Meat Science 175 (2021) 108466
Contents lists available at ScienceDirect 
Meat Science 
journal homepage: www.elsevier.com/locate/meatsci 
Effect of slaughter age and post-mortem days on meat quality of longissimus 
and semimembranosus muscles of Boer goats 
Archana Abhijith a, Robyn D. Warner a, Minh Ha a, Frank R. Dunshea a,b, Brian J. Leury a, 
Minghao Zhang a, Aleena Joy a, Richard Osei-Amponsah c, Surinder S. Chauhan a,* 
a School of Agriculture and Food, The University of Melbourne, Parkville, VIC 3010, Australia 
b Faculty of Biological Sciences, The University of Leeds, Leeds LS2 9JT, United Kingdom 
c Department of Animal Science, School of Agriculture, University of Ghana, Legon, Accra, Ghana   
A R T I C L E  I N F O   A B S T R A C T   
Keywords: This study investigated the effects of age of animal and days post-mortem (PM) on meat quality of Boer goats. 
pH decline Twenty-four (24) wether Boer goats of two age groups (2YO group: 2 years old and 9MO: 6–9 months, with 12 
Retail meat quality animals/group) were slaughtered in a commercial processing plant. The pH@Temp18 was estimated to be above 
Lipid oxidation 6 in both age groups with higher (P < 0.01) values in 2YO goats. The PM storage for 14 days reduced the shear 
TBARS 
Total glycogen force in both age groups (P < 0.01). 2YO goat muscles (longissimus and semimembranosus) exhibited higher (P <
0.01) Thiobarbituric acid reactive substance values (TBARS), indicating increased lipid oxidation. Glycogen (P <
0.01) and lactate content (20 min post-slaughter) in longissimus of 9MO were lower compared to 2YO, and total 
muscle glycogen concentration was lower (P < 0.01) in both age groups below the threshold levels. Hence, as 
hypothesized, age and days PM proved to play crucial roles on Boer meat quality.   
1. Introduction carcasses, 18–35 ◦C at pH = 6 was defined as the optimum pH tem-
perature window for product to be aged for 5 days and 8–18 ◦C for 
Australia is the largest exporter of goat meat globally (MLA, 2020). product aged for 10 days (Gutzke, Franks, Hopkins, & Warner, 2014). To 
The Australian goat meat industry recorded 1.6 million head slaugh- the best of our knowledge, there is no such pH temperature window 
tered in 2018, that was worth over AUD $182 M (MLA, 2020). The defined for goat meat. Also, little is known about goat meat quality at-
majority of Australian goat meat produced is exported. Goat meat has no tributes as affected by age of animals and post-mortem storage, which 
religious restrictions, and is one of the most widely consumed red meats may be vital to develop and optimize goat meat production and pro-
in parts of Asia, the Middle East, Africa and Hispanic population across cessing systems. Therefore, this study was designed to document the 
the United States of America (GICA, 2015). Although, the export market postmortem muscle pH temperature decline, cooked meat quality and 
is a lucrative enterprise, domestic consumption is negligible, apart from retail color stability of Boer goats as affected by animal age and days 
the ethnic populations remaining true to their cultural origins (MLA, post-mortem (PM). We hypotheized that age of animal and days PM 
2020). However, the Australian goat meat industry is on track to sta- have key roles to play on the meat quality of goats. 
bilize the supply base and achieve new market opportunities and expand 
the domestic market. However, research and development activities in 2. Materials and methods 
Australia to reduce the inconsistent goat meat eating quality is in its 
early stages (MLA, 2017). Quality assurance is an innovative approach 2.1. Animals 
that has proven to be successful in promoting the beef and sheep meat 
industry (Bonny et al., 2018). When the Meat Standards Australia (MSA) Twenty-four (twelve 6–9 months old goats: 9MO and twelve 2-year 
beef grading system was established, inclusion of an ideal pH/temper- old: 2YO) wether Boer goats were sourced from Myrrhee farm, Victo-
ature window was a critical concept put forward initially (Hopkins, ria, Australia. The goats had been on improved pasture (rye grass) and 
Ponnampalam, Van de Ven, & Warner, 2014). For example for lamb native grasses, along with grass hay. Lucerne hay was only available 6 
* Corresponding author. 
E-mail address: ss.chauhan@unimelb.edu.au (S.S. Chauhan).  
https://doi.org/10.1016/j.meatsci.2021.108466 
Received 16 September 2020; Received in revised form 28 January 2021; Accepted 3 February 2021   
Available online 11 February 2021
0309-1740/© 2021 Elsevier Ltd. All rights reserved.
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
weeks before they were used in the study. The animals were transported a gas mixer to achieve O2: CO2 ratio of 80%: 20%. The gas ratio of the 
(3 h) to Cedar Meats, Brooklyn, Australia and kept in lairage overnight packs were checked by a gas analyzer and was 80% O2, 20% CO2 ±
for 14 h before slaughter. Goats were transported using purpose-built 0.1%. Chops (5 cm thickness, 90 g) were placed on a cello pad positioned 
animal transport trailer and every care was taken to minimize stress to in Cryovac black trays (170 mm × 223 mm, Sealed Air, Australia). The 
animals as per standard practices. Goats were off feed during lairage trays were sealed with a biaxially Oriented PolyAmide/Polyethylene / 
before slaughter and had access to water only. Ethylene vinyl alcohol-based film (LID-1050, OTR 10 cm3/m2/24). 
Trays were subsequently kept in 4–6 ◦C refrigerator (display cabinets) 
2.2. Slaughter procedures, measurement and sampling for 10 days and color was measured on the respective days of display. 
