Probing the Properties of Dough with Low‐Intensity Ultrasound

Ultrasonic assessments of the properties of dough have been used over the past 15–20 years to complement studies of dough properties that use other physical testing techniques. After the principles and techniques of low‐intensity ultrasound are introduced, its use as a tool for investigating the rheology and structure of dough is reviewed. One important outcome from ultrasonic assessments of dough properties is an understanding of how bubbles alter dough rheology.     

Plasticizers for Zein: Their Effect on Tensile Properties and Water Absorption of Zein Films

Cast zein films are brittle at room conditions, so plasticizers are added to make them more flexible. The tensile properties of these films are known to be affected by the relative humidity (RH) of the ambient air. However, little is known about how the plasticizers are affected by RH. Cast zein films were plasticized with either glycerol (GLY), triethylene glycol (TEG), dibutyl tartrate (DBT), levulinic acid (LA), polyethylene glycol 300 (PEG), or oleic acid (OA). Mechanical properties and moisture content (MC) of the films were measured after one week of storage at 3, 20, 50, 70, 81, and 93% RH. The relative humidity of the films' storage had a great effect on the films' tensile properties. All the films' tensile strength and Young's modulus values decreased as RH increased. Films containing DBT, TEG, LA, or PEG showed an increase in the percent elongation with increasing RH. Films containing GLY, OA, or no plasticizer did not show any increase in percent elongation as RH increased. The changes seen in tensile properties with increasing RH are because of zein's hygroscopic nature. The absorbed water will further plasticize the zein. The type of plasticizer used determined the extent of the changes seen in the tensile properties of films stored at different RH values. Depending on the plasticizers used in the film, there were large differences in the amount of water absorbed. Films increasingly absorbed water depending on the plasticizer they contained in the order GLY > TEG > LA > PEG > NONE > DBT > OA. Films containing hygroscopic plasticizers like TEG absorbed too much water at high RH and became weak, but they absorbed enough water at lower RH values to not be brittle. While films containing the more hydrophobic plasticizer DBT were brittle at intermediate RH values, they had good mechanical properties at high RH values.     

轮胎结构参数对非稳态侧偏频率特性的影响

以考虑胎体复杂变形的轮胎非稳态侧偏特性理论模型为基础，分析了轮胎结构参数对轮胎非稳态侧偏频率特性的影响，并进一步分析了轮胎结构参数对车辆摆振的影响。     

Effects of Preparation Temperature on Gelation Properties and Molecular Structure of High‐Amylose Maize Starch

In this study, 3% aqueous high‐amylose maize starch (Hylon VII) dispersions were heated to temperatures of 140–165°C. The onset and rate of gel formation was observed using a small‐strain oscillation rheometer as a function of temperature from 90 to 25°C. The gel formation clearly began earlier in high‐amylose starch paste preheated at lower temperatures, but the rate of gelation was slower and the resulting gel was weaker in comparison with starch pastes preheated at higher temperatures. In addition, the structure of the final gels was studied using large deformation compression measurements. The most rigid gel structure on the basis of small and large deformation tests was obtained for high‐amylose starch gel preheated to 150–152°C, depending on the type of measurement. The rate of gelation was also fastest in that temperature range. High‐amylose gels heated to higher temperatures lost their rigidity. The molecular weight distribution of starch molecules was measured by size‐exclusion chromatography. Heating caused extensive degradation of amylopectin, which had a great effect on amylose gel formation and the final gel properties of high‐amylose maize starch. Micrographs of Hylon VII gels showed that phase separation of starch components visible in light microscopy occurred on heating to higher temperatures.     

Effects of Protein Content,Glutenin‐to‐Gliadin Ratio,Amylose Content,and Starch Damage on Textural Properties of Chinese Fresh White Noodles

The independent effects of flour protein and starch on textural properties of Chinese fresh white noodles were investigated through reconstitution of fractionated flour components. Noodle hardness decreased with decreased protein content, whereas it unexpectedly increased as protein content decreased to a very low level (7.0%). Noodle cohesiveness, tensile strength, and breaking length increased with increased protein content. Higher glutenin‐to‐gliadin ratio resulted in harder and stronger noodles at constant protein content. Increased starch amylose content resulted in increased flour peak viscosity. When water absorption remained the same during noodle making, hardness and cohesiveness of cooked noodles also increased with increased starch amylose content, while springiness did not vary significantly. Increased starch damage of ≈5.5–10.4% effectively improved noodle hardness; however, starch damage >10.4% decreased it. Increased starch damage also enhanced noodle springiness while it decreased cohesiveness.     

