Food Chemistry 151 (2014) 547–553

Contents lists available at ScienceDirect

Food Chemistry journal homepage: www.elsevier.com/locate/foodchem

Phenolic acid composition, antioxidant activity and phenolic content of tarhana supplemented with oat flour A. Kilci, D. Gocmen ⇑ Uludag University, Faculty of Agric., Dep. of Food Eng., 16059 Gorukle, Bursa, Turkey

a r t i c l e

i n f o

Article history: Received 11 September 2013 Received in revised form 30 October 2013 Accepted 6 November 2013 Available online 26 November 2013 Keywords: Oat Tarhana Antioxidant activity Phenolics

a b s t r a c t In this study, oat flour (OF) was used to replace wheat flour in tarhana formulation at the levels of 10, 20, 30 and 40% (w/w). Control sample did not contain OF. The results showed that addition of OF caused increases in levels of phenolic acids within tarhana samples. The most abundant phenolic acids were vanillic and ferulic acids, and they were followed by gallic acid. Tarhana samples with OF also showed higher antioxidant activities than control sample did. Compared with the control sample, the total phenolic content level increased with the increase in the amount of OF. The results of sensory analysis showed that OF addition neither caused any undesirable taste nor an odor and panelists emphasised a sweet taste as the OF amounts were increased. Therefore, tarhana supplemented with OF can be claimed to be a good source of minerals, phenolics and antioxidants as compared to tarhana without OF. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Tarhana is a traditional Turkish fermented cereal food made from cereal flours, yogurt and various vegetables. It is a good source of B vitamins, minerals, organic acids and free amino acids. Thanks to its rich content, it is known to be a healthy food for children, adults, and for patients (Daglioglu, 2000). After all ingredients are mixed and homogenised and dough is obtained, it is fermented at 30–35 °C for 1–5 days (Gocmen, Gurbuz, Roussef, Smoot, & Dagdelen, 2004; Temiz & Pirkul, 1991), then it is dried and ground by a mill (Tarakci, Dogan, & Koca, 2004). An important part of tarhana consumed in Turkey is homemade and therefore it is sun-dried. From a commercial point of view, tarhana is produced by using modern drying techniques on industrial scale (Tarakci et al., 2004). Tarhana is mainly consumed as soup in Turkey. Tarhana powder is first mixed with cold water (1:5) and then allowed to dissolve for about half an hour, and finally cooked for 20 min with occasional stirring. As soon as it is boiled, some butter is added to the soup and it is consumed at 70 °C. Cheese and roasted bread pieces can also be added upon request (Ozdemir, Gocmen, & Kumral, 2007). Regional diversity of the amount and the type of ingredients, as well as the processing techniques in Turkey, affects chemical composition, nutritional content and sensory attributes of tarhana (Degirmencioglu, Gocmen, Dagdelen, & Dagdelen, 2005; Tarakci et al., 2004). Basically, 4 different types of tarhana have been defined by the Turkish Standardization Institute: (a) flour tarhana, ⇑ Corresponding author. Tel.: +90 224 294 14 95; fax: +90 224 294 14 02. E-mail addresses: [email protected], [email protected] (D. Gocmen). 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.11.038

(b) goce tarhana, (c) semolina tarhana, and (d) mixed tarhana. Using wheat flour, cracked wheat and semolina separately or as combinations in the recipe causes some differences (Daglioglu, 2000). Cereal and legume flours other than wheat flour can also be used in the production of tarhana (Ozdemir et al., 2007). One of them is oat flour which is known as rich in bioactive compounds, dietary fiber and b-glucan. The use of oats in human nutrition has been increasing owing to the fact that they contain beneficial nutritional properties (Webster, 2002). Oats are also useful for the control of diabetes, lipid profile (Butt, Tahir-Nadeem, Khan, & Shabir, 2008), total and low density lipoprotein (LDL) cholesterol levels (Kestin, Moss, Clifton, & Nestel, 1990). In recent years, the interest in oat-based foods for human consumption has increased dramatically because oats are rich in b-glucan and phenolic (Gray et al., 2000; Liu, Zubik, Collins, Marko, & Meydari, 2004; Malkki, Myllymaki, Teinila, & Koponen, 2004; McMullen, 2000; Peterson, Emmons, & Hinns, 2001). The most important bioactive compounds of oats are phenolic compounds. Some oat phenolics have great potential as nutraceuticals while some others are powerful antioxidants. Before the development of the commercial potential of synthetic antioxidants, oat flour was used as antioxidant to extend the shelf life of milk powder, butter, ice cream and some cereal products for many years (Webster, 2002). The antioxidant potential of oats has been recognised for many years. The US FDA Authorization of the Heart Health’s remarks connected with the consumption of oats is especially significant. In the early 1960s, the first researchers who investigate oat antioxidants drew attention to their potential as a sanitary material (Webster, 2002). In addition to its nutritional

