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Sweet potato was planted at three soil and air temperatures (21, 25 and 28 °C) with the same humidity and light time/intensity. Root tuber starches were isolated, and their multi-scale structures were investigated to reveal the effects of growth temperature on starch properties. Growth temperature did not change the morphology and amylose content of starch, but markedly increased the size of starch from volume-weighted mean diameter 12.2 μm to 17.0 μm. Starch grown at high growth temperature exhibited less A branch-chains and lower branching degree of amylopectin and more B2 and B3+ branch-chains of amylopectin than at low growth temperature. With increasing growth temperature, starch changed from C

Three sweet potato varieties with purple-, yellow-, and white-fleshed root tubers were planted in four growing locations. Starches were isolated from their root tubers, their physicochemical properties (size, iodine absorption, amylose content, crystalline structure, ordered degree, lamellar thickness, swelling power, water solubility, and pasting, thermal and digestion properties) were determined to investigate the effects of variety and growing location on starch properties in sweet potato. The results showed that granule size (D[4,3]) ranged from 12.1 to 18.2 μm, the iodine absorption parameters varied from 0.260 to 0.361 for OD620, from 0.243 to 0.326 for OD680 and from 1.128 to 1.252 for OD620/550, and amylose content varied from 16.4% to 21.2% among starches from three varieties and four growing locations. Starches exhibited C-type X-ray diffraction patterns, and had ordered degrees from 0.634 to 0.726 and lamellar thicknesses from 9.72 to 10.21 nm. Starches had significantly different swelling powers, water solubilities, pasting viscosities, and thermal properties. Native starches had rapidly digestible starch (RDS) from 2.2% to 10.9% and resistant starch (RS) from 58.2% to 89.1%, and gelatinized starches had RDS from 70.5% to 81.4% and RS from 10.8% to 23.3%. Two-way ANOVA analysis showed that starch physicochemical properties were affected significantly by variety, growing location, and their interaction in sweet potato.

The kernel properties, gelatinisation and physicochemical properties of rice were investigated in a waxy rice Guang‐ling‐xiang‐nuo (GLXN) and its transgenic line GLXN‐RNAi with inhibition of starch branching enzyme I/IIb. The volume swelling, water content and leached material of cooked kernels increased with increasing cooking time, but they were lower in GLXN‐RNAi than in GLXN. The kernels of GLXN‐RNAi were more difficultly gelatinised and disrupted than those of GLXN during cooking. The starch in the exterior of GLXN‐RNAi endosperm was not completely gelatinised. The CA‐type starch of GLXN‐RNAi was more resistant to cooking than A‐type starch of GLXN. The cooked kernels of GLXN‐RNAi had lower rapidly digestible starch and greater slowly digestible starch than those of GLXN. Brown rice flour had higher peak, hot, final and setback viscosities and lower breakdown viscosity in GLXN than GLXN‐RNAi. These results indicated that GLXN‐RNAi kernels exhibited great potential in applications as health foods.

The extra-long chain (ELC) of amylopectin influences molecular compositions of starch. In this study, starches were isolated from 22 rice varieties with different ELCs. Molecular compositions of starch were determined, and their relationships with crystalline structure, gelatinization properties, pasting properties, and enzyme hydrolysis were analysed. The results showed that the starches with different ELCs had significantly different structural and functional properties. The ELC was significantly positively related to setback viscosity and negatively related to relative crystallinity, lamellar peak intensity, swelling power, gelatinization enthalpy, and rapidly digestible starch of retrograded starch. The true amylose content was significantly positively related to retrogradation and negatively related to peak viscosity and hydrolysis degree by α-amylase and amyloglucosidase. The short branch-chain of amylopectin was significantly positively related to lamellar peak intensity, swelling power, hydrolysis degree by α-amylase, and rapidly digestible starch of retrograded starch and negatively related to setback viscosity and resistant starch of retrograded starch. The ratio of short to long branch-chain of amylopectin was significantly positively related to swelling power and hydrolysis degree by α-amylase. The principal component analysis and partial least squares discriminant analysis demonstrated that the low-ELC starches were distinguished from the middle- and high-ELC starches, the middle-ELC starches basically clustered together, but the high-ELC starches were highly dispersed. The above results would provide some new information for rice quality breeding and starch applications by changing the ELC in starch.

