Effect of the drying method and texture improvers on reconstitution behavior of yogurt powder: physical and microbiological properties / Efecto del método de secado y mejoradores de textura sobre el comportamiento de reconstitución de un yogurt en polvo: propiedades físicas y microbiológicas

Background: One of the most used and effective preservation strategies in foods is drying. However, there are problems with the rheological properties, color, and viability of lactic acid bacteria in the yogurt once reconstituted when applying such conservation strategies. Objectives: Determine the concentration of the type of texture improver and drying that minimizes the negative effect on the rheological, color, and microbiological properties of a reconstituted yogurt powder. Methods: Intended to determine the texture improver which increases rheological properties of reconstituted yogurt powder, a mixture type experimental design was applied where three texture improvers were assessed; carboxymethylcellulose (CMC) (mass fraction 0 - 1), pectin (mass fraction 0 - 1), and xanthan gum (mass fraction 0 - 1). The rheological parameters; consistency index (K), flow behavior (n), viscosity at 100s-1 (η), the storage (G') and loss (G'') modules, and the phase shift angle (δ) of each of the reconstitutions were considered as design-dependent variables. Secondly, a central composite design (face-centered) was used for assessing the effectiveness of the drying (convection, spray-drying, and freeze-drying), the concentration of the texture improver (0.0 - 1.0 %), and the yogurt powder concentration (8.0 - 15.0 %). The above-mentioned rheological parameters, color, and viability of the lactic acid bacteria from each reconstituted yogurt powder were considered as the dependent variables. Optimization sought to match the parameters of reconstituted yogurt powder that approximated the conditions of fresh yogurt. Results: The independent variables in their lineal expression and some interactions between them had statistically significant differences (p < 0.05). At a concentration of 10.59 % with 0.03 % xanthan gum, the reconstitution of freeze-dried yogurt powder was the optimized condition (p < 0.05) and obtained the rheological, color, and microbiological parameters closest to fresh yogurt. Conclusions: The drying of the yogurt by freeze-drying mixed with xanthan gum as a texture improver allowed to obtain a reconstituted yogurt with properties close to the fresh product for direct consumption

Antecedentes: Una de las estrategias de conservación más utilizadas y efectivas en los alimentos es el secado. Sin embargo, existen problemas en las propiedades reológicas, el color y la viabilidad de bacterias ácido lácticas en el yogur una vez reconstituido al aplicar tales estrategias de conservación. Objetivos: Determinar la concentración del tipo de mejorador de textura y secado que minimiza el efecto negativo sobre las propiedades reológicas, de color y microbiológicas de un yogur en polvo reconstituido. Métodos: Para determinar el mejorador de textura que aumente las propiedades reológicas del yogur en polvo reconstituido, se aplicó un diseño experimental de tipo de mezcla donde se evaluaron tres mejoradores de textura; carboximetilcelulosa (CMC) (fracción de masa 0 -1), pectina (fracción de masa 0 -1) y goma xantan (fracción de masa 0 -1); los parámetros reológicos: índice de consistencia (K), comportamiento de flujo (n), viscosidad a 100s-1 (η), módulos de almacenamiento (G') y pérdida (G''), y ángulo de desfase (δ) de cada una de las reconstituciones fueron considerados como variables dependientes. En segundo lugar, se utilizó un diseño central compuesto (centrado a las caras) para evaluar el efecto del tipo de secado (convección, secado por aspersión y liofilización), la concentración del mejorador de textura (0.0 - 1.0 %) y concentración del yogur en polvo (8.0 - 15.0 %). Como variables dependientes se consideraron los parámetros reológicos mencionados anteriormente, el color y la viabilidad de las bacterias ácido lácticas de cada yogur en polvo reconstituido. La optimización buscó igualar los parámetros del yogur en polvo reconstituido que se aproximaran a las condiciones del yogur fresco. Resultados: Las variables independientes en su expresión lineal y algunas interacciones entre ellas tuvieron diferencias estadísticamente significativas (p < 0.05). La reconstitución de yogur liofilizado en polvo a una concentración de 10.59 % con 0.03 % de goma xantan, fueron las condiciones optimizadas (p < 0.05) que obtuvieron los parámetros reológicos, de color y microbiológicos más cercanos al yogur fresco. Conclusión: El secado del yogur por liofilización mezclado con goma xantan como mejorador de la textura, permitió obtener un yogur reconstituido con propiedades cercanas al producto fresco para consumo directo

Chemical Properties, Rheological Behavior, and Melissopalynological Analysis of Selected Brazilian Honeys from Hovenia dulcis Flowering

Abstract Monofloral honeys are high-added-value food, a reason for constant cases of fraud. This study investigated Brazilian monofloral honeys from Hovenia dulcis flowering produced by Apis mellifera and Tetragonisca angustula bees. Chemical, physicochemical, rheological, and melissopalynological analysis were assessed. Properties such as moisture, pH, ashes, total acidity, total available carbohydrate, and soluble sugars of all analyzed honey samples agreed with the established by the legislation. All the honey samples were satisfactorily fitted by both Ostwald-de Waele and Casson rheological models revealing homogenous products, mostly presenting pseudoplastic character. The melissopalynology confirmed the presence of H. dulcis pollen in the MH samples; however, some honeys did not show >45% pollen of H. dulcis, thus revealing mislabeling cases. Continuous evaluation of honey is necessary, once this is a valuable food frequently involved in frauds, hence causing problems to consumers.

