When filling canned food products in the food sector, if the product is filled with liquid and filling liquid, the volume expands during the sterilization stage and the wall of the box is forced. In this case, there is not enough vacuum in the box. Therefore, a space must be left at the top of the can during filling. This gap is called the net head gap in the sector. The head space is left to compensate for the expansion of the products in the box during the heat treatment step.

This amount of space varies depending on the type of food to be placed in the box, or depending on the size and shape of the can. In the sterilization phase, the head space must be higher for the products that swell by taking water and increase the volume. In addition, the pressure in the sterilization stage forces the body and the walls of the can, since the flexibility of the lid is not high in long and thin canisters. This percentage must also be higher than the headroom in these boxes. The larger the volume of the can, the larger the amount of head space.

According to general applications, a top space of 5-10 is left in the canister up to a percentage of its volume. In other words, the filling rate in canned cans should be between 90-95 at most. In addition, the head space in glass jars to be sterilized between 115-121 degrees cannot be less than 6 percent of the container volume.

If the filling rate is above the appropriate ratio, the can can explode due to excessive pressure and vacuum, or the box is deformed. On the contrary, if the filling rate is low, this time the octic acid and the wear are seen in the box due to excess air.

In authorized laboratories, generally accepted test methods and test criteria are applied in the filling rate (percentage) determination studies. In terms of the reliability and impartiality of the analysis results, laboratories comply with the standards issued by domestic and foreign organizations.