Effect of different drying methods on total bioactive compounds, phenolic profile, in vitro bioaccessibility of phenolic and HMF formation of persimmon

Journal Pre-proof Effect of different drying methods on total bioactive compounds, phenolic profile, in vitro bioaccessibility of phenolic and HMF formation of persimmon Selma Kayacan, Salih Karasu, Perihan Kübra Akman, Hamza Goktas, Ibrahim Doymaz, Osman Sagdıc PII:

S0023-6438(19)31172-7

DOI:

https://doi.org/10.1016/j.lwt.2019.108830

Reference:

YFSTL 108830

To appear in:

LWT - Food Science and Technology

Received Date: 31 January 2019 Revised Date:

7 November 2019

Accepted Date: 8 November 2019

Please cite this article as: Kayacan, S., Karasu, S., Akman, Perihan.Kü., Goktas, H., Doymaz, I., Sagdıc, O., Effect of different drying methods on total bioactive compounds, phenolic profile, in vitro bioaccessibility of phenolic and HMF formation of persimmon, LWT - Food Science and Technology (2019), doi: https://doi.org/10.1016/j.lwt.2019.108830. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

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Effect of Different Drying Methods on Total Bioactive Compounds, Phenolic Profile, In Vitro Bioaccessibility of Phenolic and HMF Formation of Persimmon

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Selma Kayacan1, Salih Karasu, 1Perihan Kübra Akman1, Hamza Goktas1, Ibrahim Doymaz2, Osman Sagdıc1 1

Yildiz Technical University Faculty of Chemical and Metallurgical Engineering, Department of Food Engineering, 2 Yildiz Technical University Faculty of Chemical and Metallurgical Engineering, Department of Chemical Engineering

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Corresponding Author

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Corresponding author address:

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Salih Karasu

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Yildiz Technical University, 34210, Istanbul Turkey

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E-mail: [email protected], [email protected]

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Tel: +90 212383 4581

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Faks: +90 212 383 4571 1

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Abstract

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This study aims to investigate the effects of different drying methods namely, ultrasound-

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assisted vacuum-drying (USV), freeze-drying (FD), infrared-drying (ID) and hot-air drying

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(HAD) on bioactive compounds, phenolic profile, in vitro bioaccessibility of phenolic

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compounds, color change, sugar profile and HMF formation of persimmon fruits. Total

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phenolic contents (TPC) were 77.2, 112.5, 124.9 and 262.4 mg GAE/100 g for HAD, ID,

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USV, and FD, respectively. CUPRAC, DPPH, β-carotene and lycopene level were 219.2-

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635.2 mg TE/100 g, 101.1-299.7 mg TE/100 g, 294.3-438.5 mg/100 g and 720.6-966.5

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mg/100 g, respectively. Drying methods significantly affected both amounts of individual

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phenolics and their distribution (P < 0.05). Epigallocatechin was determined as a major

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phenolic compound for all samples (88.2-383.2 mg/100 g). All drying process significantly

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increased the bioaccessibility of phenolic compounds (P < 0.05). HAD showed the highest in

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vitro bioaccessibility. All drying methods significantly affected ∆E values (P < 0.05). HMF

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values were 12.1, 15.0 and 23.4 mg/kg for ID, USV and HAD samples, respectively and was

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not found for FD. This study suggested that USV and ID could be used as an alternative

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drying method to FD and conventional drying due to high drying rate, less phenolic

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degradation, HMF formation, and color change.

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Keywords: Lycopene, β-carotene, epigallocatechin, CUPRAC, flavonoids

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1. Introduction

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Persimmon is from Ebenaceae family, is cultivated widely in warm temperate regions,

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including China, Korea, Japan, Brazil, Turkey, and Italy (Butt et al., 2015). Persimmon is

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abundant in glucose and fructose, phenolic compounds, carotenoids, and minerals. Due to

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high water content and nutritional value, the shelf life of ripened persimmon is quite short,

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and it is perishable. Any preservation methods should be applied to extend shelf life and

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provide consuming of fruit all year rounds.

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Drying is one of the most common methods used in the preservation of fruits and vegetables.

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Hot-air drying or conventional drying is the most popular drying methods due to its low cost

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and easy application (Diamante, Ihns, Savage, & Vanhanen, 2010; Wojdyło et al., 2016).

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However, it has several disadvantages due to its long drying time. The extended drying

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process can cause some undesirable effects such as degradation of bioactive compounds, loss

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in nutritional and sensory quality, higher shrinkage, occurrence in undesirable compounds and

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lower rehydration ratio (Wojdyło et al., 2016). 5-hydroxymethylfurfural (HMF) is an

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intermediate Maillard reaction product and considered as a harmful compound to human

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health. In addition to the undesirable effect on human health, HMF formation causes

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nutritional loss by a reduction in the amino acids and sugar contents. Therefore HMF

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formation can be considered as a quality index for dried products and its level should be

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determined after the drying process (Gunel, Tontul, Dincer, Topuz, & Sahin-Nadeem, 2018;

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Jorge et al., 2018).

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Freeze-drying (FD) is considered the best drying method because FD produces high sensory

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and nutritional quality dried foods and provide in lower shrinkage, and higher rehydration

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capacity. However, it is not preferred because it is a prolonged and expensive process and not

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easy use (Wojdyło et al., 2016). The innovative drying methods should be applied to increase

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mass and heat transfer rates, and reduce degradation in some bioactive compounds and 3

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occurrence in undesirable compounds with a low cost and easy application. In this study,

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ultrasound-assisted vacuum drying (USV), infrared drying (ID), freeze-drying (FD) and hot-

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air drying (HAD) were used to drying of persimmon. USV is innovative drying method and

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has been applied in a few studies in the drying of beef meat, chicken (Başlar, Kılıçlı, Toker,

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Sağdıç, & Arici, 2014), fish (Başlar, Kılıçlı, & Yalınkılıç, 2015), green beans (Tekin, Başlar,

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Karasu, & Kilicli, 2017) and red peppers (Tekin & Baslar, 2018). However, no study has been

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conducted on the drying of persimmon with USV.

