Production of phenolic enriched mushroom powder as affected by impregnation method and air drying temperature

Journal Pre-proof Production of phenolic enriched mushroom powder as affected by impregnation method and air drying temperature Fatih Mehmet Yılmaz, Aslı Zungur Bastıoğlu PII:

S0023-6438(20)30024-4

DOI:

https://doi.org/10.1016/j.lwt.2020.109036

Reference:

YFSTL 109036

To appear in:

LWT - Food Science and Technology

Received Date: 17 May 2019 Revised Date:

13 November 2019

Accepted Date: 8 January 2020

Please cite this article as: Yılmaz, F.M., Bastıoğlu, Aslı.Zungur., Production of phenolic enriched mushroom powder as affected by impregnation method and air drying temperature, LWT - Food Science and Technology (2020), doi: https://doi.org/10.1016/j.lwt.2020.109036. 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. © 2020 Published by Elsevier Ltd.

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Production of phenolic enriched mushroom powder as affected by impregnation method

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and air drying temperature

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Fatih Mehmet Yılmaza,*, Aslı Zungur Bastıoğlua

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a

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09010, Efeler, Aydın, Turkey.

Aydın Adnan Menderes University, Engineering Faculty, Food Engineering Department,

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*Corresponding Author Tel: +90 256 213 75 03 Fax: +90 256 213 66 86

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E-mail: [email protected]

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ABSTRACT

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This study aimed to develop a functional food ingredient by incorporating grape pomace

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extract into mushroom slices using both vacuum impregnation (VI) and simultaneous

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application of ultrasound assisted vacuum impregnation (VI+US) techniques with further air

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drying at 55, 65 and 75 ˚C. Drying kinetics of processes as well as bioactive compounds and

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physical properties of mushroom powders belonging to VI and VI+US treatments were

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assessed and compared with non-treated (N-T) samples. The activation energies of drying for

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VI (27.05 kJ mol-1) and VI+US (16.24 kJ mol-1) treatments were found significantly lower

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than N-T (43.42 kJ mol-1) samples, and VI+US samples exhibited highest total phenolic and

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total flavonoid contents with highest antioxidant capacity values. Physical properties of the

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mushroom powders were affected by both impregnation techniques and air-drying

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temperatures. Impregnation treatments increased D[3,2] values (surface area mean) of

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the samples dried at higher temperatures, and the ultrasound application resulted in the

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highest values. Both VI and VI+US treatments improved flowability (Carr index)

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compared to N-T samples. The highest oil and water holding capacity values were

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determined in VI+US samples while sole VI treatment revealed lowest water holding

38

capacity.

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Keywords: Mushroom powder, vacuum impregnation, ultrasound, enrichment, grape

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pomace.

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1. Introduction

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In recent years, food industry has been heading towards to finding convenient and

43

natural additives and fortification strategies as alternative to usage of synthetic additives

44

in a variety of food applications (Choe et al., 2018). More recently, there has been a great

45

interest to using powder form of mushrooms in food technology. Mushroom powders have

46

been used as a substitute for meat (Kurt & Gençcelep, 2018), as an alternative to phosphates 2

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in meat products (Choe et al., 2018) and also for fortification of bakery products (Okafor,

48

Okafor, Ozumba, & Elemo, 2012). Specifically, Agaricus bisporus is regarded as an excellent

49

source of biologically active compounds such as prebiotics (i.e. inulin), β-glucan and

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tocopherols (Aida, Shuhaimi, Yazid, & Maaruf, 2009; Palacios et al., 2011). When

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compared to other species, even though A. bisporus is the most cultivated species in the

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world and contains higher protein content with essential amino acids (Mattila, Salo-

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Väänänen, Könkö, Aro, & Jalava, 2002); it has the minimum polyphenol contents and

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antioxidant capacity (Palacios et al., 2011).

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Grape pomace, a by-product of juice and wine-making processes, accounts for 20 – 30%

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(w w-1) of the total grapes used and approximately 70% of the phenolic compounds of

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grapes remain in the pomace (Goula, Thymiatis, & Kaderides, 2016; Xu, Burton, Kim, &

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Sismour, 2016). Numerous studies reported that grape pomace contain valuable phenolic

59

compounds mainly anthocyanins (malvidin and peonidin glycosides), procyanidins, flavan-3-

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ols (catechin, epicatechin), flavonols (rutin, quercetin, kaempferol), stilbenes (trans-

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resveratrol) and phenolic acids (ferulic acid, cinnamic acid) which exhibit anti-oxidant, anti-

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diabetic, cardio-protective and chemo-preventive effects (Drosou, Kyriakopoulou, Bimpilas,

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Tsimogiannis, & Krokida, 2015). Furthermore, several specific phenolic compounds of

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grape pomace extracts have shown strong antimicrobial properties which could be utilized

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to extend shelf life of food products in response to increasing concerns to use synthetic

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additives in food products (Xu et al., 2016).

