Characterization of the Aroma-Active, Phenolic, and Lipid Profiles of

Article pubs.acs.org/JAFC

Characterization of the Aroma-Active, Phenolic, and Lipid Profiles of the Pistachio (Pistacia vera L.) Nut as Affected by the Single and Double Roasting Process Juan José Rodríguez-Bencomo,† Hasim Kelebek,§ Ahmet Salih Sonmezdag,≠ Luis Miguel Rodríguez-Alcalá,‡ Javier Fontecha,‡ and Serkan Selli*,# †

Department of Chemical Engineering, University of Rovira i Virgili, Av. Paisos Catalans 26, 43007-Tarragona, Spain Faculty of Engineering and Natural Sciences, Department of Food Engineering, Adana Science and Technology University, 01100 Adana, Turkey ≠ Araban Vocational High School, Department of Organic Agriculture, University of Gaziantep, 27600 Gaziantep, Turkey ‡ Instituto de Investigación en Ciencias de la Alimentación (CSIC-UAM), Food Analysis and Bioactivity, Department of Lipids, Universidad Autónoma de Madrid (UAM), Nicolás Cabrera, 9, 28049, Madrid, Spain # Faculty of Agriculture, Department of Food Engineering, Cukurova University, 01330, Adana, Turkey

Downloaded by KTH ROYAL INST OF TECHNOLOGY on August 29, 2015 | http://pubs.acs.org Publication Date (Web): August 28, 2015 | doi: 10.1021/acs.jafc.5b02576

§

ABSTRACT: The pistachio (Pistacia vera L.) nut is one of the most widely consumed edible nuts in the world. However, it is the roasting process that makes the pistachio commercially viable and valuable as it serves as the key step to improving the nut’s hallmark sensory characteristics including flavor, color, and texture. Consequently, the present study explores the effects of the single-roasting and double-roasting process on the pistachio’s chemical composition, specifically aroma-active compounds, polyphenols, and lipids. Results showed the total polyphenol content of increased with the roasting treatment; however, not all phenolic compounds demonstrated this behavior. With regard to the aroma and aroma-active compounds, the results indicated that roasting process results in the development of characteristics and pleasant aroma of pistachio samples due to the Maillard reaction. With regard to lipids, the pistachio roasting treatment reduced the concentration of CN38 diacylglycerides while increasing the amount of elaidic acid. KEYWORDS: pistachio, roasting process, polyphenols, antioxidant capacity, lipid, aroma-active compounds

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INTRODUCTION

Regarding the effects of the roasting process on pistachios, some studies have focused on moisture, texture, hardiness, color, and other sensory attributes;14,15 while other works have studied the variation of the chemical composition of the kernel. Kashant et al.16 studied the compositional changes in carbohydrates, proteins, and amino acids. Certain works have examined the chemical compounds directly related to some organoleptic characteristics. Hojjati et al.,1 for instance, studied the effects on the volatile composition and color produced by the gentle roasting process of Iranian pistachios (135 °C for 20 min), observing a limited production of pyrazines and a decrease in lightness (L value) resulting from Maillard-related browning. Using a more intense roasting process (200 °C for varying time lengths), Gogus et al.17 evaluated changes in the composition of volatiles in Pistacia terebinthus and observed an important effect on the levels of compounds resulting from the Maillard reaction (i.e., pyrazines, furans, and benzene derivatives). Although much data on pistachio composition has been published, there is a lack of information on the transformations resulting from the roasting process, including a wide range of

The pistachio (Pistacia vera L.) nut is one of the world’s most popular edible nuts and an important agricultural commodity for a number of countries. Iran, USA, and Syria are the main pistachio producers as well as Turkey, where the major cultivars grown are Uzun, Kirmizi, Siirt, Halebi, and Ohadi. Pistachios are consumed raw or roasted, salted or unsalted, by themselves as savory snacks or as major ingredients in many traditional desserts, for which producers generally prefer the Uzun and Kirmizi cultivars. As with other edible nuts, the roasting process of the pistachio is a vital step to enhance its sensory characteristics of flavor, color, and texture. The moisture loss resulting from the heat treatment produces a more crisp and choice texture while at the same time the change in chemical composition resulting from the Maillard reaction and lipid oxidation improves color and aroma.1,2 Using both fresh and roasted pistachios of various cultivars, several studies have investigated the nut’s physical properties and chemical compositions, including volatile and phenolic composition, lipid composition, sensory characteristics, antioxidant capacity, and aroma-active compounds.2−9 In addition, quite a few studies have focused on aspects of ripening and harvesting times, production, packing and storage conditions, and compositional effects of these processes on the end product’s quality.10−13 © XXXX American Chemical Society

Received: March 20, 2015 Revised: August 14, 2015 Accepted: August 22, 2015

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DOI: 10.1021/acs.jafc.5b02576 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry

authentic standards and by comparing the retention times and spectra.11 Quantification was performed by external calibration with standards. Concentration was expressed as mg per 100 mg of pistachio sample. Antioxidant Capacity (DPPH Assay). The electron donation ability of the extract was measured by bleaching of the purple-colored solution of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical according to the method of Tsantili et al.11 An aliquot of 0.1 mL of the methanol/ water phenolic extract of the pistachio samples (diluted 1/25) was added to 3.9 mL of DPPH solution in methanol (6 × 10−5 M). The mixture was shaken vigorously and left standing at room temperature for 30 min. The absorbance of the resulting solution was then measured at 515 nm after 30 min by a Shimadzu UV-1700 spectrophotometer (Kyoto-Japan). Results were expressed as Trolox equivalent antioxidant capacity. Trolox standard solutions were prepared at a concentration ranging from 1 to 50 μM. Obtaining of Aroma Extract (Purge and Trap System) and Olfactometric Analysis. The purge and trap system used to carry out the extraction process consisted of a nitrogen source controlled by a flow-meter and connected to a splitter system to divide the flow in several channels in order to purge three samples at the same time. A standard 20 mL vial capped with a crimp cap with a septum was used to contain the solid sample. The needle of the source of N2 and the cartridge were installed through the septum to purge and trap the aroma compounds. As adsorbent, 200 mg of Lichrolut EN resins from Merck was chosen as the most suitable material for aroma compounds retention according to the literature.18,19 The temperature of the vial sample was controlled by a thermostated bath. The sample of pistachio, previously shelled and milled with a laboratory blender, was placed into a 20 mL vial (3 g in order to avoid the caking of the solid) removing oxygen from the headspace with nitrogen. The optimized conditions of the purge and trap method were the following: sample was preincubated at the optimized purging temperature (60 °C) for 10 min. The purge and trap process was carried out for 90 min with a nitrogen flow of 500 mL/min. After this was completed, the compounds retained in the cartridge were eluted with 6 mL of dichloromethane at very a slow flow. The eluate was dried with sodium sulfate and concentrated with a Dufton column until 200 μL remained (at 45 °C). β-Ionone and 2-octanol were used as internal standards. The samples were stored at −20 °C until GC analysis. The aroma compounds evaluated for the optimization of purge and trap method belong to different chemical families with a wide range of volatility, and they are presented in Table 1. The repeatability of the purge and

compositional parameters and the evaluation of their organoleptic significance. Hence, the aim of this work was to characterize the formation of (i) key odorants, (ii) polyphenols, and (iii) lipid from the pistachio cultivar Uzun (Pistacia vera) under two different roasting conditions. Moreover, a purge-andtrap method for obtaining an aroma extract was optimized.


