Food quality is greatly dependent on the security of the food packaging process，which has been widely developed to inhibit food spoilage and to prolong the shelf life for food products. Gas in scattering media absorption spectroscopy is used as an optical noninvasive method to estimate the gas content in food packages. A diode laser with central wavelength of 760 nm is used to record an oxygen spectroscopic signal, and then to estimate the oxygen content by investigating the gas exchange in the package. The experimental results show that the technique can be used to determine the oxygen concentration and to assure the integrity and security of food packages.