In-bag dry-aged lean beef was produced using a stepwise ageing process. Lean bull beef striploins were dry-aged at 2°C, 75% RH under three different air velocities: 0.5, 1.5, and 2.5 m·s−1 for 7 days followed by wet-ageing for 14 days. The quality and acceptability of the dry-aged beef were compared with equivalent beef dry-aged for 21 days at 0.5 m·s−1 which served as a control. Two portions of the dry-aged beef (7/21 days) were randomly selected and held frozen at −18°C for 12 months. Shear force, drip, and cook loss decreased significantly (
Postmortem ageing of fresh beef for retail and foodservice is essential in meeting the high demands and expectations of discerning consumers seeking exceptional eating experience. Ageing improves tenderness [
Dry-ageing requires critical control of processing parameters including temperature, air velocity, and relative humidity, to prevent excessive weight loss and growth of microorganisms. A new method called “in-bag dry-ageing” has emerged over the last decade to address the concerns associated with the traditional dry-ageing process [
Most dry-aged beef is produced from well-marbled premium beef cuts from prime steers or heifers with high intramuscular fat (IMF) and consumed locally rather than exported and fresh rather than thawed. Lean bull beef, on the contrary, is characterised as low-value beef with fat content of 1-2%, reduced juiciness, and tough texture. As a result, it is usually processed to sausages, patties, and other further processed meat products and hardly used for premium products such as the dry-aged products. Recently, dry-aged
Long-term storage of dry-aged beef may need to be considered if the meat industry was to produce dry-aged meat for commercial export as it currently does for chilled and frozen wet-aged meat. Freezing of meat at −18°C during storage and distribution is a common practice in the meat industry, particularly for the export market. A processing strategy called “aged and then frozen” was of great interest over the last decade. This strategy refers to applying a certain period of wet-ageing (2–4 wks) prior to the frozen storage. It has been proven to improve the colour stability, tenderness, and water-holding capacity without negative impact on the meat quality [
This study aimed to investigate the effects and interactions of air velocities, ageing time, and long-term frozen storage on the meat quality and acceptability of in-bag dry-aged striploins from lean bull beef using the stepwise ageing regime. The current study was carried out to test the hypothesis that the combination of in-bag dry-ageing at higher air velocities for shorter ageing time followed by wet-ageing in vacuum barrier bags would produce dry-aged meat of equivalent quality, long-term frozen stability, and acceptability to in-bag dry-ageing meat produced using longer dry-ageing time and with no wet-ageing involved.
A total of 15 pairs (
Schematic illustration of the ageing process and treatment combinations in the current study. BD: in-bag dry-ageing; W: wet-ageing; T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
A thin layer of dried and discoloured surface (including subcutaneous fat) was trimmed off from the striploins aged for 7 d and 21 d and then fabricated into 2 cm thick steaks. Minimum three steaks were taken from each loin of each treatment (T1–T4) and at different ageing time points (0, 7, and 21 d) for further analysis of fresh beef. No subsample was taken at 7 d of ageing time for the control (T1). Another three fresh steaks (minimum) were obtained from each loin of each treatment and ageing time point, as described above, vacuum packed immediately after ageing, and stored frozen at −18°C for 12 months to determine the effect of long-term frozen storage on the quality of dry-aged lean beef.
Microorganisms from the untrimmed surface of fresh (unfrozen) beef samples were enumerated before (0 d) and after the ageing process (21 d) for all four treatments using standard methods in the Compendium of Methods of Microbiological Examination of Foods [
The pH of fresh and frozen (thawed at 4°C overnight) in-bag dry-aged beef samples (T1–T4 at all ageing time points, one steak per loin) obtained from
Beef steaks from pH measurement were minced individually after trimmed off intramuscular fat and subsamples were collected for proximate analysis. Moisture content was measured using the oven-drying method described in AOAC 950.46 [
The steaks (one steak per loin) from fresh (0, 7, and 21 d) and frozen (7 and 21 d, thawed at 4°C overnight) in-bag dry-aged beef loins (T1–T4) were placed on a polypropylene foam tray lined with moisture absorbent pads and then overwrapped with the polyvinyl chloride (PVC) film and allowed to bloom for 30∼60 min under simulated retail display light at 4°C. Surface colour was measured using a Minolta Chroma Meter (CR-400; Konica Minolta Photo Imaging Inc., Mahwah, NJ, USA) that had been calibrated using a standard white tile. CIE (L
The water-holding capacity was evaluated in the form of % drip loss for the fresh beef (7 and 21 d of in-bag dry-aged), % thaw + drip loss for the frozen beef (7 and 21 d of in-bag dry-aged), and % cook loss for both the fresh and frozen samples (one steak per loin).
