Quantitative Genetic Basis of Gelatinization Temperature of Rice

Gelatinization temperature of rice starch plays an important role in grain quality. We mapped eight loci responsible for the gelatinization parameters of rice: onset temperature (T_o), peak temperature (T_p), conclusion temperature (T_c) and enthalpy (ΔH) using a population of 242 recombinant inbred lines (RIL). Eight quantitative trait loci (QTL) were mapped onto the chromosome regions where starch‐synthesis related genes are located. The Wx gene (granule‐bound starch synthase [GBSS]), and the region of chromosome 11 played major roles in gelatinization trait determination; and other loci were starch‐branching enzyme (SBE) genes that modify the two major loci by epistasis. High‐level interactions were also detected indicating a trans mode of action of the genes. The genetic basis for these parameters was consistent with the relationship between the thermal properties and the structure of the starch granule. This information can be helpful for the improvement of starch‐producing crops, including the improvement of rice grain quality, both for food and industrial uses.     

Rapid Screening to Identify Unusual Thermal Starch Traits from Bulked Corn Kernels

Differential scanning calorimetry (DSC) is used routinely to screen for starch thermal properties. In early generations of line development, the established analysis separately evaluates starch extracted from five, single corn kernels. A thermal property trait carried by a recessive gene would appear 25% of the time; thus, if five separate kernels were evaluated, the likelihood of detecting an unusual thermal trait is high. The objective of the current work was to expedite selection by examining five kernels at a time, instead of one, hypothesizing that we would be able to detect different thermal properties in this blend. Corn lines, all from the same genetic background (ExSeed68 or Oh43), with known thermal functions (amylose‐extender, dull, sugary‐1, sugary‐2, and waxy) were blended with normal starch (control) in ratios of 0:5, 1:4, 2:3, 3:2, 4:1, and 5:0, and analyzed with DSC. The values for each ratio within a mutant type were unique (α < 0.01) for most DSC measurements, especially for gelatinization onset temperature, change in enthalpy of gelatinization, and range of gelatinization. These results support the five‐kernel method for rapidly screening large amounts of corn germplasm to identify kernels with unusual starch traits.     

Thermal Properties of Corn Starch Extraction Intermediates by Differential Scanning Calorimetry

Thermal properties of corn starch extraction intermediates from four types of corn were studied using differential scanning calorimetry. Starch at four different stages of extraction, including a standard single-kernel starch isolation procedure and three starch extraction intermediates, was isolated from mature corn kernels of B73 and Oh43 inbreds and the mutants of waxy (wx) and amylose extender (ae) in an Oh43 background. Differences in thermal properties and moisture and protein contents of starch from the extraction stages were statistically analyzed. Most thermal properties (gelatinization and retrogradation onset temperatures, gelatinization and retrogradation ranges, gelatinization and retrogradation peak temperatures, gelatinization and retrogradation enthalpies, peak height index, and percentage of retrogradation) of starches extracted at stage 3 intermediate (a procedure that did not include a final washing step) were similar to those of starch extracted by the standard single-kernel isolation procedure. Values for gelatinization peak temperature, gelatinization enthalpy, and peak height index were different between the standard and the stage 3 intermediate. The values obtained from starches extracted at stage 3, however, were consistent and predictable, suggesting that this extraction intermediate might be used in screening programs in which many starch samples are evaluated. By using the stage 3 extraction, samples could be evaluated in three rather than four days and the procedure saved ≈0.5 hr of labor time. The other two starch extraction intermediates, which excluded filtering and washing or filtering, washing, and steeping, produced starch with thermal properties generally significantly different from starch extracted by the standard single-kernel isolation procedure.     

