scholarly journals Comparative Analysis of Quality Criteria for the Control of Liquefaction at the Obtaining of Starch-Based Hydrolysates

2012 ◽  
Vol 69 (2) ◽  
Author(s):  
Monica MIRONESCU ◽  
Ion Dan MIRONESCU ◽  
Maria Iasmina MOZA ◽  
Adrian TRIFAN ◽  
Vionela MIRONESCU
Keyword(s):  
Comparative Analysis ◽  
Yield Stress ◽  
Chromatographic Method ◽  
Potato Starch ◽  
Flow Behavior ◽  
Quality Criteria ◽  
Strong Relationship ◽  
Dextrose Equivalent ◽  
Rheological Method ◽  
Liquefaction Process

Starch hydrolysates production converts starch to different kinds of products using enzymes in two steps, liquefaction and saccharification. This study investigated three types of analysis methods for the assessing and characterization of the liquefaction process: a rheological method (to measure yield stress), a chemical method (for the determination of Dextrose Equivalent DE) and a chromatographic method (HPLC to obtain the Degrees of Polymerization DPs).  Potato starch with 13.5% dry substance was liquefied with the enzyme Liquozyme Supra for two hours in optimal conditions of pH and temperature. A comparative analysis between the methods to describe the liquefaction process was realised. Yield stress offered valuable information on the flow behavior of the samples showing that after 15 minutes of liquefaction the product behaves as a fluid without yield point, with a decreasing value of the middle yield stress. DE had an ascending value during liquefaction indicating that the total reducing sugars are increasing in time. After two hours of liquefaction, glucose (DP1) in very small amounts (around 1%), maltotriose (DP3) and maltotetrose (DP4) in much higher amounts were obtained; no maltose was produced. The quantity of DP3 and DP4 was increasing with the liquefaction time whereas the content in oligosaccharides with DP 5 or higher as 5 (DP5+) was decreasing. The comparative analysis of the chemical and the chromatographic method showed that both methods characterize very well the liquefaction process. It was found that there was a strong relationship between the DE values and the total DP3+DP4 as measured from HPLC and also between DE and DP5+. 

Comparative analysis of polysaccharide properties and their effect on oxidative stability of food emulsions

2021 ◽  
pp. 50-53
Author(s):  
Варужан Амбарцумович Саркисян ◽  
Юлия Владимировна Фролова ◽  
Роман Владимирович Соболев ◽  
Алла Алексеевна Кочеткова
Keyword(s):  
Differential Scanning Calorimetry ◽  
Comparative Analysis ◽  
Oxidative Stability ◽  
Potato Starch ◽  
Locust Bean Gum ◽  
Scanning Calorimetry ◽  
Multivariate Statistical ◽  
Food Ingredients ◽  
Food Emulsions ◽  
Locust Bean

