Modeling and simulation of parametric sensitivity in primary freeze-drying of foodstuffs

Chakraborty, Rajat; Saha, Abhijit; Bhattacharya, Pratik

doi:10.1016/j.seppur.2005.10.008

Cited by 26 publications

(12 citation statements)

References 9 publications

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“…In freeze-drying of products in vials and shelves the thermocouples were placed in the bottom of the sample to determine the product temperature in the primary drying when all ice crystals were sublimated. Bhattacharya and Mahajan (2003) and Chakraborry and Bhattacharya (2006).…”

Section: Resultsmentioning

confidence: 99%

“…Some authors have determined the primary drying rate by stopping the freeze-drying process at a fixed point and measuring the weight lost during this partial drying phase (Searles, Carpenter, Randolph, 2011;Chakraborry, Saha, Bhattacharya, 2006). Pikal et al (1983) described a microbalance technique to determine sublimation rates by evaluating the dried layer resistance of different materials.…”

Section: Introductionmentioning

confidence: 99%

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Freeze-drying microscopy in mathematical modeling of a biomaterial freeze-drying

Borgognoni

Bevilacqua

Pitombo

2012

Braz. J. Pharm. Sci.

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Transplantation brings hope for many patients. A multidisciplinary approach on this field aims at creating biologically functional tissues to be used as implants and prostheses. The freeze-drying process allows the fundamental properties of these materials to be preserved, making future manipulation and storage easier. Optimizing a freeze-drying cycle is of great importance since it aims at reducing process costs while increasing product quality of this time-and-energy-consuming process. Mathematical modeling comes as a tool to help a better understanding of the process variables behavior and consequently it helps optimization studies. Freeze-drying microscopy is a technique usually applied to determine critical temperatures of liquid formulations. It has been used in this work to determine the sublimation rates of a biological tissue freeze-drying. The sublimation rates were measured from the speed of the moving interface between the dried and the frozen layer under 21.33, 42.66 and 63.99 Pa. The studied variables were used in a theoretical model to simulate various temperature profiles of the freeze-drying process. Good agreement between the experimental and the simulated results was found.Uniterms: Freeze-drying microscopy. Bovine pericardium. Mathematical modeling.A prática da transplantação traz esperança para muitos pacientes. Uma visão multidisciplinar nessa área visa à produção de tecidos biológicos para serem utilizados como implantes e próteses. A liofilização é um processo de secagem que preserva características essenciais desses materiais, facilitando sua manipulação e armazenamento. A liofilização é um processo que requer muito tempo e energia e sua otimização é muito importante, pois permite reduzir custos de processo melhorando a qualidade do produto. A modelagem matemática é uma ferramenta que permite descrever o comportamento do produto durante o processo e, consequentemente, auxilia os estudos de otimização. Microscopia óptica acoplada à liofilização, uma técnica usualmente aplicada na determinação de temperaturas críticas de formulações líquidas, foi utilizada neste trabalho na determinação de taxas de sublimação da liofilização de um tecido biológico. As taxas de sublimação foram calculadas a partir da velocidade da interface entre a camada seca e congelada, sob pressões de 21,33, 42,66 e 63,99 Pa. As variáveis estudadas foram usadas em um modelo matemático teórico, que simula os perfis de temperatura do produto durante o ciclo de liofilização. Os resultados apresentados demonstraram boa relação entre os dados experimentais e simulados.Unitermos: Microscopia óptica acoplada à liofilização. Pericárdio bovino. Modelagem matemática.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Freeze-drying microscopy in mathematical modeling of a biomaterial freeze-drying

Borgognoni

Bevilacqua

Pitombo

2012

Braz. J. Pharm. Sci.

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“…They are as follows [10]: 1) Heat transfer and mass transfer occur in one dimension only, which is normal to the sublimation interface and surface; 2) Sublimation occurs at an interface parallel to and at distance X from the surface;…”

Section: Methodsmentioning

confidence: 99%

“…But this method has a weakness, i.e., the product nutrients could evaporate due to decrease in the boiling point [9]. Then, to accelerate the drying rate and reduce the drying time, additional heat is added to sublimate the ice directly into the gas phase [10][11]. The heat source could be an electrical heater, microwave or waste heat condenser [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Then, to accelerate the drying rate and reduce the drying time, additional heat is added to sublimate the ice directly into the gas phase [10][11]. The heat source could be an electrical heater, microwave or waste heat condenser [10][11][12][13]. This method preserves the nutrition content, color, taste, and biological structure of a specimen.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of Vacuum Freeze Drying with Utilization of Internal Cooling and Condenser Waste Heat for Sublimation

