Crosslinking of surface-sizing starch with cyclodextrin units enhances the performance of paper as essential oil carrier

Abstract

Abstract We present a feasible method to produce coated papers with long-lasting presence of natural active compounds. First, the composition of essential oils from Eucalyptus globulus was analyzed by gas chromatography-mass spectrometry (GC-MS), revealing high proportions of eucalyptol (73 %) and α-pinene (15 %) in the case of the leaves, and sesquiterpenoids like globulol and epiglobulol (55 %) for the wood essential oil. These compounds were incorporated onto paper sheets by conventional coating processes, using surface starch as binder. Nonetheless, the main source of novelty lies in the functionalization of starch with β-cyclodextrin by two-step esterification, resulting in enhanced binding capabilities. Release to air was evaluated by headspace-solid phase microextraction, using a divinylbenzene/Carboxen/polydimethylsiloxane fiber, whose adsorbates were analyzed by GC-MS. One week after coating a paper sheet with native starch and essential oil from E. globulus, terpineol, eucalyptol and pinene were below the limit of detection. The insertion of cyclodextrin moieties improved the protection of the most volatile active compounds from fast evaporation. Likewise, cyclodextrin units enhanced the preservation of antioxidant activity, but the weak scavenging potential of E. globulus essential oils was the limiting factor. In this sense, promising results were obtained by replacing said essential oil with hydroxytyrosol.