Effects of α-tocopherol and citric acid on the oxidative stability of alimentary poultry fats during storage at low temperatures

Figures & data

Table 1. Changes in quality parameters of goose fat and goose fat with added antioxidants stored at two different temperatures.

	Goose fat			Goose fat with 0.1% α-tocopherol			Goose fat with 0.1% citric acid
Days of storage	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)
at +4°C
0	1.10^k ± 0.01	0.60^m ± 0.06	84.7^a ± 0.3	1.11^ij ± 0.03	0.62^j ± 0.05	84.5^a ± 0.2	1.10^j ± 0.02	0.59^j ± 0.03	84.2^a ± 0.5
60	2.03^j ± 0.03	1.76^l ± 0.01	83.4^ab ± 0.4	1.73^i ± 0.03	0.92^ij ± 0.01	84.1^a ± 0.5	1.83^i ± 0.04	1.07^i ± 0.07	83.8^a ± 0.6
120	3.80^hi ± 0.02	3.24^jk ± 0.02	81.8^bc ± 0.1	2.81^h ± 0.05	1.77^i ± 0.04	83.1^b ± 0.4	2.97^h ± 0.03	1.98^h ± 0.06	83.3^ab ± 0.4
180	7.33^g ± 0.05	4.87^hi ± 0.04	80.7^de ± 0.3	4.02^g ± 0.07	2.90^h ± 0.07	82.3^bc ± 0.2	4.25^fg ± 0.06	3.01^g ± 0.01	82.0^bc ± 0.1
240	9.51^ef ± 0.04	7.25^fg ± 0.03	78.5^f ± 0.2	5.70^f ± 0.01	4.37^gh ± 0.06	80.4^c ± 0.3	5.92^ef ± 0.05	4.52^fg ± 0.04	79.8^c ± 0.2
300	11.14^d ± 0.06	9.02^de ± 0.05	76.2^g ± 0.4	7.79^e ± 0.02	6.02^f ± 0.03	78.3^d ± 0.2	7.81^e ± 0.01	6.23^e ± 0.02	77.5^de ± 0.3
360	12.70^c ± 0.01	10.84^d ± 0.07	74.3^h ± 0.5	9.78^cd ± 0.04	7.88^de ± 0.02	76.7^e ± 0.1	9.92^cd ± 0.07	7.96^de ± 0.05	75.8^ef ± 0.2
420	14.04^bc ± 0.03	12.75^c ± 0.01	71.7^i ± 0.3	11.75^c ± 0.03	10.05^c ± 0.05	75.6^ef ± 0.1	11.94^b ± 0.04	10.12^c ± 0.07	74.4^g ± 0.2
450	14.74^b ± 0.05	13.62^b ± 0.06	71.1^ij ± 0.4	12.68^b ± 0.05	11.14^b ± 0.07	74.8^g ± 0.4	13.01^ab ± 0.05	11.39^b ± 0.04	73.1^h ± 0.4
480	15.11^a ± 0.01	14.59^a ± 0.03	70.7^jk ± 0.1	13.46^a ± 0.02	12.25^a ± 0.04	74.1^gh ± 0.3	13.73^a ± 0.01	12.51^a ± 0.03	72.2^hi ± 0.5
at –20°C
0	1.10^k ± 0.01	0.60^m ± 0.06	84.7^a ± 0.3	1.11^ij ± 0.03	0.62^j ± 0.05	84.5^a ± 0.2	1.10^j ± 0.02	0.59^j ± 0.03	84.2^a ± 0.5
60	1.51^kj ± 0.02	1.32^l ± 0.03	83.9^ab ± 0.2	1.23^ij ± 0.03	0.75^ij ± 0.02	84.2^a ± 0.4	1.44^i ± 0.04	0.97^hi ± 0.01	84.0^a ± 0.3
120	2.40^j ± 0.04	2.43^k ± 0.05	82.8^b ± 0.5	1.91^hi ± 0.01	1.31^i ± 0.05	83.7^ab ± 0.2	2.13^hi ± 0.02	1.55^h ± 0.07	83.5^ab ± 0.5
180	3.91^hi ± 0.06	3.81^j ± 0.02	81.3^c ± 0.4	2.75^gh ± 0.06	2.05^hi ± 0.04	82.8^b ± 0.5	2.95^h ± 0.07	2.31^gh ± 0.02	82.4^bc ± 0.1
240	6.58^gh ± 0.03	5.58^gh ± 0.04	79.2^de ± 0.1	3.71^g ± 0.05	3.09^h ± 0.07	81.0^bc ± 0.3	4.02^g ± 0.06	3.48^g ± 0.06	80.2^c ± 0.2
300	9.67^ef ± 0.07	7.52^ef ± 0.01	77.3^fg ± 0.1	5.60^f ± 0.07	4.15^gh ± 0.06	79.3^c ± 0.4	5.88^ef ± 0.05	4.69^fg ± 0.04	78.3^d ± 0.3
360	11.29^e ± 0.02	9.46^de ± 0.05	75.8^gh ± 0.2	7.10^e ± 0.04	5.37^f ± 0.01	78.1^d ± 0.2	7.59^e ± 0.03	5.99^e ± 0.03	76.9^de ± 0.5
420	12.51^cd ± 0.01	11.34^d± 0.07	74.6^h ± 0.4	8.40^d ± 0.03	6.67^ef ± 0.04	77.1^de ± 0.3	8.96^d ± 0.04	7.28^de ± 0.05	75.6^ef ± 0.4
450	13.24^c ± 0.03	12.22^c ± 0.04	73.6^hi ± 0.4	9.13^cd ± 0.01	7.26^de ± 0.05	76.6^e ± 0.3	9.65^cd ± 0.07	7.91^de ± 0.01	74.8^g ± 0.3
480	14.02^b ± 0.05	13.31^b ± 0.01	72.4^j ± 0.3	9.72^cd ± 0.02	7.89^de ± 0.03	76.0^ef ± 0.1	10.31^bc ± 0.01	8.64^d ± 0.04	74.1^gh ± 0.2

