Production and evaluation of total phenolics, antioxidant activity, viscosity, color, and sensory attributes of quince tea infusion: Effects of drying method, sonication, and brewing process

Graphical abstract

Highlights

• •Effect of drying method and sonication on phenolics content of quince tea infusion was studied.
• •Antioxidant activity and total phenolic of tea dried in infrared dryer (250 W, distance = 7 cm) were higher.
• •The infusion prepared by the infrared has a reddish-brown hue (higher a* value).
• •Sensory attributes scores of the infusion prepared with infrared dryer were higher.

Abstract

This study aimed to examine the influence of drying approaches (convective and infrared (IR)), sonication, and brewing time on the total phenolic content (TPC), antioxidant activity (AA), viscosity, color indexes, and sensory attributes of quince tea infusion (QTI). The AA and TPC in the QTI dried in the IR dryer were higher than in the convective dryer. The TPC and AA of QTI prepared by convective and IR dryers increased when the ultrasound treatment and brewing time were increased. In terms of viscosity and Brix, there was no differences between the QTIs and the average viscosity and density of the samples were 1.79 ± 0.28 mPa.s and 3.18 ± 0.07°Brix, respectively. The QTI prepared by the IR has a reddish-brown hue (higher a* value), but the samples prepared with the convective dryer were yellow (higher b* value). The sensory attributes scores of QTI prepared by IR were higher than those of convection-dried samples. In general, the use of an IR dryer for drying grated quince, ultrasound treatment for 8 min, and brewing time for 30 min is a promising condition for the production of QTI with higher TPC and AA, and with appropriate color and sensorial acceptance.

1. Introduction

Fruit tea infusions or fruit teas are very interesting in different countries due to their diverse taste, medicinal properties, antioxidant properties and bioactive compounds [1], [2]. Depending on the type of dried fruit used to make fruit tea, this tea may contain useful minerals, some vitamins, sugar, and various pigments (such as anthocyanins and carotenoids) [3], [4]. Sari and Hardiyanti [4] confirmed that a longer withering period and a shorter rolling period would enhance total phenolic content (TPC) (223.70 μg gallic acid equivalent (GAE)/ml), antioxidant activity (AA), and lightness color of dragon fruit peel tea. Şahin [3] confirmed that rutin is the main phenolic compound in the fruit tea infusions.

Quince (Cydonia oblonga) is known as an important food source of health-promoting compound, due to its AA, TPC, and antibacterial characteristics [5]. In addition, several researchers reported that dried quince is a natural and inexpensive source of TPC, that are powerful antioxidants [6], [7]. Global quince production has increased 1.3 times over the past decade and according to FAO data from 2019, 666,000 tons of quince were produced on an area of 93700 ha in 37 different countries [8]. Dried quinces are used as a tea in different countries [1], [6], [9]. The influence of drying methods (sun and oven) on the AA of quince tea was studied by Gheisari and Abhari [6]. Their results showed that the oven-dried and quince peel contained higher TPC than the sun-dried and flesh quinces, respectively. In another study, the influence of heat treatment (20–60 min) on TPC, AA, and organoleptic attributes of quince tea infusion (QTI) was investigated by Maghsoudlou, et al. [9]. Because of the increased AA caused by the heating process, these researchers recommended QTI as a healthy beverage. Several chemical and sensory properties of QTI were studied by Sohrabvandi, et al. [1]. According to the nutrient content and sensory evaluation of QTI, these researchers reported a 20-minute brewing time as the optimal condition.

As the ultrasonic wave propagates, creating cycles of contraction and expansion causes bubbles to form in the solution and cavitation as a result. This phenomenon, combined with an increase in the temperature of the sample, causes cell wall destruction, accelerated diffusion, and mass transfer, and ultimately the release of more and more intracellular compounds such as phenolic compounds [10], [11], [12], [13]. Zeinali Namdar and Gharekhani [14] reported that the use of ultrasound increased the efficiency of the extraction of phenolic compounds from the dried product during the tea brewing process. Das and Eun [15] recommend using ultrasound due to high extraction efficiency to prepare antioxidant-rich green tea extract.