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MATERIALS AND METHODS

Samples. The Uzun cultivar samples of P. vera pistachio nuts from Gaziantep, Turkey, were supplied by a local company. In the same factory, the pistachios were subjected to standard roasting processes to obtain single-roasted (160 °C for 20 min) and double-roasted (160 °C for 22 min) samples and then cooled for 10 min at room temperature. The three types of samples, raw, single-roasted, and double-roasted, were then stored in vacuum-sealed plastic bags prior to analysis. Raw nuts were used as the control to compare against the effect of two different roasting conditions. Chemicals. Hexane, methanol, acetonitrile, formic acid, dichloromethane, and chloroform were purchased from LabScan (Dublin, Ireland) and Merck (Darmstad, Germany); potassium hydroxide and sodium sulfate-1-hydrate from Panreac (Barcelona, Spain); and 1,2,3tritridecanoylglycerol (99%) and dilinolein (98%) from Sigma (St. Louis, USA). Reference milk fat butter CRM-519 (EU Commissions; Brussels, Belgium) was purchased from Fedelco Inc. (Madrid, Spain). FAME standards mix GLC-Nestlé36 and tritridecanoin (99%) were from Nu-Chek Prep, Inc. (Elysian, Minnesota, USA). Protocatechuic acid, catechin, chlorogenic acid, eriodictyol-7-O-glucoside, rutin, eriodictyol, and luteolin were purchased from Sigma-Aldrich (St. Louis, USA). n-Pentanal, α-pinene, 2,3-pentanedione, β-pinene, Nmethylpyrrole, hexanal, (E)-2-pentenal, limonene, methyl pyrazine, styrene, ocimene, furfural, terpinolene, 2,5-dimethyl pyrazine, acetic acid, 2,6-dimethyl pyrazine, 2-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-3-methylpyrazine, acetylfuran, trimethylpyrazine, 2-ethyl-3,5dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 1-octen-3-ol, γ-butyrolactone, benzaldehyde, furfuryl alcohol, (−)-menthol, 1-methyl-2pyrrolidinone, p-cymene-8-ol, hexanoic acid, benzyl alcohol, 2phenylethanol, pyrrole-2-carboxaldehyde, 5-methyl-1H-pyrrole-2-carbaldehyde, octanoic acid, p-cresol, and 4-ethylphenol were purchased from Sigma-Aldrich (St. Louis, USA). Deionized water was obtained via the Milli-Q water purification system by Millipore Corp. (SaintQuentin, France). For retention index calculation, mixtures C8−C20 and C21−C40 were purchased from Fluka. All other reagents used were of analytical grade. Phenolic Compounds Analysis and Antioxidant Activity. Extraction of Phenolic Compounds. The extraction of phenolic compounds was carried out according to Tsantili et al.11 after some modifications. The pistachio samples were ground (with seed coat) with a laboratory blender, and 5 g samples were prepared in duplicate. Each sample was extracted with 15 mL of 85% methanol by mixing with a magnetic stir bar for 2 h. The extract was separated and the solid was washed with 5 mL of 85% methanol. The two extracts were combined, filtered, and evaporated in a vacuum under 20 °C until the volume was reduced to 3 mL. Then, the extract was filtered through a 0.45-μm pore size membrane filter before injection. HPLC Analysis of Phenolic Compounds. An Agilent 1100 HPLC system (Agilent Technologies, Palo Alto CA, USA) with a diode array detector operated by Windows NT based ChemStation software was used for the phenolic compounds analysis. Separation was performed on a Beckman Ultrasphere ODS column (Roissy, France; 4.6 mm × 250 mm, 5 μm). The mobile phase consisted of water with 5% formic acid (solvent A; v/v) and acetonitrile with 40% solvent A (solvent B; v/v). Phenolic compounds were eluted under the following conditions: 1 mL/min flow rate with the temperature set at 25 °C; isocratic conditions from 0 to 15 min with 0% solvent B; gradient conditions from 0% to 20% solvent B in 30 min; from 20% to 50% solvent B in 40 min; and from 50% to 100% solvent B until 5 min. The wavelengths of the diode array detector (DAD) were set at 280, 320, and 360 nm for monitoring phenolic compounds. The identification of the phenolic compounds was obtained by using

Table 1. Compounds Selected for Optimization of Purgeand-Trap Method compound

LRIa

molecular weight

boiling point (°C)

log Pb

RSD (%)c

limonene methylpyrazine furfural benzaldehyde γ-butyrolactone octanoic acid

1156 1194 1365 1420 1513 1957

136 94 96 106 86 144

178 137 161.7 179 204 239

4.57 0.21 0.41 1.48 −0.64 3.05

7.2 2.1 5.3 3.7 5.7 17.9

a

Linear retention index calculated based on DB-WAX phase. Hydrophobic constant obtained from EPIWEB suite. cRepeatability of purge and trap optimized extraction method (n = 3). b

trap method for the optimized conditions is also presented in Table 1. For the optimization all experiments were carried out in duplicate with the double roasted sample. GC-FID, GC-MS, and GC-MS-O Analyses of Aroma Compounds. The gas chromatography system consisted of an Agilent 6890 chromatograph equipped with a flame ionization detector (FID) (Wilmington, DE, USA), an Agilent 5973 mass selective detector (MSD) (Wilmington, DE, USA), and a Gerstel ODP-2 (Baltimore, MD, USA) sniffing port. This system allowed us to simultaneously obtain a FID signal, MS signal (for the identification), and the odor B


