Efeitos de aditivos na concentração por congelamento de soro de leite bovino

Abstract

This work aimed to concentrate by freezing-concentration bovine whey (SLB) from cheese enzymatic coagulation as a pre-processing stage to obtain the freeze-dried powdered product. In this process, the effects of ethanol (C2H5OH), calcium chloride (CaCl2) and Carboxymethylcellulose (CMC) added with different concentrations on physical-chemical, rheological parameters and temperature profiles in the SLB freezing-concentration process by freezing were evaluated. The complete process was carried out in three stages and the fractions were evaluated at the end of each stage. A composite central rotational planning (CCRD) was used to evaluate the effects of additives on the response variables that were the percentage variations in density, lactose content, total soluble solids (TSS) content and protein content calculated in relation to a standard SLB sample. The Hue angle and pH values were also measured. Temperature records during the concentration process were obtained using a data acquisition system and rheological parameters, consistency index (k) and flow behavior index (n) were obtained by fitting the experimental data as to the power law model. The results of regression analysis by response surface methodology showed that the effects of ethanol, CaCl2 and CMC addition were significant (p < 0.05) on percentage variations in density, lactose content, total soluble solids content and protein content, and were less significant for Hue angle and not significant for pH. The number of stages influenced the concentration process. In the “concentrate” fraction, the largest variations in density (3.35), lactose content (6.40), SST content (4.60) and protein content (3.15) were found in the treatment consisting of 10% ethanol, 0.5% CaCl2 and 0.05% CMC. The results were supported by the analysis of the subcooling levels and initial freezing temperatures obtained from the temperature profiles and by the increase in viscosities of the "concentrated" and "ice crystals" fractions analyzed using the rheological parameters k and n. All SLB samples showed pseudoplastic behavior.