Retail packs were randomly distributed on the shelves of cold display 
The animals were electrically stunned (220 V) prior to slaughter, and cabinet with high-impact LED internal lighting on each side (maximum 
then exsanguinated using Halal methods with no electrical stimulation 18 W) with an average light intensity of 732 lx, color temperature of 
of the carcasses, which was the normal practice in this plant. Halal 4000 K, and color rendering index of 85 (GM1000LWCAS, Bromic Pty 
slaughter refers to the bleeding of animals intended for meat production Limited). Meat color was measured using Hunterlab Miniscan EZ (model 
following the Islamic criteria of Islamic ritual slaughter (Abdullah, No. 45/0-L, aperture of 31.8 mm; Hunter Assoc. Labs Inc., Virginia, 
Borilova, & Steinhauserova, 2019). The hot carcass weights were USA) calibrated against white and black reference tiles. Duplicate sur-
recorded, and the Girth Rib (GR) score was measured (total tissue depth face color measurements were taken with D65 illuminant and 10◦
over the 12th rib, 110 mm from the midline) using a GR knife. The pH observer angle. The CIE L* (lightness), a* (redness) and b* (yellowness) 
was measured in the left side of the longissimus thoracis et. lumborum values were obtained from the average values of two readings on the 
(LTL) at the 12th/13th rib site, after calibrating the meter at chiller surface of muscle samples. Psychometric hue angle (h) and psychometric 
temperature, at 30 min, 1, 2, 3, 4, 5, 6, 8, and 24 h post-slaughter. chroma (C*) were calculated using the equations outlined by Hunt et al. 
Carcasses were chilled overnight at 4 ◦C. pH of LL at 48 h post- (1991): psychometric chroma C* = (a2 + b2) 0.5, psychometric hue h =
mortem was recorded in the Meat research facility on the following tan− 1 (b/a). Cooking loss was measured following the method of Ha, 
day. Muscle pH was measured using meters with temperature compen- Dunshea, and Warner (2017). Muscle samples were weighed and cooked 
sation (WP-80, TPS Pty Ltd., Brisbane, Australia) and a polypropylene in water bath using moist cooking method (F38-ME, Julabo, 77,960 
spear-type gel electrode (Ionode IJ 44), which was calibrated at ambient Seelbach/Germany), which was pre-heated to 70 ◦C and samples were 
temperature. The pH meter was calibrated before use and at regular left in the water bath until the core temperature reached 70 ◦C. The 
intervals using pH 4 and pH 7 buffers. Dressing percentage (DP) was temperature of the sample was measured using a thermometer equipped 
calculated on the basis of live weight and hot carcass weight (HCW) with T-type thermocouples (Grant Instruments, Australia). Samples 
using the formula HCW/LW*100. Samples for measuring glycogen and were then cooled in ice water to prevent further cooking, patted dry with 
lactate content (1 g each) were taken from the LTL between the fourth paper towel and weight was recorded. The samples were stored in plastic 
and fifth lumbar vertebrae, approximately 20 min post-slaughter, bags (to reduce moisture loss) at 4 ◦C in a chiller overnight prior to 
trimmed of all visible connective tissue and fat using a scalpel, snap Warner-Bratzler shear force (WBSF) and compression test. Hence, WBSF 
frozen in liquid nitrogen and then stored in - 80 ◦C. and compression test was done with cooked meat and color and TBARS 
was done on raw meat. 
2.3. Meat packaging and storage 
2.4. Warner-Bratzler shear force and compression 
The LTL and semimembranosus (SM) muscles were sampled 24 h after 
slaughter. Vacuum packaging was performed on a Multivac C200 (Sepp Samples prepared into 90 g blocks and packed in each tray were used 
Haggenmüller GmbH & Co., Wolfertschwenden, Germany) using poly- for both WBSF and compression test (parameters measured were hard-
amide and polyethylene vacuum pouches PA/PE 70 (Multivac) with an ness, chewiness, and cohesiveness), which were conducted the next day 
oxygen permeability less than 65 cc/m2 (24 h) and water transmission after cooking, following an established method outlined by Honikel 
less than 5 g/m2/24 h. Each age group comprised of 12 left and 12 right (1998) with some modifications. Briefly, six rectangular strips of 1 cm2 
LTL and SM. The 12 left and 12 right LTL and SM of each age group were were cut parallel to the direction of muscle fibers from each sample. 
then randomly assigned to 1 or 14 days PM storage (all within a carcass). WBSF was measured by using a shear blade (V-shaped) attached to a 
After this allocation, each side was then divided into three blocks (90 g, texture analyzer (LS5 Ametek Lloyd Instruments Ltd., Largo, FL, USA) 
45 g, 90 g), which were assigned to three days of display (0, 5 and 10 with a 500 N load cell, and the shearing speed was set at 300 mm/min. 
days). Two of these blocks were 90 g each and one block weighed around The average of 6 sub-samples was calculated as an estimate of tough-
45 g. This was due to the limitation in muscle samples especially from ness. Compression test was conducted according to a method previously 
the 9MO. Texture analysis was done only on 0 and 10 day (90 g each) reported by Ha et al. (2017). A 0.63 cm diameter flat-ended probe was 
samples due to the limited muscle samples. Each of the two 90 g blocks adapted to a texture analyzer (LS5 Ametek Lloyd Instruments Ltd., 
were used for texture analysis, color and Thiobarbituric acid reactive Largo, FL, USA). A total of 5 measurements were taken for each sample 
substances (TBARS), whereas the third block from the muscle was used and presented as means. 
for color measurement and TBARS. Hence, from one carcass, there were 
four 90 g blocks and two 45 g blocks. 2.5. TBARS assay 
The samples assigned to 0 day of display were first tested for color 
and samples for TBARS were taken from the same block. The remaining Samples for TBARS analysis (10 g) were collected at 0, 5 and 10 days 
sample was then cooked for cooking loss measurement, which was then of display and frozen. The lipid oxidation in the samples was assessed by 
kept in chiller for overnight and used for texture analysis. Similarly, the the TBARS procedure (Sørensen & Jørgensen, 1996) and expressed as 
blocks assigned to 5 day and 10 days of display were taken out from mg of malondialdehyde (MDA) per kg of muscle. 
display cabinets on respective days, tested for color, cooked in a water 
bath, kept in a chiller overnight and tested for texture. This procedure 2.6. Glycogen, lactate and total glycogen content 
was repeated for the 14 days PM samples. 
