Development and preliminary field validation of water-resistant cellulose nanofiber based coatings with high surface adhesion and elasticity for reducing cherry rain-cracking

• CFN coating for preventing cherry rain-cracking was developed and validated.
• Amount of surfactant in coating was a critical factor affecting coating performance.
• CNF coating containing glycerol and surfactant had high wettability and elasticity.
• CNF coating reduced cherry rain-cracking without detrimental effect on fruit quality.

This study was aimed to systematically develop and validate cellulose nanofiber (CNF)-based hydrophobic coatings (Innofresh™) for reducing cherry rain-cracking through a lab-scale optimization study and the preliminary field validation trials. The base coating formulation consist of 0.5% CNF (w/w) and 0.5% potassium sorbate (KSb) (w/w). For optimizing the coating formulations with desired water resistance, wettability and elasticity, three different types of plasticizer (glycerol, PEG 400, and sorbitol) and their concentrations (0, 0.05, and 0.1% (w/w)), as well as surfactant mixture (1:1 ratio of Tween 80 and Span 80) at 0.05, 0.1, and 0.2% (w/w) were evaluated as additional functional substances in the base coating formulation. It was found that 0.5% CNF/0.5% KSb based coatings containing 0.1% glycerol and 0.1% or 0.2% surfactant mixture provided high wettability and elasticity along with superior water resistance. The effectiveness of the optimized coating formulations on reducing cherry rain-cracking was validated through two field studies conducted in Chile and the United States during November–December, 2014 and May–June, 2015, respectively. The 0.5% CNF/0.5% KSb/0.1% glycerol coating containing 0.1% or 0.2% surfactant mixture resulted in significant reduction in cherry rain-cracking (∼31.18–44.60%) (P < 0.05), while no any detrimental effect on fruit firmness, size, soluble sugar, pedicel/fruit retention force, and color was observed in comparison with non-coated cherries. Therefore, the simple, but versatile CNF-based coatings incorporated with an appropriate amount of glycerol and surfactant was effective to reduce cherry rain-cracking without impacting fruit growth and quality.