Properties of Starches from Near‐Isogenic Wheat Lines with Different Wx Protein Deficiencies

To determine the effect of amylose content on the starch properties, the amylose content, pasting properties, swelling power, enzymatic digestibility, and thermal properties of partial and perfect waxy types along with their wild‐type parent were analyzed. As expected, amylose content decreases differently in response to the loss of each Wx gene, showing the least response to Wx‐A1a. Most of the characteristics, except the thermal properties of the amylose‐lipid complex in differential scanning calorimetry (DSC), differed significantly among the tested types. Furthermore, the breakdown, setback, and pasting temperatures from the Rapid Visco Analyser (RVA) and the enzymatic digestibility, swelling power, peak temperature, and enthalpy of starch gelatinization from DSC showed a correlation with the amylose content. The relationships between the peak viscosity from the RVA and the onset temperature of starch gelatinization determined by DSC with amylose content of the tested materials were not clear. Waxy starch, which has no amylose, showed a contrasting behavior in starch gelatinization compared with nonwaxy starches. Among the nonwaxy starches, lower setback, lower pasting temperature, higher enzyme digestibility, higher peak temperature, higher enthalpy of starch gelatinization, and higher swelling were generally associated with low amylose starches.     

Separation and Characterization of A- and B-Type Starch Granules in Wheat Endosperm

Mature wheat (Triticum aestivum L.) endosperm contains two types of starch granules: large A-type and small B-type. Two methods, microsieving or centrifugal sedimentation through aqueous solutions of sucrose, maltose, or Percoll were used to separate A- and B-type starch granules. Microsieving could not completely separate the two types of starch granules, while centrifuging through maltose and sucrose solutions gave a homogenous population for B-type starch granules only. Centrifuging through two Percoll solutions (70 and 100%, v/v) produced purified populations of both the A- and B-type starch granules. Analysis of starch granule size distribution in the purified A- and B-type granule populations and in the whole-starch granule population obtained directly from wheat endosperm confirmed that the purified A- and B-type starch granule populations represented their counterparts in mature wheat endosperm. Centrifugations through two Percoll solutions were used to purify A- and B-type starch granule populations from six wheat cultivars. The amylose concentrations and gelatinization properties of these populations were analyzed. All of the A-type starch granules contained higher amylose concentrations and had higher gelatinization enthalpies than did B-type starch granules. Although A- and B-type starch granules started to gelatinize at a similar temperature, B-type starch granules had higher gelatinization peak and completion temperatures than did A-type starch granules     

Genetic Diversity in Physical Properties of Starch from a World Collection of Amaranthus

Physical and functional properties of starches isolated from 93 noncultivated genotypes of nine Amaranthus species from a world germ plasm collection and an additional 31 cultivated Amaranthus genotypes obtained from China were tested. A wide variation was found in the properties tested among the Amaranthus species and among genotypes within the same species. When comparing starches from cultivated and noncultivated genotypes, it was generally found that amylose was lower; starch pasting profiles were more consistent with higher peak viscosity, lower breakdown, and lower setback; the gelatinization temperature was lower; and energy of enthalpy was higher. Under cool storage, the hardness of cultivated starch pastes was lower and the adhesiveness was higher. As expected, amylose content was a primary factor affecting the physical and functional properties of Amaranthus starch. Compared with reference maize, rice, and wheat starches, Amaranthus starch tended to have lower hot paste viscosity and lower cool paste viscosity; and higher gelatinization temperatures and higher energy of enthalpy. Furthermore, Amaranthus starch pastes showed less change of gel hardness and adhesiveness after cold storage. The environmental effect on the different properties of starch varied among Amaranthus species. It is suggested that Amaranthus starches can be developed for a wide range of food uses.     

Comparison of Flour Starch Properties in Half‐Sib Families of Opaque‐2 Maize (Zea mays L.) from Argentina

Since the discovery of the o2 mutation in maize, many studies have reported the characterization of the protein quality of opaque‐2 genotypes. However, few have reported the properties of their starch. The objective of this study was to characterize flour starch properties of 12 half‐sib families of opaque‐2 maize from Argentina. Chemical composition and thermal and pasting properties of whole grain flour were determined. Nonopaque genotypes were used as a control. Starch content of opaque‐2 genotypes did not show significant differences compared with nonopaque genotypes, yet amylose content was significantly lower. A high variability in pasting and thermal properties was observed in genotypes. Opaque samples showed a significantly higher peak viscosity and a lower pasting temperature compared with nonopaque samples, probably owing to larger and less compact starch granules in the floury endosperm. The higher the gelatinization enthalpy of opaque‐2 genotypes was, the lower the amylose content in relation to nonopaque varieties. Two retrogradation endotherms were observed in DSC analysis: one corresponding to amylopectin crystallization and the other to melting of amylose‐lipid complex. Both enthalpies were considered total starch retrogradation (ΔH _RT). A wide range of variation was obtained in ΔH _RT in opaque‐2 genotypes, but no significant differences between opaque and nonopaque genotypes were observed. The differences in starch properties found in this study would make it possible to identify opaque‐2 families with particular characteristics for the development of starchy food items adapted to specific processing traits.     

