Mapping of temperature distribution in pharmaceutical microwave vacuum drying

Kelen, Akos; Ress, S.; Nagy, Tibor; Pallai, E.; Pintye‐Hódi, Klára

doi:10.1016/j.powtec.2005.12.001

Cited by 40 publications

(24 citation statements)

References 10 publications

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“…Cavity effects are due to design limitation, location of the microwave inlet point, shape of the cavity, and hanging parts such as mixer, which are sometimes used for stirring the product to ensure more uniform electromagnetic field distribution. Workload interactions include loss factor, penetration depth, thickness, shape, and size of the product that are different from product to product (Kelen et al 2006).…”

Section: Major Problems In Microwave Heatingmentioning

confidence: 99%

Non-uniform Temperature Distribution During Microwave Heating of Food Materials—A Review

Vadivambal

Jayas

2008

Food Bioprocess Technol

425

186

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Use of microwaves has increased largely in the domestic household in the last few decades due to the convenience of using microwave ovens. In the industrial sector, microwave processing is used in some of the unit operations, while it is yet to capture a major place in the industrial applications. The major drawback associated with microwave heating is the non-uniform temperature distribution, resulting in hot and cold spots in the heated product. The non-uniform temperature distribution not only affects the quality of the food but also raises the issue of food safety when the microorganisms may not be destroyed in the cold spots. The temperature distribution during microwave heating has been studied in a wide variety of products by several researchers. This paper summarizes their results and the solutions offered by them to lessen the nonuniformity of heating. The current applications of microwave energy in the industrial sector are also highlighted.

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Section: Major Problems In Microwave Heatingmentioning

confidence: 99%

Non-uniform Temperature Distribution During Microwave Heating of Food Materials—A Review

Vadivambal

Jayas

2008

Food Bioprocess Technol

425

186

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“…Hot spot occurrence is influenced by the electromagnetic and thermodynamic features of the microwave system and the workload. 19 Hotter areas of solid materials are cooled by heat diffusion to the surrounding material that is dependent of the thermal diffusivity and temperature gradient. 19 Taking into account that with higher saccharide masses the temperature increases due to reduced heat diffusion and heat convection, a reflection of the electromagnetic wave from the phase boundary can occur, generating localized hot spots inside the material.…”

Section: Influence Of Sample Massmentioning

confidence: 99%

“…[16][17][18][19][20][21][22][23] However, despite the widespread use, microwave drying has not been used up to now as a tool to speed up the LOD determination in saccharides. Considering that LOD is performed routinely the use of microwaves could reduce the time of analysis allowing fast response regarding to the quality of sample.…”

Section: Introductionmentioning

confidence: 99%

“…19 Hotter areas of solid materials are cooled by heat diffusion to the surrounding material that is dependent of the thermal diffusivity and temperature gradient. 19 Taking into account that with higher saccharide masses the temperature increases due to reduced heat diffusion and heat convection, a reflection of the electromagnetic wave from the phase boundary can occur, generating localized hot spots inside the material. 27,34,35 However, it is important to point out that hot spot phenomenon was observed in this work only for sample masses higher than those recommended in the respective pharmaceutical monograph.…”

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confidence: 99%

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A fast microwave-assisted procedure for loss on drying determination in saccharides

