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The effects of production methods on the color characteristics, capsaicinoid
content and antioxidant capacity of pepper spices (C. annuum L.)
Article in Food Chemistry · March 2021 DOI: 10.1016/j.foodchem.2020.128184 CITATIONS 0 READS 76 3 authors:
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Food Chemistry
journal homepage:www.elsevier.com/locate/foodchem
The effects of production methods on the color characteristics, capsaicinoid
content and antioxidant capacity of pepper spices (C. annuum L.)
Aziz Korkmaz
a,b,⁎, Ahmet Ferit Atasoy
c,d, Ali Adnan Hayaloglu
eaFaculty of Health Science, Department of Nutrition and Dietetics, Mardin Artuklu University, 47200 Mardin, Turkey bCentral Laboratory, Mardin Artuklu University, 47200 Mardin, Turkey
cFaculty of Engineering, Department of Food Engineering, Harran University, 63010 Sanlıurfa, Turkey dPepper and Isot Research and Application Center, Harran University, 63010 Sanlıurfa, Turkey eFaculty of Engineering, Department of Food Engineering, Inonu University, 44000 Malatya, Turkey
A R T I C L E I N F O
Keywords:
Red pepper
Isot pepper
Red pepper flakes
Carotenoids and capsaicinoids Enzymatic browning Antioxidant capacity
A B S T R A C T
The effects of production methods for red pepper flakes (RPF) and traditional (TRI) and industrial (INI) isot spices were evaluated with respect to the carotenoid and capsaicinoid contents, extractable color (ASTA color), surface color parameters, nonenzymatic browning (NEB), and the DPPH free radical-scavenging capacity of fresh red Capsicum (FRC). The measured characteristics were significantly affected by the processing methods used. RPF exhibited the highest antioxidant activity and best color quality in terms of carotenoid content, which was the highest; ASTA value; surface color intensity; and NEB, which was the lowest. In contrast, INI-processing methods resulted in poor color quality, causing the maximum increase in NEB. The concentration of capsaicinoid increased at the end of TRI processing, whereas it decreased in the two other methods. These results suggest that the traditional production method for isots prevents excessive destruction of their color attributes and con-tributes to the desirable characteristic browning.
1. Introduction
Dried and ground forms of red pepper varieties (Capsicum annum L.) are among the most widely used spices in different food products and in many cuisines worldwide. The popularity of this spice is mainly derived from its sensory properties of color, pungency, and flavor. Moreover, because of their antioxidant components, the fruits of Capsicum genus plants have become significant components of pharmaceuticals, such as vitamins, phenolics, flavonoids, carotenoids, and capsaicinoids (Ananthan, Subhash, & Longvah, 2018).
Color is as an important attribute for determining the commercial value of pepper spices. The color quality of red pepper powder is generally evaluated by carotenoid content, ASTA (American Spice Trade Association) value, and CIE L*a*b* color parameters. The char-acteristic color of ripened Capsicum is derived from pigments called carotenoids with yellow-orange and red tones. The red color of pepper is derived from capsanthin and capsorubin, while the yellow-orange color is mostly derived from β-carotene, zeaxanthin, lutein, β-cryp-toxanthin, violaxanthin and/or capsolutein (Topuz, Dincer, Özdemir, Feng, & Kushad, 2011). The amounts of these pigments are affected by postharvest processes, especially drying, and generally decreases
because of oxidative degradation. The ASTA value is based on the measurement of the extracted color and indicates the total carotenoid content (Vega-Gálvez et al., 2009). Additionally, the CIE L*a*b* is a color scale system that measures surface color in terms of L* (white-ness/brightness), a* (redness/greenness) and b* (yellowness/blueness) parameters. Another color feature of dried pepper powder is the browning index, a measure of color loss. This parameter is mainly in-fluenced by drying conditions such as temperature, humidity, and time (Lee, Chung, Kim, & Yam, 1991; Topuz, Feng, & Kushad, 2009).
Pungency is a specific sensorial property of Capsicum varieties and is attributed to capsaicinoids. Red peppers can contain 12 or more dif-ferent capsaicinoids, whose amounts differ primarily according to variety. Among these types, capsaicin and dihydrocapsaicin are sponsible for the majority (~90%) of spice pungency. It has been re-ported that these compounds have beneficial effects on health such as anti-inflammatory and antitumor activity, cardiovascular disease pre-vention, plasma lipid reduction, and weight reduction (Topuz & Ozdemir, 2007). The capsaicinoid content is influenced by drying method (Yaldiz, Ozguven, & Sekeroglu, 2010).
Red pepper spices are generally obtained by drying and grinding mature fresh fruits. However, there are other spices for which the
https://doi.org/10.1016/j.foodchem.2020.128184
Received 25 May 2020; Received in revised form 19 September 2020; Accepted 22 September 2020
⁎Corresponding author at: Health College, Department of Nutrition and Dietetics, Mardin Artuklu University, 47200 Mardin, Turkey.