A new starch was isolated from ramie root, and its physicochemical properties were investigated. Ramie dry root contained 45.9% starch. Starch had truncated, ellipsoidal, and spherical granule shapes with size from 7 to 30 μm and D[4,3] about 14.1 μm. Starch contained 38.9% apparent amylose content and 22.4% true amylose content, exhibited B-type crystallinity, and had 26.6% relative crystallinity, 0.82 ordered degree, and 9.2 nm lamellar thickness. Starch had 71.8 °C gelatinization peak temperature and 15.6 J/g gelatinization enthalpy, and exhibited 31.4 g/g swelling power and 17.1% water solubility at 95 °C. Starch had peak, hot, breakdown, final, and setback viscosities at 3048, 2768, 279, 4165, and 1397 mPa s, respectively, and showed peak time at 4.36 min and pasting temperature at 75.0 °C. The native, gelatinized, and retrograded starches contained 15.1%, 94.0%, and 86.5% rapidly digestible starch and 83.3%, 4.0%, and 10.7% resistant starch, respectively. Compared with potato and rice starches, ramie starch was somewhat similar to potato starch but significantly different from rice starch in starch component, crystalline structure, and functional properties. Therefore, ramie starch exhibited the potential to be used as a thickening agent, resistant-digesting food additive, and alternative to potato starch in food and nonfood industries.

The relationship between starch components and hydrolysis previously focused on starches with different amylose contents (ACs) and amylopectin structures. In this study, starches were isolated from six rice seeds with the same genetic background but different activities of granule-bound starch synthase I. The starch components and enzyme hydrolysis were measured and analysed to reveal their relationships. The results showed that the six rice starches had the same amylopectin structure but different ACs ranging from approximately 1%–15%. The starch component parameters measured by different methods were significantly correlated with each other. The hydrolysis parameters of starch by both α-amylase and amyloglucosidase were analysed using three methods including a non-linear fit to the degree of hydrolysis, a first-order kinetics fit to the degree of hydrolysis, and a first-order kinetics fit to the hydrolysis rate, and they had significant correlation each other. Waxy starch had a fast hydrolysis rate and showed a single hydrolysis phase during early hydrolysis, while starch with a high AC had a bi-phasic hydrolysis process. Starch component parameters including the maximum absorption wavelength, iodine blue, AC, and low molecular weight fraction were significantly negatively correlated to the hydrolysis rate of starch. The above results indicated that starches with different ratios of amylose to amylopectin but the same amylopectin structure had significantly different hydrolysis properties. This study could provide some information for rice quality breeding and starch applications through changing the activity of granule-bound starch synthase I.

Rice mutants with altered starch components and properties are important genetic resources in rice breeding programmes. In this study, 44 mutants with altered starch components were screened from 135 rice mutants with opaque kernels using a starch&ndash, iodine absorption spectrum method, and nine mutants from them were further selected for investigating their starch properties and kernel appearance quality. The results showed that the iodine absorption spectrum parameters, OD620, OD620/550, and &lambda, max, could reflect the changes of starch components in rice mutants, and had significantly positive relationships with amylose content and negative relationships with the proportion of short branch-chains of amylopectin. The endosperm starches from nine mutants all showed A-type crystalline structure and similar short-range ordered structure, but had different relative crystallinities. The changes of starch components in mutants not only resulted in the different gelatinization properties of starch but also changed the appearance quality of brown rice kernels. This study provided abundant genetic plants for studying the molecular mechanism of starch synthesis and the quality regulation of rice kernels.

Rice (Oryza sativa) endosperm is mainly occupied by homogeneous polygonal starch from inside to outside. However, morphologically different (heterogeneous) starches have been identified in some rice mutants. How these heterogeneous starches form remains unknown. A high-amylose rice line (TRS) generated through the antisense inhibition of starch branching synthase I (SBEI) and SBEIIb contains four heterogeneous starches: polygonal, aggregate, elongated, and hollow starch; these starches are regionally distributed in the endosperm from inside to outside. Here, we investigated the relationship between SBE dosage and the morphological architecture of heterogeneous starches in TRS endosperm from the view of the molecular structure of starch. The results indicated that their molecular structures underwent regular changes, including gradually increasing true amylose content but decreasing amylopectin content and gradually increasing the ratio of amylopectin long chain but decreasing the ratio of amylopectin short chain. Granule-bound starch synthase I (GBSSI) amounts in the four heterogeneous starches were not significantly different from each other, but SBEI, SBEIIa, and SBEIIb showed a gradually decreasing trend. Further immunostaining analysis revealed that the gradually decreasing SBEs acting on the formation of the four heterogeneous granules were mainly due to the spatial distribution of the three SBEs in the endosperm. It was suggested that the decreased amylopectin in starch might remove steric hindrance and provide extra space for abundant amylose accumulation when the GBSSI amount was not elevated. Furthermore, extra amylose coupled with altered amylopectin structure possibly led to morphological changes in heterogeneous granules.