548

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

and antioxidant properties, phenolic compounds also influence multiple sensorial food properties, such as flavour, astringency, and colour. Phenolic compounds contribute to aroma and taste of numerous food products of plant origin (Rodriguez et al., 2009). In this study, tarhana was supplemented with oat flour so as to improve its functional and nutritional qualities. The aim of this research was to determine the effects of oat flour addition on the phenolic acid composition, antioxidant activity, phenolic and mineral contents of tarhana. 2. Materials and methods 2.1. Materials Wheat flour (Triticum aestivum) (Type 650), containing 13.3% protein (db), 0.64% ash (db) and 13.4% moisture, was used and supplied from the Toru Flour Milling Co., Ltd. (Bandirma/Turkey). Salt (NaCl), yoghurt, dried onion, tomato and paprika pastes were purchased from the local markets in Bursa, Turkey. Stabilised oat meal (inactivated fat hydrolysing enzymes) was purchased from Eti Food Co., Ltd. (Bozuyuk, Bilecik, Turkey). Oat meal was ground by using a hammer mill (Falling Number-3100 Laboratory Mill, Perten Instruments AB, Huddinge, Sweden) and sieved through 212 lm sieve. It was kept in refrigerator until analysed. 2.2. Production of tarhana To prepare tarhana samples, flour 100%, yogurt 50%, dried onion 2.5%, tomato paste 2.5%, paprika paste 7.5% and salt (NaCl) 7.5% were used (w/w, flour base). Oat flour (OF) were used to replace wheat flour at the levels of 10, 20, 30 and 40% (w/w) whereas control sample did not contain OF. The ingredients were mixed in a mixer (Electrolux Ditomix 5, GA, USA) for 5 min and the resulting dough samples were fermented at 30 °C in a fermentation cabinet _ (Efe Co., Ltd., Izmir/Turkey) for 3 days. The fermented dough samples were dried at 50 ± 2 °C in an air-convection oven (Efe Co., Ltd., _ Izmir/Turkey) to 9–10% moisture content. After drying process, tarhana samples were ground into a rough powder by a hammer mill equipped with a 1-mm opening screen. The resulting powders were stored in a glass jar (0.5 L) and kept in a refrigerator until analysed.

(1 mg L1) was added and then the digested samples were diluted to 25 mL prior to analysis by ICP-OES. The mineral content of the tarhana samples (K, Ca, P, Mg, Fe, Cu, Zn and Mn) were measured using the microwave (Millestone MLS 1200, Italy) nitric acid digestion procedure according to the method described by Sahan, Basoglu, and Gucer (2007) and it was followed by induction coupled plasma optical emission spectrometry (Perkin Elmer 2100 ICP-OES). The emission intensities were obtained for the most sensitive lines free of spectral interference. The analyses were performed at the following flow rates: (a) plasma gas of 15 L min1, (b) auxiliary gas of 1 L min1, and (c) sample of 0.8 mL min1. The mineral eluates were monitored at different wavelengths: 317.9 nm-Ca, 214.9 nm-P, 285.2 nm-Mg, 766.5 nm-K, 206.2 nm-Zn, 238.2 nm-Fe, 327.4 nm-Cu and 257.6 nm-Mn. All chemical analysis were carried out in duplicate on each sample. 2.4. Extraction of free phenolic compounds Free phenolic compounds were extracted according to Vitali, Vedrina Dragojevic, and Sebecic (2009) with slight modifications. Samples (10.0 g dry weight-dw) were defatted twice with 20 mL of hexane at 30 °C by an ultrasonic homogeniser (Scientz-IID, Ningbo Scientz Biotechnology Co., Ltd., Zhejiang, China). The defatted samples (2.0 g dry weight-dw) were mixed with 20 mL of HClconc/methanol/water (1:80:10, v/v) mixture and shaken with a laboratory rotary shaker (JB50-D; Shanghai Shengke Instruments, Shanghai, China) at 250 rpm for 2 h at 20 °C, and then the mixtures were centrifuged at 3500 rpm for 10 min at 4 °C in a centrifuge (Eppendorf 5417R, Germany). The supernatants (free/extractable phenolic compounds) obtained after centrifugation were stored at 20 °C until used. 2.5. Extraction of bound phenolic compounds Bound phenolic compounds were extracted according to Vitali et al. (2009) with slight modifications. After free phenolic extraction, the residues were combined with 20 mL of methanol/H2SO4conc (10:1) mixtures. The mixtures were placed in a water bath at 85 °C for 20 h, and then cooled at room temperature. They were centrifuged at 3500 rpm for 10 min at 4 °C in a centrifuge (Eppendorf 5417R, Germany). The supernatants (bound/hydrolyzable phenolic compounds) were strored at 20 °C until used.

2.3. Determination of minerals 2.6. Determination of phenolic content All solutions were prepared with analytical reagent grade chemicals and ultra-pure water (18 MX cm resistivity) generated by purifying distiled water with the TKA Ultra Pacific and Genpura water purification system (Germany). Suprapur HNO3 (67% v/v) was purchased from Merck (Darmstadt, Germany). Standard stock solutions containing 1000 mg L1 of each element (K, Ca, P, Mg, Fe, Cu, Zn and Mn) were purchased from Merck (Darmstadt, Germany) and used to prepare calibration standards. Working standards were prepared in 0.3% (v/v) HNO3 on a daily basis and used without further purification. 1000 mg L1 standard stock solutions (Merck, Darmstadt, Germany) were prepared in %0.3 HNO3 for internal standard solution. Argon (99.9995% pure, Linde, Turkey) was used as carrier gas. Sample digestion was carried out using the Millestone MLS 1200 (Italy) microwave digestion system. The samples were homogenised and then approximately 0.5 g of them was weighed directly on PTFE flasks after adding 6 mL of HNO3 and subjected to following digestion program: 250 W (2 min), 0 W (2 min), 250 W (6 min), 400 W (5 min) and 600 W (5 min). After cooling at room temperature, sample solutions were transferred into 50 mL polyethylene flasks. 100 lL of internal standard solution