^aPV: peroxide value; TBARS: thiobarbituric acid reactive substances; IV: iodine value.

^bValues are expressed as mean ± standard deviation of three replicates for each parameter.

^cDifferent letters in the same column indicate statistically significant differences at p < 0.05 (Tukey’s test).

Table 2. Changes in quality parameters of duck fat and duck fat with added antioxidants stored at two different temperatures.

	Duck fat			Duck fat with 0.1% α-tocopherol			Duck fat with 0.1% citric acid
Days of storage	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)
at +4°C
0	0.82^j ± 0.02	0.51^l ± 0.05	79.5^a ± 0.4	0.78^ij ± 0.01	0.48^j ± 0.03	79.9^a ± 0.6	0.80^ij ± 0.04	0.45^j ± 0.01	79.7^a ± 0.2
60	1.84^i ± 0.05	1.65^jk ± 0.03	78.6^ab ± 0.5	1.61^i ± 0.02	0.77^i ± 0.02	79.1^a ± 0.1	1.72^i ± 0.06	0.89^ij ± 0.03	79.2^a ± 0.1
120	3.55^h ± 0.07	3.12^hi ± 0.04	77.3^bc ± 0.3	2.63^hi ± 0.04	1.51^hi ± 0.05	78.2^ab ± 0.5	2.76^ghi ± 0.01	1.63^hi ± 0.07	77.6^bc ± 0.3
180	7.13^f ± 0.06	4.96^g ± 0.01	75.5^cd ± 0.6	3.85^gh ± 0.01	2.59^h ± 0.04	76.7^c ± 0.3	3.96^fg ± 0.07	2.80^h ± 0.05	76.1^c ± 0.1
240	9.27^e ± 0.03	6.86^ef ± 0.07	73.2^d ± 0.6	5.46^fg ± 0.06	4.88^g ± 0.07	75.0^cd ± 0.6	5.68^ef ± 0.04	4.25^gh ± 0.06	74.5^d ± 0.2
300	10.86^d ± 0.05	8.87^de ± 0.06	70.6^ef ± 0.2	7.57^def ± 0.02	6.38^f ± 0.01	73.1^d ± 0.4	7.74^de ± 0.05	5.89^fg ± 0.04	72.6^de ± 0.5
360	12.41^c ± 0.04	10.92^c ± 0.05	68.3^f ± 0.1	9.42^cd ± 0.05	7.57^d ± 0.06	71.7^e ± 0.2	9.88^cd ± 0.01	7.89^cd ± 0.01	71.1^e ± 0.4
420	13.74^b ± 0.01	12.05^b ± 0.04	66.1^g ± 0.5	11.53^bc ± 0.01	9.77^c ± 0.07	68.9^f ± 0.4	11.76^bc ± 0.02	10.02^bc ± 0.02	68.2^f ± 0.1