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Journal of Agricultural and Food Chemistry characteristics of each compound detected in the sniffing port. The oven temperature of the DB-Wax column was first held at 40 °C (for 10 min) and then increased from 40 to 160 °C at a rate of 3 °C/min and then to 240 °C at 6 °C/min, with a final hold at 240 °C for 25 min. The pressure of the column was constant at 20.0 psi and 3 μL was injected in pulsed splitless mode. The MS (electronic impact ionization) conditions were ionization energy of 70 eV, mass range m/z of 33−350 amu in combined SCAN/SIM mode. Contents of volatile compounds were expressed as relative peak area to internal standard (β-ionone). Retention index were calculated by injection of commercial mixtures of alkanes. Aroma Extract Dilution Analysis (AEDA). Olfactometric analysis was carried using two experienced sniffers. For AEDA, the concentrated aromatic extract (200 μL) of the pistachio samples was stepwise diluted 1:1 using dichloromethane as the solvent to obtain dilutions of 1:2, 1:4, 1:8, 1:16, with dilutions continuing through 1:512. Odor evaluation of the dilutions was continued until no odorant could be detected by GC-O. Each odorant was thus assigned a flavor dilution factor (FD factor) representing the last dilution in which the odorants was still detectable. The identification of aroma compounds was carried out by comparison with the mass spectra of commercial compounds (when available) and with the mass spectra of NIST library. Lipid Profile Analysis. Isolation of Lipids. Shelled pistachios (40 g) were carefully cut into small pieces. Samples were then crushed into fine particles at 8000 rpm using an ultraturrax T25 (Ika-Werke, Staufen, Germany). A portion equaling 3 g was transferred into a 50 mL glass falcon tube (Vidrafoc, Barcelona, Spain), and lipids were isolated according to the Folch method modified by Iverson et al.20 Finally, extracts were centrifuged (5 min, 8000g) to avoid impurities and chloroform removed by using rotatory evaporation. Then, lipids were accurately weighed. Extraction was carried out in triplicate. Analysis of Triacylglycerols and Diacylglycerols. Triacylglycerols (TG) and diacylglycerols (DG) were analyzed on a CLARUS 400 gas chromatograph (PerkinElmer, Massachusetts, USA) equipped with FID detector and a Rtx-65TG column (30 m × 0.25 mm × 0.10 μm; Restek Corporation, Bellefonte, Pennsylvania, USA) using injector, detector, oven temperature and chromatographic conditions as prescribed by Fontecha et al.21 Response factors were calculated by the injection of CRM-519 and dilinolein. Under these conditions, the limits of quantification (LOQ) were 1.14 mg TG/mL (R2 = 0.9996) and 1.22 mg DG/mL (R2 = 0.9993). Injections were performed in triplicate. Analysis of Fatty Acid Methyl Esters. For the determination of the fatty acid composition, samples measuring 25 mg were added with tritridecanoin (200 μL, 1.24 mg/mL) and derivatized to fatty acid methyl esters (FAME) with 2 N methanolic KOH solution according to the International Dairy Federation procedure (ISO-IDF, 2002).22 FAME were analyzed (1 μL; 1:10 split ratio) in a 6890 Agilent GLC (Palo Alto, California, USA) equipped with a MS detector (Agilent 5973N), fitted with a CPSil-88 capillary column (100 m × 0.25 mm id × 0.2 μm film thickness, Chrompack, Middelburg, Netherlands). The MS conditions were 250 °C transfer line temperature; 230 °C source temperature; 150 °C quad temperature; electron impact ionization of 70 eV; and scan operational mode, 50−550 Da. Oven temperature ́ program and conditions were set according to Rodriguez-Alcalá et al.23 Response factors were calculated by injection of GLC-Nestlé36. Under these conditions, the limit of quantification (LOQ) was 0.05 μg/mL (R2: 0,9991). All analyses were carried out in triplicate. Statistical Analysis. In a first instance all data were first subjected to an exploratory analysis to test normal distribution and homogeneity of variance. Thus, results regarding composition of volatiles and phenolics as well as antioxidant capacity were submitted to the oneway analysis of variance (ANOVA). Version 7.1 of STATISTICA for Windows was used for data processing (StatSoft, Inc., 2005, www. statsoft.com). For the lipid profile, data were analyzed according to ANOVA with the Bonferroni test as a follow-up in order to evaluate statistical differences among groups using version 22 of IBM SPSS Statistics for

Mac (IBM, Armonk, NY). For all the analysis the level of significance was set to p < 0.05, while 0.05 < p < 0.1 was established as the trend.

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RESULTS AND DISCUSSION Phenolic Composition and Antioxidant Capacity of Pistachios. The phenolic acids and flavonoids identified in hydroalcoholic extracts of raw, single-roasted, and doubleroasted pistachios are presented in Table 2. A total of seven Table 2. Phenolic Compounds and Antioxidant Capacity of Pistachios (mg/100 g fw)a compound protocatechuic acid catechin chlorogenic acid eriodictyol-7-Oglucoside rutin eriodictyol luteolin total antioxidant capacity (μmol of TE g of fw)

raw

single-roasted

double-roasted

3.14 ± 0.26 a 4.81 ± 0.52 a 4.96 ± 0.13 4.10 ± 0.42

3.96 ± 0.05 b 8.64 ± 1.48 b 3.99 ± 0.78 3.64 ± 1.15

8.59 ± 0.33 c 8.72 ± 0.82 b 5.79 ± 0.09 3.91 ± 0.35

3.01 ± 0.12 a 2.17 ± 0.04 0.78 ± 0.01 a 26.2 ± 1.2 a 8.05 ± 0.21

3.51 ± 0.10 b 2.19 ± 0.01 0.72 ± 0.02 a 32.4 ± 1.0 b 9.76 ± 0.22

5.43 ± 0.10 c 2.67 ± 0.28 1.22 ± 0.06 b 42.4 ± 1.9 c 11.5 ± 2.0

a

Different letters in a row for significant effect of processing (p < 0.05).

phenolic compounds (protocatechuic acid, catechin, chlorogenic acid, eriodictyol-7-O-glucoside, rutin, eriodictyol, luteolin) were detected and quantified. The total phenolic content increased alongside the heat treatment in the samples, with the double-roasted nuts having the highest total phenolic compound content (42.4 mg/100 g fw). These results are in line with similar studies conducted using other types of nuts such as peanuts and almonds.24,25 Thermal processing may release more bound phenolic acids from the breakdown of cellular constituents, although disruption of cell walls also releases the oxidative and hydrolytic enzymes that can destroy the antioxidants in fruits and vegetables.26 The phenolic acids in the pistachios were protocatechic acid and chlorogenic acid, positively identified by comparing their retention and UV−vis characteristics to commercial standards. Protocatechuic acid varied between 3.14−8.59 mg per 100 g of pistachios. Double-roasted nuts had almost three times as much protocatechuic acid as their raw and single-roasted counterparts, suggesting a liberation of protocatechuic acid during heat processing. Thus, double-roasted kernels contained significantly (p < 0.05) more protocatechuic acid than the other samples. Conversely, thermal processing did not affect the content of chlorogenic acid present in pistachio extracts, and there was no significance in the results obtained. In a previous study, Liu et al.27 quantified the bioactives in the whole nut, nutmeat, and skin of California pistachios and found protocatechuic acid to be between 0.2 and 4.6 mg/100 g fw. Mandalari et al.28 not only observed that protocatechuic acid concentration increased with heat treatment in pistachios, but also identified a small amount of chlorogenic acid solely in the salted and roasted nuts. The phenolic compounds may differ with respect to their binding status, dependent on specific aspects of their chemical structures. Thus, the most effective processes to release phenolic acids from plant tissues may not be the same. Major flavonoids identified in the present study were catechin, eriodictyol-7-O-glucoside, and rutin, comprising C