Physicochemical Properties of Normal and Waxy Job's Tears (Coix lachryma-jobi L.) Starch

Physicochemical properties of starches from eight coix (Coix lachrymajobi L.) accessions were investigated. There was considerable variation in most measured traits, generally corresponding to the separation into waxy and normal amylose types. The amylose contents of five normal coix ranged from 15.9 to 25.8%, and those of three waxy coix were 0.7–1.1%. Swelling power of waxy coix starches varied between 28.6 and 41.0 g/g, generally higher than waxy maize. Normal coix starches had significantly higher gelatinization peak temperature (T_p) than the normal maize, 71.9–75.5°C. The T_p of waxy coix starches was 71.1–71.4°C, similar to waxy maize. Rapid Visco-Analyser (RVA) pasting profiles of normal coix showed little variation and closely matched the normal maize starch profile. Pasting profiles of waxy coix showed more variation and had lower peak viscosities than waxy maize starch. Waxy coix starches formed very weak gels, while the gel hardness of normal coix starches was 11.4–31.1 g. Amylose content was the main factor controlling differences in starch properties of the coix starches.     

Thermal Properties of Starch from Exotic‐by‐Adapted Corn (Zea mays L.) Lines Grown in Four Environments

The effect of four growing environments (two at Ames, IA; one at Clinton, IL; and one at Columbia, MO) on the thermal properties of starch from five exotic‐by‐adapted corn inbred lines (Chis37, Cuba34, Cuba38, Dk8, Dk10) and two control lines (B73 and Mo17) were studied using differential scanning calorimetry (DSC). The variations in thermal properties within environments were similar for the exotic‐by‐adapted lines and control lines. Missouri was the warmest environment and generally produced starch with the greatest gelatinization onset temperature (T_oG), the narrowest range of gelatinization (R_G), and the greatest enthalpy of gelatinization (ΔH_G). Illinois was the coolest environment and generally resulted in starch with the lowest T_oG, widest R_G, and lowest ΔH_G. These differences were attributed to higher temperatures in Missouri during grain‐filling months either increasing the amount of longer branches of amylopectin or perfecting amylopectin crystalline structure. The Ames 1 environment produced starch with thermal properties most similar to those of Illinois, whereas the Ames 2 environment produced starch with thermal properties most similar to those of Missouri. Ames 2, located near a river bottom where temperatures tend to be warmer, likely had temperatures most similar to those found in Missouri during grain filling.     

Gelatinization Properties of Starches from Three Successive Generations of Six Exotic Corn Lines Grown in Two Locations

The objectives of this research were to evaluate the intra‐ and interpopulation variability in gelatinization properties of starches from exotic corn lines and their derivatives when grown 1) during two successive years in the same location; and 2) in both temperate and tropical environments. Six novel exotic corn lines (two 100% exotic and four 25% exotic derived from a breeding cross developed by crossing an exotic hybrid with Corn Belt lines) were selected for this research because their starches have significantly different (and potentially useful) thermal properties from those found in starch from normal Corn Belt corn. The S_n (n = 3 for 25% exotic lines and n = 1 for 100% exotic lines) generations of the six exotic lines were self‐pollinated and grown in the winter nursery in Puerto Rico. Two successive generations (S_n+1 and S_n+2) of lines selected for low onset of gelatinization temperature were self‐pollinated and grown in the same environment near Ames, IA. To evaluate the effect of environment, the S_n+2 generation also was self‐pollinated and grown in the winter nursery in Puerto Rico. Thermal properties of starches from 10 single kernels from each line were analyzed by using differential scanning calorimetry (DSC) at a ratio of 4 mg of dry starch to 8 mg of distilled water. After subsequent generations, the differences in DSC gelatinization properties between selected kernels within each progeny line narrowed, suggesting increased homogeneity of starch structural properties within each line. Unusual thermal properties were fixed in some progeny lines. Environmental factors also affected the thermal properties of starch and a significant interaction between environment and genotype was observed. These results suggest that introgression of adapted germplasm with useful genes from exotic corn would increase the available genetic variability for starch functionality and allow the development of hybrids with important value‐added traits.     

