Comparative Analysis of Total Antioxidant Status (TAS) of Ready-to-Consume Turkish Coffees With Different Flavoring Agents
Abstract
The production and consumption of both traditional and flavored Turkish coffee varieties are widespread in several countries, including Turkey. However, the health effects of flavorings used to enhance the flavor of commercially flavored coffees remain unclear. The aim of this study was to evaluate the total antioxidant status (TAS), a biomarker of health, in plain and commercially flavored Turkish coffees (blackberry, wild strawberry, hazelnut, vanilla, rose Turkish delight, and chocolate) commonly consumed by the Turkish population. In this study, a total of 24 different coffee samples of 6 different brands with plain, blackberry, wild strawberry, hazelnut, vanilla, rose delight, and chocolate flavors were examined. TAS analysis of the samples was performed with a commercial test kit based on (2,2′-azino-di-(3-ethylbenzthiazoline sulphonate) (ABTS) radical scavenging activity, and the results were expressed in mmol Trolox equivalent (TE)/L. The results showed that blackberry-flavored(3.14 ± 0.07 mmol TE/L) and vanilla-flavored (3.13 ± 0.07 mmol TE/L) Turkish coffees exhibited lower TAS levels compared to plain Turkish coffee (3.23 ± 0.01 mmol TE/L) and coffees flavored with wild strawberry (3.24 ± 0.04 mmol TE/L), chocolate (3.22 ± 0.01 mmol TE/L), hazelnut (3.22 ± 0.01 mmol TE/L), and rose delight (3.23 ± 0.01 mmol TE/L) (p < 0.05). In conclusion, individuals who want to diversify their Turkish coffee consumption while maintaining or improving their health may prefer wild strawberry-, chocolate-, hazelnut-, and rose delight–flavored coffees over blackberry- and vanilla-flavored coffees. This study highlights the potential health benefits of certain flavored coffees as an alternative to traditional plain Turkish coffee.
1. Introduction
Coffee is the general name of the Coffea tree belonging to the Rubiaceae family, and the drink is obtained from the fruits of this tree. The most commonly used commercial coffee beans are Coffea arabica L. and Coffea canephora [1]. Depending on preparation methods, there are various types of coffee such as espresso, filter coffee, Turkish coffee, Viennese coffee, Irish coffee, and Mazagran coffee [2]. If the coffee beans have been entirely ground and prepared with boiling water, this is known as “Turkish coffee,” one of the boiled coffee types [3]. Turkish coffee is diversified with aromas such as rose delight, dibek, gum mastic, milk, chocolate, strawberry, cardamom, turpentine, and hazelnut, thus addressing the tastes of a wider consumer group [4]. The addition of flavorings enhances the product diversity offered to consumers. Recently, the consumption of coffee enriched with herbal products or spices has also become popular due to its taste characteristics [5].
Coffee is among the primary sources of dietary antioxidants, since it is a beverage frequently consumed by people that contains high levels of bioactive compounds with antioxidant activity such as hydroxycinnamic acids (caffeic, chlorogenic, coumaric, ferulic, and sinapic acids), caffeine, nicotinic acid, trigonelline, cafestol, kahweol, and tocopherols [6]. Antioxidants are substances that can prevent or reduce oxidative cell damage caused by free radicals in the body [7]. Due to its antioxidant bioactive compounds, coffee has been shown to have a protective effect on a number of diseases, including cancer, Type 2 diabetes (T2DM), metabolic syndrome, kidney stones, cirrhosis, hepatocellular carcinoma, cardiovascular diseases (CVDs), and Parkinson’s and Alzheimer’s diseases [8]. It has been indicated that the antioxidant capacity of coffee types varies according to their preparation methods and that the antioxidant capacities of Turkish coffee and filter coffee are especially higher than that of espresso [9].
