Amino-acid determination In the protein concentrates of mackerel horse obtained at different pH, the aminoacid content was determinated to check up the influence of the Na OH attack. We have used the thin-layer chromatography technique and two-dimensional separation on Merck microcrystalline cellulose plate (400 u slit width). The quantitative deterrnination was done by transimission densitometry in a densitometer VITATRON TLD. 100/Hg. We can see the differences in the solubility of protein concentrates obtained by alkaline methods at pH = 8,5; 10,5 and 12,3 before and after removal with isopropyl alcohol at room temperature. In every case, the least solubility is in the range of pH = 4,5-5,5. However this solubility increases remarkably in the protein concentrate samples extracted with isopropyl alcohol. The least viscosity values, the same as with the solubility are found between pH = 4,5-5,5. We sum up the correspondent values to the rehydration of the protein concentrates previously trated with isopropyl alcohol to extract the oil. The least rehydration is, in the three products, between pH = 5-6. It is reported the emulsion of the concentrate, obtained with a previous alkaline treatment at pH = 12,3. The other two products, obtained at pH = 10,5 and 8,5, lack of emulsion capacity. We sum up the results of the amino-acid content in the different protein concentrates obtained by alkaline attack, at pH = 12,3; 10,5 and 8,5, before and after being extracted with isopropyl alcohol. There are not remarkable variations in the samples analized for what we can conclude that the different alkaline attacks used in our experiences have not influence on the amino-acid content of the protein concentrate

[EN] The obtainment of fish protein concentrate, by alkaline method and later acid precipitation is used in the industry. In this paper, we study the influence of the alkaline attack with Na OH, so as pH, temperature and attack time on the final characteristics of the protein concentrate. These characteristics are: amino acid content, functional properties, solubility, capacity. viscosity and rehydration, all them with great industrial interest to determinate the market price of a fish protein concentrate. We have used as raw material mackerel horse (Trachurus trachurus, L.) plenty and low-price species in Spain. The minced fish was blended with water at proportion 1 : 8, adding 0,25 N NaOH solution to get the different pH selected in our study. In every case the alkaline attack was made in thermostatic bath at 90º C during a variable time according to the pH of the sample. When the alkaline attack was finished, we separate by centrifugation part of the fat, bones and solid rests, and the protein contained in the liquid phase was precipited with 0.25 ClH at pH = 4.5. It was centrifuged again to separate the fat of the precipited protein, which was dried at 60º C. Finally the residual fat in the protein concentrate is removed with isopropyl alcohol and it is dried to obtain the final product

[ES] La obtención de concentrado de proteína de pescado por el método alcalino, debido a sus condiciones de fabricación, es un procedimiento empleado frecuentemente por la industria. En trabajos anteriores nos hemos ocupado de este método, para concretar las condiciones más idóneas que conducen a un producto final de mejor calidad, LÓPEZ-BENITO, GIL y PASTORIZA (19761. El objeto de este trabajo, se centra en el estudio de la influencia del tratamiento alcalino, pH, temperatura y tiempo de ataque, sobre las características finales del concentrado de proteína obtenido. Estas características son: el contenido de aminoácidos, las propiedades funcionales y la composición química, todos ellos factores de gran interés para la industria, por ser determinantes del precio a que se cotiza en el mercado el concentrado de proteína de pescado

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