Se estudió la etapa de conversión de ácido algínico a alginato de sodio, en el proceso de producción de alginatos, a partir del alga café Macrocystis pyrifera, como materia prima. Se determinó el efecto del volumen de alcohol, la proporción de alcoholagua, el pH y el tiempo de tratamiento sobre el rendimiento y la viscosidad del alginato obtenido. Se experimentaron siete volúmenes de la mezcla alcohol-agua en proporción 50:50, de 9 a 15 mL g-1 de alga. El rendimiento y la viscosidad no fueron significativamente diferentes en ninguno de los volúmenes empleados, sin embargo, con el volumen de 9 mL g-1 de alga, la agitación no fue eficiente, por lo tanto el volumen mínimo a emplear en esta etapa fue de 10 mL g-1 de alga. La proporción apropiada de la mezcla alcohol-agua se determinó usando cinco proporciones: 50:50, 47:53, 44:56, 40:60 y 37:63. El mayor rendimiento y viscosidad se obtuvieron con la proporción 50:50. Se probaron cinco valores de pH de 6 hasta 10 para determinar el pH óptimo de la reacción de conversión. Los mejores resultados se obtuvieron utilizando un pH de 7 a 8 en la solución alcohólica de la etapa de conversión. Para determinar el tiempo mínimo requerido para la reacción de conversión, las fibras de alginato de sodio se mantuvieron en agitación en una solución alcohólica durante diferentes tiempos: 20, 30, 40, 50 y 60 minutos. El rendimiento y la viscosidad obtenidos no presentaron diferencias significativas, por lo tanto, el tiempo mínimo para llevar a cabo la reacción de conversión fue de 30 minutos, para asegurar una reacción completa. Se propone el uso de un mezclador doble planetario para llevar a cabo esta etapa a otro nivel.
The alkaline extraction step of the process to obtain sodium alginate from Macrocystu pyrifera was investigated. We compared cold (28°C) and hot (80°C) treatments to determine the effect of extraction temperature on the yield and viscosity of the final product, using samples collected in Bahia Tortugas, Baja California Sur (Mexico), in the summer of 1994. At 80°C we obtained a yield of 19.10% and a viscosity of 398 cps: at 28ºC the yield was 15.53% and the viscosity was 466 cps. We conclude that hot extraction is more favourable, because the yield is statistically greater and the viscosity is the same. The effect of extraction time was also investigated in the hot process, using samples collected in Bahia Tortugas in the fall of 1990, to determine the minimum extraction time in which we can obtain high yield and quality of the final product. We tested times from 90 to 165 minutes at 80°C. In the temperature range tested, no significant difference was found between the yields or the viscosity. We conclude that the minimum extraction time is 90 minutes; however, to reach the final reaction point, the time must be extended to 120 minutes.
Growth rates of Macrocystis pyrifera fronds were measured in a control and a harvested bed in Bahía Tortugas, BCS. Measurements were taken every third day for the tirst 15 days after tagging and once again after 100 days. Growth rate in the control bed, as a function of frond length, follows a logarithmic relation, with maximum values in winter and minimum in summer. This pattern was
An evaluation of Mactt~~stis pyrifem (L.) C. Agardh kelp beds was conducted during the winter of 1985-1986 along the westem coast of Baja California, by means of estimated canopy in four different locations along their distribution range, and the total area covered was measuredby means of aerial infrared photography. The distribution of the kelp beds extends from the United States border to Morro Hermoso, B.C.S., with an absence of kelp in Bahía Vizcafno, B.C. South of Morro Hermoso, B.C.S., recovery of the kelp beds has been slow after the "El Niño" phenomenon (1982-1983) due to competitive replacement by Eiseniu urbo~~a. In the winter of 19851986, coverage by the kelp beds measured 6,485,049m2 and the standing crep was 35,813.l tons 2 2,260 tons, with 40% in the northem and 60% in the southem areas.
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