Quantificação de proteínas em suplementos alimentares à base de soro de leite empregando colorimetria e imagens digitais

Abstract

This dissertation have had as main objective the development and validation of a robust, selective and low cost analytical method associated with easy-access instrumentation to perform protein quantification in whey-based food supplements. The methodology used was based on the capture of digital images using a Motorola G6 smartphone camera. Data analysis was carried out using the PhotoMetrixPRO application, in which the images captured by the smartphone camera were transformed into an analytical signal by the application, in a scenario designed for this purpose. The Biuret method was applied to determine the proteins in the protein supplement samples, causing the formation of violet tones in the reacted solution, the intensity of staining varied according to the concentration of proteins present in the studied samples. The total volume, percentage of the reagent and the distance from the smartphone camera to the analysis plate were parameters studied in the optimization of the proposed method, which used the Central Composite Design (CCD) experimental planning, evaluated by the Design-Expert software. The validation of the method took place through the following figures of merit: Matrix/selectivity effect, linearity, precision (repeatability and intermediate precision), limit of detection (LOD), limit of quantification (LOQ), accuracy and robustness. During the validation of the method, it proved to be linear, precise, selective and robust. The linear range was studied at concentrations from 2 to 10 mg.mL-1. The results obtained by the method were compared with the conventional method by UV-Vis spectrophotometry indicating accuracy and adequate protein values to those declared on the product labels. In this way, the method demonstrated an excellent performance in the analysis with speed, simplicity and low cost, and can be reliably used in the determination of proteins in isolated and hydrolyzed supplements based on whey, thus presenting numerous advantages over conventional methods and adaptation to the principles of green chemistry.