Tensile Properties of Extruded Corn Protein Low‐Density Polyethylene Films

The strength of films extruded from powder blends of corn zein or corn gluten meal (CGM) with low‐density polyethylene was investigated. Tensile strength, percent elongation at break, and elastic modulus of the extruded films were measured. The tensile strength decreased from 13 MPa to ≈10.5 MPa with zein addition, while CGM addition resulted in tensile strength of ≈6 MPa. The higher the level of biological material (CGM or zein) in the films the lower the tensile properties. Films containing CGM exhibited significantly lower tensile properties than those containing zein. Extrusion processing of biological films is a step toward commercial viability.     

Effects of Micronization on Protein and Rheological Properties of Spring Wheat

This research investigated the effects of micronization, at different moisture levels, on the chemical and rheological properties of wheat. A set of tests designed to analyze protein fraction characteristics and rheological behaviors were conducted on samples from four wheat cultivars (AC Karma, AC Barrie, Glenlea, and Kanata). After being subjected to infrared radiation at three moisture levels (as‐is, 16%, and 22%), the seeds were milled to produce straight‐grade flour. The protein fractionation test revealed significant decreases (P ≤ 0.01) in both monomeric proteins (from 54% of total protein in the control to 37% in the tempered micronized sample) and soluble glutenins (9.4–2.5%). There was a strong negative correlation (r = ‐0.98) between the percentages of monomeric proteins and insoluble glutenins. Total extractable proteins of micronized samples tempered to 22% moisture decreased 43.5% when compared with nonmicronized control samples using size‐exclusion HPLC (SE‐HPLC). Micronization had a significant effect on gluten properties, as seen from a decrease in water absorption (P ≤ 0.01) and dough development time (P ≤ 0.01). Results showed that micronization at 100 ± 5°C had detrimental effects on wheat flour gluten functionality, including a decrease in protein solubility and impairment of rheological properties. These phenomena could be due to the formation of both hydrophobic and disulfide bonds in wheat during micronization.     

Land‐Use Type Effects on Soil Organic Carbon and Microbial Properties in a Semi‐arid Region of Northeast Brazil

Land‐use change is one of the most important anthropogenic environmental change drivers affecting the biodiversity and functioning of ecosystems. However, there is limited knowledge of the consequences for soil processes in many regions around the globe. The Brazilian semi‐arid ecosystem known as Caatinga has experienced the transformation from native forest into agricultural land, with heretofore unknown effects on soil processes and microbial properties. The aim of this study was to evaluate the impact of five land‐use changes (to maize and cowpea cropland, grape orchard, and cut and grazed pasture) on total organic C (TOC) and total N (TN) stocks and soil microbial properties of Ultisol from Caatinga. Soil samples (0–10 and 10–20 cm depth) were collected during the wet and dry periods. Split–split plot analysis of variance was used to test the effects of land use, soil depth, season and the interaction between land‐use and soil depth on soil microbial properties, TOC and TN stocks. Land‐use effects were more pronounced in the top soil layer than in the lower layer, while the pattern was less consistent in soil microbial properties. Land conversion from native forest to cropland may cause C losses from the soil, but conversion to pastures may even increase the potential of soils to function as C sinks. Grazed pastures showed not only high C and N stocks but also the highest soil microbial biomass and lowest respiratory quotients, all indications for elevated soil C sequestration. Thus, grazed pastures may represent a land‐use form with high ecosystem multifunctionality in Caatinga. Copyright © 2014 John Wiley & Sons, Ltd.     

