at 55 °C increased the pasting temperature and decreased the peak viscosity of the high-amylose rice starch. However, annealing decreased the peak viscosity of the low-amylose starch. The annealed rice starches presented a lower final viscosity and setback than did the native starches, with the exception of the low-amylose starch, which showed an increase in setback. Annealing increased the starches’ susceptibilities to α-amylase and promoted a reduction in their relative crystallinity.     

Effect of annealing on the structure and physicochemical properties of barley starches of varying amylose content

Starch from normal (CDC McGwire, SR 93102), waxy (CDC Fibar, HB 364), and High amylose (SB 94897, SB 94893) hull-less barley cultivars was isolated and its structure, morphology, and properties were studied before and after one-step annealing (50 °C for 72 h at a moisture content of 75%). The amylopectin structure of all starches was nearly identical. The X-ray pattern of CDC Fibar, HB 364, and CDC McGwire starches was of the ‘A’-type. Whereas, SR 93102, SB 94897, and SB 94893 starches exhibited a mixed ‘A + B’-type pattern. The relative crystallinity (RC), swelling factor (SF), amylose leaching (AML), gelatinization temperature range (GTR), enthalpy of gelatinization (ΔH), amylose–lipid complex melting temperature (Tp_CX) and the enthalpy of melting of the amylose–lipid complex (ΔH_CX) ranged from, 37.0% to 44.3%, 41.0–54.2% (at 90 °C), 4.0–31.0% (at 90 °C), 11.4–22.5 °C, 6.0–13.0 J/g, 84.9–89.1 °C and 0.4–1.8 J/g, respectively. The RC of CDC Fibar, HB 364, SR 93102 and CDC McGwire starches increased on annealing. Whereas, it remained unchanged in SB 94897 and SB 94893 starches. The ‘A’-type X-ray pattern of CDC Fibar, HB 364, and CDC McGwire starches remained unchanged on annealing. However, the ‘A + B’-type X-ray pattern of SR 93102, SB 94897 and SB 94893 starches resembled more closely the ‘A’-type pattern on annealing. In all starches, the X-ray intensity of the V-amylose–lipid complex peak increased on annealing. Annealing increased the gelatinization transition temperatures and decreased the GTR in all starches. The ΔH of SB 94893 starch increased on annealing, whereas it remained unchanged in the other starches. Tp_CX of SR 93102 and SB 94897 remained unchanged on annealing, whereas Tp_CX of CDC McGwire increased slightly. ΔH_CX of native and annealed CDC McGwire, SR 93102 and SB 94897 were similar. Tp_CX and ΔH_CX were not detectable in annealed SB 94893 starch. In all starches, SF decreased on annealing. Annealing decreased AML in SR 93102, SB 94897 and SB 94893 starches in the temperature range of 50–90 °C, but increased AML in HB 364 and CDC McGwire starches at higher temperatures. The effect of annealing on acid hydrolysis was marginal.     

板栗淀粉结构和功能特性研究进展

淀粉是板栗的主要成分,约占干物质的38-80%。近年来,关于谷物和块茎类淀粉的结构及其对功能性质的影响的研究已取得实质性进展,但对板栗淀粉的研究还不够深入。本文对板栗淀粉的提取方法、结构与功能性质进行了综述,重点阐述了板栗淀粉微观形貌、化学组成、分子结构、膨胀度和溶解度、热性质、糊化性质、淀粉糊的透明度、冻融稳定性、凝胶质构及体外酶消化性。最后,展望了板栗淀粉未来的研究方向。     

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

Starches from normal rice (21.72% amylose), waxy rice (1.64% amylose), normal corn (25.19% amylose), waxy corn (2.06% amylose), normal potato (28.97% amylose) and waxy potato (3.92% amylose) were heat-treated at 100 °C for 16 h at a moisture content of 25%. The effect of heat-moisture treatment (HMT) on morphology, structure, and physicochemical properties of those starches was investigated. The HMT did not change the size, shape, and surface characteristics of corn and potato starch granules, while surface change/partial gelatinization was found on the granules of rice starches. The X-ray diffraction pattern of normal and waxy potato starches was shifted from B- to C-type by HMT. The crystallinity of the starch samples, except waxy potato starch decreased on HMT. The viscosity profiles changed significantly with HMT. The treated starches, except the waxy potato starch, had higher pasting temperature and lower viscosity. The differences in viscosity values before and after HMT were more pronounced in normal starches than in waxy starches, whereas changes in the pasting temperature showed the reverse (waxy > normal). Shifts of the gelatinization temperature to higher values and gelatinization enthalpy to lower values as well as biphasic endotherms were found in treated starches. HMT increased enzyme digestibility of treated starches (except waxy corn starch); i.e., rapidly and slowly digestible starches increased, but resistant starch decreased. Although there was no absolute consistency on the data obtained from the three pairs of waxy and normal starches, in most cases the effects of HMT on normal starches were more pronounced than the corresponding waxy starches.     

