Purificacion y actividad de la pepsina de pollo / Purification and assay of chicken pepsin

The proteolitic enzyme pepsin (EC 3.4.23.1) was purified from chicken stomach by a modification of the method of Bohak (1970): after homogenazing the raw material, the zymogen was extracted with NaCl and NaHCO3, activated with 3N HCl and precipitated with NaCl (28 per cent final concentration). The precipitate was lyophilised; fractions of it were suspended in 0.02N HCl. The solution was filtered through a column (2.6 x 80 cm) of Sephadex G-100 at an elution rate of 8-10 ml x cm-2 x h-1. Two protein peaks were obtained, the first one corresponding to the pepsin (2.0 mg/ml in pooled fractions). The milk clotting activity of the enzyme was determined on skimmed milk as a substrate (Berridge, 1955). Its proteolitic activity on the artificial substrate N-acetyl-L-phenylalanyl-L-3, 5-diiodo tyrosin (APD) also was determined (Rick-Fritsch, 1974). Mean clotting activity value was 5.52 UC, higher (P < 0.01) than that of the reference chymosin (0.64 UC). The activity with APD was unsatisfactory, due to very high absorbance values of the blanks. It is concluded, that the purification steps followed in this trial are simple and rapid, conferring a strong stimulus to using chicken pepsin as a clotting agent for the industrial production of pasteurized white cheese.

Extracción de la pepsina aviar (EC 3.423.1) y su utilización como substituto de la quimosina en la elaboración de queso blanco pasteurizado / Extraction of avian pepsin (EC 3.423.1) its utilization as chymosin substitute when the making white pasteurized cheese

Se extrajo pepsina aviar a partir de estómagos glandulares de aves, para ser utilizada como substituto de la quimosina en a elaboración de queso blanco pasteurizado. La enzima extraida demostró poseer un rendimiento de 4,3 g de pepsina aviar liofilizada por cada kilogramo de estómagos glandulares, y una actividad coagulante, sobre el substrato de Berridge, ocho veces superior a la quimosina utilizada como patrón de referencia. No se encontraron diferencias significativas en la composición química ni en la calidad organoléptica de los quesos fabricados, cuando se utilizó pepsina aviar, quimosina aviar, quimosina y la mezcla de ambos. Demostrándose que la substitución, tanto parcial como total, de la quimosina por la pepsina en queso blanco pasteurizado es factible, ya que ofrece una mayor actividad coagulante y un queso con características químicas y sensoriales similares a las obtenidas con el cuajo tradicional