Xiangli Kong

Physicochemical properties of starches from diverse rice cultivars varying in apparent amylose content and gelatinisation temperature combinations.

The physicochemical properties of starches isolated from 14 rice cultivars produced in China were investigated. These rice starches showed a non-random combination of AAC and GT. Rice starches showed a typical A-type diffraction pattern with the degree of crystallinity ranging from 32.3% (a high AAC rice) to 45.5% (a waxy rice). AAC was significantly correlated with the pasting, thermal and textural properties. The positive correlations were found with PV, HPV, CPV, SB and HD (p<0.05), while the negative corrections were found with SP, ADH, COH, T(o), T(p), T(c) and ΔH (p<0.05). However, AAC had no correlations with BD, PTime and percentage of retrogradation (R%). The degree of crystallinity and GT had a positive correlation with the retrogradation properties. It could be concluded that although AAC was the major factor affecting the physicochemical properties of rice starch, the retrogradation property of rice starch was mainly determined by the degree of crystallinity and GT.

Fine structure characterization of amylopectins from grain amaranth starch

The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with alpha-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then beta-amylase to remove all external chains, whereby the internal structure was obtained. The phi,beta-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC-PAD). The results showed that the domain fraction contained approximately 2.2 clusters, and single clusters were composed of approximately 13 chains. The phi,beta-limit dextrins of the clusters were further hydrolyzed with alpha-amylase to characterize their building block composition. The average DP of the branched blocks was approximately 11 and they contained on average approximately 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of approximately 6 branched blocks, and the internal chain length between the blocks was approximately 6.8.

Effects of heat-moisture treatment reaction conditions on the physicochemical and structural properties of maize starch: moisture and length of heating.

Changes in the properties of normal maize starch (NMS) and waxy maize starch (WMS) after heat-moisture treatment (HMT) under various reaction conditions were investigated. NMS and WMS were adjusted to moisture levels of 20%, 25% and 30% and heated at 100 °C for 2, 4, 8 and 16 h. The results showed that moisture content was the most important factor in determining pasting properties for NMS, whereas the heating length was more important for WMS. Swelling power decreased in NMS but increased in WMS, and while the solubility index decreased for both samples, the changes were largely determined by moisture content. The gelatinisation temperatures of both samples increased with increasing moisture content but remained unchanged with increasing heating length. The Fourier transform infrared (FT-IR) absorbance ratio was affected to different extents by the moisture levels but remained constant with increasing the heating length. The X-ray intensities increased but relative crystallinity decreased to a greater extent with increasing moisture content. This study showed that the levels of moisture content and length of heating had significant impacts on the structural and physicochemical properties of normal and waxy maize starches but to different extents.

Influence of acid hydrolysis on thermal and rheological properties of amaranth starches varying in amylose content.

BACKGROUND The granules of amaranth starch are very small compared with starches from other sources. In the current work, amaranth starches with different amylose contents were treated with hydrochloric acid as a function of time in order to study the effect of acid treatments on starches. Differential scanning calorimetry and dynamic oscillation in shear were employed to analyse the thermal and rheological properties of acid-modified amaranth starch. RESULTS Results showed that gelatinisation temperatures and enthalpy change of gelatinisation (ΔH) decreased steeply initially, and had a slight increase with further treatment up to 12 h then decreased, an outcome that reflected distinct resistance to acid with various amylose contents. Rheological parameters of storage and loss moduli during heating, cooling and frequency sweep of modified starches reflected the differential scanning calorimetry results by decreasing in value as the time of acid hydrolysis increased. CONCLUSION With amylose content increase, the effects of acid hydrolysis on gelatinisation temperatures became less pronounced. Nevertheless, prolonged acid hydrolysis decreased the storage and loss moduli, with the starch pastes becoming more liquid-like.

Effect of fertiliser on functional properties of flour from four rice varieties grown in Sri Lanka

BACKGROUND Fertiliser is an essential agro-chemical input in modern rice farming. Fertiliser affects the grain quality and yield of rice. Although much research has been carried out to investigate the influence of fertiliser (recommended NPK addition) on yield and quality of rice grain, little is known about the effect of fertiliser on thermal, pasting, gelling and retrogradation properties of rice flour. The aim of this study was to investigate the influence of recommended fertilisation on functional properties of rice flour from four popular high yielding rice varieties grown in Sri Lanka. RESULTS Fertiliser (recommended NPK addition) increased the protein content but reduced the apparent amylose content in rice flour except in BG 357. Swelling power and amylose leaching were decreased by fertilizer. [corrected] Pasting onset temperature, cold paste viscosity and setback were increased but peak viscosity and granular breakdown decreased. In response to the fertiliser application, gelatinisation peak temperature was reduced in all varieties except BG 300. However, compared to pasting properties, gelatinisation parameters were not much affected by fertilisation. The extent of amylopectin retrogradation was decreased by fertiliser in BG 305 and BG 352 but unchanged in the other two varieties. Except in BG 305, fertiliser reduced the gel hardness of rice flour but increased the gel cohesiveness. CONCLUSION It is apparent that the increased protein and reduced amylose content caused by fertiliser affect the functional properties of rice flour.

Mapping of quantitative trait loci for fiber and lignin contents from an interspecific cross Oryza sativa×Oryza rufipogon.