Полисахариды являются многофункциональными пищевыми ингредиентами, применяемыми в различных типах пищевых продуктов. Особый интерес вызывает изучение роли полисахаридов в качестве потенциальных про- или антиоксидантов в составе пищевых эмульсий. Основным недостатком традиционных способов оценки развития окислительных процессов в эмульсиях является необходимость предварительной экстракции жировой фазы, что может сопровождаться искажением реальных значений показателей окисления. В данной работе влияние полисахаридов на окислительную стабильность эмульсий изучено при помощи реактора окислительной устойчивости Oxitest, который позволяет проводить прямое измерение потребления кислорода в процессе окисления липидов, тем самым исключая необходимость экстракции и повышая достоверность полученных данных. Проведен сравнительный анализ 6 различных полисахаридов (альгинат натрия, i-каррагинан, камедь рожкового дерева, пектин амидированный, пектин высокоэтерифицированный, картофельный крахмал) в составе пищевых эмульсий. Методами ИК-Фурье спектроскопии и дифференциально-сканирующей калориметрии охарактеризованы состав и свойства исходных полисахаридов. Изучена вязкость 0,5%-ных растворов полисахаридов при помощи метода ротационной вискозиметрии. В результате проведенного анализа полисахаридов выявлены и охарактеризованы основные отличия в колебательных спектрах поглощения функциональных групп. Методом дифференциально-сканирующей калориметрии определены энтальпии теплового эффекта отделения влаги и начала термической деградации полисахаридов. Проведен многомерный статистический анализ полученных данных, выявивший основные закономерности между структурой и свойствами полисахаридов в составе эмульсий. Наибольшую окислительную стабильность проявили эмульсии на основе камеди рожкового дерева и амидированного пектина. Polysaccharides are multifunctional food ingredients used in various types of food products. The role of polysaccharides as potential pro- or antioxidants in food emulsions is of particular interest is. The main drawback of traditional methods for assessing the development of oxidative processes in emulsions is the need for preliminary extraction of the fat phase, which may be accompanied by a distortion of the real values of oxidation indices. In this work, the effect of polysaccharides on the oxidative stability of emulsions was studied using the Oxitest oxidative stability reactor, which allows the direct measurement of oxygen consumption during lipid oxidation, thereby eliminating the need for extraction and increasing the reliability of the obtained data. Comparative analysis of 6 different polysaccharides (sodium alginate, i-carrageenan, locust bean gum, amidated pectin, highly esterified pectin, potato starch) in food emulsions was performed. The composition and properties of the initial polysaccharides were characterized by FTIR spectroscopy and differential scanning calorimetry methods. The viscosity of 0.5% solutions of polysaccharides was studied using the rotary viscometry method. The analysis of polysaccharides revealed and characterized the main differences in the vibrational absorption spectra of functional groups. The enthalpies of the thermal effect of moisture separation and the beginning of thermal degradation of polysaccharides were determined by differential scanning calorimetry. A multivariate statistical analysis of the obtained data revealed the main relations between the structure and properties of polysaccharides in emulsions. Emulsions based on locust bean gum and amidized pectin exhibited the highest oxidative stability.

Diversity recognition and minority representation in Central and Southeast Europe: a comparative analysis

2014 ◽  
Vol 42 (3) ◽  
pp. 426-448 ◽  
Author(s):  
István Gergőo Székely ◽  
István Horváth
Keyword(s):  
Comparative Analysis ◽  
Political Representation ◽  
Strong Relationship ◽  
Legal Analysis ◽  
Southeast Europe ◽  
Minority Representation ◽  
Representation Dimension ◽  
General Attitude ◽  
External Pressures ◽  
Ethnocultural Diversity

The need to handle ethnocultural diversity and the external pressures of Euro-Atlantic integration have led to the development of complex minority rights regimes in Central and Southeast European states. The aim of this paper is to perform a comparative analysis of the political representation dimension of these regimes, and to investigate how the regulations in this domain are related to the more general attitude of states toward diversity recognition and registration. For this purpose, we classify the states according to a series of variables concerning the manner in which ethnocultural diversity is recognized and portrayed, as well as the regulations concerning the representation of minorities, and identify patterns of their incidence. The formal-legal analysis of the constitutions, minority protection laws and of the electoral legislation of the included countries reveals a clear connection between the general attitude of the state toward diversity and the incidence of autonomies, and a less unequivocal, yet strong relationship in the case of minority representation in the national polity.

Flow Behaviors of Commercial Food Thickeners Used for the Management of Dysphagia: Effect of Temperature

2012 ◽  
Vol 8 (2) ◽  
Author(s):  
Se-Ra Hong ◽  
Dong-Soo Sun ◽  
Whachun Yoo ◽  
Byoungseung Yoo
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Flow Behavior ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
High Shear ◽  
Flow Properties ◽  
Different Temperatures ◽  
Management Of Dysphagia ◽  
Arrhenius Temperature

Gum-based food thickeners are widely used to care for patients with dysphagia in Korea. In this study, the flow properties of commercially available gum-based food thickeners marketed in Korea were determined as a function of temperature. The flow properties of thickeners were determined based on the rheological parameters of the power law and Casson models. Changes in shear stress with the rate of shear (1-100 s-1) at different temperatures (5, 20, 35, and 50 oC) were independent of the type of thickener. All thickeners had high shear-thinning behavior (n=0.08-0.18) with yield stress at the different temperatures tested. In general, apparent viscosity (na,50) values progressively decreased with an increase in temperature. In addition, the consistency index (K) and Casson yield stress (σoc) values did not change much upon an increase in temperature from 5 to 35 oC, except for sample B. In the temperature range of 5-50 oC, the thickeners followed an Arrhenius temperature relationship with a high determination coefficient (R2=0.93-0.97): activation energies (Ea) for the flow of thickeners were in the range of 2.44 - 10.7 kJ/mol. Rheological parameters demonstrated considerable differences in flow behavior between the different gum-based food thickeners, indicating that their flow properties are related to the type of thickener and the flow properties of gum.

