Acoustic monitoring of eye formation in Swiss type cheese

In Swiss type cheese ripening, eye formation is one of the most important parameters to assure quality of the product. Eye formation depends on milk type, temperature, moisture, initial inoculum, among other factors. Occurrence of eye formation and time when eyes appear may be experimentally determined. However, non-destructive determination of eyes is a difficult task due to the heterogeneous nature and high attenuation of Swiss type cheese. In this work, we present an acoustic technique to detect eye formation and monitor the ripening process of Swiss type cheese. The proposed technique is based on the evolution of the Fourier spectrum during ripening. The response is measured in the opposite side of the cheese wheels. Eight cheese wheels were monitored during 30 days by registering acoustic measurements every two days. One wheel was cut every five days to take reference measurements. Three frequency bands were identified and analyzed in the energy density and in the first order momentum of the spectrum. The reference method consisted in qualitative evaluation of eyes distribution using photographs of the cut wheels. Results shows that acoustic techniques allow to detect the time eyes appear and are consistent with qualitative evaluation of images of cheese halves.