Phenolic compounds can interact with various components in food, including macronutrients like carbohydrates and proteins, as well as micronutrients such as vitamins and minerals, potentially affecting their bioactivity. These interactions may lead to either synergistic or antagonistic effects, which can vary depending on the food matrix and consumption conditions, as seen with coffee phenolics [10]. The antioxidant activity of coffee, and thus its possible health effects, is influenced by the additional ingredients [11]. It has been found that some ingredients such as sugar and milk can reduce antioxidant activity. On the other hand, herbal ingredients such as rose leaves, gum mastic, carob, peanuts, and cardamom can generally increase antioxidant activity when added to coffee [5]. In a study in which rose flavor was added to Turkish coffee, it was observed that the total antioxidant capacity of Turkish coffee enriched with rose was higher than coffees prepared without adding rose [12]. In another study in which rose petal powder was added to coffee beverages, it was reported that the initial antioxidant activities of coffee and rose petal powder samples were 61.53% and 85.06%, respectively, and this ratio ranged between 75.8% and 76.8% in rose coffee samples. It was observed that the antioxidant activity of coffee increased with the addition of an herbal flavor with higher antioxidant activity than coffee [13]. In another study, the antioxidant capacity of mastic gum, carob, peanut, and cardamom flavors added to Turkish coffee was investigated and it was found that some of these flavors provided an increase in antioxidant activity [5]. It is stated that the antioxidant activity of flavored coffee beverages may increase or decrease compared to plain coffee samples, depending on the interaction between the antioxidant compounds in the coffee and the antioxidant or prooxidant compounds found in plants or other flavoring substances [5].
There are only a few studies in the literature investigating the antioxidant activity of flavored Turkish coffees, and these have focused on cardamom-, clove-, ginger-, mastic gum-, and rose-flavored Turkish coffees [5, 12, 14]. The sample sizes of these studies are quite small. As the variety of flavored Turkish coffees has increased in recent years, there is a growing need for research to guide consumer preferences. This study aimed to determine the antioxidant activities of 24 different Turkish coffees flavored with blackberry, wild strawberry, vanilla, hazelnut, rose delight, and chocolate, which have not been investigated in previous studies. This will contribute to the literature and guide consumers.
2. Materials and Methods
2.1. Sample Selection
In this study, flavored and plain Turkish coffees that are readily available in the Turkish market were obtained from online retailers between January and March 2022. There are many Turkish coffee brands available in the market. However, brands that have both plain and flavored Turkish coffee options were included. It was ensured that all coffee samples included in the study were produced only from finely ground, medium-roasted Arabica beans. A total of 24 samples of plain, blackberry-, wild strawberry-, hazelnut-, vanilla-, rose delight-, and chocolate-flavored Turkish coffees from 6 different brands were included.
2.2. Sample Preparation
The samples were prepared traditionally according to the standards determined by “The Turkish Coffee Culture and Research Association” [3]. Finely ground powdered Turkish coffees were prepared by adding 7 g of coffee to 70 mL of cold water using a Turkish coffee pot. Due to the difficulty of temperature control in traditional coffee pots, an electric Turkish coffee machine was used to ensure standardization in the preparation of the samples. The automatic Turkish coffee machine has a coffee pot that sits on an electric heating chamber. After the water and coffee are put into this coffee pot, the pot is placed on the heater section. When the coffee is ready, the machine gives a notification. In this way, all samples can be prepared at the same temperature and time.
The samples were prepared by boiling at the aforementioned conditions. First, samples were taken from the drinkable suspended coffee solution, without touching the grounds at the bottom, to Eppendorf tubes in the first minute after the coffees were prepared. Preparation of samples for analysis was adapted from the study protocol of Karabudak et al. [12]. Samples were immediately analyzed without further waiting.
2.3. Sample Analysis
2.3.1. Temperature Measurement
The temperatures of the brewed coffee samples (°C) were measured with the help of a probe thermometer (Arcone TP101TM).
2.3.2. Water-Soluble Dry Matter (°Brix) Measurement
A portable ATC Brix refractometer was used to determine the amount of dry matter dissolved in the water part of the prepared coffee samples.
