Along with Rahel's watch, Mammachi's pickle factory can be viewed as another symbol of the freezing of time. The whole purpose of pickling and preserving is to take something with a short shelf life and make it last basically forever. (Or at least until you open the jar and eat what's inside.) It might seem like kind of a stretch to compare, let's say, Sophie Mol to a jar of banana jam, but it doesn't seem to be an accident that the family is in the preservation business. The preservation and persistence of certain memories is central to the novel, and having a pickle factory as a focal point of the house in Ayemenem serves as a constant reminder of this.