As previously indicated, initial pH values of the growth substrates were 7.28 (TBS),5.64 (fat-lean homogenate) and 5.72 (ground beef). After storage (168h), the pH of or substrates stored at 4 °c remained relatively unchanged (date not shown). The pH values of the substrates after storage (168h) at 15c were 6.11 to 6.12 (TSB), 6.36 to 6.39 (fat-lean homogenate) and 5.57 to 5.61 (ground beef)