All samples were packaged in high oxygen modified atmosphere For the determination of glycogen content, 10 mg of frozen LL 
packaging (hiOxMAP; 80% O2, 20% CO2) during the simulated display. sample was homogenised in 100 μl of MilliQ water and boiled for 5 min 
The hiOxMAP packaging was conducted with a Multivac T200 (Sepp to inactivate enzymes. Samples were then centrifuged (Eppendorf, 
Haggenmüller GmbH & Co., Wolferschwenden, Germany) connected to Centrifuge 5417C, USA) for 5 min at 13,000 x g to remove insoluble 
2
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
material. The supernatant from each sample was plated in duplicate and 3.2. Muscle pH and temperature decline 
compared to glycogen standards using the colorimetric protocol detailed 
by the commercial glycogen assay kit (MAC016A, Sigma-Aldrich, St. The effect of age of the animal on pH and temperature measurements 
Louis, MO 63103, USA). Absorbance was measured at 570 nm using a is presented in Fig. 1 and pH and temperature in LTL muscle at different 
micro-plate reader (QuantStudio 1, appliedbiosystems, Thermo Fisher time points is shown in Figs. 2 and 3. The ultimate pH of the LL of 9MO 
Scientific, USA) in order to calculate total glycogen concentration of was higher compared to 2YO goats (Table 1; P < 0.001). The predicted 
each sample. pH@Temp18 (Table 1) was higher in 9MO compared to 2YO (P <
For lactate content, 50 mg of sample was homegenised with 4 vol- 0.001). However, both age group goats showed pH@Temp18 above 6. It 
umes of the lactate assay buffer, and centrifuged for 10 min at 13,000 x was not possible to report Temp@pH 6 as none of the goats had reached 
g. Supernatant was plated in duplicate and compared to lactate stan- pH 6 in the optimum temperature range. 
dards using the colorimetric protocol detailed by the commercial lactate 
assay kit (MAC064, Sigma-Aldrich, St. Louis, MO 63103, USA). Absor- 3.3. Muscle glycogen and lactate content 
bance was measured at 570 nm using the micro-plate reader. Total 
glycogen content (μmol/g) was calculated as the sum of muscle glycogen The glycogen content (μmol/g) in LL of both 9MO and 2YO goats is 
and lactate (μmol/g) (Knee, Cummins, Walker, & Warner, 2004). presented in Table 1. As shown in the table, glycogen content was lower 
in 9MO as compared to 2YO goats (P < 0.001). Similar trend was 
2.7. Statistical analysis observed with the lactate and total glycogen content (P < 0.01) (μmol/ 
g). 
All statistical analyses were performed using GenStat (16th Edition, 
VSN International Ltd., Hemel Hempstead, UK). All instrumental pa-
rameters were analyzed by the method of restricted maximum likeli- 3.4. Meat color during retail display 
hood (REML) due to multiple factors (age, days PM, display days) all 
with one experimental unit (carcass). This experiment was conducted as Age and display day influenced the LL lightness (L*) and redness (a*) 
a 2 × 2 × 3 factorial design to examine the effects of age, days PM and value with decreasing lightness and increasing redness with increasing 
display days on goat meat quality. The muscles were fixed; the allotment animal age (P < 0.01; Table 2). Further, there was an interaction be-
to treatments was randomized. For all instrumental measurements, an- tween age and display day such that the 9MO exhibited increase in a* 
imal age (9MO or 2YO), days PM (1 and 14 days PM), display days (0, 5 value over the display days (P < 0.01). However, in SM all the fixed 
and 10 day) were fitted as fixed effects. The rate of pH decline with time effect terms had effect (P < 0.01) on a* and PM and display day had 
was analyzed by regression analysis models which fit exponential effect on L* (P < 0.001). In addition, the interaction effect between age 
curves. This firstly fits a single curve of the form A + BRX, where A, B and and PM, and age and display day were also present in SM (P < 0.001). L* 
R stand for estimates of parameters for the fitted curve. It then adds age increased from 0 to 10 days in both muscle and in both PM days (P <
to the model, thus producing separate values of A for 9MO and 2YO 0.001). PM duration also increased the L* value in SM (P < 0.001). Also, 
goats. The pH at temperature 18 (pH@temp18) was predicted for each the interaction between age and PM is evident from Fig. 4, wherein 
carcass, rather than temperature at pH 6, as the 9MO failed to attain pH brown discoloration from bright cherry red color occurred in the 14 
6 at 24 h. The standard errors were then calculated for each group. days PM 2YO but not in 14 day PM 9MO goat meat. The influence of 
Multiple comparison was done using Tukey’s test for within the group muscle (P < 0.01) on a* is illustrated in Fig. 5 with higher value in LL 
variations. When significant by ANOVA at P < 0.05, the means were muscle compared to SM. The yellowness value generally increased from 
separated by LSD test. 0 to 10 days on display in both muscle (P < 0.001). PM also increased the 
3. Results 
3.1. Carcass characteristics 
The carcass characteristics of the 9MO and 2YO goats used in this 
experiment are shown in Table 1, with higher live weight, hot carcass 
weight, DP and GR fat depth for 2YO (P < 0.001 for all). 