Gelatinization and Retrogradation Traits of Starches from Argentinian Maize Inbred Lines: Patterns of Correlation Among Traits

Efforts are being made to identify sources of starches with unique end-use properties, such as thermal properties, within a wide array of maize germplasm. Because redundancy may exist when evaluating these traits, it would be useful to know the pattern of correlation among traits involved to focus the expensive stage of evaluation of germplasm on traits that do not provide redundant information. The objectives of this study were to analyze the pattern of correlations between starch gelatinization and retrogradation-associated traits in a group of 12 Argentine maize inbred lines and to develop predictive models among traits when possible. Traits measured by differential scanning calorimetry included gelatinization and retrogradation properties. Pearson correlation coefficients among starch thermal properties were determined from univariate analyses, and canonical correlations were determined from multivariate analyses. Canonical correlation analyses were more sensitive in detecting associations between starch gelatinization and retrogradation parameters than univariate analyses. Multiple regression equations to estimate the change in enthalpy of starch gelatinization and retrogradation traits, especially for change in enthalpy and percentage of retrogradation, were obtained and validated with an independent data set.     

Sources of Variation for Starch Gelatinization,Pasting, and Gelation Properties in Wheat

The starch of wheat (Triticum aestivum L.) flour affects food product quality due to the temperature-dependent interactions of starch with water during gelatinization, pasting, and gelation. The objective of this study was to determine the fundamental basis of variation in gelatinization, pasting, and gelation of prime starch derived from seven different wheat cultivars: Kanto 107, which is a partial waxy mutant line, and six near-isogenic lines (NILs) differing in hardness. Complete pasting curves with extended 16-min hold at 93°C were obtained using the Rapid Visco Analyser (RVA). Apparent amylose content ranged from 17.5 to 23.5%; total amylose content ranged from 22.8 to 28.2%. Starches exhibited significant variation in onset of gelatinization. However, none of the parameters measured consistently correlated with onset or other RVA curve parameters that preceded peak paste viscosity. Peak paste viscosity varied from 190 to 323 RVA units (RVU). Higher peak, greater breakdown, lower final viscosity, negative setback, and less total setback were associated with lower apparent and total amylose contents. Each 1% reduction in apparent or total amylose content corresponded to an increase in peak viscosity of about 22 and 25 RVU, respectively, at 12% starch concentration. Of the seven U.S. cultivars, the lower amylose cultivars Penawawa and Klasic were missing the granule-bound starch synthase (GBSS; ADPglucose starch glycosyl transferase, EC 2.4.4.21) protein associated with the Waxy gene locus on chromosome 4A (Wx-B1 locus). Kanto 107 was confirmed as missing both the 7A and 4A waxy proteins (Wx-A1 and Wx-B1 loci). The hardness NIL also were shown to be null at the 4A locus. Apparent and total amylose contents of prime starch generally corresponded well to the number of GBSS proteins; although the hardness NIL tended to have somewhat higher amylose contents than did the other GBSS 4A nulls. We concluded that reduced quantity of starch amylose due to decreased GBSS profoundly affects starch gelatinization, pasting, and gelation properties.     