Developments in the Science of Zein,Kafirin, and Gluten Protein Bioplastic Materials

Despite much research, there are very few commercial prolamin bioplastics. The major reason, apart from their high cost, is that they have inferior functional properties compared with synthetic polymer plastics. The inferior functional properties are because the prolamins are complex, each consisting of several classes and subclasses, and the functional properties of their bioplastics are greatly affected by water. Prolamin bioplastics are produced by controlled protein aggregation from a solvent or by thermoplastic processing. Recent research indicates that aggregation occurs by polypeptide self‐assembly into nanostructures. Protein secondary structure in terms of α‐helical and β‐sheet structure seems to play a key but incompletely understood role in assembly. Also, there is inadequate knowledge as to how these nanostructures further assemble and organize into the various forms of prolamin bioplastics such as films, fibers, microparticles, and scaffolds. Many methods have been investigated to improve prolamin bioplastic functionality, including better solvation of the prolamins, plasticization, physical and chemical cross‐linking, derivatization, and blending with synthetic and natural polymers, and some success has been achieved. The most promising area of commercialization is the biomedical field, in which the relative hydrophilicity, compatibility, and biodegradability of, particularly, zein and kafirin are advantageous. With regard to biomedical applications, “supramolecular design” of prolamin bioplastics through control over inter‐ and intramolecular weak interactions and disulfide/sulfhydryl interchange appears to have considerable potential.     

Molecular Structure and Some Physicochemical Properties of High‐Amylose Barley Starches

The molecular structure and some physicochemical properties of starches from two high‐amylose cultivars of barley, high‐amylose Glacier A (HAG‐A) and N (HAG‐N), were examined and compared with those of a normal cultivar, Normal Glacier (NG). The true amylose contents of HAG‐A, HAG‐N, and NG were 41.0, 33.4, and 23.0%, respectively. Iodine affinities before and after defatting of starch, and thermograms of differential scanning calorimetry, indicated that HAG‐A and HAG‐N starches had a higher proportion of amylose‐lipid complex than did NG starch. The amylopectins from HAG‐A and HAG‐N were similar to NG amylopectin in average chain length (18–19), β‐amylolysis limit (β‐AL 56–57%), number‐average degrees of polymerization (DP_n 6,000–7,500) and chain length distribution. Very long chains (1–2%) were found in amylopectins from all cultivars. HAG‐A amylopectin had a larger amount of phosphorus (214 ppm) than the others. The amyloses from HAG‐A and HAG‐N resembled NG amylose in DP_n (950–1,080) and β‐AL (70–74%). However, HAG‐A and HAG‐N had a larger number of chains per molecule (NC 2.4–2.7) than NG amylose (1.8) and contained the branched amylose with a higher NC (9.5–10.6) than that of NG amylose (5.8), although molar fractions of the branched amylose (15–20%) were similar.     

Effects of Genotype and Environment on the Starch Properties and End‐Product Quality of Oats

Five Canadian oat genotypes were grown at six environments in Manitoba to assess the effects of genotype, environment, and genotype‐by‐environment interaction on oat starch properties and end‐product quality. Genotypic variation was significant for total starch, amylose content, starch swelling volume (SSV), Rapid Visco Analyser (RVA) pasting viscosities, differential scanning calorimetry (DSC) thermal properties, and starch gel texture as well as the quality of flakes and cooked oatmeal made by laboratory‐scale methodologies. Environment was the dominant factor contributing to the total variation of starch content, RVA pasting viscosities, SSV, and DSC thermal properties. Most measurements of starch gel and oatmeal texture were not affected by growing environment. Cross‐over analysis revealed that changes in the ranking of genotypes across environments occurred for starch RVA hot paste, breakdown and shear thinning viscosities, work of gel compression, flake hydration capacity, and the proportion of large flakes, indicating that breeding for these traits would require multiple testing sites. Trends were observed between oatmeal texture and several flake and starch gel properties, warranting further study. Results of this study indicated that there is a potential to breed Canadian oat cultivars with improved functional end‐product quality for use in the milling and food manufacturing industries.     

