The study was carried out on seven Algerian olive cultivars to report the effect of Spanish style processing on individual and total phenolic compounds and the changes that occur in antioxidant capacity. The results indicate that the treatment leads to losses in phenolic contents which are cultivar dependent.
Table olives (
Several factors are known to affect the qualitative and quantitative phenolic profiles of table olives. These bioactive compounds are closely affected by cultivar (Vinha
Olives cannot be consumed directly after harvest due to their extreme bitterness and they must undergo various processes. Three kinds of table olives are of economic importance in the international market: Spanish style green olives in brine, Greek style naturally black olives in brine, and California black ripe olives. Spanish style green olives or “alkali-treated green olives in brine” are the most widely distributed (El Khaloui and Nouri,
Many studies have been carried out regarding the influence of different processing methods of table olives on the levels of total and single phenolics (Romero
Olive fruits of seven Algerian cultivars:
Olives were debittered in an alkali solution (15 g·L−1) during 8 to12 h until the lye had penetrated two thirds of the pulp. Three washing waters are more than sufficient (twice for 4 h and once for 12 h) to eliminate excess alkali. Then, the olives were fermented in brine (8% NaCl) where a lactic fermentation reduces the pH to 4.5.
Samples of fresh and processed olives were freeze-dried at −58 °C (Christ, Alpha 1–4 LD plus, Osterode am Harz, Germany), ground in electric blender (IKA model A 11 B, Staufen, Germany) and stored at −18 °C until analysis.
Phenolic compounds were extracted according to Mc Donald
The total phenolic content of the extracts was determined with Folin Ciocalteu reagent according to Borzello
The presence and amount of phenolic compounds in the olive extracts were studied by reversed phase HPLC analysis using a binary gradient elution. The analysis was performed by reversed phase HPLC on a LC-10ADVP Shimadzu (Milan, Italy) liquid chromatography equipped with an SPD M10AVP diode array detector (Shimadzu). The chromatographic separation was achieved on a Spherisorb S5 ODS-3 (250 mm×4.6 mm i.d.) reversed-phase column (Phenomenex, Macclesfield, UK). The solvent system used was a gradient of solvent A (water: trifluoroacetic acid, 97:3, v/v), and solvent B (acetonitrile: methanol, 80:20, v/v). A step gradient from 5% to 98% B (45 min) was applied at a flow rate of 1 mL·min−1. Peak quantification was carried out at 279 nm. The main phenolic compounds were identified by comparison with relative retention times of pure compounds, when available, or by comparing the relative elution order and UV spectra with those reported in the literature (Brenes
The Ferric
The procedure reported by Boskou
The hydrogen peroxide radical scavenging activity was determined according to Hemalatha
% scavenged H2O2 = (AC-AT)/AC*100
Where: Ac is the absorbance of the control and AT is the absorbance of the test.
The effect of extracts on the β-carotene- linoleic acid emulsion was determined by applying the method reported by Nsimba
Where: AA% is antioxidant activity, A0 and At; emulsion absorbance at t=0 and after incubation time t (t=105 min), A00 and A0t: absorbance values for negative control at t=0 and after the same incubation time.
All experiments were conducted in triplicate and a statistical analysis was done using Statistica 5.5 with the analysis of variance (ANOVA/MANOVA) to determine the significant differences at a level of confidence of (P<0.05). Correlation coefficients were calculated using the Pearson coefficient.
