Transferencia de masa y calor en el secado de lechos rellenos por circulación transversal de aire

El término ’’secado” expresa la eliminación por evaporación dei líquido contenido en un sólido; el calor necesario para la evaporación puede ser suministrado por convección desde un gas caliente, conducción a través de una superficie, o por radiación. Cuando un sólido se seca ocurren simultáneamente dos procesos fundamentales: 1º) se transfiere calor para evaporar el líquido, y 2º) se transfiere materia como líquido o como vapor dentro del sólido, y como vapor desde la superficie. Los factores que gobiernan la velocidad de estos procesos determinan la velocidad de secado. La presente investigación tiene por objeto estudiar diversos aspectos del llamado ”período de velocidad de secado constante’’ en este período, el secado ocurre por difusión de vapor desde la superficie saturada del material a través de una película de aire. El movimiento de humedad dentro del sólido es suficientemente rápido como para mantener la condición de saturación en la superficie, y la velocidad de secado es controlada por la velocidad de transferencia de calor a la superficie de evaporación. La velocidad de transferencia de masa balancea a la de calor, y la temperatura de la superficie saturada permanece constante.Tesis digitalizada en SEDICI gracias a la colaboración de la Biblioteca de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta

Chemical characterization of an encapsulated red wine powder and its effects on neuronal cells

Red wine polyphenols are known for their implications for human health protection, although they suffer from high instability. For this reason, a red wine powder was prepared by freeze-drying encapsulation in maltodextrin/arabic gum matrix, and its composition was determined by means of high-performance liquid chromatography coupled quadrupole time-of-flight mass spectrometry (HPLC-MS-QTOF). More than thirty polyphenols, including anthocyanins, flavanols, flavonols, phenolic acids and stilbenoids, were identified. Some of the main quantified polyphenols were: malvidin-3-O-glucoside, malvidin 3-O-(6”-acetyl-glucose), petunidin-3-O-glucoside, quercetin-3-O-glucuronide, syringenin-3-O-glucoside, epicatechin, gallic acid and syringic acid. The biological activity of this de-alcoholized and encapsulated red wine on human neuroblastoma SH-SY5Y cells was studied. The results showed that the encapsulated red wine powder has active redox properties, as verified by performing reactive oxygen species (ROS) analysis utilizing a neuronal model. This could help explain its action against the neurotoxicity induced by 6-hydroxydopamine (6-OHDA).Fil: Rocha Parra, Diego Fernando. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; España. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chirife, Jorge. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Zamora, María Clara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: de Pascual Teresa, Sonia. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; Españ

Drying/encapsulation of red wine to produce ingredientes for healthy foods

Epidemiological evidence indicates that moderate consumption of red wine reducesthe incidence of coronary disease, atherosclerosis, and platelet aggregation. Wine is very rich in antioxidant compounds because of their phenolic components.However, many people for ethnic, social or religious reasons do not consume wine. Drying/encapsulation of red wine in the presence of adequate carbohydrates leads to water and more than 99% of alcohol removal; a glassy amorphous microstructure is obtained in which the wine's phenolic compounds are entrapped. The resulting product is a free flowing powder which could be used for the polyphenol enrichment of healthy foods and/or drink powders, as well as in the pharmaceutical industry. The wine industry may take advantage of the dried/encapsulated red wine using as a raw material red wines which have littlecommercial value for different reasons; i.e. poor quality due to raw material, unfavourable climatic conditions, or wines that suffered some alteration during the wine making process. Dry encapsulated wine may be a new alternative to red wines that cannot be sold as such for different reasons, and open new opportunities to diversify wine products.Fil: Alvarez Gaona, Izmari Jasel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Rocha Parra, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Zamora, María Clara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Chirife, Jorge. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; Argentin

Determination of heat transfer coefficients of biological systems during cooling in liquid nitrogen under film and nucleate pool boiling regimes

The cryopreservation process consists of reducing the temperature of the sample to a point where biological stability is achieved. In particular the measurement of the temperature change of the sample is important to calculate cooling rates and to determine if a sample is vitrified or undergoes phase change transition. As soon an object is plunged into liquid nitrogen it enters into a film boiling regime due to the large temperature difference between the object and the liquid nitrogen (LN2). This determines a heat flux from the object to LN2 causing the latter to boil in the immediate vicinity of the object and creating a pocket of nitrogen vapor around the object which acts as an “insulator” and retards further heat transfer. Film boiling is also referred to as the “Leidenfrost effect”. Boiling curves for a specific cryobiological system are scarcely found in the literature due to the small dimensions of the devices used in the process and the experimental limitations. The experimental information such as the time-temperature curve allows the prediction of the surface heat transfer coefficients that govern the cooling process: film, transition and nucleate boiling. In order to predict the surface heat transfer coefficient for each boiling regime the mathematical modeling of the partial differential equations that represent the energy transfer must be implemented, applying convective boundary conditions. In this work the different heat transfer coefficients and the boiling curve of straws filled with ice (at an initial temperature between -2ºC to -9ºC) were experimentally measured when they were immersed in liquid nitrogen; this allowed to determine the existence of different boiling regimes. The application of a numerical finite element program using the software COMSOL was used to predict time-temperature curves and to obtain the surface heat transfer coefficients that control each boiling regime. Independent experiments were carried out using straws that contained a biological fluid (semen+extender), which were initially at room temperature, to further validate the different surface heat transfer coefficients for film and nucleate pool boiling. The program takes into account the variable thermo-physical properties of the biological sample. This constitutes a highly non-linear mathematical problem, as the freezing process evolves with a variable surface heat transfer coefficients as the different boiling regimes occur. The program was experimentally validated contrasting experimental temperatures vs. time with numerical predictions. The numerical program is an important tool in order to correctly assess the heat transfer process and optimize the cryopreservation of straws filled with biological fluids.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Determination of heat transfer coefficients of biological systems during cooling in liquid nitrogen under film and nucleate pool boiling regimes

