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Start Over Descriptor "mass-transfer" Journal journal of food engineering
3 results on '"mass-transfer"'

1. Effect of boldo (Peumus boldus M.) pretreatment on kinetics of supercritical CO2 extraction of essential oil

Author

Uquiche, Edgar, Huerta, Elizabeth, Sandoval, Alicia, and del Valle, José Manuel

Subjects
*CHEMICAL kinetics, *SUPERCRITICAL fluid extraction, *CARBON dioxide, *ESSENTIAL oils, *FOOD chemistry, *EFFECT of temperature on food, *LOW temperatures
Abstract

Abstract: This work examined the effect of the solid matrix on supercritical carbon dioxide (SC CO2) extraction of essentials oils from boldo leaves (Peumus boldus M.) subjected to rapid decompression of a CO2-impregnated sample, conventional milling, and low-temperature milling. Low-temperature conditioning prior to milling decreased heat-driven losses of volatile compounds during milling, as attested by a higher extract yield for low-temperature (10.8g extract/kg extract-free substrate) than conventionally (9.63g/kg) milled sample. Extract yield was even larger for the rapidly decompressed sample (11.4g/kg). Results of SC CO2 extraction experiments carried out at 40°C and 10MPa were adjusted to a diffusional model using the effective diffusivity of the extract in the solid matrix (D e) and a single partition of essential oils between solid substrate and SC CO2 as best-fitting parameters. A microstructural factor (F M), which was estimated as the ratio between the binary diffusion coefficient of the essential oil in SC-CO2 under extraction conditions and D e, was used to characterize the effect of sample pretreatment on extraction rates. Values of F M for rapidly decompressed (202) and low-temperature milled (1740) samples were smaller than value for conventionally milled samples (2200), which revealed that the two first treatments disrupted secretory cavities in boldo leaves more effectively than the third. This was confirmed by light microscopy observations. The work included also measurements using oregano bracts (Origanum vulgare L.) as the substrate to confirm literature reports on the SC CO2 extraction of pretreated bracts and to serve as a reference to our main results with boldo leaves. Trends with oregano coincided with those of boldo. [Copyright &y& Elsevier]

Published
2012
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2. Evaluation of a chicory root cold store humidification system using computational fluid dynamics

Author

Herman Ramon, Bart Nicolai, Pieter Verboven, Ann Schenk, and Mulugeta Admasu Delele

Subjects
Materials science, Meteorology, multiphase flow, Nozzle, Airflow, Cold storage, mass-transfer, humidification, porous media, Stack (abstract data type), macroscopic turbulence model, Deposition (phase transition), Relative humidity, bulk, Composite material, cfd, porous-media, parameters, cfd model, relative-humidity, Humidity, temperature storage, cold storage, chicory root, lagrangian model, Room air distribution, movement, air-flow, Food Science
Abstract

Humidification of chicory root cold stores helps in maintaining the quality and extending the postharvest storage time of chicory roots. Low evaporation rate of the sprayed droplets at such sub-zero temperatures (-2 degrees C to -1 degrees C) favours surface deposition that could have an adverse effect on the efficiency of the storage room. A three-dimensional computational fluid dynamics (CFD) model was developed and used to predict the storage room air velocity, temperature and humidity distributions, and fate of the water droplets that were sprayed for humidifying the storage room. The humidification system in a chicory root cold store was then optimized. The efficiency of the humidification system was affected by length of cold air deflector, stack height, number of nozzles and duration of humidification. Elongating the air deflector, reducing the stack height, reducing the number of nozzles and shortening the humidification time increased the amount of droplet evaporated and decreased the amount of droplet deposited on the stack. The following combinations of room design and operating parameters could clearly give the best performance of the humidification system: deflector length of 0.8 m, two nozzles with an interval humidification of 1.5 min on and 2 min off cycle and stack height of 3.4 m. (C) 2009 Elsevier Ltd. All rights reserved. ispartof: Journal of food engineering vol:94 issue:1 pages:110-121 status: published

Published
2009

3. Concentration of aqueous extracts of defatted soy flour by ultrafiltration; Effect of suspended particles on the filtration flux

Subjects
cross-flow, layer, Leerstoelgroep Productontwerpen en kwaliteitskunde, food and beverages, mass-transfer, convection promotion, Product Design and Quality Management Group, membrane, VLAG
Abstract

Suspended particles can have a positive effect on the flux and concentration curve of soy flour extracts during ultrafiltration. This is described by a simple empirical model. The suspended particles in this study were insoluble milled bean material (mean particle size 25 m). It is shown that it is possible to concentrate soy extracts to a much higher final concentration with an acceptable flux. The suspended particles are able to clean the membrane by a scouring mechanism. They have a positive effect on the reversibility of fouling.

Published
2003

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