Rice straw is always regarded as a by-product of rice production, but it could be a significant energy source for ruminant animals. Knowledge of the genetic variation and genetic architecture of cell wall traits will facilitate rice breeders by improving relevant traits through selective breeding and genetic engineering. The common wild rice, Oryza rufipogon Griff., which is considered to be the progenitor of Oryza sativa, has been widely utilized for the identification of genes of agronomic importance for rice genetic improvement. In the present study, the mapping of quantitative trait loci (QTLs) for acid detergent fiber (ADF), neutral detergent fiber (NDF), acid detergent lignin (ADL), and ADL/NDF ratio was carried out in two environments using a backcrossed inbred line (BIL) population derived from a cross between the recurrent parent Xieqingzao B (XB) and an accession of Dongxiang wild rice (DWR). The results indicated that all four traits tested were continuously distributed among the BILs, but many BILs showed transgressive segregation. A total of 16 QTLs were identified for the four traits, but no QTLs were in common in two environments, suggesting that environment has dramatic effects on fiber and lignin syntheses. Compared to the QTL positions for grain yield-related traits, there were no unfavorable correlations between grain yield components and cell wall traits in this population. The QTLs identified in this study are useful for the development of dual-purpose rice varieties that are high in grain yield and are also high in straw quality.

Effects of gamma irradiation on physicochemical properties of native and acetylated wheat starches

Effects of gamma irradiation on the physicochemical and crystalline properties of the native and acetylated wheat starches were investigated. Peak, hot paste, cool paste and setback viscosities of both native and acetylated wheat starches decreased continuously and significantly with the increase of the irradiation dose, whereas breakdown viscosity increased after irradiation. However, gamma irradiation only exerted slight effects on thermal and retrogradation properties of both native and acetylated wheat starches. X-ray diffraction and fourier transform infrared spectroscopy revealed that acetylation modification had considerable effects on the molecular structure of wheat starch, and the crystallinity of both untreated and acetylated starches increased slightly with the increase of irradiation dose. However, the V-type crystallinity of amylose-lipid complex was not affected by gamma irradiation treatments with doses up to 9kGy.

Physicochemical and crystalline properties of heat–moisture-treated rice starch: combined effects of moisture and duration of heating

BACKGROUND Currently there is much interest in the application of physical modification techniques such as heat-moisture treatment (HMT). The effects of HMT on normal and waxy rice starches, subject to different levels of moisture content and duration of heating, were investigated. RESULTS Water solubility index (determined at 90 °C) decreased after HMT for normal and waxy rice starches, while swelling power (determined at 90 °C) showed inconsistent results (decrease for normal type, increase for waxy type) after HMT. Values in pasting parameters of normal and waxy rice starch increased initially, but the extent of increase slowed down with moisture content and length of treatment increasing. HMT decreased gelatinization temperatures with 4 h and 8 h treatment, but when length of treatment was prolonged to 16 h gelatinization temperature increased. Degree of crystallinity decreased for all treatments, and decreased much more at higher levels of moisture content. CONCLUSION Variations in levels of moisture content and duration of heating had significant effects on physicochemical and crystalline properties to different extents.

Gamma Irradiation of Starch

As a physical treatment, gamma irradiation has many advantages, such as high efficiency, low-cost, eco-friendship, and no remarkable rise in temperature during the treatment process. The degradation changes of starch by radiation are reproducible and quantitative, without needing special appliances to control temperature and environment. The effects of irradiation on starch have attracted much more attention in the last decade. Gamma radiation may generate free radicals which can contribute to molecular changes and fragmentation of starch. Starch depolymerization leads to progressive reduction in molecular size of amylose and amylopectin by random cleavage of the glycosidic chains, and consequently changes the structural and physicochemical characteristics of starch. Visible or significant changes on starch granules upon irradiation were not found; however, some researchers found that Maltese cross became unclear and fissures or cracks developed on starch granules. To date, all researchers found that the C-type starches showed decrease in amylose content upon gamma irradiation, and most researchers reported that gamma irradiation treatment decreased amylose content in A-type starches but increased amylose content in B-type starches. The X-ray diffraction pattern of starches remained unchanged after gamma irradiation, but the relative crystallinity decreased upon irradiation in most cases; however, some A-type starches exhibited increase in relative crystallinity at low-dose irradiation and then decreased at higher doses. The Fourier transform-infrared spectral pattern of irradiated starch was not altered; however, most intensities increased indicating decreases in the ordered structure of starch upon irradiation. Gelatinization temperatures and enthalpy of gelatinization of A-type starches decreased upon irradiation in most cases. With regard to the B-type starches, the gelatinization parameters showed increase at lower dosage but decreased with irradiation dose increasing in some cases. For C-type starches, the gelatinization parameters were observed to increase by most researchers. The swelling power was observed to decrease under gamma irradiation treatment in most cases, water solubility index of irradiated starches increased with irradiation dosage elevated in all reports, and the syneresis of gels formed with irradiated treated starches decreased. Most pasting and rheological parameters of irradiated starches decreased continuously with irradiation dosage increasing. Gamma irradiation can be employed to elevate the resistant starch fraction, whereas some researchers observed that irradiation treatment could decrease resistant starch content. Radiation processing can promote cross-linking in the starch matrix under oxygen. Graft copolymerization of chemicals onto starch by a simultaneous irradiation technique can also be achieved to produce biodegradable film or superabsorbent hydrogel.