2.3.3. Total Antioxidant Status (TAS) Assay
The TAS of each of the prepared coffee samples was analyzed calorimetrically using commercial kits based on the principle of 2,2′-azino-di-(3-ethylbenzthiazoline sulphonate) (ABTS) radical scavenging activity measurement (Rel Assay, Gaziantep, Turkey). In the kits, all reagents and standards included in the kits were ready for use. The principle of the test is based on the conversion of the dark blue-green colored ABTS radical solution to its colorless form by antioxidants in the sample. Total antioxidant activity was calculated using the absorbance value of the samples at 660-nm wavelength. The calibration curve was constructed using a stable antioxidant standard called Trolox [15]. The results are expressed in mmol Trolox equivalent (TE)/L. All samples were analyzed in triplicate.
2.4. Statistical Analysis
For the analysis of the study data, SPSS 22.0 package programme was used. The dependent variable was TAS values (mmol/L), and the independent variables were plain and flavored Turkish coffee varieties brewed under the same conditions. Descriptive statistics for variables are expressed as number (n) and arithmetic mean ± standard deviation (sd). The normality of continuous variables was analyzed using the Shapiro–Wilk test, as the sample size was less than 50. The null hypothesis was accepted, and the data were described as normally distributed when p > 0.05. “One-way ANOVA” was used to compare TAS (mmol/L), temperature (°C), and water-soluble dry matter (°Brix) values of plain and flavored Turkish coffee samples according to their flavors and brands. The Games–Howell test was used as a post hoc test because the variances were not equally distributed [16]. The significance level of all tests was determined as p < 0.05.
3. Results
A comparison of TAS (mmol TE/L) values of brewed, plain, and flavored Turkish coffees is given in Figure 1 and Table 1. The difference between the temperatures (°C) and Brix° values of the varieties of plain and flavored Turkish coffees brewed in a standardized way was not found to be statistically significant (p > 0.05). Additionally, the TAS values of Turkish coffee in the following flavors did not differ statistically: wild strawberry (3.24 ± 0.038 mmol TE/L), hazelnut (3.22 ± 0.010 mmol TE/L), chocolate (3.22 ± 0.012 mmol TE/L), rose delight (3.23 ± 0.006 mmol TE/L), and plain (3.23 ± 0.009 mmol TE/L). The TAS values of blackberry-flavored (3.14 ± 0.069 mmol TE/L) and vanilla-flavored (3.13 ± 0.068 mmol TE/L) Turkish coffees were significantly lower than those of plain Turkish coffee (3.23 ± 0.009 mmol TE/L) and other flavored Turkish coffee varieties (p < 0.05) (Table 1) (Figure 1).
| Coffee type | Temp. (°C) min-max | Brew. time (mean) | °Brix (mean) | TAS (mmol/L) mean ± sd | Statistical analysis of antioxidant activity according to brand | Statistical analysis of antioxidant activity according to coffee flavor |
|---|---|---|---|---|---|---|
| Plain Turkish coffee (n:6) | 79–85 | 1.07 | 1340.3 | 3.23 ± 0.009 |
|
|
| Brand A | 3.23 ± 0.002 | |||||
| Brand B | 3.23 ± 0.002 | |||||
| Brand C | 3.22 ± 0.010 | |||||
| Brand D | 3.24 ± 0.011 | |||||
| Brand E | 3.24 ± 0.003 | |||||
| Brand F | 3.22 ± 0.018 | |||||
| Blackberry flavored Turkish coffee (n:3) | 80–82 | 1.17 | 1348.6 | 3.14 ± 0.069 ∗ |
|
|
| Brand A | 3.22 ± 0.011a | |||||
| Brand E | 3.07 ± 0.052b | |||||
| Brand F | 3.14 ± 0.022a,b | |||||
| Rose delight–flavored Turkish coffee (n:3) | 80–83 | 1.10 | 1340.6 | 3.23 ± 0.006 |
|
|
| Brand A | 3.23 ± 0.001 | |||||
| Brand E | 3.23 ± 0.011 | |||||
| Brand F | 3.22 ± 0.001 | |||||
| Hazelnut-flavored Turkish coffee (n:3) | 80–84 | 1.11 | 1341.0 | 3.22 ± 0.010 |
|
|
| Brand A | 3.23 ± 0.003 | |||||
| Brand B | 3.22 ± 0.003 | |||||
| Brand C | 3.21 ± 0.014 | |||||
| Chocolate-flavored Turkish coffee (n:3) | 80–82 | 1.04 | 1340.3 | 3.22 ± 0.012a |
|
|
| Brand A | 3.23 ± 0.004 | |||||
| Brand B | 3.22 ± 0.009 | |||||
| Brand C | 3.21 ± 0.014 | |||||
| Vanilla-flavored Turkish coffee (n:3) | 80–82 | 1.03 | 1347.6 | 3.13 ± 0.068 ∗ |
|
|
| Brand A | 3.21 ± 0.002a | |||||
| Brand E | 3.09 ± 0.044b | |||||
| Brand F | 3.09 ± 0.040b | |||||
| Wild strawberry–flavored Turkish coffee (n:3) | 80–85 | 1.02 | 1340.6 | 3.24 ± 0.038 |
|
|
| Brand A | 3.23 ± 0.005 | |||||
| Brand B | 3.22 ± 0.002 | |||||
| Brand C | 3.27 ± 0.061 |
- Note: The absence of any letter in the column means that there is no statistical difference. There is no significant difference in terms of temperature, brewing time, and Brix values (p > 0.05). The p values of the results with significant differences are presented in bold.