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Latest meat technology studies have focused on reducing fat, phosphate and nitrite

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contents by considering demands of health-conscious consumers. To reach those

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purposes, dietary fiber and antioxidant-rich plant sources and/or plant extracts are

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utilized as effective substitutes (Akesowan, 2016; Kumar et al., 2017). Among these

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plants, mushroom has been used in sausage emulsion formulation as an alternative to 3

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phosphate due to its pH elevating property (Choe et al., 2018). Mushroom inclusion in

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meat formulation has been shown to retard lipid oxidation (Bao, Ushio, & Ohshima,

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2008) and more specifically, the use of mushroom powder enhanced emulsion stability

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and improved textural attributes of meat products (Kurt & Gençcelep, 2018). Besides,

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mushroom has been shown among next generation food additives due to its rich protein

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content with high biological values, dietary fiber, and essential components (Kurt &

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Gençcelep, 2018).

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Meat products are more vulnerable to oxidation due to their high lipid contents and

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harsh production methods. Studies aim to inhibit fat and protein oxidation in meat

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products by using natural and synthetic antioxidants (Cheng, Liu, Zhang, Chen, &

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Wang, 2018). The main problem in using those antioxidants is non-homogeneous

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distribution in large bulks, since they are added at considerably lower concentrations

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(ppm or ppb).

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Mixing of small amount of powders within large amount of bulks has always been a

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complex process. Although some procedures and special design equipment have been

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developed to minimize segregation and agglomeration, it could be considerably difficult to

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create a perfect mix (Ammarcha, Gatumel, Dirion, Cabassud, & Berthiaux, 2017). At this

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viewpoint, vitamins, minerals and antioxidant compounds which are relatively at low

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percentages could be hardly mixed homogeneously within large powdered bulks.

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However, vacuum impregnation represents as an effective tool allowing a rapid penetration of

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the desirable substances with a homogeneous distribution profile in the final products (Neri et

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al., 2016). Therefore, homogeneously distributed phenolic enriched mushroom powder

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could be produced using vacuum impregnation pre-treatment followed by a suitable

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drying and milling operations afterwards.

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Based on the given information, the objective of this study was to produce mushroom

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powder enriched with grape pomace phenolics as an innovative food ingredient. In this

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regard, the mushroom slices were subjected to two different pre-treatments and were dried at

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three different temperature levels. Drying kinetics of the operations were determined, and

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then bioactive and physical properties of mushroom powders were analysed and compared

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with non-treated (N-T) mushroom powders.

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2. Materials and Methods

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2.1. Materials

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Fresh mushrooms (Agaricus bisporus) were provided from PE-MA Mushroom

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Production and Trade Inc. (İzmir, Turkey) and red grape pomace (var. Vitis vinifera) was

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supplied from a local fruit juice company. The by-product discharged after pressing line

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(including seed, skin and relatively small amount of stem) was placed into polyethylene

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(PE) bags, sealed and immediately transported to laboratory at 4 - 7 °C and stored at –

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20 °C before commencement of the operations. Food grade mannitol was purchased from

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Hylen Co. Ltd. (Qingdao, China). All other chemicals were of analytical grade.

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2.2. Methods

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2.2.1. Preparation of grape pomace extract

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Grape pomace extract was prepared as described by Tournour et al. (2015) with

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some modifications. The thawed by-product was firstly dried at 45 °C in a vacuum oven

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at 16 kPa for 3 h, and then finely ground after stems were manually separated from the

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pomace (seed and skin). The pomace was mixed with 50% EtOH at 1:50 (w:v) solid to

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solvent ratio (Sant’Anna, Brandelli, Marczak, & Tessaro, 2012) in covered vessels. The

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vessels were kept in a rotary water bath operated at 50 °C and 50 rpm for 120 min. The

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supernatant fraction were collected after centrifugation at 4000g for 10 min and

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evaporated using a rotary evaporator until the total volume decreased by 90%. Finally, 5

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the remaining slurries were diluted with water and stored within jars at 4 °C (Bioactive

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properties of extract were presented in Table S1).

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2.2.2. Preparation of mushroom slices and impregnation treatments

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Mushrooms were washed, separated from roots and the caps were sliced with a knife.

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The thicknesses of sliced mushrooms measured by a digital caliper were 3.29 ± 0.08 mm.

126

The thicknesses were ensured to be the same for the consistency of the operations during

127

vacuum impregnation and drying experiments. The sliced mushrooms were separated into

128

three groups with regard to treatments: Non – treated (N-T), vacuum impregnation (VI) and

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ultrasound assisted vacuum impregnation (VI+US). For VI and VI+US treatments, sliced

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mushrooms were immersed in a solution (1:5; w:v) within the impregnation equipment

131

(Ermaksan Ultrasonics, ULT 50-S, Turkey) and were covered with a stainless steel perforated

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basket to prevent any overlap. The equipment has ultrasonic function (35 kHz), temperature -

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pressure controllers, vacuum pump, and air – solution drainage valves. The impregnation

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solution was 0.2 M mannitol including 1.8% grape pomace extract. The vacuum pressure,

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vacuum time and restoration time after vacuum were at 600 mmHg, for 10 min and 20 min,

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respectively for VI treatment. The VI+US treatment was carried out at 550 W simultaneous

137

ultrasonic application at the same conditions with VI treatment. After the treatments, the

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mushroom slices were gently drained with a tissue paper to remove any immersion

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solution lest on the surface of mushroom slices.