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Some studies have reported on the drying of persimmon. Nicoleti et al. (2005) dried

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persimmon with air drying at different temperatures and velocities. Then, they were evaluated

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viscoelastic properties of dried persimmons. In another study, ascorbic acid degradation of

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persimmon during tray drying was investigated (Nicoleti, Silveira, Telis-Romero, & Telis,

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2007). Cárcel, García-Pérez, Riera, and Mulet (2007) used ultrasonically enhanced convective

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drying and conventional drying method in order to dry persimmons. They compared drying

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kinetics of both drying methods. Doymaz (2012) evaluated some thin-layer drying models of

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persimmon. Karaman, Toker, Yüksel, et al. (2014) dried persimmon and investigated effects

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on drying methods, which are freeze-drying oven drying, and vacuum oven drying, on

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bioactive and physicochemical properties of persimmon. These studies focused on the total

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phenolic content and antioxidant activity, which are determined by spectrophotometric

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methods. The effects of drying on phenolic profile and their in vitro bioaccessibility should be

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investigated. The effects of different drying methods on phenolic bioaccessibility of

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persimmon could not found in the literature. Another novelty of this study is an investigation

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of in vitro bioaccessibility of phenolic compounds of dried persimmon. Only components

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released from the food matrix and absorbed in the small intestine are potentially bioavailable

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and show beneficial properties. Therefore, it is essential to research the bioaccessibility of

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phenolic components and other antioxidants from solid matrices (Palafox-Carlos, Ayala4

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Zavala, & González-Aguilar, 2011). This study aims to investigate the effects of different

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drying methods namely, USV, FD, ID and HAD on total phenolic compounds, phenolic

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profile, in vitro bioaccessibility of phenolic compounds, color change, sugar profile and HMF

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formation of persimmon fruits.

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2. Materials and methods

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2.1. Material

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Fresh persimmon fruits were purchased from a local market in Istanbul, Turkey. Fruits with

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homogeneous characteristics (of the same size and color) were selected, and damaged fruits

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were discarded. Until drying processes, the fruits were stored at 4 °C in polyethylene bags.

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All the standards and chemicals used in this study were obtained from Merck (Darmstadt,

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Germany).

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2.2. Drying procedure

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Persimmon samples were dried with four different methods which are infrared drying (ID),

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ultrasound-assisted vacuum drying (USV), hot-air drying (HAD) and freeze-drying (FD).

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Before drying processes, persimmons were cut into equal slices with 2 mm thickness and 5

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cm length. USV was carried out according to the method described by Başlar et al. (2014)

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study. The drying process for USV and HAD was performed at 55 °C air temperatures. HAD

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was performed at a constant air velocity of 2 m/s. The air velocity was calculated by a Testo

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440 vane probe anemometer (Lutron, AM-4201, Taiwan). The air flow was applied

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horizontally through the surface of the persimmon slices. The ID was performed in a moisture

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analyzer (Snijders Moisture Balance, Snijders b.v., Tilburg, Holland). Infrared power (IP)

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level of drying process was 88 W. IP level was determined using a digital energy meter

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(PeakTech 9035, Germany). FD was conducted according to a standard program of freeze-

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dryer (Martin Christ, Beta 1-8 LSCplus). Moisture loss of the persimmon slices was recorded

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at 30 min intervals during HAD, USV, and ID. The sample weight was recorded by a digital 5

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balance (Mettler-Toledo AG, Grefensee, Switzerland, model BB3000) with 0.1 g accuracy.

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The drying process was finished when the final moisture content of the dried persimmon

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slices reached about 0.2 kg water/kg dry matter (d.b.). The experiments were carried out in

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triplicate, and plotting of the drying curves for HAD, USV, and ID was performed by using

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the average values of the moisture content.

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2.3. Extraction procedure of phenolics

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Fresh and dried persimmon samples were extracted by methanol-water (50:50). The ratio of

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solid material to the solvent was 1:10. The mixture was homogenized by an ULTRA-

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TURRAX (Daihan, HG-15D) at 10.000 rpm for 2 min. After homogenization, the mixture

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was incubated by shaking for 2 h at room temperature. At the end of the incubation, samples

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were centrifuged at 3920 g. The supernatant was filtered by a 0.45 µm filter.

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2.4. Total phenolic content

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The total phenolic content (TPC) of persimmon samples was performed according to the

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modified method expressed by Singleton and Rossi (1965). 2.5 mL of tenfold diluted Folin

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Ciocelteau’s phenol reagent was added to tubes containing 0.5 mL of extract. Then 2 mL of

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Na2CO3 (7.5%) was added to this mixture. After 30 min incubation, the absorbance was read

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at 760 nm with a UV/VIS spectrophotometer (Shimadzu UV-1800, Kyoto, Japan). The total

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phenolic content was expressed as mg gallic acid equivalent (GAE) per 100 g of dry matter

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(mg GAE/100 g DM).

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2.5. Total flavonoid content

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The total flavonoid content (TFC) found in extracts was estimated according to the method

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described by (Zhishen, Mengcheng, & Jianming, 1999). A 1 mL extract was mixed with 4 mL

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of distilled water. 0.3 mL of NaNO2 (5 mg/ 100 mL water) was added to this mixture. After 5

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min, 0.3 mL of AlCl3 (10 g/100 ml water ) was added. Then, 2 mL aqueous solution of NaOH

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(4 g NaOH/100 mL water) and 2.4 mL of distilled water were added. The absorbance of the

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mixture was measured at 510 nm using a UV/VIS spectrophotometer, and the results were

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expressed as mg catechin equivalent per 100 g of dry matter (mg CE/100 g DM).

