Influência do tratamento térmico e do pH na produção do doce de leite: determinação de 5-hidroximetilfurfural (HMF) livre e desenvolvido

Abstract

This study aimed to investigate the effects of thermal treatment and pH on the production of dulce de leche, with a focus on the formation of compounds derived from the Maillard Reaction and on the physicochemical and rheological properties of the final product. Formulations were prepared and subjected to different heating times (0 to 55 minutes at 121.1 °C), with F0 values calculated for each treatment. HMF (5- hydroxymethylfurfural), the main marker of the Maillard Reaction, was evaluated in two forms: free HMF, directly quantified by HPLC in freshly produced samples, and developed HMF, obtained by reheating the samples at 90 °C for up to 3 hours. The analyses showed that free HMF follows an exponential formation trend with increasing F0, reaching a stationary phase. The evaluation of developed HMF revealed that there is still significant potential for further formation of this compound even after thermal processing, which supports the use of the term “developed” instead of the traditional “total.” Additionally, physicochemical data indicated that thermal treatment directly influenced the reduction in pH, the increase in titratable acidity, and the release of ionic calcium into the soluble phase, demonstrating the disintegration of casein micelles under more intense heating conditions. Color parameters, evaluated by CIE-Lab colorimetry and UV-Vis spectrophotometry, showed progressive darkening related to the formation of melanoidins, with this effect being more pronounced during processing than throughout shelf life. Finally, rheological analyses fitted to the Herschel-Bulkley model confirmed the pseudoplastic behavior of the samples, with the most intensely heated products exhibiting higher yield stress, greater consistency, and lower flow behavior index, with variations in apparent viscosity suggesting relevant structural changes. The results provide valuable insight into the thermal effects on dulce de leche quality and propose a new conceptual approach for evaluating HMF in thermally processed foods.