The bag drip method by Honikel [
Fresh beef portions (one portion per loin, 6 cm thickness) with weight of approximately 400 g from 7 d to 21 d of ageing were cooked in a boiling water bath (99°C) to the internal temperature of 70°C. Frozen steaks (one steak per loin, thaw at 4°C overnight) of 2 cm thickness from 7 d to 21 d of ageing time were cooked sous vide at 70°C for 1 hr. Immediately after cooking, the cooked samples were transferred into an ice bath for 30 min to prevent further cooking, blotted dry, and weighed. The % cook loss was calculated as follows: % cook loss = [(initial weight − cooked weight)/initial weight] × 100.
Cooked steaks from Section
The texture profile of long-term frozen in-bag dry-aged lean beef was analysed using texture profile analysis (TPA) according the procedure described by Zhang et al. [
Fresh in-bag dry-aged steaks (21 d, minimum three steaks per loin) were cooked in a conventional oven at 170°C until the core temperature reached 70°C. Frozen in-bag dry-aged steaks (21 d, minimum three steaks per loin) were thawed at 4°C chiller overnight and precooked sous vide at 70°C for 1 h and reheated on a grill set at 230°C for 90 s on each side. Once cooked, each steak was cut across the grain into a 1.3 × 1.3 × 2.0 cm piece and randomly assigned to a plastic cup. All the cups were prelabelled with unique codes made of panelist numbers (1, 2, 3, etc.) × sample ID (A, B, C, and D). Each panellist was asked to taste one sample each time in the order from A to D. Each sample ID (A–D) of the same panellist corresponded to one of the ageing treatments (T1–T4). The panellists may taste the same sample from the same steak more than once due to the randomised design model. Water and water crackers were provided as palate cleansers. Consumers were asked to take a bite of cracker, rinsed their mouths, and rest for 30 s between the samples. Consumers have been informed that swallowing was allowed but not compulsory.
A randomised trial was designed with 30 striploins from 15 beef carcasses (
Weight loss of lean beef during in-bag dry-ageing increased (
Average % weight loss of lean beef striploins of four different ageing treatments across different ageing times (days). BD: in-bag dry-ageing; W: wet-ageing. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
A significantly lower (
Effect of ageing treatments, ageing time, and frozen storage on the proximate content of in-bag dry-aged lean bull beef.
Attributes/storage type | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | |||||||||
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Fresh | 0 d | 76.22x | 76.29x | 75.84x | 75.81x | 0.43 | 0.029 | 0.532 | 0.450 | 0.561 | 0.727 | 0.810 |
7 d | 75.83ay | 74.77by | 75.84ay | |||||||||
21 d | 74.93y | 75.19z | 74.67z | 74.33z | ||||||||
|
0.001 |
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|
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Frozen | 0 d | 76.27 | 76.37 | 76.55 | 75.69 | 0.82 | 0.002 | 0.824 | 0.494 | |||
7 d | 76.22a | 74.83b | 75.69a | |||||||||
21 d | 74.93 | 75.09 | 74.57 | 74.08 | ||||||||
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0.241 | 0.145 | 0.068 | 0.075 | ||||||||
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Fresh | 0 d | 0.69 | 0.64 | 1.10 | 1.17 | 0.26 | 0.018 | 0.796 | 0.163 | 0.201 | 0.370 | 0.832 |
7 d | 0.63a | 1.21b | 0.62a | |||||||||
21 d | 0.66 | 0.69 | 1.05 | 1.25 | ||||||||
|
0.799 | 0.654 | 0.298 | 0.146 | ||||||||
Frozen | 0 d | 1.09 | 0.99 | 0.88 | 2.00 | 0.33 | 0.056 | 0.394 | 0.222 | |||
7 d | 0.73a | 1.28b | 0.85a | |||||||||
21 d | 0.68 | 0.78 | 1.13 | 1.08 | ||||||||
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0.232 | 0.541 | 0.600 | 0.116 | ||||||||
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Fresh | 0 d | 22.31x | 22.17x | 22.26x | 22.26x | 0.29 | 0.948 | 0.709 | 0.236 |
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7 d | 22.65y | 23.21y | 22.77y | |||||||||
21 d | 23.48y | 23.33z | 23.70z | 23.77z | ||||||||
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0.003 | <0.001 |
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Frozen | 0 d | 19.01x | 18.25x | 18.65 | 20.34 | 1.04 | 0.198 | 0.874 | 0.432 | |||
7 d | 19.78xy | 21.37 | 20.12 | |||||||||
21 d | 21.35y | 21.23y | 21.11 | 22.11 | ||||||||
|
0.043 | 0.044 | 0.125 | 0.058 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
Meat colour is widely used by consumers to determine the freshness of the meat products [
Effect of ageing treatments, ageing time, and frozen storage on pH of in-bag dry-aged lean bull beef.
