Food Chemistry 125 (2011) 536–541

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Food Chemistry

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Variation in antioxidant potential and total polyphenol content of freshand fully-fermented Sri Lankan tea

S. Jayasekera a, A.L. Molan b, M. Garg c, P.J. Moughan a,⇑a Riddet Institute, Massey University, Palmerston North, New Zealandb Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealandc Nutraceuticals Research Group, School of Biomedical Sciences and Pharmacy, University of Newcastle, Australia

a r t i c l e i n f o a b s t r a c t

Article history:Received 30 June 2010Received in revised form 25 July 2010Accepted 8 September 2010

Keywords:Antioxidant activityTotal phenolic contentsUnfermented teaFully-fermented Sri Lankan tea

0308-8146/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.foodchem.2010.09.045

⇑ Corresponding author. Tel.: +64 06 350 5560; faxE-mail address: p.j.moughan@massey.ac.nz (P.J. M

Tea polyphenols possess antioxidant properties and have been shown to have a protective effect againstseveral degenerative diseases. The study aimed to determine the amounts of polyphenols and antioxidantproperties for teas grown in Sri Lanka, over a period of 10 months. Water extracts of freeze-dried fresh(unfermented) and fully-fermented tea leaves were made for a structured set of samples (fermentedand unfermented teas from six plantations; teas representing two harvesting seasons from four planta-tions) collected from the main tea growing regions in Sri Lanka. Total phenolic content (TPC), the ferricreducing antioxidant power (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavengingactivity were determined for each sample. The results highlight significant (P < 0.05) variations in antiox-idant activity across the six plantations. FRAP and DPPH for both fermented and unfermented teas fromthe four highland plantations showed a significant (P < 0.05) interaction between season and plantation.A similar interaction between season and plantation was observed for total phenolics in unfermentedteas from the four highland plantations. The variability of the total phenolics for fermented teas, however,was independent of seasonal variations. A significant correlation (r = 0.5, P < 0.05) was observed betweenFRAP and total phenolics.

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1. Introduction

Polyphenols in tea scavenge reactive oxygen species and freeradicals through several proposed mechanisms (Salah et al.,1995), including depolarisation of electrons and formation of intra-molecular hydrogen bonds (Van Acker, Van den Berg, Tromp,Griffioen, & Van Bennekom, 1996). Green tea (unfermented tea)is a major beverage in Asian countries, such as China and Japan,whereas black tea (fermented tea) is more popular in other partsof the World. Although green and black teas are made from theleaves of the same plant, Camellia sinensis, differences in the pro-cessing of the leaves result in differing chemical compositions.Some studies (Leung et al., 2001) have shown that black tea hasequal health benefits to green tea, indicating that the theaflavinspresent in black tea possess similar antioxidant potency to the cat-echins in green tea.

In living organisms, reactive oxygen species are generated bymany pathways and they can cause oxidative damage to importantbiomolecules such as lipoproteins and DNA. Antioxidants andantiradicals have received much attention because their ingestion

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: +64 06 350 5655.oughan).

supposedly helps to prevent in vivo oxidative damage which isassociated with many diseases, including cancer, atherosclerosis,diabetes, arthritis, brain dysfunction, and immune deficiency.Consequently, there has been increasing interest in finding naturalantioxidants from plants to protect the human body from the attackof free radicals and retard the progress of chronic diseases (Haslam,1996; Rice-Evans, Miller, & Paganga, 1996; Weisburger, 1999).

Although there is conflicting evidence, epidemiological studiessuggest that green tea possesses diverse pharmacological proper-ties, which include anti-oxidative (Serafini, Ghiselli, & Ferro-Luzzi,1996), anti-inflammatory (Mutoh et al., 2000), anti-mutagenic(Steele et al., 2000), anti-diabetic (Zeyuan, Bingying, Jinming, &Yifeng, 1998), anti-bacterial (Hara-Kudo et al., 2005), anti-parasitic(Molan, Meagher, Spencer, & Sivakumaran, 2003; Molan, Sivakum-aran, Spencer, & Meagher, 2004), and anti-aging effects (Espositoet al., 2002). Although a number of mechanisms have been pro-posed for the beneficial effects of tea, the radical-scavenging andantioxidant properties of tea polyphenols are frequently cited asimportant contributors (Higdon & Frie, 2003) to these beneficaleffects.

