Granule structure and distribution of allomorphs in C-type high-amylose rice starch granule modified by antisense RNA inhibition of starch branching enzyme

Changes of crystalline structure and physicochemical properties of Pueraria lobata var. thomsonii starch under water deficit

Crystal type is an important physicochemical property of starch. However, it is currently unclear whether changes in crystal type affect other properties of starch. This study discovered that water deficit resulted in an increase in small starch granules and transparency in Pueraria lobata var. thomsonii, while causing a decrease in amylose content and swelling power. Additionally, the crystal type of P. Thomsonii starch changed from CB-type to CA-type under water deficit, without significantly altering the short-range ordered structure and chain length distribution of starch. This transformation in crystal type led to peak splitting in the DSC heat flow curve of starch, alterations in gelatinization behavior, and an increase in resistant starch content. These changes in crystalline structure and physicochemical properties of starch granules are considered as adaptive strategies employed by P. Thomsonii to cope with water deficit.

Physicochemical properties of starches from sweet potato root tubers grown in natural high and low temperature soils

Three sweet potato varieties grew in natural high temperature (HT) and low temperature (LT) field soils. Their starch physicochemical properties were affected similarly by HT and LT soils. Compared with LT soil, HT soil induced the increases of granule size D[4,3] from 18.0-18.7 to 19.9-21.8 μm and amylopectin average branch-chain length from 21.9-23.1 to 24.1-24.7 DP. Starches from root tubers grown in HT and LT soils exhibited CA- and CC-type XRD pattern, respectively. Starches from root tubers grown in HT soil exhibited stronger lamellar peak intensities (366.8-432.0) and higher gelatinization peak temperature (72.0-76.8 °C) than those (176.2-260.5, 56.4-63.4 °C) in LT soil. Native starches from root tubers grown in LT soil were hydrolyzed more easily (hydrolysis rate coefficient 0.227-0.282 h-1) by amylase than those (0.120-0.163 h-1) in HT soil. The principal component analysis exhibited that starches from root tubers grown in HT and LT soils had significantly different physicochemical properties.

Correlation between in vitro starch digestibility and starch structure/physicochemical properties in rice

Natural resistant starch (RS) in rice provides human health benefits, and its concentration in rice is influenced by the structure and physicochemical properties of starch. The native starch structures and physicochemical properties of three rice varieties, QR, BR58, and BR50, and their relationships to in vitro digestibility were studied. The starch granules in all three varieties were irregular or polyhedral in shape. There were a few oval granules and a few pinhole structures in QR, no oval granules but a higher number of pinholes in BR58, and no oval granules and pinholes in BR50. QR is a low-amylose (13.8 %), low-RS (0.2 %) variety. BR58 is a low-amylose (15.3 %), high-RS (6.5 %) variety. BR50 is a high-amylose (26.7 %), high-RS (8.3 %) variety. All three starches exhibited typical A-type diffraction patterns. Starch molecular weight, chain length distribution, starch branching degree, pasting capabilities, and thermal properties differed considerably between the rice starches. The RS contents of the rice starch varieties were positively correlated with AAC, Mw/Mn, Mz/Mn, peak 3, B, PTime, and Tp and negatively correlated with Mn, peak 2, DB, PV, and BD, according to Pearson's correlation analysis. These findings may be helpful for the breeding and development of high-RS rice varieties.

The differences in metabolites, starch structure, and physicochemical properties of rice were related to the decrease in taste quality under high nitrogen fertilizer application

Nitrogen fertilizer application is one of the key cultivation practices to improve rice yields. However, the application of high nitrogen fertilizers often leads to a reduction in the stickiness of the rice after cooking, thus reducing the taste quality of rice. Moreover, there are differences in taste quality among rice varieties, and the mechanism has not been studied in depth. In this study, two rice varieties (Meixiangzhan2hao and Exiang2hao) were planted under two nitrogen fertilizer levels. The physicochemical properties and taste quality of the rice were determined after maturity. Our results showed that high nitrogen fertilizer level alters tryptophan metabolism in rice, increasing most amino acid content and protein content in rice. The high content of protein and the higher short-range ordered structure of starch inhibited the gelatinization characteristics of starch and reduced the taste quality of rice. Under high nitrogen fertilizer application, Exiang2hao showed smaller increases in protein content, lower level of amylose and relative crystallinity, and higher content of lipid metabolites. These differences in chemical substances resulted in a less pronounced reduction in the taste quality of Exiang2hao. In this study, the taste quality of different rice varieties under different levels of nitrogen fertilizer application was analyzed, providing new ideas for future improvement of rice taste quality.

