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

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.

Size press practices and formulations affecting paper properties and process efficiency: A Review

“…An innovative technology has been demonstrated by which natural oils, or other hydrophobic monomeric compounds, can be incorporated into a specialty paper product, possibly allowing their gradual release over time (Aguado et al 2022). This was achieved by crosslinking of the starch with cyclodextrin, taking advantage of the hydrophobic character of the interior of that ring-like saccharide.…”

“…One of the main purposes of a crosslinking agent can be to prevent resolubilization of some kind of an aqueous coating if it happens to get wet again later. Crosslinkers for use in size press formulations have been mentioned by several researchers (Trouve and Takala 1993;Li et al 2022;Fei et al 2011;Li et al 2012;Wang et al 2015a;Wang et al 2018;Liu et al 2021;Aguado et al 2022;Li et al 2022). There is a lot of variation within the reagents and approaches in the group of citations.…”

“…In addition, crosslinking can be used as a way to build up the molecular weight of some sort of copolymer in preparation for its later usage at a size press (Li et al 2012;Li et al 2022). In another case, the researchers used crosslinking to make sure that cyclodextrin, the purpose of which was to collect oil, was not subject to later detachment from the paper (Aguado et al 2022).…”