Table 1 
Effect of age group [2YO (2 yrs. old) and 9MO (6–9 months old)] on carcass 
characteristics, glycogen, lactate, and total glycogen content in longissimus 
thoracis et lumborum (LTL). LW Live weight, HCW Hot carcass weight, DP dres-
sing percentage, GR fat depth, the total tissue depth 110 mm from the spine over 
the 12/13th rib. Values are predicted means.  
Traits 2YO 9MO SED P-value 
LW (kg) 45.8 29.0 1.19 < 0.001 
HCW (kg) 18.9 11.3 0.52 < 0.001 
DP 41.3 38.9 0.60 < 0.001 
In GR fat depth (mm) 5.5 3.7 0.40 < 0.001 Fig. 1. pH and temperature of M. longissimus for 2YO (2 yrs. old) (x) versus 
pH@Temp18 6.7 7.1 0.04 < 0.001 9MO (6–9 months old) (□) goats with the speculative ‘ideal’ pH/temperature 
pH 24 5.8 6.1 0.06 < 0.001 window shown as the solid black line (pH/temperature window defined as 
Glycogen (μmol/g) 27.4 11.6 3.81 < 0.001 temperature at pH 6 in the M. longissimus < 35 ◦C and > 18 ◦C). The dotted lines 
Lactate (μmol/g) 43.5 32.8 8.86 0.25 represent the cold-shortening window (pH > 6 and temp <10 ◦C) and it should 
Total glycogen content (μmol/g) 70.8 43.8 8.81 0.01  be noted that majority of the carcasses passed through this window. 
3
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
7.5
9MO 2YO
7.0
6.5
6.0
5.5
5.0
0.5 1 2 3 4 6 8 24
Time post-mortem (h)
Fig. 2. Effect of slaughter age [2YO (2 yrs. old) and 9MO (6–9 months old)] (P 
< 0.01) on post-mortem pH decline of M. longissimus. Vertical bars represent 
standard errors. 
25
20 9MO 2YO
15
10
5
0
0.5 1 2 3 4 6 8 24
Time post-mortem (h)
Fig. 3. Effect of slaughter age [2YO (2 yrs. old) and 9MO (6–9 months old)] (P 
< 0.01) on post-mortem temperature decline of M. longissimus Vertical bars 
represent standard errors. 
b* with increasing duration in LL (P < 0.001) and SM (P = 0.07), 
although age did not show much effect. Hue angle (h) showed a similar 
trend in both muscles with an increase on the 5 day of display and 
decrease on 10 day of display. This was evident in both 0 and 14 days PM 
meat. This trend was however not significant. Chroma (C*) showed an 
opposite trend with a decrease on the 5 day of display and increase on 
10 day of display, which was also evident in both muscle and both PM 
periods. Age, PM and age x PM interactions on C* were significant in 
both LL and SM (P < 0.001; Table 2). 
3.5. Lipid oxidation assay 
Fig. 6 illustrates the effect of all treatments on the amount of MDA 
produced per kg of muscle in LL of Boer goat during the simulated retail 
display. Among the fixed factors, lipid oxidation expressed as TBARS 
(mg MDA/ kg), was affected by age, days PM and retail display period in 
LL muscle of Boer goats (P < 0.01; Fig. 6). Similar results were observed 
in SM muscle, with effect of age (P < 0.01), PM (P < 0.05) and display 
days (P < 0.01) on lipid oxidation. Additionally, age x PM, display day x 
PM, and age x PM x display day interactions were present in both the 
muscles (P < 0.01). 
3.6. Cooking loss 
Cooking loss of the 1 and 14 days PM samples are presented in 
Table 3. For cooking loss, there was a significant interaction between 
age and retail display days such that cooking loss decreased with the 
increasing retail display period only in the 9MO goats LL, which ranged 
from around 26% for 0 day display to 18% for 10 days display irre-
spective of PM days (Table 3). However, in SM the effects of age, days 
PM and display days on cooking loss were not significant. Although a 
4
Temperature
pH
Table 2 
Effect of slaughter age [Age; 2YO (2 yrs. old) and 9MO (6–9 months old)], days post-mortem (PM: 1 and 14 days) and display days (DD:0, 5 and 10 days) on meat color (lightness L*, redness a*, yellowness b*, hue angle h, 
chroma C*) for the longissimus thoracis et lumborum (LL) and Semimembranosus (SM) during retail display of Boer goat meat. No significant interactions between age, PM and display days were observed at P = 0.05. Means 
within a row without a common superscript are significantly different (P < 0.05).  
