EFFECT OF GLUCOSE-CITRIC ACID BASED NATURAL DEEP EUTECTIC SOLVENT (NADES) ON FLEXIBLE FILMS FROM BABASSU MESOCARP FLOUR

Babassu mesocarp flour (BMF) contains 60 to 90% starch and can be used to develop biobased films. NADES are green solvents that can be added to films as plasticizing agents to improve mechanical properties and bioactivity. This study aimed to produce and characterize glucose-citric acid NADES and evaluate their effects on the mechanical and optical properties of BMF films. Two NADES (GLU-CIT20, GLU-CIT30) were prepared with glucose- citric acid (1:1) plus 20% or 30% water under heating (60°C) and stirring (2 h). The NADES were characterized by pH (with pH strips), density (DMA 4500 digital density meter; Anton Paar), and viscosity (MCR301 rotational rheometer; Anton Paar) as a function of temperature. Antimicrobial activity was assessed by the disk diffusion method for Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli, and Salmonella sp. Films were prepared by casting with 4% BMF in water and NADES at 60%, 80%, or 100% of BMF: A) 60GLU-CIT20; B) 80GLU-CIT20; C) 100GLU-CIT20; D) 60GLU-CIT30; E) 80GLU-CIT30, and F) 100GLU-CIT30. Data were analyzed by ANOVA/Tukey's test (p<0.05). The pH of NADES remained acidic as the temperature increased (25 to 50°C). For density (g/cm³): GLU-CIT20 at 25°C (1.41±0.00001^a), GLU-CIT20 at 50°C (1.39±0.00001^b), GLU-CIT30 at 25°C (1.35±0.00001^c), GLU-CIT30 at 50°C (1.33±0.00001^d). For viscosity (Pa·s): GLU-CIT20 at 25°C (1.7±0.008^a), GLU-CIT20 at 50°C (0.223±0.0001^b), GLU-CIT30 at 25°C (0.218±0.0004^b), GLU-CIT30 at 50°C (0.061±0.005^c). Both NADES showed an exponential decrease in viscosity with increasing temperature and antimicrobial activity against all bacteria, with inhibition zones from 9 mm. For the mechanical properties of the films, thickness values (mm) were: A (0.117±0.01^c), B (0.150±0.01^a), C (0.153±0.01^a), D (0.128±0.01^bc), E (0.135±0.01^b) and F (0.132±0.01^b). Tensile strength (TS; MPa): A (9.75±1.8^a), B (4.72±0.4 ^c), C (2.12±0.2^d), D (9.27±1.7^a), E (6.83±1.3^b) and F (2.16±0.4^d). Elongation at break (EB; %): A (9,8±5.2^c), B (34.7±9.7^b), C (53.12±4.7^a), D (1.69±0.5^c), E (29.37±6.0^b) and F (56.27±6.6^a). Young's modulus (YM; MPa): A (435.77±53.5^a), B (67.67±3.0^c), C (3.71±0.5^d), D (462.99±39.9^a), E (213.55±19.4^b) and F (3.49±0.15^d). Film B was the reddest and film A the least. Films A and F were the most yellowish, while film C was the most bluish. All films showed similar Chroma Index about 51. GLU-CIT acted as a plasticizer while providing antimicrobial activity. Films with 100% GLU-CIT20 or GLU-CIT30 were more flexible and non-brittle, indicating improved starch polymer network formation. These films represent promising alternatives for food packaging.