Structural modification of waxy,regular, and high‐amylose maize and hulless barley starches on partial acid hydrolysis and their impact on physicochemical properties and chemical modification

Waxy (WX), regular (RA), and high‐amylose (HA) maize and hulless barley (HB) starches were subjected to partial acid hydrolysis with 1.0 and 2.2 N HCl for 30–240 min. In both starches, the extent of hydrolysis with 1.0 N HCl followed the order: HA>WX>RA, whereas with 2.2 N HCl, the order was: HA>WX>RA (maize) and WX>HA>RA (HB), respectively. The relative crystallinity increased (HA>WX>RA) and the X‐ray pattern remained unchanged, whereas the swelling factor decreased (WX>RA>HA in maize and WX>HA>RA in HB) at both acid concentrations. Starches hydrolyzed with 1.0 N HCl exhibited increased gelatinization temperatures (WX>RA>HA in maize, WX>HA ∼ RA in HB), a narrower gelatinization temperature range (WX>RA>HA in maize, WX>RA ∼ HA in HB) and a decreased gelatinization enthalpy (WX>HA>RA in maize and HB). Acid hydrolysis increased the accessibility of the phosphorylating reagent into the amorphous regions. The extent of phosphorylation was more pronounced (maize>HB) in starches hydrolyzed with 1.0 N HCl for 60–90 min. The bound phosphorus content (BPC) followed the order: HA>WX>RA in maize and HB starches hydrolyzed with 1.0 N HCl for 240 min. In both starches, the extent of cationization was not influenced either by acid concentration or hydrolysis time. In general, acid hydrolysis significantly affected the reactivity of starch towards phosphorylation, where the optimum hydrolysis condition differed with starch source. The results would benefit the starch industry, since the amount of the phosphorylating reagent required for increasing thermal stability and/or freeze‐thaw stability could be decreased substantially, if starches are subjected to partial acid hydrolysis prior to derivatization.     

Study on physicochemical characteristics of waxy potato starch in comparison with other waxy starches

The physicochemical properties of wx potato, wx corn, and wx rice starches were examined and compared. wx potato starch displayed the B‐type XRD pattern, whereas wx rice and wx corn displayed the A‐type. Shapes of wx potato starch were oval or slightly round, wx corn and wx rice starch granules were polygonal. AM contents of the three starches were between 1.0 and 1.5%. Rapid viscosity analyzer data showed initial pasting temperatures of wx potato, wx corn, and wx rice starches as 69.6, 75.4, and 76.8°C, respectively, peak viscosity, breakdown, and setback of wx potato starch were 2114, 1084, and 4 mPa s. Using DSC, onset temperature of gelatinization of wx potato starch was 5.5–7.2°C higher than those of wx rice and wx corn starches. The thermal enthalpies of the starches studied in our laboratory were in the range of 0.2268–1.9900 J/g with decreasing order of wx potato > wx corn > wx rice starch.     

Structure of faba bean, black bean and pinto bean starches at different levels of granule organization and their physicochemical properties