Discrepancies in resistant starch and starch physicochemical properties between rice mutants similar in high amylose content

The content of resistant starch (RS) was considered positively correlated with the apparent amylose content (AAC). Here, we analyzed two Indica rice mutants, RS111 and Zhedagaozhi 1B, similar in high AAC and found that their RS content differed remarkably. RS111 had higher RS3 content but lower RS2 content than Zhedagaozhi 1B; correspondingly, cooked RS111 showed slower digestibility. RS111 had smaller irregular and oval starch granules when compared with Zhedagaozhi 1B and the wild type. Zhedagaozhi 1B showed a B-type starch pattern, different from RS111 and the wild type, which showed A-type starch. Meantime, RS111 had more fa and fb1 but less fb3 than Zhedagaozhi 1B. Both mutants showed decreased viscosity and swelling power when compared with the parents. RS111 had the lowest viscosity, and Zhedagaozhi 1B had the smallest swelling power. The different fine structures of amylopectin between RS111 and Zhedagaozhi 1B led to different starch types, gelatinization properties, paste viscosity, and digestibility. In addition to enhancing amylose content, modifications on amylopectin structure showed great potent in breeding rice with different RS2 and RS3 content, which could meet the increasing needs for various rice germplasms.

Loss of ADP-glucose transporter in barley sex1 mutant caused shrunken endosperm but with elevated protein and β-glucan content in whole meal

Grain shape and plumpness affect barley yield. Despite numerous studies on shrunken endosperm mutants in barley, their molecular mechanism and application potential in the food industry are largely unknown. Here, map-based cloning, co-segregation analyses, and allelic variant validation revealed that the loss of HORVU6Hr1G037950 encoding an ADP-glucose transporter caused the shrunken endosperm in sex1. Haplotype analysis suggested that hap4 in the promoter sequence was positively related to the hundred-grain weight showing a breeding potential. A pair of near-isogenic lines targeting HORVU6Hr1G037950 was produced and characterized to investigate molecular mechanisms that SEX1 regulates endosperm development. Results presented that the absence of the SEX1 gene led to the decrease of starch content and A-type granules size, the increase of β-glucan, protein, gelatinization temperature, soluble sugar content, amylopectin A chains, and B1 chains. Enzymatic activity, transcriptome and metabolome analyses revealed the loss of SEX1 results in an impaired ADP-glucose-to-starch conversion process, consequently leading to higher soluble sugar contents and lower starch accumulation, thereby inducing a shrunken-endosperm phenotype in sex1. Taken together, this study provides new insights into barley grain development, and the elevated protein and β-glucan contents of the whole meal in sex1 imply its promising application in the food industry.

Effects of Starch Molecular Structure and Physicochemical Properties on Eating Quality of Indica Rice with Similar Apparent Amylose and Protein Contents

It is important to clarify the effects of starch fine structure and protein components on the eating quality of indica rice. In this study, seven indica rice varieties with similar apparent amylose content (AAC) and protein content (PC) but different sensory taste values were selected and compared systematically. It was found that except for AAC and PC, these varieties showed significant differences in starch molecular structure and protein components. Compared with rice varieties with a low sensory taste value, varieties with a higher sensory taste value showed significantly lower amylose and higher amylopectin short chains (degree of polymerization 6-12) content; the protein component showed that the varieties with good taste value had higher albumin and lower globulin and glutelin content (p < 0.05). Rice varieties with lower AC, globulin, and glutelin content, as well as a higher content of albumin and amylopectin short chains, resulted in a higher swelling factor, peak viscosity, breakdown value, and ratio of hardness to stickiness, in which condition cooked rice showed a higher sensory taste value. Moreover, this study indicated that rice varieties with a higher content of albumin and amylopectin short chains were conducive to the good appearance of cooked rice. This study lays the foundation for the taste evaluation of good-tasting indica rice.