A Study of Debris Flow Behaviors According to Rheometer Properties: Focused on the Hwangnyeong Mt. and Umyeon Mt.

2020 ◽  
Author(s):  
Hyeong-Jin Kim ◽  
Dae-Ho Yun ◽  
Yun-Tae Kim
Keyword(s):  
Debris Flow ◽  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Front Velocity ◽  
Experimental Results ◽  
Small Scale ◽  
Water Mixture ◽  
Runout Distance ◽  
Two Samples

<p>A debris flow, a mass movement of soil and water mixture, is generally occurred by heavy rainfall during the rainy season in Korea. Because of climate change, the amount and frequency of rainfall has continually increased these days. Populated areas located in debris flow-prone mountainous areas are commonly subject to debris flow hazards. For this reason, it is necessary to analyze the characteristics of the debris flow behavior for the hazard mitigation. In this study, for two samples from Hwangnyeong Mt. and Umyeon Mt. in Korea, the vane-type rheometer test were performed to estimate the rheological property such as viscosity and yield stress and small-scale flume experiment was carried out to evaluate the characteristics of debris flow behaviors such as front velocity, runout distance and deposition volume. From the experimental results, rheological properties decrease with decreasing volumetric sediment concentration, and debris flow behavior gradually increased with decreasing rheological properties in the experiment. Additionally, in case of Hwangnyeong Mt. which has a high silt and clay fraction, the experimental results show that the amount of the front velocity, runout distance and deposition volume tend to increase higher than Umyeon Mt. as viscosity and yield stress decreased.</p>

Flow Behavior of Fe-3%Si Steel at High Temperatures and Strain Rates

2011 ◽  
Vol 704-705 ◽  
pp. 928-934
Author(s):  
Feng Hui An ◽  
Yu Hui Sha ◽  
Liang Zuo
Keyword(s):  
Yield Stress ◽  
Flow Behavior ◽  
Simulation Method ◽  
Strain Rate Range ◽  
High Yield ◽  
Strain Rates ◽  
Isothermal Compression ◽  
Steady State Flow ◽  
Hot Deformation Behavior ◽  
Controlling Mechanism

Hot deformation behavior of Fe-3%Si steel within temperature range of 1073~1473K and strain rate range of 0.01~5s−1was investigated by isothermal compression test using thermo-simulation method. Over the applied deformation conditions, steady state flow behavior was well described by the power law relationship with dislocation climb as the rate-controlling mechanism, and the high apparent activation energy can be attributed to the high yield stress. A modified Bergström model was proposed by introducing yield stress, and consequently the whole stress-strain curves can be accurately predicted.

Rheological Properties of Butia Pulp

2006 ◽  
Vol 2 (1) ◽  
Author(s):  
Charles Windson Isidoro Haminiuk ◽  
Maria-Rita Sierakowski ◽  
Giselle Maria Maciel ◽  
José Raniere Mazile Bezerra Vidal ◽  
Ivanise Guilherme Branco ◽  
...  
Keyword(s):  
Yield Stress ◽  
Apparent Viscosity ◽  
Good Description ◽  
Flow Behavior ◽  
Rheological Parameters ◽  
Concentric Cylinder ◽  
Flow Behavior Index ◽  
Different Temperatures ◽  
Stress Flow ◽  
Behavior Index

Rheological parameters of Butia pulp were determined at different temperatures using a concentric cylinder Haake Rotovisco rheometer, model RV-20, with measurement system ZA-30. Butia pulp was found to exhibit non-Newtonian, pseudoplastic behavior at all temperatures and the rheological parameters were adequately described by the Herschel-Bulkley model. Yield stress, flow behavior index, and consistency coefficient were significantly affected by temperature. The yield stress decreased exponentially with process temperature and ranged between 36.60 and 21.70 Pa. Apparent viscosity calculated through the Herschel-Bulkley model decreased with an increase in temperature. The Arrhenius model gave a good description of temperature effect on apparent viscosity of the pulp.