Attributes/storage type | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | ||||||||
pH | |||||||||||
Fresh | 0 d | 5.34x | 5.34x | 5.36x | 5.32x | 0.04 | 0.082 | 0.232 | 0.035 | 0.226 | 0.654 |
7 d | 5.74y | 5.60y | 5.69y | ||||||||
21 d | 5.66ay | 5.62abz | 5.64ay | 5.58bz | |||||||
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Frozen | 7 d | 5.66 | 5.65 | 5.62 | 0.03 | 0.420 | 0.644 | 0.525 | |||
21 d | 5.63 | 5.62 | 5.61 | 5.6 | |||||||
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0.068 | 0.299 | 0.588 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
Effect of ageing treatments, ageing time, and frozen storage on the instrumental colour of in-bag dry-aged lean bull beef.
Attributes/storage type | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | ||||||||
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Fresh | 0 d | 33.51x | 33.34x | 33.05x | 32.65x | 0.62 | 0.022 | 0.588 | 0.411 |
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7 d | 40.78ay | 41.28ay | 38.54by | ||||||||
21 d | 39.80y | 39.46z | 39.46z | 38.85y | |||||||
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<0.001 |
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Frozen | 7 d | 35.99 | 36.52 | 35.44 | 0.97 | 0.492 | 0.712 | 0.926 | |||
21 d | 36.22 | 35.86 | 36.08 | 36.48 | |||||||
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0.897 | 0.678 | 0.232 | ||||||||
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Fresh | 0 d | 18.05 | 18.21x | 17.44x | 17.47x | 0.90 | 0.797 | 0.927 | 0.084 | 0.004 |
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7 d | 15.25y | 15.29y | 14.62y | ||||||||
21 d | 18.45a | 18.55ax | 17.06abx | 16.38bz | |||||||
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0.232 | <0.001 | 0.004 | 0.001 | |||||||
Frozen | 7 d | 13.37 | 11.79 | 13.82 | 0.81 | 0.075 | 0.312 | 0.742 | |||
21 d | 13.77 | 13.02 | 13.34 | 13.04 | |||||||
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0.686 | 0.303 | 0.157 | ||||||||
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Fresh | 0 d | 11.84x | 11.74x | 11.44 | 11.31x | 0.49 | 0.059 | 0.53 | 0.018 |
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7 d | 10.81y | 11.39 | 10.23y | ||||||||
21 d | 12.93ay | 12.69az | 11.98ab | 11.44bx | |||||||
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0.005 | 0.001 | 0.298 | 0.058 | |||||||
Frozen | 7 d | 6.56 | 5.53 | 6.87 | 0.58 | 0.116 | 0.53 | 0.471 | |||
21 d | 7.43 | 6.93 | 7.17 | 6.55 | |||||||
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0.547 | 0.154 | 0.355 | ||||||||
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Fresh | 0 d | 21.59x | 21.68x | 20.87x | 20.82x | 0.99 | 0.585 | 0.347 | 0.047 |
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7 d | 18.70y | 19.08y | 17.84y | ||||||||
21 d | 22.54ay | 22.48ax | 20.86abx | 19.98bx | |||||||
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0.034 | <0.001 | 0.048 | 0.005 | |||||||
Frozen | 7 d | 14.9 | 13.03 | 15.44 | 0.94 | 0.078 | 0.994 | 0.653 | |||
21 d | 15.66 | 14.00 | 15.15 | 14.6 | |||||||
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0.888 | 0.236 | 0.169 | ||||||||
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Fresh | 0 d | 33.36x | 32.85x | 33.34x | 32.93x | 0.75 | 0.267 | 0.885 | 0.775 |
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7 d | 35.42y | 36.79y | 35.01y | ||||||||
21 d | 35.25y | 34.42z | 35.14y | 34.95y | |||||||
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0.01 | <0.001 | 0.001 |
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Frozen | 7 d | 26.04 | 24.89 | 26.38 | 1.22 | 0.401 | 0.442 | 0.544 | |||
21 d | 28.34 | 27.92 | 28.2 | 26.67 | |||||||
|
0.061 | 0.158 | 0.755 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
Water-holding capacity (Table
Effect of ageing treatments, ageing time, and frozen storage on water-holding capacity of in-bag dry-aged lean bull beef.