The quality and physicochemical properties of fruits after harvest can be significantly altered throughout the supply chain [16], [17]. Infrared (IR) technique is a technology with potential energy-saving (up to 50%) and high performance, application in the food processing sector is still under development. Researchers comparing IR drying with methods based on hot-air have shown that the IR technique is faster than the hot-air technique [18]. Yao et al. [19] reported that compared with hot air, using an IR dryer preserved higher TPC and nutrients in mango slices. In addition, this method improves the color characteristics of the product and better preserves its microstructure. Fadaie et al. [20] results showed that the power of IR radiation and the distance between the lamp and sample had a significant influence on the moisture loss kinetics and drying time of persimmon slices. Furthermore, the average density and rehydration ratio of persimmon slices dried by IR dryer were 639 kg/m³ and 270 %, respectively.

Little information is available in the literature regarding QTI. In addition, we found no report on the effects of the IR drying process, ultrasonic treatment, and brewing time on the TPC, AA, viscosity, color (L*, a*, and b* parameters), and sensory attributes of QTI in the literature. Hence, the purpose of this work was to estimate the impacts of drying approaches (convective and IR), ultrasound treatment time (40 kHz, at three levels of 0, 4, and 8 min), and brewing time (for 15 and 30 min) on the physicochemical characteristics and sensory attributes (color and appearance, aroma, taste acceptance, consistency, and total acceptance) of QTI.

2. Materials and methods

2.1. Drying process of grated quince

First, fresh quince fruits (Cydonia oblonga L.) were washed, and using a stainless steel homemade grater, the quinces were grated. For convective drying, the grated quinces were dried in an oven (70 ± 2 °C, Shimaz, Iran), until reaching a constant weight. For IR drying, an IR dryer (length 440 mm, width 200 mm, and height 400 mm) with an IR radiation source (250 W, Noor, Iran) was used for drying grated quinces. In this dryer, the distance of grated quinces from the radiation lamp was 7 cm.

2.2. Ultrasound treatment

The dried grated quinces were poured into a beaker and distilled water was added in a ratio of 1:20. The beakers were placed inside an ultrasonic bath (40 kHz, vCLEAN1-L6, Backer, Iran). In this research, the effect of the ultrasound pretreatment time at three levels of 0, 4, and 8 min on the grated quinces was investigated.

2.3. Brewing process

Infusion or brewing refers to the process of immersing fruit in hot water. For brewing quince tea, the beakers (containing sonicated samples) were placed in a water-bath (R.J42, Pars Azma Co., Iran) at 80 °C (Fig. 1). To prepare QTI, the beakers were placed in the water-bath for 15 and 30 min. In this study, a handheld refractometer (juanjuan, Guangdong, China) was used to determine the total soluble solids (°Brix) of the QTIs.

Fig. 1.

Schematic of production (drying process, sonication, and brewing process) and evaluation of quince tea infusion.

2.4. Total phenolic content (TPC)

The TPC of QTI was measured spectrophotometrically (UV–VIS spectrophotometer, XD-7500, Lovibond, Germany) at 765 nm after the reaction with Folin-Ciocalteu’s (Sigma-Aldrich, USA) phenol reagent, according to the technique described by Salehi et al. [21]. The measurement was compared with a standard calibration curve of gallic acid solution and the result was reported as μg GAE/ml of QTI samples.

2.5. DPPH scavenging assay

For DPPH (2,2-Diphenyl-1-picrylhydrazyl) method [21], a solution of DPPH (0.1 mM, Sigma-Aldrich, USA) was prepared in methanol (Merck, Germany). A volume of 2 ml of this solution and 2 ml of QTI were mixed in a test tube. The discoloration of the DPPH radical was recorded at 517 nm using an UV–VIS spectrophotometer (XD-7500, Lovibond, Germany), 30 min after the start of the reaction and incubation at 25 °C in the dark place. Equation (1) was utilized to determine the DPPH free radical scavenging activity of QTI [21].

$$\mathit{DPPHFRSA}(\%)=\left(1-\frac{\mathit{AB}{S}_{\mathit{tea}}}{\mathit{AB}{S}_{\mathit{con}}}\right)\times 100$$ (1)

where ABS_tea is absorbance of QTI samples, and ABS_con is absorbance of control-sample.