450	14.39^ab ± 0.03	12.66^ab ± 0.02	65.2^h ± 0.4	12.45^ab ± 0.04	10.76^b ± 0.07	67.8^fg ± 0.3	12.69^ab ± 0.07	10.84^b ± 0.04	67.5^fg ± 0.1
480	14.86^a ± 0.08	13.37^a ± 0.01	64.1^i ± 0.2	13.24^a ± 0.03	11.88^a ± 0.03	66.7^g ± 0.1	13.51^a ± 0.04	11.71^a ± 0.05	66.9^g ± 0.3
at –20°C
0	0.82^j ± 0.02	0.51^l ± 0.05	79.5^a ± 0.4	0.78^ij ± 0.01	0.48^j ± 0.03	79.9^a ± 0.6	0.80^ij ± 0.04	0.45^j ± 0.01	79.7^a ± 0.2
60	1.22^ij ± 0.03	1.21^jkl ± 0.04	78.8^ab ± 0.6	1.02^ij ± 0.01	0.59^ij ± 0.06	79.3^a ± 0.2	1.20^hij ± 0.05	0.67^ij ± 0.05	79.1^a ± 0.4
120	2.13^hi ± 0.01	2.11^hij ± 0.01	77.6^bc ± 0.1	1.65^hij ± 0.02	1.04^hij ± 0.07	78.9^ab ± 0.6	1.94^hi ± 0.01	1.19^hij ± 0.01	78.2^ab ± 0.3
180	3.64^h ± 0.05	3.23^gh ± 0.03	76.0^c ± 0.2	2.43^hi ± 0.06	1.71^hi ± 0.05	77.1^bc ± 0.5	2.72^ghi ± 0.04	1.89^hi ± 0.07	76.5^c ± 0.1
240	6.25^fg ± 0.07	4.71^g ± 0.07	73.9^d ± 0.5	3.42^gh ± 0.08	2.75^h ± 0.04	76.1^c ± 0.3	3.81^fg ± 0.06	2.78^h ± 0.05	75.6^cd ± 0.2
300	9.36^e ± 0.06	6.80^ef ± 0.04	71.8^e ± 0.6	5.31^fg ± 0.04	3.89^gh ± 0.03	73.9^d ± 0.4	5.65^ef ± 0.07	3.99^gh ± 0.06	73.1^d ± 0.5
360	10.99^d ± 0.04	8.91^de ± 0.06	70.3^ef ± 0.4	6.85^efg ± 0.05	5.16^fg ± 0.02	72.2^de ± 0.3	7.17^def ± 0.02	5.03^fgh ± 0.01	71.6^e ± 0.4
420	12.21^cd ± 0.08	11.12^c ± 0.05	68.6^f ± 0.1	8.21^ef ± 0.07	6.46^ef ± 0.01	69.4^ef ± 0.1	8.32^cdef ± 0.01	6.36^ef ± 0.03	68.9^f ± 0.1
450	12.97^c ± 0.04	12.14^b ± 0.01	67.4^fg ± 0.2	8.97^cde ± 0.03	7.06^de ± 0.08	68.3^f ± 0.1	9.06^cde ± 0.04	6.97^de ± 0.04	67.8^fg ± 0.1
480	13.82^b ± 0.01	13.03^ab ± 0.03	66.3^g ± 0.1	9.42^cd ± 0.01	7.78^d ± 0.04	67.4^fg ± 0.2	9.88^cd ± 0.03	7.69^cd ± 0.02	67.1^fg ± 0.3

^aPV: peroxide value; TBARS: thiobarbituric acid reactive substances; IV: iodine value.