Rice is principally consumed as cooked kernels. A high-amylose rice line, TRS, has a potential to positively impact human health. Though the properties of starch isolated from TRS kernels have been studied, the properties of cooked kernel remain to be resolved. In this study, the changes in kernel morphology and starch properties of brown TRS were investigated during cooking in boiling water. TRS kernel, which had polygonal, aggregate, elongated, and interior hollow starches from the inner to the outer of endosperm, showed different gelatinization properties during cooking. The polygonal starch was gelatinized most completely and fastest, the aggregate starch was partly gelatinized, and the elongated and interior hollow starches kept almost their intact status. The molecular weight distribution of starch in kernel did not show significant change, but starch crystalline structure was not wholly disrupted during the cooking process. The starch in cooked kernel had a very high resistance to digestion.

Arisaema elephas, yunnanense, and erubescens had 15.37, 61.60, and 52.91% starch content in their dry tubers. However, their starch properties have not been reported. In this study, starches were isolated from fresh tubers and characterized. Three starches all had spherical, irregular and truncated shapes with central hila, but Arisaema elephas starch had more irregular granules with small size, Arisaema yunnanense starch had more truncated granules with medium size, and Arisaema erubescens starch had more spherical granules with large size. The amylose content varied from 29.1 to 32.0% among three starches. A. elephas and yunnanense starches had CA-type crystallinity, and A. erubescens starch showed A-type crystallinity. A. elephas and erubescens starch had the lowest and highest short-range ordered degree, respectively. The swelling power at 95 °C, gelatinization peak temperature, and breakdown viscosity varied from 22.4 to 29.1 g/g, from 69.8 to 73.8 °C, and from 208 to 392 dPa s, respectively, and were the highest in A. erubescens starch and the lowest in elephas starch. The water solubility at 95 °C and setback viscosity varied from 10.2 to 15.0% and from 587 to 755 dPa s, respectively, and were the lowest in A. erubescens starch and the highest in elephas starch. A. elephas and erubescens starch had lower and higher resistance to amylase hydrolysis and in vitro digestion, respectively. The above results would be useful for the applications of starches from A. elephas, yunnanense and erubescens tubers in food and nonfood industries.

Biphasic starch granules in maize ae mutant underwent the weak to strong SBEIIb-defective effect during endosperm development, leading to no birefringence in their exterior due to extended long branch-chains of amylopectin. Biphasic starch granules are usually detected regionally in cereal endosperm lacking starch branching enzyme (SBE). However, their molecular structure, formation mechanism, and regional distribution are unclear. In this research, biphasic starch granules were observed in the inner region of crown endosperm of maize ae mutant, and had poorly oriented structure with comb-like profiles in their exterior. The inner endosperm (IE) rich in biphasic starch granules and outer endosperm (OE) without biphasic starch granules were investigated. The starch had lower amylose content and higher proportion of long branch-chains of amylopectin in IE than in OE, and the exterior of biphasic starch granules had less amylose and more long branch-chains of amylopectin than the interior. Compared with OE, the expression pattern of starch synthesis related enzymes changed significantly in IE. The granule-bound starch synthase I activity within biphasic starch granules decreased slightly. The IE experienced more severe hypoxic stress than OE, and the up-regulated anaerobic respiration pathway indicated an increase in carbon consumption. The starch in IE underwent the SBEIIb-defective effect from weak to strong due to the lack of sufficient carbon inflow, leading to the formation of biphasic starch granules and their regional distribution in endosperm. The results provided information for understanding the biphasic starch granules.

Kernel components and some physicochemical properties of cooked rice were investigated and compared between a popular japonica rice Wu-xiang 9915 (WX) and its transgenic line (WX-SBEI/IIb-) with suppression of starch branching enzyme I/IIb. The starch content, especially amylopectin content, was significantly lower in WX-SBEI/IIb- than in WX. Brown rice flour had markedly higher gelatinization temperature in WX-SBEI/IIb- than in WX. The cooked kernels of WX-SBEI/IIb- had significantly lower volume swelling, leached material amount and wet weight than those of WX during cooking. Starch granules in WX kernel could be gelatinized completely and gradually from the exterior to the interior of endosperm, leading to breakage of cooked kernels. However, aggregate, elongated and small starch granules in the exterior of WX-SBEI/IIb- endosperm could not be gelatinized completely and remained their morphologies during cooking, leading to a high resistance of kernels to cooking. Brown rice flour of WX-SBEI/IIb- had significantly lower pasting viscosities, storage modulus and loss modulus but higher loss angle tangent than that of WX. The cooked kernels of WX-SBEI/IIb- had considerably higher hardness, springiness and cohesiveness but lower adhesiveness than those of WX. The starch in cooked kernels was more resistant to digestion in WX-SBEI/IIb- than in WX.