Digestibility, structural and physicochemical properties of microcrystalline butyrylated pea starch with different degree of substitution

In this study, microcrystalline butyrylated pea starch (MBPS) with higher contents of resistant starch (RS) was synthesized via esterification with butyric anhydride (BA) using microcrystalline pea starch (MPS) as the raw material. With the addition of BA, the new characteristic peaks appeared at 1739 cm^-1 and 0.85 ppm obtained from FTIR and ¹H NMR, respectively, and increased with the higher degree of BA substitution. Moreover, an irregular shape of MBPS, such as condensed particles and more cracks or fragments, had been observed by SEM. Further, the relative crystallinity of MPS increased then native pea starch and decreased with the reaction of esterification. MBPS had higher decomposition onset temperature (T_o) and temperature of maximum decomposition (T_max) with increasing DS values. Simultaneously, an increasing trend RS content from 63.04 % to 94.11 % and a decreasing trends in rapidly digestible starch (RDS) and slowly digestible starch (SDS) contents of MBPS were recorded with increasing DS values. MBPS samples showed higher production capacity of butyric acid ranging from 553.82 μmol/L to 892.64 μmol/L during the fermentation process. Compared with MPS, the functional properties of MBPS were significantly improved.

Cultivation pattern affects starch structure and physicochemical properties of yam (Dioscorea persimilis)

Yam (Dioscorea spp.) is a major food source in many countries due to its tuber rich in starch (60 %-89 % of the dry weight) and various important micronutrients. Orientation Supergene Cultivation (OSC) pattern is a simple and efficient cultivation mode developed in China in recent years. However, little is known about its effect on yam tuber starch. In this study, the starchy tuber yield, starch structure and physicochemical properties were compared and analyzed in detail between OSC and Traditional Vertical Cultivation (TVC) with Dioscorea persimilis "zhugaoshu", a widely cultivated variety. The results proved that OSC significantly increased tuber yield (23.76 %-31.86 %) and commodity quality (more smooth skin) compared with TVC in three consecutive years of field experiments. Moreover, OSC increased amylopectin content, resistant starch content, granule average diameter and average degree of crystallinity by 2.7 %, 5.8 %, 14.7 % and 9.5 %, respectively, while OSC decreased starch molecular weight (Mw). These traits resulted in starch with lower thermal properties (To, Tp, Tc, ΔH_gel), but higher pasting properties (PV, TV). Our results indicated that cultivation pattern affected the yam production and starch physicochemical properties. It would not only provide a practical basis for OSC promotion, but also provide valuable information on how to guide the yam starch end use in food and non-food industries.

In vitro fecal fermentation characteristics of mutant rice starch depend more on amylose content than crystalline structure

To obtain the relation between rice starch features and fermentation characteristics, rice starches with various polymorphic types and apparent amylose contents were subjected to in vitro fecal fermentation. Gas and short-chain fatty acid production was evaluated as a function of fermentation time, and the microbial responses were monitored by 16S rRNA sequencing technique at the end of fermentation. Regardless of polymorphic type, three high-amylose mutant rice starches (i.e., GM03, A-type; BP577, B-type; Wx21TT, C-type) displayed significantly slower fermentation rate during the first 12 h and higher final butyrate yield (17.6-17.9 mM) compared to the A-type normal starches (9311 and Wx22TT), and promoted the proliferation of Roseburia. However, A-type normal rice starches presented higher propionate production, and increased the growth of Bacteroides and Megamonas. The principal component and redundancy analyses indicated that three high-amylose mutant rice starches showed similar abundance and migration of microbial communities, and the apparent amylose content was closely correlated with the abundance of their five key amplicon sequence variants. Our results demonstrated that amylose content might be a controlling factor in determining the fermentation properties of rice starches than crystalline structure.