^bValues are expressed as mean ± standard deviation of three replicates for each parameter.

^cDifferent letters in the same column indicate statistically significant differences at p < 0.05 (Tukey’s test).

Table 3. Changes in quality parameters of chicken fat and chicken fat with added antioxidants stored at two different temperatures.

	Chicken fat			Chicken fat with 0.1% α-tocopherol			Chicken fat with 0.1% citric acid
Days of storage	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)	PV (meq O2/kg)	TBARS (mg MDA/kg)	IV (g I2/100 g)
at +4°C
0	2.30^n ± 0.02	1.08^m ± 0.05	96.8^a ± 0.2	2.28^j ± 0.04	1.07^k ± 0.06	96.6^a ± 0.3	2.26^kl ± 0.01	1.05^l ± 0.04	96.5^a ± 0.3
60	3.80^lm ± 0.06	2.76^l ± 0.01	95.1^b ± 0.4	2.83^ij ± 0.05	1.82^jk ± 0.02	96.4^a ± 0.2	2.97^k ± 0.02	1.97^k ± 0.06	95.9^b ± 0.3
120	6.35^jkl ± 0.07	4.66^jk ± 0.03	93.0^d ± 0.3	4.05^hi ± 0.04	2.94^j ± 0.04	94.3^c ± 0.1	4.34^j ± 0.01	2.84^j ± 0.05	93.8^d ± 0.4
180	9.46^hi ± 0.04	7.38^hi ± 0.04	90.6^f ± 0.1	5.46^gh ± 0.07	4.25^i ± 0.05	91.3^e ± 0.5	5.72^ij ± 0.05	4.15^i ± 0.07	91.1^f ± 0.2
240	12.61^g ± 0.03	10.2^fg ± 0.02	88.5^gh ± 0.2	7.29^ef ± 0.06	5.74^h ± 0.07	89.6^fg ± 0.4	7.51^gh ± 0.07	5.64^h ± 0.03	88.7^g ± 0.2
300	14.81^e ± 0.06	11.87^e ± 0.07	85.6^ij ± 0.2	9.61^d ± 0.03	7.56^fg ± 0.04	86.5^hi ± 0.3	9.88^ef ± 0.06	7.79^fg ± 0.04	85.9^i ± 0.1
360	16.82^d ± 0.01	13.39^d ± 0.06	83.4^jk ± 0.5	12.11^c ± 0.02	9.46^de ± 0.03	84.3^ij ± 0.3	12.38^d ± 0.04	9.68^de ± 0.02	83.8^j ± 0.1
420	18.01^bc ± 0.02	14.48^c ± 0.01	81.7^kl ± 0.4	13.41^b ± 0.04	11.47^c ± 0.02	82.6^j ± 0.2	13.74^b ± 0.03	11.73^c ± 0.01	82.2^k ± 0.4