Phenolic contents (
Total and simple phenolic contents of fresh and processed table olives
Azz Sed | Gordal | Sevilla | Sigoise | Teffahi | Bouchouk | Azz Taz | |
---|---|---|---|---|---|---|---|
|
F: 2406.87±15.1m | 2141.3±8.97k | 1950.50±12.8j | 1923.85±1.02l | 1651.62±9.18h | 346.50±4.86c | 1220.25±14.20g |
P: 124.93±3.92a | 545.06±4.23e | 727.15±7.84f | 1688±2.55i | 475.85±11.65d | 283.43±1.41b | 359.05±1.18c | |
|
|||||||
|
F: 994.26±26.64g | 836.42±40.56f | 563.66±15.43e | 433.03±0.00d | 270.16±81.29c | 0.00±0.00a | 427.03±24.71d |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 184.29±49.27d | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | |
|
F: 375.63±0.23f | 164.62±5.53d | 164.51±11.34d | 167.79±0.00d | 105.45±21.04b,c | 78.75±10.93b,c | 170.43±9.72d |
P: 0.00±0.00a | 233.23±13.68e | 129.15±54.85cd | 124.43±24.02c,d | 79.84±11.19b,c | 56.65±6.21b | 0.00±0.00a | |
|
F: 255±72.15g | 159.39±16.05c | 168.98±5.01e | 445.5±0.00f | 29.79±0.00a | 23.21±0.68a | 135.342±11.37b |
P: 105.97±12.2bc | 45.68±1.49a | 545.42±13.24f | 98.80±19.8b | 14.49±1.49a | 100.60±1.65b | 38.22±0.00a | |
|
F: 141.64d±7.06 | 257.97±31.75e | 172.93±16.54de | 99.00±0.00c | 38.51±0.00a,b,c | 61.35±1.77b,c | 174.81±23.86 |
P: 0.00a±0.00 | 80.23±5.18c | 81.03±7.90c | 71.10±9.58bc | 14.66±2.85ab | 16.72±1.56a,b | 64.52±0.00b,c | |
|
F: 391.08±5.50d | 200.84±12.32c | 393.30±6.63d | 407.54±0.00d | 138.57±0.00b | 0.00±0.00a | 207.03±20.06c |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 131.58±18.34b | 0.00±0.00b | 0.00±0.00a | 0.00±0.00a | |
|
F: 215.57±42.27b,c | 151.44±14.17b,c | 270.12±3.35c | 306.47±0.00d | 106.54±14.57a,b | 0.00±0.00a | 104.40±6.37a,b |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 100.57±25.48a,b | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | |
|
F: 205.29±0.61c | 356.65±26.98e | 188.22±19.59c | 256.77±0.00d | 109.47±16.68b | 0.00±0.00a | 187.73±12.76c |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 120.92±32.78c | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | |
|
F: 53.23±0.55e | 84.08±2.10g | 80.13±1.94fg | 76.60±0.00f | 25.44±0.00b | 22.26±0.16b | 48.72±0.47e |
P: 37.27±0.73c | 43.65±1.09d | 106.49±0.26h | 35.84±8.76c | 24.38±0.00b | 27.60±4.23b | 24.35±0.00b | |
|
F: 334.89±86.71e | 164.39±3.95d | 140.06±3.90cd | 70.31±0.00ab | 86.02±3.91b,c | 65.30±8.64a,b | 114.52±3.79d |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 52.68±16.76a,b | 51.10±0.00a,b | 0.00±0.00a | 0.00±0.00a | |
|
F: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a |
P: 0.00±0.00a | 195.22±14.81f | 154.37±4.11e | 0.00±0.00a | 37.16±2.55b | 51.26±2.35c | 133.94±0.00e | |
|
F: 0.00±0.00a | 476.08±7.01f | 195.75±37.6c | 471.13±0.00f | 0.00±0.00a | 97.98±7.16b | 0.00±0.00a |
P: 312.23±26.32e | 0.00±0.00a | 295.45±34.64de | 258.66±51.56d | 101.69±20.31b | 195.80±3.32c | 0.00±0.00a | |
|
F: 295.68±17.74f | 98.90±2.35c | 159.82±5.79e | 121.96±0.00d | 0.00±0.00a | 0.00±0.00a | 110.84±7.71c,d |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 74.102±21.88b | 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | |
|
F: 133.57±10.95b,c | 221.95±33.78e | 212.91±16.13de | 146.25±0.00b,c | 142.95±35.82b,c | 107.26±1.80b | 136.23±27.20b,c |
P: 35.37±3.6a | 197.86±22.65c,d,e | 141.38±3.27bc | 156.4±59.13b,c,d | 0.00±0.00a | 56.42±3.08a | 0.00±0.00a | |
|
F: 231.51±34.72g | 215.93±8.10fg | 103.54±16.1cd | 149.81±41.63d,e | 137.74±33.06d,e | 0.00±0.00a | 185.90±4.38e,f |