Phenolic contents (free, bound and total phenolics) were determined based on the Folin–Ciocalteu colorimetric method as described by Xu et al. (2009) with slight modifications. To summarise briefly, an aliquot (0.5 mL) of appropriately diluted extracts, 2.5 mL of deionised water and 0.5 mL of 1.0 M Folin–Ciocalteu reagent were mixed within 10 mL volumetric flasks and vortexed for 10 min at room temperature. After 30 min, 1.5 mL of 7.5% sodiumcarbonate solution was added and mixed thoroughly. The absorbance of the reaction mixtures was measured using a spectrophotometer (UV-Mecasys, Optizen 3220) at 750 nm wavelength after incubation for 30 min at room temperature. Methanol was used as the blank, and gallic acid (GA) was used for calibration of the standard curve (0–500 mg/L). Phenolic content was expressed as gallic acid equivalents (milligrams of GAE per gram DW). 2.7. Determination of phenolic acids Phenolic acids were analysed according to validated methods with slight modifications in HPLC elution conditions (Mattila, Pihlava, & Hellström, 2005; Verardo, Serea, Segal, & Caboni, 2011;

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

549

Xu et al., 2009). All solvents were HPLC-grade and filtered through a 0.45 mm filter disk. The total phenolic extracts (free and bound) were also filtered through a membrane filter (0.45 lm) (Filtrex Technology, Singapore) prior to HPLC analysis. They were analysed in a HPLC chromatograph system (Perkin Elmer, Flexar, USA) equipped with Diode Array Detector (DAD) and a reversed-phase C18 column (Perkin Elmer ODS-2, 5 lm, 250 mm 4.6 mm). The temperature of the column oven was set at 30 °C. The wavelengths used for the quantification of phenolic acids with the diode array detector were: 254 nm for p-hydroxybenzoic acid and vanillic acid; 270 nm for gallic acid; 280 nm for syringic acid, p-coumaric acid; and 329 nm for caffeic acid, ferulic acid and sinapic acid. A gradient elution was employed with a mobile phase consisting of acetonitrile (solution A) and 2% of acetic acid (solution B) as follows: Isocratic elution 100% B, 0–15 min; linear gradient from 100% B to 85% B, 15–30 min; linear gradient from 85% B to 75% B, 30–40 min; linear gradient from 75% B to 50% B, 40–50 min; isocratic elution 50% B, 50–55 min; linear gradient from 50% B to 100% B, 55–60 min; isocratic elution 100% A, 60–70 min; isocratic elution 100% B, 70 min; post-time 6 min before the next injection. The injection volume was 10 lL, the flow rate was 1 mL/min at room temperature, and the duration of a single run was 40 min. All phenolic acids were quantified using an external standard. The total phenolic extracts and standards were analysed under the same analysis conditions and all experiments were replicated three times. Identification of the main phenolic acids as p-hydroxybenzoic, vanillic, gallic acid, syringic acid, p-coumaric acid, caffeic acid, ferulic and sinapic acids were performed by comparisons to the retention time and UV spectra of standards. Standard solutions (2 mg/mL) were subjected to the ethyl acetate extraction procedure described above. Calibration curves were calculated based on the linear correlation between concentration of standards. All quantifications were based on peak area ratios and the samples were analysed in triplicate.

radical reagent ABTS, at 7.0 mM concentration, was prepared by dissolving 0.1920 g of the compound in water, and diluting to 50 mL. To this solution was added 0.0331 g K2S2O8 such that the final persulfate concentration in the mixture be 2.45 mM. The resulting ABTS radical cation solution was left to mature at room temperature in the dark for 12–16 h, and then used for TEAC assays. The matured ABTS radical solution of blue-green colour was diluted with 96% ethanol at a ratio of 1:10. The absorbance of the 1:10 diluted ABTS radical cation solution was 1.28 ± 0.04 at 734 nm. To 1 mL of the radical cation solution, 4 mL of ethanol were added, and the absorbance at 734 nm was read at the end of the first and sixth minute. The procedure was repeated for the sample extract. The volumes of (4x) mL EtOH and x mL sample solution were taken. The reagent blank was prepared with 4 mL EtOH. One millilitre amount of 1:10 diluted ABTS radical cation solution was added to each mixture at 15 s intervals, and well mixed (total volüme = 5.0 mL). The absorbance difference (DA) was found by subtracting the sample extract absorbance from that of the reagent blank (pure radical solution). This was correlated to trolox equivalent antioxidant concentration with the aid of a linear calibration curve (usually the absorbance decrease at the 6th minute was used for calculations). The absorbance of the reagent blank (A0) diminished in the presence of antioxidants, the absorbance decrease (DA) being proportional to antioxidant concentration. The decrease in absorbance (DA) caused by antioxidants, recorded at 734 nm against ethanol at the end of 6th min, reflected the ABTS + radical cation scavenging capacity and was plotted against the concentration of the antioxidant. The TEACABTS value of a given antioxidant represents the ratio of the slope of the DA vs. concentration line of that antioxidant to that of trolox measured under the same conditions of the ABTS decolorisation assay. The TEAC coefficient, being a slope ratio, is unitless.