Effects of Extraction Methods on Physicochemical and Structural Properties of Common Vetch Starch

Three extraction methods: water extraction, lactic acid bacteria fermentation, and back-slopping fermentation were applied to extract a new type of legume starch, common vetch starch. Our results showed that the lactic acid bacteria fermented starch had the highest amylose content (35.69%), followed by the back-slopping fermented starch (32.34%), and the water-extracted starch (30.25%). Furthermore, erosion surface, lower molecular weight, smaller particle size, larger specific surface area, and a higher proportion of B1 chain were observed in the fermented starch, especially in the back-slopping fermented starch. All the extracted starches showed a type C structure, but a type C_B structure was observed in the back-slopping fermented starch. In addition, the relative crystallinity of the lactic acid bacteria fermented starch (34.16%) and the back-slopping fermented starch (39.43%) was significantly higher than that of the water-extracted starch (30.22%). Moreover, the swelling power, solubility, pasting, and thermal properties of the fermented starches were also improved. In conclusion, the fermentation extraction method, especially back-slopping fermentation, could improve the quality of the extracted common vetch starch when compared with the traditional water extraction method.

Changes in chemical composition and starch structure in rice noodle cultivar influence Rapid Visco analysis and texture analysis profiles under shading

•

The pasting property of rice noodles which decreased under shade stress.

•

Pasting property is related to amylose, short chain amylopectin and crystallinity of starch.

•

Protein content and swelling factor had significant correlation with the quality of rice noodle.

GuichaoII, a rice variety with high amylose content widely used to make rice noodles, exhibits high hardness (631.07–729.43), gel consistency (8.47–9.47 mm), and hold viscosity/peak viscosity (HPV/PKV) (0.85–0.88); however, it has a low protein content (5.74–6.96%) and swelling factor (5.49–9.77). Herein, GuichaoII was subjected to low-light stress (53% reduction) during the grain filling stage. The amylose content and crystallinity of GuichaoII and the control variety Shuhui 498 decreased while the protein content, short-chain branch ratio, and degree of branching increased, which affected the ability of the rice flour to absorb water and expand during the gelatinization process. The PKV, HPV, breakdown viscosity, and final viscosity were significantly reduced, while the hardness was significantly increased, and the gel consistency and the gelatinization quality of the rice were reduced, severely limiting the processing and production of rice noodles.

Relationships between X-ray Diffraction Peaks, Molecular Components, and Heat Properties of C-Type Starches from Different Sweet Potato Varieties

C-type starches with different proportions of A- and B-type crystallinities have different intensities and crystallinities of X-ray diffraction peaks. In this study, the intensities and crystallinities of X-ray diffraction peaks, molecular components and heat properties of C-type starches were investigated in seven sweet potato varieties, and their relationships were analyzed. The intensity and crystallinity of a diffraction peak at 5.6° were significantly positively correlated to the DP6-12 branch-chains of amylopectin and significantly negatively correlated to the true amylose content (TAC) determined by concanavalin A precipitation, gelatinization temperature, gelatinization enthalpy, water solubility at 95 °C, and pasting temperature. The intensity of diffraction peaks at 15° and 23° were significantly positively correlated to the gelatinization temperature and pasting temperature and significantly negatively correlated to the pasting peak viscosity. The significantly positive relationships were detected between the crystallinity of a diffraction peak at 15° and the DP13-24 branch-chains of amylopectin, gelatinization conclusion temperature and water solubility, between the crystallinity of diffraction peak at 17–18° and the TAC, gelatinization onset temperature, water solubility and pasting temperature, between the crystallinity of a diffraction peak at 23° and the gelatinization conclusion temperature and pasting peak time, and between the total crystallinity and the TAC, gelatinization conclusion temperature, water solubility and pasting temperature. The score plot of principle component analysis showed that the molecular components and heat property parameters could differentiate the C-type starches and agreed with their characteristics of X-ray diffraction peaks. This study provides some references for the utilizations of C-type starches.

The Underlying Physicochemical Properties and Starch Structures of indica Rice Grains with Translucent Endosperms under Low-Moisture Conditions

Rice grain quality is a complex trait that includes processing, appearance, eating, cooking, and nutrition components. The amylose content (AC) in the rice endosperm affects the eating and cooking quality along with the appearance of milled rice. In this study, four indica rice varieties with different ACs were used to study the factors affecting endosperm transparency along with the physical and chemical characteristics and eating quality of translucent endosperm varieties. Endosperm transparency was positively correlated with water content and negatively correlated with the cumulative area of cavities within starch granules. The indica landrace 28Zhan had a translucent endosperm and exhibited good taste. Based on starch fine structure analysis, long-chain amylopectin and the B2 chain of amylopectin might be major contributors to the good taste and relatively slow digestion of this landrace.