2.6. Viscosity of quince tea infusion (QTI)

The viscosity of QTI was determined using a viscometer (Brookfield, DV2T, RV, USA). The viscosity and shear stress of QTI solution at different shear rate (12–134 s⁻¹) were studied using UL Adapter Kit at 25 °C. In this study, the Power law model was used to fit the experimental shear stress-shear rate data of QTI solution (Equation (2).

$$\tau =k{\dot{\gamma }}^n$$ (2)

where τ is the shear stress (mPa), k is the power law consistency coefficient (mPa.sⁿ), $\dot{\gamma }$ is the shear rate (s⁻¹) and n is the power law flow behavior index (dimensionless).

2.7. Color of quince tea infusion (QTI)

A Samsung 25 Megapixels camera (A 50, Samsung Group, South Korea) was utilized to photograph the QTI. The color of QTI was analyzed using Image J software (V.1.42e, USA). The L* (lightness), a* (greenness/redness), and b* (blueness/yellowness) values for each sample were recorded in triplicates [22], [23].

2.8. Sensory evaluation

After summarizing the results and selecting the best QTI from each treatment, four samples of QTI, each made with different conditions, were produced, scored, and rated for sensory attributes (color and appearance, aroma, taste acceptance, consistency, and total acceptance) by 10 panelists. In the QTI sensory evaluation, panelists were given four samples to rate how much they liked samples using a hedonistic 9-point scale (1 = strongly disliked, 5 = neither like nor dislike, 9 = strongly liked). These four samples were: 1- convective dried, unsonicated and brewed for 30 min, 2- convective dried, sonicated for 8 min and brewed for 30 min, 3- IR dried, unsonicated and brewed for 30 min, and 4- IR dried, sonicated for 8 min and brewed for 30 min.

2.9. Statistical analysis

The evaluation of QTIs was conducted in a 2 × 3 × 2 × 3 (dryer type, ultrasound treatment time, brewing time, and three replicates) factorial design. Data are presented as mean ± standard deviation for triplicate measurements. Statistical analysis was performed by one-way analysis of variance (ANOVA) at 95% level of significance, using SPSS software (version 21). In addition, means were compared with Duncan's multiple range test at 95% level of significance.

3. Results and discussion

3.1. Total phenolic content (TPC)

The reported values in Table 1 reveal that the drying method, sonication, brewing time, and “sonication × brewing time” interaction have considerable impacts (p < 0.05) on the TPC of QTI. But, the “drying method × sonication”, “drying method × brewing time”, and “ drying method × sonication × brewing time ” interactions, have no significant impacts on the TPC of QTI (p > 0.05). The impacts of the drying method, ultrasound treatment time, and brewing process on the TPC of QTI are shown in Fig. 2. The TPC in the QTI dried in the IR dryer was higher than in the convective dryer. The average TPC of QTIs made from grated quince dried by the convective and IR methods was 182.93 μg GAE/ml and 245.96 μg GAE/ml, respectively. The TPC in QTI (IR-dried samples) was lower than the TPC in a green tea (649.33 μg GAE/ml) but it was higher than the TPC in a black tea (188.00 μg GAE/ml) [4]. The results of the study by Selvi, et al. [18] demonstrated that IR dehydration of rose petals promoted an enhance in TPC extracted from the petals. Their observation refers to the fact that IR dehydration damages the cell walls of the petals and thus facilitates the separation of TPC. Also, Ren et al. [24] reported that of the 4 drying methods (convective, vacuum, freeze, and IR dryers), IR had the shortest drying time and the bioactive components were better retained in the dried products.

Table 1.

Results of analysis of variance for total phenolics of quince tea infusion.

Sources of changes	Degrees of freedom	Sum of squares	Mean square	P
Dryer	1	35747.5	35747.5	0.000
Ultrasound	2	22022.6	11011.3	0.000
Brewing	1	5358.0	5358.0	0.000
Dryer × Ultrasound	2	89.2	44.6	0.844
Dryer × Brewing	1	0.3	0.3	0.973
Ultrasound × Brewing	2	1794.6	897.3	0.049
Dryer × Ultrasound × Brewing	2	286.2	143.1	0.585
Error	24	6259.5	260.8
Total	35	71557.8

Fig. 2.