E-mail address:azizkorkmaz@artuklu.edu.tr(A. Korkmaz).
Food Chemistry 341 (2021) 128184
Available online 05 October 2020
0308-8146/ © 2020 Elsevier Ltd. All rights reserved.
production processes differ, such as isot (a Turkish spice) and paprika in Spain. Isot is produced by a traditional method from certain local pepper varieties in the Sanliurfa Province of southeastern Turkey. In this method, semi-sun-dried peppers are placed in polyethylene bags and exposed to the sun for 4–7 days. The main purpose of this opera-tion, called terletme (similar to sweating), changes the pepper color to a typical blackish red. This method is time- and labor-consuming, re-quiring a total of 6–10 days. In recent years, isot has been produced with an industrial method as an alternative to traditional production. During industrial production, the pepper color-changing process is carried out using a distinct heat treatment requiring 36–48 h. The heat in this process is produced by the friction of pieces during the helical transfer of the pepper, with temperatures increasing to 70–80 °C (Korkmaz, Atasoy, & Hayaloglu, 2020).
Previous studies have shown that production conditions affect some physicochemical and biochemical characteristics of dried pepper spices (Maurya, Gothandam, Ranjan, Shakya, & Pareek, 2018). These effects are predominantly determined by drying conditions, including tem-perature, time, humidity and light.Topuz and Ozdemir (2003)found that the losses in red pigments in oven-dried (~70 °C) pepper flakes were greater than those in sun-dried peppers, while the capsaicinoid content was higher in the oven-dried peppers.Vega-Gálvez et al. (2009)
demonstrated that a higher drying temperature causes a decrease in ASTA and an increase in nonenzymatic browning. To the best of our knowledge, there is no extensive study on the quality of isot spices. Hence, the purpose of this study is to investigate the relationships be-tween the production methods and the color properties, capsaicinoid content and antioxidant capacity of isot spices. Additionally, isot is compared with red pepper flakes in terms of the properties of interest. 2. Materials and methods
2.1. Plant material
The pepper fruits (Capsicum annuum L. cv. Inan3363, a ‘‘Urfa’’- type pepper) used in this study were harvested from the Experimental Station of the GAP Agricultural Research Institute, Sanlıurfa, Turkey. Approximately 200 kg of fully red ripe fruits were freshly harvested. They were transferred immediately to the production house and pro-cessed within the same day. At the same time, one kg of fresh pepper pods was randomly separated and immediately stored at −20 °C until analysis.
2.2. Standards and chemicals
Capsanthin (≥95%), β-cryptoxanthin (≥97%), zeaxanthin (≥95%), β-carotene (≥93%), capsaicin (≥99%), dihydrocapsaicin (≥97%), 2,2-diphenyl-1-picrylhydrazyl (DPPH), diethyl ether, Na2SO4
(anhydrous), KOH and acetic acid were purchased from Sigma-Aldrich (Taufkirchen, Germany). Capsorubin (≥95%), violaxanthin (≥95%) and ß-apo-8ʹ-carotenal (≥95%) were purchased from CaroteNature (Lupsingen, Switzerland). Acetone, acetonitrile (HPLC grade), me-thanol, NaCl and anhydrous Na2SO4(analytical grade) were supplied
by Merck (Darmstadt, Germany). Purified water was obtained using a Millipore Simplicity Water Purification System (Bedford, MA, USA). 2.3. Production of samples
The dried pepper samples were produced using the method of
Korkmaz et al. (2020). First, the seeds and stems of the peppers were removed and longitudinally hand-separated into 2–3 pieces after washing with water. These slices were divided into three groups for different production methods. The details of the different production methods are shown inFig. S1. Each production process was performed in triplicate.
2.3.1. Red pepper flakes (RPF)
The slices in the first group were spread out in the sun on a clean concrete floor. The drying process was continued for 96 h until the moisture content was < 15% (w/w) as found in Turkish commercial red pepper flakes. Air temperature was measured three times (00.00 a.m.; 06.00 a.m.; and 12.30p.m.) during the drying process. The average day and night temperatures were 33 ± 1 and 21 ± 1 °C, respectively. After drying, the slices were ground using a mill into flakes 2–3 mm in size.
2.3.2. Industrial isot (INI)
The second group of slices were sun-dried for 96 h, ground to 1–3 mm, and tempered to 25% moisture content. Then, the flakes were heated to 85 °C by friction as they were transferred into an insulated wooden cabinet using a pilot-scale helical conveyor (specifically de-signed). These heated flakes were maintained in the cabinet at 85 °C for 36 h. Thereafter, the flakes were removed from the cabinet and spread for ~ 2 h until the moisture content was lower than 15%.