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2.6. Antioxidant capacity

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1,1-diphenyl-2-picrylhydrazyl (DPPH) and the copper-reducing antioxidant capacity

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(CUPRAC) methods were used to determine the antioxidant capacity of extracts. In the DPPH

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method, a 0.1 mL of persimmon extract was mixed 4.9 mL DPPH solution (4.0 mg/100 mL

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methanol). The mixture was incubated for 20 min at room temperature, and the absorbance

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was read at 517 nm (Singh, Chidambara Murthy, & Jayaprakasha, 2002). CUPRAC method

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was performed according to the method described by Apak, Güçlü, Özyürek, and Karademir

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(2004). A 0.1 mL of persimmon extract was mixed with 1 mL solution of CuCl2 (170.48 mg

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CuCl2.2H2O/100 mL water), 1 mL solution of Nc (0.156 g Nc/100 mL ethanol) and 1 mL

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solution of NH4Ac (7.708 g NH4Ac/100 mL water ) and then 1 mL distilled water was added

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to the mixture to complete the volume of the mixture to 4.1 mL. The mixture was incubated

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60 min at room temperature. The absorbance was measured at 450 nm. The results of

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antioxidant capacity were expressed as mg Trolox equivalent per 100 g dry matter (mg

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TE/100 g DM).

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2.7. In vitro digestion assay

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In vitro digestion assay was carried out according to the method suggested by McDougall,

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Dobson, Smith, Blake, and Stewart (2005). The persimmon samples were mixed with 20 mL

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of distilled water. Then, 1.5 mL pepsin solution (40 mg /mL) was added, and pH was adjusted

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to 1.7 with an aqueous solution of HCl (18.23 g/100 mL water). This mixture was incubated

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at 37 °C in a water bath for 2 h with shaking at 100 rpm. This part simulates gastric

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conditions. At the end of 2 h, 2 mL of aliquots of postgastric digestion (Pg) were removed and

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stored at -20 °C. 4.5 mL of 4 mg/mL pancreatin and 25 mg/mL bile salts mixture was added

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to the remainder which placed in a 250 mL glass beaker. A cellulose dialysis tube (15 cm)

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was filled with sufficient solution of NaHCO3 (2 g/100 mL water) to neutralize the sample’s

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titratable acidity. The beaker was sealed using parafilm and incubated at 37 °C for 2 h. This

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part simulates small intestine conditions. After incubation, the solution outside the dialysis

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tube was taken as the Out sample representing material that remains in the gastrointestinal

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tract. The solution that entered the dialysis tubing was taken as the In sample representing the

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material that entered the serum. Then, total phenolic content and antioxidant activity analyses

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were performed for Pg, In and Out samples. The percentage recovery of bioaccessibility was

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calculated by dividing as the values determined for the In fraction to the values determined

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for initial (before digestion) values and then multiply by 100 (Tomas et al., 2017).

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2.8. Individual phenolic compounds

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Individual phenolic compounds of fresh and dried persimmon samples were determined by

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HPLC coupled to a diode array (HPLC-DAD, Shimadzu Corp., Kyoto, Japan).

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previously obtained extracts for used in TPC analysis were filtered through a 0.45-µm

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membrane filter and 1 mL of the filtered sample was analyzed in an HPLC system (LC-20AD

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pump, SPDM20A DAD detector, SIL-20A HT autosampler, CTO-10ASVP column oven,

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DGU-20A5R degasser, and CMB-20A communications bus module; (Shimadzu Corp.,

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Kyoto, Japan). Separations were conducted at 40 °C on a reversed-phase column (Intersil®

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ODS C-18, GL Sciences, Tokyo, Japan) with a 250 mm × 4.6 mm length, 5 µm particle size.

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The mobile phases were solvent A (distilled water with 0.1% (v/v) acetic acid) and solvent B

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(acetonitrile with 0.1% (v/v) acetic acid). A gradient elution were 10% B (0 to 2 min), 10% to

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30% B (2 to 27 min), 30% to 90% B (27 to 50 min) and 90% to 100% B (51 to 60 min) and at

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63 min returns to initial conditions. The flow rate was adjusted as 1 mL/min. Chromatograms

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were recorded at 254-356 nm. Identification and quantitative analysis were performed based

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on retention times and standard curves. The result of individual phenolics amounts was

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expressed as mg/L for fresh and dried samples.

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The

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2.9. β-carotene and lycopene determination

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The extraction of both carotenes was performed according to the method described by Wright

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and Kader (1997) study with some modifications. 10 mL ethanol was added to 2 g fresh and

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dried samples and homogenization with an ULTRA-TURRAX (Daihan, HG-15D) at 10.000

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rpm for 3 min. Then 8 mL hexane was added and homogenized for 3 min. The mixture was

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centrifuged for 5 min at 6000 × g. After centrifugation, 5 mL of a saturated solution of NaCl

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and 8 mL hexane was used to re-extraction of sediment. And then, obtained supernatant was

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saponified with 15 mL 10% methanolic KOH for 12 h. This solution was transferred into a

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separatory system to remove KOH with aqueous solution of NaCl (10 g/100 mL) and distilled

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water. The hexane phase was evaporated, and the residue was diluted by 2.5 mL acetone.

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The β-carotene and lycopene analysis was performed by by HPLC coupled to a diode array

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(HPLC-DAD, Shimadzu Corp., Kyoto, Japan) with HPLC system (LC-20AD pump,

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SPDM20A DAD detector, SIL-20A HT autosampler, CTO-10ASVP column oven, DGU-

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20A5R degasser, and CMB-20A communications bus module; (Shimadzu Corp., Kyoto,

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Japan) was used. Separations were conducted at 40 °C on Intersil® ODS C-18 reversed-phase

215

column (250 mm × 4.6 mm length, 5 µm particle size). The mobile phase was distilled water

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acetonitrile and methanol (100/10/5). A gradient elution were 10% B (0 to 2 min), 10% to

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30% B (2 to 27 min), 30% to 90% B (27 to 50 min) and 90% to 100% B (51 to 60 min) and at

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63 min returns to initial conditions. The flow rate was adjusted as 1 mL/min. Chromatograms

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were recorded at 450 nm. Identification and quantitative analysis were performed based on

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retention times and standard curves. β-carotene and lycopene results were expressed as

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mg/100 g for fresh and dried samples.

