Thermal Characterization of Corn Starch Mutants and Textural Effects on Tortillas

Ten parent corn lines, comprised of four mutants (dull sugary2, amylose-extender sugary2, amylose-extender dull, and an amylose-extender (ae) with introgressed Guatemalan (GUAT) germplasm) and six lines with introgressed exotic germplasm backgrounds were crossed with each other to create 20 progeny crosses. The parents and progeny crosses were characterized for % resistant starch (RS), gelatinization, and retrogradation characteristics. The RS was measured from the extracted starch targeting the measurement of RS 2, which is present in ungelatinized starch, by using the Megazyme Resistant Starch kit. The RS values from the 10 parent lines varied from 18.3 % to 52.2 %, and the values from the 20 progeny crosses ranged from 16.6 to 34.0 %. Greater RS in parents was correlated to greater RS in the progeny crosses (r = 0.63, P ≤ 0.05). The Differential Scanning Calorimeter (DSC) was used to measure the gelatinization and retrogradation characteristics of the starches. Peak gelatinization temperature and change in enthalpy were positively correlated to % RS (r = 0.65 and r = 0.67, P ≤ 0.05); however, the retrogradation parameters, a measure of RS 3, did not correlate with % RS (RS 2 type). All parents, with the exception of Guat ae, and progeny crosses had % RS greater than that of commercial cornstarch (8.9%), but lower than that of a high-amylose standard (50 % apparent amylose, 40.2 % RS). The % RS and onset temperature increased with the addition of the ae gene. Tortillas are a simple food system made from whole corn that has been nixtamalized. A high-amylose, non-floury corn type with 55.2% RS, a floury corn type with 1% RS, and a 1:1 blend with 28.2% RS were used to make traditional tortillas. Whole corn was nixtamalized and ground to make masa. The masa was evaluated for pasting properties on a Rapid-Visco Analyser. The high-amylose masa slurry gelatinized only slightly, as noted by a small change in peak viscosity during the 95y C heat treatment. The floury masa had the greatest peak viscosity, whereas the blend was intermediate in value. Tortillas were evaluated by an 11-member sensory panel who evaluated the textural attributes of grittiness, moistness, chewiness, rollability, and tearability. The floury tortillas were chewier, more rollable, and grittier than the high-amylose tortillas. The blend tortillas were intermediate in most parameters. The cutting force of the high-amylose tortillas, as measured by a texture analyzer, was very low, whereas the blend and floury tortillas required more force. Chewiness was correlated to rollability (r = 0.99, P ≤ 0.05). The RS percentage was correlated to rollability (r = 0.99), and cutting force (r = 0.99). The floury and blend tortillas had a firm texture that would be expected when eating a tortilla with a filling. The high-amylose tortillas fell apart with very little force, and would not roll around a filling, making them unsuitable for this use. Although the high-amylose tortillas had increased dietary fiber in the form of RS, it had very poor textural attributes. The blend tortillas retained enough of the textural properties of the floury tortilla to make it a suitable product. Understanding the impact of RS on the gelatinization characteristics of starches and the texture of food products will help the food industry understand its impact on food processing, especially processing involving heating

Optical excitations of Si by time-dependent density-functional theory based on the exact-exchange Kohn-Sham band structure

We calculate the imaginary part of the frequency-dependent dielectric function of bulk silicon by applying time-dependent density-functional theory based on the exact-exchange (EXX) Kohn-Sham (KS) band structure and the adiabatic local-density approximation (ALDA) kernel. The position of the E2 absorption peak calculated with the EXX band structure at the independent-particle level is in excellent agreement with experiments, which demonstrates the good quality of EXX `KS quasiparticles'. The excitonic E1 peak that is missing at the independent-particle level remains absent if two-particle interaction effects are taken into account within the time-dependent LDA, demonstrating the incapability of the ALDA kernel to describe excitonic effects.Comment: 6 pages, 2 figures; contribution to "DFT 2001", Sep. 10-14, San Lorenzo de El Escorial, Spain; to be published in Int. J. Quantum. Che

Exact Kohn-Sham exchange kernel for insulators and its long-wavelength behavior

We present an exact expression for the frequency-dependent Kohn-Sham exact-exchange (EXX) kernel for periodic insulators, which can be employed for the calculation of electronic response properties within time-dependent (TD) density-functional theory. It is shown that the EXX kernel has a long-wavelength divergence behavior of the exact full exchange-correlation kernel and thus rectifies one serious shortcoming of the adiabatic local-density approximation and generalized-gradient approximations kernels. A comparison between the TDEXX and the GW-approximation-Bethe-Salpeter-equation approach is also made.Comment: two column format 6 pages + 1 figure, to be publisehd in Physical Review

Induction of high-affinity IgE receptor on lung dendritic cells during viral infection leads to mucous cell metaplasia