The dry root tuber of Stephania epigaea contained 36.5% starch, indicating a good starch source. In this study, starch was isolated from S. epigaea. Its morphology, physicochemical, and functional properties were investigated and compared with potato and maize starches. S. epigaea starch had small spherical granules with centric hila and large ellipsoidal granules with eccentric hila, and granule sizes varied from 7 to 40 μm. The starch had 33.9% amylose content and B-type crystallinity. The gelatinization onset, peak, and final temperatures were 59.4, 62.3, and 66.2°C, respectively, and were lower than those of potato and maize starches, but the enthalpy (16.3 J/g) was higher than that of potato and maize starches. The peak, hot, final, and breakdown viscosities were 2227, 1623, 2149, and 594 dPa s, respectively, and were significantly higher than those of maize starch and lower than those of potato starch. S. epigaea starch was more susceptible to amylase hydrolysis and in vitro digestion than p...

High-amylose maize starch has health benefits and special industrial uses. In this study, starches were isolated from normal maize and high-amylose inbred and hybrid maizes. Their molecular structure and enzymatic hydrolysis properties were investigated and analyzed. The high-amylose hybrid maize starch contained lower amylose, intermediate component, amylopectin long branch-chains, and amylopectin average chain length, and higher amylopectin short branch-chains than did high-amylose inbred maize starch. High-amylose maize starch was more resistant to α-amylase and amyloglucocidase hydrolysis and had a significantly lower hydrolysis rate coefficient than normal maize starch did. The native, gelatinized and retrograded starches of the high-amylose hybrid maize had significantly higher rapidly digestible starch and lower resistant starch than those of the high-amylose inbred maize. The retrogradation of gelatinized starch markedly increased the resistance of high-amylose starch to in vitro digestion. The high contents of amylose and intermediate component and the long branch-chains of amylopectin increased the resistance of maize starch to enzymatic hydrolysis and in vitro digestion.

High-amylose rice endosperm contains polygonal, aggregate, elongated, and hollow starch granules. In this study, in vitro digestion properties of native starches and structural properties of undigested starch residues were investigated. The polygonal and aggregate starches had monophasic digestograms and the elongated and hollow starches had biphasic digestograms from 0 to 8 h of digestion, but only the digestions of polygonal and aggregate starches were well fitted by first-order kinetics. The elongated and hollow starches were rapidly degraded in first 20 min of digestion, but had high resistance to degradation after 2 h of digestion. The polygonal and aggregate starches had side-by-side digestions of amylose and amylopectin as well as crystalline and amorphous components, but amylose and amorphous component of elongated and hollow starches were rapidly degraded in first 20 min of digestion. The B-type allomorph in aggregate, elongated, and hollow C-type starches contributed to the resistance to digestion.

The amylopectin molecular structures and functional properties of different-sized fractions of normal and high-amylose maize starches were investigated and compared in this study. The different-sized fractions of normal starch showed similar amylopectin molecular structures and functional properties. The small-sized fraction of high-amylose starch had significantly higher amylopectin long branch-chain and average branch-chain length than its counterpart medium- and large-sized fractions. The swelling power, gelatinization enthalpy, and hydrolysis and digestion degrees of high-amylose starch significantly decreased with decrease of granule size, and were significantly positively correlated with amylopectin short branch-chain and negatively correlated with amylopectin long branch-chain and average branch-chain length. The gelatinization peak temperature and resistant starch content increased with decrease of granule size, and were significantly positively correlated with amylopectin long branch-chain and average branch-chain length and negatively correlated with amylopectin short branch-chain. The hierarchical cluster analysis indicated that the large-sized fraction of high-amylose starch was significantly different from the medium- and small-sized fractions of high-amylose starch but more relative with normal starch. The above results could provide important information for the applications of different-sized fractions of high-amylose maize starch.

High-amylose maize starch is of interest because of its health benefits and industrial uses. Hybrid maize is widely grown for the practical and economical value of heterosis. However, starch structure of high-amylose hybrid maize has seldom been reported compared with that of high-amylose inbred maize. In this study, structure of starches from high-amylose maize inbred lines and their hybrids was investigated and compared. Starch granule became smaller in size and more spherical, oval or elongated in shape with increasing amylose content. Hybrid maize starch had lower amylose content and long branch-chain of amylopectin and higher short branch-chain and branching degree of amylopectin than inbred maize starch. Inbred maize starch had B-type crystalline structure with low relative crystallinity, but hybrid maize starch had CB-type crystalline structure and high relative crystallinity. Hybrid maize starch had lower degree of order at a short-range scale on the edge of starch granule than inbred maize starch. Hybrid maize starch had higher double helix content and lower amorphous starch than inbred maize starch. Hybrid maize starch had higher peak intensity and longer Bragg spacing of lamellar structure than inbred maize starch. Hybrid maize starch had lower gelatinization temperature and higher gelatinization enthalpy and swelling power than inbred maize starch. The different structural properties of starches had significant correlation.

