Physicochemical Properties of Common and Tartary Buckwheat Starch

Physicochemical properties of starch of three common (Fagopyrum esculentum) and three tartary (F. tataricum) buckwheat varieties from Shanxi Province, China, were compared. Starch color, especially b*, differed greatly between tartary (7.99–9.57) and common (1.97–2.42) buckwheat, indicating that removal of yellow pigments from tartary buckwheat flour may be problematic during starch isolation. Starch swelling volume in water of reference wheat starch (2.8% solids and 92.5°C) was 20.1 mL; for the three common buckwheat starches it was 27.4–28.0 mL; and for the three tartary buckwheat starches it was 26.5–30.8 mL. Peak gelatinization temperature (T_p) in water was 63.7°C for wheat starch, 66.3–68.8°C for common buckwheat and 68.8–70.8°C for tartary buckwheat. T_p of all samples was similarly delayed (by 4.0–4.8°C) by 1% NaCl. Enthalpy of gelatinization (ΔH) was higher for all six buckwheat starches than it was for wheat starch. However, one common buckwheat sample had significantly lower ΔH than the others. Starch pasting profiles, measured by a Rapid Visco-Analyzer, were characteristic and similar for all six buckwheat starches, and very different from the reference wheat starch. A comparison of pasting characteristics of common and tartary buckwheat starches to wheat starch indicated similar peak viscosity, higher hot paste viscosity, higher cool paste viscosity, smaller effect of NaCl on peak viscosity, and higher resistance to shear thinning. Texture profile analysis of starch gels showed significantly greater hardness for all buckwheat samples when compared to wheat starch.     

Effect of Sucrose on Glass Transition,Gelatinization, and Retrogradation of Wheat Starch

Differential scanning calorimetry (DSC) was used to study the effect of sucrose on wheat starch glass transition, gelatinization, and retrogradation. As the ratio of sucrose to starch increased from 0.25:1 to 1:1, the glass transition temperature (T_g, T_g′) and ice melting enthalpy (ΔH_ice) of wheat starch‐sucrose mixtures (with total moistures of 40–60%) were decreased to a range of −7 to −20°C and increased to a range of 29.4 to 413.4 J/g of starch, respectively, in comparison with wheat starch with no sucrose. The T_g′ of the wheat starch‐sucrose mixtures was sensitive to the amount of added sucrose, and detection was possible only under conditions of excess total moisture of >40%. The peak temperature (T_m) and enthalpy value (ΔH_G) for gelatinization of starch‐sucrose systems within the total moisture range of 40–60% were increased with increasing sucrose and were greater at lower total moisture levels. The T_g′ of the starch‐sucrose system increased during storage. In particular, the significant shift in T_g′ ranged between 15 and 18°C for a 1:1 starch‐sucrose system (total moisture 50%) after one week of storage at various temperatures (4, 32, and 40°C). At 40% total moisture, samples with sucrose stored at 4, 32, and 40°C for four weeks had higher retrogradation enthalpy (ΔH) values than a sample with no sucrose. At 50 and 60% total moisture, there were small increases in ΔH values at storage temperature of 4°C, whereas recrystallization of samples with sucrose stored at 32 and 40°C decreased. The peak temperature (T_p), peak width (δT), and enthalpy (ΔH) for the retrogradation endotherm of wheat starch‐sucrose systems (1:0.25, 1:0.5, and 1:1) at the same total moisture and storage temperature showed notable differences with the ratio of added sucrose. In addition, T_p increased at the higher storage temperature, while δT increased at the lower storage temperature. This suggests that the recrystallization of the wheat starch‐sucrose system at various storage temperatures can be interpreted in terms of δT and T_p.     

Effect of Drying Temperature on Physicochemical Properties of Starch Isolated from Pasta

Semolina from four durum wheat genotypes (cvs. Ben, Munich, Rugby, and Vic) were processed into spaghetti that was dried by low (LT), high (HT), and ultrahigh (UHT) temperature drying cycles. Starch was isolated from dried pasta and unprocessed wheat and semolina references. Pasta-drying cycles had no significant effect on the amylose content of starches. Significant increases in enzyme-resistant starch were observed in HT- and UHT-dried pasta (2.27 and 2.51%, respectively) compared with LT-dried pasta (1.68%). Differential scanning calorimetry (DSC) gelatinization characteristics of pasta starches showed a significantly narrow range (T_r), but no changes in onset and peak temperatures (T_o and T_p, respectively) and gelatinization enthalpy (ΔH₁) were observed. When compared with unprocessed reference samples (wheat and semolina), all pasta starches shifted to higher gelatinization T_o and T_p, with narrow T_r and no changes in δH₁. The second endothermic DSC peak indicated no increase in amylose-lipid complexation (δH₂) due to drying cycle. Starches isolated from LT and HT pasta exhibited lower peak viscosities than those from UHT-dried pasta. Genotypes Ben and Rugby demonstrated higher pasting temperature and lower peak and breakdown viscosities than Vic and Munich.     

