Development of a Quality Control Method for Raw Cow Milk Using Gas Chromatography - Ion Mobility Spectrometry and Gas Sensor Measurements

A quality monitoring method using gas chromatography –ion mobility spectrometry (GC-IMS) was developed. The results were used to implement a sensor-based quality control system for raw cow milk samples on dairy farms. The system is based on a commercial sensor system (Odor Checker Spot, OCS). GC-IMS was used to establish a profile of characteristic volatile organic compounds (VOCs) found within the headspace of raw milk samples, where the relative heights of 25 peaks corresponding to 13 VOCs were further transformed and reduced to the first principal component, using principal component analysis (PCA). 93% of all milk samples were classified correctly by PCA into either "good / fresh" or "bad / deteriorated" classes. Subsequently, the first principle component was transferred to a quality scoring system, which was used to train the OCS The OCS was able to evaluate raw milk samples and score their quality by grades, based on the GC-IMS reference measurements. Unknown samples could also been evaluated. These scores were in agreement with reference measurements at the GC-IMS.