P: 0.00±0.00a | 0.00±0.00a | 0.00±0.00a | 142.72±0.00d,e | 47.09±10.49a,b | 0.00±0.00a | 76.93±0.00b,c |
F: fresh olives; Azz Sed:
The results obtained for fresh olives are similar to those obtained for Portuguese cultivars (Pereira
A drastic decrease in phenolic content was noted after processing. Losses in those compounds differ largely among the cultivars, from 12.25% (
The HPLC analysis of phenolic compounds (
The main phenolic compound detected in fresh olives was oleuropein; its proportion ranged from 25.43% (
Verbascoside was the second most abundant phenolic compound; its values ranged from 391.08 to 407.548 mg·100 g−1 for
Similarly to the evolution of oleuropeine, verbascoside and ligstroside contents showed a decline in processed olives; their contents were under quantification limits in processed olives for the majority of cultivars, excepted for
In processed olives, the first major phenolic compound was hydroxytyrosol. The highest content was recorded for
Caffeic acid, which is derived from the hydrolysis of verbascoside, was not detected in processed olives. Rodriguez
The ferric reducing power of the phenolic extracts of fresh and processed olives are represented in
Antioxidant activities of methanolic extracts of fresh and processed olives
Cultivar | SA DPPH (mg Eq/100g DW) | Reducing Power (mg Eq/100g DW) | SA H2O2 (%) | IBBC (%) | ||||
---|---|---|---|---|---|---|---|---|
Quercetin Eq | Trolox Eq | α-tocopherol Eq | Quercetin Eq | BHA Eq | BHT Eq | |||
|
1972.62±6.71kl | 5458.53±18.57kl | 14365.51±48.86kl | 4531.90±255.67l | 7784.40±439.15l | 9180.82±517.93l | 85.02±0.69g | 72.17±3.39ef |
|
143.00±0.21a | 395.71±0.58a | 1041.40±1.54a | 283.36±0.66a | 486.73±1.13a | 574.85±1.39a | 1.75±0.39a | 34.88±2.03a |
|
1853.34±27.34l | 5128.46±75.64l | 13496.85±199.07l | 3748.66±104.43k | 6439.02±179.39k | 7594.11±211.57k | 88.89±2.22h | 71.69±0.84ef |
|
503.64±2.47d | 1393.65±6.84d | 3667.74±18.01d | 928.44±23.08c | 1594.77±39.65c | 1868.54±47.16c | 2.49±0.39a | 75.14±0.93ef |
|
1453.74±32.30i | 4022.72±89.39i | 10586.83±235.26i | 3063.5±294.56i | 5262.15±505.96i | 6206.11±596.72i | 88.67±9.67i | 73.95±1.27ef |
|
783.90±1.12f | 2169.18±3.09f | 5708.74±8.14f | 1556.35±0.00e | 2673.32±2.625e | 3154.86±0.99e | 24.21±3.51d | 45.48±4.15b |
|
1660.05±44.18k | 4593.61±122.26k | 12089.25±321.77k | 3723.16±100.42j | 6395.23±172.49j | 7542.47±203.43j | 68.09±0.65f | 81.29±1.86f |
|
1693.05±24.60j | 4684.93±68.08j | 12329.58±179.16j | 2316.28±12.27g | 3978.64±21.07g | 4687.18±24.99g | 21.24±0.93d | 75.25±3.47ef |
|
1384.64±9.17h | 3831.49±25.37h | 10083.55±66.78h | 3104.11±1789.52h | 5331.90±81.01h | 6288.38±95.54h | 13.90±3.77c | 78.36±2.88ef |
|
646.79±14.10e | 1789.77±39.03e | 4710.23±102.72e | 997.018485±8.12d | 1712.57±13.94d | 2026.75±16.80d | 12.89±0.26bc | 62.65±2.43d |
|
180.24±2.75a | 498.76±7.60a | 1312.62±20.01a | 522.45±11.34b | 897.40±19.48b | 1058.39±22.98b | 10.68±1.30b | 61.81±0.25d |
|
271.54±3.21b | 751.39±8.87b | 1977.47±23.36b | 576.74±23.8b | 990.66±40.88b | 1155.19±48.66b | 4.33±1.69a | 53.75±11.10c |
|
881.94±16.96g | 2440.45±46.93g | 6422.68±123.51g | 1946.18±45.91f | 3342.93±78.86f | 3942.62±93.01f | 19.79±2.30d | 75.08±1.52ef |
|
453.27±1.99c | 1254.26±5.50c | 3300.92±14.48c | 863.89±10.54c | 1483.90±18.10c | 1747.40±21.40c | 30.45±7.24e | 67.90±3.47de |
F: fresh olives;
P: Processed olives;
Results represent average of three replications.