Three rice varieties, Te-qing (TQ), Wu-xiang 9915 (WX) and Guang-ling-xiang-nuo (GLXN) with different amylose contents, and their derived lines with inhibition of starch branching enzyme I and IIb (SBEI/IIb) (GLXN-, WX- and TQ-SBEI/IIb–) were used to investigate and compare the starch ordered structure and component accumulation in developing kernels. The starches in developing kernels of TQ, WX and GLXN all showed a typical A-type crystallinity and had similar short-range ordered structure, but their relative crystallinities gradually decreased in TQ and WX and had no significant change in GLXN with kernel development. For wild-type rices, starch components gradually increased in developing kernels. With inhibition of SBEI/IIb, the accumulation of amylose and amylopectin long branch-chains in kernels was slightly affected, but amylopectin short branch-chains seriously decreased, resulting in a significantly lower dry weight and starch content in kernel. The B-type crystallinity in developing starch gradually accumulated with kernel development of TQ-, Wx- and GLXN-SBEI/IIb– lines. The inhibition of SBEI/IIb decreased the relative crystallinity but increased the short-range ordered structure of starches. The effects of inhibition of SBEI/IIb on starch ordered structure and component accumulation mainly appeared after 10 days after flowering, and were the most conspicuous for indica rice TQ. Though the inhibition of SBEI/IIb influenced the ordered structure and component accumulation of starch, the starch content and components in developing kernels all showed significantly positive correlations with kernel dry weight.

Starches were isolated from vitreous and floury endosperms from the same kernels, and their physicochemical properties were investigated to reveal their differences. Starch from vitreous endosperm had more surface indentations, larger granule size, and higher contents of protein, amylose and damaged starch than that from floury endosperm. Both starches from vitreous and floury endosperms exhibited A-type crystalline structure, but starch from vitreous endosperm had lower relative crystallinity and lamellar peak intensity than that from floury endosperm. Starch from floury endosperm had higher gelatinization temperature and enthalpy but lower gelatinization temperature range and percentage of retrogradation than that from vitreous endosperm. Native starch from floury endosperm was more resistant to enzyme hydrolysis than that from vitreous endosperm. Gelatinized and retrograded starches had similar digestion properties between starches from vitreous and floury endosperms. Principal component analysis indicated that starches from vitreous and floury endosperms had significant differences in their physicochemical properties.

Cereal crops with inhibition expression of starch branching enzyme (SBE) contain highly resistant starch in the endosperm, and have potential health benefits for human. However, seed plumpness is significantly different, with different inhibition effects of SBE expression, resulting in differently shrunken seeds. In this study, a transgenic resistant starch rice line, which has highly resistant starch and is developed through inhibition expression of SBEs, had non-, slightly, and moderately shrunken seeds with plumpness from high to low. The differently shrunken seeds had significantly different seed weight and starch content. Different morphological starch granules were detected in the endosperm and had similar spatial distribution pattern among the non-, slightly, and moderately shrunken seeds. Starches from differently shrunken seeds had similar amylose content and amylopectin structure. The protein amount of amylose/amylopectin synthesis key enzymes in endosperm was no different between differently shrunken seeds. The primary branch of the panicle had a higher percentage of non-shrunken seeds than did the secondary branch at the same part of the panicle. From the upper part to the base of the panicle, non-shrunken seeds gradually decreased but slightly and moderately shrunken seeds gradually increased. The above results indicated that the differently shrunken seeds in transgenic rice line had the same SBE dosage, and the starch morphology and structure had no relationship with seed plumpness. The grain position on the panicle influenced seed plumpness, but had no effect on starch properties.