振动频率对压实黄土动强度特性的影响

利用动扭剪三轴仪对压实黄土进行了不同振动频率下的试验研究,分析了振动频率f对压实黄土的动强度和动强度参数的影响规律.研究表明,在一定围压下,压实黄土动强度均随振动频率f的升高而增大,与振动频率呈正相关关系;在试样振动频率确定的情况下,压实黄土的动强度随围压的增加而增大;压实黄土的动黏聚力cd和动内摩擦角ψd均随着频率的增大而升高;动强度参数中cd和ψd随振次的增加均呈减小并最终趋于稳定的趋势.     

Reduction of Aflatoxin and Fumonisin Contamination in Yellow Corn by High‐Speed Dual‐Wavelength Sorting

A high‐speed dual‐wavelength sorter was tested for removing corn contaminated in the field with aflatoxin and fumonisin. To achieve accurate sorting, single kernel reflectance spectra (500–1,700 nm) were analyzed to select the optimal pair of optical filters to detect mycotoxin‐contaminated corn during high‐speed sorting. A routine, based on discriminant analysis, was developed to select the two absorbance bands in the spectra that would give the greatest classification accuracy. In a laboratory setting, and with the kernels stationary, absorbances at 750 and 1,200 nm could correctly identify >99% of the kernels as aflatoxin‐contaminated (>100 ppb) or uncontaminated. A high‐speed sorter was tested using the selected filter pair for corn samples inoculated with Aspergillus flavus; naturally infested corn grown in central Illinois; and naturally infested, commercially grown and harvested corn from eastern Kansas (2002 harvest). For the Kansas corn, the sorter was able to reduce aflatoxin levels by 81% from an initial average of 53 ppb, while fumonisin levels in the same grain samples were reduced an average of 85% from an initial level of 17 ppm. Similar reductions in mycotoxin levels were observed after high‐speed sorting of A. flavus inoculated and naturally mold‐infested corn grown in Illinois.     

Effect of Solvent and Temperature on Secondary and Tertiary Structure of Zein by Circular Dichroism

Circular dichroism studies were performed on zein to determine how the secondary and tertiary structure changes with different solvents, temperatures, or pH. Alcoholic solvent type and common denaturants such as SDS and low amounts of urea had little effect on the secondary structure of zein. Utilization of dimethylformamide or acetic acid as solvent gave changes in tertiary structure. Solutions of zein in 8M urea produced solutions with large changes in tertiary structure. The dissolution of zein in 50 mM sodium hydroxide produces a zein with large changes in secondary and tertiary structure and little loss in primary structure. Increasing the temperature of zein to 70°C in 80% ethanol-water gave reversible changes in the primary structure (20% reduction in absolute magnitude of [θ]λ at 208 and 222 nm) and tertiary structure (40% reduction in absolute magnitude of [θ]λ at 268 nm).     

Mixing‐Recording Method for the Practical Determination of Physical Properties of Soy Protein Isolate

The mixing properties of soy protein isolate (SPI) were investigated. The electric current of a kitchen food processor was monitored during the mixing of SPIs to produce dough, and an identical mixing curve was obtained for each SPI. The obtained peak time and peak height of the electric current curve were correlated to the physical properties (solubility and gel strength) of each SPI. The peak time negatively correlated with solubility, and the peak height positively correlated with gel strength. Optical microscopic observations showed that the dough microstructure appeared to be related to the peak time. Moreover, some conditions such as the SPI storage conditions and the ionic strength of the mixing buffer affected the mixing properties. This mixing‐recording method is proposed as a practical tool that could simplify the evaluation of SPI characteristics.     

Optimizing Extraction of Zein and Glutelin‐Rich Fraction During Sequential Extraction Processing of Corn

