Behavior of α- and β-cyclodextrin-encapsulated allyl isothiocyanate as slow-release additives in polylactide-co-polycaprolactone films

The natural antibacterial agent allyl isothiocyanate (AITC) encapsulated in either alpha- or beta-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 (TGAMS) were used to explore the thermal properties of CD-encapsulated 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 P-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 beta-CD than to alpha-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 beta-CD complex of AITC in PLA-PCL films but not when incorporating the alpha-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. (C) 2007 Wiley Periodicals, Inc.