Estudo da influência de diferentes estabilizantes na estrutura coloidal de leite desnatado

Abstract

This doctoral thesis primarily aimed to investigate the effects of adding different calcium chelating salts (stabilizing salts) on the physicochemical properties and colloidal structure of skimmed milk. The work was structured in two chapters addressing fundamental aspects for the dairy industry. In the first chapter, we evaluated the influence of calcium sequestrant salts permitted and not permitted by Brazilian legislation for UHT milk. Sodium citrate and various sodium ortho- and polyphosphates were tested at five distinct concentrations (0.00, 0.05, 0.10, 0.15 and 0.20% w.w-1 ). Samples underwent heat treatment in an oil bath at 155°C (F₀ = 1.43 minutes), followed by rapid cooling and physicochemical analyses. Results demonstrated that tetrasodium diphosphate (TSP) and sodium triphosphate (STP) at 0.15% and 0.20% w.w-1 concentrations promoted the most significant changes in the colloidal system, with marked pH increase, high calcium sequestration capacity, and reduced heat coagulation time. Furthermore, these salts significantly altered particle size distribution and Ca²⁺ equilibrium at pH 4.0, showing that salt concentration directly influences the observed changes. The second chapter focused on comparing calcium sequestrant salts formed by different cations (Na⁺ and K⁺). We evaluated two sodium phosphates (disodium phosphate - DSP and trisodium phosphate - TSP) and their potassium analogs (dipotassium phosphate - DKP and tripotassium phosphate - TKP), with trisodium citrate as control. Replacing sodium with potassium ions did not significantly alter parameters such as pH, calcium sequestration capacity or heat coagulation time. However, tripotassium phosphate (TKP) at concentrations from 0.10% w.w-1 caused significant changes in particle size distribution profile, suggesting that K⁺ ions interact differently with proteins compared to Na⁺ ions. In conclusion, this thesis provides important contributions to understanding the interactions between calcium sequestrant salts and the milk matrix. The results may offer technical support for the industry to optimize processes and formulations, aligning technological innovation with regulatory requirements and market demands.