Abstract: An opening/closing system, particularly for packaging bags, of the type that includes a planar base part defining at least in part an opening through itself, this base part includes guide means parallel to the opening and engaging with guide means belonging to a slider designed to close the opening or leave it open, which system is characterized in that, before the system is used for the first time, the opening is closed at least partly by a layer of material, and in that the slider includes a cursor directed toward the opening and capable of at least partly destroying the layer of material to open the opening when the slider is moved for the first time.

Abstract: System for opening/closing a packaging bag, comprising an opening formed in one of its walls, delimited by edges of this wall. Furthermore, this system comprises a flat base piece at least partially delimiting an opening through it and comprising the two longitudinal elements intended to be connected to the bag, this base piece thus being able to accommodate the slider and being intended to be fixed to the wall of the bag in such a way that the opening that it delimits coincides with the opening made in the wall of the bag.

Abstract: System for opening/closing a packaging bag, comprising an opening formed in one of its walls, delimited by edges of this wall. Furthermore, this system comprises a flat base piece at least partially delimiting an opening through it and comprising the two longitudinal elements intended to be connected to the bag, this base piece thus being able to accommodate the slider and being intended to be fixed to the wall of the bag in such a way that the opening that it delimits coincides with the opening made in the wall of the bag.

Abstract: This invention relates to a process for selectively separating the alpha-lactalbumin from the proteins of whey; the process comprises a heat treatment of the whey previously concentrated to a dry matter content of 10 to 40% by weight, and acidified to a pH of less than 4, preferably from 3 to 3.5, said heat treatment being carried out at a temperature not exceeding 75.degree. C., preferably from 45.degree. to 75.degree. C., for a duration of 15 seconds to 1 hour so as selectively to precipitate the alpha-lactalbumin; this heat treatment is followed by the recovery of the alpha-lactalbumin in the form of a precipitate and possibly of the other lacto-proteins remaining in solution in the residual whey. The process presents the advantage of being simple to carry out and being of low cost.