Resistant starch formation in rice: Genetic regulation and beyond

Resistant starch (RS), a healthy dietary fiber, is a particular type of starch that has attracted much research attention in recent years. RS has important roles in reducing glycemic index, postprandial blood glucose levels, and serum cholesterol levels, thereby improving and preventing many diseases, such as diabetes, obesity, and cardiovascular disease. The formation of RS is influenced by intrinsic properties of starch (e.g., starch granule structure, starch crystal structure, and amylose-to-amylopectin ratio) and non-starch components (e.g., proteins, lipids, and sugars), as well as storage and processing conditions. Recent studies have revealed that several starch-synthesis-related genes (SSRGs) are crucial for the formation of RS during seed development. Several transcription factors and mRNA splicing factors have been shown to affect the expression or splicing of SSRGs that regulate RS content, suggesting their potential roles in RS formation. This review focuses mainly on recent research progress on the genetic regulation of RS content and discusses the emerging genetic and molecular mechanisms of RS formation in rice.

A review of starch, a unique biopolymer - Structure, metabolism and in planta modifications

Starch is a complex carbohydrate polymer produced by plants and especially by crops in huge amounts. It consists of amylose and amylopectin, which have α-1,4- and α-1,6-linked glucose units. Despite this simple chemistry, the entire starch metabolism is complex, containing various (iso)enzymes/proteins. However, whose interplay is still not yet fully understood. Starch is essential for humans and animals as a source of nutrition and energy. Nowadays, starch is also commonly used in non-food industrial sectors for a variety of purposes. However, native starches do not always satisfy the needs of a wide range of (industrial) applications. This review summarizes the structural properties of starch, analytical methods for starch characterization, and in planta starch modifications.

Sizes, Components, Crystalline Structure, and Thermal Properties of Starches from Sweet Potato Varieties Originating from Different Countries

Sweet potato is a root tuber crop and an important starch source. There are hundreds of sweet potato varieties planted widely in the world. Starches from varieties with different genotype types and originating from different countries have not been compared for their physicochemical properties. In the research, starches from 44 sweet potato varieties originating from 15 countries but planted in the same growing conditions were investigated for their physicochemical properties to reveal the similarities and differences in varieties. The results showed that the 44 starches had granule size (D[4,3]) from 8.01 to 15.30 μm. Starches had different iodine absorption properties with OD680 from 0.259 to 0.382 and OD620/550 from 1.142 to 1.237. The 44 starches had apparent amylose content from 19.2% to 29.2% and true amylose content from 14.2% to 20.2%. The starches exhibited A-, C_A-, C_C-, or C_B-type X-ray diffraction patterns. The thermograms of 44 starches exhibited one-, two-, or three-peak curves, leading to a significantly different gelatinization temperature range from 13.1 to 29.2 °C. The significantly different starch properties divide the 44 sweet potato varieties into different groups due to their different genotype backgrounds. The research offers references for the utilization of sweet potato germplasm.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Structural and digestion properties of potato starch modified using an efficient starch branching enzyme AqGBE

Modified potato starch with slower digestion may aid the development of new starch derivatives with improved nutritional values, and strategies to increase nutritional fractions such as resistant starch (RS) are desired. In this study, a correspondence between starch structure and enzymatic resistance was provided based on the efficient branching enzyme AqGBE, and modified starches with different amylose content (Control, 100%; PS1, 90%; PS2, 72%; PS3, 32%; PS4, 18%) were prepared. Through SEM observation, NMR and X-ray diffraction analyses, we identified that an increased proportion of α-1,6-linked branches in potato starch changes its state of granule into large pieces with crystallinity. Molecular weight and chain-length distribution analysis showed a decrease of molecular weight (from 1.1 × 10⁶ to 1.1 × 10⁵ g/mol) without an obvious change of chain-length distribution in PS1, while PS2-4 exhibited an increased proportion of DP 6-12 with a stable molecular weight distribution, indicating a distinct model of structural modification by AqGBE. The enhancement of peak viscosity was related to increased hydrophobic interactions and pieces state of PS1, while the contents of SDS and RS in PS1 increased by 37.7 and 49.4%, respectively. Our result provides an alternative way to increase the RS content of potato starch by branching modification.