Studies have shown that the quality of tea, especially black tea,is influenced by many factors such as season and altitude (Owuor,Obaga, & Othieno, 1990), genetic make-up of the plant (Magoma,Wachira, Obanda, Imbuga, & Agong, 2000; Owuor & Obanda,

S. Jayasekera et al. / Food Chemistry 125 (2011) 536–541 537

1995), and the region of production and climate (Owuor, Obanda,Nyirenda, & Mandala, 2008). However, there is not a great deal ofinformation on the effects of these factors on the total phenolicconcentrations in tea and subsequent antioxidant activity. There-fore, we investigated the total phenolic content (TPC) as well asthe FRAP and DPPH radical-scavenging activity of water extractsfrom fresh and fermented tea leaves grown in different regions ofSri Lanka. The regions selected included four highland plantationsand two lower altitude plantations. For high-grown teas, sampleswere also collected from the two harvesting seasons (dry and mon-soon). The relationship between the total phenolic contents of teainfusions and antioxidant potential was also investigated. A preli-minary study was undertaken to determine the effect of brewingtemperature and stirring during brewing on TPC and the measuresof antioxidant activity. The overall objective was to ascertain thevariability in the total phenolic content and antioxidant activityin fermented Sri Lankan teas and their corresponding startingmaterial (unfermented fresh tea leaves) and to investigate the ef-fect of season and plantation.

2. Materials and methods

2.1. Samples

Freeze-dried fresh leaf (unfermented) samples and their corre-sponding black tea (fermented) samples were collected from sixtea plantations in Sri Lanka over the years April 2005 and January2006. The plantations were selected to represent the key tea pro-ducing regions in Sri Lanka. From the plantations situated in higherelevations (four of the six plantations where definite seasons oc-cur), samples were collected during the dry (April, September)and monsoon (January, June) seasons to study the effect of season.Fresh leaf samples were collected when the leaves were broughtinto the tea factory of each plantation and corresponding blacktea leaf samples were collected 18–24 h later when the fresh leafbatches were processed into black tea. Seasonal sampling wasnot performed for teas grown in the low and mid altitudes wherethe climatic conditions remain relatively constant throughout theyear. The names and locations of the plantations and the monthswhen the samples were collected are listed in Table 1. In total therewere ten samples (four samples collected during the dry seasonfrom four highland plantations, four samples collected during themonsoon season from four highland plantations, and one sampleeach from the two low-altitude plantations) each of fermentedand unfermented tea. The teas were of different cultivars, grownin different soils, and had been subjected to different horticulturalmanagement practices. The ratio of vegetatively propagated toseedling plants was 70:30 across the plantations.

Fresh tea leaves were collected directly from the tea factorieswithin 1–2 h of plucking. Fifty approximately equally sized sam-

Table 1Names, locations and sampling periods for the Sri Lankan teas.

Plantation Description of the location

Pedro estate Located in Nuwara Eliya, western slopes of the central hills, about 2in the central hill region

Laxapana estate Located on the western slopes of the central hills, about 1200–150

Greatwesternestate

Located in the western slopes of the central hills, about 1200–180

Sarnia Estate Located in the eastern slopes of the central hills, about 1200–1300

Kataboolaestate

Located in the middle slopes about 600–900 m above sea levels. Thpatterns for mid grown teas

Rilhena estate Located at an elevation of about 600 m above sea level. There are nfor low grown teas

ples were drawn at random, immediately after the leaves werebrought into the factory. A 200 g composite sample from these ran-dom samples was stored in sealed bags at 4 �C to prevent physicaldamage during immediate transportation to the Tea ResearchInstitute in Sri Lanka where they were freeze-dried. Travel timevaried from between 2–5 h. Freeze-dried tea samples were broughtto New Zealand in sealed, airtight, foil bags for chemical analysis.Processed black tea (fully-fermented) samples were collected fromthe factories on completion of processing the following day. Blacktea samples were selected from the same batch of leaves fromwhich the fresh leaf samples were collected and in the manner de-scribed for the fresh leaf samples. Samples were finely ground be-fore chemical analysis.