450	18.61^b ± 0.07	15.26^b ± 0.04	80.3^lm ± 0.3	14.12^ab ± 0.01	12.58^b ± 0.01	81.4^k ± 0.1	14.46^ab ± 0.02	12.41^b ± 0.05	81.1^l ± 0.2
480	19.11^a ± 0.04	16.15^a ± 0.03	77.1^n ± 0.2	14.61^a ± 0.05	13.77^a ± 0.06	80.2^l ± 0.4	14.92^a ± 0.01	13.92^a ± 0.04	78.3^m ± 0.3
at –20°C
0	2.30^n ± 0.02	1.08^m ± 0.05	96.8^a ± 0.2	2.28^j ± 0.04	1.07^k ± 0.06	96.6^a ± 0.3	2.26^kl ± 0.01	1.05^l ± 0.04	96.5^a ± 0.3
60	3.21^m ± 0.01	2.04^lm ± 0.07	95.5^b ± 0.1	2.64^ij ± 0.03	1.53^jk ± 0.04	96.3^a ± 0.1	2.84^k ± 0.01	1.72^k ± 0.03	96.2^a ± 0.4
120	4.72^kl ± 0.03	3.56^kl ± 0.04	93.8^cd ± 0.4	3.54^hij ± 0.06	2.24^ijk ± 0.01	95.4^b ± 0.4	3.92^jk ± 0.04	2.45^j ± 0.02	95.1^b ± 0.3
180	6.81^jk ± 0.05	5.58^hi ± 0.06	91.2^ef ± 0.5	4.85^ghi ± 0.05	3.26^ij ± 0.02	93.5^d ± 0.5	5.24^ijk ± 0.02	3.16^ij ± 0.04	92.7^de ± 0.1
240	9.32^hij ± 0.07	7.79^gh ± 0.01	89.1^fg ± 0.3	6.24^fgh ± 0.07	4.43^i ± 0.03	91.1^e ± 0.3	6.47^hi ± 0.03	4.23^i ± 0.02	90.9^fg ± 0.2
300	12.43^g ± 0.04	10.18^fg ± 0.02	86.7^hi ± 0.2	7.75^def ± 0.02	5.62^h ± 0.05	88.7^gh ± 0.2	7.81^gh ± 0.06	5.78^h ± 0.01	88.3^g ± 0.4
360	14.52^ef ± 0.06	12.29^de ± 0.04	84.5^ij ± 0.3	8.86^de ± 0.01	6.82^fgh ± 0.07	86.4^hi ± 0.3	9.02^efg ± 0.06	6.95^fgh ± 0.03	85.1^i ± 0.2
420	16.11^de ± 0.06	13.98^cd ± 0.03	82.8^jk ± 0.4	9.78^d ± 0.03	7.81^efg ± 0.06	84.1^ij ± 0.4	9.87^ef ± 0.05	7.99^fg ± 0.06	83.6^j ± 0.2
450	16.01^de ± 0.05	14.66^bc ± 0.05	81.5^kl ± 0.1	10.45^cd ± 0.04	8.36^ef ± 0.06	82.9^j ± 0.1	10.65^def ± 0.01	8.59^f ± 0.05	82.1^k ± 0.3
480	17.93^cd ± 0.03	15.54^ab ± 0.07	80.1^lm ± 0.1	11.03^cd ± 0.02	9.17^e ± 0.02	81.7^k ± 0.1	11.34^de ± 0.07	9.42^ef ± 0.07	80.9^l ± 0.4