The structure and physicochemical properties of pulse starches isolated from different cultivars of faba bean (FB), black bean (BB) and pinto bean (PB) were examined. FB starches exhibited numerous cracked granules, whereas the surface of PB and BB starches showed no evidence of cracks or indentations. Apparent amylose, phosphorus and bound lipid contents ranged from 25.8 to 33.6%, 0.004 to 0.009% and 0.13 to 0.15%, respectively. Variations in the above parameters among cultivars of FB and BB were marginal, but significant (P < 0.05) among cultivars of PB. All starches exhibited a ‘C’ type X-ray pattern. The amount of B-type unit cells ranged from 20.6 to 25.0% (FB), 15.4 to 17.7% (BB) and 7.9 to 17.3% (PB). Relative crystallinity ranged from 20.3 to 21.9% (FB), 20.4 to 21.3% (BB) and 21.3 to 23.1% (PB). Molecular order near the granule surface followed the order: BB ~ PB > FB. Variations in molecular order among cultivars of FB, BB and PB were marginal. Differences in amylopectin chain length distribution among FB, BB and PB starches and among cultivars were marginal. The extent of interaction of amylopectin double helical associations within the crystalline lamella followed the order: BB ~ PB > FB. Amylose leaching (AML) in the temperature range 60–90 °C, gelatinization temperatures and enthalpy of gelatinization followed the order: FB > BB ~ PB, FB > PB > BB, BB ~ PB > FB and BB ~ PB > FB, respectively. Variations in AML among cultivars were marginal in FB, but significant (P < 0.05) in BB and PB starches. Swelling factor (SF) in the temperature range 60 to 85 °C and at 90 °C followed the order: FB > BB ~ PB and BB ~ PB > FB, respectively. Differences in SF among cultivars of FB and BB starches were more significant (P < 0.05) at temperatures below 80 °C, whereas, in PB starches, differences among cultivars were more significant (P < 0.05) at temperatures above 80 °C. Variations in peak viscosity, viscosity breakdown and set-back were marginal among FB cultivars, but were significant (P < 0.05) among BB and PB (PB > BB) cultivars. FB starches were hydrolyzed by 2.2 N HCl at a faster rate than BB and PB starches (BB > PB). The amounts of rapidly digestible starch (RDS), slowly digestible starch (SDS), resistant starch (RS), hydrolysis index (HI) and expected glycemic index (eGI) followed the order: FB > BB ~ PB, FB > BB ~ PB, BB ~ PB > FB, FB > BB > PB and FB > BB > PB, respectively. Variations in RDS, SDS, RS, HI and eGI among cultivars followed the order: PB > BB > FB. The in vitro digestibility studies showed that PB and BB starches may be more effective than FB starches in controlling blood glucose levels.     

Studies on the granular structure of resistant starches (type 4) from normal,high amylose and waxy corn starch citrates

Granular and crystalline structure of starch citrates from normal, high amylose and waxy corn starch were characterized using scanning electron microscopy (SEM), optical microscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) in this study. SEM showed that citric acid treatment induced changes in the morphology of starch granules. The granule structure of starch citrates was not collapsed or destroyed even after heating. Normal and high amylose corn starch citrates maintained birefringence but lost it upon heating at 100 °C for 30 min. However, waxy corn starch citrate showed no birefringence, even before heating. Starch citrates showed different X-ray diffraction patterns before and after heating. A new peak at 1724 cm⁻¹ (ester bond) was observed in FT-IR for all starch citrates before and after heating, indicating starch citrates were heat-stable. After the deconvolution of spectra, the intensity ratio of 1016 cm⁻¹/1045 cm⁻¹ was used to calculate the ratio of amorphous to crystalline phase in the starch citrates. The ratio of 1016 cm⁻¹/1045 cm⁻¹ increased with an increase in the degree of substitution.     

Impact of thermostable amylases during bread making on wheat bread crumb structure and texture

Thermostable amylases [Bacillus subtilis α-amylase (BSuA) and B. stearothermophilus maltogenic amylase (BStA)] with different modes of action and impacts on firming properties were added during straight-dough bread making. BSuA continuously degraded the starch fraction during bread making. Its action resulted in larger gas cells than in control bread, but did not change initial firmness. In contrast to BSuA, BStA mainly degraded starch at the end of the baking phase and during bread cooling, which caused little if any impact on bread crumb texture. However, it led to higher initial firmness readings than for the control breads. Neither BSuA nor BStA were inactivated during bread making. The results evidence that starch properties have a large impact on bread crumb structure and initial firmness and are highly influenced by the mode of action of the enzyme.     

Gel texture and rheological properties of normal amylose and waxy potato starch blends with rice starches differing in amylose content

This study characterised the textural and rheological behaviour of blends of rice (waxy, low- and high-amylose) and potato (waxy and normal) starch. Blends of potato starch with rice starch in the ratios of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 were tested. Addition of rice starch (except high-amylose rice starch) greatly increased the swelling of rice–potato starch mixtures. Addition of rice starch decreased gel firmness for most starch mixtures and increased gel adhesiveness for blends containing waxy potato starch. For rheological measurements, storage modulus was much higher than loss modulus of blends, indicating solid-like behaviour. Starch blends with 20%/40% proportion of rice starch showed a greater thickening effect, whereas with further increase in rice starch proportion, a pseudoplastic, shear-thinning behaviour was observed. This study may provide a basis to develop blends of potato and rice starch for potato noodle production without use of chemical additives.     

