This study investigated the influence of chitosan (CH) and hydroxypropyl methylcellulose (H), along with ultrasound power, on the physicochemical properties, antifungal activity, and stability of oil-in-water (O/W) nanoemulsions containing thymol and cinnamaldehyde in a 7:3 (v/v) ratio. Eight O/W formulations were prepared using CH, H, and a 1:1 (v/v) blend of CH and H, both with and without ultrasonication (U). Compared to untreated samples, U-treated nanoemulsions had lower droplet sizes (433-301 nm), polydispersity index (0.42-0.47), and zeta potential (-0.42-0.77 mV). The U treatment decreased L* and b* values, increased a* color attribute values, and increased apparent viscosity (0.26-2.17) at the same shear rate. After 28 days, microbiological testing of nanoemulsions treated with U showed counts below the detection limits (< 2 log CFU mL-1). The U-treated nanoemulsions exhibited stronger antifungal effects against R. stolonifer, with the NE/CH-U and NE/CH-H-U formulations demonstrating the lowest minimum inhibitory and fungicidal concentrations, measured at 0.12 and 0.24 μL/mL, respectively. On day 28, U-treated nanoemulsions demonstrated higher ionic, thermal, and physical stability than untreated samples. These findings suggest that the stability and antifungal efficacy of polysaccharide-based nanoemulsions may be improved by ultrasonic treatment. This study paves the way for innovative, highly stable nanoemulsions.
This study examines the in vitro antifungal properties and in vivo efficacy of thymol-cinnamaldehyde (TH-CIN) loaded nanocapsules, prepared using chitosan (CH) and hydroxypropyl methylcellulose (H) with varying ultrasonic power (200-600 W), for controlling Rhizopus stolonifer in papaya. Ultrasonic power notably influenced the nanocapsules' antifungal properties, both in vitro and in vivo. Higher ultrasonic power resulted in improved antifungal activity, with NC-CH-400 and NC-CH-H-600 formulations achieving the highest inhibition zones (94.67 % and 93.33 %, respectively) against R. stolonifer in vitro. The Minimum Inhibitory Concentration (MIC) for CH formulations was 6.25 mg/mL, while the Minimum Fungicidal Concentration (MFC) for all formulations was 50 mg/mL. Protein leakage assays demonstrated significant disruption of R. stolonifer cell membranes, with NC-CH-400 and NC-CH-H-600 at MFC reducing intracellular protein concentrations by over 95 %. In vivo tests showed that NC-CH-400 nanocapsule-coated papayas, whether sprayed or dipped, reduced weight loss to 0.54 % and 0.86 %, respectively, and exhibited lower decay severity indices, particularly during storage. Spraying was more effective than dipping in preventing decay. Peel color analysis revealed that coated fruits maintained acceptable ripeness levels over 10 days, indicating delayed maturation. Coated fruits also exhibited better color consistency and were preferred in sensory evaluations for improved taste, aroma, color, and texture, particularly with NC-CH-400 and NC-CH-H-600 coatings.