^aPV: peroxide value; TBARS: thiobarbituric acid reactive substances; IV: iodine value.

^bValues are expressed as mean ± standard deviation of three replicates for each parameter.

^cDifferent letters in the same column indicate statistically significant differences at p < 0.05 (Tukey’s test).

Table 4. Variations in fatty acid composition (% of total fatty acids) of fresh poultry fats and poultry fats with α-tocopherol stored at two different temperatures

Fatty acids	Goose fat			Duck fat			Chicken fat
	Control (fresh fat)	Goose fat with 0.1% α-tocopherol after 480 days of storage at +4°C	Goose fat with 0.1% α-tocopherol after 480 days of storage at –20°C	Control (fresh fat)	Duck fat with 0.1% α-tocopherol after 480 days of storage at +4°C	Duck fat with 0.1% α-tocopherol after 480 days of storage at –20°C	Control (fresh fat)	Chicken fat with 0.1% α-tocopherol after 480 days of storage at +4°C	Chicken fat with 0.1% α-tocopherol after 480 days of storage at –20°C
Myristic (14:0)	1.89 ± 0.03	2.18 ± 0.02	1.98 ± 0.03	2.18 ± 0.03	2.46 ± 0.02	2.29 ± 0.05	0.73 ± 0.03	0.87 ± 0.04	0.57 ± 0.04
Myristoleic (14:1)	1.47 ± 0.05	1.59 ± 0.06	1.49 ± 0.01	1.79 ± 0.05	1.92 ± 0.05	1.86 ± 0.04	0.50 ± 0.07	0.74 ± 0.09	0.63 ± 0.07
Pentadecanoic (C15:0)	2.65 ± 0.02	3.00 ± 0.05	2.85 ± 0.07	2.89 ± 0.02	3.11 ± 0.01	2.92 ± 0.02	1.63 ± 0.09	1.80 ± 0.06	1.66 ± 0.05
Palmitic (C16:0)	10.99 ± 0.01	11.54 ± 0.06	11.41 ± 0.02	11.41 ± 0.01	12.05 ± 0.06	11.34 ± 0.03	9.72 ± 0.08	10.12 ± 0.05	9.87 ± 0.01
Palmitoleic (C16:1)	11.13 ± 0.04	10.98 ± 0.01	11.08 ± 0.06	10.80 ± 0.04	10.68 ± 0.04	10.72 ± 0.06	8.09 ± 0.04	8.21 ± 0.03	8.13 ± 0.04
Hexadecadienoic (C16:2)	4.08 ± 0.05	3.77 ± 0.06	3.90 ± 0.06	3.78 ± 0.05	3.56 ± 0.06	3.75 ± 0.04	5.66 ± 0.09	5.60 ± 0.08	5.62 ± 0.02
Hexadecatrienoic (C16:3)	3.65 ± 0.02	3.44 ± 0.04	3.56 ± 0.01	3.25 ± 0.02	3.07 ± 0.03	3.22 ± 0.02	4.82 ± 0.05	4.76 ± 0.04	4.80 ± 0.06
Hexadecatetranoic (C16:4)	2.59 ± 0.04	2.28 ± 0.03	2.48 ± 0.06	2.17 ± 0.01	2.05 ± 0.01	2.10 ± 0.05	2.87 ± 0.01	2.81 ± 0.07	2.84 ± 0.08
Heptadecanoic (C17:0)	0.11 ± 0.05	0.32 ± 0.01	0.21 ± 0.05	0.09 ± 0.06	0.27 ± 0.05	0.22 ± 0.01	0.13 ± 0.04	0.38 ± 0.01	0.20 ± 0.03
Stearic (C18:0)	8.51 ± 0.01	8.93 ± 0.06	8.50 ± 0.06	8.93 ± 0.07	9.24 ± 0.03	9.06 ± 0.03	7.18 ± 0.06	7.68 ± 0.05	8.25 ± 0.09
Oleic (C18:1)	29.64 ± 0.03	28.75 ± 0.02	29.26 ± 0.01	29.30 ± 0.03	29.10 ± 0.01	29.60 ± 0.04	34.03 ± 0.01	33.91 ± 0.04	33.96 ± 0.05
Linoleic (C18:2)	19.82 ± 0.06	19.58 ± 0.04	19.69 ± 0.06	19.41 ± 0.02	19.08 ± 0.04	19.35 ± 0.02	20.80 ± 0.03	19.64 ± 0.02	19.89 ± 0.08
Linolenic (C18:3)	1.19 ± 0.02	1.14 ± 0.02	1.15 ± 0.05	1.25 ± 0.04	1.11 ± 0.05	1.20 ± 0.06	1.11 ± 0.08	0.95 ± 0.01	0.98 ± 0.04
Stearidonic acid (C18:4)	1.62 ± 0.05	1.50 ± 0.03	1.58 ± 0.03	1.41 ± 0.01	1.30 ± 0.03	1.37 ± 0.07	1.73 ± 0.06	1.53 ± 0.07	1.60 ± 0.01
Total SFA	24.15 ± 0.05	26.03 ± 0.06	24.95 ± 0.02	25.50 ± 0.04	27.13± 0.03	25.83 ± 0.01	19.39 ± 0.04	20.85 ± 0.06	20.55 ± 0.04
Total MUFA	41.90 ± 0.04	41.26 ± 0.03	41.59 ± 0.06	42.23 ± 0.02	41.70 ± 0.05	42.18 ± 0.06	42.62 ± 0.06	42.86 ± 0.01	42.72 ± 0.07
Total PUFA	32.95 ± 0.06	31.71 ± 0.02	32.46 ± 0.03	31.27 ± 0.01	30.17 ± 0.02	30.99 ± 0.03	36.99 ± 0.03	35.29 ± 0.08	35.73 ± 0.08
PUFA/SFA	1.36 ± 0.02	1.21 ± 0.05	1.30 ± 0.03	1.22 ± 0.06	1.11 ± 0.04	1.19 ± 0.05	1.90 ± 0.06	1.69 ± 0.05	1.83 ± 0.08

^aSFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.

^bValues are expressed as mean ± standard deviation of three replicates for each parameter.