Effects of drying method, ultrasound treatment time (U), and brewing time (B) on the total phenolic content of quince tea infusion. Various letters near the bars denote statistically significant differences at p < 0.05.

The TPC of QTI prepared by convective and IR dryers increased when the ultrasound treatment and brewing time were increased. By increasing the time of ultrasonic application from 0 to 8 min, the average amount of TPC in QTI increased from 211.36 μg GAE/ml to 273.34 μg GAE/ml (in IR-dried samples). Ultrasonic process can increase the extraction of bioactive compounds, such as phenolic compounds, from the cell wall by inducing cavitation and thereby enhancing mass transfer around colloidal particles [21], [25]. The results of Yildiz et al. [26] study confirmed that ultrasonic treatment inhibited the growth of bacteria, mold, and yeast in freshly cut quince slices when stored at 4 °C. In addition, the ultrasonically treated slices demonstrated considerable improvement in bioactive compounds and improved physical characteristics compared with all other treatments.

By increasing the brewing time from 15 to 30 min, the average amount of TPC in QTI increased from 233.66 μg GAE/ml to 258.25 μg GAE/ml (in IR-dried samples). Das and Eun [15] reported that compared with the control, the sonication extraction method considerably enhanced the yield of TPC, catechins, and flavonoids content, and resulted in higher AA of green tea. Furthermore, they confirmed that the maximum extraction performance of the bioactive metabolites from green tea occurred at 80 °C for 20 min.

3.2. DPPH radical scavenging activity

Statistical analysis of data confirmed that the drying method, sonication, brewing time, and “ drying method × sonication ” interaction, have considerable effects on the AA of QTI (p < 0.01) (Table 2). But, the “drying method × brewing time”, “sonication × brewing time”, and “ drying method × sonication × brewing time ” interactions, have no significant impacts on the AA of QTI (p > 0.05). The impacts of drying method, sonication, and brewing time on the DPPH radical scavenging activity of QTI are shown in Fig. 3. The AA in the QTI dried in the IR dryer was higher than in the convective dryer. The average AA of QTIs made from grated quince dried by the convective and IR methods was 61.99% and 82.15%, respectively. The impact of drying methods (microwave, IR, and oven) on the TPC and AA of dried lemon peel powder was investigated by Özcan et al. [27]. The powder obtained after dehydration demonstrated the minimum AA (58.72%) in the convective dried powder and the maximum AA (67.84%) in the IR dried powder.

Table 2.

Results of analysis of variance for DPPH radical scavenging activity of quince tea infusion.

Sources of changes	Degrees of freedom	Sum of squares	Mean square	P
Dryer	1	3657.5	3657.5	0.000
Ultrasound	2	6575.7	3287.9	0.000
Brewing	1	616.7	616.7	0.000
Dryer × Ultrasound	2	1840.3	920.1	0.000
Dryer × Brewing	1	13.9	13.9	0.369
Ultrasound × Brewing	2	106.8	53.4	0.058
Dryer × Ultrasound × Brewing	2	34.5	17.2	0.369
Error	24	398.2	16.6
Total	35	13243.5

Fig. 3.

Effects of drying method, ultrasound treatment time (U), and brewing time (B) on the DPPH radical scavenging activity of quince tea infusion. Various letters near the bars denote statistically significant differences at p < 0.05.

The AA of QTI prepared by convective and IR dryers increased when the sonication and brewing time were increased (Fig. 3). By increasing the time of ultrasonic application from 0 to 8 min, the average AA of QTI increased from 74.13% to 90.04% (in IR-dried samples). Impact of the preparation conditions of marjoram (Origanum vulgare) tea on the level of AA was studied by Zeinali Namdar and Gharekhani [14]. The results of this work confirmed that by applying ultrasound and increasing brewing time, the TPC and AA of tea increased. By increasing the brewing time from 15 to 30 min, the average AA of QTI increased from 78.63% to 85.67% (in IR-dried samples). The impacts of infusion time and temperature on the AA and TPC of white tea were examined by Pérez-Burillo et al. [28]. These authors found that the free radical scavenging capacity of white tea increased linearly with brewing time and water temperature.