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Figure 1. Optimization of the purge and trap method: effect of temperature (1A), nitrogen purging flow (1B), and purging time (1C) on recovery of volatiles from pistachio.

temperature treatments, and last raw samples, which concurs with the present study. Furthermore, Tomanio et al.8 and Martorana et al.29 investigated the phenolic composition of pistachio seed and skin obtained from nuts grown in Bronte, Sicily. They quantified rutin as the major phenolic compound of the Bronte variety of P. vera. The antioxidant potential of the pistachio samples was assessed by using the DPPH assay method (Table 2), revealing a slight trend of increasing DPPH values with the roasting process. Similarly, Chandrasekara et al.25 mentioned that the antioxidant levels of cashew nuts increased as the roasting time

4.81−8.72 mg, 3.1−3.91 mg, and 3.01−5.43 mg per 100 g of pistachios, respectively. Our results shows that double-roasted samples had a 2-fold higher flavonoid content compared to raw and single-roasted nuts. It is well-established that flavonoids are effective natural antioxidants. The results obtained in the HPLC analysis suggest release and isomerization of such compounds during heat treatment of pistachios. Chandrasekara et al.25 measured the effect of roasting on phenolic content and antioxidant properties of testa-containing and testa-free kernels of cashew nuts. These authors found the highest levels of flavonoids at high-temperature treatments, followed by lowD


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Table 3. Volatile Composition of Pistachio Samplesa LRIb

compounds

raw

single-roasted

double-roasted

identificationc

960 978 996 1010 1018 1034 1037 1068 1075 1113 1119 1156 1158 1185 1189 1194 1203 1211 1229 1252 1257 1259 1272 1311 1318 1330 1333 1355 1365 1376 1384 1390 1405 1420 1425 1426 1429 1457 1513 1516 1551 1561 1570 1586 1613 1719 1729 1745 1755 1766 1802 1894 1906 1918 1957 1963 1969 2053 2059

n-pentanal 2-methyl-3-pentanone 3-methyl-2-pentanone α-pinene 2,3-pentanedione camphene hexanal β-pinene N-methylpyrrole 3-carene (E)-2-pentenal limonene (2 + 3)-methyl-1-butanol styrene 2-methyl-1-penten-3-ol methylpyrazine ocimene 3-methyl-1-penten-3-ol terpinolene 2,5-dimethylpyrazine 2,6-dimethyl-pyrazine 2-ethylpyrazine 2,3-dimethylpyrazine 2-ethyl-5-methylpyrazine 2-ethyl-6-methylpyrazine 2-ethyl-3-methylpyrazine trimethylpyrazine acetic acid furfural 2-ethyl-3,6-dimethylpyrazine 1-octen-3-ol 2-ethyl-3,5-dimethylpyrazine acetylfuran benzaldehyde ethylhexanol 2-methyl-3,5-diethylpyrazine camphor 2-methyl-6-(1-propenyl)-pyrazine γ-butyrolactone 5-methyl-1H-pyrrole-2-carbaldehyde isopropenylpyrazine furfuryl alcohol (−)-menthol 1-methyl-2-pyrrolidinone N-acetyl-4(H)-pyridine 1-(2-furanylmethyl)-1H-pyrrole p-propenylanisole hexanoic acid p-cymen-8-ol benzyl alcohol 2-phenylethanol pyrrole-2-carboxaldehyde DL-pantolactone furaneol octanoic acid p-cresol m-cresol 3,4-dimethylphenol 4-ethylphenol

0.0161 + 0.0023 a 0.2271 ± 0.0367 0.6996 ± 0.1271 3.0154 ± 0.051 a 0.0034 ± 0.0006 a 0.1624 ± 0.006 a 0.0136 ± 0.0019 a 0.1821 ± 0.0012 a 0.0931 ± 0.0084 a 0.201 ± 0.0093 a nd a 0.3238 ± 0.0364 a 0.0259 ± 0.0017 0.0152 + 0.0026 a 0.9405 ± 0.1701 0.0036 ± 0.005 a 0.0939 ± 0.0047 0.705 ± 0.1259 0.5662 ± 0.0288 a nd a nd a nd a nd a 0.0029 ± 0.0007 a 0.0014 ± 0.0008 a 0.0064 ± 0.0013 a 0.0014 ± 0.0007 a 0.0805 ± 0.0097 a 0.0049 ± 0.0016 a nd a nd a nd a nd a 0.0133 ± 0.0037 a 0.2424 ± 0.0153 nd a 0.0333 ± 0.0011 a nd a 0.0215 ± 0.001 a nd a nd a nd a 0.0949 ± 0.0125 b nd a nd a nd a 0.0374 ± 0.0155 a 0.0553 ± 0.0009 a 0.0352 ± 0.0023 a 0.0121 ± 0.0021 a 0.0569 ± 0.0299 a nd a nd a nd a 0.0175 ± 0.0035 0.0377 ± 0.0093 0.0496 ± 0.0141 0.075 ± 0.0216 0.0954 ± 0.029

0.0617 + 0.0069 b 0.2218 ± 0.0201 0.7028 ± 0.0687 4.8606 ± 0.2365 b 0.0192 ± 0.0003 b 0.198 ± 0.0057 b 0.2092 ± 0.0068 c 0.3673 ± 0.0188 c 0.3909 ± 0.0343 b 0.2737 ± 0.0227 b nd a 0.5103 ± 0.0367 b 0.0209 ± 0.0022 0.0212 + 0.0007 ab 0.9524 ± 0.0978 0.0503 ± 0.0011 b 0.1112 ± 0.0122 0.71 ± 0.073 0.9922 ± 0.0952 b 0.148 ± 0.0026 b 0.1481 ± 0.0026 b 0.0146 ± 0.0006 b nd a 0.017 ± 0.001 a 0.0582 ± 0.0037 a 0.0062 ± 0.0008 a 0.0513 ± 0.0028 a 0.216 ± 0.0127 b 0.0253 ± 0.0013 b 0.0489 ± 0.0026 a 0.0423 ± 0.0059 b nd a 0.0044 ± 0.0001 b 0.0536 ± 0.002 b 0.2025 ± 0.01 0.009 ± 0.0007 a 0.0698 ± 0.0042 b 0.0115 ± 0.0014 a 0.1061 ± 0.0061 b 0.0085 + 0.0009a 0.0097 ± 0.0008 a 0.0079 ± 0.0003 b 0.1072 ± 0.0141 ab 0.0341 ± 0.0027 a 0.0608 ± 0.0065 a nd a 0.0195 ± 0.0095 a 0.0862 ± 0.007 b 0.0648 ± 0.0153 b 0.0227 ± 0.0007 b 0.0419 ± 0.0093 a 0.0086 ± 0.0023 a 0.0179 ± 0.0025 b 0.0097 ± 0.0029 a 0.0112 ± 0.002 0.0281 ± 0.0099 0.0317 ± 0.0131 0.0502 ± 0.0246 0.0616 ± 0.0317