- ∗Statistically significant difference between the mean TAS value (mmol TE/L) of flavored coffees (p < 0.05).
- a,b,cEach different letter represents a statistically significant difference between mean TAS values according to brands (p < 0.05).
The TAS values of flavored coffees according to brands are compared in Table 1. The TAS values of plain Turkish coffees and Turkish coffees with rose delight, hazelnut, chocolate, and wild strawberry flavors did not differ significantly between brands (p > 0.05). The TAS value of blackberry-flavored Turkish coffee of Brand E (3.07 ± 0.052 mmol TE/L) was significantly lower than the TAS value of blackberry-flavored Turkish coffee of Brand A (3.22 ± 0.011 mmol TE/L) (p < 0.05). The TAS value of vanilla-flavored Turkish coffee of Brand A (3.21 ± 0.002 mmol TE/L) was significantly higher than that of Brands E and F (E: 3.09 ± 0.044, F: 3.09 ± 0.040 mmol TE/L) (p < 0.05) (Table 1).
A comparison of the TAS values of Turkish coffees of the same brand is shown in Table 2. The TAS values of Turkish plain coffees of Brands A, E, and F (A: 3.23 ± 0.002, E: 3.24 ± 0.004, and F: 3.22 ± 0.008 mmol TE/L) were statistically significantly higher than those of blackberry-flavored (A: 3. 22 ± 0.011, E: 3.07 ± 0.052, and F: 3.13 ± 0.022 mmol TE/L) and vanilla-flavored (A: 3.21 ± 0.003, E: 3.08 ± 0.044, and F: 3.09 ± 0.040 mmol TE/L) coffees of the same brand (p < 0.05) (Table 2). There was no statistical difference between the TAS values of flavored coffees of Brands B, C, and D, which did not have vanilla- and blackberry-flavored coffee products.