Different letters in the same line, and between fresh and processed olives for the same cultivar indicate significant difference (p<0,05).
Processing caused a decrease in the reducing capacity of extracts. The values ranged from 283.36 QEq·100 g−1, 486.72 BHAEq·100 g−1, 574.85 mg BHTEq·100 g−1 (
The results showed that a reduction in reducing power is related to a loss in phenolic content. A significante correlation (r=0.98) (
Correlation coefficients for the relationship between antioxidant activities and phenolic content of the extracts
Var | TP | Oleuro | Hydroxy | DPPHQ | DPPH-T | DPPH-αT | RP-Q | RP-BHA | RP-BHT | Querc | Ligst | vebasco | Tyrosol | hydroxy-glu | Ac-hydroxy | B-carot | H2O2 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Var | 1.000 | |||||||||||||||||
TP | −0.429 | 1.000 | ||||||||||||||||
Oleuro | −0.488 | 0.900 |
1.000 | |||||||||||||||
Hydroxy | −0.335 | 0.336 | 0.261 | 1.000 | ||||||||||||||
DPPHQ | −0.533 |
0.955 |
0.858 |
0.414 | 1.000 | |||||||||||||
DPPH-T | −0.490 | 0.967 |
0.830 |
0.357 | 0.939 |
1.000 | ||||||||||||
DPPH- |
−0.490 | 0.967 |
0.830 |
0.357 | 0.939 |
1.000 |
1.000 | |||||||||||
RP-Q | −0.444 | 0.980 |
0.905 |
0.408 | 0.979 |
0.947 |
0.947 |
1.000 | ||||||||||
RP-BHA | −0.444 | 0.980 |
0.905 |
0.408 | 0.979 |
0.947 |
0.947 |
1.000 |
1.000 | |||||||||
RP-BHT | −0.444 | 0.980 |
0.905 |
0.408 | 0.979 |
0.947 |
0.947 |
1.000 |
1.000 |
1.000 | ||||||||
Querc | −0.328 | 0.866 |
0.830 |
0.113 | 0.733 |
0.866 |
0.866 |
0.787 |
0.787 |
0.787 |
1.000 | |||||||
Ligst | −0.427 | 0.786 |
0.911 |
0.099 | 0.750 |
0.694 |
0.694 |
0.786 |
0.786 |
0.786 |
0.689 |
1.000 | ||||||
Verbasco | −0.333 | 0.850 |
0.754 |
0.118 | 0.714 |
0.821 |
0.821 |
0.752 |
0.752 |
0.752 |
0.828 |
0.749 |
1.000 | |||||
Tyrosol | −0.473 | 0.451 | 0.371 | 0.595 |
0.392 | 0.486 | 0.486 | 0.390 | 0.390 | 0.390 | 0.522 | 0.229 | 0.474 | 1.000 | ||||
Hydroxy-Glu | −0.265 | 0.704 |
0.779 |
0.211 | 0.546 |
0.613 |
0.613 |
0.638 |
0.638 |
0.638 |
0.819 |
0.644 |
0.671 |
0.631 |
1.000 | |||
Ac-Hydroxy | 0.051 | −0.422 | −0.470 | 0.085 | −0.358 | −0.434 | −0.434 | −0.378 | −0.378 | −0.378 | −0.508 | −0.459 | −0.494 | 0.104 | −0.153 | 1.000 | ||
B-Carot | 0.096 | 0.678 |
0.510 | −0.105 | 0.574 |
0.587 |
0.587 |
0.637 |
0.637 | 0.636 |
0.560 |
0.434 | 0.563 |
−0.14 | 0.519 | −0.103 | 1.000 | |
H2O2 | −0.459 | 0.824 |
0.875 |
0.413 | 0.829 |
0.774 |
0.774 |
0.838 |
0.838 | 0.838 |
0.703 |
0.722 |
0.658 |
0.460 | 0.732 |
−0.335 | 0.456 | 1.000 |
Significant linear correlation at p<0.05.