2.2. Chemicals

2,4,6-Tripyridyl-s-triazine (TPTZ), sodium acetate, ferric chlo-ride and gallic acid, Folin–Ciocalteu’s phenol reagent and ferroussulphate were purchased from Sigma (Palmerston North, NewZealand).

2.3. Preliminary study

A preliminary study was undertaken to evaluate the effects ofbrewing temperature and stirring on the recovery of TPC and onantioxidant activity. Freeze-dried fresh leaf (unfermented) samplesand their corresponding black tea (fermented) samples were sub-jected to brewing at either 70 �C or 100 �C, with or without stirringand TPC, FRAP and DPPH were each determined in triplicate. Thetrial was duplicated over time.

2.4. Estimation of the total phenolic content by the Folin–Ciocalteuassay

The amount of total phenolic content (TPC) in aqueous tea ex-tracts (100 �C, with stirring) was determined according to the Fo-lin–Ciocalteu procedure as described by Molan, Flanagan, Wei,and Moughan (2009b). Briefly, an aliquot of 12.5 ll of water-solu-ble tea extract was mixed with 250 ll of 2% sodium carbonatesolution in 96-well microplates and allowed to react for 5 min atroom temperature. Then 12.5 ll of Folin–Ciocalteu phenol reagent(50%) was added and allowed to stand for 30 min at room temper-ature before the absorbance of the reaction mixture was read at650 nm using a plate reader. Calibration was achieved with anaqueous gallic acid solution (100–1000 lg/ml). Total phenol valueswere expressed as gallic acid equivalents (GAE) based on the cali-bration curve. The assay was carried out in triplicate for duplicateextractions giving six observations for each sample. Values givenfor each sample are means of six observations.

Sampling period

000 m above sea level on the western slopes April (dry) and June (monsoon)2005

0 m above sea level April (dry) and June (monsoon)2005

0 m above sea level April (dry) and June (monsoon)2005

m above sea level September 2005 (dry) andJanuary 2006 (monsoon)

ere are no seasonal variations in harvesting April and June 2005

o seasonal variations in harvesting patterns September 2005 and January2006

538 S. Jayasekera et al. / Food Chemistry 125 (2011) 536–541

2.5. Evaluation of antioxidant activity using FRAP assay

The antioxidant activity (AOA) of water-soluble tea extracts(100 �C, with stirring) was determined using the ferric reducingability of plasma (FRAP) assay of Benzie and Strain (1996). Theworking FRAP reagent was prepared by mixing 10 volumes of300 mmol/l acetate buffer, pH 3.6, with 1 volume of 10 mmol/lTPTZ (2,4,6-tripyridyl-s-triazine) in 40 mmol/l hydrochloric acidand with 1 volume of 20 mmol/l ferric chloride. Freshly preparedFRAP reagent (250 ll) was warmed to 37 �C for 10 min, and then8.5 ll extract and 25 ll deionized water was added to the FRAP re-agent. Sample absorbance was then read at 595 nm after 30 min ina plate reader.

A standard curve was prepared using different concentrations(1–12 mmol/l) of FeSO4�7H2O. The results were corrected for dilu-tion and expressed in mmol FeSO4/l. All solutions were used on theday of preparation. All determinations were performed in triplicatefor duplicate extractions, giving six observations for each sample.Values for each sample are means of six observations.