The cryopreservation process consists of reducing the temperature of the sample to a point where biological stability is achieved. In particular the measurement of the temperature change of the sample is important to calculate cooling rates and to determine if a sample is vitrified or undergoes phase change transition. As soon an object is plunged into liquid nitrogen it enters into a film boiling regime due to the large temperature difference between the object and the liquid nitrogen (LN2). This determines a heat flux from the object to LN2 causing the latter to boil in the immediate vicinity of the object and creating a pocket of nitrogen vapor around the object which acts as an “insulator” and retards further heat transfer. Film boiling is also referred to as the “Leidenfrost effect”. Boiling curves for a specific cryobiological system are scarcely found in the literature due to the small dimensions of the devices used in the process and the experimental limitations. The experimental information such as the time-temperature curve allows the prediction of the surface heat transfer coefficients that govern the cooling process: film, transition and nucleate boiling. In order to predict the surface heat transfer coefficient for each boiling regime the mathematical modeling of the partial differential equations that represent the energy transfer must be implemented, applying convective boundary conditions. In this work the different heat transfer coefficients and the boiling curve of straws filled with ice (at an initial temperature between -2ºC to -9ºC) were experimentally measured when they were immersed in liquid nitrogen; this allowed to determine the existence of different boiling regimes. The application of a numerical finite element program using the software COMSOL was used to predict time-temperature curves and to obtain the surface heat transfer coefficients that control each boiling regime. Independent experiments were carried out using straws that contained a biological fluid (semen+extender), which were initially at room temperature, to further validate the different surface heat transfer coefficients for film and nucleate pool boiling. The program takes into account the variable thermo-physical properties of the biological sample. This constitutes a highly non-linear mathematical problem, as the freezing process evolves with a variable surface heat transfer coefficients as the different boiling regimes occur. The program was experimentally validated contrasting experimental temperatures vs. time with numerical predictions. The numerical program is an important tool in order to correctly assess the heat transfer process and optimize the cryopreservation of straws filled with biological fluids.Fil: Santos, Maria Victoria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Sansinena, Marina Julia. Pontificia Universidad Catolica Argentina "Santa Maria de Los Buenos Aires". Facultad de Ciencias Agrarias; ArgentinaFil: Chirife, Jorge. Pontificia Universidad Catolica Argentina "Santa Maria de Los Buenos Aires". Facultad de Ciencias Agrarias; ArgentinaFil: Zaritzky, Noemi Elisabet. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

In-vitro development of vitrified-warmed bovine oocytes after activation may be predicted based on mathematical modelling of cooling and warming rates during vitrification, storage and sample removal

Heat transfer during cooling and warming is difficult to measure in cryo-devices; mathematical modelling is an alternative method that can describe these processes. In this study, we tested the validity of one such model by assessing in-vitro development of vitrified and warmed bovine oocytes after parthenogenetic activation and culture. The viability of oocytes vitrified in four different cryo-devices was assessed. Consistent with modelling predictions, oocytes vitrified using cryo-devices with the highest modelled cooling rates had significantly (P < 0.05) better cleavage and blastocyst formation rates. We then evaluated a two-step sample removal process, in which oocytes were held in nitrogen vapour for 15 s to simulate sample identification during clinical application, before being removed completely and warmed. Oocytes exposed to this procedure showed reduced developmental potential, according to the model, owing to thermodynamic instability and devitrification at relatively low temperatures. These findings suggest that cryo-device selection and handling, including method of removal from nitrogen storage, are critical to survival of vitrified oocytes. Limitations of the study include use of parthenogenetically activated rather than fertilized ova and lack of physical measurement of recrystallization. We suggest mathematical modelling could be used to predict the effect of critical steps in cryopreservation.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Influence of storage conditions on phenolic compounds stability, antioxidant capacity and colour of freeze-dried encapsulated red wine