Alhamid

Yusuf

Mahlia

et al. 2013

MST

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Vacuum freeze drying is an excellent drying method, but it is very energy-intensive because a relatively long drying time is required. This research investigates the utilization of condenser waste heat for sublimation as a way of accelerating the drying rate. In addition, it also investigates the effect of internal cooling combined with vacuum cooling in the pressure reduction process. Jelly fish tentacles were used as the specimen, with different configurations for condenser heat waste and internal cooling valve opening. The results show that heating with condenser heat waste can accelerate the drying rate up to 0.0035 kg/m 2 .s. In addition, pre-freezing by internal cooling prevents evaporation until the mass of the specimen is 0.47 g and promotes transition of the specimen into the solid phase. AbstrakKarakteristik Pengering Beku Vakum dengan Menggunakan Pendinginan Internal dan Panas Buang Kondenser untuk Sublimasi. Pengering beku vakum adalah metode pengeringan yang terbaik, tetapi konsumsi energinya sangat tinggi karena lamanya waktu pengeringan yang diperlukan. Penelitian ini mengkaji penggunaan panas buang kondenser untuk proses sublimasi sebagai salah satu cara untuk mempercepat laju pengeringan. Disamping itu, juga mengkaji pengaruh pendinginan internal yang dikombinasikan dengan pendinginan vakum pada waktu dilakukan proses penurunan tekanan. Tentakel ubur-ubur (Jelly fish tentacles) digunakan sebagai bahan percobaan dengan berbagai konfigurasi panas buang kondensor dan pembukaan katup pendinginan internal. Hasilnya menunjukkan bahwa pemanasan dengan panas buang kondensor dapat mempercepat laju pengeringan sampai dengan 0.0035 kg/m 2 .s Selain itu, pembekuan awal dengan melakukan pendinginan internal dapat mencegah terjadinya penguapan sampai dengan 0.47g dan mempercepat transformasinya menjadi padatan.

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Comparison of quasi-steady-state and unsteady-state formulations in a freeze dryer modeling

2014

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An unsteady-state model is developed for primary and secondary stages of freeze drying process of skim milk. The results are compared with those obtained from a quasi-steady-state (QSS) formulation. The QSS formulation is not valid where the applied heat load is high. The applied heat load affects on the drying time the most compared to other parameters like chamber pressure and the radiation surface temperature. List of symbolsC p Heat capacities C Concentration (kg/m 3 ) c Weight fraction of internal water h Sample thickness (m) H Position of interface (m) k 2 , k 4 Self diffusivity constant (m 2 /s) k 1 , k 3 Bulk diffusivity constant (m 2 /s) k Thermal conductivity (kW/m K) f (T z ) Water vapor pressure-temperature functional form (N/m 2 ) DH sub Heat of sublimation of ice (kJ/kg) q Density (kg/m 3 ) K g Internal mass transfer coefficient (s) M Molecular weight m s Weight of dry solid N Mass flux (kg/m 2 s) N t Total flux (N t = N w ? N in ) P Partial pressure (N/m 2 ) P°Partial pressure of water vapor at z = 0 (N/m 2 ) q Heat flux at the bottom of the vial (kW/m 2 ) R Universal gas constant S Vial surface area (m 2 ) t Time (s) T Temperature (K) V Velocity of interface (m/s) V totVolume of the sample X Weight fraction of total moisture (dry basis) z Sample length coordinateGreek letters a Thermal diffusivity e Porosity r Stefan-Boltzmann constant q Density (kg/m 3 )

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Modeling and simulation of parametric sensitivity in primary freeze-drying of foodstuffs

Cited by 26 publications

References 9 publications

Freeze-drying microscopy in mathematical modeling of a biomaterial freeze-drying

Freeze-drying microscopy in mathematical modeling of a biomaterial freeze-drying

Characteristics of Vacuum Freeze Drying with Utilization of Internal Cooling and Condenser Waste Heat for Sublimation

Comparison of quasi-steady-state and unsteady-state formulations in a freeze dryer modeling

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