2.3.3. Traditional isot (TRI)
The third group of pepper slices was sun-dried for 48 h to ap-proximately 30% moisture content. Then, 3,000 mL of brine (4 g/100 g) was sprinkled onto these semidried slices (7.47 kg) as necessary for the sweating process called terletme. During this process, the slices were placed into polyethylene bags that were then thinly spread on a con-crete floor in sunlight. The inside temperatures of the bags were de-termined using a thermocouple thermometer (type 421305, Extech, Waltham, MA, USA), measured three times (00.00 a.m.; 06.00 a.m.; and 12.30p.m.) each day during the terletme process. The average day and night temperatures inside the bags were 50 ± 1 and 23 ± 1 °C, re-spectively, during this stage. The bags were turned daily, the slices removed from the bags and covered with a cotton cloth at night. After six days, the slices were sun dried again for 24 h until the moisture was lower than 15%. Finally, they were ground by a mill to approximately 1–3 mm. The particle size of the three milled samples was determined using four mesh sieves with hole sizes of 3.15 mm, 2.80 mm, 1 mm, and 0.85 mm (UTEST, Ankara, Turkey).
2.4. Sampling
Fresh peppers with the seeds and peduncles removed were crushed into a fine puree for 10 s in a low-speed laboratory-type blender (Waring 8011; Torrington, CT, U.S.A.). RPF, INI and TRI were micro-nized for 30 s in a high-speed spice grinder (Premier PRG 259; Istanbul, Turkey) to 100–300 µm. The four prepared samples were stored at −18 °C before analyses. All analyses were performed in triplicate for each sample.
2.5. Analysis of the color attributes 2.5.1. Carotenoid analyses
The carotenoids were extracted according to the method of
Mínguez-Mosquera and Hornero-Mendez (1993)with minor modifica-tions. One gram of sample (for the fresh sample, 10 g of puree) was extracted with 50 mL of acetone using a homogenizer (Ultra-Turrax T25 Basic, IKA, Staufen, Germany) at 15,000 rpm for 30 s. The extraction was repeated until colorless. All extracts were combined, and the acetone evaporated at 33 °C and 210 mmHg in a vacuum with a rotary evaporator (Heidolph, Schwabach, Germany) until the volume was re-duced to 50 mL. The extract was transferred to a separating funnel and shaken with 100 mL of diethyl ether. A 20 µL aliquot of ß-apo-8ʹ-car-otenal (1 mg/1 mL acetone) was added to the extract as the internal standard. Then, 100 mL of NaCl water solution (10%) was added, and the phases were separated. The ether phase containing pigments was washed with 100 mL anhydrous Na2SO4solution (2%) to remove the
remaining water. The ether phase was saponified with 50 mL of a 10%
A. Korkmaz, et al. Food Chemistry 341 (2021) 128184
KOH solution in methanol and maintained at room temperature for 1 h with shaking in the dark. Then, the solution was separated with a 10% NaCl water solution, and the aqueous phase was removed. The organic phase was washed repeatedly with distilled water until neutral, treated several times with anhydrous Na2SO4(2%), dried in a rotary (32 °C and
204 mm Hg) and passed through nitrogen gas to eliminate the water residue. The obtained pigments were dissolved in an amber glass vial with 5 mL of acetone and stored in a freezer (Arcelik 2595, Eskisehir, Turkey) at −20 °C until HPLC analysis. One milliliter of this dilution was passed through a 0.45 µm membrane filter (Millipore) before in-jection.
Carotenoid analyses were performed using an HPLC system (Shimadzu LC-20AD) equipped with a diode array detector (SPD-M20A). The column was a reverse-phase Inertsil ODS-3 (250 mm × 4.6 mm, 5 μm). The separations were achieved using an acetone–water binary gradient elution as follows: 0–5 min, 75% acetone; 5–10 min, 85% acetone; 10–15 min, 95% acetone; 15–20 min, 100% acetone; 20–23 min, 75% acetone. The flow rate was 1.25 mL/ min, the injection volume was 20 µL, and the detection wavelength was set at 450 nm. The injection was performed in duplicate for each sample. The identification of capsanthin, zeaxanthin, carotene, β-cryptoxanthin, ß-apo-8ʹ-carotenal, capsorubin, and violaxanthin was conducted by comparing the retention times of their commercial stan-dards. These pigments were quantified by using calibration curves prepared with the standards based on the internal standard. A few unidentified peaks were also evaluated as β-carotene equivalent to calculate the estimated amount of total carotenoid (Hervert-Hernández, Sáyago-Ayerdi, & Goñi, 2010).