Trait 2YO 9MO P-value  
1 day 14 days 1 day 14 days SED Age PM DD Age X PM Age X DD PM X DD  
0 5 10 0 5 10 0 5 10 0 5 10         
Longissimus thoracis et lumborum 
L* 30.6a 35.14bc 32.2ab 32.4ab 34.4bc 35.3bc 33.5abc 36.5c 34.3bc 33.0ab 35.1bc 34.3bc 0.74 0.020 0.313 <0.001 0.015 0.510 0.037 
a* 17.0abc 19.7bcd 18.2abcd 19.8bcd 21.9d 19.9bcd 15.2a 20.3cd 20.8cd 16.4ab 21.3d 20.9d 0.82 0.885 <0.001 <0.001 0.123 <0.001 0.642 
b* 13.8a 16.9bc 16.3abc 17.3bc 17.8bc 17.14bc 13.6a 16.9bc 18.07bc 15.1ab 17.6bc 18.9c 0.95 0.700 <0.001 <0.001 0.352 0.006 0.099 
H 39.9a 41.6a 43.2a 41.4a 39.7a 40.8a 40.8a 39.7a 40.9a 41.5a 39.1a 41.5a 1.33 0.320 0.558 0.065 0.277 0.413 0.190 
C* 22.2ab 26.5bc 24.8abc 26.1bc 28.3c 25.9bc 20.2a 26.5bc 27.4c 22.1bc 27.5c 28.0bc 1.38 0.003 <0.001 0.330 <0.001 0.339 0.833  
Semimembranosus 
L* 30.7a 32.2ab 32.4ab 34.3bcde 36.5de 35.8cde 33.5abc 33.8bcd 34.9bcde 35.0bcde 36.8e 35.6cde 0.60 0.072 <0.001 <0.001 0.005 0.364 0.780 
a* 18.8bc 17.6ab 14.7a 19.4bc 18.9bc 18.3bc 14.6a 19.0bc 16.6ab 14.6a 21.0c 16.5ab 0.97 <0.001 0.002 <0.001 0.001 <0.001 0.240 
b* 15.9bcde 14.8abcd 13.4ab 16.0cde 17.4e 14.7abcd 13.7abc 16.6de 15.1bcde 12.6a 17.1de 15.5bcde 0.53 0.121 0.070 <0.001 0.028 <0.001 0.024 
H 41.6a 41.9a 44.1a 40.4a 39.7a 40.4a 41.8a 40.8a 41.4a 39.4a 40.4a 42.6a 1.71 0.726 0.048 0.175 0.198 0.995 0.882 
C* 23.6bcde 22.3abc 19.5a 24.7cde 26.9e 22.9abcd 20.5ab 25.6cde 22.9abcd 19.7a 26.2de 23.0abcd 1.11 0.385 0.001 <0.001 <0.001 <0.001 0.082  
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
9 MO  1 day PM
9 MO  14 days PM
1.2
2 YO 1 day PM
2 YO 14 days PM i
1.0
0.8 gh
de de
0.6 eef h
fg
0.4 cd
b
0.2 bc
a
0.0
0 day 5 day 10 day
Display days
Fig. 6. Effect of slaughter age [2YO (2 yrs. old) and 9MO (6–9 months old)](P 
< 0.01), display time (P < 0.01) in high oxygen MAP (80%O2; 20% CO2 for 0, 5 
or 10 days respectively) and days post-mortem PM (1 or 14 days) (P < 0.01) on 
lipid oxidation (TBARS) in longissimus thoracis et. lumborum muscle of Boer 
Fig. 4. Visual illustration of meat packed in in high oxygen modified atmo- goats. Interactions of age x PM, PM x display day, and age x PM x display day 
sphere packaging (80% O2; 20% CO2), during the study illustrating the retail were P < 0.01. Vertical bars represent standard errors. 
color stability of 2YO (2 yrs. old) versus 9MO (6–9 months old) goats during 
two post-mortem days (1 and 14 days) over the simulated display period, of 0 to 
10 days. Note that the 0 day display samples were similar in color, the 5 day 4. Discussion 
samples were bright cherry red, and the 10 day samples showed substantial 
variation from red to brown. (For interpretation of the references to color in this This study investigated the effect of age of animal and post-mortem 
figure legend, the reader is referred to the web version of this article.) storage on meat quality of Boer goats. The salient findings of the 
research highlight that irrespective of the age group, the ultimate pH 
was higher than the normal ultimate meat pH of 5.4–5.7, which was 
LL SM
25 evident from the insufficient glycogen content in both age groups. Of 
23 prime importance is the finding that PM storage of goat meat for 14 days 
21
19 significantly tenderized the meat of both age groups. Display day and 
17 age of animal showed significant effect on the lightness, redness, yel-
15
13 lowness, and lipid oxidation. This is similar to the findings by Warner, 
11 Kearney, Hopkins, and Jacob (2017) who showed the major effects of 
9
7 display period on meat color stability and Calnan, Jacob, Pethick, and 
5 Gardner (2014) who showed the role of production factors on meat 
0 day 5 day 10 0 day 5 day 10 color. However, these studies were with lamb meat and the present 
day day
study has not established any relationship of lamb meat with goat meat 
2 YO 9 MO 2 YO 9 MO 2 YO 9 MO 2 YO 9 MO 2 YO 9 MO 2 YO 9 MO quality. Nonetheless, Sheridan, Hoffman, and Ferreira (2003) showed 
1 day PM Display days 14 days PM that Boer kid meat compares favorably with Mutton Merino lambs in 
terms of color, shear force and water-holding capacity. 
Fig. 5. Effect of muscle [SM, semimembranosus and LL, longissimus lumborum; (P 
< 0.01)], slaughter age [2YO (2 yrs. old) and 9MO (6–9 months old)](P = 0.29), 4.1. Carcass characteristics 
and days post-mortem (PM;1 or 14 days) (P < 0.01) on the redness (a*) in high 
oxygen MAP (80%O2; 20% CO2) over the display period of 0 to 10 days. In- The live weight and carcass weight of both age groups were similar to 
teractions of age x display day and muscle x display day were P < 0.01. Vertical previous studies on Boer goats of similar age groups by Yusuf, Goh, 
bars represent standard errors. 
Samsudin, Alimon, and Sazili (2014) and Silva, de Medeiros, Oliveira, 
and Gonzaga Neto (2016). The significant difference in GR fat depth 
similar trend of reduction in cooking loss was observed in 2YO goat between 9MO and 2YO goats (3.7 vs. 5.5) contributed mainly to the 
meat, this was not significant. rapid and extreme chilling of 9MO (Kannan et al., 2014). 