2.6. Determination of DPPH radical-scavenging capacity

The DPPH assay has been widely used to test the ability ofcompounds to act as free radical scavengers or hydrogen donorsand to evaluate the antioxidant activity of foods and plant ex-tracts (Satoh, Tohyama, & Nishimura, 2005; Yildirim, Mavi, &Kara, 2001; Zhu, Hackman, Ensunsa, Holt, & Keen, 2002). The as-say detects scavenging of free radicals by samples through thescavenging activity of the stable 2,2-diphenyl-1-picrylhydrazyl(DPPH) free radical. The reduced DPPH formazan form wasdetermined using a spectrophotometer. Briefly, 25 ll of aqueoustea extract (100 �C, with stirring) or 0.1–1.0 mM ascorbic acid in0.1% ethanol (as a positive control as well as a blank for back-ground subtraction) were allowed to react with 250 ll of0.2 mM DPPH in 95% ethanol in a 96-well microplate. The platewas then incubated at room temperature for 30 min after whichthe absorbance was measured at 550 nm using a microplatereader. Scavenging capacity of the sample was compared to thatof ascorbic acid as a positive control.

The antiradical activity was calculated as a percentage of DPPHdecolouration using the following equation:

Antiradical activity¼ ðabsorbance of control incubation� absorbance of the tested sample=absorbance of controlincubationÞ � 100:

Table 2Effect of brewing temperature and stirring during extraction on (A) Ferric reducing antioactivity (DPPH;%) and (C) total phenolic content (TPC; mg gallic acid equivalent (GAE)/g d

Temperature (T)/stirring (S)

(A)FRAP 70 �C (unstirred) 70 �C (stirred) 100 �C (unstirred)Unfermented 9.2 9.9 10.1Fermented 8.0 8.8 9.0

(B)DPPH 70 �C (unstirred) 70 �C (stirred) 100 �C (unstirred)Unfermented 28.5 31.9 37.8Fermented 28.5 36.3 41.9

(C)TPC 70 �C (unstirred) 70 �C (stirred) 100 �C (unstirred)Unfermented 148.5 159.8 154.7Fermented 86.5 124.2 115.2

a Values are the means of triplicate incubations for two separate runs (n = 6).

All determinations were performed in triplicate for duplicateextractions, giving six observations for each sample. Values foreach sample are means of six observations.

2.7. Statistical analysis

Statistical analyses were conducted using SAS (2008 version).Quantitative data for FRAP, DPPH and TPC were compared usingANOVA. A two-way ANOVA including the effects of plantation, sea-son and plantation � season was performed on a subset of 16 sam-ples (high-grown teas only).

3. Results and discussion

3.1. Preliminary study, effect of brewing temperature and stirring onTPC, FRAP and DPPH

The effects of both extraction temperature and stirring duringextraction on FRAP values, DPPH-scavenging activity and TPC ofaqueous extracts from unfermented and fermented tea leaves areshown in Table 2. The FRAP values, and the TPC values increased(P < 0.05) with increasing brewing temperature from 70 �C to100 �C and with stirring at both temperatures (P < 0.05) for bothunfermented and fermented leaves. For DPPH, values increased(P < 0.05) with increasing brewing temperature and stirring forunfermented leaves, but there was a significant (P < 0.05) interac-tion effect for unfermented leaves (Table 2). At both temperaturesand with and without stirring, extracts from unfermented leavesshowed significantly higher (P < 0.05–0.0001) FRAP and TPC valuesthan fermented leaves. The results are consistent with those of Chen,Shi, and Chen (1996) and Khokhar and Magnusdottir (2002), who re-ported that the level of total phenols in different teas increased withextraction temperature. Molan, De, and Meagher (2009a) studiedthe effect of extraction temperature and stirring during extractionon the FRAP and TPC values of green tea and also found that these val-ues increased with increasing temperature and stirring. Based on theresults of the preliminary study, all extractions in the main studywere undertaken at 100 �C with stirring.

3.2. Main study

Coefficients of Variation (%; between 6 replicate determina-tions) ranged from 1% to 5% for FRAP, 3% to 15% for DPPH and0.2% to 1.2% for TPC (Table 3). Overall mean CV’s (%) were 2.4,7.8 and 0.64 for FRAP, DPPH and TPC, respectively and particularlyfor the FRAP and TPC assay, the CV’s indicate a generally high de-gree of precision for the respective chemical analyses.

xidant power (FRAP; mmol/l), (B) 2,2-diphenyl-1-picrylhydrazyl radical-scavengingry leaves) for unfermented and fermented tea samplesa.