Rheological Characterization of Suspension of Hollow Glass Beads

SPE Journal ◽  
2017 ◽  
Vol 22 (05) ◽  
pp. 1671-1680 ◽  
Author(s):  
Simone Lumsden ◽  
John P. Singh ◽  
Ronnie G. Morgan ◽  
Gregory Hundt
Keyword(s):  
Yield Stress ◽  
Surface Area ◽  
Unit Volume ◽  
Flow Behavior ◽  
Fluid Viscosity ◽  
Rheological Characterization ◽  
Concentrated Suspension ◽  
Hollow Glass ◽  
Glass Spheres ◽  
Liquid Suspension

Summary Hollow glass spheres (beads) are widely used as density and rheological modifiers for various oil and gas process fluids, particularly cement. One of the primary uses is to achieve lightweight slurries with good mechanical properties of the set cement. This paper discusses a concentrated, yet pumpable, suspension of these spheres for offshore cementing applications. Providing the lightweight spheres in a liquid suspension eliminates the risks associated with dry blending these materials. The development of the liquid suspension of hollow beads enables on-the-fly mixing of cement slurries with desired density profiles. Currently, the beads are premixed in the cement powder before they are shipped to offshore locations, which could result in the segregation of the beads during delivery and storage, and limits operations to the predetermined density (concentration of beads) of the slurry. This paper presents the rheological behavior of the concentrated suspension (up to 60% vol/vol) of hollow glass spheres suspended in a dilute aqueous solution of bentonite and soda ash. In addition, an attachment to the viscometer (called Fann Yield Stress Adaptor or FYSA) was used to characterize the flow behavior. A rheological model was developed to highlight the bead/bead surface interactions as a major component controlling flow behavior. Four different variants of beads were studied. These were selected to represent a range in surface area per unit volume of beads. Increasing the concentration of beads or the bentonite in solution correlated to increased yield stress and fluid viscosity at operational shear rates. In addition, a Krieger-Dougherty-type relation captured well the effect of the bead concentration, with the maximum packing fraction of beads as a function of surface area per unit volume of the beads. Overall, the Herschel-Bulkley (HB) model best described the suspension rheology with the shear-thinning exponent in the range of ≈0.8 to 1.0. Surface area of the beads linearly correlated to the yield stress of the corresponding concentrated bead solution. Results of this study and the model developed can be used to develop variants of the system with minimal experimentation, thus significantly shortening the design time.

Dislocation Core Structure and the Normal Yield Behavior of L12 Ordered Alloys

1984 ◽  
Vol 39 ◽  
Author(s):  
G. Tichy ◽  
V. Vitek ◽  
D. P. Pope
Keyword(s):  
Yield Stress ◽  
High Temperatures ◽  
Flow Behavior ◽  
Dislocation Core ◽  
Screw Dislocations ◽  
Thermally Activated ◽  
Normal Behavior ◽  
Ordered Alloys ◽  
Increasing Temperature ◽  
Good Agreement

ABSTRACTA rapid increase of the yield stress with increasing temperature, often observed in L12 ordered alloys, is commonly called the “anomalous flow behavior”. This phenomenon is believed to result from the thermally activated transformation of the core of 1/2<110> screw dislocations from a glissile form to a sessile form at high temperatures. It is shown here that another class of L12 alloys exists in which these two forms of the screw dislocation core are not available. These are the alloys in which the APB on {111} planes is not stable and the atomistic studies of screw dislocations in such alloys show that their cores are always sessile. The yield stress of these alloys then increases with decreasing temperature and no increase at high temperatures occurs. Such behavior has been observed, for example, in Pt3Al. This “normal” behavior is analogous to that of b.c.c. metals and a theory of the temperature dependence of the yield stress has been developed along the same lines as in the case of b.c.c. metals. Comparison of this theory with measurements on Pt3Al single crystals shows a good agreement.

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