OLEIC ACID DETECTION BY COLORIMETRIC PENTACOSADINOIC ACID (PCDA) COLORIMETRIC NANOSENSOR: A PRELIMINARY APPROACH FOR APPLICATION IN BOVINE MILK

The lipid content in bovine milk, stored mainly in the form of triglycerides, is an important indicator of milk quality and directly affects its nutritional value, as it is responsible for transporting essential vitamins to the human body, including A, D, E, K, and in the production of dairy products. In this context, this study evaluated the use of a polydiacethylene (PDA)-based colorimetric nanosensor for the detection of fat content in synthetic samples of oleic acid, one of the main fatty acids in milk. Vesicles of 10-12 pentacosadinoic acid (PCDA) at 0.001 mol. L⁻¹ were dissolved in a 1% (w/w) aqueous solution of triblock copolymer (L64), sonicated (400 W) for 10 minutes, filtered (0.45 μm), refrigerated (12 h) and light-cured under UV light (254 nm) for 10 minutes to obtain blue vesicles, characterized in Zetasizer (Malvern Instruments Ltd) with mean hydrodynamic radius of (3.296 ± 0.523 nm) and Zeta potential (-22.10 ± 1.57 mV). Seven concentrations of the synthetic oleic acid sample (0 to 1,10.10⁻⁵ mol.mL⁻¹) were prepared in a solution of L64 at 2.2% (w/w), keeping the nanosensor volumes (0.0002 mol.mL⁻¹) and the samples fixed. The colorimetric response was evaluated by scanning spectrophotometry (300-700 nm) in a microplate reader (Synergy-HTX) and by color value (CV) analysis, from the extraction of the RGB values of the images corresponding to the assays by the ImageJ software