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.     

Physicochemical and Thermal Characteristics of Starch Isolated from a Waxy Wheat Genotype Exhibiting Partial Expression of Wx Proteins

A unique wheat genotype carrying waxy‐type allelic composition at the Wx loci, Gunji‐1, was developed, and its starch properties were evaluated in comparison to parental waxy and wild‐type wheat varieties. Gunji‐1 was null in all three of the Wx genes but exhibited a lower level of Wx proteins than the wild‐type. Starch amylose content and cold water retention capacity were 10.1 and 70.5% for Gunji‐1, 4.2 and 76.6% for waxy, and 27.9 and 65.0% for wild‐type, respectively. No significant differences were observed in microstructure, granule size distribution, and X‐ray diffractograms of the starch granules isolated from Gunji‐1 compared with those of waxy and wild‐type wheat varieties. Starch pasting peak, breakdown, and setback viscosities and peak temperature of Gunji‐1 were intermediate between waxy and wild‐type wheat. In starch gel hardness, Gunji‐1 (1.1 N) was more similar to waxy wheat (0.5 N) than to the wild‐type variety (17.6 N). Swelling power, swelling volume, paste transmittance during storage, and gelatinization enthalpy of Gunji‐1 were lower than those of waxy wheat but greater than those of wild‐type wheat. Retrogradation of starch stored for one week at 4°C expressed with DSC endothermic enthalpy was absent in the waxy wheat variety, whereas Gunji‐1 exhibited both retrogradation of amylopectin and amylose‐lipid complex melting similar to the wild‐type parent, even though enthalpies of Gunji‐1 were much smaller than the wild‐type parent.     

Functional Characteristics of Bread Wheat (Triticum aestivum L.) Near‐Isogenic Lines Differing at the Waxy (Wx) Locus

The Waxy (Wx) gene in hexaploid wheat (Triticum aestivum L.) encodes granule‐bound starch synthase (GBSS1), which is involved in the synthesis of amylose, a mostly linear glucan polymer that makes up ∼25% of wheat starch. A null mutation of the Wx gene in each of the three genomes is associated with starch almost entirely consisting of the branched glucan polymer amylopectin (waxy starch), with corresponding changes in functionality. However, the rheological behavior of partially waxy starch remains unclear. The objective of this study was to characterize flour and baking quality in 16 near‐isogenic lines, null at the Wx locus on zero, one, two, or all three genomes, grown in four different environments. Across allelic groups, significant variations in amylose concentrations, flour paste viscosity, loaf structure and texture, dough stability, and proximate variables were observed. Because waxy wheat starch has greater water absorbance and resistance to retrogradation than normal starch, its inclusion in flour blends has been suggested as a means of improving the texture and appearance of bakery products and noodles. The results indicate that wheat encoding <3 functional homeologs of GBSS1 produces starch that has potential in the production of certain food items, such as Asian noodles. However, further research is necessary to determine the optimal amylose‐to‐amylopectin ratio to improve baking quality.     

Rapid Isolation of Sorghum and Other Cereal Starches Using Sonication

High‐intensity ultrasound (sonication) was investigated as a method to rapidly purify starch from sorghum and other cereal grains. To improve the process, buffers were optimized to solubilize sorghum proteins in combination with the sonication. Protein content and starch color were determined to evaluate the efficiency of the extraction process. Sonication times, SDS concentration, different types and concentrations of reducing agents (sodium metabisulfite, dithiothreitol, and β‐mercaptoethanol), and centrifugation speeds of the starch washing procedure were tested. Protein content of isolated sorghum starch was reduced to 0–0.14% (db) after 2 min of sonication (using any of the reducing agents tested). Sodium metabisulfite was chosen as the preferred reducing agent because of its lower toxicity and odor compared with other reducing agents tested. The optimum conditions for producing high‐purity sorghum starches (0.06% protein) were obtained using the following conditions: 2 min of sonication time with 12.5 mM sodium borate buffer, pH 10, containing 0.5% SDS (w/v) and 0.5% sodium metabisulfite (w/v) using 1,500 rpm centrifugation speed during starch washing. Starches separated by this method showed significantly less protein content and b values (yellowness) compared with starches separated by enzymatic methods or methods using NaCl solutions and protein extraction buffers with multiple washing steps, both of which take several hours to complete. Differential scanning calorimetry thermogram values for starches isolated by three different methods showed similar patterns, except that starches obtained with the enzymatic method had slightly higher values of T_o, T_p, and ΔH. Other cereal starches from whole wheat meal, wheat flour, corn, rice, and barley were also obtained rapidly using sonication.     

