CHITOSAN MICROPARTICLES OBTAINED BY ULTRASONICATION FOR USE AS AN EDIBLE COATING

Chitosan is a biocompatible, biodegradable, antimicrobial, and non-toxic material with diverse functional and biological properties. The use of these particles at the micro or nanoscale enhances the optimization of their functional properties, such as antimicrobial and antioxidant activity. Developing simple and accessible production processes for microscale chitosan structures will enable their broader application in the industry. Therefore, this study aimed to develop chitosan microparticles for subsequent application as an edible coating, particularly for meat products. A Central Composite Rotational Design (CCRD) was employed to optimize the production of microparticles, using a 2² factorial design with two independent variables: amplitude (ranging from 20% to 80%) and sonication time (from 5 to 30 minutes), totaling 11 experimental trial. For each trial, 2 grams of chitosan were dissolved in 25 mL of 10% acetic acid solution for 2 hours. Subsequently, 25 mL of a 1% tripolyphosphate solution was added. The samples were then subjected to ultrasonic treatment (Qsonica Sonicator) according to the proposed CCRD conditions. The average hydrodynamic diameter was determined by Dynamic Light Scattering (DLS) at 25°C, using a laser incidence angle of 173°, on a Zetasizer Nano ZS particle analyzer (Malvern Instruments). The viscosity was evaluated using a rotational rheometer (LM200, Lamy Rheology) at a shear rate of 50 s⁻¹ for 1 minute. Color parameters were measured using a Konica Minolta CM-5 colorimeter under D65 illumination, 10° observer angle, in liquid mode, in CIELAB color space. The parameters analyzed included L*, a*, b*, chroma (C*), and hue angle (h), as well as gloss, opacity, dominant wavelength, and excitation purity. Although it was not possible to adjust a predictive model for particle size (p > 0.10), the measured sizes ranged from 2563 nm to 10440 nm, with the smallest particles obtained at 71% amplitude for 8 minutes. Viscosity ranged from 2.13 Pa·s (80% amplitude for 17 min) to 44.15 Pa·s (50% amplitude for 5 min), indicating that shorter sonication times result in higher sample viscosity. Statistical models were successfully fitted for the color parameters L*, a*, b*, C*, h*, and gloss. The desirability function (100%) indicated that the optimal conditions for obtaining brighter (L* = 78.84) and glossier (44.07) samples were 80% amplitude and 6.5 minutes of sonication. Therefore, the production of chitosan microparticles was successfully optimized, yelding improved visual Properties and demostrating considerable potential for application as an edible coating.