Attributes/storage type | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | ||||||
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Fresh | 7 d | 3.86x | 3.35x | 3.26x | 0.29 | 0.226 | 0.152 | 0.257 | |
21 d | 1.35 | 1.56y | 1.58y | 1.92y | |||||
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<0.001 | 0.001 | 0.001 | ||||||
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Frozen | 7 d | 12.38x | 10.36x | 11.75x | 1.41 | 0.335 | 0.322 | 0.443 | |
21 d | 5.79 | 7.49y | 5.86y | 7.33y | |||||
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0.009 | 0.013 | 0.003 | ||||||
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Fresh | 7 d | 30.22 | 29.46 | 32.18x | 1.69 | 0.519 | 0.979 | 0.204 | |
21 d | 27.77 | 27.74 | 25.98 | 28.69y | |||||
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0.240 | 0.120 | 0.020 | ||||||
Frozen | 7 d | 31.81 | 31.81 | 33.04x | 1.04 | 0.174 | 0.498 | 0.644 | |
21 d | 29.60 | 30.29 | 30.59 | 29.40y | |||||
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0.103 | 0.371 | 0.003 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d. Different letters of “x, y, or z” within the same column mean results are significantly different from each other (
Effect of ageing treatments, ageing time, and frozen storage on instrumental texture of in-bag dry-aged lean bull beef.
Attributes/storage type | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | ||||||
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Fresh | 0 d | 132.00x | 116.70x | 131.81x | 114.25x | 12.45 | 0.071 | 0.932 | 0.919 |
7 d | 89.34xy | 69.24y | 83.95y | ||||||
21 d | 72.67y | 71.98y | 68.26y | 70.61y | |||||
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0.001 | 0.011 |
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0.007 | |||||
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Frozen | |||||||||
Hardness (kg) | 7 d | 2.49 | 2.81 | 2.72 | 0.37 | 0.348 | 0.601 | 0.920 | |
21 d | 3.02 | 2.88 | 3.11 | 3.10 | |||||
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0.404 | 0.362 | 0.193 | ||||||
Springiness | 7 d | 0.53 | 0.51 | 0.54 | 0.02 | 0.678 | 0.634 | 0.969 | |
21 d | 0.53 | 0.53 | 0.53 | 0.52 | |||||
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0.778 | 0.051 | 0.582 | ||||||
Cohesiveness | 7 d | 0.55 | 0.53 | 0.55 | 0.41 | 0.313 | 0.609 | 0.410 | |
21 d | 0.55 | 0.54 | 0.54 | 0.54 | |||||
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0.380 | 0.388 | 0.537 | ||||||
Chewiness (kg) | 7 d | 0.72 | 0.75 | 0.81 | 0.12 | 0.394 | 0.547 | 0.944 | |
21 d | 0.89 | 0.83 | 0.89 | 0.89 | |||||
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0.440 | 0.159 | 0.509 | ||||||
Resilience | 7 d | 0.23 | 0.22 | 0.22 | 0.01 | 0.522 | 0.909 | 0.276 | |
21 d | 0.23 | 0.22 | 0.22 | 0.22 | |||||
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0.181 | 0.473 | 0.773 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
There was no interaction (
Stepwise ageing involving the in-bag dry-ageing of lean bull beef for 7 d followed by 14 d of wet-ageing (T2) significantly (
The instrumental tenderness (shear force) of dry-aged lean beef produced using stepwise ageing did not differ with its control counterpart produced by dry-ageing of lean beef for 21 d straight (Table
There was no effect of stepwise ageing on the measured quality parameters of frozen in-bag dry-aged lean beef (21 d, T1 and T2). Therefore, the use of stepwise ageing produced in-bag dry-aged lean beef of equivalent quality to those of in-bag dry-ageing only without an adverse effect, even after a long-term frozen storage.
