Steep Time Research Articles

Formation of trihalomethanes in foods and beverages

Trihalomethanes (THMs) are suspected carcinogens and reproductive toxicants commonly found in chlorinated drinking water. This study investigates THM formation during the preparation of beverages and foods using chlorinated drinking water. A total of 11 foods and 17 beverages were tested. Under the experimental conditions, each food and beverage formed THMs, primarily chloroform, although low or trace levels of brominated THMs were also detected. Tea formed the highest THM levels (e.g., chloroform levels from 3 to 67 µg l−1), followed by coffee (from 3 to 13 µg l−1), rice (9 µg l−1), soups (from 0.4 to 3.0 µg l−1), vegetables (<1 µg l−1), and baby food (<0.7 µg l−1). Chloroform formation with instant tea, used as a highly reproducible model system, increased with free chlorine concentration, decreased with higher food (tea) concentration, and was unaffected by reaction (steeping) time and bromide ion concentration. These findings indicate that chlorine-food reactions are fast, but that formation decreases as the chlorine demand of the food system increases. THMs are formed in the preparation and cooking of a wide variety of foods if free chlorine is present, and our results suggest that tea can be a significant source of exposure to THMs.

Analysis of the behaviour of a natural expansive soil under cyclic drying and wetting

Analysis of the behaviour of a natural expansive soil under cyclic drying and wetting

Enzymatic corn wet milling: engineering process and cost model

BackgroundEnzymatic corn wet milling (E-milling) is a process derived from conventional wet milling for the recovery and purification of starch and co-products using proteases to eliminate the need for sulfites and decrease the steeping time. In 2006, the total starch production in USA by conventional wet milling equaled 23 billion kilograms, including modified starches and starches used for sweeteners and ethanol production [1]. Process engineering and cost models for an E-milling process have been developed for a processing plant with a capacity of 2.54 million kg of corn per day (100,000 bu/day). These models are based on the previously published models for a traditional wet milling plant with the same capacity. The E-milling process includes grain cleaning, pretreatment, enzymatic treatment, germ separation and recovery, fiber separation and recovery, gluten separation and recovery and starch separation. Information for the development of the conventional models was obtained from a variety of technical sources including commercial wet milling companies, industry experts and equipment suppliers. Additional information for the present models was obtained from our own experience with the development of the E-milling process and trials in the laboratory and at the pilot plant scale. The models were developed using process and cost simulation software (SuperPro Designer®) and include processing information such as composition and flow rates of the various process streams, descriptions of the various unit operations and detailed breakdowns of the operating and capital cost of the facility.ResultsBased on the information from the model, we can estimate the cost of production per kilogram of starch using the input prices for corn, enzyme and other wet milling co-products. The work presented here describes the E-milling process and compares the process, the operation and costs with the conventional process.ConclusionThe E-milling process was found to be cost competitive with the conventional process during periods of high corn feedstock costs since the enzymatic process enhances the yields of the products in a corn wet milling process. This model is available upon request from the authors for educational, research and non-commercial uses.

Physicochemical characterizing of industrial and traditional nixtamalized corn flours

Commercial nixtamalized corn flours (CNCF) from three industrial plants in Mexico and traditional nixtamalized corn flour (TNCF) were used to study their particle size distribution (PSD), chemical analysis and dietary fiber analysis. The particle size of the flours were divided into five different fractions, 30, 40, 60, 80 and 100 US mesh, using a sieving machine. These were studied in relation to their peak viscosity and calcium content. The results indicated that the chemical analysis of CNCF and TNCF were found in equal amounts of protein, fat, ashes and moisture. However, the calcium content and total dietary fiber (TDF) is higher in the TNCF sample than in that of the CNCF sample. On the other hand, the PSD exhibited an unimodal distribution. The TNCF showed homogenous behavior in calcium content and peak viscosity of the various sized fractions for different steeping times (0, 1, 3 and 7 h). Nonetheless, the three CNCF were significantly different. It was concluded that the CNCF has approximately 1/3 more calcium content than that of TNCF. From a nutrimental point of view these results are very important especial in Mexico because nixtamalized products especially in tortillas is the main source of calcium for the general population. The foregoing results suggest that CNCF has to be fortified with calcium and fiber after processing or the steeping times of the process must be incremented.