SEM Significance

100 �C (stirred) T S T � S10.6 0.073 P < 0.0001 P < 0.0001 NS

9.9 0.142 P < 0.0001 P < 0.0001 NS

100 �C (stirred) T S T � S43.8 0.9 P < 0.0001 P = 0.0003 NS42.9 0.952 P < 0.0001 P = 0.0015 P = 0.0129

100 �C (stirred) T S T � S173.5 1.48 P < 0.0001 P < 0.0001 NS162.9 3.32 P < 0.0001 P < 0.0001 NS

Table 3Coefficients of variation (CV,%) for Ferric Reducing Antioxidant Power (FRAP), DPPHfree radical-scavenging activity (DPPH) and Total Polyphenol Content (TPC) for sets ofsix observations for each sample.

Plantation/Season Samplenumber

Coefficient ofVariation (CV%)

FRAP DPPH TPC

Pedro dry season unfermented 1 3 5 0.8Pedro monsoon season unfermented 2 1.8 7 1Laxapana dry season unfermented 3 1.3 6 0.4Laxapana monsoon season

unfermented4 2.1 6 0.2

Greatwestern dry seasonunfermented

5 4 8 0.6

Greatwestern monsoon seasonunfermented

6 2 10 0.4

Sarnia dry season unfermented 7 2.9 6 0.4Sarnia monsoon season unfermented 8 4 15 1.2Kataboola unfermented 9 5 3 1Rilhena unfermented 10 0.2 12 0.6Pedro dry season fermented 11 2.5 5 1Pedro monsoon season fermented 12 3 7 1Laxapana dry season fermented 13 2.2 6 0.8Laxapana monsoon season fermented 14 2.5 7 0.6Greatwestern dry season fermented 15 1.2 8 0.8Greatwestern monsoon season

fermented16 1.6 14 0.2

Sarnia dry season fermented 17 2.6 14 0.4Sarnia monsoon season fermented 18 3 8 1.2Kataboola fermented 19 3 3 0.4Rilhena fermented 20 1 6 0.2Overall mean CV% 2.4 7.8 0.64

Fig. 1. (A) Ferric reducing antioxidant power (FRAP; mmol/l), (B) 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity (DPPH;%) and (C) total phenolic content(TPC; mg gallic acid equivalent (GAE)/g dry leaves) for unfermented and fermentedtea samples collected from the plantations listed in Table 2. Means (±SE) oftriplicate measurements for two separate runs (n = 6).

S. Jayasekera et al. / Food Chemistry 125 (2011) 536–541 539

The mean values for TPC, FRAP and DPPH in each of the samplesare shown in Fig. 1 and point to potential for selecting teas of eitherhigh or low TPC and antioxidant activity. The concentration of totalpolyphenols ranged from a low of 121 to a high of 198 mgGAE/gdry leaves, meaning that there was a 63% difference between thehighest and lowest TPC values. FRAP values ranged from 8273 to11519 lmol/l and this corresponds to a 39% difference betweenthe highest and lowest values. DPPH values were more variablethan FRAP values, ranging from 31.4% to 53.1% inhibition. For DPPHthere was a 69.1% difference between the highest and lowestvalues.

3.3. Influence of plantation and season on FRAP, DPPH and TPC

For FRAP there was a statistically significant interaction be-tween plantation and season for both the fermented (P < 0.0001)and unfermented teas (P < 0.001) (Table 4) indicating that differ-ences between plantations were not consistent for season. Thehighest and the lowest FRAP values for high-grown unfermentedteas were observed for teas from Sarnia and Pedro plantationsrespectively. In contrast, the highest and lowest FRAP values forthe corresponding fermented tea, were observed for Pedro and Sar-nia plantations respectively.

Similarly, for DPPH there was a significant (P < 0.05) interactioneffect between season and plantation (Table 4) for both the fer-mented and unfermented teas. The highest and the lowest DPPHvalues for both fermented and unfermented teas were observedfor Pedro and Greatwestern plantations respectively.

