Cereal Chem. 75(3):365-373Laboratory-isolated buckwheat (Fagopyrum esculentum) starch was compared to commercial corn and wheat starches. Buckwheat starch granules (2.9-9.3 µm) were round and polygonal with some holes and pits on the surface. Buckwheat starch had higher amylose content, waterbinding capacity, and peak viscosity, and it had lower intrinsic viscosity when compared with corn and wheat starches. Buckwheat starch also showed restricted swelling power at 85-95°C and lower solubility in water at 55-95°C and was more susceptible to acid and enzymatic attack. Gelatinization temperatures, determined by differential scanning calorimetry, were 61.1-80.1°C for buckwheat starch compared to 64.7-79.2°C and 57.1-73.5°C for corn and wheat starches, respectively. A second endotherm observed at 84.5°C was an amylose-lipid complex attributed to the internal lipids in buck-wheat starch, as evidenced by selective extraction. The retrogradation of buckwheat, corn, and wheat starch gels was examined after storage at 25, 4, and -12°C for 1-15 days. In general, buckwheat starch retrogradation was slower than that of corn and wheat starch, but it increased as storage time increased, as did that of the other starch pastes. When the values of the three storage temperatures were averaged for each storage period analyzed, buckwheat starch gels showed a lower percentage of retrogradation than did corn and wheat starch gels. Buckwheat starch also had a lower percentage of water syneresis when stored at 4°C for 3-10 days and had better stability to syneresis after three freeze-thaw cycles at -12 and 25°C.
Cereal Chem. 76(4):541-547Semolina 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 (∆H 1 ) 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 ∆H 1 . The second endothermic DSC peak indicated no increase in amylose-lipid complexation (∆H 2 ) 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.
Cereal Chem. 75(3):301-307Freeze-thaw stability of amaranth, corn, wheat, and rice starches was determined measuring the percent of syneresis by centrifugation. Thermal properties were calculated by differential scanning calorimetry (DSC). The effects of salt (NaCl at 2 and 5%) and sugars (sucrose, glucose, and fructose at 10, 20, and 30%) on the freeze-thaw stability of amaranth starch were also studied. Based on DSC and centrifugation methods, amaranth starch had better stability after freezing and thawing through four cycles than did corn, wheat, and rice starches. Amaranth starch with added salt showed similar stability as compared with a control when measured by centrifugation and showed increased stability when measured by DSC. Adding sugars to amaranth starch gels had varying results, but for the most part, they showed similar or increased stability when compared with a control.
W inter wheat (Triticum aestivum L.) production in the southern Great Plains is dominated by dual-purpose management schemes that provide a winter forage source for stocker cattle (Bos taurus L.) and grain production from the same crop. Relative emphasis on forage versus grain is highly impacted by a producer's personal preference, but factors intrinsic to a given crop season are also infl uential, such as forage availability before cattle turnout and the relative pricing of wheat versus beef. Wheat producers in the southern plains do not discriminate heavily among cultivars for dual-purpose capability, and most hard winter wheat breeding programs do not include dual-purpose adaptation as a selection criterion.A breeding-oriented emphasis is justifi ed, however, by the 40% lower rate of genetic gain observed for yield potential under dual-purpose (0.9% yr −1 ) versus grain-only (1.3% yr −1 ) production systems (Khalil et al., 2002). The yield difference between grain-only and dual-purpose systems (Winter and Thompson, 1990;Carver et al., 2001) can be attributed largely to the 4-wk earlier planting date essential to forage-biomass accumulation . Hence producers who choose a cultivar for dual-purpose production may prioritize early stand establishment with rapid canopy closure.The dual-purpose system provides an integral selection environment for the development and evaluation of experimental breeding lines (Thapa et al., 2010). Lines that reach candidate status are expected to excel in a grain-only system as well as they do in a dual-purpose system. The hard red winter (HRW) wheat cultivar 'Duster' (Reg. No. CV-1065,
Composites of polycaprolactone (PCL) and vital wheat gluten (VG) were extruded, injection-molded, and analyzed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope, and Fourier-transform infrared (FTIR). Neat PCL sample was cooled down to À70 C and heated to 150 C, where a glass transition (T g ) emerged atfollowed by a melting transition at 56.6 C. At the end of the heating cycle, a cooling cycle started, where the same sample exhibited crystallization transition at 30.1 C. VG exhibited a T g at 63.0. Data analysis of TGA showed a one-step degradation mechanism of neat PCL versus multiple steps for the composites, indicating similar molecular structure and physical properties of neat PCL unlike the composites. In nitrogen environment versus air, the degradation activation energy (E a ) of the composites has increased at higher VG levels. From the DSC and TGA data, it is apparent that some physical interaction between PCL and VG was present. The FTIR analysis verified the physical nature of this interaction as opposed to chemical interaction. Proteinase degradation activity on the extruded composites was much higher than the injectionmolded as indicated by higher weight loss in the extruded samples.
Cereal Chem. 75(3):338-345A response surface analysis using a second-order central composite design was used to study the effect of extrusion process parameters on the extrudate quality of three blends containing buckwheat flour. The extrudates were prepared as three blends. Blend 1 was a 55:40:5 (w/w) mix of light buckwheat flour, wheat flour, and nonfat dry milk (NFDM). Blend 2 was a 40:55:5 mix of light buckwheat flour, corn meal, and NFDM. Blend 3 was a 30:60:10 mix of light buckwheat flour, corn meal, and NFDM. The blends were processed in a twin-screw extruder with factorial combinations of the parameters including: process temperatures of 95-150°C, dough moisture of 15-22%, and screw speeds of 260-390 rpm. The linear components alone significantly explained most of the variation of expansion index, bulk density, water absorption, and break-ing strength. The greatest amount of variability was explained by process temperature for blend 1. Dough moisture accounted for the greatest amount of variation for blends 2 and 3. Maximum predicted expansion index values and high water absorption percentages were obtained at low dough moisture levels. Dough moisture and process temperatures were the most important factors predicting bulk density. Sensory evaluation of texture, color, flavor, and general acceptability scores of selected samples ranked blend 3 > blend 2 > blend 1. The in vitro protein digestibility values ranked blend 1 > blend 2 > blend 3. An increase of up to 9.5% units in the protein digestibility values was observed when compared to the nonextruded raw blends.
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