This study was conducted to improve yields and qualities of corn protein co‐products produced by the sequential extraction process (SEP), a process using ethanol to fractionate corn in producing fuel ethanol. A two‐stage extraction protocol was evaluated to recover zein and subsequently recover a glutelin‐rich fraction (GRF). After the simultaneous oil‐extraction and ethanol‐drying step of SEP, zein was extracted from the anhydrous‐ethanol‐defatted, flaked corn by using 70% (v/v) ethanol at 60°C for 1.5 hr in a shaking water bath. Zein was recovered by ultrafiltering and then drying in a vacuum‐oven. Zein yield was 65% of the available zein in the flaked corn. SDS‐PAGE band patterns of the recovered zein closely resembled that of commercial zein. After zein extraction, the GRF was extracted using 45% ethanol and 55% 0.1M NaOH at 55°C for 2 hr. The extract was concentrated by ultrafiltration and then freeze‐dried. GRF yield was ≈65% of the available protein. Freeze‐dried GRF contained 90% crude protein (db), which classified the protein as a protein isolate. As with the protein concentrate from the original SEP, the GRF isolate was highly soluble in water at pH ≥ 7, had good emulsifying and foaming properties, formed stable emulsions, and was heat‐stable.     

Effects of Germination Duration on Milling,Physicochemical, and Textural Properties of Medium‐ and Long‐Grain Rice

Germinated brown rice is popular in Asia for its increased γ‐aminobutyric acid (GABA) content and sweeter and softer texture compared with conventional brown rice. However, most studies investigated germinated rice properties on medium‐grain or aromatic rice. The objective of this study was to compare differences between a medium‐grain (Jupiter) and a long‐grain (Wells) rice under similar germination conditions on their milling, physicochemical, and textural properties over the course of germination. Rough rice was soaked in water at 25°C for 12 h and then incubated at 30–34°C for four germination durations. Wells had a higher breakage percentage and a greater weight decrease than Jupiter during germination. Wells had a significantly lower GABA content before germination and at the first two germination durations than Jupiter, but the GABA content in Wells significantly increased at the third germination duration to become significantly higher than that of Jupiter. There were no significant changes in gelatinization temperatures and pasting properties of germinated rice from both cultivars at different germination durations. The cooked rice hardness from Wells decreased at the longest germination duration, whereas Jupiter showed a more significant decrease in cooked rice stickiness from germination. The results demonstrate that the impacts of germination on physical, chemical, and textural properties of rice were affected by grain type and germination duration.     

Impact of Thiocyanate Salts on Physical,Thermal, and Rheological Properties of Zein Films

A new class of zein additives was investigated, thiocyanate salts. Ammonium, potassium, guanidine (GTC), and magnesium thiocyanate salts were added to solutions of zein in with various amounts of tri(ethylene glycol) (TEG), cast as films, and then tested to determine the impact that each salt had on properties. The presence of these salts affected solution rheology and intrinsic viscosity, demonstrating that the salts interacted with the protein. It was found that these salts acted as plasticizers, as they lowered the glass transition temperature of zein when evaluated with differential scanning calorimetry. In zein films in which TEG was present, these salts increased elongation and reduced tensile strength. However, unlike traditional plasticizers (such as TEG), when the salts were used as the only additive, elongation was not increased and tensile strength was not decreased. Of the salts tested, GTC in combination with TEG was found to increase elongation the most. The impact of salts on elongation was greatly affected by the relative humidity in which the samples were stored.     

Free Lipids in Air‐Classified High‐Protein Fractions of Hard Winter Wheat Flours and Their Effects on Breadmaking Quality

Free lipids (FL) were extracted from straight‐grade flours (SF) and the air‐classified high‐protein fractions (ACHPF) of nine hard winter wheats. The mean values of FL contents in 10 g (db) SF and ACHPF were, respectively, 92.8 and 178.5 mg for total FL, 74.1 and 141.9 mg for nonpolar lipids (NL), 12.8 and 20.9 mg for glycolipids (GL), and 4.9 and 12.0 mg for phospholipids (PL). FL compositions of SF and ACHPF showed nonsignificant differences in NL (80.7 and 81.1% of the FL) but significant differences in GL (13.9 and 12.0% of the FL) and PL (5.4 and 6.9% of the FL). Fortification of SF with ACHPF by blending to reach 13% protein content increased gluten quantity and thereby loaf volume but decreased gluten index, loaf volume regression, and crumb grain scores. NL contents showed significant relationships with dry gluten contents (r = 0.79) and gluten index (r = ‐0.83) values, indicating that high NL content in ACHPF could decrease gluten quality of fortified flours. Thus, an optimum balance should be maintained during fortification.