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.     

桂淮系列淮山淀粉结构研究

选育产量高、淀粉含量高、适应性广的淮山新品种对保障我国粮食安全和促进农民增收具有重大意义,而淮山淀粉的结构与性质可以影响淮山的口感以及淀粉加工特性。通过测定桂淮5号、桂淮7号、桂淮8号、紫淮山4个淮山品种的淀粉的成分、淀粉颗粒的粒径与外观,利用偏光十字、红外光谱、核磁共振等分析淀粉颗粒的结晶特性,研究不同品种间淀粉结构与性质。结果表明:桂淮8号较其余3个品种淮山淀粉具有更高的蛋白质和直链淀粉含量;X-射线衍射及13C谱结果分析显示桂淮7号和桂淮8号为B型淀粉。     

香蒲绒纤维对机油的吸附性能研究

利用香蒲绒纤维作吸油材料对含油废水中的机油进行处理,阐述了纤维的吸油机理。研究了该纤维对纯机油以及对含水机油的吸附能力,并研究了纤维的重复利用性能。结果表明,香蒲绒纤维对机油有很好的吸附能力,1g纤维能吸附13～20g的纯机油,能吸附含水机油12～18g;吸油后纤维通过挤压即可重复利用,且经过5次重复试验后1g香蒲绒纤维仍能吸附5～10g的含水机油。     

Perspectives on the history of research on starch

Starch has been used over several millennia for a number of different applications. However, research on understanding this substance only spans about three centuries starting with Leeuwenhoek who observed it in 1716. This story of discovery of the molecular structure and architectural makeup of starch is chronicled in a series of six essays of which this is the third with a focus on contemporary terminologies used in the 19th and early 20th centuries and its impact on advances in starch. Following the discovery of diastase, researchers focused on understanding the action of diastase on “transforming” starch into sugar. Besides maltose, they found that the products consisted of a range of dextrins with different abilities to complex with iodine. However, the nomenclature of the products that were obtained under a myriad of experimental conditions gave rise to confusions and misinterpretations, which transpired for over 30 years. Researchers also attempted to understand starch structure through systematic analyses of the different stages of starch breakdown. A new era of confusion in both nomenclature and structural interpretation started in the early 20th century with the discovery of cyclodextrins that were obtained from starch using the microorganism B. macerans. This gave rise to the school of “the low molecular elementary unit hypothesis” for starch structure, which lasted for about 25 years.

     

Impact of annealing on the molecular structure and physicochemical properties of normal,waxy and high amylose bread wheat starches

Starch from normal (CDC teal), high amylose (line 11132) and waxy (99 WAX 27) bread wheat cultivars was isolated and its morphology, composition, structure and properties were studied before and after annealing. Granule diameters, total phosphorus, total amylose, lipid complexed amylose chains, crystallinity, gelatinization temperature range, gelatinization enthalpy, swelling factor (at 90 °C), and amylose leaching (at 90 °C), in the above starches ranged from 2–38 μm, 0.007–0.058%, 26.9–32.3%, 13.4–18.7%, 28.6–42.8%, 12.7–14.3 °C, 11.3–13.3 J/g, 27.6–72.2 and 22.2–26.2%, respectively. Peak viscosity, thermal stability, set-back and susceptibility towards acid hydrolysis followed the order: 99WAX27 > CDC teal > 11132, 11132 > CDC teal > 99WAX27, CDC teal > 99 WAX 27 > 11132, and 99WAX27 > 11132 > CDC teal, respectively. Susceptibility towards α-amylase hydrolysis followed the order: 99 WAX 27 > 11132 > CDC teal (<24 h) and 11132 > CDC teal > 99WAX27 (>24 h). The extent of retrogradation measured by spectroscopy and differential scanning calorimetry followed the order: 11132 > CDC teal > 99WAX27 and 99WAX27 > CDC teal > 11132, respectively. In all starches, concentration of amylose, lipid complexed amylose chains, gelatinization temperature range, swelling factor, amylose leaching, peak viscosity, final viscosity, set-back, light transmission, susceptibility towards α-amylase and acid hydrolysis and the proportion of small (2–8 μm) B-type granules decreased on annealing. Thermal stability and crystallinity increased on annealing. In all starches, gelatinization, enthalpy, retrogradation rate and amylopectin chain length distribution remained unchanged on annealing. Pores and indentations were formed on the granule surfaces of CDC teal and 99WAX27 starches on annealing.     