DETECTION AND VERIFICATION OF QUANTITATIVE TRAIT LOCI AFFECTING TOLERANCE TO LOW PHOSPHORUS IN RICE

Phosphorus (P)-deficiency in rice (Oryza sativa L.) may cause yields reductions. This research was conducted to map quantitative trait loci (QTL) for tolerance to low-P stress in a double-haploid (DH) line, and to verify these loci in another SSD9 population, which is the ninth generation of single-seed-distribution population derived from the same parents. Two populations were cultured solution at different period. By using the linkage map, QTLs for traits associated with tolerance to low-P stress were located. Results indicated that for DH population, one restricted fragment length polymorphism (RFLP) marker located on chromosome 6 was closely associated with relative root dry weight, relative shoot dry weight, and relative total dry weight. Two QTLs affected relative P uptake content. One micro-effect QTL was found to be associated with relative P utilization efficiency. For relative amounts of root exuded acid phosphatase, relative P allocation between shoot and root, relative plant P concentration, and relative shoot P concentration, one micro-effect QTL was detected for each one. Quantitative trait loci for 3 traits were detected for both DH and SSD9 populations, but the loci for each located trait were inconsistent between two populations; the reason for inconsistency in QTLs was analyzed. The main reason could be the difference in solution environment.     

Gelatinization,Pasting, and Gelling Properties of Sweetpotato and Wheat Starch Blends

Sweetpotato starch is high yielding but has very limited uses. It is possible to expand its application by blending it with other starches to obtain novel properties. In this study, functional properties of the blends of native sweetpotato starch with native, acid‐thinned, and hydroxypropylated wheat starch were studied at different ratios (75:25, 50:50, 25:75). The swelling factor, extent of amylose leaching, pasting, and gel textural properties of the blends were nonadditive of their individual components, and could be mathematically modeled by quadratic equations in relation to the ratios. Two peaks during pasting were observed for some starch mixtures studied by Rapid ViscoAnalyser (RVA). The gelatinization and retrogradation enthalpies (ΔH) of the blends were additive of their individual components and could be modeled by linear equations. All starch mixtures exhibited two peaks during differential scanning calorimetry (DSC) scan for gelatinization, but a single peak for retrograded starches. This study may provide basis for formulation of mixtures using starch from diverse sources to develop more natural starch systems with a range of physicochemical properties.     

Characterization of Thermal Traits of Starches from Argentinian Maize Inbreds: Genotypic and Crop Year Variability

Thermal properties are among the most important end‐use characteristics of starch from maize (Zea mays L.). Knowledge of the contribution of genotype and environment to the total variance for starch thermal properties is needed to aid in defining a testing strategy for selecting maize with desirable thermal starch properties. Thus, the objectives of this study were 1) to characterize the thermal properties of starches from a group of recently developed Argentine maize inbred lines, and 2) to assess the variability in starch properties attributable to genetic and crop year effects. Twelve inbred lines developed by the National Institute of Agricultural Technology (INTA) in Argentina derived from a wide array of germplasm sources were evaluated. Gelatinization and retrogradation properties were measured by differential scanning calorimetry. Enthalpy means for gelatinization were below means reported in the literature, suggesting possible energy savings when using these starches. The ratio between change in enthalpy for retrogradation and gelatinization was above the mean reported in the literature, suggesting a starch that may be useful as a dietary fiber. Significant environmental effects caused by crop year were detected. Some inbred lines, with smaller observed ranges and standard deviations across environments, may be more stable for some properties.     

Effects of Annealing and Concentration of Calcium Salts on Thermal and Rheological Properties of Maize Starch During an Ecological Nixtamalization Process

The objective of the present work was to study the effect of annealing and concentration of Ca(OH)₂ (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (T_o, T_p, and T_f) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl₂ > CaSO₄ > Ca(OH)₂ ≈ CaCO₃. This behavior was because of the dissociation of each salt or lime in water. Anions (OH⁻) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns.     

Genetic Diversity in Properties of Starch from Zimbabwean Sorghum Landraces

Starch was isolated from 95 sorghum landraces from Zimbabwe using an alkali steep and wet‐milling procedure. The physicochemical properties of sorghum starch were examined for potential use in Southern Africa. All the landraces evaluated had a normal endosperm indicated by the amylose content of the starches. Starch properties were not correlated to most of the physical grain quality traits evaluated. Grain hardness was weakly correlated to starch gel adhesiveness (r = 0.36) and amylose content (r = 0.38) (P < 0.001). The mean peak viscosity (PV) of the sorghum starches was 324 Rapid Visco Analyser units (RVU) compared with 238 RVU in a commercial corn starch sample; PV was 244–377 RVU. Some landraces had low shear‐thinning starches, implying good paste stability under hot conditions. Pasting properties were highly correlated among the sorghum starches. The starch gel hardness showed considerable variation (44–71 g) among the landraces. Gelatinization peak temperatures were 66–70°C. The thermal properties of starches were not correlated with starch swelling and pasting properties. Genotype grouping by highest and lowest values in each category would allow selection of sorghums based on a specific attribute depending on the desired end use.     