2.8. Determination of antioxidant activity

2.8.3. CUPRAC assay of total antioxidant activity Estimation of cupric ion reducing antioxidant activity (CUPRAC) was conducted according to the method of Apak et al. (2008). Add 1 mL 1.102 M CuCl2+ + 1 mL 7.5  103 M neocuproine + 1 mL 1 M NH4Ac + x mL 103 M antioxidant neutral solution + (1x) H2O:VT = 4 mL; measure final absorbance at 450 nm. Antioxidant activity of phenolic antioxidants was calculated as trolox equivalents antioxidant capacity (TEAC values) in the CUPRAC method. Sample calculation:

The antioxidant activity of the free (extractable) and bound (hydrolyzable) phenolic compounds were determined using ferric reducing antioxidant power assay (FRAP) (Benzie & Strain, 1996), 2,20 -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation assay and cupric ion reducing antioxidant capacity assay (CUPRAC) (Apak, Guclu, Ozyurek, & Celik, 2008). 2.8.1. FRAP assay of total antioxidant activity FRAP estimation was conducted according to the method as described by Benzie and Strain (1996). For the FRAP estimation, 3 mL of freshly prepared FRAP reagent (incubated at 37 °C) was mixed with 300 lL of distiled water and 100 lL of the test sample (or extraction solvent for the reagent blank). The test samples and blank were incubated at 37 °C for 40 min. At the end of incubation, absorbance was measured immediately at 595 nm. The FRAP reagent was prepared by mixing 25 mL of 0.3 mol L1 acetate buffer (pH 3.6), 2.5 mL of 20 mmol L1 FeCl3  6H2O and 2.5 mL 10 mmol L1 TPTZ solution in 40 mmol L1 HCl. Solutions of trolox dissolved in extraction solvent, ranging from 10 to 100 lmol L1 were used for the preparation of calibration curve. The final result was expressed as equivalent concentration (EC) – the concentration (lmol trolox/g sample) of a sample in reaction mixture having the reducing ability equivalent to that of 1.103 M trolox (it was determined by using the corresponding regression equation). It is important to notice that a lower value indicates higher antioxidant activity in this case. 2.8.2. ABTS assay of total antioxidant activity Estimation of ABTS + radical scavenging activity was conducted according to the method of Apak et al. (2008). The chromogenic

eTR : 1:67  104 Lmol1 cm1 eQR : 7:3  104 Lmol1 cm1 TEACQR ¼ eQR=eTR ¼ 7:3  104 =1:67  104 ¼ 4:38: 2.9. Sensory analysis The sensory evaluation analysis of tarhana soup was held by organising an untrained consumer panel with 22 panelists to determine colour, taste, odor, mouth feel and overall acceptability. A 9-point hedonic scale with 9-like extremely, 8-like very much, 7-like moderately, 6-like slightly, 5-neither like or dislike, 4-dislike slightly, 3-dislike moderately, 2-dislike very much, and 1-dislike extremely was used. For each sample, 100 g dried tarhana powder (dry weight basis) was mixed with 1000 mL water. It was brought to the boiling point and 10 g of butter was added. It was allowed to simmer for 10 min over medium heat with constant stirring. The cooked sample was served to the panelists at a temperature of 70 ± 2 °C (Gocmen et al., 2004). Water and bread were used for clear the palate before each test sample. The samples were

550

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

identified and coded by three-digit random numbers and served to the panelists in random order to guard against any bias. 2.10. Statistical analysis JMP software version 6.0.0 (SAS Institute Inc., Cary, North Carolina, USA) was used to perform the statistical analyses. When significant differences were determined (p < 0.05), the Least Significant Difference (LSD) test was used to determine the differences among means.

performes as a cofactor in enzymatic processes that represent an integral part of the structure of DNA self-repair system. Zn is required for DNA synthesis and repair (Fenech, 2005). The highest level of Fe content was found in the sample with 40% OF (598 mg kg1) while the lowest level of Fe content was determined in the control sample (386 mg kg1). Our results were consistent with those obtained by Tamime, Muir, Khaskheli, and Barclay (2000). As known, anaemia results from Fe deficiency. Conversely, Fe overload (excess iron) may increase the risk of cancer or heart attacks (Hemalatha, Platel, & Srinivasan, 2007). 3.2. Phenolic contents

3. Results and discussion 3.1. Mineral contents The results obtained are shown in Table 1. All mineral levels were determined on a dry weight (dw) basis. According to average levels of minerals in all samples, copper was found to be highest and it was followed by manganese, zinc and iron. The major differences in the mineral contents were in potassium and calcium levels (i.e. apparoximately 2-fold more in tarhana with 40% OF compared with control). Generally significant differences (p < 0.05) between control sample and tarhana samples with OF for Fe, Cu, Zn, P and Ca were associated with the amount of oat flour added. The mineral contents of the samples with OF increased as the level of OF added to the samples was increased. The levels of Cu in tarhana samples supplemented with OF were within the range of 4396–5226 mg kg1 (Table 1). Copper is a component of enzymes required for Fe metabolism and is necessary for the formation of hemoglobin and is required for the function of over 30 proteins including superoxide dismutase, ceruloplasmin, lysyl oxidase, cytochrome c oxidase, tyrosinase and dopamine-bhydroxylase (Arredondo & Nunez, 2005; Vitali, Vedrina Dragojevic, & Sebecic, 2008). Marginal deficits of this essential nutrient can contribute to the formation and progression of a number of diseases (e.g. high blood pressure and infertility) including cardiovascular disease and diabetes. Furthermore, deficits of copper during pregnancy can lead to serious structural malformations in fetus, and persistent neurological and immunological abnormalities on infants (Uriu-Adams & Keen, 2005; Vitali et al., 2008). The Mn value of the sample with 40% OF was maximum (2110 mg kg1) and the Mn value of control was minimum (1576 mg kg1). Mn concentrations of the samples supplemented with OF were significantly higher than control, except the sample with 10% OF (Table 1). The human body contains a total of 10–40 mg of manganese. Manganese is the metal activator for pyruvate carboxylase and it activates various enzymes like some other divalent metal ions (Belitz & Grosch, 1999, chap. 4). Increasing the amount of OF addition led to zinc content increasing from 498 to 654 mg kg1 (Table 1). Zn concentrations of tarhana samples with OF were significantly (p < 0.05) higher than those of control sample. Zinc is a component of a number of enzymes. Zinc deficiency in animals causes disorders while high zinc intake by human body is toxic (Belitz & Grosch, 1999). It