| Coffee type | Brand | Temp. (°C) | Brewing time (min) | °Brix | TAS (mmol/L) mean ± sd | Statistical analysis |
|---|---|---|---|---|---|---|
| Plain | A | 80 | 1.07 | 1340 | 3.23 ± 0.002a |
|
| Blackberry | A | 80 | 1.17 | 1342 | 3.22 ± 0.011b | |
| Rose delight | A | 80 | 1.10 | 1341 | 3.23 ± 0.001 | |
| Hazelnut | A | 80 | 1.11 | 1341 | 3.23 ± 0.003 | |
| Chocolate | A | 80 | 1.04 | 1341 | 3.23 ± 0.004 | |
| Vanilla | A | 80 | 1.03 | 1341 | 3.21 ± 0.003b | |
| Wild strawberry | A | 80 | 1.02 | 1340 | 3.23 ± 0.005 | |
| Plain | B | 79 | 0.58 | 1340 | 3.23 ± 0.002 |
|
| Rose delight | B | 83 | 1.07 | 1341 | 3.23 ± 0.011 | |
| Hazelnut | B | 80 | 1.10 | 1341 | 3.22 ± 0.003 | |
| Chocolate | B | 82 | 1.04 | 1340 | 3.22 ± 0.009 | |
| Wild strawberry | B | 83 | 1.08 | 1341 | 3.22 ± 0.002 | |
| Plain | C | 82 | 1.02 | 1340 | 3.22 ± 0.010 |
|
| Hazelnut | C | 84 | 1.10 | 1341 | 3.21 ± 0.014 | |
| Chocolate | C | 82 | 1.06 | 1340 | 3.21 ± 0.013 | |
| Wild strawberry | C | 85 | 1.06 | 1341 | 3.27 ± 0.061 | |
| Plain | D | 80 | 1.02 | 1340 | 3.24 ± 0.011 |
|
| Rose delight | D | 83 | 1.02 | 1340 | 3.22 ± 0.001 | |
| Plain | E | 81 | 1.05 | 1341 | 3.24 ± 0.004a |
|
| Blackberry | E | 82 | 1.10 | 1352 | 3.07 ± 0.052b | |
| Vanilla | E | 82 | 1.03 | 1350 | 3.08 ± 0.044b | |
| Plain | F | 85 | 1.18 | 1341 | 3.22 ± 0.008a |
|
| Blackberry | F | 82 | 1.10 | 1352 | 3.13 ± 0.022b | |
| Vanilla | F | 82 | 1.05 | 1352 | 3.09 ± 0.040b | |
- Note: There is no significant difference in terms of temperature, brewing time, and Brix values (p > 0.05). The p values of the results with significant differences are presented in bold.
- a,bEach different letter represents a statistically significant difference (p < 0.05).
4. Discussion
Coffee is a beverage that remains popular and that is constantly researched in various aspects such as its high content of antioxidant compounds, changes in its structure, composition, and antioxidant activity during the processing and production process, and the effect of various brewing methods on its composition and antioxidant activity [17–20]. In recent years, flavored coffee products have gained an important position in the market in order to respond to consumer demands and increase product diversity. The number of studies on the composition and antioxidant activities of flavored coffee varieties is increasing day by day [5, 12, 14, 21]. According to Turkey Nutrition and Health Research-2019 data, the frequency of not consuming Turkish coffee was 25.8%, while the frequency of consuming it every day was 18.7% [22]. In this study, the effects of flavorings on the antioxidant activity of brewed Turkish coffee were investigated. Blackberry-, wild strawberry-, rose delight-, vanilla-, chocolate-, and hazelnut-flavored Turkish coffees were prepared, and the antioxidant activities of their infusions were determined and compared with the antioxidant activity of plain coffee.
The phenolic compound content and antioxidant activity of brewed coffees may differ according to the type of coffee beans, the region where the beans were grown, the degree of roasting and grinding, as well as the brewing method and duration, and the ingredients added to the coffee after brewing [23–25]. Accordingly, while selecting flavored and plain coffee varieties to be examined within the scope of our research, attention has been paid to selecting Arabica-type, medium-roasted varieties and applying the same brewing process. The absence of a significant difference between Brix and temperature values of brewed coffees is a result of applying the same brewing process. It has been indicated that the phenolic compound content and antioxidant activities of Arabica coffee beans may vary according to their varieties. In a prior study, four different Arabica coffee varieties were studied, and it was found that the Colombian variety (17.74 ± 0.32 mg GAE/g) had the highest phenolic compound content, while the Peruvian variety (10.24 ± 0.73 mg GAE/g) had the lowest phenolic compound content. Similarly, the Colombian variety (17.17 ± 0.15 mg AAE/g) had the highest antioxidant activity, while the Peruvian variety (6.17 ± 0.28 mg AAE/g) had the lowest antioxidant activity [26]. In this study, TAS values of vanilla- and blackberry-flavored Turkish coffees of Brand A were significantly lower than those of the same flavored coffees of Brand E. The use of different Arabica varieties by different brands may be among the reasons why the antioxidant capacities of blackberry- and vanilla-flavored coffees differed significantly according to the brands.