蒲菜热烫的工艺条件

通过对过氧化物酶的残留酶活、色差、剪切强度和剪切功的分析,研究了热烫时间和贮藏温度对蒲菜的过氧化物酶、色泽和质构的影响.结果表明,在100℃的热烫温度下随着热烫时间的延长,过氧化物酶活降低,而贮藏2 d后酶活的再生量先增大后降低,在热处理时间为1.0-1.5min时达到最大值;热烫时间为4 min时,可基本破坏蒲菜中的过氧化物酶,且蒲菜的质构和色泽较好.     

The structure of starch granules in fried battered products

This work studies the structure of starch granules during different steps in the production of frozen battered squid rings, using image analysis and microscopy techniques. Frozen battered squid was prepared with four different batter formulations including wheat flour, corn flour, salt and leavening agent and subjected to pre-frying, freezing and final frying to obtain an industrial product. A control product for each of the formulations was prepared with no pre-frying and no freezing steps.The control products, regardless of their formulation, showed most starch components occluded into the starch granules, while the final products presented more leaching of starch components out of the granules. The use of corn flour as an ingredient increased the water retention capacity of the batter, resulting in higher area values for starch granules in formulations where this ingredient is used. There were significant differences between some formulations in the size and shape of the large starch granule population, but no significant differences were observed for the small granule population. As regards the preparation steps, short thermal treatments such as pre-frying mainly affected the large starch granules, which are weaker.     

Functional and tableting properties of acetylated and oxidised finger millet (Eleusine coracana) starch

The functional and tableting properties of native (NaFM) and chemically modified (by acetylation, AcFM; and oxidation, OxFM) finger millet starches were investigated. The tablet formation properties of the starches were assessed by Heckel and Kawakita analysis. The swelling power and solubility of the starch increased with increase in temperature with AcFM having the highest swelling power, while OxFM had the highest solubility. X‐ray diffractometry showed that the starches had the characteristic ‘A’ pattern with strong peaks at 3.78, 4.37, 4.87, and 5.17 Å. Chemical modification causes rupture of some starch granules as revealed by the Scanning Electron Micrograph. Chemical modification also leads to improved gelatinisation profile, with reduction in ΔH_gel from 9.64 J/g (NaFM) to 3.88 J/g (AcFM) and 8.76 J/g (OxFM). The bulk density and Hausner's ratio increased after chemical modification of the starch. Chemical modification reduced the mean yield pressure, P_y (Heckel analysis) but increased the deformability P_k (Kawakita analysis) of the starch compacts. Chemical modification also increased the crushing and tensile strength of the starch compacts, but lowered its disintegration time and friability.     

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starch pastes

The effect of rice variety and starch isolation method on the pasting and rheological properties of rice starches was evaluated. One waxy and three non-waxy rice varieties from California with a range of amylose contents of 1.6–26.5% and four methods of isolation were evaluated. A rotational rheometer (RR) was used to measure the pasting and rheological properties of starch dispersions (8% w/w). The RR pasting curves had similar shapes to those from a rapid visco-analyzer (RVA). The four treatments used for isolating starch were a protease, NaOH (0.1% and 0.4%), or sodium dodecyl sulfate (SDS) (1.0%). The NaOH (0.4%) and SDS treatments were found to reduce the peak pasting temperatures of the non-waxy starches as compared with the protease and NaOH (0.1%) treatments. The same trend of the treatments was found with the elastic moduli, low shear viscosities, and yield stresses of the non-waxy starch pastes measured at 65 °C, immediately after pasting. The elastic moduli of the waxy starch pastes appeared to be least affected by method of starch isolation, but the low shear viscosity and yield stress of the protease starch paste was significantly higher than the paste from the other three treatments. Overall, the method of rice starch isolation was found to affect the gelatinization and rheological characteristics of hot rice starch paste.     

The properties and molecular structures of gusiljatbam starch compared to those of acorn and chestnut starches

The properties and molecular structures of starch from gusiljatbam (GS) (Castanopsis cuspidate), a pine nut‐type fruit with a chestnut taste, compared to starches from an acorn (AS) and a chestnut (CS) were investigated. The starches were isolated using an alkaline steeping method, and analyzed. The TAM contents of GS, AS, and CS were 44.09, 30.56, and 29.55%, respectively. The GS showed the highest water binding capacity (110.83%) and solubility at 80°C (10.00%). The initial pasting temperature of GS was the lowest, but its pasting viscosity was the highest among them. Trough, cold, and setback viscosities and particle sizes were in the following order: GS>AS>CS. The XRD patterns of GS, AS, and CS revealed B, A, and C_b type crystals, respectively. HPSEC showed the MW distribution patterns of the starches as AP, intermediate materials (IM), and AM peaks. However, the MW of AM as well as AP peak intensity and IM patterns were different. According to the branched chain length distribution of AP at DP 13–24 and DP 25–36, DP_n, and DP_w decreased in the following order: GS>AS>CS, but DP 6–12 and DP ≥ 37 were distributed in reverse order.     