Rheological Properties and Retention Ability of Octoxynol-9 Vaginal Thermosensitive in Situ Gel / 中国药师

Objective: To observe the rheological properties of octoxynol-9 vaginal thermosensitive in situ gel [(O-9)-VTG] for predicting the gelation behavior in vivo, and evaluate the retention ability in vagina.Methods: The rheological parameters of (O-9)-VTG and (O-9)-VTG diluted by stimulant vaginal fluid (SVF) were measured by a Haake Rheomix to characterize the rheological properties.The vaginal samples after the administration of self-made (O-9)-VTG and O-9 gel were withdrawn, and then the concentration of octoxynol-9 in the samples was determined to evaluate the retention ability.Results: (O-9)-VTG was Newtonian fluid with low viscoelasticity under room temperature and converted to gel at 32.6℃.The formula could still transform into gel at body temperature after diluted by SVF, and resided in the vagina of mice above 8 h.Conclusion: (O-9)-VTG has suitable gelation temperature and rheological properties.Compared with the self-made octoxynol-9 gel, (O-9)-VTG has satisfactory retention in vagina, which meets the requirements for vaginal topical use.

Preparation and Characterization of Polymeric Mucoadhesive Film for Buccal Administration.

Objectives: Buccal films consist mainly of polymer that has a good mucoadhesive profile and plasticizer. A lot of polymers and plasticizers can be used to configure the mucoadhesive films as hydroxyethyl cellulose and glycerin respectively. Material and Methods: Films prepared by dispersing the polymer, mixing it with plasticizer and pouring it in Petri dishes to be dried and cut finally. Physicochemical tests were used to evaluate the films. These tests are organoleptic evaluation and polymer and plasticizer selection, determination of rheological properties of polymers, film thickness, and determination of moisture content, determination of moisture uptake and evaluation of mechanical properties. Results and Conclusions: It was found that films prepared from polyvinyl alcohol 2% (w/w) especially with the addition of propylene glycol 20% from the weight of the polymer have excellent characteristics. This formula has promising organoleptic and mechanical properties and its solution is Non-Newtonian pseudoplastic. Moreover, this formula is very thin and has moderate percent of moisture content and moisture uptake. Also, it has high elongation with moderate tensile strength. As a result, it is better to prepare the film by these ingredients to obtain an ideal mucoadhesive formula.

Rheological properties of dental resin cements during polymerization / 대한치과보철학회지

PURPOSE: The purpose of this study was to observe the change of viscoelastic properties of dental resin cements during polymerization. MATERIALS AND METHODS: Six commercially available resin cement materials (Clearfil SA luting, Panavia F 2.0, Zirconite, Variolink N, RelyX Unicem clicker, RelyX U200) were investigated in this study. A dynamic oscillation-time sweep test was performed with AR1500 stress controlled rheometer at 32degrees C. The changes in shear storage modulus (G'), shear loss modulus (G"), loss tangent (tan delta) and displacement were measured for twenty minutes and repeated three times for each material. The data were analyzed using one-way ANOVA and Tukey's post hoc test (alpha=0.05). RESULTS: After mixing, all materials demonstrated an increase in G' with time, reaching the plateau in the end. RelyX U200 demonstrated the highest G' value, while RelyX Unicem (clicker type) and Variolink N demonstrated the lowest G' value at the end of experimental time. Tan delta was maintained at some level and reached the zero at the starting point where G' began to increase. The tan delta and displacement of the tested materials showed similar pattern in the graph within change of time. The displacement of all 6 materials approached to zero within 6 minutes. CONCLUSION: Compared to other resin cements used in this study, RelyX U200 maintained plastic property for a longer period of time. When it completed the curing process, RelyX U200 had the highest stiffness. It is convenient for clinicians to cement multiple units of dental prostheses simultaneously.

Synthesis, characterization and rheological properties of guaran grafted polyacrylamide (G-G-Pam) copolymer.

Guaran was transformed into grafted polymer using vinyl monomer. The vinyl monomer used for the graft was acrylamide. The grafting was initiated through the formation of free radical centers on the polymer backbone by oxidation of guaran with cerium (IV) in nitric acid medium. The degree of grafting was varied by using varying amount of acrylamide vinyl monomer. The rheological properties of the guaran grafted polyacrylamide copolymer have been studied by varying the degree of grafting, time, concentration, temperature, spindle number and shear rate. Thermal Characteristics of the guaran-grafted polyacrylamide was studied using thermo gravimetric analysis under nitrogen atmosphere. The prepared copolymer was characterized by FTIR.