The levels of the free, bound and total phenolic contents of samples were given in Table 2. Total phenolic contents were calculated as the sum of free and bound phenolic contents as suggested by Vitali et al. (2009). Compared with the control sample, the free, bound and total phenolic contents were gradually increased with the addition of OF to tarhana samples. The free phenolic contents significantly (p < 0.05) increased approximately 60–75% with additions of OF. For bound phenolics, the trend of changes in the content was the same as the free phenolics. The highest bound phenolic content (4399.51 mg 100 g1) was determined in the sample supplemented with 40% OF. Total phenolics are mainly made up of the free and bound phenolics in oats. Therefore, its content was influenced by the free and bound phenolics (Xu et al., 2009). Compared with control sample, the total phenolic content increased with the increase in the amount of OF. The data showed that tarhana supplemented with oat flour might be considered as a fairly rich source of phenolic compounds. It might significantly contribute to daily dietary phenolic intake. 3.3. Phenolic acids HPLC is a traditional technique for the analysis of phenolic compounds, such as phenolic acids and polyphenols, such as flavonoids (Xu et al., 2009). The RP-HPLC chromatograms of extracts derived from control sample and from the sample with 40% OF are shown in Fig. 1. The RP-HPLC quantitative analytical results of the phenolic acids extracted from the samples are shown in Table 3. It can be seen from the figures that some compounds such as gallic, vanillic, Table 2 Phenolic contents of tarhana samples* (mg of GAE 100 g1 DW). OF (%)

Free

Bound

Total

0 10 20 30 40

122.49 ± 11.028d 200.99 ± 6.259bc 204.57 ± 0.216b 207.76 ± 43.308ab 217.40 ± 4.137a

2612.01 ± 178.707d 2911.08 ± 373.158cd 2961.17 ± 119.366c 3200.10 ± 351.769bc 4399.51 ± 454.247a

2734.50 ± 301.269c 3112.07 ± 169.537bc 3165.74 ± 120.648bc 3407.86 ± 326.776b 4616.91 ± 438.309a

Data are expressed as means ± standard deviations (n = 3). a–d means superscript with different alphabets in the same column differ significantly (p < 0.05). * Mean values represented by the same letters within the same column are not significantly different at p 6 0.05.

Table 1 Mineral concentrations of tarhana samples* (mg kg1 DW). OF (%)

Fe

Cu

Zn

Mn

K

Mg

P

Ca

0 10 20 30 40

386 ± 2f 468 ± 15de 511 ± 2cd 565 ± 14b 598 ± 11a

4351 ± 59f 4396 ± 199de 4785 ± 81c 4881 ± 61bc 5226 ± 66a

498 ± 12e 568 ± 5d 588 ± 6cd 635 ± 36b 654 ± 16a

1576 ± 80c 1719 ± 36bc 1896 ± 21b 2058 ± 21ab 2110 ± 73a

9.18 ± 7de 15.46 ± 0.05cd 17.27 ± 3.09bc 18.21 ± 18.13ab 18.99 ± 0.48a

1.86 ± 0.01cd 1.94 ± 0.00c 2.26 ± 0.03b 2.41 ± 0.24ab 2.65 ± 0.10a

9.06 ± 0.31d 9.79 ± 0.16c 11.01 ± 1.10bc 11.18 ± 0.04b 12.81 ± 0.37a

6.73 ± 0.41f 8.05 ± 0.03de 10.30 ± 0.09c 11.47 ± 0.87bc 13.03 ± 0.17a

Data are expressed as means ± standard deviations (n = 3). a–f means superscript with different alphabets in the same column differ significantly (p < 0.05). * Mean values represented by the same letters within the same column are not significantly different at p 6 0.05.

551

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

Fig. 1. HPLC chromatograms of the total phenolic extracts from the control (A) and the ample with 40% oat flour (B).

Table 3 Contents of phenolic acid in tarhana samples (lg g1 DW).* OF (%)

Gallic acid

Vanillic acid

Caffeic acid

Syringic acid

p-Coumaric acid

Sinapic acid

Ferulic acid

p-Hydroxybenzoic acid

Total

0 10 20 30 40

31.1 ± 2.38e 58.9 ± 1.17d 76.3 ± 1.39c 94.7 ± 2.07b 122.2 ± 1.66a

163.3 ± 3.07de 403.8 ± 2.58bc 418.9 ± 1.67b 427.8 ± 1.79ab 431.6 ± 2.47a

13.7 ± 0.79ef 42.4 ± 1.07d 57.9 ± 1.37c 71.2 ± 1.56ab 74.7 ± 0.68a

0.7 ± 1.27e 23.4 ± 0.58d 44.0 ± 0.88c 62.0 ± 3.19b 84.7 ± 2.00a

5.2 ± 2.66de 13.1 ± 1.77c 15.7 ± 1.59b 17.9 ± 0.78ab 18.9 ± 1.19a

5.1 ± 1.89c 5.5 ± 0.67bc 6.4 ± 0.78b 8.8 ± 1.37ab 9.1 ± 1.79a

74.7 ± 2.48e 124.8 ± 2.07d 182.7 ± 1.18c 220.6 ± 1.87b 276.2 ± 3.29a

4.6 ± 0.67e 18.1 ± 0.89d 36.5 ± 1.57c 52.8 ± 0.76b 73.5 ± 1.18a

298.4 690 838.4 955.8 1090.9

Data are expressed as means ± standard deviations (n = 3). a–f means superscript with different alphabets in the same column differ significantly (p < 0.05). Mean values represented by the same letters within the same column are not significantly different at p 6 0.05.