TP: Total phenolic.
DPPH-Q (Q: quercetin eq), DPPH-T (T:trolox eq), DPPH-αT (α-tocopherol eq).
RP=reducing power, RP-Q (quercetin eq), RP-BHA (BHA eq); PR-BHT (BHT eq).
The potential anti-oxidant index (PAOXI) values of extracts are given in
PAOXI values of extracts corresponding to reducing power, scavenging activity and inhibition bleaching of β-carotene
RP | SAH2O2 | IBBC | |
---|---|---|---|
|
F: 0.514d | F: 0.286b | F: 0.336g |
P: 0.429a | P: 0.626c | P: 0.035a | |
|
F: 0.560e | F: 0.237a,b | F: 0.299f |
P: 0.597f | P: 2.209f | P: 0.072b | |
|
F: 0.594f | F: 0.208a | F: 0.263e |
P: 0.468b | P: 0.317b | P: 0.161c | |
|
F: 0.584e,f | F: 0.319b | F: 0.267e |
P: 0.805h | P: 0.858d | P: 0.248e | |
|
F: 0.527d | F: 1.053e | F: 0.210d |
P: 0.480b,c | P: 0.369b | P:0.076b | |
|
F: 0.648g | F: 0.323b | F: 0.055a,b |
P: 0.505c,d | P: 0.575c | P: 0.054a,b | |
|
F: 0.632g | F: 0.578c | F: 0.161c |
P: 0.419a | P: 0.106a | P: 0.054b |
F: fresh olives P: Processed olives.
RP: Reducing Power SAH2O2 : Scavenging activity against H2O2 IBBC: Inhibition Bleaching of β-carotene.
Different letters in the same column indicate significant difference (p<0.05).
The scavenging capacity of the extracts (
The effect of processing on scavenging capacity differs among the cultivars; as a consequence of the decline in phenolic content, a reduction was noted for six cultivars with remarkable differences in loss percentages: 92.75% (
According to the Folin Ciocalteu assay,
A graphic representation% DPPH inhibition=f (C (mg·mL−1)) revealed a perfect linearity for all samples (0.993≤r≤0.997) (data not shown) which indicates that the extract scavenging effect on DPPH radical increases with increasing concentrations. The scavenging capacity of fresh olives according to the effective concentrations (EC50) (
The effective concentration (EC50) of extracts exhibited an inverse relationship with phenol contents, showing a significant negative correlation (r=−0.772). Phenolic compounds of olive extracts are good hydrogen donors.
Inhibition percentages of hydrogen peroxide in fresh and processed green olives (
Losses in scavenging activities after processing were estimated to be 97.94, 97.19, 72.69, 68.8 and 59.45%, respectively, for
The antioxidant activity of flavonoids against H2O2 was not significant (r=0.404) (
Potential antioxidant index (PAOXI) values of the extracts (
The percentages of inhibition bleaching of β-carotene (IBBC) for fresh and processed olive extracts at the concentration of 7.14 mg·mL−1 are given in
Losses in antioxidant activity after processing varied according to the cultivar:
The PAOXI values obtained (
To get a complete picture of the ranking of the antioxidant capacities of table olives, a relative antioxidant capacity index (RACI) was calculated by integrating the antioxidant capacity values generated from the different tests. RACI is the mean value of standard scores transformed from the initial data generated with different methods (Sun and Tanumihardjo,
Relative antioxidant capacity index (RACI) of extracts of fresh and processed olives.
In conclusion, the results revealed a significant influence of Spanish style processing on the phenolic compounds and antioxidant capacity of green table olives extracts of seven Algerian cultivars. This effect differs greatly among the cultivars;
The results obtained for the antioxidant activity assessed by the four assays showed that among the studied cultivars, the fresh olives of the
The data from this study show that olive extracts and mainly extracts of fresh olives of
As far as we know, this is the first report considering the antioxidant potential of Algerian green olive cultivars. Further studies are needed to focus on phenolic loss reduction as a result of Spanish style processing of green table olives.
The authors are grateful to the staff of