Antibacterial properties of edible coatings from chitosan and young coconut shell liquid smoke

Abstract

Abstract Liquid smoke-based edible coatings have garnered considerable attention in the food processing and post-harvest industry due to their environmentally friendly attributes and their ability to extend the shelf life of perishable goods. This study investigates the antimicrobial efficacy of edible coatings formulated using chitosan and young coconut shell liquid smoke against both gram-negative bacteria (Escherichia coli and Salmonella typhimurium) and gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus). The liquid smoke was produced via the pyrolysis of young coconut shells at temperatures of 300 (T1), 340 (T2), 380 (T3) and 420ºC (T4). The edible coatings were prepared by blending 2% (v/w) liquid smoke with varying chitosan concentrations of 0.5 % (Ch 0.5), 1% (Ch 1) and 1.5% (Ch 1.5). Antibacterial activity assessments were conducted using the disc diffusion method (Kirby Bauer). The findings reveal that the antibacterial efficacy of the edible coatings against each bacterial strain is influenced by both the pyrolysis temperature and the concentration of chitosan employed. Liquid smoke derived from T4 pyrolysis exhibited the highest inhibitory potential, except for Bacillus subtilis. Notably, the most pronounced antimicrobial activity against Salmonella typhimurium was observed with the T4Ch1.5 edible coating. Specifically, at T4Ch1.5, the inhibitory zones for Escherichia coli, Salmonella typhimurium, Bacillus subtilis, and Staphylococcus aureus were measured at 7.65 mm, 8.30 mm, 7.55 mm, and 7.23 mm, respectively. The results underscore the promise of edible coatings comprising a combination of chitosan and young coconut shell liquid smoke as potential candidates for preserving food and agricultural products, offering both protection and antibacterial properties.