Antifungal effect of active sticker coated with hydroxypropyl methylcellulose combining waxes and essential oil and its application on butter cake

• Novel active sticker papers were developed to inhibit mold growth in packaged butter cake. The active sticker papers were coated with formulations containing hydroxypropyl methylcellulose (HPMC), clove essential oil (CEO), and a hydrophobic agent—either beeswax (BW) or carnauba wax (CW). • Two coating method were used: a single-layer coating (HPMC+BW, HPMC+CW, HPMC+BW+CEO, and HPMC+CW+CEO) and a double-layer coating (HPMC+CEO/BW, HPMC+CEO/CW, HPMC/BW+CEO, and HPMC/CW+CEO), designed to control the release and functionality of the active components. • In both in vitro and in vivo assays, the CEO-containing papers demonstrated significant antifungal activity, effectively inhibiting the growth of key spoilage molds ( Aspergillus flavus and Rhizopus stolonifera ). • The double-layer coating markedly improved the paper's physical properties: it enhanced water resistance by reducing water vapor transmission rate (WVTR) and water absorption, while simultaneously increasing tear resistance. This study developed an active sticker to inhibit mold growth on butter cake using coatings of hydroxypropyl methylcellulose (HPMC), carnauba wax (CW) or beeswax (BW), and clove essential oil (CEO). Single layer (HPMC+BW, HPMC+CW, HPMC+BW+CEO, HPMC+CW+CEO) and double layer coatings (HPMC+CEO/BW, HPMC+CEO/CW, HPMC/BW+CEO, HPMC/CW+CEO) were applied on sticker papers and evaluated for their properties, including structural and thermal characterization, surface morphology, physical properties, water resistance, and antifungal efficacy. Double layer with beeswax coatings exhibited better adhesion to the paper, without cracking. All CEO-containing coating formulations effectively inhibited Rhizopus stolonifera and Aspergillus flavus . Based on this, large (4.5×6.0 cm) and small (4.5×3.0 cm) sizes of papers coated with HPMC+BW+CEO and HPMC/BW+CEO were selected for in-package testing with butter cake by adhering the coated sticker paper inside PET containers. The large piece of double layer HPMC/BW+CEO coating provided the best mold suppression on butter cake, a result directly correlated with its greater CEO release profile. The active sticker did not alter cake texture, however, it led to a noticeable reduction in sensory scores for odor, taste, and overall acceptance compared to the control. Analysis of water resistance properties (water vapor transmission rate, water absorption, and contact angle) confirmed that double layer coatings provided significantly better water resistance than single layer coatings and uncoated paper. The HPMC/BW+CEO coated paper is identified as a promising candidate for extending the shelf life of the butter cake industry. This active sticker acts as a biocontrol for reduction in food waste, supporting a better environment and health.