M. longissimus thoracis et lumborum from 64 bull beef carcasses
were selected based on their pH values. The meat pH was measured
48 h post slaughter by inserting calibrated pH and temperature
probes (Mettler Toledo MP 125 pH meter with an Inlab 427 probe) directly
into the muscle/meat. Duplicate readings were taken for analysis
of each sample. Twelve of the samples were used for various
calibrations and trial runs and the remaining 52 samples ranging in
ultimate pH from 5.4 to 6.9 (Table 1) were vacuum packed and stored
in a −1.5 °C chiller until the freezing point analysis, which was carried
out over a period of 8 weeks.
An insulated box was designed and built to control the rate of temperature
decline in the samples during freezing (Fig. 1). The box could
hold six meat samples, with each sample filling a plastic specimen bottle
(no lid) 42 mm diameter and 55 mm high. A T-type thermocouple
probe was constructed [using 40 fine gauge (0.2mm wire diameter,
Class 1 Tolerance; calibrated against an RT200 reference thermometer)]
for each of the 6 samples using a 14 gaugeMonoject™hypodermic needle.
The thermocouple tip was insulated to prevent heat transfer from
the metal of the needle. The thermocouple sensors were fixed into the
lid such that it would always be located in the physical centre of the
product sample when the rig was assembled.
The thermocouples were calibrated using high purity (Milli-Q)
water placed into the sample pots instead of meat. The thermocouple
probes were centralised in the sample pots containing the Milli-Q
water. Once the box was closed and sealed with tape, the thermocouple
lead was plugged in and the data logger was started. The sample