Respiratory viral infections are associated with an increased risk of asthma, but how acute Th1 antiviral immune responses lead to chronic inflammatory Th2 disease remains undefined. We define a novel pathway that links transient viral infection to chronic lung disease with dendritic cell (DC) expression of the high-affinity IgE receptor (FcεRIα). In a mouse model of virus-induced chronic lung disease, in which Sendai virus triggered a switch to persistent mucous cell metaplasia and airway hyperreactivity after clearance of replicating virus, we found that FceRIa−/− mice no longer developed mucous cell metaplasia. Viral infection induced IgE-independent, type I IFN receptor–dependent expression of FcεRIα on mouse lung DCs. Cross-linking DC FcεRIα resulted in the production of the T cell chemoattractant CCL28. FceRIa−/− mice had decreased CCL28 and recruitment of IL-13–producing CD4+ T cells to the lung after viral infection. Transfer of wild-type DCs to FceRIa−/− mice restored these events, whereas blockade of CCL28 inhibited mucous cell metaplasia. Therefore, lung DC expression of FcεRIα is part of the antiviral response that recruits CD4+ T cells and drives mucous cell metaplasia, thus linking antiviral responses to allergic/asthmatic Th2 responses

Exotic Corn Lines with Increased Resistant Starch and Impact on Starch Thermal Characteristics

Ten parent corn lines, including four mutants (dull sugary2, amyloseextender sugary2, amylose-extender dull, and an amylose-extender with introgressed Guatemalen germplasm [GUAT ae]) and six lines with introgressed exotic germplasm backgrounds, were crossed with each other to create 20 progeny crosses to increase resistant starch (RS) as a dietary fiber in corn starch and to provide materials for thermal evaluation. The resistant starch 2 (RS2) values from the 10 parent lines were 18.3–52.2% and the values from the 20 progeny crosses were 16.6–34.0%. The %RS2 of parents was not additive in the offspring but greater RS2 in parents was correlated to greater RS2 in the progeny crosses (r = 0.63). Differential scanning calorimetry (DSC) measured starch thermal characteristics, revealing positive correlations of peak gelatinization temperature and change in enthalpy with %RS2 (r = 0.65 and r = 0.67, P ≤ 0.05); however, % retrogradation (a measure of RS3) and retrogradation parameters did not correlate with %RS2. The %RS2 and onset temperature increased with the addition of the ae gene, likely because RS delays gelatinization

Current-Density Functional Theory of the Response of Solids

The response of an extended periodic system to a homogeneous field (of wave-vector $q=0$) cannot be obtained from a $q=0$ time-dependent density functional theory (TDDFT) calculation, because the Runge-Gross theorem does not apply. Time-dependent {\em current}-density functional theory is needed and demonstrates that one key ingredient missing from TDDFT is the macroscopic current. In the low-frequency limit, in certain cases, density polarization functional theory is recovered and a formally exact expression for the polarization functional is given.Comment: 5 pages, accepted in PR

Second harmonic generation in SiC polytypes

LMTO calculations are presented for the frequency dependent second harmonic generation (SHG) in the polytypes 2H, 4H, 6H, 15R and 3C of SiC. All independent tensor components are calculated. The spectral features and the ratios of the 333 to 311 tensorial components are studied as a function of the degree of hexagonality. The relationship to the linear optical response and the underlying band structure are investigated. SHG is suggested to be a sensitive tool for investigating the near band edge interband excitations.Comment: 12 pages, 10 figure

Role of HbA1c in the Screening of Diabetes Mellitus in a Korean Rural Community

BackgroundRecently, the measurement of glycated hemoglobin (HbA1c) was recommended as an alternative to fasting plasma glucose or oral glucose tolerance tests for diagnosing diabetes mellitus (DM). In this study, we analyzed HbA1c levels for diabetes mellitus screening in a Korean rural population.MethodsWe analyzed data from 10,111 subjects from a Korean Rural Genomic Cohort study and generated a receiver operating characteristic curve to determine an appropriate HbA1c cutoff value for diabetes.ResultsThe mean age of the subjects was 56.3±8.1 years. Fasting plasma glucose and 2-hour plasma glucose after 75 g oral glucose tolerance tests were 97.5±25.6 and 138.3±67.1 mg/dL, respectively. The mean HbA1c level of the subjects was 5.7±0.9%. There were 8,809 non-DM patients (87.1%) and 1,302 DM patients (12.9%). A positive relationship between HbA1c and plasma glucose levels and between HbA1c and 2-hour plasma glucose levels after oral glucose tolerance tests was found in a scatter plot of the data. Using Youden's index, the proper cutoff level of HbA1c for diabetes mellitus screening was 5.95% (sensitivity, 77%; specificity, 89.4%).ConclusionOur results suggest that the optimal HbA1c level for DM screening is 5.95%