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2.4
Oxidative stability
2.4.1
Fat extraction
Lipid extraction was conducted based on Kinsella
et al. (1977) with some modification. The obtained
fat was directly used for analysis or stored in the
airtight amber bottle and flushed in N2 gas and
stored at 4°C until used. (Kinsella, Shimp, Mai &
Weihrauch, 1977)
Table 1. Effect of nanostructured ginger rhizome and
synthetic antioxidant marination on pH value.
Day/Sample 0
3
6
9
12
C
6.46aE
6.64aD
6.76bC
6.92aB
7.17aA
MG
6.37cD
6.49bC
6.78aB
6.85bA
6.85bA
SM
6.42bD
6.42cD
6.46cC
6.56cB
6.73cA
NG
6.09eE
6.16eD
6.21eC
6.25eB
6.33eA
BHA/BHT
6.11dE
6.30dD
6.37dC
6.51dB
6.67dA
2.4.2
Peroxide Value (PV)
The Peroxide Value (PV) was conducted accord-
ing to the method by (AOAC, 2002). The peroxide
value was calculated as follows:
Value are expressed as mean
3).
Values marked by the different superscript letters within
a column (a-e) and (A-E) within a row denote statistically
differences (p .05).
±
standard deviation (n
=
Peroxide value (PV) =
Vs - Vb × T × 10
3
× 2 Weight of sample (g)
all the samples gradually increased during storage
at 4°C for 12 days of chill storage. The pH value
showed significantly (p
Where: Vs = Volume in ml titration for sample
Vb = Volume in ml titration for blank
T = Molarity of sodium thiosulphate
The PV expressed as miliequivalents of peroxide
oxygen per kilogram of sample (mEq/kg).
.05) higher values in C
sample and the lowest observed in NG marinated
chicken thigh throughout the study period. The
sample that depicted higher pH value may attribute
to higher degree of oxidation (Lingaiah & Reddy,
2001). Chicken thigh treated with nanostructured
ginger rhizome powder (NG) had the best effect
with highest pH value of 6.33 while that of control
reaching pH of 7.12 after 12 days of chilled stor-
age. The pH increment could be due to microbial
activity in meat. Nanostructured ginger rhizome
treatment exhibited lowest pH among all treated
samples during chilled storage.
<
2.5
Statistical analysis
All experiments were carried out in triplicate and
presented as mean and standard deviation. One-
way analysis of variance (ANOVA) was used to
analyze the data using SPSS statistical software
(version 21 SPSS Inc., USA). The means were
compared with Duncan's multiple comparison test
(DMCT) and p < .05 was considered as statistical
significance.
3.2
Color changes determination
Effect of treatment and days of storage on color
stability of marinated chicken thigh is shown in
Table 2. In general, the L* value was in the range
of 51.68 to 57.44 which was the expected lightness
value for spent hen meat. This indicates the fresh-
ness for all tested sample at 0 day of chilled storage.
Perhaps, the L* value obtained were comparable
to the one reported previously, where L value for
spent hen
Pectoralis major
muscle was around
52.51 (Chueachuaychoo, et al., 2011). However,
obviously higher degree of lightness showed in
NG sample compared to other samples (p < .05).
Nanostructured ginger rhizome used in this study
was very fine (nanoscale) and light cream in color.
Therefore, it was expected that chicken thigh
treated with nanostructured ginger rhizome ha d
different color from the other samples.
The L* value slightly decreased throughout the
storage period but no differences were detected
between 3 to 9 days of chilled storage, but drasti-
cally reduced after storage for 12 days with C sam-
ple exhibiting lowest L value with the rate of color
degradation were in between 16.57 percent to 21.66
percent for treated samples and 25.33 percent in C
3
RESULTS AND DISCUSSION
3.1
pH changes
Meat pH has a profound influence on meat quality
since changes in pH relatively caused protein dena-
turation and affect the quality attributes such as
color and water holding capacity. The comparative
pH value of tested samples is presented in Table 1.
Initially the muscle pH value were in the ranged
of 6.09 to 6.46 which indicate that all pH values
were within the expected range for normal spent
hen. The ultimate pH of raw spent as reported by
Chueachuaychoo et al. (2011) was around 6.10.
Generally, at the early stage of storage there were
significantly lower pH values (in range of 6.09 to
6.42) for treated samples compared to control sam-
ple (6.46 ± 0.007). It showed that ginger rhizome
powder and synthetic antioxidant BHA: BHT
decreased the initial pH of marinated chicken
thigh. Kim et al. (2009) reported lower pH in the
tested sample that contains dietary garlic com-
pared to control sample. However, the pH values of
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