3.7. WBSF and compression 4.2. Muscle pH temperature decline 
The mean values of shear force for all treatments are presented in The postmortem muscle pH and temperature decline suggested rapid 
Table 3. Of the fixed effect terms, only PM and display days influenced chilling of carcasses (Pophiwa, Webb, & Frylinck, 2017). The occurrence 
(P < 0.01) the shear force in LL, with significant (P < 0.001) interaction of cold shortening in carcasses is generally dependent on the cooling rate 
effect between days PM and display days (Table 3). Whereas, in SM of a muscle and occurs if the muscle temperature drops below 10 ◦C 
muscle, days PM (P < 0.001) and display day (P < 0.001) influenced while the muscle is still in the pre-rigor state (Pophiwa et al., 2017). 
shear force, with an interaction (P < 0.05) between age and display days Higher pH@Temp18 demonstrated the severity of cold shortening in 
(P < 0.001). The effect of PM storage on both muscles were similar, with 9MO, which we related to the study in goats reported by MLA (2007), 
lower values for the 14 days PM meat of both 2YO and 9MO as expected. wherein they used pH@Temp18 as a cut off for cold-shortening. Many 
Overall, higher shear force values were observed for the 2YO goat’s SM researchers have related the high ultimate pH solely to the pre-slaughter 
muscle, as expected, although the variations were not significant. stress (Hashem, Hossain, Rana, Islam, & Saha, 2013; Kadim et al., 2010). 
Moreover, the reduction in LL shear force with increased days PM (1 day 
PM vs. 14 days PM) was higher in 2YO as compared to 9MO. Muscle also 
influenced the WBSF in Boer goat meat (P < 0.01; Fig. 7). 
5
Redness (a*)
TBARS (MDA mg/kg/LLmuscle)
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
Table 3 
Effect of slaughter age [Age; 2YO (2 yrs. old) and 9MO (6–9 months old)], days post-mortem (PM: 1 and 14 days) and display days (DD:0 and 10 days) on cook loss (% 
CL), Warner-Bratzler shear force (WBSF, kg) and hardness for the longissimus thoracis et lumborum (LL) and M. Semimembranosus (SM). No significant interactions 
between age, PM and display days were observed at P = 0.05. Means within a row without a common superscript are significantly different (P < 0.05).  
Traits 2YO 9MO P-value  
1 day 14 days 1 day 14 days SED Age PM DD Age X Age X PM X 
PM DD DD  
0 10 0 10 0 10 0 10  
Longissimus thoracis et lumborum 
CL (%) 29.5b 24.5ab 30.5b 27.3b 26.2b 18.0a 27.4b 18.6a 2.07 <0.001 0.160 < 0.598 0.027 0.760 
0.001 
WBSF (N) 69.1b 39.5a 35.5a 35.2a 61.8b 41.1a 36.2a 34.7a 3.10 0.646 < < 0.231 0.237 < 0.001 
0.001 0.001 
Hardness 47.8ce 40.0abcd 38.2ab 44.8bcde 39.2abc 33.5a 37.9ab 37.9ab 1.87 0.004 0.869 0.236 0.075 0.495 < 0.001 
(N) 
Semimembranosus 
CL (%) 22.9ab 27.8b 25.9b 23.8ab 22.2ab 23.7ab 25.4b 19.1a 2.10 0.088 0.544 0.617 0.927 0.056 < 0.001 
WBSF (N) 66.1b 34.1a 35.0a 30.3a 59.2b 34.1a 33.5a 20.7a 3.10 0.554 < < 0.244 0.244 < 0.001 
0.001 0.001 
Hardness 48.8d 46.8cd 47.1 cd 43.9bcd 44.1bcd 34.2a 38.7abc 37.3ab 1.95 <0.001 0.183 0.002 0.671 0.237 0.163  
(N) 
Lower muscle glycogen levels in animals in this study could be 
80 explained by the non-availability of sufficient good quality feed on-farm 
70 LL SM and the possible depletion of muscle glycogen due to preslaughter 
60 handling and the susceptibility of goats to inevitable ante-mortem stress 
50 associated with pre-slaughter handling and transportation (Archana 
40 et al., 2018; Kadim et al., 2010). Non-availability of quality fodder and 
30 insufficient feeding of animals prior to slaughter have been known to be 
20 the important contributor to antemortem glycogen depletion in rumi-
10 nants (Knee, Cummins, Walker, Kearney, & Warner, 2007). Similarly, 
0 day 10 day 0 day 10 day seasonal variation in muscle glycogen levels have been reported (Knee 
2 YO 9 MO 2 YO 9 MO 2 YO 9 MO 2 YO 9 MO et al., 2004) which again suggest a direct relationship between feed 
quality and quantity with the muscle glycogen levels. Previous research 
1 day PM 14 days PM
Display days has shown the reduced incidence of dark cutting in beef with high- 
energy supplement diets, by improving the muscle glycogen levels at 
Fig. 7. Effect of muscle [SM, semimembranosus and LL, longissimus lumborum; (P slaughter (Knee et al., 2004; Knee et al., 2007) and suggested that 
< 0.01)], slaughter age [2YO (2 yrs. old) and 9MO (6–9 months old)](P < supplementary feeding with high-energy diets could be executed as an 
0.05), and days post-mortem (PM;1 or 14 days) (P < 0.01) on the WBSF (N) of ‘on-farm’ preslaughter strategy to reduce dark cutting in beef. Similarly, 
Boer goat meat. Interactions of PM x display day was P < 0.01 and age x PM x Jacob, Pethick, and Chapman (2005) showed that lambs finished on 
display day was P < 0.05. Error bars represent standard errors. grain-based feedlot rations had higher muscle glycogen content 
