A method and a device can be used for setting vacuum time in a packaging apparatus and in a packaging process. The method and device provide for determining, from pressure signals or from humidity signals detected in the vacuum chamber, a reference time instant. The method and device also provide for commanding a vacuum device either to stop extracting gas from the vacuum chamber or to execute one or more prescribed steps preluding to end of the vacuum cycle at expiration of a delay time interval following said reference time instant.