Carcass Characteristics And Meat Quality Of Emus – A Pilot Study
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
Tamil Nadu Veterinary and Animal Sciences University
Abstract
A study on the carcass characteristics, meat quality traits including amino acid
profile, fatty acid profile and mineral content estimation along with organoleptic and
microbial quality of emu of the age groups 15 and 18 months were carried out. Eight
birds were slaughtered from each group. Value added products were prepared from
emu meat and compared with those made from beef and chicken. The
physicochemical properties were assessed at 0, 1 st , 2 nd and 7 th day. The samples were
kept in chiller (0°C ± 1°C) upto 1 st day and then in freezer (-18°C ± 1°C) upto 7 days
for further assessment. Quality traits were also analysed on three different muscle
regions, viz., drumstick, thigh and breast of emu.
Significant and progressive increase in live weight and carcass weight was
observed with increase in age whereas the meat: bone ratio decreased significantly.
Drip loss and cooking loss were higher in the 18 month age group. A mean dressing
percent of 65.06 and 67.95 in both the age groups was recorded. The mean per cent
yield of edible offals such as heart, liver, kidney and gizzard were 1.35 and 1.39, 1.43
and 1.45, 0.65 and 0.74, 1.18 and 1.22, respectively. The mean percent yield of
inedible offals, viz., recorded for blood, feather, skin, shank, head, lungs, intestines,
proventriculus, spleen, trachea, oesophagus and wings of 15 and 18 months age
groups were 1.20 and 1.63, 0.41 and 0.55, 2.81 and 3.19, 1.06 and 1.38, 0.31 and
0.36, 0.30 and 0.35, and 0.59 and 0.70, 0.15 and 0.07, 0.03 and 0.07, 0.14 and 0.16,
0.14 and 0.12 and 0.05 and 0.07, respectively.
There was a linear increase in the weights and yields of edible and inedible
offals with age. However, the yields of offals such as skin, head and intestines did not
differ significantly (P>0.05) with increase in age. A highly significant increase in the
yield of cut up parts such as neck, breast and rib and loin were observed with increase
in age, whereas a highly significant decrease in the weights of cut up parts such as
drumstick, thigh and rump was observed with increase in age. The increase in the
yields of fat and bone were highly significant in the 18 month age group.
The progressive fall in pH values (5.66 – 5.52) during the periods of storage in
chiller and freezer indicated the normal trend. Decrease in the water holding capacity
was observed with increase in chronological age and with storage periods. Different
muscle regions also showed a highly significant difference in the water holding
capacity. The R- value obtained in this study at 1 st day ranged from 1.06 -1.24 in both
the age groups indicating the onset of rigor mortis at chiller storage during this period.
The extract release volumes of both the age groups increased gradually and
consistently throughout the storage period. The thiobarbituric acid number and
tyrosine values increased significantly at different storage periods for both the age
groups and there was no significant difference in the tyrosine values between the age
groups.
The fibre diameters increased gradually as age advanced (14.35μm – 17.27
μm) and decreased with storage periods. The sarcomere length revealed significant
decrease as age advanced (2.92 μm – 2.23 μm) and increased with storage periods.
Significant difference was noticed in the myofibrillar fragmentation index between
the age groups and the myofibrillar fragmentation increased with storage. The
myoglobin percent, shear force values and collage contents increased significantly
with age. The drumstick region had the highest and the breast region the lowest
values.
Spectrophotometric assay of meat colour revealed that the younger age groups
had higher lightness (L * ), lower redness (a * ) and yellowness (b * ) values. Drumstick
region revealed to have minimal lightness (L * ) and intense redness (a * ) and the thigh
region was found to be intermediary. The breast region had the highest lightness (L * )
and lowest redness (a * ) values. Hue values were more in drumstick and the breast
showed more chroma values.
The texture profile values reflected the younger groups to have favourable
textural properties pertaining to tenderness of meat. The texture profile results
revealed that the younger age groups had decreased hardness, springiness,
cohesiveness, gumminess and chewiness values than the older birds. The texture
parameters also indicated drumstick to be a less tender region than the thigh and
breast.
There was increased percentage of moisture and protein observed in the
younger age groups. The fat and cholesterol percentages were very less in the younger
group which is of concern to nutritionists. The comparative analysis of the proximate
composition in emu, beef and chicken meat revealed that emu meat had the highest
protein and lowest fat and cholesterol percentage.
The saturated fatty acids were significantly higher in the older age groups. The
monounsaturated and polyunsaturated fatty acids were more in the younger age
groups. Oleic acid (C18:1) was the predominant monounsaturated fatty acid and the
polyunsaturated fatty acids such as the linoleic (C18:2) and linolenic (C18:3) were all
significantly higher in the younger groups.
It was observed that the mineral contents between the muscle regions as well
as between the age groups of emu birds differed with high significance. The minerals
magnesium, calcium, sodium and zinc were found to be more in younger animals than
the older groups.
The emu meat from the younger age groups exhibited higher scores for all the
sensory parameters. Decreased scores for tenderness and juiciness were given to the
older age groups by the sensory panelists. Microbiological quality revealed no
significant difference (P>0.05) between the two age groups.
Between the products of emu, beef and chicken, emu sausages and nuggets
exhibited less intense colour. The texture profile analysis of the products revealed a
highly significant difference (P<0.01) between the products as well as between the
different species. Emu products exhibited lesser values of all the textural attributes
than beef but were more than chicken. Emu sausages and nuggets exhibited more
stability and product yield values than beef and lower values than chicken.
Emu products received more panelists score compared to beef in appearance,
tenderness and juiciness. Microbial quality of the products prepared from emu, beef
and chicken showed a significantly higher difference in the microbial counts at
different storage periods. However, the counts were within the acceptable limits.
Hematoxylin and Eosin stained muscle tissue sections of emu, beef and chicken
revealed that the fibre diameters of emu tissues (12 μm – 14μm) were similar to that
of chicken (11 μm - 13μm) than beef (23 μm - 30μm).
The results of the study indicated that emu of 15 months age group can be
advocated for meat production considering the various favourable characteristics like
meat : bone ratio, high meat yield (drumstick and thigh cuts), reduced drip loss and
cooking loss, and the meat quality traits like pH, water holding capacity, R – value,
extract release volume, thiobarbituric acid number, tyrosine value, fibre diameter,
sarcomere length, myofibrillar fragmentation index, myoglobin percent, shear force
value and collagen content, instrumental analysis of colour, texture profile analysis,
proximate composition and cholesterol content, amino acid profile, fatty acid profile,
mineral content. The organoleptic scores also were supportive to the 15 month age
group. The comparison of value added products were favourable to emu meat.