2.5.2. Extractable color (ASTA) measurement
ASTA values were determined according to the method re-commended by theAOAC (2002)with a slight modification. A 0.1 g ( ± 0.001) sample was placed into a 100 mL volumetric flask. Acetone was added to the mark, and the flask was shaken. The solution was left in the dark for 16 h. Then, the absorbance of an aliquot of this extract was measured in duplicate at 460 nm against acetone using a spectro-photometer (Biochrom Libra S70, Cambridge, UK). The ASTA values were calculated as follows:
= w
ASTA Absorbance 16.4 If 1
where Ifis the correction factor of the spectrophotometer, calculated by dividing the theoretical absorbance (0.600) by the true absorbance of a standard solution of potassium dichromate (0.001 M) and ammonium and cobalt sulfate (0.09 M) in 1.8 M H2SO4at 460 nm, and w is the
sample weight based on the dry matter.
In addition, the extractable red and yellow color ratio was calcu-lated by using the ratio of absorbance of acetone extract used in ASTA analysis at 470 nm to 455 nm (Topuz et al., 2009).
2.5.3. Nonenzymatic browning (NEB) index measurement
The NEB was determined according to the method used byTopuz et al. (2009). Briefly, 0.1 ( ± 0.001) g of sample was added to 50 mL of pure water and agitated at 25 °C and 140 rpm for 2 h. Then, the mixture was centrifuged at 3,000 g for 8 min. The supernatant was filtered with a PTFE filter (0.45 µm). The absorbance of the filtrate was measured at 420 nm with a spectrophotometer (Biochrom Libra S70, Cambridge, UK). The absorbance was converted to a dry weight of 0.1 g by com-pensating for the moisture content of the samples.
2.5.4. Determination of surface color
The surface color of spices was measured using a colorimeter (Minolta CR-5, Tokyo, Japan), reading values of L*, a* and b* on three different points of the surface for each sample. Furthermore, the in-strument enabled the determination of the chroma (C) and hue angle (ho), which can be obtained from the following equations:
= +
C (a2 b2 0.5) =
ho tan 1( / )b a 2.6. Capsaicinoid analyses
The extraction of the capsaicinoids was carried out according to the method ofContreras-Padilla and Yahia (1998)with some modifications. A 0.5 g sample was mixed with 30 mL of acetonitrile, homogenized using an Ultra-Turrax homogenizer at 2,000 rpm for 30 s and main-tained at 80 °C for 4 h with periodic shaking every 30 min. The sus-pension was maintained at room temperature (30 min) to cool and al-lowed to settle. The supernatant was filtered through a 0.45 µm PTFE filter and injected into the HPLC.
Capsaicinoids were analyzed using a Shimadzu HPLC (Shimadzu LC-20AD) system coupled to a fluorescence detector (RF-10AXL) and a Luna C18 column (C18 100A, Phenomenex; 250 × 4.60 mm, 5 µm). The separation conditions were applied as described byTopuz et al. (2011)at room temperature. The mobile phase was a mixture of acet-onitrile:water:acetic acid (100:100:1) at a flow rate of 1.2 mL/min. The injection volume was 10 µL. The detector was set at 280 nm excitation and 320 nm emission. Identification and quantification were performed with capsaicin and dihydrocapsaicin as external standards. Since there are no analytical standards for nordihydrocapsaicin and homo-capsaicin, these compounds were identified based on their chromato-graphic behaviors on a C18 column, as determined previously (Giuffrida et al., 2014; Ornelas-Paz et al., 2010). Therefore, the quan-tifications of these capsaicinoids were performed using the calibration curves of capsaicin. In addition, the Scoville Heat Units of samples were determined from concentrations of capsaicinoids using the conversion factors for each compound presented by Todd, Bensinger, and Biftu (1977).
2.7. Antioxidant capacity analysis
The antioxidant activity was determined using 2,2-diphenyl-1-pi-crylhydrazyl (DPPH) based on the method used byArslan and Ozcan (2011)with slight modifications. One gram of sample was extracted in 25 mL of methanol using the Ultra-Turrax homogenizer at 2200 rpm for 10 s. The extraction was repeated two times to ensure efficacy. Then, 15 µL of the extract was mixed with 285 µL of 0.025 M DPPH in me-thanol, filtrated using a 0.45 µm PTFE filter and incubated at room temperature in the dark for 30 min. The absorbance of the solutions was read at 517 nm against a blank without DPPH using a spectro-photometer (Biochrom Libra S70, Cambridge, UK). The total anti-oxidant activity was expressed as the percentage of inhibition of DPPH and calculated as follows:
= ×
Antioxidant activity(%) 1 Abs
Abs 100
sample control
2.8. Statistical analysis
The data are expressed as the means ± standard deviation (SD). The significance of differences between spices was tested using one-way analysis of variance (ANOVA) followed by Duncan’s multi comparison test (P < 0.05). All statistical analyses were performed with the SPSS (version 16.0, Chicago, IL, U.S.A.) software package.