0.1597 + 0.0105 c 0.1916 ± 0.011 0.6041 ± 0.0229 3.1398 ± 0.0566 a 0.1081 ± 0.0031 c 0.1743 ± 0.0032 a 0.1573 ± 0.0099 b 0.2345 ± 0.0121 b 0.7547 ± 0.0717 c 0.2503 ± 0.0249 ab 0.0092 ± 0.000 b 0.473 ± 0.0355 b 0.0191 ± 0.002 0.0266 + 0.0053 b 0.799 ± 0.0318 0.4717 ± 0.0027 c 0.1215 ± 0.0198 0.5934 ± 0.0209 0.8935 ± 0.1659 b 1.2497 ± 0.0867 c 0.1761 ± 0.006 c 0.1473 ± 0.007 c 0.1364 ± 0.0133 b 0.2152 ± 0.0258 b 0.5027 ± 0.0689 b 0.0857 ± 0.0136 b 0.52 ± 0.0706 b 0.5981 ± 0.0217 c 0.0578 ± 0.0015 c 0.535 ± 0.0902 b 0.0654 ± 0.0043 c 0.1318 ± 0.0226 b 0.0361 ± 0.0018 c 0.0893 ± 0.003 c 0.2215 ± 0.0849 0.0979 ± 0.0158 b 0.0365 ± 0.0071 a 0.0885 ± 0.0162 b 0.3622 ± 0.0286 c 0.0702 + 0.01b 0.1501 ± 0.029 b 0.0294 ± 0.0052 c 0.0713 ± 0.0032 a 0.1915 ± 0.0282 b 0.535 ± 0.1386 b 0.0439 ± 0.0152 b 0.0728 ± 0.004 b 0.1196 ± 0.0032 c 0.0754 ± 0.0059 b 0.0228 ± 0.0028 b 0.2072 ± 0.0779 b 0.0685 ± 0.0086 b 0.0542 ± 0.0101 c 0.0583 ± 0.0161 b 0.0226 ± 0.0076 0.0411 ± 0.007 0.0531 ± 0.0065 0.0818 ± 0.0122 0.105 ± 0.0147

LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS, std LRI,MS, std LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,tent LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,std LRI,MS,std LRI,MS,tent LRI,MS,tent LRI,MS,std

a

Volatile compounds (raw, single-roasted, and double-roasted) expressed in relative peak area to internal standard (β-ionone). Values with different letters in the same row are significant statistically (p < 0.05). bLinear retention index calculated based on DB-WAX phase. cMethods of identification: E


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Journal of Agricultural and Food Chemistry Table 3. continued


LRI (linear retention index); MS tent. (tentatively identified by MS); std (chemical standard). When only MS or LRI is available for the identification of compounds, it must be considered as an attempt of identification.

results are shown in Table 3 as relative peak areas to β-ionone. As can be seen, 39 compounds were identified in the raw sample (not roasted), while in single-roasted and doubleroasted samples, 56 and 60 compounds were identified, respectively, indicating the importance of the roasting process on the number of compounds detected. The compounds were classified according their chemical characteristics: carbonyl compounds, terpenes, alcohols, phenols, furanic compounds, pyrazines, pyrroles, lactones, acids, phenolic, and benzene derivatives. Among them, only the volatile phenolics did not show any statistical differences created by the roasting process. Clearly, the increase in carbonyl compounds, pyrazines, pyrroles, and furanic compounds was related to the roasting process since these compounds are formed by Maillard reactions.33 With regard to the pyrazines, among the 16 detected in the double-roasted samples, only five were observed in the raw samples: methylpyrazine, trimethylpyrazine, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, and 2-ethyl-3-methylpyrazine. The production of pyrazines during the roasting process was also very significant in the nuts roasted a second time; indeed, most pyrazines increased between 8 and 15 times the amount identified in single-roasted samples. Our results are in accordance with Vazquez-Araujo et al.34 and Agila et al.35 who observed the strong effect of roasting time on pyrazine production in almonds. The number and type of pyrazines for single-roasted samples detected in our study are similar to the results in the GC-O study by Aceña et al.7,36 in which pistachios were roasted at 160 °C for 20 min. However, Hojjati et al.1 observed fewer differences in pyrazine levels for Iranian pistachios, both raw and roasted at 135 °C for 20 min, detecting only two pyrazines in the roasted samples that could be attributed to the less-intense roasting process. The sensory importance of pyrazines depends on the substituents of the molecule, as they are less potent with methyl groups than with ethyl ones.33 Like the pyrazines, most of the pyrroles and furans existed in virtually undetectable amounts in raw samples, subsequently increasing in amount over the course of the roasting process.37 Thus, in raw samples, only the less volatile ones were detected, i.e., furfural and N-methylpyrrole; however, the levels of all these compounds increased with the roasting time but less dramatically than with pyrazines.34 Furfural and derivatives generally possess caramel-like, sweet, and fruity notes, while pyrroles, depending on their substituents, could possess favorable (caramel-like, sweet, corn-like) or unfavorable notes. In addition, another reaction related to the Maillard was the Strecker degradation of α-amino acids initiated by carbonyl compounds, producing an aldehyde and α-aminoketone. Although some aldehydes are highly volatile compounds and could be lost in the heating process through evaporation, our results showed an increase of the amount of aldehydes, including hexanal, pentanal, benzaldehyde, and (E)-2-pentenal, which may be due to their formation via Strecker degradation. Other compounds, such as short chain acids and lactones, were affected by roasting time since they also can be formed by Maillard reactions.38