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2.10. Sugar content and HMF contents

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Determination of sugar composition of the samples was performed using the HPLC system

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(Shimadzu, Japan), equipped with a refractive index detector (RID-10A) and CARBOSep 9

0

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CHO-682 Pb column. The column temperature was thermostatted at 80

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chromatographic separation was obtained using the isocratic flow of ultrapure water at a flow

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rate of 0.4 ml/min. For each analysis, ten gram of sample was extracted with the addition of

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100 mL of distilled water for 4 hours using mechanic shaker at room temperature. After that,

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the extract was filtered through a 0.45 µm membrane filter, and 20 µL filtrate was injected

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into the column. The number of sugars was calculated using an external calibration curve,

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and the results were expressed in g/100 g sample.

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An HPLC system (Shimadzu, Japan) equipped with a diode array detector, an autosampler

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and a temperature-controlled column oven, Inertsil ODS3 C18, five µm, 4.6 x 250 mm

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column was used to determine HMF content in the persimmon samples. The isocratic mobile

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phase was 0.1 g/100 mL aqueous acetic acid solution and acetonitrile (90:10, v/v) at a flow

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rate of 1.0 mL/min. The column temperature was 40 oC, and the injection volume was 20 µL.

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Data acquisition was performed ranged from 220 to 660 nm wavelength, and the

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chromatograms were acquired at 285 nm. The amount of HMF was calculated using an

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external calibration curve (R2 = 0.99), and the results were reported in mg/kg.

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C. The

2.11. Color

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A chroma meter (CR-400, Konica Minolta, Tokyo, Japan) with a measuring head of an 8-mm

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aperture and the CIE Standard Illuminate D65, di:8° (diffuse illumination/8° viewing angle)

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was used for the color measurements. L* (whiteness/darkness), a* (redness/greenness), and

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b* (yellowness/blueness) were used to express color values of samples, and total color change

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of the samples was expressed with ∆E. ∆E was estimated

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equation:

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∆E = (∆L* )2 + (∆a* )2 + (∆b* )2

according to the following

(1)

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Chroma (C*) is known as a quantitative attribute of colorfulness. In order to determine the

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degree of difference of a hue by comparison with grey color with the same lightness, C* is

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used. C* was calculated following equation:

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C * = a *2 + b *2

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(2)

2.12. Statistical analysis

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The statistical analysis was performed using the Statistica software program (StatSoft, Inc.,

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Tulsa, OK). All the analyses for dried and fresh samples were performed in triplicate. The

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standard deviation and mean value were expressed. ANOVA was performed to determine the

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differences between samples. Duncan, multiple comparison tests at 95% significance level

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was used to evaluate the effect of different drying methods on bioactive compounds, in vitro

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bioaccessibility, phenolic profile change, and color and HMF formation of persimmon.

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Person’s coefficient of correlation was used for the comparing of the antioxidant capacity and

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bioactive compounds.

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3. Results and discussion

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3.1. Effect of drying methods on drying time

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Fig 1 showed a drying curve of the persimmon samples dried by HAD, USV, and ID. Drying

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times were 255, 310, and 742 min for ID, USV and HAD method, indicating that ID and USV

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exhibited higher drying rate comparing to HAD. The higher drying rate of ID can be

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explained by the higher power density than HAD. The transfer of ID energy from the heating

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source to the food surface is conducted without heating the surrounding air and heat from the

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ID source can be delivered to directly food surface with high efficiency (Ahmad, Marhaban,

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& Soh, 2015). Drying time for USV was lower than conventional drying. The cavitations

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mechanism generated during ultrasound process may cause a higher drying rate. Higher

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drying rate in ID and USV for red pepper drying were also reported from Tekin and Baslar

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(2018) studies.

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3.2. Effect of drying methods on TPC, TFC, AA, β-carotene and lycopene

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Table 1 showed the effects of different drying methods on TPC. TPC of fresh persimmon

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samples was found 265.1 mg GAE/100 g. The TPC value of fresh persimmon samples was in

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the range of Karaman, Toker, Çam, et al. (2014) study. In their study, TPC value changed

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according to the solvent used and was reported as 96.77 and 3872 mg GAE/100 g. Senica,

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Veberic, Grabnar, Stampar, and Jakopic (2016) reported TPC as 364.88 mg GAE/100 g. Their

279

result was similar to our study. TPC values of fresh persimmon sample significantly

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decreased after drying processes (P < 0.05) and calculated as 77.2, 112.5, 124.9 and 262.4 mg

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GAE/100 g for HAD, ID, USV, and FD, respectively. HAD showed the lowest TPC than

282

other methods. As well know of the fact that the phenolic compounds are susceptible to heat

283

treatment and oxidation. The high drying time during conventional drying could cause

284

degradation in phenolic compounds. The highest TPC of persimmon sample obtained from

285

USV as compared to the other thermal drying processes. During the USV process, cavitation

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mechanism could increase rupture of plant cell and phenolic extraction rate. Also during

287

USV, acoustic energy produced with ultrasound and vacuum application reduced mass and

288

heat transfer resistance and drying time (Yang, Li, Tao, Luo, & Yu, 2018). Lower drying time

289

might have resulted in a lower thermal load and phenolic degradation. Lower degradation in

290

USV and ultrasound-assisted conventional drying were also reported from other studies

291

(Kroehnke et al., 2018; Tekin & Baslar, 2018; Tekin et al., 2017). ID showed higher phenolic

292

content than conventional drying (HAD). Possibly, covalent bonds could be broken down,

293

and antioxidants could be released by far-infrared (Meng, Fan, Li, & Zhang, 2017) so that

294

TPC for ID was higher than that of HAD. TPC results of fresh persimmon and FD persimmon

295

were close to each other. It is widely known that FD is conducted at very low temperatures

12

296

and can be considered as the best drying technique regarding preserve bioactive or other

297

nutrition components of foods (Duan et al., 2015). The results of our study were comparable

298

with previously published studies conducted on drying of persimmon and other fruits (Gao,

299

Wu, Wang, Xu, & Du, 2012; Jung et al., 2005; Karaman, Toker, Çam, et al., 2014).

