Apparent density

The mass of a porous material divided by its total volume — solids plus the air spaces within. Because voids contribute volume without mass, apparent density is always lower than the true density of the material’s constituents. Food engineers measure it routinely for powders, extruded snacks, freeze-dried products and baked goods: it predicts how much fits in a package, how a powder flows and rehydrates, how crisp a snack feels, and what transport costs. A airy loaf crumb and a dense energy bar differ largely in apparent density. It is also a process control parameter, flagging deviations in extrusion, drying or fermentation.