A significantly higher (
A significantly (
Effect of ageing treatments and ageing time on
Attributes | Ageing time | Treatments | SED |
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T1 | T2 | T3 | T4 | ||||
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0 d | 0.992x | 0.993x | 0.994x | 0.992x | 0.001 | 0.325 |
21 d | 0.987y | 0.987y | 0.988y | 0.986y | |||
|
0.005 |
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0.003 |
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APC | 0 d | 4.21x | 2.62 | 3.09 | 2.74x | 0.61 | 0.281 |
21 d | 2.50y | 3.29 | 2.56 | 2.00y | |||
|
0.038 | 0.459 | 0.494 |
|
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LAB | 0 d | 1.15 | ND | 1.50 | ND | 0.07 | — |
21 d | ND | ND | ND | ND | |||
|
— | — | — | — | |||
Mould | 0 d | 1.39 | ND | ND | ND | 0.05 | — |
21 d | ND | 1.00 | ND | ND | |||
|
— | — | — | — | |||
Yeast | 0 d | 2.21x | ND | 1.48 | 1.39 | 0.40 | 0.003 |
21 d | 4.06ay | 1.57b | 2.12b | 2.41b | |||
|
0.007 | — | 0.237 | 0.076 | |||
Enterobacteriaceae | 0 d | 3.16 | 1.84 | 1.38 | 1.71 | 0.71 | — |
21 d | ND | 2.69 | ND | 1.35 | |||
|
— | — | — | — | |||
|
0 d/21 d | ND | ND | ND | ND | — | — |
ND: not detected; BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
The quality parameters of a long-term frozen-stored in-bag dry-aged lean beef (21 d, T1–T4) were not affected by the treatment combinations of air velocity and stepwise ageing. The differences in colour (a
Effect of ageing treatment combinations and frozen storage on sensory acceptability of in-bag dry-aged lean beef for 21 days.
Attributes | Storage type | Treatments | SED |
| |||
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T1 | T2 | T3 | T4 | ||||
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Aroma | 56.53 | 55.58 | 55.78 | 56.60 | 2.81 | 0.977 | |
Tenderness | 53.62 | 48.73 | 45.84 | 55.01 | 4.88 | 0.224 | |
Juiciness | 54.39 | 53.64 | 48.35 | 47.80 | 4.12 | 0.244 | |
Flavour | 44.85 | 44.76 | 41.87 | 42.95 | 4.35 | 0.881 | |
Off-flavour | 20.68 | 16.73 | 19.16 | 17.79 | 3.66 | 0.727 | |
Overall liking | 59.77 | 58.20 | 52.88 | 57.17 | 3.33 | 0.218 | |
Preference ranking (%) | 28.41 | 22.73 | 22.73 | 20.45 | |||
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Aroma | 5.75 | 5.81 | 5.81 | 6.00 | 0.19 | 0.548 | |
Tenderness | 5.74 | 5.46 | 5.75 | 6.02 | 0.30 | 0.397 | |
Juiciness | 5.86a | 4.55b | 5.24c | 5.91a | 0.26 |
| |
Flavour | 6.12 | 5.76 | 5.96 | 6.33 | 0.23 | 0.126 | |
Off-flavour | 1.71 | 1.89 | 1.85 | 1.78 | 0.12 | 0.401 | |
Overall liking | 6.03a | 5.37b | 5.89a | 6.25a | 0.24 | 0.006 |
BD: in-bag dry-ageing; W: wet-ageing; SA: stepwise ageing; AV: air velocity. T1: BD at 0.5 m·s−1 for 21 d; T2: BD at 0.5 m·s−1 7 d + W for 14 d; T3: BD at 1.5 m·s−1 for 7 d + W for 14 d; T4: BD at 2.5 m·s−1 for 7 d + W for 14 d.
