Use of electronic nose for corn silage screening

Corn silages were randomly collected in the Po valley during the year 2012. Samples were taken from 18 concrete wall bunkers and from 3 different positions of freshly cut face: core or C, (1 meter high from the bottom), side or S (1.5 meter high from the bottom, 0.3 meter from the walls) and top or T (0.5 meter from the top). Collected samples were stored at 4 °C and subjected within 24 h to electronic nose analysis (Pen3 – Airsense AnalyticsGmbH, Schwerin, Germany) equipped with metal oxide semiconductor sensors (W1C, W3C, W6S, W5C, W1S, W1W, W2S, W2W, W3S). Each sample was weighed (20 g) into airtight glass jar, then jars were closed and let it stand at room temperature for 30 minutes to allow for headspace equilibrium. After reaching equilibrium, the headspace gas was pumped to sensors of the electronic nose (flow rate 400 ml/min). The measurement phase lasted 60 seconds with data collection interval of 1 second. A stand-by phase (320 seconds) was observed between each sample reading to allow for a cleaning of the system. Only one reading (at 59 second) for each sensor entered a data matrix of 54 rows (silage samples) and 9 columns (sensors). A correlation matrix was obtained from collected data and a principal component analysis (PCA) was performed using the FACTOR procedure of SAS. The PRIN method with Kaiser’s criterion (eigenvalue≥1.00) and the orthogonal Varimax rotation were used to extract latent constructs and to produce loading vectors and sample scores. Three principal components (PC) were extracted: PC1 (W1C, W3C, W5C, W1S, W2S, W2W; eigenvalue=5.60), PC2 (W6S, W3S; eigenvalue=1.75), PC3 (W1W; eigenvalue=1.00). The PC1 allowed for clustering the silage samples into two populations being C and S+T, whereas the PC2 and PC3 tended to discriminate between S and T samples. Results suggest electronic nose could be a valuable laboratory tool for discriminating corn silages exposed to different preservation