A total of 30 beef short loins (M. longissmus lumborum; bone-in)
from 15 beef carcasses (steers; around 2 years old) at 2 days postmortem
was obtained from a local meat processing plant. Each short
loin was divided in half using a band saw yielding a total of 60 loin sections,
to which 6 different dry/wet-aging regimes (Table 1) were randomly
assigned based on the pre-allocated balanced incomplete block
design (n = 10/per treatment). The six treatments included 4 dryaging
regimes (2 aging temperatures (1 or 3 °C) × 2 air-velocities
(0.2 m/s or 0.5 m/s), and 2 wet-aging control groups (1 or 3 °C). The
wet-aged control groups were only tested for the temperature effect,
since beef loins in vacuum bags would not be affected by air-velocity,
when placed in a dry-aging testing chamber (DTC; Fig. 1). A total of 4
DTCs was used to set the four different dry-aging regimes. Each DTC
was monitored for the processing regimes including temperature, relative
humidity (RH) and air-velocity during the whole aging process period.
The given 2 × 2 (temperature × air-velocities) combinations
resulted in various RH regimes, such as 76% (at 1 °C and 0.2 m/s), 73%
(at 1 °C and 0.5 m/s), 49% (at 3 °C and 0.2 m/s), and 55% (at 3 °C and
0.5 m/s) as summarised in Table 1. Once initial pH and weight were
measured, each loin section was placed in each assigned DTC and aged
for 3 weeks. Each loin section was relocated within the individual testing
chambers on a weekly basis to avoid any location effect on meat
quality attributes. After 3 weeks of aging, the final pH and after storage
weight were measured. The beef loin sections were removed from the
assigned aging test chamber, and a certified butcher performed further
processing (trimming and boning-out) simulating actual retail butchery
practice (Fig. 1). Surface trimming loss and time taken for trimming
were recorded. From each loin section, steak samples were cut for
meat quality analyses including shear force, drip loss, initial colour,
and sensory evaluation. Samples formetabolomics analysiswere selected
based on the sensory evaluation data. The steaks for shear forcewere
cooked on the same day for themeasurement. The steaks for consumer
sensory evaluation (two steaks per treatment) were vacuum packaged
and stored at −20 °C for less than a month.