300

Similar results were reported for TFC of persimmon. HAD, ID and USV heat treatments

301

caused a significant decrease in TFC of persimmon. There was no significant difference in

302

TFC values of fresh persimmon (15.56 mg CE/100 g DM). and FD persimmon (15.19 mg

303

CE/100 g DM) (P > 0.05). The lowest TFC value was obtained from the HAD sample (6.52

304

mg CE/100 g DM).

305

DPPH and CUPRAC methods were used to calculate the antioxidant capacity of persimmon.

306

A high correlation was observed with antioxidant capacity and, TPC and TFC results.

307

Pearson’s coefficient of correlation (r) values was presented in Table 1. According to Table

308

1, r values an as higher than 0.87, and CUPRAC results showed higher correlation than DPPH

309

results. It was found that fresh persimmon samples had the highest antioxidant capacity, and

310

FD followed this. The results of the antioxidant capacity of this study were in accordance with

311

the findings of Wojdyło et al. (2009). Our and their study indicated that the drying process

312

led to a decrease in antioxidant properties of fruits. This result could be due to degradation of

313

the bioactive compounds like phenolic and carotenoids due to higher thermal load.

314

Degradative enzymes, thermal degradation of phytochemicals, and the loss of antioxidant

315

enzyme activities are related to reducing antioxidant activity (Korus, 2011). The antioxidant

316

capacity reduced with increasing thermal load. Therefore a proper drying procedure should be

317

conducted to preserve antioxidant capacity during the drying process. In our study, FD, USV,

318

and ID showed a higher antioxidant capacity than conventional drying. USV could be used as

319

an alternative drying technique to FD for remaining antioxidant capacity.

13

320

Table 1 also showed the effect of different drying methods on β-carotene and lycopene level.

321

According to Table 1, β-carotene and lycopene level of fresh samples were found 438.5 and

322

966.51 mg/100 g, respectively. In a similar to our study, β-carotene level was reported as 599

323

mg /100 g in Senica et al. (2016) study. The lycopene level was lower than our study (45 mg/

324

100g). Both β-carotene and lycopene level significantly reduced after all drying process

325

except FD. FD applied samples showed similar β-carotene and lycopene levels to fresh

326

samples (P > 0.05). The high retention of the lycopene and β-carotene level during freeze-

327

drying could be due to low contact temperature and a low oxygen partial pressure during the

328

drying process (Regier, Mayer-Miebach, Behsnilian, Neff, & Schuchmann, 2005). Higher

329

reduction in β-carotene and lycopene level (32% and 25.46%) was observed from the samples

330

applied by HAD. These results can be explained by the degradation of carotenes during the

331

long drying process at 55 °C. USV and ID showed a lower reduction in β-carotene and

332

lycopene level compared to HAD. It can be explained by lower drying time in USV and ID.

333

For all drying process, a high correlation was observed between both lycopene β-carotene and

334

antioxidant capacity results (Table 1).

335

The reduction in β-carotene (40%) and lycopene (22%) level of firm persimmon during the

336

drying process at 45 °C was reported from Senica et al. (2016). The effect of different drying

337

methods (solar, oven, vacuum, and freeze) on the retention of bioactive compounds including

338

β-carotene (40%) and lycopene in African eggplant were studied by Mbondo, Owino,

339

Ambuko, and Sila (2018). They reported that higher and lower retention in β-carotene was

340

observed from freeze and oven drying, respectively.

341

3.3. Effect of different drying Methods on Individual Phenolic Contents

342

Table 2 showed the effect of FD, USV, ID, and HAD process on the individual phenolic

343

contents of the persimmon. In this study, thirty-three, phenolic compounds standards were 14

344

used for the characterization of individual phenolic compounds. Drying methods affected both

345

phenolics content distribution and their level. FD showed sixteen phenolic compounds while

346

HAD exhibited only six phenolic compounds. Individual phenolic distribution and level of

347

fresh samples and FD applied samples showed a similar trend. Thirteen different phenolic

348

compounds were determined in fresh samples. Vanillic acid, naringenin, and p-coumaric acid

349

were not detected in fresh samples. This result can be explained by rupturing of plant cells

350

and facilitate extraction of phenolic after freeze drying process. Other drying methods caused

351

a significant reduction in the level of most phenolic compounds (P < 0.05). USV and ID

352

showed thirteen and nine phenolic compounds, respectively. This result showed that some

353

phenolic compounds were completely degraded during some the drying process, especially in

354

HAD.

355

Epigallocatechin was determined to be major phenolic compounds for all samples and ranged

356

from 88.20 to 383.27 mg/100 g. The samples dried by FD and ID showed the highest and

357

lowest epigallocatechin level, respectively. All drying methods, except FD, reduce

358

epigallocatechin level during the drying process. USV showed the second-highest

359

epigallocatechin level (361.95 mg/100 g). Higher retention in epigallocatechin for USV

360

treated sample could be explained by the breakdown of the plant cell by cavitation effects

361

generated from the ultrasound. Gallic acid was found as major phenolic acid, and its highest

362

level was obtained from the samples dried by FD and ID (24.50 and 20.62 mg/100 g

363

respectively). Gallic acid was not detected from the samples dried by HAD, indicating that

364

degradation of the gallic acid occurred during a long period of conventional drying. Epi-

365

catechin was the third major phenolic compound, and its level significantly changed

366

according to drying methods (1.22-2.28 mg/100 g). FD showed highest epi-catechin level

367

followed by USV, ID, and HAD. Similar to the other phenolics higher reduction in epi-

368

catechin level was observed from HAD. P-coumaric acid, ellagic acid methyl ester syringate, 15

369

and trans-cinnamic were observed from all samples. Unlike other phenolics, HAD showed

370

highest trans-cinnamic level followed by FD. Myricetin and resveratrol were only obtained

371

from the samples dried by FD and USV, indicating that other drying methods cause

372

degradation in these compounds. Higher retention of phenolic compounds by FD was also

373

reported from previously published studies (de Torres, Díaz-Maroto, Hermosín-Gutiérrez, &

374

Pérez-Coello, 2010).

