Effect of selected Hofmeister salts on textural and rheological properties of nonfat cheese

Three Hofmeister salts (HS; sodium sulfate, sodium thiocyanate, and sodium chloride) were evaluated for their effect on the textural and rheological properties of nonfat cheese. Nonfat cheese, made by direct acidification, were sliced into discs (diameter = 50 mm, thickness = 2 mm) and incubated with agitation (6 h at 22°C) in 50 mL of a synthetic Cheddar cheese aqueous phase buffer (pH 5.4). The 3 HS were added at 5 concentrations (0.1, 0.25, 0.5, 0.75, and 1.0 M) to the buffer. Post-incubation, cheese slices were air dried and equilibrated in air-tight bags for 18 h at 5°C before analysis. Small amplitude oscillatory rheology properties, including the dynamic moduli and loss tangent, were measured during heating from 5 to 85°C. Hardness was determined by texture profile analysis. Acid-base buffering was performed to observe changes in the indigenous insoluble (colloidal) calcium phosphate (CCP). Moisture content decreased with increasing HS concentration. Cheeses incubated in high concentrations of SCN− softened earlier (i.e., loss tangent = 1) compared with other HS treatments. Higher melting temperature values were observed for cheeses incubated in high concentrations of SO42−. Hardness decreased in cheeses incubated in buffers with high concentrations of SCN−. The indigenous CCP profile of nonfat cheese was not greatly affected by incubation in Cl− or SCN−, whereas buffers with high concentrations of SO42− reduced the acid-base buffering contributed by CCP. The use of high concentrations (1.0 M) of SCN− for incubation of cheeses resulted in a softer protein matrix at high temperatures due to the chaotropic effect of SCN−, which weakened hydrophobic interactions between CN. Cheese samples incubated in 1.0 M SO42− buffers exhibited a stiffer protein matrix at high temperatures due to the kosmotropic effect of SO42−, which helped to strengthen hydrophobic interactions in the proteins during the heating step. This study showed that HS influenced the texture and rheology of nonfat cheese probably by altering the strength of hydrophobic interactions between CN.