3.2. pH, water activity, moisture, and fat content changes
The average pH value of uncooked 10 and 18% pump rate beef samples are 5.90 and 6.01, respectively (Table 2). Following cooking to endpoint temperatures of 55–71.1 °C, the pH of the beef samples increases to 6.04–6.09 and 6.13–6.16 in 10 and 18% pump rate beef samples, respectively (P < 0.05) ( Table 2). The pH increase in cooked beef is caused by a decrease in free acidic groups as meat temperatures increase (Lawrie & Ledward, 2006). The higher pH values in the 18% pump rate beef compared to the 10% samples (P < 0.05) has been shown to be a result of higher amounts of salt and sodium tripolyphosphate raising the net charge of the beef muscle ( Hedrick et al., 1994).