This study examined the physicochemical and mechanical properties of edible composite films made of cellulose nanofiber (CNF) and shellac (Sh). All films were conditioned at 25℃ and 53% relative humidity (RH) for at least 48 h before analyses. Increasing the Sh ratio from 0% to 100% resulted in an increase in film thickness from 57.8 μm to 71.1 μm, while opacity decreased significantly from 22.3 mm⁻¹ to 3.7 mm⁻¹. With the increase in the Sh ratio, the moisture content, water solubility, and swelling of the film increased from 9.7% to 35.1%, 4.9% to 100%, and 3.0% to 10.5%, respectively. The CNF film (0% Sh) exhibited a lower water contact angle than the films with 80% and 100% Sh, but it was more water-resistant. As the Sh ratio increased, the tensile strength, yield stress, Young’s modulus, and work of break of the films decreased significantly from 17.9 MPa to 0.3 MPa, 1.00 MPa to 0.38 MPa, 220.7 MPa to 0.9 MPa, and 0.67 MJ/m3 to 0.13 MJ/m3, respectively. Conversely, the elongation at break increased dramatically from 10% to 253%. This study demonstrated that the thickness, opacity, moisture-related properties, and mechanical properties of CNF-Sh composite films could be tailored by varying the biopolymer ratio.

Abstract
Introduction
Materials and Methods
    Materials
    Preparation of CNF-Sh composite films
    Thickness
    Opacity
    Moisture content
    Water solubility
    Swelling
    Contact angle
    Mechanical properties
    Statistical analysis
Results and Discussion
    Thickness of CNF-Sh composite films
    Opacity of CNF-Sh composite films
    Moisture content, solubility and swelling ofCNF-Sh composite films
    Contact angle of CNF-Sh composite films
    Mechanical properties of CNF-Sh composite films
Conclusion
References

• Dong Hoon Kim(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea)
• Hyo Jin Kim(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea, Institute of Food Industrialization, Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang 25354, Korea)
• Donghwa Chung(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea, Institute of Food Industrialization, Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang 25354, Korea) Corresponding author
• Hee Chung(Institute of Food Industrialization, Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang 25354, Korea)
• Won-Ki Min(Department of Food Science and Industry, Kyungil University, Gyeongsan 38428, Korea)