For TPC, there was a significant interaction between plantationand season for the unfermented (P < 0.001) but not for the fer-mented tea (Table 4). There was an independent effect of bothplantation and season on the total phenolic content for fermentedtea. The highest and the lowest TPC values for high-grown unfer-mented teas were observed for Sarnia and Pedro teas respectively.The highest and lowest TPC values for the corresponding fer-mented tea were observed for Pedro and Sarnia plantations respec-

tively. The dry season fermented teas had higher TPC than themonsoon teas. It has been found that the levels of phenolic com-pounds in the leaves of plants are influenced by many environmen-tal factors, such as climate, season, and soil fertility (Roberts,Beuselinck, Ellersieck, Davis, & McGraw, 1993). Moreover, Lees,Hinks, and Suttil (1994) reported that big trefoil clones grown un-der high temperature (30 �C) had substantially greater levels oftannins than the same clones grown under cooler temperature(20 �C).

Interestingly, Sarnia teas had the highest TPC and FRAP valuesin the unfermented state but the lowest TPC and FRAP values whenfermented.

3.4. Effect of fermentation on FRAP, DPPH and TPC

Previous studies (Atoui, Mansouri, Boskou, & Kefalas, 2005; Lee,Kim, Lee, & Lee, 2003) have shown that green tea contains more to-tal phenolics than black tea. In the presently reported study, allteas showed a small numerical increase in determined TPC whenfermented into black tea (Table 5) but with the increases beingstatistically significant (P < 0.05) for only four of the eight teas(Table 5).

In the current study, monsoon season teas showed a general de-crease in FRAP during fermentation (Table 5). Previous studies(Langley-Evans, 2000; Satoh et al., 2005) have also shown that fer-mented tea possessed significantly lower reducing power thanunfermented tea. One of the dry season teas (Pedro) showed a

Table 4Effect of plantation, season and plantation x season on mean (n = 6) FRAP (mmol/l), DPPH (%inhibition) and TPC(mg GAE/g dry leaves) values for unfermented and fermentedteasa.

Plantation Season SEM Significance

Pedro Laxapana Greatwestern Sarnia Dry Monsoon Plantation Season Interaction

UnfermentedFRAP 10.2 11.04 10.8 11.2 10.8 10.7 0.096 <0.001 NS <0.001DPPH 46.3 43.3 38.4 41.4 42.3 42.3 1.03 <0.05 NS <0.001TPC 170.72 173.66 169.92 179.48 172.8 174.16 2.24 <0.0001 0.008 <0.001

FermentedFRAP 10.4 10.8 9.9 9.7 10.9 9.5 0.125 <0.001 <0.0001 <0.0001DPPH 44.8 41.1 33.5 44.6 44.1 44.1 1 <0.001 0.004 <0.05TPC 171.9a 169.2b 157.5c 153.6bc 169.6a 156.5b 2.01 <0.0001 <0.0001 NS

Means sharing the same letter in a row within plantation and season effects were not significantly different at P < 0.05.a Means (±SE) of triplicate measurements for two separate runs (n = 6).

Table 5Effect of fermentation on FRAP, DPPH and TPC for a range of Sri Lankan teas grown in different seasonsa.

FRAP (mmol/l) DPPH (% inhibition TPC (mg GAE/g dry leaves)

Unferm.tea

Fermen.tea

SE Significance/Pvalue

Unfermen.tea

Fermen.tea

SE Significance Unferm.tea

Fermen.tea

SE Significance

Pedro/dry season 10.6 11.2 0.13 <0.01 53.1 39.6 1.6 <0.001 168.2 169.4 3.6 NSLaxapana/dry season 10.9 11.1 0.07 NS 41.7 44.9 2.1 NS 177.4 177.6 1.88 NSGreatwestern/dry