Gelatinization and Retrogradation Kinetics of High‐Fiber Wheat Flour Blends: A Calorimetric Approach

The impact of dietary fiber (DF) mixtures on dough thermal properties needs to be investigated when designing high‐fiber wheat bread. Effects of flour replacement at different levels (6–34%) by soluble (inuline [FN]), partially soluble (sugar beet [FX], pea cell wall [SW]), and insoluble (pea hull [EX]) DF on wheat dough thermal profiles have been investigated by simulating baking, cooling, and storage in differential scanning calorimetry (DSC) pans. In general, DF incorporation into water‐flour systems delayed endothermic transition temperatures for both gelatinization and retrogradation phenomena except for the peak temperature (T_p) of retrogradation. With some exception, the pattern of the enthalpy of amylopectin retrogradation was lower and slower (lower constant of proportion, k) over 10 days of storage in gelatinized hydrated flour‐fiber blends when compared with control without DF. FX, a partially soluble fiber, provided major effects on gelatinization (T_p decrease and ΔH increase) and retrogradation kinetics (the Avrami exponent, n, increase). Single presence of EX allowed a significant reduction in the Avrami exponent n leading to slower kinetics for amylopectin retrogradation when included in the blends.     

Starch Properties and Stability of Club and Soft White Winter Wheats from the Pacific Northwest of the United States

Based on examination of 192 club and soft white winter (SWW) wheat samples, club and SWW wheat flours showed comparable levels of starch damage and flour peak viscosity, while differing significantly in starch content. Varietal differences and growing conditions had strong influence on the characteristics of both classes of wheat flour. Club wheat flour exhibited better stability in starch content and starch damage than did SWW wheat flour. A significant correlation between starch damage and cookie diameter in both club and SWW wheat was observed (r = -0.480, P < 0.0001 for club wheat and r = -0.430, P < 0.0001 for SWW wheat). Sponge cake volume was positively correlated with starch content in both classes of wheat (r = 0.362, P < 0.01 for club wheat and r = 0.181, P < 0.05 for SWW wheat). When wheat samples were grown in one location over three years, club and SWW wheat flours had comparable starch content. However, flour and prime starch peak viscosities were significantly different in club than in SWW wheat. Club wheat flour had lower starch damage and amylose content, as measured by high-performance size-exclusion chromatography (HPSEC), than did SWW wheat flour. Crop year and varietal differences had significant effect on amylose content, starch damage, and flour and starch peak viscosities, but not on starch content, in both classes of wheat flour. When wheat samples were grown in one year over seven locations, club wheat flour was higher in starch content, lower in starch damage, and comparable in amylose to SWW wheat flour. Both flour and prime starch viscosities were significantly higher in club wheat than in SWW wheat. Varietal differences and growing location had strong influence on starch properties in both classes of wheat. Peak viscosity of the isolated starch did not correlate well with the corresponding flour, indicating that flour pasting property does not reflect the pasting property of starch. The fine structure of isoamylase-debranched amylopectins from club and SWW wheats had a similar tri-modal pattern, with maximum at ≈DP 15 and two valleys at ≈DP 20 and 45, respectively. Although wheat flour samples differed widely in their prime starch peak viscosity, no significant difference between debranching patterns was obtained. These results indicate that the fine structure of amylopectin might not be responsible for the large differences in prime starch pasting property.     

