Preparation of Hydroxypropyl Methylcellulose-Fucoidan-Citral Nanoemulsion Composite Film: Characterization and Preservative Application in Ostrea rivularis Gould

Ostrea rivularis Gould ( O. rivularis ) is nutritionally rich oyster species highly perishable due to endogenous enzymatic activity and microbial proliferation. Currently, active packaging incorporating natural antimicrobials offers a promising approach to improve the quality and shelf-life of aquatic products. In this study, an active composite film (HPMC-FCD-CNE) was developed by incorporating citral nanoemulsion (CNE) into a hydroxypropyl methylcellulose (HPMC) and fucoidan (FCD) matrix. The film with 4% (v/v) CNE exhibited optimal mechanical and barrier properties alongside enhanced antioxidant and antibacterial activities. During refrigerated storage at 4 °C, oysters wrapped with the HPMC-FCD-CNE demonstrated a 4-day extension in shelf-life compared to unwrapped controls, with superior sensory acceptability and delayed quality deterioration, as indicated by reduced total volatile basic nitrogen (TVB-N), K value, and microbial counts. These findings highlight the potential of HPMC-FCD-CNE as an effective active packaging strategy to preserve oysters and other aquatic products under refrigeration.