3.3. Viscosity of QTI

In this study, the effects of changing shear rate (12–134 s⁻¹) on the viscosity and shear stress of the QTI solution were investigated (Fig. 4). In terms of viscosity and Brix, there was no significant differences between the QTIs and the average viscosity and density of the samples were 1.79 ± 0.28 mPa.s and 3.18 ± 0.07°Brix, respectively. Also, fitting ability of Power law model to experimental data of QTI is shown in Fig. 4. The results confirmed that the Power law model was the suitable equation to describe the flow behavior of QTI solution (R² > 0.954). Based on the Power law model, the QTI demonstrated non-Newtonian behavior, which is described by a flow behavior index value (n) higher than 0.846. The results demonstrate that the values of k range from 1.710 to 3.385 mPa.sⁿ.

Fig. 4.

Shear stress-shear rate data and Power law model fitting ability for the quince tea infusions. ** CON=convective; IR=infrared; U= ultrasound treatment time (min); B= brewing time (min).

3.4. Color

Prolonging the brewing time is associated with increased extraction of desired color and flavor compounds. The color of fruit tea and its development after brewing depends on the amount of natural pigment extracted from the fruit and the rate of brown pigment production due to the browning reaction including enzymatic, caramelization, and Maillard [10], [29]. The QTI prepared by the IR has a reddish-brown hue (higher a* value), but the samples prepared with the convective dryer were yellow (higher b* value). Effects of drying method, ultrasound treatment time, and brewing process on the color indexes of QTI are reported in Table 3. The lightness index was considerably higher for convective dried samples (p < 0.05). The mean L*, a*, and b* values of QTI processed by convection drying were 86.37, −1.81, and 56.43, respectively. The redness index was significantly higher for IR-dried samples (p < 0.05). The mean L*, a*, and b* values of QTI processed by IR drying were 51.54, 40.87, and 54.01, respectively. In convective-dried samples, the lightness value of the QTI significantly decreased with increasing sonication time from 0 to 8 min (p < 0.05). But, in IR-dried samples, the lightness value of the QTI significantly increased with increasing sonication time from 0 to 8 min (p < 0.05). In convective-dried samples, the redness value of the QTI significantly increased from −3.19 ± 1.14 to 2.90 ± 1.25 with increasing sonication time from 0 to 8 min (p < 0.05). But, in IR-dried samples, the redness value of the QTI decreased from 44.51 ± 0.30 to 38.29 ± 0.75 with increasing sonication time from 0 to 8 min (p > 0.05). Brewing time (15 and 30 min) had no significant effect on the lightness and redness indexes of the QTI (p > 0.05). In IR-dried samples, the yellowness index value of the QTI significantly increased from 48.82 ± 1.45 to 58.46 ± 1.25 with increasing sonication time from 0 to 8 min (p > 0.05).

Table 3.

Effects of drying method, ultrasound treatment time (U), and brewing time (B) on the color indexes of quince tea infusions.

Drying method	Treatment type	Lightness (L*)	Greenness/Redness (a*)	Yellowness (b*)
Convective	U = 0;B = 15	89.08 ± 1.38 a	−5.16 ± 2.18 d	54.70 ± 0.54 cde
	U = 0;B = 30	87.11 ± 1.78 ab	−3.19 ± 1.14 d	61.81 ± 5.40 a
	U = 4;B = 15	88.19 ± 0.47 ab	−3.79 ± 0.72 d	52.53 ± 2.08 cde
	U = 4;B = 30	86.89 ± 1.92 ab	−2.88 ± 1.70 d	60.76 ± 5.56 ab
	U = 8;B = 15	84.38 ± 3.55 bc	1.26 ± 2.58c	55.56 ± 2.24 bcd
	U = 8;B = 30	82.58 ± 1.93c	2.90 ± 1.25c	53.19 ± 2.51 cde
Infrared	U = 0;B = 15	46.08 ± 2.06 e	45.70 ± 1.34 a	50.75 ± 3.43 de
	U = 0;B = 30	45.47 ± 4.82 e	44.51 ± 0.30 a	48.82 ± 1.45 e
	U = 4;B = 15	55.15 ± 2.10 d	39.67 ± 1.30 ab	54.08 ± 1.87 cde
	U = 4;B = 30	54.10 ± 1.09 d	39.74 ± 3.09 ab	56.20 ± 2.75 abcd
	U = 8;B = 15	54.39 ± 2.88 d	37.34 ± 0.81 ab	55.77 ± 4.88 bcd
	U = 8;B = 30	54.05 ± 1.62 d	38.29 ± 0.75 ab	58.46 ± 1.25 abc