season10.4 10.6 0.11 NS 35.9 35.5 1.9 NS 168 170.6 4.2 NS

Sarnia/dry season 11.5 10.6 0.16 <0.001 39 38.5 2 NS 161 173.6 2.3 <0.001Pedro/monsoon season 9.8 9.7 0.07 NS 50.5 39.1 1.6 <0.001 171.7 172.1 2.74 NSLaxapana/monsoon

season11.2 10.5 0.13 <0.001 43.9 38.2 2 NS 160.9 169.9 1.72 <0.05

Greatwestern/monsoonseason

11.1 9.2 0.29 <0.0001 31.4 40.9 2 NS 147.1 169.3 3.52 <0.0001

Sarnia/monsoon season 10.8 8.7 0.36 <0.001 50.6 43.7 2.2 <0.05 146.3 152.0 9.22 <0.05

a Means (±SE) of triplicate incubations for two separate runs (n = 6).

Table 6Correlation coefficients (r), for the association between FRAP (lmol/l) and DPPH(% inhibition) with TPC (mg GAE/g dry leaves) for aqueous extracts from fermentedand unfermented tea.

Relationship r Significance

FRAP * TPC 0.5 <0.0001DPPH * TPC 0.1 NSFRAP * DPPH 0.2 NS

540 S. Jayasekera et al. / Food Chemistry 125 (2011) 536–541

significant increase in FRAP with fermentation, with another tea(Sarnia) showing a decrease.

Interestingly, three out of four of the monsoon season teasshowed a significant increase in TPC yet a significant decrease inFRAP during processing. This may be due to the formation of di-mers and polymers with lower antioxidant power during fermen-tation of the monsoon season teas. The increase in TPC andconcomitant decrease in FRAP during processing of monsoon sea-son teas deserve detailed attention.

DPPH values for most of the teas were not significantly(P > 0.05) affected during processing (Table 5). Pedro teas fromboth dry and monsoon season and Sarnia tea from the monsoonseason showed a statistically significant decrease in DPPH due tofermentation (Table 5).

3.5. Correlation between total phenolics and antioxidant properties

Correlation analyses between TPC and FRAP and DPPH, respec-tively (including all data for each measure) were undertaken (Table6). There was an overall positive relationship between FRAP andTPC, but not between DPPH and TPC, or between DPPH and FRAP.

When correlations were calculated within subsets of the total datasets, there was a statistically significant (P < 0.05) correlation be-tween FRAP, DPPH and TPC for fermented tea, and for unfermenteddry season tea but not for unfermented monsoon season tea.

It may be that the total phenolic content influences the reduc-tion of ferric ions but not the effect of the radical-scavenging activ-ity of tea. Previous studies (Benzie & Strain, 1996; Benzie & Szeto,1999; Molan et al., 2009b; Satoh et al., 2005; Von Gadow, Joubert,& Hansmann, 1997; Wiseman, Balentine, & Frei, 1997; Xie, Shi,Chen, & Ho, 1993; Zhu et al., 2002) have also shown that there isa strong correlation between reducing power (FRAP values) and to-tal phenolic content of green, oolong and black teas. These resultsindicate that polyphenols are a major contributor to the antioxi-dant capacity of at least fermented teas.

4. Conclusions

The study demonstrates considerable variation among both fer-mented and unfermented Sri Lankan tea samples for TPC and anti-oxidant properties as determined by FRAP and DPPH and showsthat there is considerable potential for using selected combinationsof plantations and season to select high antioxidant teas. There wasalso evidence for an interaction effect for TPC, FRAP and DPPHamong season and plantation, such that differences seen amongplantations differed with season. Various reasons may be behindthese differences such as climate, season, and soil fertility. In termsof selecting high antioxidant teas, attention needs to be paid toboth plantation and season.

Fermentation during the monsoon season produced a statisti-cally significant increase in TPC but a decrease in FRAP for threeof the four monsoon season teas. This relationship between FRAP

S. Jayasekera et al. / Food Chemistry 125 (2011) 536–541 541

and TPC was largely limited to the monsoon season teas. Furtherstudies to determine the catechin and theaflavin profiles and toelucidate the role of the respective polyphenols in the antioxidantactivity are now underway.

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