MINAS FRESCAL CHEESE ELABORATED WITH THERMOSONICATED RAW MILK: ENGINEERING FACTORS, GROSS COMPOSITION, AND PHYSICAL PARAMETERS

Conventional thermal treatments, such as pasteurization, can ensure the safety of dairy foods, but their application can result in adverse effects such as nutrient degradation and sensory changes. Thermosonication (TS) is a nonconventional technology that combines heat with acoustic cavitation to improve microbial inactivation; however, there is still a gap in the knowledge about TS of raw milk for production of cheeses. Therefore, this study aimed to evaluate the influence of raw milk processing by TS (160, 400, and 640 W, 72-75 °C/10-15 s) on the manufacture of Minas Frescal cheese. Engineering factors (acoustic power, acoustic intensity, power density, specific energy, energy density) were determined for TS processing as well as gross composition ( moisture, protein, fat), optical (L, a,b, whiteness index WI) and rheological parameters (uniaxial compression). Cheeses using pasteurized (HTST) and raw milk (control) were also processed for comparative purposes. TS were faster (14.16, 9.16, and 9.16 min for TS160, TS400, and TS640, respectively) than HTST (17.5 min, p < 0.05) to achieve the processing temperature. Overall, TS may be an alternative to conventional pasteurization as shorter processing times (reduction of 47.5% for TS400 and TS640) may be achieved. Regards the engineering parameters,, heating rates values for TS160, TS400, and TS640 were 0.003, 0.013, and 0.03 °C s-1, while the other operational parameters were acoustic power of 3.93, 15.72, and 39.3 W; an acoustic intensity of 8.5, 33.8, and 84.6 W cm-2; power density of 0.01, 0.05 and 0.13 W cm-3; and specific energy of 11, 28.3 and 70.7 J g-1, in treatments TS160, TS400 and TS640, respectively. Finally, the energy density (ED) values were 0.45, 0.72 and 1.15 kJ cm-3 for TS160, TS400 and TS640, respectively. For the moisture content values, TS samples presented lower values and less variation between them (46.1 to 47.6% w/w, p < 0.05) compared to the HTST sample, which can be explained by the time x temperature profile of the treatments, in which TS treatments generated faster heating, which may cause a more significant loss of free water in the cheese. For protein and fat content, TS samples had the higher content (p < 0.05), which can be explained by the effect of TS on the particle size of proteins and the fat globules; for the former, increased surface hydrophobicity and exposure to buried sulfhydryl groups (located inside the protein), thus improving gelling properties. Optical parameters demonstrate TS had higher indices related to white color (p<0.05) when compared to the HTST sample. The related time of processing does not trigger the Maillard reaction. Related to rheological parameters, the fracture strain has presented a gradual decrease across HTST (0.651), TS160 (0.458), TS400 (0.404), and TS640 (0.373) samples (p < 0.05). Therefore, TS-treated samples showed higher brittleness than the other samples. Likewise, no significant differences among HTST or TS-treated samples were observed for the fracture stress (σ_f) (p > 0.05).