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Revista mexicana de ingeniería química

Print version ISSN 1665-2738

Rev. Mex. Ing. Quím vol.7 n.2 Ciudad de México Aug. 2008

 

Ingeniería de alimentos

 

Variaciones del contenido de humedad por efecto de congelado a temperaturas de criogenia

 

Variations in water content due to freezing at cryogenic temperatures

 

L.L. Méndez–Lagunas1*, J. Rodríguez–Ramírez1 y M. Y. García–Cortes2

 

1 CIIDIR IPN U. Oaxaca, Hornos 1003 Sta. Cruz Xoxocotlan, Oax. Mexico, C.P.71230. * Autora para la correspondencia. E–mail: lmendezla@ipn.mx. Tel. (951)51–70400 ext 82726

2 Universidad Tecnológica de la Mixteca, Carr. a Acatlima Km. 2.5 Huajuapan de León, Oax., México C.P. 69000

 

Recibido 27 de Noviembre 2007
Aceptado 7 de Agosto 2008

 

Resumen

Las variaciones de contenido de humedad por efecto del congelamiento a temperaturas de criogenia fueron evaluadas en el transcurso de una cinética de secado de ajo. Las condiciones de secado fueron temperaturas constantes de 40°C, 50°C y 60°C con un flujo de aire de 1.8 m/s. Las muestras frescas, secas y en el transcurso de secado fueron congeladas con nitrógeno líquido antes de la determinación de contenido de humedad. Como referencia, muestras no congeladas fueron monitoreadas al mismo tiempo.

Durante las cinéticas de secado, las muestras sometidas a congelamiento por criogenia varían entre 0 y 70% en su contenido de humedad en relación a las no tratadas con criogenia. Estos valores contrastan con los encontrados en muestras completamente secas o totalmente frescas que fue de 0.55 y 1.17 % respectivamente. Los resultados sugieren que los diversos fenómenos que ocurren durante el congelamiento a temperaturas de criogenia, dependen principalmente del contenido de humedad del material antes de someterse a este proceso. Estas variaciones son muy importantes si se realizan correcciones de la humedad base seca de determinaciones fisicoquímicas en el transcurso de procesos de conservación (ej. secado) pero afectan poco cuando estas correcciones se efectúan en determinaciones sobre muestras frescas o totalmente secas.

Palabras clave: determinaciones fisicoquímicas, criogenia, contenido de humedad.

 

Abstract

Variations in water content owing to freezing at cryogenic temperatures were evaluated in the kinetic drying process of garlic. The drying conditions were constant temperatures of 40°C, 50°C and 60°C with an airflow of 1.8m/s. Samples of garlic that were fresh, dry, and in the process of drying were frozen in liquid nitrogen before determining their water content. As a reference, samples that were not frozen were monitored at the same time. During the kinetic drying, the samples subjected to cryogenic freezing varied from 0 to 70% in water content compared to those not cryogenically treated. These resultants contrast with those found in wholly dried or wholly fresh samples, which showed a difference of 0.55 and 1.17% respectively.

The results suggest that the diverse phenomena which occur during freezing at cryogenic temperatures depend principally on the water content of the material before it is subjected to this process.

These variations are highly important if correcting this difference in the dry base water content of physical chemical tests in the process of preservation (e.g. drying), but have little effect when these changes are made in tests with fresh or wholly dried samples.

Keywords: food analysis, cryogenic, water content.

 

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Agradecimientos

Se agradece a la COFAA–IPN por los apoyos otorgados a los autores y al financiamiento del proyecto SIP–20060155. Así mismo se dan las gracias a Frank M. León Martínez y a Juan D. Vela Santiago por la asistencia técnica en este trabajo.

 

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