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Ultrasound-Assisted Preparation of Chitosan Oligosaccharide-Stabilized Thyme Oil-in-Water Nanoemulsions: Enhanced Storage Stability and Antimicrobial Properties

Summary

Researchers created tiny droplets of thyme oil mixed in water using sound waves and a natural stabilizer from shellfish shells. These droplets stayed stable for weeks without separating and worked twice as well at fighting bacteria and mold compared to regular thyme oil. The new formula could be used to keep fresh food from spoiling during storage.

Background

Thyme oil (TO) possesses potent antioxidant and antimicrobial properties but suffers from high volatility, hydrophobicity, and susceptibility to oxidation. Oil-in-water emulsions are effective delivery systems for essential oils, but face challenges with Ostwald ripening that compromise stability. This study addresses the need for stabilization methods that preserve antimicrobial efficacy without using ripening inhibitors.

Objective

To develop chitosan oligosaccharide (COS)-stabilized thyme oil-in-water nanoemulsions using ultrasound-assisted emulsification and evaluate their storage stability, encapsulation efficiency, and antimicrobial properties compared to free thyme oil.

Results

Ultrasonic treatment at 450 W for 10 minutes achieved droplet sizes below 240 nm with encapsulation efficiency exceeding 90%. The COS/CA interface layer and PVA effectively enhanced emulsion stability during 21-day storage. Encapsulated TO exhibited 1.25-fold higher ABTS and 1.33-fold higher DPPH radical scavenging activities compared to free TO. MIC values for emulsions were half those of free TO, with 2TO-E achieving 99.31% inhibition of P. italicum growth.

Conclusion

COS-stabilized thyme oil nanoemulsions represent an effective delivery system that simultaneously improves storage stability and antimicrobial efficacy without requiring ripening inhibitors. The emulsions maintained excellent physicochemical stability and demonstrated superior antioxidant and antimicrobial properties, making them promising candidates for applications in food preservation and active packaging.
  • Published in:Foods,
  • Study Type:Experimental Study,
  • Source: 10.3390/foods14172930; PMID: 40941046
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