^*The values with different superscript letters in a column are significantly different (p < 0.05).

3.5. Sensory attributes

Table 4 demonstrates the sensory evaluation results of QTIs. Sensory evaluation of the samples revealed that the IR-dried samples scored higher than the convective-dried samples in all properties tested. Therefore, drying grated quinces by IR radiation can increase the marketability of QTIs. In terms of sensory evaluation, the convective-dried and unsonicated sample was of poor quality and received the worst scores. QTIs dried by IR, sonicated for 8 min and brewed for 30 min were the best samples in terms of organoleptic characteristics. The results of sensory evaluation of fruit tea produced by Sohrabvandi, et al. [1] showed that increasing the brewing time by 10 min significantly improved the taste and color of the product.

Table 4.

Sensory attributes of quince tea infusions.

Sample	Color and appearance	Aroma	Taste acceptance	Consistency	Total acceptance
CON;U = 0;B = 30	3.80 ± 1.69b	5.10 ± 1.37b	4.80 ± 2.35b	5.30 ± 2.26 a	5.20 ± 1.23b
CON;U = 8;B = 30	4.50 ± 2.22b	6.10 ± 1.85 ab	5.50 ± 1.72 ab	5.60 ± 1.78 a	5.90 ± 1.52 ab
IR;U = 0;B = 30	7.00 ± 0.67 a	7.20 ± 1.32 a	6.70 ± 2.00 a	6.10 ± 2.51 a	6.70 ± 2.00 a
IR;U = 8;B = 30	7.50 ± 1.27 a	7.10 ± 1.20 a	6.80 ± 1.69 a	6.70 ± 1.89 a	7.30 ± 1.16 a

* CON = convective; IR = infrared; U = ultrasound treatment time (min); B = brewing time (min).

** The values with different superscript letters in a column are significantly different (p < 0.05).

4. Conclusion

Dried quince can be an alternative for production of healthy tea infusion as it is a rich source of TPC. QTI is nutritious and rich in phenolic compounds. In this work, the impacts of drying approaches, sonication, and brewing process on the TPC, AA, viscosity, color indexes, and sensory attributes of QTI was examined. The TPC of sonicated samples was higher than the untreated samples. The TPC in the QTI dried in the IR dryer was higher than in the convective dryer. The TPC of QTI prepared by convective and IR dryers increased when the sonication and brewing time were increased. Based on the Power law model, the QTI demonstrated a non-Newtonian behavior, described by the flow behavior index value higher than 0.846. The results demonstrated that the values of k range from 1.710 to 3.385 mPa.sⁿ. The lightness index was significantly higher for convective dried samples (p < 0.05). The redness index was significantly higher for IR-dried samples (p < 0.05). QTI dried by IR, sonicated for 8 min, and brewed for 30 min were the best samples in terms of organoleptic characteristics. Future studies can be carried out to investigate the applications of other non-thermal technologies (high pressure processing, pulsed electric field, and pulsed light) on the quality and sensory attributes of fruit tea infusions.

CRediT authorship contribution statement

Fakhreddin Salehi: Conceptualization, Methodology, Validation, Investigation, Writing – review & editing, Software, Formal analysis, Writing – original draft, Data curation. Helia Razavi Kamran: Software, Formal analysis, Data curation. Kimia Goharpour: Software, 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 influence the work reported in this paper.