Monitoring changes in the volatile profile of cheese crackers during storage using GC-MS and PTR-MS

The primary objective of this work was to determine the feasibility of using PTR-MS ion profiles to monitor changes in the volatile profile of cheese crackers during storage. This was done by obtaining PTR-MS ion profiles of cheese crackers during the early shelf-life of the product (first 4 months of storage) and comparing these data to those obtained using a more traditional approach, i.e. purge and trap-GC-MS (PT-GC-MS). The PTR-MS profile of the samples was monitored for 47 ion masses, mainly corresponding to low molecular weight compounds or fragments of low mass. From the application of multivariate statistical analysis (cluster analysis, PCA, ANOVA) to the PTR-MS data of the samples of different storage times, it was shown that the age of the sample was an important factor for their classification. It was possible to differentiate two main groups of samples, the first group included samples of age <3 months (1, 1.5 and 2 months). This group had low ion intensities relative to the second group. The second group comprised samples of age ≥3 months (3 and 4 months) that showed higher ion intensities. PT-GC-MS data on the same samples found 38 volatile compounds, primarily aldehydes, that increased during storage. A good correlation was found between changes in some PTR-MS masses and major volatile compounds of crackers. The compounds that increased were generally products of autoxidation. It appears that a PTR-MS could be a useful tool for monitoring volatile changes during storage in cheese crackers.