and temperature increased. The differences in antioxidants among the three pistachio samples could be explained by their phenolic content and composition differences. Phenolic compounds with antioxidant properties are lost during the roasting of the nuts; nonetheless, the antioxidant levels of the nuts is partially restored by the development of compounds possessing more antioxidants.30 These compounds were reported as the intermediate Maillard reaction products (MRPs), as well as the resultant melanoidins, characterized by high antioxidant levels and related to the presence of reduction-type structures. Together with oxidation, condensation, and complexation of polyphenol compounds, and following suit to protein and starch hydrolysis, the Maillard reaction involves not only the reduction of sugars and amino acids but also the production of carbonyl compounds from lipid oxidation.31,32 Optimization of Purge-and-Trap Method to Obtain Pistachio Aroma Extract. The initial conditions were chosen based on the literature7,18 (60 °C for sample incubation, 300 mL/min of N2 purge flow and 60 min purging time). The results of the optimization of each parameter, purge temperature, purge time, and nitrogen flow are presented in Figure 1 (Y-axis units are expressed as relative peak area to 2-octanol). As expected, an increase in peak areas from 30 to 60 °C was observed (Figure 1A) because most of the compounds presented have high boiling points (>115 °C). Although higher temperatures would produce more sensitive extractions, 60 °C was fixed as the maximum temperature to avoid any sample changes during testing time.7 As observed in Figure 1B, the nitrogen purge flow generally increased the extraction efficiency between 100 mL/min and 500 mL/min. After 500 mL/min the extraction efficiency fluctuated slightly up and down until 1000 mL/min. In order to avoid loss of compounds or no retention on the cartridge, 500 mL/min was chosen. Finally, after the temperature and flow were fixed (60 °C and 500 mL/min N2), the effect of purging time was evaluated (Figure 1C). As can be observed, the peak areas show a steady increase until 90 min and then either remain constant or experience a slight drop-off. On the basis of these results, optimal conditions were set with temperature at 60 °C and flow at 500 mL/min for 90 min. In order to increase the sensitivity of the method in the olfactometric analysis, the dichloromethane extracts of two samples were combined, and the volume was reduced to 200 μL. Under these conditions, the error (Table 1) of the method is less than 10% for most of the compounds except for the less volatile octanoic acid (17.9%). These results showed that the method allowed aroma extraction of the volatile and semivolatile compounds of pistachio with an acceptable repeatability. In the case of compounds with a high molecular weight, high boiling point, and high/low hydrophobic constant, the method showed some variations. However, the compounds with lower volatility and higher molecular weight would most likely have negligible significance at the sensory level. Volatile Composition of Pistachios. The analysis of the aroma extracts by GC-MS and a deep study of the chromatograms has allowed tentative identification via mass spectrometry of numerous volatile compounds in the three sample types: raw, single-roasted, and double-roasted. The F


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Journal of Agricultural and Food Chemistry Table 4. Aroma-Active Regions of Raw, Single-Roasted, and Double-Roasted Pistachio Samples


FD Factora b

odor region

LRI

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

960 1185 1235 1242 1262−1269 1292 1346 1379 1390 1426 1447 1475 1516 1534 1586 1719 1891 1914 2059

odor description solvent, rancid burnt, toasted burnt, plastic chemical, solvent popcorn, toasted fatty, roasted popcorn, oily, toasted fatty, negative burnt toasted burnt, toasted popcorn, roasted popcorn roasted toasted, pharmacy toasted, burnt fatty phenolic plastic, chemical

raw

single-roasted

4

8 4 8 8 2 2 8

double-roasted

compoundc

2 4 128 2 128 2 4

n-pentanal styrene unknown an alcohol 2,6-dimethyl pyrazine; 2-ethylpyrazine an alcohol unknown unknown 2-ethyl-3,5-dimethylpyrazine 2-methyl-3,5-diethylpyrazine unknown unknown 5-methyl-1H-pyrrole-2-carbaldehyde a pyrazine 1-methyl-2-pyrrolidinone 1-(2-furanylmethyl)-1H-pyrrole unknown unknown 4-ethylphenol

16 32 2 4 8 2 2

2 2 8

a

FD factor is the highest dilution of the extract at which an odorant is determined by aroma extract dilution analysis. bLinear retention index calculated on DB-WAX capillary column. cOdor description as perceived by panelists during olfactometry.

roasted samples and 15 for double-roasted samples. Singleroasted samples did not show a very high flavor dilution factor (FD), with a maximum value at 8 for four odor-active regions: 5 (popcorn/toasted), 8 (fatty/negative), 10 (toasted), and 13 (popcorn). The compounds responsible for these aroma regions could only be identified in some cases: region 5 was the same as that detected in the raw samples; region 10 was identified as 2-methyl-3,5-diethylpyrazine and camphor; and region 13 was identified as a pyrrole (5-methyl-1H-pyrrole-2carbaldehyde). In addition, other regions at LRI 1346 (region 7) with a FD of 4, and several with FD of 2 (regions 11 and 12) which had aroma characteristics described as popcorn/toasted, are probably due to pyrazines or pyrrolic compounds, although the compounds were not identified. Two regions at LRI 1891 and 1914 (regions 17 and 18) with fatty and phenolic notes, respectively, contained unknowns. Noteworthy those aroma notes detected in single-roasted samples that were not detected in double-roasted samples (regions 8, 11, 17, and 18). This could be due to compounds present in the original samples or generated during the roasting process in the first roasting and later degraded or evaporated away in the second roasting. Another possibility is the formation of these compounds in the first roasting and their subsequent transformation into others as roasting time is longer. Vazquez-Araujo et al.34 studied the formation of toasty aroma notes in almonds and their volatile profile, observing that different roasting times are necessary to form different pyrazines and slight aroma loss at some points in the roasting process. In addition, the big differences in the odor thresholds of pyrazines is a function of their substituents (methyl or ethyl), which could significantly affect the quality and intensity of the aroma notes.33 As expected the double-roasted sample exhibited the highest flavor dilution factors. Thus, two regions presented a FD of 128: region 3 (burnt/plastic) and region 5 (popcorn/toasted). The compounds responsible for the notes in region 5 were 2,6dimethylpyrazine and 2-ethylpyrazine, which were reported as

The variation in the amount of other compounds in the raw samples, such as terpenes, benzene derivatives, and alcohols, is probably more related to a concentration effect in the sample through the loss of water and the subsequent evaporation of these compounds during roasting. Among them, it is remarkable that terpenes showed, in general, the highest values in single roasted samples. This group of compounds is the most interesting since numerous terpenes have been detected in oils of P. vera leaves39 as well as in fruit pistachio oils and other edible nuts.40 Among the nine terpene compounds detected in the present study were terpinolene, α-pinene, β-pinene, limonene, 3-carene, and camphene, which were detected in the Uzun variety of the raw Turkish pistachio,2 in the raw and roasted Iranian pistachio,1 and in the “Kerman” pistachio from California.40 Evaluation of the Aroma-Active Compounds of Pistachios. The results of the olfactometric analysis and the application of AEDA on the extracts of the three pistachio sample types (raw, single-roasted, and double-roasted) are presented in Table 4. As can be expected, the number of odoractive regions in the raw samples was much lower than in the roasted samples. Indeed, in raw samples, an odor-active region was detected only between LRI 1262 and 1269 with popcorn and toasted notes most likely associated with 2 pyrazines: 2,6dimethyl-pyrazine and 2-ethylpyrazine having FD factors of 4. Although these two compounds were not identified in the chromatograms of the raw samples (Table 3), due to the sensitivity of the method, both compounds were detected in the other two sample types. It is remarkable that these two pyrazines were not detected in olfactometric analysis by other authors in raw samples of the pistachio (P. vera),2 suggesting the probable existence of some thermic effects on the sample during harvesting and processing. Moreover, other studies undertaking chemical analyses have not detected pyrazines in raw pistachio samples (P. vera and P. terebinthus).1,17 The roasting process had a significant effect on the number of odor-active regions, with 9 regions observed for singleG