Formation of type 3 resistant starch from mechanical activation-damaged high-amylose maize starch by a high-solid method

This study focused on constructing a high-solid reaction system to prepare type 3 resistant starch (RS₃) with high-amylose maize starch as raw material by mechanical activation (MA) pretreatment combined with thermal and freeze-thaw treatments. MA pretreatment effectively destroyed the crystal structure and molecular structure of native starch. MA damaged starch with a certain viscosity could form dough with a small amount of water to construct a starch continuous phase system. RS content increased with the damage levels of starch as the formation of double helix structure, attributed to that the molecules of MA damaged starch could be easy to move and form recrystallization structure. Thermal and freeze-thaw treatments contributed to strong interaction of starch-water and the re-formation of internal crystal structure of MA damaged starch to form RS₃. This study provides insight into the development of a highly effective approach for large scale production of resistant starch.

Influence of physicochemical properties and starch fine structure on the eating quality of hybrid rice with similar apparent amylose content

In this study, we compared the physicochemical properties and starch structures of hybrid rice varieties with similar apparent amylose content but different taste values. In addition to the apparent amylose content, gel permeation chromatography analysis showed that the higher proportions of amylopectin short chains and relatively lower proportions of amylopectin long chains, which could lead to higher peak viscosity and breakdown value, as well as a softer and stickier texture of cooked rice, were the key factors in determining the eating quality of hybrid rice. High-performance anion-exchange chromatography analyses showed that the proportion of amylopectin short chains (degree of polymerization 6-10) and intermediate chains (degree of polymerization 13-24), which might affect the gelatinisation enthalpy and crystallinity, also contributed greatly to the eating quality of hybrid rice. Moreover, this study indicated that a greater diversity of forms and sizes of starch granules might influence the eating quality of hybrid rice.

Effects of acid hydrolysis on the evolution of starch fine molecular structures and gelatinization properties

Effects of acid hydrolysis on amylose molecular structures and their relations to starch gelatinization properties were investigated. First-order kinetics models were applied to fit the evolution curve of starch chain-length and molecular size by acid hydrolysis treatment. Results showed that a single hydrolysis phase was involved in the degradation of waxy maize starch chains, while two distinct phases existed for the degradation of maize, high amylose maize and sago starch chains. The fast hydrolysis phase involved degradation of amylose chains with DP > ~300 and amylopectin long intra-cluster branches, while amylose chains with DP < ~300 was involved in the slow hydrolysis phase. Amylose molecules with DP ~ 300 were proposed to impact starch gelatinization properties by interaction with cut-off amylopectin double helices and formation of amylose crystallites/entanglements. This study could help food industry precisely control amylose molecular structures by acid hydrolysis treatment to develop starchy foods with desirable properties.

Impact of ultrasonic treatment on rice starch and grain functional properties: A review

As a green, nonthermal, and innovative technology, ultrasonication generates acoustic cavitation in an aqueous medium, developing physical forces that affect the starch chemistry and rice grain characteristics. This review describes the current information on the effect of ultrasonication on the morphological, textural, and physicochemical properties of rice starch and grain. In a biphasic system, ultrasonication introduced fissures and cracks, which facilitated higher uptake of water and altered the rice starch characteristics impacting textural properties. In wholegrain rice, ultrasonic treatment stimulated the production of health-related metabolites, facilitated the higher uptake of micronutrient fortificants, and enhanced the palatability by softening the rice texture. This review provides insights into the future direction on the utilization of ultrasonication for the applications towards the improvement of rice functional properties.

Effect of ultrahigh pressure on structural and physicochemical properties of rice and corn starch in complexes with apple polyphenols

BACKGROUND

Ultrahigh-pressure (UHP) treatment, a non-thermal processing technology, exerts a bactericidal effect and affects food texture. How UHP treatments influence starch-polyphenol complexes has not yet been reported. Here, we studied the effects of UHP treatment on the structure of common rice starch (CRS)-apple polyphenol (AP) and common corn starch (CCS)-AP mixtures.