Effect of Hydroxypropylation on Retrogradation and Water Dynamics in Wheat Starch Gels Using 1H NMR

The water dynamics in gels made from native wheat starch, control (alkali‐treated) starch, and hydroxypropylated starch were studied using ¹H NMR relaxometry. Transverse relaxation studies showed that at least two domains of water exist in the starch gel, one with a T₂ of 0.5–8 msec and one with a T₂ at 8–200 msec. For starch gels held at 5°C for up to 15 days, the peak T₂ of both regions decreased with time for gels made from native starch, but not for those made from hydroxypropylated starch. Changes in integrated signal in each region suggests that water migrates out of the lower T₂ domain during retrogradation. Gels made from isolated amylose had a single, relatively mobile water domain, with T₂ dependent on gel concentration. This fraction did not change during storage at 5°C. Granule‐rich gels showed two water domains, one with a T₂ range similar to that for amylose gels, which varied over time and were thermally reversible. During storage, most significant changes occurred in the relatively low T₂ region associated with granule remnants. These studies show that, in addition to changes in starch during retrogradation, water dynamics are also affected by recrystallization and chemical modification of starch molecules.     

Relationship of Gelatinization and Recrystallization of Cross‐Linked Rice to Glass Transition Temperature

Nonwaxy rice starch was cross‐linked with sodium trimetaphosphate and sodium tripolyphosphate to obtain different degrees of cross‐linking (9.2, 26.2, and 29.2%). The objective was to investigate the influence of cross‐linking on thermal transitions of rice starch. Starch suspensions (67% moisture) were heated at 2°C/min using differential scanning calorimetry (DSC) to follow melting transition of amylopectin. Biphasic transitions were observed at ≈60–95°C in all samples. Melting endotherms of amylopectin shifted to a higher temperature (≤5°C) with an increasing degree of cross‐linking, while there was no dramatic change in enthalpy. Recrystallization during aging for 0–15 days was significantly suppressed by cross‐linking. The delayed gelatinization and retrogradation in crosslinked starch were evident due to restricted swelling and reduced hydration in starch granules. Glass transition temperature (T_g) measured from the derivative curve of heat flow was ‐3 to ‐4°C. No significant change in T_g was observed over the storage time studied.     

Chemical and Physicochemical Properties of Maize Starch After Industrial Nixtamalization

Processing conditions similar to traditional nixtamalization are now used by the industry in the production of dry maize flours (DMF). The objective of this investigation was to evaluate the effect of industrial nixtamalization on maize starch. Thus, dent maize grains were sampled from storage silos and the starch isolated (S). From the same batch of maize, DMF was obtained and the starch isolated (S‐DMF). The amylose content in the starches was quite similar (21.5–23.4%) and characteristic of a dent maize. However, nixtamalization increased the calcium content in S‐DMF. The starches investigated exhibited the typical A‐type diffraction pattern after 40 days of storage at 11–84.1% rh. However, the differential scanning calorimetry (DSC) results showed that annealing of maize starch occurred during storage at 30°C. On the other hand, industrial nixtamalization has both a melting and annealing effect on maize starch. Thus, the operative glass transition temperature (T_g), and the DSC parameters that define starch gelatinization (T_p and ΔH) showed that the proportion between crystalline and amorphous regions within the starch granule and the extent of physical damage to starch were modified by nixtamalization. As an example, T_g for S was between 60 and 62.5°C, while the S‐DMF had a T_g of 45–55°C for damaged starch and 65–70°C for annealed starch. Additionally, the extraction of the nonconstitutive starch lipids provided starches with more consistent thermal properties, particularly in the behavior of gelatinization at different water content. This last observation might have important implications in the consistency of starch physicochemical properties and, consequently, in the quality of maize products such as tortillas.     

Agronomic and Quality Performance of Progeny Lines Derived from Spring Wheat by Durum Wheat Crosses

Hard red spring wheat (Triticum aestivum L. subsp. aestivum) and durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn) have both been selected for dryland yield potential and high grain protein, although end uses of flour are different. For this study, 14 tetraploid and 10 hexaploid lines were derived from crosses between tetraploid durum wheat and hexaploid hard red spring wheat. Our objective was to determine the impact of genetic exchange between the two classes on agronomic and quality attributes of derived progeny lines. Yield potential of both the tetraploid and hexaploid progeny was lower than the parental types. Polyphenol oxidase levels were higher by almost twofold in the hexaploid group. The tetraploid progeny group had better noodle color than did the hexaploid group. Bread quality of hexaploid group was superior, with loaf volume 362 cm³ higher than that of tetraploid progeny group. In general, the presence of durum wheat genes in the derived hexaploid lines had little impact on most quality traits. The presence or absence of the D genome tended to be the major influence on end use quality traits. Our results suggest that genetic exchange between the two groups has a small effect on end use quality, but low yield potential in the progeny suggests obtaining desirable genetic combinations for plant improvement may be challenging.     