3. Results and discussion
3.1. The color properties of the samples 3.1.1. Carotenoids
quantified carotenoids in FRC decreased (P < 0.05) after the pro-duction of spices. Thus, the initial total content of carotenoids de-creased in the production of the RPF, TRI and INI by 28.6%, 45.5% and 62.6%, respectively. For the TRI and RPF, this may be explained by the oxidation of carotenoids during sun drying and the terletme process (Mínguez-Mosquera, Pérez-Gálvez, & Garrido-Fernández, 2000), while the greater decrease in INI may be mainly due to the heat treatment, which can also cause the thermal degradation of carotenoids (Daood, Kapitány, Biacs, & Albrecht, 2006).Minguez-Mosquera, Jaren-Galan, and Garrido-Fernandez (1994) found a 65% decrease in total car-otenoid content in red pepper after oven drying.Topuz and Ozdemir (2003)reported an approximately 81.11% reduction in the total car-otenoid concentration in red pepper after sun drying (5–7 days). An-other study on the dehydration of fresh mature pepper for producing paprika reported loss rates of total carotenoid amounts between 10% and 24% (Gallardo-Guerrero, Pérez-Gálvez, Aranda, Mínguez-Mosquera, & Hornero-Méndez, 2010).
On the other hand, the changes in carotenoid levels during pro-duction were determined, and interestingly, an increasing trend in total carotenoid content (Table S1) was observed during the terletme process, which was applied for TRI production. This is probably due to the fa-vorable conditions, such as temperature, time and moisture or water activity (aw), that sustain pigment synthesis after harvesting (
Gallardo-Guerrero et al., 2010; Topuz et al., 2011). Additionally, a significant correlation during the production of TRI was found between the total carotenoid content and aw(Table S2) (Pearson’s coefficient = 0.746, P < 0.01). The levels of carotenoids in all samples were sorted in decreasing order: capsanthin > zeaxanthin > carotene > β-cryptoxanthin > capsorubin > violaxanthin. Capsanthin, the major pigment (red), constituted 48.61%, 43.50% and 49.01% of the total carotenoid content in the TRI, INI and RPF, respectively. Violaxanthin, the minor carotenoid, accounted for 3.19%, 3.92% and 2.63% of the total carotenoid content in the TRI, INI and RPF, respectively. In gen-eral, the profile of the carotenoids in the samples was similar to that shown in previous results based on various forms of dried peppers (Topuz & Ozdemir, 2007; Topuz et al., 2011). All carotenoids in the FRC exhibited different levels of loss for each sample after production (P < 0.05). The retention rate of capsanthin (79%) in the RPF was higher than that in the yellow fractions (65%) (Fig. 1). This can be explained by the higher oxidative stability of capsanthin exposed to the sun. Additionally, certain yellow carotenoids were thought to be con-verted to red carotenoids, increasing the level of difference between these fractions (Minguez-Mosquera et al., 1994). However, more yellow pigments than red pigments were retained during the INI production process. This result may be related to the higher thermal stabilities of the main yellow carotenoids, particularly β-cryptoxanthin (Daood et al., 2006). Table 1 Carotenoid contents of FRC, TRI, INI and RPF (mg kg −1 dw). Sample Capsanthin Zexsanthin β-Carotene β-Cryptoxanthin Capsorubin Violaxanthin Unidentified Red fractions Yellow fractions Total carotenoids FRC 971.61 ± 10.91 a 319.67 ± 3.9 a 228.04 ± 4.57 a 149.45 ± 5.23 a 128.30 ± 0.49 a 112.12 ± 0.20 a 275.67 ± 8.86 a 1099 ± 5.67 a 809.28 ± 3.48 a 2184.49 ± 34.10 a TRI 579.12 ± 0.87 c 171.84 ± 1.37 c 125.74 ± 0.56 c 103.93 ± 0.83 c 79.65 ± 0.64 c 38.61 ± 0.32 c 92.83 ± 1.41 c 658.77 ± 0.75 c 440.12 ± 0.77 c 1191.74 ± 3.14 c INI 355.25 ± 5.33 d 147.19 ± 2.54 d 98.66 ± 0.82 d 77.66 ± 1.24 d 46.93 ± 0.69 d 32.97 ± 0.50 d 57.94 ± 0.69 d 401.25 ± 2.99 d 356.48 ± 1.28 d 816.60 ± 11.80 d RPF 764.00 ± 11.51 b 228.80 ± 6.25 b 142.20 ± 2.41 b 115.30 ± 0.14 b 95.60 ± 2.53 b 41.50 ± 0.42 b 171.94 ± 7.57 b 859.60 ± 7.02 b 527.80 ± 2.31 b 1559.30 ± 14.58 b FRC: Fresh Red Capsicum ;TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes. a-d Different lowercase letters in same column indicate significant difference among samples (P < 0.05). 0 15 30 45 60 75 90
Capt Zex β-Car β-Cry Capb Vio Red Yellow
Ret ent io n o f ca ro teno ids (%) TRI INI RPF
Fig. 1. Retention of carotenoids in TRI, INI and RPF. FRC: Fresh Red Capsicum;
TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes.
