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.
]]> Referencias
Adam N.R., Wall G.W. (2001). Multipropose cryogenic surface apparatus: A liquid nitrog–chilled sample tray. Crop Science 41,755–758. [ Links ]
Campañone L.A., Roche L.A., Salvadori V.O., Mascheroni R.H. (2002) Monitoring of Weight Losses in Meat Products during Freezing and Frozen Storage, Food Science and Technology International 8(4), 229–238. [ Links ]
Campañone L.A., Salvadori V.O., Mascheroni R.H. (2001) Weight loss during freezing and storage of unpackaged foods. Journal of Food Engineering 47, 69–79. [ Links ]
Campañone L.A., Salvadori V.O., Mascheroni R.H. (2005). Food freezing with simultaneous surface dehydration:approximate prediction of weight loss during freezing and storage. International Journal of Heat and Mass Transfer 48(6), 1195–1204. [ Links ]
Crafts–Brandner SB, Salvucci M.E. and Egli D.B. (1990). Changes in ribulosebisphosphate carboxylase/oxygenase and ribulose 5–phosphate kinase abundances and photosynthetic capacity during leaf senescence. Photosynthesis Research 23, 223–230. [ Links ]
Goral D. (2008). The effect different techniques of freezing and defrosting on the quality of spice vegetables after a long–term freezer storage, Electronic Journal of Polish Agricultural Universities 11(1), 1–15. [ Links ]
Hintse J. (2001) NCSS and PASS, Number Cruncher Satatistical Systems, Kaysuille, Utah. [ Links ]
Kellner K. y Scurlock R.G. (1971). Cryogenics and its applications. Review of Physics in Technology 2, 25–38. [ Links ]
Murthy C.T., Bhattacharya S. (2008). Cryogenic grinding of black pepper. Journal of Food Engineering 85, 18–28. [ Links ]
Rodríguez R. J. Méndez L.L., Martínez A.C , Fidel D.N. (2001). A closed loop tunnel for drying kinetics research Procceding of 2d. IADC, Veracruz, Mex., 499–504. [ Links ]
Sharkey T.D., Seemann J.R., Berry J.A. (1986). Regulation of ribulose–1,5 bisphosphate carboxylase activity in response to changing partial pressure of O2 and light in Phaseolus vulgaris. Plant Physiology 81,788–791. [ Links ]
Usada H., Shimogawara K. (1994). Induction of the inactivation and degradation of phosphoenol–pyruvate carboxylase and ribulose 1,5–bisphosphate carboxylase/ oxygenase in maize leaves by freezing and thawing. Plant Cell Physiology 35, 363–370. [ Links ]
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