Characterization of Starch in Aegilops Species

Starch was extracted and cleaned from 99 accessions of 20 species of Aegilops and also from 200 accessions of hexaploid wheat. Amylose content was determined by iodine staining and absorbance at 535 and 620 nm. Particle‐size distribution was determined by laser scattering. The amylose content of the Aegilops accessions did not exceed the extremes found in domesticated wheat. Aegilops species, on the whole, had a lower content of small particles than the hexaploid wheats. There was no correlation between amylose content and particle‐size distribution. Some species of Aegilops may be useful sources of low‐starch B‐type granules for hexaploid wheat, if the trait can be transferred, but they are unlikely to contribute to further variation in amylose content.     

Relationship Between Physicochemical Properties of Starches and White Salted Noodle Quality in Japanese Wheat Flours

This study describes the effect of starch properties of Japanese wheat flours on the quality of white salted noodles (WSN). Starch was isolated from 24 flours of 17 Japanese cultivars and amylose content was determined along with pasting properties by Rapid Visco Analyser (RVA), thermal properties by differential scanning calorimetry (DSC), and the distribution of amylopectin chain length by high‐performance anion exchange chromatography (HPAEC). Twenty flours were used to prepare WSN. As expected, 5–6% lower amylose content was associated with good WSN quality (higher scores in softness, elasticity, and smoothness). RVA analysis indicated that the pasting temperature had the greatest influence on WSN quality, while breakdown and setback showed slight effects on WSN quality. DSC results showed that lower endothermal enthalpy (ΔH) in the amylose‐lipid complex was associated with good WSN quality. Chainlength distribution of amylopectin by HPAEC was not an important factor in relation to WSN quality.     

Evaluation of Starch Properties of Wheats Used for Chinese Yellow-Alkaline Noodles in Japan

The objective of the present research was to assess the functional properties of the starches isolated from Australian prime hard wheat (PH) and hard red winter wheat (HRW) in the United States. These wheats are favorably used in Japan for the production of Chinese yellow-alkaline noodles (YAN). Starches isolated from PH showed higher amylose content than those of noodle wheat but lower than bread wheat. Analysis of swelling power showed that PH starch had lower values than noodle wheat starches but higher values than bread wheat starches. By contrast, HRW starch showed relatively higher amylose content and lower swelling power. There were large differences in the starch pasting properties between PH and HRW. High-performance size-exclusion chromatography studies on the components leached from the starch (80°C, 20 min) showed that PH starch had a somewhat characteristic leaching profile. Its peak ratio of high molecular weight region to low molecular weight region was greater than that of HRW starch. PH starch also characterized by having lower endothermal enthalpy (ΔH) in amylose-lipid transition. The eating quality assessment for YAN revealed that PH had more elastic texture than HRW. Additional reconstitution studies showed that these quality differences could be attributable to its starch properties.     

Amylopectin Staling of Cooked Milled Rices and Properties of Amylopectin and Amylose

Starches of waxy rices that showed varietal differences in hardness testing of cooked rice after amylopectin staling and high-amylose content (AC) rices differing in gel consistency (GC) and starch gelatinization temperature (GT) were studied to determine the factors related to varietal differences in amylopectin staling of cooked rice. Intermediate- and high-GT starches showed greater amylopectin staling of gelatinized rice by hardness testing values or differential scanning calorimetry (DSC) endotherm than did low-GT starches in both waxy and nonwaxy rices. Isoamylase-debranched amylopectins of waxy rices differed in the ratio of weight-average degree of polymerization (DP_w) fractions, but these fraction ratios were not simply related to differences in amylopectin staling of cooked rice. Among high-AC rices, amylopectin from low-GT starch was confirmed to have higher iodine affinity (2.3–2.5%) than amylopectin from intermediate-GT starches (1.7–1.8%), regardless of GC. Within high-AC starch of the same GT type, soft-GC rice corresponded with more A + B₁ DP_w 16–18 and less B₃ DP_w 150–200 fractions of debranched amylopectin and low DP_w of amylose. Amylopectin of amylose extender mutant of IR36 was confirmed to have a longer chain length than ordinary rice amylopectin: the debranched amylopectin has more B₂ DP_w 47–51 fraction, less A + B₁ DP_w fraction, but no B₄ fraction with DP_w > 200. Only high-AC amylopectin had debranched fraction with DP_w >120.     