A. Korkmaz, et al. Food Chemistry 341 (2021) 128184
3.1.2. Extractable color
The ASTA values of the samples are illustrated in Fig. 2a. This parameter was significantly affected by production method (P < 0.05) and measured as 158.30 ± 0.87, 147.50 ± 0.48, 139.11 ± 0.15 and 124.38 ± 0.45 for the FRC, RPF, TRI and INI, respectively. It was reported that the ASTA values of 52 different pepper spices selected based on different origins ranged between 101 ± 28.3–140 ± 35.4 (Molnár et al., 2018). ASTA color can be used as an indicator of total carotenoid content for the quality assessment of pepper spices (Mínguez-Mosquera & Pérez-Gálvez, 1998). There was a good correla-tion between the ASTA values and the total carotenoid levels of the samples (Pearson’s coefficient = 0.976, P < 0.01). Pérez-Gálvez, Mínguez-Mosquera, Garrido-Fernández, Lozano-Ruiz, and Montero-de-Espinosa (2004)also reported a high correlation (r = 0.992) between the ASTA units and the total carotenoids of paprika during storage, whereas Pérez-Gálvez, Hornero-Méndez, and Mínguez-Mosquera (2009)found a low correlation.
The R/Y pigment ratio of the fresh pepper (1.033 ± 0.008) de-creased after spice production (P < 0.05). INI had the lowest R/Y ratio, 0.950 ± 0.002, possibly because, as mentioned above, their red pigments have lower thermal stability. The R/Y ratios of the TRI and RPF were found to be similar, with values of 0.977 ± 0.002 for the TRI and 0.978 ± 0.001 for the RPF (P > 0.05) (Fig. 2a). The R/Y ratios of similar ranges have been found by other researchers (Topuz et al., 2009).
3.1.3. Nonenzymatic browning index
Although browning is considered a color deterioration for pepper
spices, darkening to a certain extent is desired in the production of isot. This change in color is used as an index of the characteristic flavor of the spice. In practice, the terletme process for TRI and the heat treatment for INI are applied for the purpose of controlled the browning of these spices. The NEB values of the TRI, INI and RPF were 0.261 ± 0.008, 0.713 ± 0.014 and 0.144 ± 0.005, respectively (Fig. 2b). The NEB value of the RPF was similar to that of a previous study (Cao et al., 2016), which reported a similar drying time for the powder of sun-dehydrated Capsicum. It was also reported that extended drying time notably led to an increase in the browning rate of dried peppers (Yang et al., 2018).
The higher NEB of the TRI compared to that of the RPF was likely based on the terletme. This process not only has a higher application temperature and awbut also an extended drying time (Lee et al., 1991;
Rhim & Hong, 2011; Yang et al., 2018).Lee et al. (1991)also reported the highest browning rate in dried pepper for the 0.5–0.7 awrange and 40 °C temperature, similar to terletme conditions. The NEB of the INI was 2.73-fold greater than that of the TRI. This difference was more likely based primarily on the higher temperature (Yang et al., 2018). NEB in pepper is the product of Maillard reactions between sugars and amino acids (Lee et al., 1991). Moreover, the ASTA and NEB values of the samples were strongly correlated (Pearson’s coefficient = −0.961, P < 0.01). This result indicates greater browning in pepper spices and greater color-related pigment degradation (Lee & Kim, 1989). 3.1.4. Surface color
The values for surface colors of the samples are shown inFig. 3. These values, except for hue angle (ho), were significantly affected by
production method (P < 0.05). The L* (lightness) value of the fresh sample was lower than that of the spices, probably due to losses in carotenoids or an increase in the content of bright pigments during production, causing a lighter color (Topuz et al., 2009). The RPF had the highest L*, a* (redness) and b* (yellowness) values, whereas the INI had the lowest values for these parameters. The greater decreases in the lightness of the INI, meaning a darker color, can be attributed to the higher concentration of brown pigment formed by Maillard reactions (Rhim & Hong, 2011). The pronounced decreases in a* (60.35%) and b* (36.13%) of the INI can be explained by further degradation in car-otenoids of this sample than that of the others (Yang et al., 2018). The higher a* and b* values of the TRI and RPF compared to those of the fresh pepper can be related to an increase in carotenoid concentrations due to a decrease in moisture content (Shirkole & Sutar, 2018). The C (chroma) value, which more precisely represents the stability in color, exhibited similar changes to those in a* and b* after production.
Furthermore, the Pearson test showed that the surface color para-meters of the spices were significantly correlated with the total d b a c 0.00 0.15 0.30 0.45 0.60 0.75 FRC TRI INI RPF NE B
b)
a)
A C D B a b c b 0.90 0.95 1.00 1.05 1.10 50 70 90 110 130 150 170 FRC TRI INI RPF R/Y ASTA ASTA R/YFig. 2. ASTA values and R/Y ratio (a), and NEB (b) of FRC, TRI, INI and RPF.