Effect of low and high acetylation degree in the morphological, physicochemical and structural characteristics of barley starch

Barley starch was acetylated at two levels (low degree: LD (0.9), and high degree: HD (2.7)) substitution and the morphological, physicochemical and structural of the resultant acetylated barley starch were determined. The acetylated barley starches presented the signal at 1226 cm⁻¹ that corresponds to the C-O stretching of acetyl groups. The morphological study showed fusion of starch granules in the acetylated starch with HD. This effect was evident in the pasting test, because the viscoamylograph profile of HD starch showed the absence in peak viscosity, viscosity breakdown and viscosity setback. The peak gelatinization was similar for native and LD and decrease in the HD acetylated starch. The gelatinization enthalpy value showed difference among the samples, indicating that the loss of the ordered double helices more than the crystallinity loss was higher in the HD acetylated barley starch. In the retrogradation test, acetylation affected both retrogradation and enthalpy value, because acetylated barley starch with HD substitution at three storage days had 3.2 j/g and with LD 4.8 j/g. The molecular weight and z-average radius of gyration values decreased due to the acetylation process, indicating depolymerization of starch components as it was evidenced by the increase in short chains level in the acetylated samples.     

Molecular structure,rheological and thermal characteristics of ozone-oxidized starch

The effects of oxidation by ozone gas on the molecular structure, rheological and thermal properties of starch (corn, sago and tapioca) were investigated. Starch, in dry powder form, was exposed to ozone for 10 min at different ozone generation times (OGTs). Average molecular weight decreased in oxidized corn and sago starches but increased in oxidized tapioca starch. All oxidized starches exhibited non-Newtonian shear-thinning behaviour. Starch viscosity decreased drastically with increasing OGT. Young’s modulus for all oxidized corn and sago starch gels stored for 1 and 7 days at 4 °C increased significantly compared to unmodified starch. No differences were noted in gelatinization temperatures and gelatinization enthalpies of all oxidized starches compared to unmodified starch. Retrogradation enthalpy increased markedly in corn starch after 1 min OGT. These results show that the extent of starch oxidation varies among starches of different botanical origins under similar ozone treatment conditions.     

Elucidation of structural difference in theaflavins for modulation of starch digestion

The relationship between structure and activity of theaflavins against human pancreatic α-Amylase was investigated by in vitro and in silico methods. The IC₅₀ and total energy value showed that inhibitory effects followed the order: theaflavin-3, 3’-di-O-gallate > theaflavin-3’-O-gallate > theaflavin-3-O-gallate > theaflavin. Inhibitory activity was depended on hydroxyl groups and galloyl moieties of theaflavins to interact with the catalytic residues of the active site of α-Amylase by hydrogen bonds and π–π (aromatic–aromatic) interactions. The galloylated theaflavin has higher binding affinity with α-Amylase than non-galloylated theaflavin. The study showed that theaflavins might act as natural enzyme inhibitors with potential health benefits, which provide a foundation for designing novel functional food for effective controlling of starch digestion and postprandial glucose levels.     

The influence of Cu(II) ions on physicochemical properties of potato starch oxidised by hydrogen peroxide

The study investigates the influence of Cu(II) ions used as a catalyst on the effectiveness of potato starch oxidation by hydrogen peroxide, and compares the physicochemical properties of the modified starches. The starch was oxidised by H₂O₂ alone and with the addition of Cu(II) ions at three concentrations: 0.1, 0.2 or 0.3 g per 100 g d.m. of starch. The oxidised starches were examined for the content of carboxyl groups, carbonyl groups, amylose and copper, and for water‐binding capacity and water solubility at temperatures of 60 and 80°C. Colour parameters (L*a*b*), susceptibility to retrogradation, thermodynamic characteristics of pasting, intrinsic viscosity and pasting characteristic by RVA were also determined. The results indicate that the concentration of Cu(II) ions added as a catalyst has an effect on both the effectiveness of the oxidation process and the physicochemical properties of starch.     

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.