Green banana fruit is an important starch resource that consists of flesh and peel. The physicochemical properties of flesh starch have been widely studied, however, those of peel starch have hardly been studied, leading to the waste of peel. In this study, the physicochemical properties of the starches from the flesh and peel of green banana fruit were investigated and compared. The dry flesh and peel had 69.5% and 22.6% starch content, respectively. The starch had oval and irregular granules with eccentric hila. Their starches had similar bimodal size distribution, the volume-weighted mean diameter was approximate 17 &mu, m, and the peel starch had a slightly smaller granule size than the flesh starch. The maximum absorption wavelength was higher in peel starch than in flesh starch. The apparent amylose content of flesh and peel starch was 21.3% and 25.7%, respectively. The flesh and peel starches both exhibited B-type crystalline structures and had similar relative crystallinity, short-range ordered degrees, and lamellar structures. The swelling power was similar between flesh and peel starches, but the water solubility was higher in peel starch than in flesh starch at 95 &deg, C. The peel starch had a higher gelatinization temperature than flesh starch, but their gelatinization temperature range and enthalpy were similar. Both flesh and peel starches showed a diphasic hydrolysis dynamic, but peel starch had higher resistance to porcine pancreatic &alpha, amylase hydrolysis than flesh starch. The contents of rapidly digestible starch, slowly digestible starch, and the resistant starch of flesh and peel were 1.7%, 4.3%, 94.1% and 1.4%, 3.4%, 95.2%, respectively, for native starch, and 73.0%, 5.1%, 21.9%, and 72.3%, 4.5%, 23.2%, respectively, for gelatinized starch.

Mature endosperm was separated regionally into different parts in three rice cultivars, Te-qing (TQ), Wu-xiang 9915 (WX9915) and Guang-ling-xiang-nuo (GLXN), and their transgenic lines with inhibition of starch branching enzyme I and IIb (SBEI/IIb-). Within the three wild-type cultivars, starches from endosperm different regions showed similar molecular and crystalline structures. However, in rices with inhibition of SBEs, amylopectin short branch-chain content and branching degree gradually decreased, but amylopectin B3+ chain content and average chain length increased gradually from the interior to exterior of endosperm. The amylose content gradually increased from the interior to exterior of endosperm in TQ- and WX9915-SBEI/II- lines. From the interior to exterior of endosperm, starch changed gradually from CC- to CB-type in TQ-SBEI/II- line and from CA- to CC-type in GLXN-SBEI/II- line, and remained CA-type in WX9915-SBEI/II- line. These results provided some information for quality breeding and utilizations of rice with inhibition of SBE.

Starch, as a main energy storage substance, plays an important role in plant growth and human life. Despite the fact that several enzymes and regulators involved in starch biosynthesis have been identified, the regulating mechanism of starch synthesis is still unclear. In this study, we isolated a rice floury endosperm mutant M14 from a mutant pool induced by 60Co. Both total starch content and amylose content in M14 seeds significantly decreased, and starch thermal and pasting properties changed. Compound starch granules were defected in the floury endosperm of M14 seeds. Map-based cloning and a complementation test showed that the floury endosperm phenotype was determined by a gene of OsPPDKB, which encodes pyruvate orthophosphate dikinase (PPDK, EC 2.7.9.1). Subcellular localization analysis demonstrated that PPDK was localized in chloroplast and cytoplasm, the chOsPPDKB highly expressed in leaf and leaf sheath, and the cyOsPPDKB constitutively expressed with a high expression in developing endosperm. Moreover, the expression of starch synthesis-related genes was also obviously altered in M14 developing endosperm. The above results indicated that PPDK played an important role in starch metabolism and structure in rice endosperm.

Starches with comb-like profiles have been detected in some cereal endosperms with inhibiting expression of starch branching enzyme (SBE). Although amylose is considered to be an important factor in the formation of the comb-like profile, the details remain unclear. In this study, a transgenic rice line (GLXN-SBEI/IIb-) was derived from japonica waxy rice cultivar Guang-ling-xiang-nuo (GLXN) through antisense RNA inhibition of both SBEI and SBEIIb. The expression and activity of SBEI, SBEIIb and SBEIIa were declined. The GLXN-SBEI/IIb- endosperm contained large and small starch granules, and these starch granules had the comb-like profiles. The comb-like profiles of starches were detected in GLXN-SBEI/IIb- endosperm after 10 days after flowering with gradually increasing proportion of long branch-chains of amylopectin. The long branch-chains of amylopectin were responsible for forming the comb-like profiles at the outer region of starch granules. The gradually decreasing expression of SBEs influenced the synthesis of amylopectin during endosperm development, resulting in different structure between the inner and outer regions of starch granules from GLXN-SBEI/IIb- endosperm. The above results indicated that the long branch-chains of amylopectin, not amylose, led to the formation of comb-like profiles of starch granules in cereal crops with inhibiting expression of SBEs.

Rice starches with different amylose contents were treated with sodium dodecyl sulfate (SDS) to deplete surface proteins and lipids, and the changes in molecular structure, thermal properties, and enzymatic hydrolysis were evaluated. SDS treatment did not significantly change the molecular weight distribution, crystalline structure, short-range ordered degree, and gelatinization properties of starch, but significantly altered the pasting properties and increased the swelling power of starch. The removal of surface proteins and lipids increased the enzymatic hydrolysis and in vitro digestion of starch. The influences of removing surface proteins and lipids from starch on swelling power, pasting properties, and enzymatic hydrolysis were different among the various starches because of the differences in molecular structures of different starch styles. The aforementioned results indicated that removing the surface proteins and lipids from starch did not change the molecular structure but had significant effects on some functional properties.