RESULTS

Overall, UHP treatment decreased the particle size of the CRS-AP and CCS-AP composites. Furthermore, the ΔH values of the CRS-AP and CCS-AP mixtures decreased, and the heating stability was improved after UHP treatment. X-ray diffraction indicated that the relative crystallinity of the mixtures was unaffected by UHP treatment. Fourier-transform infrared spectroscopy proved that no new absorption peaks were observed in the infrared spectra, and the order of starch-AP was decreased after UHP treatment. These results indicated that UHP treatment inhibited the retrogradation of the starch-AP mixture. Our analyses of the microstructures of CRS-AP and CCS-AP mixtures showed increased folding and more pronounced network structures under high-pressure.

CONCLUSIONS

These results provide a theoretical basis for further exploring the properties of starch-AP mixtures following UHP treatment and provide insights regarding the use of UHP treatments for food production. © 2020 Society of Chemical Industry.

Effect of structure evolution of starch in rice on the textural formation of cooked rice

The content and composition of rice kernels are closely related to the textural properties of cooked rice. In this study, the mechanistic explanations of textural changes were linked to proton mobility, leaching behavior, and the molecular features of rice components during cooking. The decreasing trend of hardness and the formation of stickiness was mainly determined by the molecular mobility of components. The molecular weight (Mw) of starch and protein in leached solids increased with the leaching at 70-100 °C. The Mw of rice kernels at different cooking temperatures and times was similar, but the molecular size and volume varied at different stages of cooking. The dismission of the crystalline structure, C1 resonance, and lamellar structures after cooking at 100 °C for 10 min indicated that the structural evolution of starch in rice kernels was time- and temperature-dependent. These results provide a promising foundation for developing strategies to control rice cooking.

Comparison of physicochemical properties of very small granule starches from endosperms of dicotyledon plants

In this study, 6 very small granule starches (VSGSs) were isolated from endosperms of dicotyledon Amaranthus cruentus, Agriophyllum squarrosum, Chenopodium quinoa, Euryale ferox, Mirabilis jalapa, and Vaccaria hispanica. Their morphologies and physicochemical properties were investigated. Most VSGSs with granule size <3 μm were spherical or polygonal, and their apparent amylose contents ranged from 19.4 to 33.1% with A. cruentus starch the lowest and E. ferox starch the highest. All VSGSs had the same A-type crystalline structure with relative crystallinities from 23.3 to 29.6%. Though 6 VSGSs had slight differences in short-range ordered structure and lamellar repeat distance, their lamellar peak intensities exhibited significant differences. The gelatinization temperatures showed significant differences among 6 VSGSs with C. quinoa starch the lowest and M. jalapa starch the highest. The 6 VSGSs had significantly different pasting viscosities with peak viscosities from 1887 to 4579 mPa s, hot viscosities from 1704 to 3479 mPa s, breakdown viscosities from 56 to 1170 mPa s, final viscosities from 2419 to 4811 mPa s, and setback viscosities from 715 to 1821 mPa s. The digestion properties of starches were significantly different among 6 VSGSs. The above results could provide some references for applications of these VSGSs.

Physicochemical properties of vitreous and floury endosperm flours in maize

Three maize cultivars with different endosperm types (flint, semiflint, and dent maize cultivars) were studied to characterize vitreous endosperm flour properties compared with those of floury endosperm flour from the same maize kernels. Vitreous endosperm flour had higher amylose and protein contents, and lower starch content, higher percentage of large starch granule, bigger mean diameter of starch granule, higher iodine capacity, higher trough viscosity and final viscosity and setback, lower swelling power, lower peak viscosity and breakdown, and higher peak time and pasting temperature than the counterpart floury endosperm flour. X-ray diffraction analysis indicated typical A-pattern for starches of vitreous and floury endosperm flours. Floury endosperm flour showed the presence of greater crystallinity and higher enthalpy change (∆Hgel) than vitreous endosperm flour for three cultivars. Retrogradation enthalpy (∆Hret) and retrogradation percentage (R) of vitreous and floury endosperm flours ranged from 6.23 to 7.92 J/g and 52.72% to 73.62%, and from 5.46 to 6.45 J/g and 45.70% to 56.58%, respectively. In conclusion, vitreous and floury endosperm flours had significantly different physicochemical properties. Results of this study provide a foundation for better and valid utilization of different endosperm section during grain processing.