FRC: Fresh Red Capsicum; TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes. a-c and A-CDifferent lowercase and uppercase letters indicate
significant difference among samples (P < 0.05).
d b c c b b b b b a c c d d a a a a a a 0 10 20 30 40 50 60 L* a* b* C* h* Colour parameters FRC TRI INI RPF
Fig. 3. Surface color parameters of FRC, TRI, INI and RPF. FRC: Fresh Red Capsicum; TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes.a-c
Different lowercase letters indicate significant difference among samples (P < 0.05).
carotenoid content, ASTA and NEB values (Table S3). These values (except ho) were strongly positively correlated with both ASTA and
total carotenoids of the spices (P < 0.01) and were highly negatively correlated with NEB values. These relationships demonstrate that the surface color of red pepper powders produced by different methods can be used to compare the losses in their color quality caused by car-otenoid degradation and browning. Yang et al. (2018)also observed good correlations between the surface color values and both the natural pigment content and NEB values. However,Nieto-Sandoval, Fernandez-Lopez, Almela, and Munoz (1999)reported a weak correlation between ASTA and CIELAB parameters.
3.2. The capsaicinoids in samples
The capsaicinoid content of the samples is given inTable 2. The sum of capsaicin and dihydrocapsaicin was 94.17% of the total capsaicinoid content in the fresh sample, compared with approximately 88% for all the spices. There were significant differences between the individual and the total capsaicinoid contents of the spices (P < 0.05). The initial concentrations of capsaicin, dihydrocapsaicin and total capsaicinoids in the production of RPF decreased by 26.6%8, 12.39% and 14.75%, re-spectively. The losses in capsaicinoids during the drying period can be caused by their oxidation by peroxidase activity (Bernal et al., 1993). Similarly,Topuz and Ozdemir (2004)reported significant decreases in capsaicinoids in pepper fruits after sun drying. In contrast,Maurya et al. (2018)reported no differences between the capsaicin content of five fresh pepper types and their blanched sun-dried forms.
In contrast to the RPF, all capsaicinoids were increased in the TRI; therefore, their total content in this sample increased to 26.15%, at their highest level. In addition, both sun drying and terletme processing increased the capsaicinoid content during the production of TRI (data not shown). This increase may be attributed to the continuation of the ripening process in fruits depending on suitable aforementioned con-ditions (Topuz et al., 2011). Indeed, in the manufacture of RPF, cap-saicinoid content first increased during sun drying but then
immediately decreased, probably due to reduction in moisture content or aw. The capsaicinoid concentrations in the INI (except for homo-dihydrocapsaicin) were relatively higher than those in the RPF, despite the conversion of the RPF to INI by the thermal treatment (Fig. S1). This may be explained by the higher efficiency of extraction from the INI as a result of damage in the fruit tissue caused by the higher temperature and longer duration (Ornelas-Paz et al., 2010).
As seen inTable 2, the amount of capsaicin in fresh pepper was slightly more than that of dihydrocapsaicin, while the latter was the predominant capsaicinoid in the dried samples. Essentially, it was found that the two capsaicinoids exhibited both increases and decreases during sun drying and terletme days, but in total, dihydrocapsaicin showed a higher rate of increase (data not shown).Barbero et al. (2014)
reported an increase in the relative percentage of dihydrocapsaicin in the total capsaicinoid content during the last days of full ripening of a Cayenne pepper type. Additionally, these authors attributed the in-crease in dihydrocapsaicin to the dein-crease in capsaicin, agreeing with the trending changes in these capsaicinoids during the processing of TRI. This phenomenon suggests the possibility of the conversion of capsaicin to dihydrocapsaicin (Giuffrida et al., 2014). The pungency of the fresh sample in SHU was affected in parallel with the total capsai-cinoid content of the spice. However, the pungency of the INI was not significantly different from that of the fresh peppers (P > 0.05) (Table 2).
3.3. The DPPH scavenging capacity of samples
The antioxidant capacities of samples in terms of DPPH free radical scavenging activity are depicted inFig. 4. The DPPH scavenging ac-tivity of fresh pepper (17.85 + 0.88%) was less than that of dried samples, probably because of its high moisture content, which reduces the concentration of antioxidant components.Arslan and Ozcan (2011)
observed similar increases in DPPH radical scavenging capacity of fresh pepper after sun and oven drying (50, 60 °C). In contrast,Vega-Gálvez et al. (2009) and Rufián-Henares, Guerra-Hernández, and García-Villanova (2013)reported a higher DPPH inhibition activity of fresh red peppers than of dried peppers.
TRI showed the lowest DPPH scavenging capacity among the spices, with a value of 31.66 ± 1.52%, while INI and RPF presented similar values, 62.68 ± 1.12% and 67.94 ± 1.60%, respectively (P < 0.05).