Analysis of Quality Protein Changes in Nixtamalized QPM Flours as a Function of the Steeping Time

ABSTRACTThis study showed the protein changes in Quality Protein Maize (QPM H‐368C) during the traditional nixtamalization process as a function of the steeping time from 0 to 15 hr. Protein content (N × 6.25), pH, protein fractionation, reactive lysine, essential amino acids, and protein digestibility were analyzed to explain the protein quality modifications in nixtamalized corn flours (NQF). The thermoalkaline process increased significantly (P ≤ 0.05) the protein content (5.57 ± 0.86%) in NQF obtained at 3, 5, 7, 9, 11, 13, and 15 hr of steeping time compared with native corn or corn without treatment (NC). The pH values of NQF were not proportional to the steeping time and significantly different (P ≤ 0.05) between them. At 5 hr critical steeping time, the total lysine and reactive lysine content decreased severely (36 and 32%, respectively) with statistical differences (P ≤ 0.05) compared with NC. On the other hand, the tryptophan content decreased significantly (P ≤ 0.05) at steeping times of 5–15 hr (38.70 ± 6.7%) compared with NC. The changes in the lysine and tryptophan content were not proportional to the steeping time. The protein recovery in the albumin and globulin fraction diminished (P ≤ 0.05) with respect to raw corn. The protein recovery for γ‐zeins, glutelin‐like proteins, glutelins, and residue increased. A significant (P ≤ 0.05) decrease was found in the essential amino acids in NQF with 3–7 hr of steeping time compared with NC. Equally important was the reduction in protein digestibility observed in NQF steeped at long steeping times (11–15 hr) with significant (P ≤ 0.05) differences compared with NC. The protein solubility distribution along the steeping step and the essential amino acids location, specifically lysine in corn kernel, could explain partially the protein quality changes observed in this research. Finally, these results contribute to reconciling discrepancies associated with the protein quality modifications in nixtamalized corn reported previously in literature.

Cultural variations and constants in emotional reactions to sounds

In this talk I will argue that emotional reactions to sounds can be both constant and vary between different cultures. A model of sound perception that was developed by Chalmers room acoustics group, the Emotional Reaction Model (ERM) will be reviewed. The ERM predicts that emotional reactions to auditory events can be both elicited by 1) certain form features (eg. a steep rise time, a loud sound, a rough sound) and 2) content features (eg. the qualitative experience of the sound source; the loud, rough sound is a tiger roaring). The influence of form features are expected to be rather constant across people and cultures, while content features are expected to vary more between people. Empirical evidence supporting these predicitions will be reviewed and the implications for our understanding sound perception will be discussed.

Differential Mobility Separation of Ions Using a Rectangular Asymmetric Waveform

The performance of a planar differential mobility spectrometer (DMS) is investigated when operated in air at ambient pressure and driven by a rectangular asymmetric waveform, limited to frequencies of <1.2 MHz and voltage pulse amplitudes of <1 kV with steep rise times of the order of approximately 15 ns. Independent control of frequency, voltage pulse amplitude, and duty cycle allow for characterizing the DMS in terms of transmission, resolution and separation. The tradeoff between sensitivity and resolution and the effect of duty cycle on instrument performance are demonstrated experimentally. The dependence of ion mobility on the magnitude of the electric field determines the displacement of ions measured by the DC compensation voltage as a function of the duty cycle. Optimum values for the duty cycle exist for the separation of A- and C-type ions, while, B-type ions exhibit a more complex behavior. An analytical expression for describing the effect of duty cycle on the separation of the ions, determined by variations in the compensation voltage, is developed and compared to experimental results obtained in air below 75 Td using estimated alpha parameters for a set of ketones. In this context, errors associated with the calculation of alpha parameters using polynomials of even powers are highlighted.

Thermoresponsive Characteristics of Fluoroalkyl End-Capped Co-oligomers in Aqueous Solutions and on the Poly(methyl methacrylate) Film Surface

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide--acryloylmorpholine co-oligomers were prepared by the co-oligomerizations of fluoroalkanoyl peroxides with the corresponding monomers. These fluorinated co-oligomers exhibited a lower critical solution temperature (LCST) characteristic in aqueous solutions. Of particular interest, a steep time dependence of contact angle values for dodecane was observed from 40 to 60 degrees C to decrease their values, effectively, on the modified PMMA [poly(methyl methacrylate)] film surface treated with fluorinated co-oligomer possessing the LCST: 36 degrees C (in water), although such a steep time dependence was not observed from 20 to 30 degrees C.