Debate on the consumer preference and acceptability of dry-aged beef over the equivalent wet-aged beef is ongoing. Some of the studies found no significant difference in the consumer acceptability of the tenderness and juiciness of dry-aged as compared to the wet-aged beef [
For the overall liking and the flavour liking, findings from previous studies were also controversial. Thus, the conclusion over the most effective ageing method to maximise palatability cannot be easily drawn. In the current study, consumers gave similar ratings of overall liking to all four samples; however, different findings were observed when they were asked to express their preference between samples. As shown in Table
Rancidity, noted as the off-flavour, is another important indicator for the consumers to determine the freshness of cooked meat. Low mean values of the off-flavour were found in the cooked steaks of all the treatments, suggesting the difficulty in recognising the rancid flavour from the frozen in-bag dry-aged (21 d) lean beef samples. The rancidity note generated from the deteriorated meat is mainly caused by the oxidation and hydrolysis of the fat in meat. The meat samples containing higher fat (such as prime cuts and wagyu meat) were more susceptible to oxidation and consequently give off the rancid flavour. It is worth noting that the beef samples used in this study were lean bull beef, which only contained approximately 1% of IMF (Table
The length of dry-ageing time had a significant (
Overall, the pH of in-bag dry-aged striploins increased significantly (
After in-bag dry-ageing for 21 d (T1, Table
Drip loss significantly decreased (
Shear force values decreased significantly (
There was no difference in lactic acid bacteria, Enterobacteriaceae, and moulds across ageing time in the current study.
After long-term frozen storage, the proximate content of in-bag dry-aged beef from all four ageing treatments did not differ across the ageing time except for the muscle protein content which increased with ageing (Table
The pH, colour, and texture profile of in-bag dry-aged lean beef was not affected by ageing time (
The pH of in-bag dry-aged beef was not affected by long-term frozen storage (
Frozen storage had the major effect on the instrumental colour of in-bag dry-aged beef (Table
The water-holding capacity of frozen in-bag dry-aged beef decreased due to the extrafluid loss upon thawing (Table
The increase of dry-ageing chamber air velocity accelerated the weight loss of in-bag dry-aged lean bull beef but had no other negative effects on meat quality, microbiological safety, and consumer palatability. Ageing time, on the contrary, played a more important role in improving the quality of the dry-aged products. Combining in-bag dry-ageing with traditional wet-ageing as a stepwise ageing strategy was able to produce dry-aged lean beef of equivalent quality compared to those of dry-ageing only for the same period of ageing time but with lower weight loss/higher yield. In-bag dry-aged lean bull beef products could be long-term frozen stored for up to 12 months and still be acceptable to consumers.
The following are some of the implications particularly the stepwise ageing process used in the present study: The process can be applied by the meat industry to shorten the turnover time of the dry-ageing chamber because the wet-ageing component can be accomplished during chill chain distribution without any loss in quality. The process produced microbiologically safe dry-aged products with improved ease of handling and potentially free of trimming and increased yield. This enables the meat industry to produce dry-aged products easier, safer, and cheaper for both local and export markets. Long-term frozen storage of in-bag dry-aged lean beef produced using the process had no effect on the quality of the thawed product except for the minor discolouration. Thus, postthawing display may not be recommended for long-term frozen in-bag dry-aged lean beef. Exporting the product frozen in vacuum packages or supplying the product precooked in sous vide for local and international restaurants and markets is suggested to retain the value of the in-bag dry-aged products. In-bag dry-aged lean beef from the process have potential as a value-added product for the low marbled fresh and frozen beef market locally and globally. Future work regarding the oxidative changes of lipids and proteins, the changes of flavour precursors from the ageing treatments and frozen storage, and their impact on the shelf life and functionality of the products need to be explored.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare that there are no conflicts of interest regarding the publication of this article.
The authors would like to acknowledge Debbie Frost, Kevin Taukiri, and Dr. Talia Hicks for assistance with the collection of samples, Robert Kemp for assistance with the setup of the dry-ageing chambers, and Dr. Maryann Staincliffe for statistical advice. The first author would like to acknowledge the Auckland University of Technology for his PhD scholarship from the Performance Based Research Fund. This work was supported by the Ministry of Science and Innovation, New Zealand, and the Internal Strategic Science Investment Fund of AgResearch Limited (contract A19113).