Evaluation of the antioxidant activity of Betula pendula leaves extract and its effects on model foods

Figures & data

Table 1. Polyphenol composition identified in methanol extract of BP using LCMS.

No.	tR (min)	Molecular formula	[M-H]^-	Proposed compound
1	14.2	C15H14O6	298.0718	catechin
2	17.3	C9H8O3	163.0401	p-coumaric acid
3	29.31	C15H10O8	317.0303	myricetin
4	31.6	C15H10O7	301.0354	quercetin
5	32.8	C15H12O5	271.0612	naringenin

Table 2. Soluble concentration, polyphenol content and antioxidant activity of BP extracts.

Activity of Betula pendula	Extraction solvent
	90:10 (v/v) EtOH:H20	75:25 (v/v) EtOH:H20	50:50 (v/v) EtOH:H20
	Soluble concentration (g/L)	19.83 ± 0.05^a	20.1 ± 0.02^b	22.6 ± 0.05^c
Total phenolic content  (mg GAE/g DW)	10.8 ± 0.05^a	9.11 ± 0.03^b	11.23 ± 0.02^ac
FRAP (mmol of TE/g DW)	1.59 ± 0.02^a	1.06 ± 0.06^b	1.52 ± 0.01^ac
TEAC (mmol of TE/g DW)	1.27 ± 0.05^a	1.36 ± 0.03^ab	1.45 ± 0.02^bc
ORAC (mmol of TE/g DW)	1.56 ± 0.05^a	1.67 ± 0.05^b	2.81 ± 0.03^c

Values are mean ± standard deviation (n = 3).

GAE: gallic acid equivalent; TE: trolox equivalent; DW: dry weight.

^a–cMeans within a row with different letters are significantly different (p < 0.05).

Figure 1. Area of the electron paramagnetic resonance (EPR) spectra of the radical adduct DMPO-OCH₃ generated from a solution of H₂O₂ [2 mM] and FeSO₄ [0.04 mM] with DMPO [14 mM] as spin trap in MeOH as solvent. The area of the EPR signal is plotted against concentration of BP methanolic extracts.

Table 3. The colour values of beef patties during refrigerated storage for 10 days.

	Time of storages (days)
Treatment	0	2	4	6	8	10
L*
Control	29.77 ± 0.87^a1	38.68 ± 1.50^a2	29.20 ± 0.326^a1	37.10 ± 1.23^a2	37.23 ± 0.45^a2	45.61 ± 2.22^a3
0.1% BHT	29.77 ± 0.87^a1	32.86 ± 1.78^b2	30.55 ± 0.967^b3	35.44 ± 1.06^b4	37.99 ± 1.19^a5	40.58 ± 0.46^b6
0.1% BP	29.77 ± 0.87^a1	34.47 ± 1.73^c2	30.91 ± 1.518^b3	37.30 ± 0.94^a4	41.02 ± 1.08^b5	40.98 ± 0.46^b5
0.3% BP	29.77 ± 0.87^a1	28.42 ± 1.58^d1	36.45 ± 1.744^c2	33.12 ± 1.38^c3	36.47 ± 1.99^c2	36.23 ± 1.90^c2
a*
Control	7.49 ± 0.08^a1	6.76 ± 0.29^a2	6.54 ± 0.328^a2	6.26 ± 0.42^a2	4.72 ± 0.38^a3	0.89 ± 0.01^a4
0.1% BHT	7.49 ± 0.08^a1	8.18 ± 0.43^b2	9.28 ± 0.282^b3	7.05 ± 0.26^b1	7.36 ± 0.41^b1	2.86 ± 0.01^b4
0.1% BP	7.49 ± 0.08^a1	7.37 ± 0.23^c1	8.74 ± 0.130^c2	7.25 ± 0.32^b1	5.64 ± 0.15^c3	1.24 ± 0.04^b4
0.3% BP	7.49 ± 0.08^a1	9.16 ± 0.18^d2	8.68 ± 0.340^c3	8.38 ± 0.18^c3	6.75 ± 0.13^d4	2.90 ± 0.01^b5
b*
Control	7.42 ± 0.32^a1	4.86 ± 0.06^a2	7.67 ± 0.362^a1	8.55 ± 0.09^a3	9.95 ± 0.14^a4	6.77 ± 0.16^a5
0.1% BHT	7.42 ± 0.32^a1	6.68 ± 0.01^b2	8.40 ± 0.150^b3	8.39 ± 0.07^a3	8.38 ± 0.06^b3	2.10 ± 0.44^b4
0.1% BP	7.42 ± 0.32^a1	6.36 ± 0.23^b2	8.96 ± 0.526^b3	8.41 ± 0.12^a3	8.76 ± 0.02^b3	2.12 ± 0.33^b4
0.3% BP	7.42 ± 0.32^a1	9.19 ± 0.51^c2	10.19 ± 0.270^c3	7.90 ± 0.18^b1	5.00 ± 0.06^a4	6.90 ± 0.20^a5

All values are expressed as mean ± standard deviation of three replicates.

^a–dMean values in the same column (variants) with different letters are significantly different (p < 0.05).

^1–6Mean values in the same line (storage time) with different numbers are significantly different (p < 0.05).

L*= lightness; a* = redness; b*= yellowness.

Control = beef patty without antioxidants, 0.1% BHT = beef patty with 0.1% of butylated hydroxytoluene, 0.1% BP = beef patty with 0.1% of BP extract, 0.3% BP = beef patty with 0.3% of BP extract.

Figure 2. Effects of BP extract and BHT on metmyoglobin changes in beef patties during 10 days of refrigerated storage at 4 °C.

Control = beef patty without antioxidants, 0.1% BHT = beef patty with 0.1% (w/w) of butylated hydroxytoluene, BP (0.1%) = beef patty with 0.1% (w/w) of BP extract, BP (0.3%) = beef patty with 0.3% (w/w) of BP extract. Each sample was measured in triplicate and the average standard deviation for each sample was less than 5%.

Figure 3. The TBARS values (mg malondialdehyde/kg sample) of beef patties in MAP atmosphere during refrigerated storage for 10 days without light.

Control = beef patty without antioxidants, 0.1% BHT = beef patty with 0.1% (w/w) of butylated hydroxytoluene, 0.1% BP = beef patty with 0.1% (w/w) of BP extract, 0.3% BP = beef patty with 0.3% (w/w) of BP extract. Each sample was measured in triplicate and the average standard deviation for each sample was less than 5%.

Figure 4. Changes in TBARS values (mg malodialdehyde/kg sample) in control and sample containing 0.1% (w/w) BHT and BP extract in MAP atmosphere during 17 days storages at 4 ± 1 °C without light. Each sample was measured in triplicate and the average standard deviation for each sample was less than 5%.