Effects of the microstructure of pretreated aluminum joints AA2024 [formula omitted] on the ultrasonic evaluation of adhesion

This paper is concerned with the ultrasonic characterization of the adhesion in a structural bond subjected to various surface pretreatments. The aim is: (a) to know if the non destructive evaluation allows to distinguish three types of pretreatments and (b) to optimize the procedure (e.g. time of steeping, concentration of the solution, temperature) for a given surface treatment in order to obtain a better durability of structural joints. This distinction is based on the measurement of the cutoff-frequencies of the guided waves. The comparison with two rheological models leads to a classification of the pretreatments according to their effectiveness.

Clearcut: a fast implementation of relaxed neighbor joining

Clearcut is an open source implementation for the relaxed neighbor joining (RNJ) algorithm. While traditional neighbor joining (NJ) remains a popular method for distance-based phylogenetic tree reconstruction, it suffers from a O(N(3)) time complexity, where N represents the number of taxa in the input. Due to this steep asymptotic time complexity, NJ cannot reasonably handle very large datasets. In contrast, RNJ realizes a typical-case time complexity on the order of N(2)logN without any significant qualitative difference in output. RNJ is particularly useful when inferring a very large tree or a large number of trees. In addition, RNJ retains the desirable property that it will always reconstruct the true tree given a matrix of additive pairwise distances. Clearcut implements RNJ as a C program, which takes either a set of aligned sequences or a pre-computed distance matrix as input and produces a phylogenetic tree. Alternatively, Clearcut can reconstruct phylogenies using an extremely fast standard NJ implementation. Clearcut source code is available for download at: http://bioinformatics.hungry.com/clearcut

Application of Protease and High‐Intensity Ultrasound in Corn Starch Isolation from Degermed Corn Flour

ABSTRACTThe conventional corn wet‐milling process requires a long steeping time and has environmental and health concerns from the use of SO2. A recently proposed two‐stage enzymatic milling procedure with the first stage of water soaking and coarse grinding of corn and the second stage of incubating with enzymes has been shown to reduce the soaking time and possibly eliminate the need for SO2 addition. This current work explored the applications of protease and high‐intensity ultrasound in the second stage of the two‐stage enzymatic milling for corn starch isolation to further shorten the process time without use SO2. of The starch yield from sonication alone was 55.2–67.8% (starch db) as compared with 53.4% of the water‐only control with stirring for 1 hr and 71.1% of the conventional control with SO2 and lactic acid steeping for 48 hr. Protease digestion alone for 2 hr was not effective (45.8–63.9% yield) in isolating corn starch, but the starch recovery was increased to 61.2–76.1% when protease was combined with sonication. The preferred combination was neutral protease digestion for 2 hr followed by sonication at 75% amplitude for 30 min. The results demonstrated that combinations of high‐intensity ultrasound and neutral protease could replace SO2 and shorten the steeping time in the enzymatic wet‐milling process for corn starch isolation.

RETRACTED: Evaluation of physicochemical changes in nixtamalized maize flours as a function of steeping time

The physicochemical properties of nixtamalized corn flours for different steeping times were studied, evaluating the particle size distribution (PSD), calcium concentration, viscosity, and crystallinity. Nixtamalized maize kernels with different steeping times were milled, dehydrated, and pulverized, which resulted in a variation in the particle size of the corresponding flours. The PSD was separated into two groups according to their percentage share in the flours: Group I (40, 60 and 80 US mesh), and Group II (30 and 100 US mesh). The calcium content increased in a nonlinear way as a function of increases in the steeping time. The greatest values were for the 100 US particle size. The maximum viscosity of the flours increased with steeping time and with diminishing particle size, for particle size greater than 30 US. The crystallinity of our samples varied from 9% to 14%, as a function of steeping time and calcium concentration. For the samples with steeping times of 8 and 9 h, the crystallinity behavior is similar: between 9% and 10.7%, respectively. The results obtained indicate that steeping time significantly improves the physicochemical properties of nixtamalized maize flours, as well as the quality of the final product. 2005 Elsevier Ltd. All rights reserved.

