2.4. Surface pH determination
The surface pH of the pork was measured both before the pork chops
were placed inside the vacuum-package (initial) and before microbiological
analysis (Thermo Scientific Orion 8135BN ROSS Flat surface pH
probe, Beverly, MA; Jenco 6230 N Meter, San Diego, CA). The pH
meter was calibrated using 4.0 and 7.0 phosphate buffers (do I need to
add temperature here? They were calibrated at 4 °C). The surface pH
of each pork chop was measured three times, obtaining at least one
measurement from each side of the pork chop. All measurements for
pork chops of the same vacuum-package were averaged to obtain a
pre-package pH and for a post-package pH, all pH measurements of
the same vacuum-package taken after the package was opened were
averaged.