Preparation and physicochemical properties of modified jackfruit starches

Modifications of jackfruit starch, extracted from the cotyledons of Artocarpus heterophyllus Lam. (Thong Prasert cultivar), were carried out to obtain a pregelatinized starch, three (m-, n- and i-) carboxymethyl starches, a hydroxypropyl starch and a phosphate cross-linked starch. Physicochemical properties of native and modified jackfruit starches were comparatively investigated. Pregelatinized, hydroxypropyl, and cross-linked starches were insoluble or partially soluble in water at room temperature, while carboxymethyl starches were soluble with good overall water uptake. Scanning electron microscopic images revealed that granules of most modified jackfruit starches retained the native appearance and crystal structure, with the exception of pregelatinized starch and two (n- and i-) carboxymethyl starches, which showed significant breakage of granules. X-ray diffraction patterns corroborated to suggest the loss of crystallinity in these modified starches. Thermal analysis showed a significant decrease in the gelatinization temperature of hydroxypropyl starch with no change in enthalpy, while higher gelatinization temperature and less enthalpic value were observed for pregelatinized starch. Pregelatinized and hydroxypropyl starches showed temperature-dependent improvement on swelling and solubility, while cross-linked starch exhibited less solubility. Aqueous solution of m-carboxymethyl starch yielded the highest apparent viscosity with improved heating-cooling stability.     

The bread baking quality of six wheat starches differing in composition and physical properties

Starch was isolated from six types of wheat and separated into large A-granule and small B-granule fractions which exhibited a suitable range of properties. Respective amylose contents were 28.6–31.0% and 25.1–31.5%, lysophospholipids 707–1014mg 100 g^?1, and 1058–1398 mg 100 g^?1, and gelatinisation temperatures (GT) by differential scanning calorimetry (DSC) 58.4–62.7°C and 60.5–64.5°C. The A- and B-granule fractions were remixed in various proportions and reconstituted with freeze-dried gluten and freeze-dried water-solubles from flour to test the effects of changes in the properties of the total starch, A-granule or B-granule fractions, and the effects of various proportions of B-granules on the quality of bread. The specific volumes of the loaves were not affected by starch amylose or lipid content, but were significantly correlated with either the GT of the total starches or their A-granules. The optimum proportion of B-granules was 25–35% by weight, but their GT had no effect on loaf specific volume. Staling changes were quantified from crumb compressibility measurements and the enthalpy of the endotherm for gelatinisation of retrograded amylopectin in stored breadcrumb, measured by DSC. Initial and limiting moduli of crumb firmness were correlated with loaf specific volume and starch GT, but rate and time constants calculated from the Avrami equation were independent. Rate and time constants and limiting enthalpy values calculated from the DSC results were independent of all other measured parameters.     

Relationships between amylopectin internal molecular structure and physicochemical properties of starch

BackgroundStructure-property relationships of starch components remain a subject of research interest. In recent years, there has been increasing evidence revealing the importance of amylopectin internal structure in determining physicochemical properties of starch. The part between the sole reducing end and out branches of amylopectin forms the internal part of the molecule. It contributes to the formation of the amorphous lamellae of the granules.Scope and approachThis mini-review focuses on the impact of amylopectin internal molecular structure on different physicochemical properties of starch. The properties include gelatinization, swelling power, amylose leaching, pasting, retrogradation, and digestibility of starch. The statistical approach to analyze the structure-property relationships of starch is also discussed. Related nomenclatures are described.Key findings and conclusionsAmylopectin with a longer internal chain length tends to give more ordered packing of double helices in the granules with a higher thermal stability. A longer internal chain length of amylopectin also contributes to the formation of recrystallized amylopectin with a more ordered structure and higher thermal stability. The results summarised in this mini-review clearly show that the molecular structure of amylopectin internal part should be considered in order to better understand the complex structure-property relationships of starch components.     