The influence of the steeping time on the antioxidant properties of a chinese herbal tea

The different methods of making herbal tea used in various cultures may decrease the efficiency of herbal tea, therefore the purpose of the present study was to examine the changes in antioxidant activity and metal ion concentration in aqueous extracts of “Tieguanyin Stomach Tea” obtained with different steeping times. Partial phytochemical examination, element analysis, and the determination of antioxidant properties were carried out. High Al, Cr, Mn, Ni, Pb and Ti content was observed in the tea drug. Aqueous extracts of the drug sample showed H-donor activity, reducing power and scavenging activity, depending on the steeping time and concentration. According to our findings, 5-min steeping was the least effective and redox parameters of the aqueous extracts did not change considerably between 15 and 120 min of steeping time.

Molecular structure and ion exchange of amidoximated cellulosic materials

Modification of lignocellulosic materials, e.g., cotton stalks, bagasse, and rice straw, by incorporation of amidoxime group for ion exchange is investigated. The uptake of metal ions Cu, Cr, Ni, and Fe by these modified lignocellulosic materials is measured. Amidoximated bagasse has higher efficiency toward metal ions uptake than amidoximated cotton and rice straw. The effect of different variables, e.g., metal ion concentration, temperature of metal ion solution, and time of steeping, on the efficiency of the amidoximated (bagasse raw material, unbleached bagasse, and bleached bagasse) ion exchangers toward metal ions uptake is tested. The molecular structure of the prepared amidoxime from bagasse and its pulps is studied by using infrared spectroscopy. New bands appeared at 1661 and 916 cm−1 in the spectra of amidoximated bagasse and its pulps ion exchangers due to the formation of CN and NOH groups. The thermal properties of these ion exchangers is also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 303–311, 2006

Effect of ground corn steeping on starch properties

Pasting and thermal properties, and microstructure of starch from ground corn (GS) steeped at 52 °C in sulphurous acid solution (0.20%) at different steep times (8, 16, 24, 32 and 40 h) were investigated. The isolated starch obtained by wet milling was characterised by determining pasting properties in Rapid Visco Analyser (RVA), retrogradation enthalpy in differential scanning calorimetry (DSC), and microstructure of granules in light (LM) and scanning electron microscopy (SEM). Milling before steeping and long steep time caused reduction in peak, hot paste, cool paste, breakdown and setback viscosities. Steep time provoked an increase in the retrogradation temperatures (onset and peak), whereas no significant differences were found in retrogradation enthalpy. Microstructure characteristics analysed by SEM showed many cracks and cavities on surface in samples steeped 8 h, whereas samples steeped 40 h showed a great alteration and disruption of their inner layer. LM with polarised light confirmed that starches retained birefringence with several differences depending on the steep time. The use of ground kernels allowed a better steep solution-endosperm interaction, which caused changes in rheological, thermal and microstructural starch characteristics.

Effects of interfacial layers in InGaN∕GaN quantum-well structures on their optical and nanostructural properties

We compared the optical properties and material nanostructures between several InGaN∕GaN multiple quantum-well (QW) samples of different interfacial layers. In some of the samples, InN interfacial layers were inserted between the wells and barriers to improve the QW quality and hence the light-emission efficiency. Compared with a widely used barrier-doped QW structure, the insertions of the InN interfacial layers (silicon doped or undoped) do enhance the photon emission efficiencies. Of the two samples with InN interfacial layers, the one with intrinsic InN interfacial layers had the higher photoluminescence (PL) and electroluminescence (EL) efficiencies. Cluster structures are clearly observed in this sample, resulting in strong carrier localization. In this sample, we also observed a temperature-dependent S-shape variation in the PL spectral peak, a strong photoluminescence excitation (PLE) intensity, and a steep PL decay time variation beyond its peak as a function of temperature. On the other hand, both carrier localization and quantum-confined Stark effect (QCSE) were relatively weaker in another sample, which includes silicon-doped InN interfacial layers. The broadening of the InGaN well layers, in one sample, by inserting silicon-doped InGaN interfacial layers led to the sharpest cluster structures and the strongest carrier localization among the four samples. Therefore, in this sample we observed quite high PL and EL efficiencies, increasing EL spectral peak energy with temperature, a strong PLE intensity, and a steep PL decay time variation beyond its peak in temperature dependence. Compared with the aforementioned samples, the widely used QW structure (the reference sample) shows the lowest PL and EL emission efficiencies, the smallest PL and EL emission photon energies, and the generally longest PL decay times. This suggests that the QCSE is the strongest in this sample.

