2. Materials and methods
2.1. Meat quality attribute analyses
2.1.1. Raw materials and processing
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 for metabolomics analysis were selected based on the sensory evaluation data. The steaks for shear force were cooked on the same day for the measurement. The steaks for consumer sensory evaluation (two steaks per treatment) were vacuum packaged and stored at −20 °C for less than a month.
2. วัสดุและวิธีการ 2.1. เนื้อคุณภาพคุณลักษณะวิเคราะห์ 2.1.1 ดิบและประมวลผล 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 for metabolomics analysis were selected based on the sensory evaluation data. The steaks for shear force were cooked on the same day for the measurement. The steaks for consumer sensory evaluation (two steaks per treatment) were vacuum packaged and stored at −20 °C for less than a month.
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