Chinese yam is an important edible starch plant and widely cultivated in China. Its rhizome and bulbil are starch storage tissues below and above ground, respectively. In this paper, starches were isolated from the rhizome and bulbil of Chinese yam, and their structural and functional properties were compared. Both starches had an oval shape with an eccentric hilum and a CA-type crystalline structure. Their short-range ordered structure and lamellar structure had no significant difference. However, the rhizome starch had a significantly bigger granule size and lower amylose content than the bulbil starch. The swelling power and water solubility were significantly lower in the rhizome starch than in the bulbil starch. The onset and peak gelatinization temperatures were significantly higher in the rhizome starch than in the bulbil starch. The rhizome starch had a significantly higher breakdown viscosity and a lower setback viscosity than the bulbil starch. The thermal stability was lower in the rhizome starch than in the bulbil starch. The rhizome starch had a significantly lower resistance to hydrolysis and in vitro digestion than the bulbil starch. The above results provide important information for the utilization of rhizome and bulbil starches of Chinese yam.

Background Endosperm starch provides prime energy for cereal seedling growth. Cereal endosperm with repression of starch branching enzyme (SBE) has been widely studied for its high resistant starch content and health benefit. However, in barley and maize, the repression of SBE changes starch component and amylopectin structure which affects grain germination and seedling establishment. A high resistant starch rice line (TRS) has been developed through inhibiting SBEI/IIb, and its starch has very high resistance to in vitro hydrolysis and digestion. However, it is unclear whether the starch resists in situ degradation in seed and influences seedling growth after grain germination. Results In this study, TRS and its wild-type rice cultivar Te-qing (TQ) were used to investigate the seedling growth, starch property changes, and in situ starch degradation during seedling growth. The slow degradation of starch in TRS seed restrained the seedling growth. The starch components including amylose and amylopectin were simultaneously degraded in TQ seeds during seedling growth, but in TRS seeds, the amylose was degraded faster than amylopectin and the amylopectin long branch-chains with B-type crystallinity had high resistance to in situ degradation. TQ starch was gradually degraded from the proximal to distal region of embryo and from the outer to inner in endosperm. However, TRS endosperm contained polygonal, aggregate, elongated and hollow starch from inner to outer. The polygonal starch similar to TQ starch was completely degraded, and the other starches with long branch-chains of amylopectin and B-type crystallinity were degraded faster at the early stage of seedling growth but had high resistance to in situ degradation during TRS seedling growth. Conclusions The B-type crystallinity and long branch-chains of amylopectin in TRS seed had high resistance to in situ degradation, which inhibited TRS seedling growth. Electronic supplementary material The online version of this article (10.1186/s12870-017-1219-8) contains supplementary material, which is available to authorized users.

Starch was isolated from the kernels of jackfruit, longan, loquat, litchi, and mango fruits, which contained approximately 56, 59, 71, 53, and 64% starch, respectively, indicating that these fruit kernels are good starch sources. The structural and functional properties of these isolated starches were investigated and compared. The starches had irregular, truncated, spherical, and elliptical shapes with central hila and exhibited different sizes, with mango starch being the largest and jackfruit and longan starches being the smallest. The five starches had similar amylose contents but exhibited significantly different crystalline properties including crystalline type, relative crystallinity, short-range ordered structure, and lamellar intensity. Among the five starches, the jackfruit and loquat starches had the highest and lowest gelatinization temperature and enthalpy, respectively, and the litchi and mango starches had the highest and lowest pasting viscosity, respectively. The longan and loquat starches were more susceptible to enzyme hydrolysis than the other starches.

The molecular structural parameters of six normal rice starches with different amylose contents were investigated through their iodine absorption spectra and gel permeation chromatography of fully branched and debranched starches. The thermal and digestion properties of starches were also determined and their relationships with molecular structural parameters were analyzed. Results showed that the molecular structural parameters of maximum absorption wavelength, blue value (BV), optical density 620 nm/550 nm (OD 620/550), amylose, intermediate component, and amylopectin, including its short branch-chains, long branch-chains, and branching degree, had high correlation in different determining methods. The intermediate component of starch was significantly positively related to amylose and negatively related to amylopectin, and the amylopectin branching degree was significantly positively related to amylopectin content and negatively related to amylose content. The gelatinization temperatures and enthalpy of native starch were significantly positively related to BV, OD 620/550, and amylose content and negatively related to amylopectin short branch-chains. The gelatinization temperatures and enthalpy of retrograded starch were significantly negatively related to amylopectin branching degree. The digestions of gelatinized and retrograded starches were significantly negatively related to the BV, OD 620/550, amylose, and intermediate component and positively related to amylopectin and its short branch-chains and branching degree.