Quantitative Trait Loci for Seed Dormancy in Wild Barley (Hordeum spontaneum C. Koch)

A quantitative trait locus analysis was carried out to unravel the genetic basis of dormancy in wild barley (Hordeum spontaneum) from Israel. Two accessions, Ashkelon and Mehola, from divergent environments were crossed to produce a mapping population. A linkage map was produced from the F₂ population, and F₄ seeds were used for germination experiments. Five quantitative trait loci (QTL) were detected for dormancy across the different germination experiments. These QTL were found on chromosomes 1, 2, 5, 6 and 7. The variation explained by each QTL varied between 8 and 25%. Ashkelon alleles increased the germination except for the QTL on chromosome 5. Three out of these five QTL co-locate with QTL found earlier in cultivated barley crosses, although this does not necessarily imply that they would be the same loci. The level of dormancy is much higher in wild barley than in cultivated barley and wild barley may have alleles that have not yet been utilised in breeding for optimally dormant barley.     

Retrogradation of Maize Starch After Thermal Treatment Within and Above the Gelatinization Temperature Range

Studies of starch retrogradation have not considered the initial thermal treatment. In this article, we explore the effect of heating to temperatures within and above the gelatinization range on maize starch retrogradation. In the first experiment, 30% suspensions of waxy (wx) starch were initially heated to final temperatures ranging from 54 to 72°C and held for 20 min. On reheating in the differential scanning calorimeter immediately after cooling, the residual gelatinization endotherm peak temperature increased, the endotherm narrowed, and enthalpy decreased. Samples stored for seven days at 4°C showed additional amylopectin retrogradation endotherms. Retrogradation increased dramatically as initial holding temperature increased from 60 to 72°C. In a second experiment, wx starch was initially heated to final temperatures from 54 to 180°C and rapidly cooled, followed by immediate reheating or storage at 4°C. Maximum amylopectin retrogradation enthalpy after storage was observed for initial heating to 82°C. Above 82°C, retrogradation enthalpy decreased as initial heating temperature increased. A similar effect for ae wx starch was observed, except that retrogradation occurred more rapidly than for wx starch. These experiments show that heating to various temperatures above the range of gelatinization may profoundly affect amylopectin retrogradation, perhaps due to varying extents of residual molecular order in starch materials that are commonly presumed to be fully gelatinized. This article shows that studies of starch retrogradation should take into account the thermal history of the samples even for temperatures above the gelatinization temperature range.     

Noodle Quality as Related to Sorghum Starch Properties

Starch was extracted from 10 sorghum genotypes and physicochemical properties (amylose content and pasting, textural, and thermal properties) were evaluated. The amylose content was 24–30%. DC‐75 starch had the highest peak viscosity (380 Rapid Visco Analyser units). Gelatinization peak temperature occurred over a narrow range (67–69°C). Genotypes Kasvikisire and SV2 produced white starches. Starches from other genotypes were different shades of pink. The starch noodles prepared were, accordingly, either white or pink. Cooking enhanced the pink coloration of noodles. Cooking loss, noodle rehydration, and elasticity were evaluated. Cooking loss was low (mean 2.4%). Noodle elasticity was highly correlated with starch pasting properties of hot paste viscosity (HPV) (r = 0.81, P < 0.01) and cold paste viscosity (CPV) (r = 0.75, P < 0.01). Noodle rehydration was significantly correlated to the initial swelling temperature of starch (T_i) (r = ‐0.91, P < 0.001) and gelatinization peak temperature (T_p) (r = 0.69, P < 0.05). The findings suggest a potential area of food application for sorghum genotypes of different grain colors. Evaluation of starch properties could be a good starting point for selecting sorghum genotypes with superior noodle‐making properties.