Highlights

• First study on the effects of concentration & layering on shellac coating performance
• 100-fold improved O2 barrier of bagasse paperboard (BP) with 2-layer, 40 % shellac coating.
• 40- & 5-fold improved H2O resistance & barrier of BP with 2-layer, 40 % shellac coating.
• Improved thermal resistance of BP with 2-layer, 40 % shellac coating
• 50-Day increase in potato chip shelf life by coating BP with 2 layers of 40 % shellac.

Abstract

Fiber-based packaging is a sustainable approach for food packaging. To maintain biodegradability and economic viability, coatings used for improving barrier properties of fiber-based materials should be environmentally friendly, biodegradable and inexpensive. Shellac, a natural and biodegradable polyacid resin with good film-forming properties and hydrophobicity, has been widely studied as a film, however, information on shellac as coating for fiber-based materials is limited to its blend with additives or biopolymers and its application as a single layer. This study investigated the effects of shellac layer number and concentration on shellac-coated bagasse paperboard (BP) properties pertinent to food packaging applications. Shellac solution at different concentrations (24, 40, 60 %) was applied on BP in differing numbers of layers (1–4) using the bar coating technique. The different shellac-coated BPs were characterized for water vapor permeability (WVP), oxygen permeability (OP), water absorbency (Cobb60), thickness, coating weight, chemical structure, morphology, and mechanical and thermal properties. The results showed that the BP coated with two 40 % shellac-layers (0.03 mm and 9.6 % in dry weigh) had the lowest WVP (1.3 × 10⁻¹² kg m m⁻² s⁻¹ Pa⁻¹), OP (3.8 × 10⁻¹⁴ kg m m⁻² s⁻¹ Pa⁻¹), and Cobb60 (0.004 g m⁻²) resulting in an 82.2 %, 99.5 %, and 97.5 % improvement in water barrier, oxygen barrier, and resistance to absorb water over the uncoated BP. This shellac coating also improved the thermal resistance of BP and did not affect its mechanical properties. Therefore, the interplay between shellac layer number and concentration can improve the properties of shellac-coated BP and thus, the performance of BP for food packaging as demonstrated by food shelf-life simulation.

Read the full paper via sciencedirect.com