For the purpose of this experiment, twenty striploins (M. longissimus
lumborum) were selected from the regular supply of a commercial abattoir
and portioned and packaged on site. Of these, ten were obtained
from 1 day postmortem YG MSA carcasses (females or steers up to
30 months old that have passed MSA grading). The other ten striploins
(7 day vacuum aged) originated from PR carcasses (animals up to
42 months old with no more than 7 permanent incisor teeth).
Four adjacent steaks (about 2.5 cmthick)were cut, using a knife, from
the anterior end of the primal ofwhich 2 were randomly assigned toMAP
packaging (80% O2, 20% CO2; oxygen transmission rate 1 cm3/m2/24 h)
and the remaining 2 to Darfresh® (skinpack) packaging (oxygen transmission
rate b2 cm3/m2/24 h). Sampleswere transported to UNE in polystyrene
boxes on a layer of ice and stored for an additional 7 days at about
3 °C before further sampling.
After the 7 day ageing period, the packages were opened and the
steaks were sampled for pH and color measurements, sensory analysis,
shear force and degradation of myofibrillar proteins. Regarding the
latter, a sample of about 4 g was cut from each steak, placed in 5 mL
tubes and frozen at −20 °C in a walk-in −20 °C freezer until analysis.