The Effect of Steeping Time on the Final Malt Quality of Buckwheat

To determine the effect of steeping time on final buckwheat malt quality, buckwheat was steeped for three different times resulting in three different out-of-steep moisture contents: 7 h steeping (35%), 13 h steeping (40%) and 80 h steeping (45%). An increased steeping time increased malting losses, total beta-amylase activity and Kolbach index. On the contrary total nitrogen, friability and viscosity of consequent congress worts were decreased. A maximum alpha-amylase activity was found in buckwheat malted with an out-of-steep moisture content of 45%. Beta-amylase existed in a soluble and latent form in buckwheat. The latent form was solubilised during malting. In addition extra beta-amylase was produced. In general the optimum out-of-steep moisture content for buckwheat is between 35 to 40%, which is a compromise between attaining the desired malt quality and minimising malting loss.

Effect of Protease Addition on Starch Recovery from Steeped Sorghum and Maize

AbstractThe effect of protease addition on starch recovery from steeped white regular sorghum (RSOR) compared to yellow maize (YMZ) was determined. An in vitro wet milling method standardized to test dosages from 0 to 1.5 Anson units (AU/100 g grain) indicated that starch yields increased proportionally as enzyme concentration increased. The yields were significantly lower for RSOR. A factorial experiment with a level of confidence of P &lt; 0.05 was performed to study the effect of protease addition (1.25 AU/100 g grain) to coarsely ground kernels for 4 h after 20 h or 44 h SO2 steeping of whole grains. Calcium oxide (CaO) was used to increase the pH of the steep solution to 5.5 and improve enzyme activity. The in vitro and laboratory tests indicated that the enzyme treatment significantly improved starch yields and recoveries; the effect being more pronounced in RSOR. Protease‐treated kernels yielded 3.2% more starch than those steeped regularly. RSOR steeped for 20 h and then treated with the enzyme for 4 h yielded 6.7% more starch than the counterparts steeped regularly. When steep times were compared, kernels soaked regularly for 48 h produced 1.6% more starch than counterparts steeped for 24 h. The protease treatment reduced the amount of inseparables (gluten‐starch complexes) to zero and also lowered the gluten content of starch by about 1.5%. A comparison of protein and ash contents for the refined starches indicated that the process was more efficient for YMZ than for RSOR and for grains steeped regularly for 48 h. YMZ starch started gelatinization at a lower temperature, required less time to reach peak viscosity and had less shear thinning than RSOR.

A Study on the Corrosion Fatigue Characteristics of Al 2024-T3 Alloy

In order to investigate how the corrosion dramatically reduces fatigue resistance of a 2024-T3 aluminium alloy, a series of corrosion experiments in a 3.5 wt% NaCl solution with different steeping time, and subsequent fatigue experiments under uniaxial cyclic load have been performed with the laminate specimens. The nucleation and growth of corrosion pits are found to occur mainly at the grain boundary. The optical micrographs of the experiments show that the fatigue micro-crack initiates on the bottom of the pit, expands its way through the neighbouring pits that located at the slip direction and then forms a main fatigue crack that leads to fracture. The similar corrosion experiments are also performed at different solution temperatures: 22 °C, 40°C, 60°C, and 80°C respectively. The effects of the steeping time and solution temperature on the fatigue life are investigated.

Effect of Steeping Corn with Lactic Acid on Starch Properties

ABSTRACTPasting and thermal properties of starch from corn steeped in the presence of lactic acid and at different steeping times (8, 16, 24, 32, and 40 hr) were investigated. Corn kernels were steeped at 52°C with 0.2% (w/v) SO2 and with and without 0.5% (v/v) lactic acid. The isolated starch obtained by corn wet‐milling was characterized by determining starch recoveries, retrogradation, and melting transition properties of the lipid‐amylose complex by differential scanning calorimetry (DSC), and pasting properties by the Rapid Visco Analyser (RVA). Damaged granules and the starch granule size were determined by using microscopic techniques. Starches from corn steeped in the presence of lactic acid (LAS) were compared with control starch (CS) steeped without lactic acid. Greater starch recoveries were obtained for LAS samples than for CS samples, and practically no damaged starch was present in the former preparations. The presence of lactic acid affected the RVA profiles and steeping time affected the viscosities of the starch suspensions. In general, the RVA parameters of LAS suspensions were lower than those of CS suspensions. No great modification of the thermal properties was observed; only a slight decrease in amylopectin retrogradation and in the melting enthalpy of the amylose‐lipid complex was observed. Hydrolysis of the starch during steeping seems the most probable explanation to the starch modifications produced by lactic acid addition.