Pigs were harvested at a USDA inspected facility. Loins (Longissimus
thoracis et lumborum) from the left side of the pig were collected 1 day
postmortem, placed in bags along with their respective identification
tag, and transported with ice packs to the Iowa State University Department
of Food Science and Human Nutrition Sensory Evaluation Unit
(Ames, IA).
After aging for 10 days at 4 °C, loins were cut. The loin was cut
15.24 cm from the sirloin end to make a roast. The roast was then
vacuum packaged and frozen. Next, two 2.54 cm chops were cut, vacuum
packaged, and frozen. The chop cut closest to the roast was used for
pork quality measurements and the next following chop was used for
sensory analysis. These samples were frozen at −20 °C for a minimum
of 14 days to a maximum of 30 days before analysis. The second half of
the loin, starting with the side opposite of the blade end, was cut
into two 2.54 cm chops followed by a 15.24 cm roast. These samples
were weighed and used for fresh analysis. The first chop was used
for sensory analysis and the second chop, located closest to the
roast, was used for pork quality measurements. Every sample was
trimmed to approximately 6 mm of subcutaneous fat. After cooking,
each roast was faced and cut into four 2.54 cm slices. Slices closest to
the sirloin end and blade end of the loin were used for pork quality
measurements. The remaining 2 slices were used for the sensory
analysis.
2.3. Physical and chemical evaluation
Loin purge percent was completed before the loin was cut and was
calculated by dividing the purge weight by the sum of the loin and
purge weight. Frozen chops and roasts were thawed at 4 °C for 48 h.
Purge loss was calculated by dividing the purge weight by the sum of
the roast or chops and purge weight. Cooking loss was determined by
weighing the chop or roast before and immediately after cooking to
an internal temperature of 68 °C. Cooking loss was calculated as the
weight of the cooked sample subtracted from the raw sample weight,
then divided by the weight of the raw sample.
Star probe force was measured on a room temperature cooked
sample by an Instron (model 5566, Norwood, MA) with a 1 kilonewton
load cell and a 200 mm per minute crosshead speed. Six readings of each
sample were taken and the average value was used. The pH was