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Journal of Agricultural and Food Chemistry important contributors to roasted pistachio aroma.36 In fact, 2,6-dimethylpyrazine has a very low odor threshold of 74 ng/L in air.41 However, the significance of the 2-ethylpyrazine is expected to be lower because this compound has a higher odor threshold. On the other hand, the compounds of region 3 could not be identified. Odor region 10 (toasted) should be highlighted, with a FD of 32 and which was identified as camphor and 2-methyl-3,5-diethylpyrazine. Further, region 9 was characterized by a burnt note and a FD of 16. The last odor zone was identified as 2-ethyl-3,5-dimethylpyrazine. The pyrazine of region 9 showed a low odor threshold (0.011 ng/ l of air)41 and was detected by other authors17,36 in roasted samples of P. vera and P. terebinthus. Two regions had a FD of 8. Specifically, region 14 was comprised of roasted notes probably due to a pyrazine, and, region 19, with both a plastic note and a chemical note were attributed to 3,4-dimethylphenol and 4-ethylphenol, the latter of which has also been detected through GC-O analysis of roasted pistachios.7 Three more regions were identified with a FD of 4: region 2 had burnt and toasted notes identified as styrene; region 7 had a popcorn/ oily/toasted notes; and region 13 had a popcorn note identified as a pyrrole. The remaining five regions had a FD of 2: region 1 had solvent and rancid notes identified as n-pentanal; region 4 had chemical and solvent notes probably due to alcohol; region 13, which was also detected in roasted samples; and regions 15 and 16 with toasted notes attributable to pyrrolic compounds. Fatty Acid and Di- and Triacylglyceride Composition. Lipid content in the raw, single-roasted and double-roasted samples was 41.47 ± 0.85, 41.49 ± 0.75, and 41.96 g oil/100 g pistachio (p > 0.05), respectively. DG and TG composition of the raw, single-roasted, and double-roasted pistachios is presented in Table 5. Contents of

affected by processing. However, the results for DG CN38 (0.05 < p < 0.1) suggest that quantities were slightly reduced as a result of processing. The analysis of fatty acid methyl esters (FAME) showed three main compounds (Table 6) which were palmitic (C16− 72.50 mg/g oil for raw, 69.16 mg/g oil for single-roasted, and 73.85 mg/g oil for double-roasted), oleic (C18:1 c9−684.21 mg/g oil for raw, 691.60 mg/g oil for single-roasted, and 670.61 mg/g oil for double-roasted), and linoleic acid (C18:2 c9, c12− 186.40 mg/g oil for raw, 186.68 mg/g oil for single-roasted, and 197.93 mg/g oil for double-roasted). Stearic (C18), palmitoleic (C16:1 c9), C18:1 c11 and α-linolenic acid (C18:3 c9, c12, c15) were also present by FAME analysis, demonstrating that the overall composition is similar to that reported elsewhere for pistachios in Turkey.6 In general terms, the fatty acid composition was stable after single roasting and double roasting. However, it was observed that double-roasted samples had significantly higher concentrations of elaidic acid (C18:1 t9, 0.12 mg/g oil) compared to raw (0.06 mg/g oil) and single-roasted (0.08 mg/g oil) samples. It was also observed that levels of oleic acid were lower (p < 0.05) in double-roasted samples than in the others. The lipid composition of pistachios has a high concentration of unsaturated fatty acids. It is well-established that such compounds are prone to alteration by oxidative reactions. Thus, after drying Iranian pistachios at 70 °C, Kashani et al.43 reported concentration levels of total free fatty acids associated with hydrolysis of TG, 1,3-DG, and phospholipids. The present study’s results about DG CN38 are in line with those prior findings. In further investigations studying the effects of roasting (190 °C for 10 min), salting, and packing samples from Lebanon, it was concluded that thermal processing was the main factor leading to the production of hydroperoxides and total trans fatty acids.44 On the other hand, studies focused on the possible effects of heating of butter (20−350 °C), found isomerization of oleic in elaidic acid explained through oxidation reactions.45 Trans double bonds are more stable than cis bond when compared under the same conditions, with trans formation favored by temperature and time.46 Other authors have47,48 described that unsaturated fatty acids can be isomerized into cis/trans compounds at the intramolecular level,49 catalyzed by thiyl radicals formed from thiols groups in proteins. The present results about variations in the amounts of oleic and elaidic are in line with the aforementioned studies. However, this is the first study describing exactly which trans compounds are involved in such changes. In conclusion, the results obtained in this study showed the strong effect of roasting on the chemical composition of pistachios. The total amount of polyphenols increase with the roasting treatment; however, not all phenolic compounds demonstrated this behavior. In regard to the volatile composition and the aroma-active compounds, the effect of the roasting process on the number and intensity of the odoractive regions was clearly observed. Nevertheless, although the highest intensities were generally observed in double-roasted samples, in some cases odor regions in single-roasted samples had lower intensity than double-roasted samples. This observation can be used to optimize the roasting time in order to improve the organoleptic quality of the pistachios. Finally, the lipid analysis indicates that the roasting treatment of pistachio nuts reduced the concentration of DG CN38 and increased the amount of elaidic acid due to the isomerization of oleic acid by oxidative reactions.

Table 5. Total Contents and Molecular Species Composition (%) of Di- and Triacylglycerides in the Assayed Pistachio Samplesa raw CN36 CN38 total DG CN50 CN52 CN54 total TG

0.50 3.11 3.61 2.07 19.45 74.87 96.39

± ± ± ± ± ± ±

single-roasted 0.01 0.15 0.16 0.04 0.19 0.02 0.16

0.46 3.05 3.51 1.97 19.82 74.71 96.49

± ± ± ± ± ± ±

0.05 0.15 0.20 0.39 0.83 1.32 0.20

double-roasted

p

± ± ± ± ± ± ±

0.43 0.09 0.39 0.56 0.25 0.67 0.39

0.48 2.94 3.42 2.10 19.88 74.60 96.58

0.02 0.10 0.12 0.04 0.24 0.31 0.12

a

DG: diacylglycerides; TG: triacylglycerides; p: significance level (p < 0.05).