Arslan and Ozcan (2011) reported that DPPH scavenging capacities ranged from 67.02 to 76.14% for dried peppers produced with different drying methods, including sun drying.Deng et al. (2018)demonstrated the DPPH scavenging capacities of peppers dried by different methods and temperatures to range between approximately 30 and 45%. The low antioxidant capacity for TRI was probably due to the long pro-cessing time under the sun, which caused the degradation of anti-oxidant compounds, mainly vitamin C (Cervantes-Paz et al., 2014). The findings of a recent study show that vitamin C is lost completely during the production of isot (Korkmaz et al., 2020).
The higher antioxidant capacity of the INI compared with that of the TRI may be related to a further generation of Maillard reaction com-pounds, which can enhance the antioxidant capacity (Kim & Lee, 2009).
Vega-Gálvez et al. (2009)observed that peppers dehydrated at high Table 2
Capsaicinoid consents and pungency of FRC, TRI, INI, and RPF (mg kg−1dw).
Sample CAP DHC n-DHC h-DHC Total capsaicinoids Pungency (SHU)
FRC 72.48 ± 0.08b 70.44 ± 1.44b 6.80 ± 0.17c 2.03 ± 0.05d 151.77 ± 0.68c 2383 ± 15b
TRI 75.28 ± 0.14a 94.04 ± 0.27a 13.11 ± 0.08ab 9.01 ± 0.11a 191.46 ± 0.60a 2932 ± 8a
INI 67.14 ± 0.01c 72.71 ± 0.05b 14.20 ± 1.99a 3.93 ± 0.05c 157.98 ± 2.09b 2420 ± 20b
RPF 53.14 ± 0.14d 61.71 ± 0.09c 9.97 ± 0.10bc 4.55 ± 0.05b 129.38 ± 0.52d 1984 ± 3c
FRC: Fresh Red Capsicum; TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes; CAP: capsaicin; DHC: dihydrocapsaicin; n-DHC: nordihydrocapsaicin. h-DHC: homodihydrocapsaicin.
a–dDifferent lowercase letters in same column indicate significant difference among samples (P < 0.05).
d c b a 0 15 30 45 60 75 FRC TRI INI RPF DP PH sca venging (%)
Fig. 4. DPPH free radical scavenging capacity of FRC, TRI, INI and RPF. FRC:
Fresh Red Capsicum; TRI: Traditional Isot; INI: Industrial Isot; RPF: Red Pepper Flakes. a-c Different lowercase letters indicate significant difference among
samples (P < 0.05).
A. Korkmaz, et al. Food Chemistry 341 (2021) 128184
temperatures (80 and 90 °C) showed higher DPPH scavenging activity than those dehydrated at low temperatures (50 and 60 °C), consistent with the relationship between TRI and INI. Additionally, heat treatment during INI production may cause the release of antioxidant compounds from the pepper matrix (Ornelas-Paz et al., 2013).
4. Conclusion
The changes in color quality, capsaicinoid content and antioxidant capacity of fresh pepper were evaluated for the production of TRI, INI and RPF. The results show that the RPF exhibited the highest carotenoid content, ASTA value, surface color intensity and DPPH free radical scavenging capacity, while presenting the lowest browning index and capsaicinoid content. The INI-processing method noticeably reduced the carotenoid content, ASTA and color intensity compared to the TRI-processing method, while the DPPH scavenging capacity and the browning index by the heat treatment were greatly increased. The TRI-processing method increased the content of the major capsaicinoid, in contrast to the other methods. These findings indicate a difference be-tween isot spices and red pepper flakes. Depending on the terletme op-eration, TRI production not only prevents an excessive loss of car-otenoids but also provides a desirable level of browning. Therefore, the color quality of traditional isot was better than that of the industrial isot. Additionally, depending on the production method, carotenoid content, ASTA and NEB were found to be well correlated with each other and to the parameters of surface color. Conditions for the production of tra-ditional isot pepper should be optimized for both industrial scale and standard production. Future studies are needed on the changes in color properties, capsaicinoid content and antioxidant capacity of the TRI, INI and RPF produced during storage.
CRediT authorship contribution statement
Aziz Korkmaz: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing - original draft. Ahmet Ferit Atasoy: Conceptualization, Funding acquisition, Methodology, Project administration, Data curation, Supervision, Writing - review & editing. Ali Adnan Hayaloglu: Methodology, Validation, Formal analysis, Data curation.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influ-ence the work reported in this paper.
Acknowledgments
This study was supported by The Southeastern Anatolia Project Regional Development Administration, Republic of Turkey Ministry of Industry and Technology (Project: GAP-ISOT) and Harran University Scientific Research Institutions (HUBAK Project No: 14010). The au-thors thank the Experimental Station of the GAP Agricultural Research Institute for supplying the fresh peppers used in spice production. Appendix A. Supplementary data
Supplementary data to this article can be found online athttps:// doi.org/10.1016/j.foodchem.2020.128184.
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