375

In conclusion, individual phenolic compounds level and distribution significantly were

376

affected by drying methods. USV techniques showed higher phenolic distribution and major

377

phenolic levels. Therefore USV could be used as an alternative technique to FD to preserve

378

phenolic compounds and bioactive compounds during the drying process with lower drying

379

times and operation cost.

380

3.4. In vitro digestion assay

381

Effect of the drying methods on the in vitro digestion assay of TPC, TFC, and CUPRAC of

382

fresh and dried persimmon was shown in Table 3. According to Table 3, all drying process

383

including freeze-drying led to a significant increase in the recovery of bioaccessibility of total

384

phenolic, total flavonoid, and antioxidant capacity (P < 0.05). The increase in the

385

bioaccessibility of the phenolic and antioxidant could be explained by increasing the release

386

of bounded phenolic by heat treatment during the drying process. The thermal treatment may

387

cause a breakdown of the plant matrix and increased phenolics release (Dewanto, Wu, & Liu,

388

2002). During HAD drying time was higher than another method at 50 °C. HAD and ID

389

showed higher bioaccessibility than other drying methods. Higher bioaccessibility of the ID

390

and HAD might be due to a higher thermal load during the drying process. There were

391

limited researches in the literature about the effect of drying on the bioaccessibility of

392

phenolics. Kamiloglu and Capanoglu (2013) studied on in vitro bioaccessibility of

393

polyphenols in fresh and sun-dried figs (Ficus carica L.). It was reported from their study that 16

394

drying led to an increase in the In fraction of yellow figs. In a similar to our study, Zhao et al.

395

(2017) reported that hot air drying showed higher phenolic bioaccessibility in dried

396

Rhodomyrtus tomentosa berries compared to microwave and combined microwave-

397

conventional drying. The increase in phenolic bioaccessibility after thermal treatment was

398

also be reported from other studies (Tomas. et al., 2017).

399

3.5. Effect on Sugar and HMF contents

400

Considering macronutrients, persimmon has around 16% carbohydrates of sugars, which are

401

mostly fructose, glucose, and sucrose. These sugars can be found in a higher amount than in

402

other fruits which are commonly consumed (Pérez-Burillo, Oliveras, Quesada, Rufián-

403

Henares, & Pastoriza, 2018). Among the examined sugars, fructose and glucose were

404

determined in the range of 17-29 g/100 g fruit (Table 4), while sucrose was only detected at

405

much lower levels (data not shown). This could be explained by the activity of invertase,

406

which hydrolyzes sucrose into glucose and fructose (Del Bubba et al., 2009). The amounts of

407

glucose and fructose in ID, USV, and HAD samples were found much lower than in FD

408

samples. This is probably a result of the formation of HMF, which is a heat-induced

409

compound when heat treatment of ID, USV, and HAD were applied. The sugars are inclined

410

to chemical conversion at elevated temperatures. There was no significant difference in the

411

fructose and glucose content when the drying methods of ID, USV, and HAD were compared.

412

Although the major sugars of persimmons are sucrose, glucose, and fructose, various data on

413

related levels in sugar composition of persimmon have been reported in the literature (Ittah,

414

1993). Besides these differences are generally due to the genetic factors, these could also be

415

related to several parameters such as invertase activity, ripening stage, the method of

416

extraction, etc. (Daood, Biacs, Czinkotai, & Hoschke, 1992; Ittah, 1993). Pérez-Burillo et al.

417

(2018) reported that the effects of genetic factors on persimmon and kiwi fruit sugar

418

compositions. In another study, Del Bubba et al. (2009) indicated that the sucrose amount of 17

419

persimmon fruit decreased due to strong invertase activity during maturity. In the study of

420

Erturk or Çandır, Ozdemir, Kaplankiran, and Toplu (2009), changes of the sugar composition

421

in persimmon fruits were investigated during the maturity stages (stage I, stage II and stage

422

III) and found that glucose and fructose amount increased during the maturity, while sucrose

423

amount decreased at the beginning of the growth but increased at the end of stage III.

424

Similarly, in this study, the results were probably related to genetic factors and the maturity

425

period of persimmon fruits.

426

According to the HMF analysis, sugars were exposed to chemical transformation by heat

427

applications. These applications could lead to Maillard reaction and caramelization of sugars

428

in the acid medium of persimmon samples, and therefore, variable amounts of HMF were

429

detected in the samples (Rada-Mendoza, Olano, & Villamiel, 2002). The HMF was not found

430

in FD samples since it is a heat-induced compound. However, HMF was found as 12.13,

431

15.06, and 23.47 mg/kg for the samples dried by ID, USV, and HAD respectively. The HMF

432

amount in the samples might be related to the duration of heat application. Namely, the main

433

reason for the higher HMF content in HAD could be the more extended period of heat

434

application compared to ID and USV. HMF is also related to the browning of persimmon

435

samples, which were exposed to heat applications. The lightness index was found lowest in

436

HAD samples with the highest HMF amount compared to other samples.