TG were 96.39 g/100 oil for raw samples, 96.49 g/100 oil for single-roasted samples, and 96.58 g/100 oil for double-roasted samples. In all of the samples assayed, TG CN54 was the main compound (74.87 g/100 oil for raw, 74.71 g/100 oil for singleroasted, and 74.69 g/100 oil for double-roasted), while TG CN52 and CN50 were lower. Two compounds were detected by DG composition, CN36 (0.50 g/100 oil for raw; 0.46 g/100 oil for single-roasted, and 0.48 g/100 oil for double-roasted) and DG CN38 (3.11 g/100 oil for raw, 3.05 g/100 oil for single-roasted, 2.94 g/100 oil for double-roasted). Holčapek et al.42 reported the TG and DG composition of pistachio oil as equivalent carbon number ranging from 40 to 50 and 20 to 34, respectively. However, if TG and DG are calculated as CN, results are similar to those found in the current research study. The data revealed that TG in the assayed samples was not H


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Table 6. Fatty Acid Composition (mg/g oil) in the Assayed Pistachio Samplesa C14 C15 C16 C16:1 t C16:1 c9 C17 C17:1 C18 C18:1 t9 C18:1 t10 C18:1 c9 C18:1 c11 C18:2 c9, t12 C18:2 c9, c12 C20 C18:3 c9, c12, c15 C20:1 c11 C20:1 c13 C22 C23 C24 SFA MUFA PUFA

raw

single-roasted

double-roasted

p

0.78 ± 0.05 0.06 ± 0.01 72.50 ± 2.22 0.47 ± 0.01 4.61 ± 0.14 0.34 ± 0.01 0.68 ± 0.03 16.91 ± 0.23 0.06 ± 0.03 a 0.24 ± 0.01 684.21 ± 1.65 a 23.14 ± 0.38 0.22 ± 0.04 186.40 ± 0.71 2.82 ± 0.13 1.75 ± 0.04 0.22 ± 0.03 2.63 ± 0.16 1.26 ± 0.10 0.27 ± 0.02 0.42 ± 0.03 95.35 ± 1.94 716.28 ± 1.29 188.36 ± 0.72

0.73 ± 0.01 0.05 ± 0.01 69.16 ± 1.98 0.47 ± 0.04 4.34 ± 0.19 0.32 ± 0.03 0.65 ± 0.03 17.35 ± 0.96 0.08 ± 0.03 a 0.23 ± 0.01 691.60 ± 8.55 a 22.87 ± 0.61 0.22 ± 0.05 186.68 ± 8.66 3.00 ± 0.23 1.73 ± 0.06 0.24 ± 0.02 2.90 ± 0.07 1.37 ± 0.17 0.29 ± 0.01 0.48 ± 0.06 92.75 ± 3.37 718.61 ± 8.46 188.64 ± 8.73

0.80 ± 0.04 0.06 ± 0.01 73.85 ± 2.16 0.48 ± 0.03 4.72 ± 0.16 0.35 ± 0.01 0.68 ± 0.02 17.67 ± 0.22 0.12 ± 0.03 b 0.24 ± 0.02 670.61 ± 0.47 b 22.76 ± 0.25 0.24 ± 0.01 197.93 ± 1.46 2.93 ± 0.13 1.73 ± 0.05 0.22 ± 0.03 2.62 ± 0.14 1.27 ± 0.11 0.26 ± 0.04 0.42 ± 0.04 97.61 ± 1.70 702.48 ± 0.28 199.91 ± 1.45

0.19 0.31 0.08 0.86 0.07 0.23 0.28 0.34 0.00 0.68 0.02 0.57 0.71 0.05 0.46 0.86 0.54 0.07 0.57 0.39 0.27 0.13 0.01 0.054

a

p: significance level. t: trans double bond; c: cis double bond. SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids. Different letters in a row for significant effect of processing (p < 0.05).

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(7) Aceña, L.; Vera, L.; Guasch, J.; Busto, O.; Mestres, M. Determination of roasted pistachio (Pistacia vera L.) key odorants by headspace solid-phase microextraction and gas chromatographyolfactometry. J. Agric. Food Chem. 2011, 59, 2518−2523. (8) Tomaino, A.; Martorana, M.; Arcoraci, T.; Monteleone, D.; Giovinazzo, C.; Saija, A. Antioxidant activity and phenolic profile of pistachio (Pistacia vera L., variety Bronte) seeds and skins. Biochimie 2010, 92, 1115−1122. (9) Kucukoner, E.; Yurt, B. Some chemical characteristics of Pistacia vera varieties produces in Turkey. Eur. Food Res. Technol. 2003, 217, 308−310. (10) Maskan, M.; Karatas, S. Storage stability of whole-split pistachio nuts (Pistachia vera L.) at various conditions. Food Chem. 1999, 66, 227−233. (11) Tsantili, E.; Konstantinidis, K.; Christopoulos, M. V.; Roussos, P. A. Total phenolics and flavonoids and total antioxidant capacity in pistachio (Pistachia vera L.) nuts in relation to cultivars and storage conditions. Sci. Hortic. 2011, 129, 694−701. (12) Raei, M.; Mortazavi, A.; Pourazarang, H. Effects of Packaging Materials, Modified Atmospheric Conditions, and Storage Temperature on Physicochemical Properties of Roasted Pistachio Nut. Food Anal. Method. 2010, 3, 129−132. (13) Panahi, B.; Khezri, M. Effect of harvesting time on nut quality of pistachio (Pistacia vera L.) cultivars. Sci. Hortic. 2011, 129, 730−734. (14) Shakerardekani, A.; Karim, R.; Ghazali, H. M.; Chin, N. L. Effect of roasting conditions on hardness, moisture content and colour of pistachio kernels. Int. Food Res. J. 2011, 18, 723−729, DOI: 10.2139/ ssrn.1799189. (15) Nikzadeh, V.; Sedaghat, N. Physical and Sensory Changes in Pistachio Nuts as Affected by Roasting Temperature and Storage. Am.Eurasian J. Agric. Environ. Sci. 2008, 4, 478−483. (16) Kashant, K.; Guy Valadon, L. R. Effect of salting and toasting on the carbohydrates and proteins of Iranian pistachio kernels. J. Food Technol. 1984, 19, 247−253. (17) Gogus, F.; Ozel, M. Z.; Kocak, D.; Hamilton, J. F.; Lewis, A. C. Analysis of roasted and unroasted Pistacia terebinthus volatiles using

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; phone: + (90)-322-3386173; fax: + (90) 322 338 66 14). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS J.J.R.B. acknowledges the postdoctoral fellowship for the visiting scientists program, The Scientific and Technological Research Council of Turkey (TUBITAK-BIDEB, no: 2221). We thank Bethany J. Hausch from University of Illinois (UIUC) for proofreading the manuscript.

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