In a study that compares the antioxidant activity of Turkish coffees prepared by adding certain amounts of rose petals (0.5, 1.5, and 2.0 g) to ground Arabica coffee, it was found that there was no significant difference between the antioxidant activities (ABTS radical scavenging activity) of plain coffee and coffee with 0.5 g of rose petals added (2.2 ± 0.11 and 2.4 ± 0.09 mmol TE/L), while adding 1.5 g (2.6 ± 0.05 mmol TE/L) and 2 g (2.7 ± 0.02 mmol TE/L) of rose petals to coffee significantly increased its antioxidant activity [12]. In this study, while the TAS values (ABTS radical scavenging activity) of blackberry-flavored (3.14 ± 0.069 mmol TE/L) and vanilla-flavored (3.13 ± 0.068 mmol TE/L) Turkish coffees were found to be significantly lower compared to plain Turkish coffee (3.23 ± 0.009 mmol TE/L), the TAS values of rose delight–flavored (3.23 ± 0.006 mmol TE/L), hazelnut-flavored (3.22 ± 0.010 mmol TE/L), chocolate (3.22 ± 0.012 mmol TE/L), and wild strawberry–flavored (3.24 ± 0.038 mmol TE/L) Turkish coffees were similar to plain Turkish coffee. In a study comparing the antioxidant activities and phenolic contents of coffees with cardamom, ginger, and clove additives and plain Arabica coffee, it was found that the total polyphenol content of ginger and clove coffees was found to be statistically significantly higher than those of cardamom and plain coffees. The antioxidant activities of the coffees varied depending on the principles of the antioxidant activity analysis method. For example, cardamom and clove coffees had higher H2O2 scavenging activity than black and ginger coffees. DPPH radical scavenging activity was similar in plain, cardamom, and ginger coffees but lower in clove coffee. Ginger coffee showed statistically significantly higher ferric-reducing antioxidant activity than the other groups [14]. In another study, which examined flavored Turkish coffees supplied from Turkey (n = 6), antioxidant activities of coffees were ranked as gum mastic–flavored (98.1%) > plain (94.5%) > carob-flavored (68.3%) > peanut-flavored (53.1%) > cardamom-flavored (29.6%) [5]. It was determined that the phenolic compound contents of plain and mastic gum coffees were similar, and the results of scavenger activity toward DPPH and ABTS- + free radicals and ferric-reducing power were significantly higher than carob samples. Phenolic compound contents of carob coffees were also found to be significantly lower. These results were attributed to the differences between the plant:coffee ratios and the interaction of other compounds that do not show antioxidant activity such as sugars and amino acids in the composition of coffee with radical compounds such as Folin–Ciocalteu and ABTS [5]. Although compounds with high antioxidant activity were added to plain coffee, the antioxidant activity of the final product being lower than that of plain coffee samples, as in our study, was attributed to polymerization and interaction between phenolic compounds. The different polarities of antioxidant compounds in the composition of flavored coffee samples are another factor that may affect the number of antioxidant compounds that pass into the water in brewed coffee samples and thus the antioxidant activities of the samples [27]. There are also differences between the study designs in terms of the addition of flavor compounds [12, 14] or the inclusion of commercially available flavored Turkish coffees [5] as in this study. There is no information about the types, properties, and quantities of flavoring additives in commercially flavored coffees. These factors may have contributed to the lower antioxidant activity of blackberry- and vanilla-flavored coffees compared to plain and other flavored coffees in this study and may have contributed to the significant difference in antioxidant activity of blackberry- and vanilla-flavored coffees according to brand. Flavoring method of the coffee is also an important factor influencing antioxidant activity. The maceration method (coffee soaked in flavoring fruits) and the addition of flavor additives/oils postroasting significantly affect the final product’s antioxidant activity. In one study, the levels of 5-HMF and acrylamide increased and chlorogenic acid decreased by 4.64–6.48 g/100 g in coffees with flavor additives compared to macerated and control groups [21]. These changes in these compounds negatively affect the antioxidant activity of coffee. The addition of food flavors such as cherry, strawberry, grapefruit, and vanilla resulted in similar antioxidant properties to the control coffee extract. In contrast, mango and raspberry flavors reduced the antioxidant properties. This result was associated with the prooxidant activity of some flavor compounds containing unsaturated double bonds by contributing to radical production [21].
