In this study, we investigated the effects of aging treatment on the physicochemical, mechanical, and barrier properties of edible composite films prepared from shellac (Sh) and cellulose nanofiber (CNF) with different blending ratios. Sh–CNF films (0%, 20%, and 50% CNF) were fabricated and subjected to aging for 7 days at 40°C and 53% relative humidity. Film thickness was found to decline with both CNF incorporation and aging, whereas there were corresponding increases in opacity, particularly in Sh-rich films. In addition, the moisture content and water solubility of films declined at higher CNF ratios, and aging contributed to further reductions in moisture content, although had no significant effects on water solubility. Color analysis revealed that aging promoted the yellowing of pure Sh films, whereas the addition of CNF mitigated these changes. The findings of mechanical analysis revealed that CNF enhanced tensile strength, yield stress, Young’s modulus, and work of break, although reduced elongation at break. Aging contributed to further enhancements of strength and stiffness, along with a reduction in flexibility, although the magnitude of change diminished at higher CNF contents. Furthermore, the findings of gas barrier analysis indicated that CNF was associated with reductions in oxygen permeability, although promoted increases in water vapor permeability, with aging having the opposite effects. Collectively, these findings revealed that the functional properties of Sh–CNF films can be tailored via controlled aging and blending, thereby highlighting the potential utility of these films as edible packaging materials.

Abstract
Introduction
Materials and Methods
    Materials
    Preparation of Sh-CNF dispersions and compositefilms
    Aging of Sh-CNF composite films
    Thickness measurements
    Opacity measurements
    Moisture content measurements
    Water solubility measurements
    Color measurements
    Mechanical property measurements
    Water vapor permeability measurements
    Oxygen permeability measurements
    Statistical analysis
Results and Discussion
    Effects of aging on thickness and opacity
    Effects of aging on moisture content and watersolubility
    Effects of aging on color
    Effects of aging on mechanical properties
    Effects of aging on moisture and oxygen barrierproperties
Conclusion
References

• Dong Hoon Kim(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea)
• Yohan Song(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea)
• Gunhyung Park(Food Technology Major, Graduate School of International Agricultural Technology, Seoul National University, Pyeongchang 25354, Korea)
• Huin Lee(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)