Evaluación de las propiedades flexurales y reológicas de cinco resinas compuestas formuladas para restauraciones anteriores / Evaluation of flexural and rheological properties of five resin composites formulated for anterior restorations

El objetivo de esta investigación fue evaluar las propiedades flexurales y reológicas de cinco resinas compuestas formuladas para restauraciones anteriores. Materiales y métodos: Se realizaron 17 muestras de resinas compuestas para cada grupo: G1 Ice® esmalte A2, G2 Ice® dentina OA2 (SDI), G3 Tetric N- Ceram® A2, G4 InTen-S® A3, G5 Tetric - Ceram® A2 (Ivoclar/Vivadent), G6 Filtek Z350® A2 (3M/ESPE); 10 muestras de cada grupo se confeccionaron con dimensiones de 25 mm de largo x 2 mm de alto x 2 mm de ancho para ser sometidas test de flexión de tres puntos, en una máquina de pruebas universales (Shimadzu AGS-J) a una velocidad de 1 mm/min. Para la prueba de escurrimiento se confeccionaron 7 muestras por cada grupo, de 5mm de diámetro x 3 mm de alto sin polimerizar entre 2 láminas de policarbonato con una carga de 20 Newtons x 60 segundos. Los datos fueron analizados con un ANOVA de 1 Vía para cada variable, utilizando el Software estadístico SPSS 15.0 ®. Resultados: La variable resistencia flexural obtuvo una p= 0,000; lo que indica diferencia estadística significativa, los grupos se ubicaron: G6? G2, G3= G1, G5> G4. La variable módulo flexural obtuvo un p= 0,000 lo que indica diferencia estadística significativa, los grupos se ubicaron: G6? G2, G3= G5, G1> G4. La variable escurrimiento obtuvo un p= 0,000 lo que indica diferencia estadística significativa, los grupos se ubicaron: G2> G3, G4? G6, G5, G1. Conclusiones: En las condiciones en que se realizó esta investigación las propiedades flexurales de las resinas compuestas de nanorrelleno G6 fueron superiores a las híbridas G5, G4; las microhíbridas G2, G1 y la nanohíbrida G3. La capacidad de escurrimiento no parece estar influenciada por el porcentaje de relleno proporcionado por el fabricante, la clase y la marca comercial, ya que casi todos los grupos presentaron un escurrimiento homogéneo; sin embargo el G2 parece tener una viscosidad reducida lo cual se relaciona con una difícil manipulación

The aim of this study was to evaluate flexural and rheological properties of five resin composites formulated for anterior restorations. Materials and methods: 17 samples of resin composite were made for each group: G1 Ice® enamel A2, G2 Ice® dentine OA2 (SDI), G3 Tetric N- Ceram® A2, G4 InTen-S® A3, G5 Tetric - Ceram® A2 (Ivoclar/Vivadent), G6 Filtek Z350® A2 (3M/ESPE); 10 samples of each group were made with a 25 x 2 x2 mm dimension and submitted at the three-point flexural test, in a universal testing machine (Shimadzu AGS-J) at a speed of 1 mm/min. For the flow test a load of 20 Newtons during 60 seconds, were applied at 7 samples of each group made of 5mm of diameter and 3 mm of thickness without photocuring between the two polycarbonate laminate. The data were analyzed whit a one way ANOVA for each variable, using statistical Software SPSS 15.0 ®. Results: The flexural strength variable obtained a p= 0,000 value indicating a strong and significant statistical difference, the ranks groups were: G6? G2, G3= G1, G5> G4. The elastic module variable obtained a p= 0.000 value; indicating significant statistical difference, the ranks groups were: G6? G2, G3= G5, G1> G4. The slumping resistance variable obtained a p= 0.000 value indicating significant statistical difference, the ranks groups were: G2> G3, G4? G6, G5, G1. Conclusions: In the conditions in which this research was made the flexural properties of nanofilled composite resin G6 were superior to the G5, G4 hybrids; the G2, G1 micro-hybrids and the nano-hybrid G3. The flow capacity seems not to be influenced by the percentage of filling referred by the manufacturer, the class and the trade name since almost all the groups presented a homogenous flow; nevertheless the G2 seems to have a reduced viscosity which is related to a difficult manipulation

Rheological properties and gel properties of agar / 中国海洋药物

Objective Rheological properties and gelation properties of agar were investigated. Methods The gelling point,melting point and the gel strength of agar were detected with MCR101 rheometer and TA texture testing instrument. Results and Conclusion Rheological properties of agar were affected by its concentration ,temperature and the addition of salt (such as NaCl ,CaCl2) and sucrose. Apparent viscosity exhibited shear thinning behavior following the power law model. Apparent viscosity increased with the increase of concentration,and decreased with the rise of temperature. The decrease in viscosity followed an Arrhenius temperature dependence. Agar solutions exhibited typical "weak gel" properties by small strain oscillatory measurements. The results indicated that the agar solution was characterized as a gel properties ,and which could form a kind of heat reversible gel. The gelling point of agar was lower than its melting point. The gel strength of agar could be affected by its gel time,and the addition of salt (such as NaCl,CaCl2) and sucrose.