compared to lambs finished on pasture and sucker lambs finished on 
4.3. Glycogen and lactate content pastures. 
A curvilinear relation exists between muscle glycogen content and 
Muscle glycogen concentration has been known to play an important lactate content (Chauhan & England, 2018). Lower glycogen reserves at 
role in post-mortem glycolysis and meat pH (England, Scheffler, Kasten, the time of slaughter leads to less lactate production (Sabow et al., 2017) 
Matarneh, & Gerrard, 2013; Pethick, Rowe, & Tudor, 1995). Glycolysis and less acidification of postmortem muscle. Accumulation of lactate in 
is one of the major biochemical processes that regulate the pH decline, post-mortem muscle is usually considered a good indicator of the extent 
and ultimate pH (pHu) to some extent. Glycogen is the main source of and rate of glycolysis (Choe et al., 2008) (Ferguson & Gerrard, 2014) 
energy in postmortem muscle and the skeletal muscle transforms stored (Ferguson & Gerrard, 2014) (Ferguson & Gerrard, 2014) (Ferguson & 
glycogen into ATP, lactate, and ultimately H+ ions (Chauhan & En- Gerrard, 2014) (Ferguson & Gerrard, 2014) (Ferguson & Gerrard, 2014). 
gland, 2018). The formation of H+ ions results in a drop in the muscle In our study, higher lactate content was observed in 2YO goat meat 
pH from 7.2 in living muscle to a pH near 5.5 in meat under normal compared to 9MO meat, which was in accordance with the glycogen 
conditions (Scheffler, Park, & Gerrard, 2011). When muscle contains content. It is usually associated to the pre-slaughter stress (Kadim et al., 
low level of glycogen at slaughter, it results in limited pH decline and 2010; Kannan et al., 2003; Nikbin, Panandam, & Sazili, 2016). The 
high meat pH, called dark firm and dry meat (DFD) in pig and poultry lactate levels observed in this study are comparable to lactate content of 
and dark-cutting in ruminants (Chauhan & England, 2018). In this goat meat reported by Pophiwa et al. (2017) and Nikbin, Panandam, & 
study, lower glycogen content in 9MO as compared to 2YO, indicated Sazili, (2016) in Boer goats and Simela, Webb, and Frylinck (2004) in 
glycogen depletion in these animals. Moreover, this was in line with our South African indigenous goats, though not enough to achieve normal 
results for pH24 as pH24 was higher in 9MO compared to 2YO. Of sig- ultimate pH. 
nificance is the finding that in the current study, glycogen content in 
both goat groups was relatively low, below the critical threshold of 
45–55 μmol/g (Warriss, 1990). This could be the major factor respon- 4.4. Meat color during retail display 
sible for the high pH24 in the goats irrespective of the age group. Similar 
results of lower glycogen content were also previously reported by The visual illustration of the changes in meat color during the study 
Pophiwa et al. (2017), Kannan et al. (2014) and Kannan, Kouakou, (Fig. 2) illustrates the higher color stability of meat from 9MO goats, 
Terrill, and Gelaye (2003) in goats. most likely due to lower myoglobin content (Warner et al., 2017) and 
higher oxidative capacity (Calnan et al., 2014). Previously, the color 
6
WBSF (N)
A. Abhijith et al.                                                                                                                                                                                                              M   e a  t  S  c i e  n  c e 175 (2021) 108466
stability of sheep meat, measured by oxymyoglobin to metmyoglobin major process responsible for the quality deterioration of meat and meat 
ratio, has been shown to reduce between the ages of 8 and 22 months products by reducing shelf life and producing rancid off-flavors and taste 
(Warner, Ponnampalam, Kearney, Hopkins, & Jacob, 2007). The higher (de Lima Júnior, do Nascimento Rangel, Urbano, & Moreno, 2013). In 
color stability is likely to be associated with the higher ultimate pH of our study, the peak value of MDA in LL was on the last day of display, 
the 9MO goats in our study as Warner et al. (2007) showed in lambs that being day 10, in both 1 and 14 days PM meat for both age groups. 
rectus femoris with higher ultimate pH actually had better color stability Although, a general trend of higher lipid oxidation with time in display 
than muscles of lower pH, as measured by redness a* and also oxy- as observed in the meat of 2YO goats compared to the 9MO in both 1 and 
myoglobin/metmyoglobin ratio. Previously, Ledward, Dickinson, 14 days PM samples, this was not uniform throughout the display days. 
Powell, and Shorthose (1986) had attributed this positive relation of Notably, the peak value of lipid oxidation in LL during the display days 
high ultimate pH (> 5.8) to color stability to the rate of autoxidation of did not exceed the critical value of 2 mg/kg, defined by Campo et al. 
myoglobin decrease and the enzymatic reducing system being more (2006) as a limit for perception of rancid taste in red meats by con-
active with increasing pH in beef. Also, increased metmyoglobin sumers. Similarly, in SM muscle the TBARS peak value occurred in 14 
reducing activity and decreased lipid oxidation are associated with days PM meat of 2YO goats on the last day (day 10) of simulated display. 
improved color stability (Mancini & Ramanathan, 2014). Our results However, the value exceeded the critical value as it reached 2.3 mg 
could be also related to the finding in old Merino sheep that have a MDA/kg. This could be in fact related to reports of Frank et al. (2017) 
higher muscle myoglobin concentration and higher oxidative capacity and Warner et al. (2017) in lambs who observed the reduced stability of 
(Gardner et al., 2007). Higher oxidative capacity is in turn related with SM muscle in hiOxMAP packed meat. Overall, regardless of the age and 
higher levels of isocitrate dehydrogenase levels (Calnan et al., 2014) and PM period, lipid oxidation progressed in goat meat with display time. 