A concentration of 9% (w/w) maltodextrin (DE 10) and gum arabic was added to red wine C. sauvignonand freeze dried to obtain a dealcoholized wine powder having a polyphenols concentration 7.1 timeshigher than in liquid red wine. Malvidin 3-G and total anthocyanins were the phenolics showing greaterlosses during storage. Moreover, an increase of water activity from 0.11 to 0.58 greatly enhanced thelosses. The decrease in malvidin 3-G content was associated with the decrease on redness (colourparameter a*) of wine powder. Gallic acid was the most stable phenolic and its content remained constant during storage at all water activity levels under investigation. Contents of epicatechine, catechine, caffeic acid and resveratrol remained constant at aw = 0.11, although at aw = 0.33 catechine and epicatechine suffered important losses. Results indicated that water activity was a key factor affecting phenolics stability during storage.Antioxidant activity of the wine powder remained constant over 145 days at accelerated storage conditions.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Freeze-Drying Encapsulation of Red Wine Polyphenols in an Amorphous Matrix of Maltodextrin

Maltodextrin DE 10 was added to Argentine red wine (Cabernet Sauvignon) in a 20% concentration (total weight basis), and the resulting solution was freeze-dried. Water and almost all ethanol were eliminated during freeze-drying leaving an amorphous glassy maltodextrin microstructure (i. e., "wine powder"), containing the red wine's polyphenols (as well as other non-volatile constituents of the dry extract). Almost no loss of total polyphenols was found in the freeze-drying process. Upon milling, the maltodextrin microstructure yielded a free-flowing powder, and its glassy nature was confirmed by measuring its glass transition temperature (Tg). After 15 days, storage at 38 °C total polyphenols content in the "wine powder" remained practically unchanged. This free-flowing powder contained 3. 7 times the concentration of polyphenols in red wine, while only containing less than 1% ethanol. This might be added to other powdered foods as a source of wine polyphenols.Fil: Sanchez, Virginia Estela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Facultad de Ciencias Agrarias. Departamento de Alimentos; ArgentinaFil: Baeza, Rosa Isabel. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Facultad de Ciencias Agrarias. Departamento de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galmarini, Mara Virginia. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Facultad de Ciencias Agrarias. Departamento de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zamora, María Clara. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Facultad de Ciencias Agrarias. Departamento de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chirife, Jorge. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Facultad de Ciencias Agrarias. Departamento de Alimentos; Argentin

Application of hedonic dynamics using multiplesip temporal-liking and facial expression for evaluation of a new beverage

Abstract: Drinking and eating are not a matter of a single sip or bite. Dynamic data gathered from multiple sip or bite, seem to be more reliable than simple sip/bite evaluation. However, methodologies and analyses based on multiple sips/bites have received little attention until recently. The present study tested an innovative approach to measure the temporal changes in acceptance. It combines multiple-sip temporal-liking measurements (MSTL) with implicit taste reactivity using facial pattern expressions at different time points, for evaluation of a new beverage. Seventy-three consumers (35 females and 38 males) evaluated acceptance during 60 s, drinking three sips, with each sip every 20 s. The consumers’ faces were filmed by a camera during the test session in order to analyze facial affective reactions. The results of the present paper show that MSTL modality allows seeing temporal changes in the acceptance of the beverage. Parameters analyzed maximum intensity (Imax) and area under the curve (AUC) in selfreported response curves presented variation through successive sips. The self-rated liking increased from the first sip to the third. In the same way facial expressions also showed a change over time during successive sips. In this case, the basic emotion of disgust, unpleasantness-related Action Units (AUs; AU 26 and AU 15) and negative valence showed a decrease from the first sip to the third one. It was observed that negative facial reactions are greater than the positive facial reactions in intensity

Determination of heat transfer coefficients in plastic French straws plunged in liquid nitrogen

The knowledge of the thermodynamic process during the cooling of reproductive biological systems is important to assess and optimize the cryopreservation procedures. The time–temperature curve of a sample immersed in liquid nitrogen enables the calculation of cooling rates and helps to determine whether it is vitrified or undergoes phase change transition. When dealing with cryogenic liquids, the temperature difference between the solid and the sample is high enough to cause boiling of the liquid, and the sample can undergo different regimes such as film and/or nucleate pool boiling. In the present work, the surface heat transfer coefficients (h) for plastic French straws plunged in liquid nitrogen were determined using the measurement of time–temperature curves. When straws filled with ice were used the cooling curve showed an abrupt slope change which was attributed to the transition of film into nucleate pool boiling regime. The h value that fitted each stage of the cooling process was calculated using a numerical finite element program that solves the heat transfer partial differential equation under transient conditions. In the cooling process corresponding to film boiling regime, the h that best fitted experimental results was h = 148.12 ± 5.4 W/m2 K and for nucleate-boiling h = 1355 ± 51 W/m2 K. These values were further validated by predicting the time–temperature curve for French straws filled with a biological fluid system (bovine semen-extender) which undergoes freezing. Good agreement was obtained between the experimental and predicted temperature profiles, further confirming the accuracy of the h values previously determined for the ice-filled straw. These coefficients were corroborated using literature correlations. The determination of the boiling regimes that govern the cooling process when plunging straws in liquid nitrogen constitutes an important issue when trying to optimize cryopreservation procedures. Furthermore, this information can lead to improvements in the design of cooling devices in the cryobiology field.Facultad de Ingenierí