RESUMO
In the study, the effects of nitrate and/or nitrite (150 mg/kg KNO3, 300 mg/kg KNO3, 150 mg/kg NaNO2, and 150 mg/kg KNO3 + 150 mg/kg NaNO2) on proteolytic changes (free amino acid composition, SDS-PAGE) in pastirma were investigated. Pastirma samples were also analyzed in terms of some qualitative (pH, aw, TBARS, residual nitrite, salt) properties. The lowest total free amino acid content (1818.3 mg/ 100 g DM) was observed in the combination of 150 mg/kg KNO3 + 150 mg/kg NaNO2, while the highest content (2847.49 mg/ 100 g DM) was observed in 150 mg/kg KNO3. Although the pastirma groups generally exhibited similar SDS-PAGE profiles, differences were detected at some band intensities. The lowest TBARS value (22.24 µmol MDA/kg) was observed in 150 mg/kg KNO3 + 150 mg/kg NaNO2. As a result, the use of 150 mg/kg KNO3 in the pastirma curing process causes more intense proteolysis.
RESUMO
Moisture desorption isotherms of beef were determined in the relative humidity range of 23 to 90% at 5, 15 and 25°C and at 2.5% NaCl and 2.5% NaCl+150 ppm NaNO(2) content. Desorption isotherms were found to be typical type II sigmoid. The water content at equilibrium was higher in beef with NaCl and NaCl+NaNO(2) than control samples. Experimental data were fitted to various mathematical models and it was found that the Peleg model was best in describing the equilibrium moisture content relationship for beef samples over the entire range of temperatures. The net isosteric heat of sorption was estimated from equilibrium desorption data, using the Clausius-Clapeyron equation. Isosteric heats of desorption were found to increase with decreasing moisture content.