*

caffeic, syringic, p-coumaric, sinapic, ferulic, p-hydroxybenzoic acids were detected in our study. These results indicate that OF supplementation improved the phenolic acid contents of tarhana (Table 3). Phenolic acid levels varied significantly (p < 0.05) between control sample and tarhana samples with OF, except sinapic acid. The most abundant phenolic acids were vanillic, followed by ferulic acid and gallic acid in the samples supplemented with OF. The compound with retention time at 21.48 min has been identified as vanillic acid by co-elution with standard. The highest vanillic acid content was found in the sample with 40% OF (431.6 lg g1) while the lowest content of vanillic acid was determined in control sample (163.3 lg g1) (Table 3). Compound at 29.60 min was identified as ferulic acid. Its identity was confirmed by co-elution with a commercial standard. Ferulic acid contents of tarhana samples with OF were significantly (p < 0.05) higher than that of control sample. This result is consistent with the results of Mattila et al. (2005), Xu et al. (2009). Gallic acid detected at 7.23 min by co-elution with a commercial standard was measured in the samples with OF, and it ranged from 58.9 lg g1 to 122.2 lg g1. Gallic acid contents were significantly (p < 0.05) different in control sample and tarhana samples supplemented with OF (Table 3). Compound at 18.65 min was identified as p-hyroxybenzoic acid. Its existence was confirmed by co-elution with a commercial standard. Its content was too low in control, but it significantly (p < 0.05) increased as the OF supplementation to tarhana samples increased. The sample with 40% OF contained nearly 16 times higher p-hyroxybenzoic acid than that of control sample (Table 3).

Furthermore, control sample contained nearly 76 times lesser syringic acid than OF supplemented tarhana samples did (Table 3). There is no literature data for comparing the influence of OF addition on phenolic acid contents of tarhana whereas the data of this study are compatible with those reported by Verardo et al. (2011) who detected same phenolic acids in the oat extracts obtained from commercial oat samples. Finally, there is considerable evidence that higher phenolic acid concentrations are correlated with oat supplementation to tarhana. 3.4. Antioxidant activity Antioxidant activities were investigated using ferric reducing antioxidant power assay (FRAP), ABTS radical cation assay and cupric ion reducing antioxidant activity assay (CUPRAC). The usage of OF in tarhana formulation enhanced levels of antioxidant activity (Table 4). This can be attributed to the rich antioxidant capacities of oat products compared with wheat flour. TEACABTS values of free phenolic extracts were not significantly different in control sample and tarhana samples supplemented with OF. But these values of the samples enriched with OF were scarcely higher than that of control. TEACABTS values measured in the free phenolic extracts ranged from 2.82 to 3.05 lmol trolox/g of sample. The highest value (3.05 lmol trolox/g of sample) was determined by addition of 40% OF (Table 4). There were significant (p < 0.05) increases in TEACABTS values of bound phenolic extracts in the samples with OF after 30% addition level compared to those of control sample (Table 4). As the levels of OF increased in formulations, these values increased. TEACABTS

552

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

Table 4 Antioxidant activity in tarhana samples* (lmol trolox g1 DW). OF (%)

0 10 20 30 40

ABTS

CUPRAC

FRAP

Free

Bound

Free

Bound

Free

Bound

2.39 ± 0.738b 2.82 ± 0.269ab 2.85 ± 0.146ab 2.87 ± 0.257ab 3.05 ± 0.102a

134.02 ± 28.328bc 138.42 ± 46.188bc 188.82 ± 22.259ab 199.54 ± 20.337a 204.48 ± 16.456a

2.54 ± 0.017de 4.70 ± 0.108c 5.99 ± 0.007bc 6.06 ± 0.339ab 7.60 ± 0.103a

56.77 ± 9.858d 85.47 ± 8.007cd 91.18 ± 35.176bc 95.27 ± 30.208b 111.59 ± 26.059a

2.01 ± 0.114c 2.70 ± 0.206bc 3.15 ± 0.286b 3.48 ± 0.425ab 3.92 ± 0.221a

2.90 ± 0.355cd 3.18 ± 0.317c 3.88 ± 0.237ab 3.98 ± 0.183ab 4.43 ± 1.649a

Data are expressed as means ± standard deviations (n = 3). a–e means superscript with different alphabets in the same column differ significantly (p < 0.05). * Mean values represented by the same letters within the same column are not significantly different at p 6 0.05.

Table 5 Sensorial properties of tarhana samples*. OF (%)

Colour

Taste

Odour

Mouth feel

Overall acceptability

0 10 20 30 40

5.90 ± 1.676 6.58 ± 1.169 6.00 ± 1.477 6.80 ± 1.318 5.79 ± 1.646

6.15 ± 2.249 6.63 ± 1.503 6.15 ± 1.528 6.53 ± 1.577 5.58 ± 1.802

5.75 ± 2.017 6.47 ± 1.578 5.80 ± 1.319 6.40 ± 1.267 5.79 ± 1.778

6.37 ± 2.309 6.53 ± 1.427 6.05 ± 1.388 6.35 ± 1.501 5.79 ± 1.749

6.05 ± 2.038 6.31 ± 1.577 5.89 ± 1.679 6.42 ± 1.637 5.56 ± 1.759

Data are expressed as means ± standard deviations (n = 3). Mean values represented by the same letters within the same column are not significantly different at p 6 0.05.