has reduced color stability. Similar increase in TBARS with postmortem chill storage have been 
Lower L* and higher a* values for 2YO goats are similar to the previously reported in LL of pork (Haak, Raes, Van Dyck, & De Smet, 
findings reported by Polidori, Pucciarelli, Cammertoni, Polzonetti, and 2008), LL and SM of mutton (Popova & Marinova, 2013) and gluteus 
Vincenzetti (2017), who found similar results in older lambs compared medius muscle of goat meat (Adeyemi, Shittu, Sabow, Ebrahimi, & Sazili, 
to younger ones. Lightness of meat has an inverse relationship with 2016). Lipid oxidation is highly associated with the pigment oxidation 
heme iron content, which increases as slaughter age increases in lamb due to production of free radicals and reactive oxygen species (Faust-
(Bures & Barton, 2012; Mancini & Hunt, 2005; Warner et al., 2007). A man, Sun, Mancini, & Suman, 2010). Lipid oxidation enhance 
recent study in two age groups of Korean native black goat (9 months myoglobin oxidation (Lin & Hultin, 1977) and reduce surface redness. 
and 18 months) reported a similar observation. The authors attributed This is evident from our results of higher lipid oxidation values (Fig. 3) 
the higher redness and lower lightness in the 18 months old goats to the in the 10 day of display and the discoloration of meat during this period 
higher number of type I muscle fibers and thicker perimysium (Bakhsh, (Fig. 2). 
Hwang, & Joo, 2019). Conversely, and as would be expected, redness of 
meat increases with haem iron content and both increase with age of the 4.6. Cooking loss 
animal (Warner et al., 2007). L* increased from 0 to 10 days in both 
muscles and in both 1 and 14 days PM meat. However, the effect of PM The lower cooking loss in the 9MO, which further reduced with 
days on L* value was evident only in SM with higher value observed in display days could be associated with the higher ultimate pH (Li et al., 
14 days PM meat than 1 day PM meat. It has been previously studied 2014). Our result was similar to the findings in goats and lamb (Cetin, 
that higher L* with increasing PM period is associated with reduction of Bingol, Colak, & Hampikyan, 2012), which stated that the muscle pH 
mitochondrial respiratory activity, which increases oxygenation of the affected cooking loss, but not by PM period. In addition, the increased 
myoglobin molecule, resulting in greater formation of oxymyoglobin cooking loss with increasing age in our study agreed with findings of 
(Vitale, Pérez-Juan, Lloret, Arnau, & Realini, 2014). An increase in Schönfeldt and Strydom (2011) who hypothesized that increased cross- 
lightness is explained as the changes in relative contents of chemical linking of collagen with age results in decreased water-holding capacity, 
forms of myoglobin, and increased light scattering due to protein due to increased moisture loss upon heating or cooking. 
denaturation (Peng et al., 2019). Peng et al. (2019) showed that the 
increased lightness in hiOxMAP meat during storage indicates that meat 4.7. WBSF and compression 
loses the satisfactory color in meat. 
The yellowness value generally increased from 0 to 10 days on As expected, the highest shear force values were observed in the 2YO 
display in both muscles. PM days also increased the b* with increasing goat meat that was 0 d aged. This could be associated with smaller 
duration in LL and SM, although age did not show much effect. Previ- extent of post-mortem proteolysis, bigger size of muscle fibers (Torn-
ously, it was studied that b* values are associated to onset of brown berg, Von Seth, & Göransson, 1994), presence of mature collagen cross- 
pigmentation, and unacceptable appearance in meat is related to more link (non-reducible cross-link) in advanced animal slaughter age 
pronounced yellow tint, which depends on the relative balance of a* and (Mashele, 2017; McCormick, 1994). The presence of heat stable collagen 
b* (O’Sullivan et al., 2003). There was no effect of any of the treatments cross-links limits the solubility of collagen in meat from mature sheep, 
on h value in either of the muscles. However, it is to be noted that in SM, even at higher temperature (Light, Champion, Voyle, & Bailey, 1985). 
C* showed a trend of decrease from 5 to 10 days of display (P < 0.001), There was a marked increase in tenderness in this study after 14 days PM 
although not evident in LL. This finding was similar to the result re- in both age groups, as previously reported by Teixeira, Pereira, and 
ported by Frank et al. (2017) in hiOxMAP packaged SM muscle in lamb. Rodrigues (2011). It is well known that ageing promotes tenderization of 
Noticeably, increasing L* and b* and decreasing C* marked formation of meat (Marino, Della Malva, & Albenzio, 2015). In general, meat 
corresponding brown-color indicating partial oxidation of some of the tenderization is mainly due to ultrastructural changes that weaken the 
pigment to metmyoglobin, with (Mancini & Hunt, 2005). This finding integrity of the myofibers in the muscle tissue (Li et al., 2014). On the 
could clearly be related to the results of Frank et al. (2017) who did other hand, the toughness of meat has been attributed to low activity of 
similar hiOxMAP packaging in lamb meat. proteolytic enzymes in muscle samples, especially calpains, which are 
considered to play a key role in the degradation of specific muscle 
4.5. Lipid oxidation assay proteins (Marino et al., 2015; Saccà, Corazzin, Bovolenta, & Piasentier, 
2019). Also, lower activity of the proteolytic enzymes (calpains and 
Oxygen exposure is an essential factor contributing to lipid oxidation caspases) and higher activity of calpastatin with age contribute to the 
during storage (Amaral, Silva, & Lannes, 2018), especially in hiOxMAP higher toughness in older goats (Saccà et al., 2019). The role of myofi-
packaging, which was used in the present study. Lipid oxidation is the brillar or cytoskeletal protein degradation during refrigerated storage to 
7
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meat tenderness is studied (Adeyemi et al. 2016). Proteins such as titin Bonny, S. P., O’Reilly, R. A., Pethick, D. W., Gardner, G. E., Hocquette, J. F., & Pannier, L. 
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