437

3.6. Color

438

Table 5 showed the color values of fresh and dried persimmon samples. Initial L*, a* and b*

439

values of the samples were 48.98, 14.95 and 32.56 respectively. As it is seen from the Table,

440

L*, a*, and b* values decreased after HAD, ID, USV processes significantly (P < 0.05). The

441

color of the fresh and dried persimmons were As mentioned before in previous parts, β-

442

carotene and lycopene degradation and HFM formation were higher for the samples applied

443

by HAD. Degradation in these pigments and HMF formation could cause a reduction in color

18

444

parameters. ∆E value is a useful tool to describe total color change after the drying process.

445

∆E value changed between 21.57 and 23.63, indicating that higher color change was observed

446

from HAD except for FD. Higher drying time in the HAD process could result in higher

447

pigment degradation and non-enzymatic browning (Guiné & Barroca, 2012). High ∆E for FD

448

can be explained by a different mechanism. In the freeze-drying process, thermal degradation

449

and non-enzymatic browning reaction do not occur (Gao et al., 2012), and color parameters

450

increase after the drying process. This can be explained by increasing of the pigments

451

concentrations after removing water. It is known that vacuum drying is suitable for heat-

452

sensitive products, but a total color change of USV was found higher than ID. Tekin et al.

453

(2016) indicated that ultrasound application stimulated pigment degradation. C* value of

454

fresh persimmon was 35.83. After thermal processes, this value decreased to 16.37, 18.63,

455

and 14.88 for HAD, ID, USV, respectively. After freeze-drying, C* value increased to 54.81.

456

The high chroma value of the samples means that the color intensity perceived by humans is

457

so high (Pathare, Opara, & Al-Said, 2013). Therefore, the decrease in C* value for HAD, ID,

458

and USV can be explained by pigment degradation.

459

4. Conclusion

460

In this study, four different drying methods were applied to determine the effects on phenolic

461

and sugar composition, bioaccessibility, and color of persimmons. All drying methods, except

462

FD, showed a significant change in all determined parameters. HAD caused the highest

463

reduction in phenolic compounds β-carotene, lycopene, and antioxidant capacity level.

464

Highest color change and HMF formation were also observed in HAD treated samples.

465

In contrast to these disadvantages, HAD led to an increase in vitro bioaccessibility of phenolic

466

compounds. USV and ID significantly increased drying rate and caused lower degradation in

467

phenolic compounds compared to the HAD process. This study suggested that FD should be

468

used to preserve bioactive compounds level, antioxidant activity, and color quality. 19

469 470

References

471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515

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629 630 631 632 633 634 635 636 637 638 639 640 641 642

23

MR ( kg water/kg dry matter)….

2.5

ID HAD

2.0

USV

1.5 1.0 0.5 0.0 0

643

150 300 450 600 Drying time (min)

750

644 645

Fig 1 Drying kinetic of persimmon (HAD: hot air drying, ID: infrared drying, USV: ultrasound

646

assisted vacuum drying, MR: Moisture ratio).

647 648 649 650 651 652 653 654 655 656 657 658 659 660 24

661

662 663 664 665 666 667

Fig 2. The pictures of the dried and fresh samples (A: fresh persimmon samples, B: sliced fresh persimmon samples, C: hot air drying (HAD) persimmon samples, D: ultrasound assisted vacuum drying (USV) persimmon samples, E: infrared drying (ID) persimmon samples, F: freeze drying (FD) persimmon samples

25

668

Table 1 The results of TPC, TFC, CUPRAC, and DPPH

669 Bioactive properties

TPC1 TFC CUPRAC2 DPPH3 β-carotene Lycopene

Samples

r

Fresh

FD

ID

USV

HAD

265.1 ± 1.7a 15.6 ± 0.7a 635.2 ± 13.5a 299.7 ± 3.0a 438.5 ± 16.2a 966.5 ± 33.2a

262.4 ± 0.5a 15.2 ± 0.4a 630.9 ± 0.6a 296.6 ± 0.6a 427.0 ± 1.4a 931.5 ± 28.9a

112.5 ± 0.4c 9.7 ± 0.2c 368.6 ± 3.1c 219.9 ± 12.3c 386.5 ± 7.7b 808.8 ± 0.6c

124.9 ± 1.3b 11.1 ± 0.1b 376.8 ± 6.9b 234.9 ± 17.1b 347.2 ± 19.4cb 883.2 ± 15.2b

77.2 ± 0.9d 6.5 ± 0.4d 219.2 ± 9.6d 101.1 ± 6.8d 294.3 ± 19.9d 720.6 ± 1.0d

DPPH

CUPRAC

0.8765 0.9149 0.9049 1 0.8516 0.8656

0.9267 0.9292 1 0.9430 0.8416 0.8656

670 671

HAD, hot air drying; ID, infrared drying; USV, ultrasound assisted vacuum drying; FD, freeze drying; TPC: Total phenolic content, TFC: Total flavonoid content,

672

Different lowercase letter in the same line indicates differences between samples subjected to different drying methods (P < 0.05). r, Pearson coefficient of correlation.

1

TPC expressed as mg GAE/100 g DM CUPRAC expressed as mg TE/100 g DM 3 DPPH expressed as mg TE/100 g DM 2

26

673

Table 2 Individual phenolic compounds of dried persimmon

HAD nd nd nd 205.138 ± 1.316c nda nd 1.224 ± 0.053c 0.154 ± 0.009b nd

Amount of phenolics (mg/100 g) USV ID FD 3.879 ± 0.197d 20.62 ± 0.268c 24.508 ± 0.712b 0.704 ± 0.032b 0.417 ± 0.001c 1.391 ± 0.100a nd nd 1.084 ± 0.100b b d 361.958 ± 1.443 88.208 ± 1.267 383.272 ± 8.752a 0.258 ± 0.029c 0.466 ± 0.046b 0.664 ± 0.081a 0.15 ± 0.007b nd 0.285 ± 0.001a 1.552 ± 0.033b 1.38 ± 0.084c 2.28 ± 0.200a c d 0.123 ± 0.004 0.095 ± 0.000 0.457 ± 0.031a 0.508 ± 0.029c 0.589 ± 0.003c 0.744 ± 0.011a