Genetic Diversity and Relationships of Wheat Landraces from Oman Investigated with SSR Markers

Little is known about genetic diversity and geographic origin of wheat landraces from Oman, an ancient area of wheat cultivation. The objectives of this study were to investigate the genetic relationships and levels of diversity of six wheat landraces collected in Oman with a set of 30 evenly distributed SSR markers. The total gene diversity, (H_T), conserved in the three durum wheat (Triticum durum desf.) landraces (H_T = 0.46) was higher than in the three bread wheat (Triticum aestivum L.) landraces (H_T = 0.37), which were similar to Turkish and Mexican bread wheat landraces calculated in previous studies. Genetic variation partitioning (G_ST) showed that variation was mainly distributed within rather than among the durum (G_ST = 0.30) and bread wheat (G_ST = 0.19) landraces. Based on modified Rogers’ distance (MRD), the durum and bread wheat landraces were distinct from each other except for a few individuals according to principal coordinate analysis (PCoA). One bread wheat landrace (Greda) was separated into two distinct sub-populations. A joint cluster analysis with other landraces of worldwide origin revealed that Omani bread wheat landraces were different from other landraces. However, two landraces from Pakistan were grouped somewhat closer to Omani landraces indicating a possible, previously unknown relationship. Implications of these results for future wheat landrace collection, evaluation and conservation are discussed.     

Thermal Properties of Starch from 62 Exotic Maize (Zea mays L.) Lines Grown in Two Locations

The variability in thermal properties among 62 S₃ lines derived from a high-yielding exotic corn (Zea mays) population, Antigua 1 (PI 484990), was evaluated by differential scanning calorimetry (DSC). The S₃ lines were grown in Puerto Rico (1990–1991) and Georgia (1994). Separate single-kernel starch extractions for five kernels (five replicates) from each line grown in each location were performed, and the starch was analyzed. The DSC values reported included gelatinization onset (T_oG), range (R_G), enthalpy (ΔH_G), and peak height index (PHI) and retrogradation onset (T_oR), range (R_R), enthalpy (ΔH_R), and percent retrogradation (%R) (an indication of the stability of gelatinized starch after storing at 4°C for 7 days). Significant differences (P < 0.05) were found among the 62 lines of Antigua 1 for T_oG, R_G, and PHI and highly significant differences (P < 0.01) were found for ΔH_G. The starches from plants grown in Georgia (1994) had significantly (P < 0.05) greater T_oG, ΔH_G, and PHI but a significantly lower R_G than those from Puerto Rico (1990–1991). These data suggest that the starch from plants grown in Georgia (1994) might have a greater degree of crystallinity than that from Puerto Rico (1990–1991). None of the retrogradation values were significantly different among starches of the 62 lines of Antigua 1 and the starches from plants grown in the two locations.     

Thermal Properties of Starch in Corn Variants Isolated After Chemical Mutagenesis of Inbred Line B73

The starch from eight ethyl methanesulfonate (EMS) treated M4 families of the corn (Zea mays L.) inbred line B73 was analyzed using differential scanning calorimetry (DSC), a Rapid Visco Analyser (RVA), a texture analyzer (TA), and scanning electron microscopy (SEM) coupled with image analysis. The eight families were chosen from 144 families previously selected for having starch with unusual DSC parameters. Apparent amylose contents of the starch from the eight families generally were lower than that of the control. According to DSC, starches from mutagenized families tended to have lower onset temperature (T₀) of gelatinization, enthalpy (ΔH) of gelatinization, and peak height index (PHI), but broader gelatinization range (R) than the B73 control. Their values for ΔH and percentage of retrograzdation (%R) were clustered around that of the control. Pasting properties from the RVA of the starches from the M4 families also were clustered around those of the control B73 starch, except for the setback values which were lower than B73 for M4 starches. Gel firmness values, as measured by TA, of all the M4 starches were generally lower than that of the B73 starch at storage treatments of one day at 25°C or seven days at 4°C. The stickiness of the gels of the M4 starches tended to be greater than that of B73 after seven days of storage at 4°C. These observations were consistent with the lower apparent amylose values for the M4 starches. SEM and image analysis data revealed no differences among the treatments in granule size and shape. Possibly, EMS treatment altered the genes, affecting internal structure of the starch granules. Starch from the mutagenized families likely had lower bonding forces among molecules and fewer long chains in the amylopectin molecules than did B73.