High-resistant starch cereal crops with the inhibition of the starch branching enzyme (SBE) have been widely studied. However, the effects of the inhibition of SBE on waxy cereal crops are unclear. A transgenic rice line (GTR) derived from a japonica waxy rice cultivar Guang-ling-xiang-nuo (GLXN) has been developed through antisense RNA inhibition of both SBEI and SBEIIb. In this study, GLXN and GTR were cultivated in the dark only in deionized H2O, and their shoot and root growth, starch in situ degradation, and starch property changes were investigated during seedling growth. Compared with GLXN, GTR showed a significantly slow seedling growth, which was not due to the embryo size and vitality. The slow degradation of starch in the seed restrained the seedling growth. GLXN starch was completely degraded gradually from the proximal to distal region of the embryo and from the outer to inner region in the endosperm, but GTR starch in the peripheral region of the endosperm was not completely degraded, and the starch residual was located in the outside of the compound starch though its degradation pattern was similar to GLXN. During seedling growth, GLXN starch had the same A-type crystallinity and a similar ordered structure, but the crystallinity changed from the CA-type to B-type and the ordered structure gradually increased in the GTR starch. The above results indicated that GTR had a heterogeneous starch distributed regionally in the endosperm. The starch in the peripheral region of the endosperm had a B-type crystallinity, which was located in the outside of the compound starch and significantly increased the resistance to in situ degradation, leading to the seedling slow growth.

Lotus rhizome C-type starch was separated into different size fractions. Starch morphologies changed from irregular to elongated, ellipsoid, oval, and spherical with decreasing granule size. The small- and very-small-sized fractions had a centric hilum, and the other size fractions had an eccentric hilum. The different size fractions all showed C-type crystallinity, pseudoplasticity and shear-thinning rheological properties. The range of amylose content was 25.6 to 26.6%, that of relative crystallinity was 23.9 to 25.8%, that of swelling power was 29.0 to 31.4 g/g, and that of gelatinization enthalpy was 12.4 to 14.2J/g. The very-small-sized fraction had a significantly lower short-range ordered degree and flow behavior index and higher scattering peak intensity, water solubility, gelatinization peak temperature, gelatinization conclusion temperature, consistency coefficient, hydrolysis degrees, and digestion rate than the large-sized fraction. Granule size significantly positively influenced short-range ordered structure and swelling power and negatively influenced scattering peak intensity, water solubility, hydrolysis and digestion of starch (p

Large-, medium-, and small-sized granules were separated from normal and high-amylose maize starches using a glycerol centrifugation method. The different-sized fractions of normal maize starch showed similar molecular weight distribution, crystal structure, long- and short-range ordered structure, and lamellar structure of starch, but the different-sized fractions of high-amylose maize starch showed markedly different structural properties. The amylose content, iodine blue value, amylopectin long branch-chain, and IR ratio of 1045/1022 cm(-1) significantly increased with decrease of granule size, but the amylopectin short branch-chain and branching degree, relative crystallinity, IR ratio of 1022/995 cm(-1), and peak intensity of lamellar structure markedly decreased with decrease of granule size for high-amylose maize starch. The large-sized granules of high-amylose maize starch were A-type crystallinity, native and medium-sized granules of high-amylose maize starch were CA-type crystallinity, and small-sized granules of high-amylose maize starch were C-type crystallinity, indicating that C-type starch might contain A-type starch granules.

High-amylose cereal starches usually have heterogeneous starch granules in morphological structure. In the present study, the polygonal, aggregate, elongated, and hollow starch granules were separated from different regions of the kernels of high-amylose rice, and their structures were investigated. The results showed that the polygonal starch granules had low amylose content and high short branch-chain and branching degree of amylopectin, and exhibited A-type crystallinity. The aggregate starch granules had high long branch-chain of amylopectin, relative crystallinity, and double helix content, and exhibited C-type crystallinity. The elongated starch granules had high amylose content and low branching degree of amylopectin and relative crystallinity, and exhibited C-type crystallinity. The hollow starch granules had very high amylose content, proportion of amorphous conformation, and amylose-lipid complex, and very low branch-chain of amylopectin, branching degree of amylopectin, and double helix content, and exhibited no crystallinity. The different structures of heterogeneous starch granules from high-amylose rice resulted in significantly different thermal properties.