Fresh 31.254 ± 1.77a 1.438 ± 0.100a 2.110 ± 0.010a 399.136 ± 5.850a 0.469 ± 0.001b nd 3.02 ± 0.650a nd 0.672 ± 0.040b

0.491 ± 0.028b

1.821 ± 0.055a

0.269 ± 0.001c

0.424 ± 0.020b

0.385 ± 0.001b

nd

0.068 ± 0.001

nd

nd

nd

0.059 ± 0.006c 0.439 ± 0.027a nd nd nd nd

0.173 ± 0.004b 0.194 ± 0.001c 0.957 ± 0.003b nd nd nd

nd 0.149 ± 0.007d nd nd nd nd

0.220 ± 0.015a 0.318 ± 0.012b 1.102 ± 0.005a 0.108 ± 0.010 0.356 ± 0.048a 1.015 ± 0.060b

0.185 ± 0.010ab 0.284 ± 0.050b 1.076 ± 0.104a nd 0.378 ± 0.030a 1.282 ± 0.037a

Phenolic compounds Gallic acid Homogentisic acid Catechin Epigallocatechin Chlorgenic acid Vanilic acid Epin-catechin p-Coumaric acid Rutin hydrate Ellagic acid+Methyl syringat 3-4 Dimethoxy cinnamic acid Resveratrol trans Cinnamic acid Myricetin Naringenin Kaempferol Isorhamnetin

674 675

Note: nd: not detected. HAD, hot air drying; ID, infrared drying; USV, ultrasound assisted vacuum drying; FD,

676

freeze drying. Different lowercase letter in the same line indicates differences between samples subjected to

677

different drying methods (P < 0.05)

27

678 679 680

Table 3 The results for the bioaccessible TPC, TFC, CUPRAC of fresh and dried persimmons

681

TPC4

CUPRAC5

Initial Pg In Out Recovery (%) Initial Pg In Out Recovery (%)

Fresh

FD

ID

USV

HAD

265.1 ± 1.73a 140.33 ± 6.48a 13.04 ± 3.24ab 131.90 ± 18.36a 4.92 ± 0.05d 635.19 ± 13.52 a 50.52 ± 0.07e 24.31 ± 0.03e 44.15 ± 0.74c 3.82 ± 0.02d

262.4 ± 0.58a 49.61 ± 1.06b 14.43 ± 0.48b 51.04 ± 0.39b 5.51 ± 0.35d 610.94 ± 6.04 a 61.22 ± 0.08c 25.50 ± 0.05d 41.87 ± 0.11d 4.17 ± 0.05d

112.5 ± 0.48c 27.39 ± 0.81c 17.24 ± 0.24a 15.53 ± 1.29c 15.32 ± 0.09b 368.65 ± 3.14b 95.45 ± 0.03a 48.16 ± 0.01a 54.83 ± 0.02a 13.06 ± 0.09b

124.9 ± 1.34b 26.19 ± 1.12c 16.25 ± 0.90a 15.03 ± 0.60c 13.10 ± 0.10c 376.81 ± 6.98b 90.45 ± 0.02b 38.12 ± 0.02b 48.88 ± 0.02b 10.11 ± 0.07c

77.2 ± 0.98d 24.58 ± 0.41d 14.24 ± 0.74b 17.44 ± 2.48c 18.43 ± 0.05a 219.24 ± 9.63c 55.31 ± 0.00d 35.14 ± 0.03c 35.95 ± 0.04e 16.02 ± 0.04a

682 683

HAD, hot air drying; ID, infrared drying; USV, ultrasound assisted vacuum drying; FD, freeze drying; Pg, post gastric digestion; In, a dialyzable fraction of intestinal

684

digestion; Out undialyzable fraction of intestinal digestion. Different lowercase letter in the same line indicates differences between samples subjected to different drying

685

methods (P < 0.05).

4

TPC expressed as mg GAE/100 g DM CUPRAC expressed as mg TE/100 g DM

5

28

Table 4 Change in color values of persimmon during the drying process

Parameters L* a* b* ∆E C*

Fresh persimmon 48.98 ± 0.97b 14.95 ± 1.46b 32.56 ± 2.22b 35.83b

Dried persimmon HAD ID 38.38 ± 0.78d 40.37 ± 1.90c 11.24 ± 0.78d 13.50 ± 1.15c 11.91 ± 2.38d 12.38 ± 1.76c 23.51a 21.57c 16.37d 18.63c

USV 41.78 ± 1.57c 8.51 ± 1.77e 12.21 ± 1.70c 22.53b 14.88e

FD 62.99 ± 1.36a 21.41 ± 1.35a 50.45 ± 1.28a 23.63a 54.81a

HAD, hot air drying; ID, infrared drying; USV, ultrasound assisted drying; FD, freeze drying. Different lowercase letter in the same line indicates differences between samples subjected to different drying methods (P < 0.05).

29

Table 5 The effect of different drying methods on sugar and HMF content

Methods FD ID USV HAD

Glucose (%) 27.56 ± 0.02 17.54 ± 0.01 17.87 ± 0.06 17.11 ± 0.01

Fructose (%) 28.56 ± 0.03 18.33 ± 0.03 17.20 ± 0.01 16.87 ± 0.02

HMF (mg/kg) nd 18.13 ± 0.05b 15.06 ± 0.06c 23.47 ± 0.11a

Different lowercase letter in the same column indicates differences between samples subjected to different drying methods (P < 0.05). HAD, hot air drying; ID, infrared drying; USV, ultrasound assisted drying. Nd: not detected.

30

Highlights 1.

ID and USV exhibited higher drying rate compared to conventional drying.

2.

FD, USV, and ID showed higher antioxidant capacity than conventional drying

3.

Drying methods significantly affected the distribution of phenolics.

4.

HAD and ID showed the highest bioaccessibility.

5.

ID and USV could be used as an alternative drying method.