It is indicated that vanilla, one of the ingredients used to flavor Turkish coffee varieties analyzed in this study, contains vanillic acid, 4-hydroxybenzyl alcohol, 4-hydroxy-3-methoxybenzyl alcohol, 4-hydroxybenzaldehyde, and vanillin. It has been found that the antioxidant activity of 4-hydroxybenzyl alcohol and 4-hydroxy-3-methoxybenzyl alcohol, which are among the constituents of vanilla, is significantly higher than those of vanillin and vanillic acid [28]. The results show that the antioxidant activity of the vanilla extract, which is traditionally used as a flavoring agent, can vary depending on the ratio of the components it contains. The antioxidant capacity of vanilla is also significantly affected by the extraction method and bean quality [29]. Similarly, a study comparing the phenolic compound content and antioxidant activity of blackberry species according to extraction method has found that the phenolic compound content (2688.1 ± 11.1 mg GAE/100 g) and antioxidant activity (108.43 ± 1.23 μmoL TE/g) of samples extracted with methanol were determined to be significantly higher than those samples extracted with water (2285.9 ± 13.0 mg GAE/100 g and 75.17 ± 1.31 μmoL TE/g, respectively) [30]. Since the brewed coffee samples were also extracted with water, the antioxidant activity of coffee samples with flavoring additives may have been found similar to or lower than that of plain Turkish coffee samples due to this reason.
5. Conclusions and Recommendations
According to the results of this study, it was found that the antioxidant capacity of blackberry- and vanilla-flavored Turkish coffee varieties was significantly lower compared to plain and other flavored Turkish coffee varieties (wild strawberry, chocolate, hazelnut, and rose delight). In meeting the need for changing consumption, other flavored Turkish coffee varieties (wild strawberry, chocolate, hazelnut, and rose delight) may be a better alternative than blackberry- and vanilla-flavored varieties. It may also be recommended for health-conscious individuals who want to consume flavored Turkish coffee with higher antioxidant activity than plain coffee to add flavoring herbal sources in powder form to their coffee. On the other hand, the antioxidant activity of blackberry- and vanilla-flavored coffees also varied depending on the brand, flavor characteristics, coffee bean characteristics, and processing methods. Furthermore, it is difficult to interpret the results as there is no information about how the flavorings were added. The inclusion of this information on product labels by coffee producers would be useful for both consumers and researchers.
This study has the limitation that the results of the study cannot be generalized to other Turkish coffees sold around the world, as it reflects the results of Turkish coffees that were on the market in a certain period in Turkey. In addition, in this study, the antioxidant activities of coffees were analyzed only in terms of ABTS radical scavenging activity. According to previous studies, it is seen that flavored coffee types vary according to methods based on different principles (DPPH, ABTS, ferric-reducing activity, etc.). Therefore, one of the limitations of this study is that antioxidant activity was not analyzed with a different method other than ABTS. Considering these conditions, it is necessary to carry out further studies. In order to provide a precise recommendation, it is necessary to carry out studies evaluating the quantity, type, and activity of antioxidants in a greater number and variety of flavored Turkish coffee samples.
In summary, future studies may consider analyzing the antioxidant activity of coffee samples using different methods and determining their total phenolic content. Additionally, identifying the amount of chlorogenic acid, the primary antioxidant compound in coffee, along with the major antioxidant compounds in added flavoring ingredients, would help clarify the impact of these flavoring compounds on antioxidant activity.
Conflicts of Interest
The authors declare no conflicts of interest.
Author Contributions
All authors designed and drafted the work or revised it critically for important intellectual content and approved the final content of this manuscript.
Funding
This study was funded by grants from the Gazi University Projects of Scientific Investigation (BAP) (TLO-2022-7474).
Acknowledgments
The authors have nothing to report.
Open Research
Data Availability Statement
We declare that the data supporting the conclusions of the article are fully described within the article, and the database is available from the first author ([email protected]) upon reasonable request.
