Assessing the Impact of Carcass Hot Fat Trimming on Chilling Rate and Carcass Quality

Date
2023-08
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Abstract

Beef chilling practices continue to be challenged by today’s incremental increase in carcass weight and backfat thickness. Hot fat trimming (HFT) allows for optimization of the current scenario. Reducing bulk, specifically thick layers of insulating fat, prior to chilling through the use of hot fat trimming could improve the ability to chill carcasses and improve quality. The objective of the first study was to evaluate the impact of hot fat trimming on chilling rate, tenderness, marbling score, lean color, carcass composition, and carcass yield. Alternating left and right sides (N = 40; n = 20 sides per treatment) of the same carcass were hot fat trimmed (HFT) and the alternate side remained untrimmed (negative control; CON). Temperature was continuously monitored in the deep tissue round, loin, chuck, and surface of all sides during chilling. During grading, lean color and quality and yield grade measurements were obtained. Carcasses were fabricated and whole muscle components (blade meat, neck meat, and inside round cap) were collected from each side and subjected to proximate composition analysis. Two strip loin steaks (2.54 cm) as well as a face steak (approximately 100 g) from each side were collected and assigned to 1 of 2 aging treatments (2 d and 14 d) and analyzed for slice shear force (SSF) and sarcomere length (raw and cooked). The impact of HFT was measured on a within carcass basis (nested design) was a significance level set at α = 0.05 for all statistical analysis. All HFT monitored locations of the round, loin, chuck, and surface exhibited a more rapid temperature decline than CON sides (P < 0.01). The most pronounced effects occurred in the round, chuck, and surface, where the HFT was 2:52, 2:38, and 1:34 min faster than the CON to reach 4°C. The HFT loin demonstrated a 38 min advantage to 4°C over paired CON. Final mean temperatures (21 h) of the round, loin, and chuck were greater in CON sides (P  0.02). Final surface temperatures were trending (P = 0.07) for HFT sides to possess a lower mean temperature at the conclusion of chilling. Visual (P = 0.77) and instrumental (P  0.10) lean color measurements were not different. No differences existed in SSF and sarcomere length (P  0.15). As expected, external fat removal resulted in lower percentage of fat (P < 0.01) for blade meat and inside round cap and a greater percentage of moisture (P < 0.01) in these tissues. Hot fat trimming resulted in a greater subprimal yield (P < 0.01), bone yield (P < 0.01), lean trim yield (P  0.03), and lesser fat trim yield (P < 0.01) than paired CON sides. Hot fat trimming demonstrated a more rapid chilling rate, a substantial reduction in chilling duration, improved carcass composition, and increased yields without negatively impacting the quality of the carcass. The objective of the second study was to determine the effect of two levels of HFT on chilling rate, tenderness, marbling score, lean color, and the demand for energy during the chilling process. Alternating left and right sides (N = 420; n = 105 sides per treatment  2 replications) of the same carcass were assigned to one of two HFT techniques, minorly trimmed (MT; rep 1) or aggressively trimmed (AT; rep 2). The paired side was left untouched as a negative control (CON). The following measurements were obtained during collection: carcass weights, carcass temperature decline, instrumental color, quality and yield grade factors, as well as an 8 cm section from the anterior end of the strip loin. Temperature probes continuously monitored temperature in the deep tissue round, loin, chuck, and surface. Loin sections were aged to 14 d and fabricated into 2.54 cm steak for slice shear force (SSF) and Warner-Bratzler shear force (WBSF) determination with the remaining portion (face steak; approximately 100 g) reserved for sarcomere length analysis. This study was a nested design where carcass side served as the experimental unit nested in carcass, with a significance level set at α = 0.05 for all statistical analysis. Both MT and AT sides chilled more rapidly than CON counterparts at all measured locations (P < 0.05). Exponential decay models showed among the greatest difference (P < 0.05) realized in the chuck and surface. These areas reached 4°C in 1:29 and 1:22 faster in MT sides and 45 and 30 min faster in AT sides, respectively. Round temperatures of MT and AT reached 4°C more rapidly (14 min and 55 min, respectively) than paired CON counterparts. In the loin, MT and CON temperature declines were not different (P = 0.10); however, AT sides demonstrated a 14 min advantage (P < 0.01). These temperature advantages translated to 0.0113 and 0.0117 savings in tons of refrigeration (TR) over CON in MT and AT sides, respectively. Tenderness was not affected by HFT, as shown by no difference in SSF and WBSF values and sarcomere lengths for CON and either MT (P ≥ 0.31) or AT (P ≥ 0.58) sides. No differences found in marbling score between CON and MT or AT (P ≥ 0.16), or instrumental lean color of CON and AT (P = 0.16). In the current study, HFT uniquely had an advantage in temperature decline without affecting tenderness. Additionally, HFT results in lower energy usage and could lead to reduced refrigeration costs over untrimmed sides.


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Keywords
energy expenditure, hot fat trimming, chilling, beef quality, tenderness
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