There are a number of emerging rapid non-destructive methods for chemical grouping of foods such as the direct injection mass spectrometric techniques (DIMS), atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) (Davies, Linforth, Wilkinson, NLG919 Smart, & Cook, 2011), proton transfer reaction mass spectrometry (PTR-MS) (Biasioli, Yeretzian, Gasperi, & Mark, 2011) and selected ion flow tube mass spectrometry (SIFT-MS) (Langford et al., 2012) have gained the attention of the researchers working in the field
for classification and authenticity, due to their ability to perform real time non-invasive analysis with high sensitivity and limited sample pre-treatment. PTR in combination with a time-of-flight mass spectrometer (PTR-ToF-MS) have been extensively used for classification studies of a broad range of food products including PDO cheese, olive oil and dry cured hams, intact fruits and their derivatives (Aprea et al., 2006, Biasioli et al., 2003, Cappellin et al., 2012, Del Pulgar et al., 2011 and Galle et al., 2011). In these cases, classification typically uses the data matrix resulting
from the entire mass spectrum (spectral fingerprint) and statistical treatment to identify clusters, trends or correlations, appropriate data mining techniques may C59 wnt include partial least squares discriminant analysis (PLS-DA), K-nearest neighbours (KNN), soft independent modelling of class analogies (SIMCA) (Fisk, Virdie, Kenny, & Ullrich, 2010) support vector machine (SVM) and random forest (RF) (Cappellin et al., 2012). Whist direct injection mass spectrometric techniques are rapid and information rich, gas phase chemometric classification approaches should always take into consideration
the availability of volatile compounds in the gas-phase and the equilibrium concentration difference between the product and its gas phase. The chemical potential of a volatile component is dependent Methane monooxygenase firstly on the physicochemical properties of the analyte, the physical structure of the matrix (Yang et al., 2012 and Yu et al., 2012), the presence of multiple phases (Fernández-Vázquez et al., 2013 and Fisk et al., 2011) and chemical composition of the product being analysed (Fisk, Boyer, & Linforth, 2012). It is therefore important to consider that modifications to the product non-volatile composition may have a significant impact on the aroma profile and therefore where appropriate, standardisations should be applied.