The natural antibacterial agent allyl isothiocyanate (AITC) encapsulated in either a-or b-cyclodextrin (CD) has previously been evaluated as a slow-release additive in polylactide-co-polycaprolactone (PLA-PCL) films designed for use in cheese packaging. In the research described in this article, thermogravimetric analysis (TGA) and thermogravimetric analysis in tandem with mass spectrometry (TGA-MS) were used to explore the thermal properties of CDencapsulated AITC complexes as well as those of PLA-PCL films containing these complexes. To our knowledge, this is the first reported application of the TGA-MS technique to explore the thermal stability of CD-entrapped AITC and the first study to report differences in thermal stability of AITC in a-and b-CD cavities in the solid state. Observed differences in the thermal degradation profile of films containing the CD complexes can be explained if AITC binds more strongly to b-CD than to a-CD. This hypothesis has been reinforced by gas chromatography (GC) and high performance liquid chromatography (HPLC) studies, the results of which suggest that a new covalently bound AITC-CD complex may be formed when incorporating the b-CD complex of AITC in PLA-PCL films but not when incorporating the a-CD complex of AITC. This finding means that the a-CD complex of AITC would be preferred in situations where adequate longterm controlled release of AITC from polymer films is required, as for example in the case of active packaging applications.