Amylose content,molecular structure,physicochemical properties and in vitro digestibility of starches from different mung bean (Vigna radiata L.) cultivars

Physicochemical and in vitro digestibility characteristics of starches isolated from six cultivars of mung bean (Vigna radiata L.) were studied. Significant differences (p < 0.05) were observed between the cultivars with respect to amylose content (29.9–33.6%), relative crystallinity (29.0 to 31.7%), particle diameter (16.2–17.1 µm) and molecular weight of amylopectin (260–289 × 10⁶ g/mol). The scanning electron micrographs revealed the presence of large oval to small round shape granules with average particle diameter of 16.2–17.1 µm. The X‐ray diffraction pattern was of the C‐type. The enthalpies of gelatinization and retrogradation were 8.9–10.3 and 4.6–6.3 J/g, respectively. The amounts of slowly digesting and resistant starch of mung bean followed the order: PBM‐1 > SML‐32 > ML‐613 > SML‐134 > ML‐267 > ML‐5 and ML‐5 > ML‐267 > SML‐134 > ML‐613 > SML‐32 > PBM‐1, respectively. The six starches exhibited significant (p < 0.05) differences in their pasting parameters. Correlation analysis showed that amylose content, granule diameter and relative crystallinity values were important in determining thermal, pasting and in vitro digestibility of starches.     

Gelatinisation properties of native and annealed potato starches

The relationship between the gelatinisation parameters of native and annealed starches extracted from ten different potato varieties grown at the same site at the same time was studied. The objective was to identify how native gelatinisation temperatures and enthalpies impacted on annealed starch gelatinisation parameters. Prior to ANN, the initial onset (T_o), peak (T_p) and conclusion (T_c) gelatinisation temperatures ranged from 58.71 to 62.45, 62.52 to 66.05 and 68.67 to 72.27°C, respectively, which increased to 66.15 to 69.12, 70.22 to 72.30 and 76.21 to 77.44°C, respectively, post ANN. Overall, the greater the initial gelatinisation temperatures the smaller the increment (ΔGT) post ANN. Comparable enthalpy values pre‐ and post‐ANN were 15.13 to 18.37 and 15.76 to 18.37 J/g, respectively. These data indicate that the more ‘perfect’ the crystallites were before ANN the less they could be enhanced by the ANN process and that against a constant background of α‐glucan structure, the pattern (rate) of starch deposition might be the primary differentiator of starch architecture across the varieties.     

Effect of acid hydrolysis in the presence of anhydrous alcohols on the structure,thermal and pasting properties of normal,waxy and high‐amylose maize starches

Maize starches with different amylose contents (0%, 23% and 55%) were treated in anhydrous methanol, ethanol, 2‐propanol, 1‐butanol with 0.36% HCl at 25 °C for 5 days. Results showed that the extent of change in physicochemical properties increased from methanol to butanol. Treated waxy maize starch showed higher than 65% solubility at above 75 °C. The diffraction peak at 2θ = 5.3° of amylomaize V starch disappeared after treatment in ethanol, 2‐propanol and 1‐butanol. Acid–alcohol treatment decreased the gelatinisation temperature of normal (from 64.5 to 61.9 °C) and waxy maize (from 68.1 to 61.1 °C) starches, while it increased that of amylomaize V (from 68.7 to 72.3 °C) starch. The extent of the decrease in the pasting viscosity followed the following order: amylomaize V < normal maize < waxy maize. This study indicated that acid–alcohol treatment degraded preferentially the amorphous regions and the different changes depended on the crystal structure and amylose content of starch.     

Effects of electron‐beam irradiation on physicochemical properties of starches separated from stored wheat

Effects of electron‐beam irradiation (0, 1.0, 2.7, and 4.4 kGy) on physicochemical properties, MW distribution as well as microstructure of starches separated from electron‐beam irradiated and stored wheats were investigated by differential scanning calorimeter (DSC), SEM, and static multi‐angle laser light scattering (MALLS). The profiles of starch viscosity illustrated that peak, hot paste, cold paste, and setback were considerably decreased with increasing irradiation dose. The DSC pattern indicated that the electron‐beam irradiation caused a slight decrease in gelatinization temperature. SEM results showed that on the surfaces of a few starch granules fissures appeared and that they become rough when the irradiation doses reached 4.4 kGy. Damaged starch (DS) contents analysis suggested that the DS increased from 5.33 to 7.38% as the dose increased from 0 (control) to 4.4 kGy. HPSEC measurement showed that the starch molecule were gradually degraded due to the electron‐beam irradiation treatment, and the molar mass of wheat starches decreased by one order of magnitude when the irradiation doses reached 4.4 kGy.