The interaction between amylose and amylopectin synthesis in rice endosperm grown at high temperature

Starch is the abundant component in rice endosperm, and its microstructure determines the quality and functional properties of rice grain. It is well known that the starch fine structure is markedly influenced by high temperature during grain filling. However, it is poorly understood on the competition among starch synthesis related enzymes as well as the interaction between amylose and amylopectin biosynthesis under increased growing temperature. In this study, the non-waxy and waxy rice were planted under normal and high temperatures. Parameterizing analysis of the starch microstructure using mathematical models proved that amylose synthesis competed with the elongation of long amylopectin chains (DP＞60); Short chains of amylopectin can be used as the substrate for elongation of longer amylopectin chains; High temperature eliminated the consistency and regularity of the synthesis of amylose and amylopectin. In addition, enzyme assay proved the validity of fitting results from mathematical modeling analysis of starch.

Inhibition of starch branching enzymes in waxy rice increases the proportion of long branch-chains of amylopectin resulting in the comb-like profiles of starch granules

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.

Comparison of Physicochemical Properties of Starches from Flesh and Peel of Green Banana Fruit

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 μm, 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 °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 α-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.

Physicochemical Properties of C-Type Starch from Root Tuber of Apios fortunei in Comparison with Maize, Potato, and Pea Starches

The dry root tuber of Apios fortunei contained about 75% starch, indicating that it is an important starch resource. Starch displayed spherical, polygonal, and ellipsoidal granules with central hila. Granule sizes ranged from 3 to 30 μm with a 9.6 μm volume-weighted mean diameter. The starch had 35% apparent amylose content and exhibited CA-type crystalline structure with 25.9% relative crystallinity. The short-range ordered degree in the granule external region was approximately 0.65, and the lamellar thickness was approximately 9.6 nm. The swelling power and water solubility began to increase from 70 °C and reached 28.7 g/g and 10.8% at 95 °C. Starch had typical bimodal thermal curve in water with gelatinization temperatures from 61.8 to 83.9 °C. The 7% (w/w) starch-water slurry had peak, hot, breakdown, final, and setback viscosities of 1689, 1420, 269, 2103, and 683 mPa s, respectively. Rapidly digestible starch, slowly digestible starch, and resistant starch were 6.04%, 10.96%, and 83.00% in native starch; 83.16%, 15.23%, and 1.61% in gelatinized starch; and 78.13%, 17.88%, and 3.99% in retrograded starch, respectively. The above physicochemical properties of A. fortunei starch were compared with those of maize A-type starch, potato B-type starch, and pea C-type starch. The hierarchical cluster analysis based on starch structural and functional property parameters showed that A. fortunei and pea starches had similar physicochemical properties and were more related to maize starch than potato starch.

Effects of Different Isolation Media on Structural and Functional Properties of Starches from Root Tubers of Purple, Yellow and White Sweet Potatoes

Different-colored sweet potatoes have different contents of pigments and phenolic compounds in their root tubers, which influence the isolation of starch. It is important to justify the identification of the most suitable isolation medium of starch from different colored root tubers. In this study, starches were isolated from root tubers of purple, yellow and white sweet potatoes using four different extraction media, including H₂O, 0.5% Na₂S₂O₅, 0.2% NaOH, and both 0.5% Na₂S₂O₅ and 0.2% NaOH. Their structural and functional properties were investigated and compared among different extraction media. The results showed that the granule size, apparent amylose content, lamellar peak intensity, thermal properties, and pasting properties were different among different-colored sweet potatoes due to their different genotype backgrounds. The four extraction media had no significant effects on starch structural properties, including apparent amylose content, crystalline structure, ordered degree, and lamellar peak intensity, except that the NaOH and Na₂S₂O₅ treatment were able to increase the whiteness of purple and yellow sweet potato starches. The different extraction media had some effects on starch functional properties, including thermal properties, swelling power, water solubility, and pasting properties. The above results indicated that the H₂O was the most suitable extraction medium to simply and fast isolate starch from root tubers of different-colored sweet potatoes.