*

values measured in the bound phenolic extracts ranged from 138.42 to 204.48 lmol trolox/g in the samples with OF. While the highest value (204.48 lmol trolox/g of sample) was determined in the sample with 40% OF, the lowest value (134.02 lmol trolox/g of sample) was found in control sample (Table 4). TEACCUPRAC value of free phenolic extract of the sample with 40% OF had the highest (7.60 lmol trolox/g sample) whereas the control sample had the lowest value (2.54 lmol trolox/g sample). The results also showed that OF addition in tarhana formulation exhibited significantly (p < 0.05) increasing antioxidant activity with the increase in the addition levels (Table 4). Compared with control sample, OF addition showed significant effects (p < 0.05) on TEACCUPRAC values of bound phenolic extracts after 20% addition level of OF (Table 4). In the sample enriched with 40% OF was found to be the sample with the highest (111.59 lmol trolox/g sample) antioxidant potential. As the levels of OF increased in formulation, these values also increased. The results of TEACFRAP values in the free phenolics showed that samples enriched with OF had significantly (p < 0.05) higher antioxidant activity compared to the control sample except the level of 10 and 20% OF (Table 4). In the free phenolic extracts measured TEACFRAP values ranged from 2.70 to 3.92 lmol trolox/g of the samples with OF. The highest value (3.92 lmol trolox/g of sample) was achieved by addition of 40% OF. Significant (p < 0.05) increases were measured in TEACFRAP values of bound phenolic extracts in the samples with OF compared to that of control sample except 10% OF addition (Table 4). TEACFRAP values measured in the bound phenolics ranged from 3.18 to 4.43 lmol trolox/g of sample. While the highest value (4.43 lmol trolox/g of sample) was determined in the sample with 40% OF, the lowest value (2.90 lmol trolox/g of sample) was found in control sample. The data showed that there were positive correlations among the results of antioxidant capacities and total phenolic acids and total phenolic contents of the samples. As the total phenolic acids and total phenolic contents of the samples increased, antioxidant capacities of the samples increased. Fang, Hu, Liu, Chen, and Ye (2008) also reported that the antioxidant capacities of extracts are mainly due to the total phenolic content and total phenolic acids.

3.5. Sensory findings Sensorial properties of tarhana samples are shown in Table 5. All of the soups prepared with OF and control sample were comparable in terms of the sensorial properties. OF addition did not cause a deteriorative effect on this property. The tarhana samples supplemented with 30% OF had the highest colour scores. Taste values obtained by sensorial analysis of the tarhana soups varied between 5.58 and 6.63. The highest odour values were determined in the samples supplemented with 10% and 30% OF (6.47 and 6.40, respectively). Similarly, in the samples with 10% and 30% OF, the highest taste values (6.63 and 6.53, respectively) were obtained. Overall acceptances of tarhana soups were found to be the best with the 30% OF. The results of sensorial analysis showed that supplementation of OF into tarhana did not cause any undesirable taste or odour. Oat flour supplementation to tarhana samples resulted in acceptable soup properties. Panelists emphasised a sweet taste as the OF increased in the soups (data were not given). 4. Conclusion Oat flour addition enhanced the mineral contents of the tarhana samples. It was observed that OF used in this study is a good source of minerals as compared to wheat flour. OF addition to tarhana positively affected phenolic contents. Compared with control sample, the total phenolic content increased with the increase in the amount of OF added. As the level of OF was increased, phenolic acids levels also increased. The most abundant phenolic acids were vanillic and ferulic acids, and they were followed by gallic acid in the samples. Tarhana samples supplemented with OF also showed higher antioxidant activities than those of control sample. Thus, the use of OF in tarhana formulation may provide health benefits and nutritional and functional advantages by raising the levels of mineral and phenolic contents, phenolic acids and antioxidant activity. The results of sensorial analysis showed that supplementation of OF into tarhana did not cause any undesirable taste and odour. The results confirmed that oat flour (OF) is a suitable ingredient for tarhana production. OF either had no deteriorative effect or had some improving effects on nutritional and functional properties of

A. Kilci, D. Gocmen / Food Chemistry 151 (2014) 547–553

tarhana. Slightly lower sensory values in the sample with 40% OF might decrease the acceptability of this tarhana soup as compared to control (wheat based tarhana). However, the sensory properties of soups with 40% and more than this level of oat flour can be improved by further studies. Acknowledgements This study is a part of MSc thesis of the first author. The authors would like to thank The Scientific and Technological Research Council of Turkey (TUBITAK) for their financial support to this research project (Project No. TOVAG 110 O 805). References Apak, R., Guclu, K., Ozyurek, M., & Celik, S. E. (2008). Mechanism of antioxidant capacity assays and the CUPRAC (cupric ion reducing antioxidant capacity) assay. Microchimica Acta, 16, 413–419. Arredondo, M., & Nunez, M. T. (2005). Iron and copper metabolism. Molecular Aspects of Medicine, 26, 313–327. Belitz, H. D., & Grosch, W. (1999). Food chemistry (2nd ed.). New York: SpringerVerlag Berlin Heidelberg. Benzie, I. F. F., & Strain, J. J. (1996). The ferric reducing ability of plasma (FRAP) as a measure of ‘‘Antioxidant Power’’: The FRAP assay. Analytical Biochemistry, 239, 70–76. Butt, M. S., Tahir-Nadeem, M., Khan, M. K. I., & Shabir, R. (2008). Oat: Unique among the cereals. European Journal of Nutrition, 47, 68–79. Daglioglu, O. (2000). Tarhana as a traditional Turkish fermented cereal food, its recipe, production and composition. Nahrung, 44, 85–88. Degirmencioglu, N., Gocmen, D., Dagdelen, A., & Dagdelen, F. (2005). Influence of tarhana herb (Echinophora sibthorpiana) on fermentation of tarhana, Turkish traditional fermented food. Food Technology and Biotechnology, 43(2), 175–179. Fang, Z., Hu, Y., Liu, D., Chen, J., & Ye, X. (2008). Changes of phenolic acids and antioxidant activities during potherb mustard (Brassica juncea, Coss.) pickling. Food Chemistry, 108, 811–817. Fenech, M. (2005). The genome health clinic and genome health nutriogenomics concepts: Diagnosis and nutritional treatment of genome and epigenome damage on individual basis. Mutagenesis, 20, 255–269. Gocmen, D., Gurbuz, O., Roussef, R. L., Smoot, J. M., & Dagdelen, A. F. (2004). Gas chromatographic-olfactometric characterisation of aroma active compounds in sun-dried and vacuum-dried tarhana. European Food Research and Technology, 218, 573–578. Gray, D. A., Auerbach, R. H., Hill, S., Wang, R., Campbell, G. M., & Webb, C. (2000). Enrichment of oat antioxidant activity by dry milling and sieving. Journal of Cereal Science, 32, 89–98. Hemalatha, S., Platel, K., & Srinivasan, K. (2007). Zinc and iron contents and their bioaccessibility in cereals and pulses consumed in India. Food Chemistry, 102, 1328–1336.