Bizzi

Barin

Hermes

et al. 2011

J. Braz. Chem. Soc.

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Um procedimento rápido para determinação de perda por dessecação (LOD) foi desenvolvido empregando aquecimento por radiação micro-ondas. Amostras de sacarídeos foram utilizadas e diferentes parâmetros foram avaliados, tais como a posição da amostra na cavidade do micro-ondas, massa de amostra e tempo de irradiação. Massas de amostra de 1 g e tempo de irradiação entre 15 e 25 min foram suficientes para a determinação da perda por dessecação de todos sacarídeos. Os resultados obtidos para perda por dessecação assistida por micro-ondas (MALOD) foram comparados com os resultados obtidos por LOD convencional em estufa e não apresentaram diferença significativa. O tempo de análise foi reduzido de 2,4 a 15 vezes, quando comparado ao sistema convencional de LOD e o desvio padrão relativo das medidas foi inferior a 1%. Até 16 amostras podem ser processadas simultaneamente, tornando o procedimento MALOD apropriado para análise de rotina.A fast procedure for loss on drying (LOD) determination was developed using microwave radiation. Samples of commercial saccharides were dried and the influence of sample position inside the microwave cavity, sample mass and irradiation time were evaluated. Sample mass of 1 g and irradiation time between 15 to 25 min were enough to LOD determination for all saccharides. Results obtained using the proposed microwave-assisted loss on drying (MALOD) procedure were compared with those obtained by conventional LOD determination using an oven and no statistical difference was found among results of these techniques. Using MALOD procedure the relative standard deviation was below 1%. The time for analysis was reduced from 2.4 to 15 times when compared to conventional LOD determination and up to 16 samples could be simultaneously processed making MALOD procedure suitable for routine analysis.Keywords: loss on drying, saccharides, microwave, food and pharmaceutical samples IntroductionLoss on drying (LOD) determination is a parameter often evaluated to access the quality of products. Several applications of LOD can be found in industry, in special for food and pharmaceutical industries, which currently use LOD to determine the amount of volatile matter (in general, water) that is driven off under specific conditions. 1-3 The LOD determination is relatively simple to be performed and results with relatively good precision can be obtained resulting in a widespread use. For example, in the 30 th edition of The United States Pharmacopeia more than one thousand monographs recommended the use of LOD in their tests that makes it a parameter that must be routinely evaluated in current quality control. 4 The procedures recommended for LOD determination can be performed at different conditions of drying such as pressure (atmospheric or vacuum) and temperature (with or without heating). [1][2][3] In some cases, the use of a desiccant to help the drying process (e.g. diphosphorus pentoxide) is recommended, Bizzi et al. 377 Vol. 22, No. 2, 2011 specially for mild drying conditions used for samples that can...

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“…Mapping temperature distribution had also been used to investigate the pharmaceutical microwave vacuum drying was performed by Kelen et al 23 When drying of extremely fragile corn starch-based granules (6.3kg) was carried out under vacuum (50T5 mbar) and accelerated by microwaves (1.2kW, 2450MHz) in a single/one pot unit (Collette Ultima 25l; a high-shear granulator that incorporates vacuum and microwave drying options), local burning was experienced after 25min of microwave heating. In the case of dielectric heating the location and temperature of hot spots are unpredictable, because of many factors, which influence the uniformity of the E-field.…”

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confidence: 99%

Thermography, A New Approach in Food Science Studies: A Review

Samanian

Mohebbi

2016

MOJFPT

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Background: Thermography can be defined as a process of writing or printing involving the use of heat. It's a technique for detecting and measuring variations in the heat emitted by various regions of the body and transforming them into visible signals that can be recorded photographically. Clearly it would be of great use in diagnosing abnormal or diseased underlying conditions. But in the recent years it has been suggested as a viable method in food science research both in detection and process control. Scope and approach:We reviewed thermography as a not new method which has recently found its way into vast areas of research and practice. After discussing its history and fundamentals some practical applications of thermography such as medical, agricultural and quality control are presented. But the main focus of review is laid on its usage in food science and technology, which is provided in two main categories of process control and detection, through a series of case studies. Key findings and conclusion:Thermography is a non invasive, non destructive and instantaneous method that makes dynamic observations feasible. It also can be used to confirm any slight gradient in temperature, suggesting it as a detection method. The most important drawback to method is being highly. Modification of the method to make it into a practical procedure in industry, heat and mass transfer studies and microbiological studies can be possible future concerns of the method.

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Mapping of temperature distribution in pharmaceutical microwave vacuum drying

Cited by 40 publications

References 10 publications

Non-uniform Temperature Distribution During Microwave Heating of Food Materials—A Review

Non-uniform Temperature Distribution During Microwave Heating of Food Materials—A Review

A fast microwave-assisted procedure for loss on drying determination in saccharides

Thermography, A New Approach in Food Science Studies: A Review

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