Abstract: A bag of plastic material for vacuum preservation of food comprises two rectangular walls joined together along three sides. The width of one of the walls is larger than the width of the other wall by a predetermined quantity, preferably about 5%.

Abstract: The bag is made from a polyethylene sheet and has a mouth with at least one sheath along its edge, the sheath containing an inextensible ribbon which is graspable from outside through a hole cut in the sheath, in order to close the bag after filling. An elastically extensible ribbon is fastened at its opposite ends to the material of the bag. When the bag is received in a rigid bin with its upper margin overturned over the bin rim, the elastic ribbon is pulled radially, looped and released around the overturn of the bag to clamp it around the bin.

Abstract: The bag consists of two walls made from sheets of a multi-layer, synthetic material, welded together along part of the perimeter. One of the walls has two or three rectilinear, longitudinal rough stripes on its inner surface, obtained by hot-printing and extending substantially along the full length of the bag. The stripes are obtained by pressing a welding bar, coated with a rough, non-adhesive material, such as teflon cloth, against the multi-layer sheet forming the wall of the bag.

Abstract: A film of a ribbon-shaped synthetic material is wound as a roll on a supporting core. At least one of the side edges of the film ribbon is incised with small cuts at right angles to said side edges, at spaced intervals along it.

Abstract: The bag is made from a polyethylene sheet and has a mouth with at least one sheath along its edge, the sheath containing an inextensible ribbon which is graspable from outside through a hole cut in the sheath, in order to close the bag after filling. An elastically extensible ribbon is fastened at its opposite ends to the material of the bag. When the bag is received in a rigid bin with its upper margin overturned over the bin rim, the elastic ribbon is pulled radially, looped and released around the overturn of the bag to clamp it around the bin.