553

Kestin, M., Moss, R., Clifton, P. M., & Nestel, P. J. (1990). Comparative effects of three cereal brans on plasma lipids, blood pressure and glucose metabolism in mildly hypercholesterolemic men. The American Journal of Clinical Nutrition, 52, 661–666. Liu, L., Zubik, L., Collins, F. W., Marko, M., & Meydari, M. (2004). The antiatherogenic potential of oat phenolic compounds. Atherosclerosis, 175, 39–49. Malkki, Y., Myllymaki, O., Teinila, K. & Koponen, S. (2004). Method for preparing an oat product and a foodstuff enriched in the content of beta-glucan. US patent, 6, 797-307. Mattila, P., Pihlava, J. M., & Hellström, J. (2005). Contents of phenolic acids, alkyland alkenylresorcinols, and avenanthramides in commercial grain products. Journal of Agricultural and Food Chemistry, 53, 8290–8295. McMullen, M. S. (2000). Handbook of cereal science and technology. In C. Kulp & J. G. Ponte (Eds.), Oats (pp. 127–148). New York: Inc. 270 Madison Avenue. Ozdemir, S., Gocmen, D., & Kumral, A. (2007). A traditional Turkish fermented cereal food: Tarhana. Food Reviews International, 23, 107–121. Peterson, D. M., Emmons, C. L., & Hinns, A. H. (2001). Phenolic antioxidants and antioxidant activity in pearling fractions of oat groats. Journal of Cereal Science, 33, 97–103. Rodriguez, H., Curiel, J. A., Landete, J. M., Rivas, B. I., Felipe, F. L., Cordoves, C. G., et al. (2009). Food Phenolics and lactic acid bacteria. International Journal of Food Microbiology, 132, 79–90. Sahan, Y., Basoglu, F., & Gucer, S. (2007). ICP-MS analysis of a series of metals (Namely: Mg, Cr Co, Ni, Fe, Cu, Zn, Sn, Cd and Pb) in black and green olive samples from Bursa, Turkey. Food Chemistry, 105, 395–399. Tamime, A. Y., Muir, D. D., Khaskheli, M., & Barclay, M. N. I. (2000). Effect of processing conditions and raw materials on the properties of Kishk 1. Compositional and microbiological qualities. Lebensmittel-Wissenschaft und Technologie, 33, 444–451. Tarakci, Z., Dogan, I. S., & Koca, A. F. (2004). A traditional fermented Turkish soup, tarhana, formulated with corn flour and whey. International Journal of Food Science and Technology, 39, 455–458. Temiz, A., & Pirkul, T. (1991). Chemical and sensorial properties of tarhana samples produced with different components. Gida, 16(1), 7–13 (in Turkish). Uriu-Adams, J. Y., & Keen, C. L. (2005). Copper, oxidative stress, and human health. Molecular Aspects of Medicine, 26, 268–298. Verardo, V., Serea, C., Segal, R., & Caboni, M. F. (2011). Free and bound minor polar compounds in oats: Different extraction methods and analytical determinations. Journal of Cereal Science, 54, 211–217. Vitali, D., Vedrina Dragojevic, I., & Sebecic, B. (2008). Bioaccessibility of Ca, Mg, Mn and Cu from whole grain tea biscuits: Impact of proteins, phytic acid andpolyphenols. Food Chemistry, 110, 62–68. Vitali, D., Vedrina Dragojevic, I., & Sebecic, B. (2009). Effects of incorporation of integral raw materials and dietary fibre on the selected nutritional and functional properties of biscuits. Food Chemistry, 114, 1462–1469. Webster, F. H. (2002). Whole-grain foods in health and disease. In L. Marquart, J. L. Slavin, & R. G. Fulcher (Eds.), Whole-grain oats and oat product (pp. 83–123). Minnesota: American Asssociation of Cereal Chemists, Inc. St. Paul. Xu, J. G., Tian, C. R., Hu, Q. P., Luo, J. Y., Wang, X. D., & Tian, X. D. (2009). Dynamic changes in phenolic compounds and antioxidant activity in oats (Avena nuda L.) during steeping and germination. Journal of Agricultural Food Chemistry, 57, 10392–10398.