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2.2.3. Drying procedure

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Treated and non – treated mushroom slices with initial weights of 1255 ± 24 g for each

142

run were placed as single layer on stainless-steel perforated trays and dried in an industrial

143

tray dryer (Eksis Industrial Drying Systems, TK-10, Turkey). Operations were performed at

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55, 65 and 75 ˚C (v=1.5 m s-1; <10% RH). The conducted temperature levels, air velocity

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and maximum relative humidity inside the dryer were decided based on published 6

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studies and by aiming to simulate industrial applications. During drying, weight losses

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were recorded at 5 min time intervals using a sensitive scale. Drying was ended when

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samples reached 0.15 kg water kg-1 dry matter. The samples were then milled using a

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grinder (Homend, Turkey) with 6 times of 10 sec on 10 sec off mode. The powder samples

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were then transferred to glass jars, vacuum sealed (Takaje, Italy) and stored at 4 ˚C until

151

analyses.

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2.3. Analyses

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2.3.1. Determination of effective moisture diffusivity and activation energy

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The adapted Fick’s diffusion equation for slab geometries is as follows (Crank, 1975):

=

( − ( −

) 8 = exp(− )

)

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Where X is moisture content at any time (kg H2O kg-1 dry solid), X0 is initial moisture

156

content (kg H2O kg-1 dry solid), Xe is equilibrum moisture content (kg H2O kg-1 dry solid),

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Deff is effective moisture diffusivity (m2.s-1), L is slab thickness (m) and t is time in minute. In

158

this equation, the moisture ratio was simplified to X/X0 instead of (X – Xe)/(X0 – Xe) as the Xe

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is relatively small compared to X or X0 (Kingsly & Singh, 2007).

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Plotting of ln(MR) versus time serves calculation of the effective moisture diffusivity (Deff) and a straight line can be obtained with a slope of ( ) as expressed below:

= 162 163

Activation energy for diffusion was determined from the slope of Arrhenius-type equation:

=

(−

7

E

)

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Where D0 is the pre-exponential factor of the Arrhenius equation (m2.s-1), Ea is the

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activation energy (kJ.mol-1), R is the universal gas constant (kJ.mol-1.K-1), and T is the

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absolute temperature (K).

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2.3.2. Determination of total phenolic (TP) contents total flavonoid (TF) contents and

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antioxidant capacities

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Sliced and powdered mushrooms were subjected to extraction prior to analyses. The

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samples were mixed with 50% EtOH solution (0.1% HCl), crushed using Ultraturrax (6000

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rpm, 1 min) and diluted with the extraction solution at a ratio of 1:5 and 1:20 (w:v) for sliced

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and powdered samples, respectively. The slurries were then transferred to covered extraction

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vessels and placed in a water bath for 60 min which was operated at 55 ˚C and at 50 rpm.

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After centrifugation at 4800g for 6 min, the supernatants were collected in falcon tubes and

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stored at 4 ˚C for analyses. TP contents were determined using Folin-Ciocalteu method as

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described by Yılmaz & Ersus Bilek (2018) and results were expressed as mg gallic acid

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equivalent per g dry weight sample (mg GAE g-1 d.b.). TF contents were determined using

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colorimetric method suggested by Kim, Jeong, & Lee (2003) and results were expressed as

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mg catechin equivalent per g dry weight sample (mg CE g-1 d.b.). Trolox equivalent

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antioxidant capacity (TEAC) values were determined with both DPPH and TEAC methods as

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described by Görgüç, Bircan, & Yılmaz (2019) and results were expressed as µmol trolox

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equivalent (TE) per g dry weight basis sample.

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2.3.3. Determination of moisture content and water activity

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Moisture contents of mushroom samples were determined using a vacuum oven (Nüve

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EV 018, Turkey) operated at 70 °C & 16 kPa absolute pressure (AOAC, 1990). The water

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activity (aw) values were measured at 25 ˚C with a water activity measurement device (Testo

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AG 645, Germany).

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2.3.4. Color values

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The Hunter L*, a*, b* values of mushroom powders were measured with a Chroma

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meter (Minolta CR-300, Minolta, Tokyo, Japan). The Chroma (C*) and hue (h°) values were

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determined using the following equations:

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C* = (a*2 + b*2)1/2

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h° = arctan(b*/a*)

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2.3.5. Particle size

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Particle sizes of the mushroom powders were determined by light scattering

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method using a Mastersizer 2000 (Malvern, UK). The particle size (µm) was expressed

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as surface area mean (Sauter mean diameter; D[3,2]), and was calculated as follows: ∑ 12 3,2

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*[,, .] = ∑

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where ni is the number of particles of diameter di.

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12 3.2

2.3.6. Bulk and tapped density

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The bulk density (ρbulk) was calculated by dividing the weight of the mushroom powder

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(2 g) to the volume occupied in a graduated cylinder (10 mL). For the tapped density (ρtap),

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the cylinder was tapped steadily and continuously on the surface by hand until there was no

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further change in volume observed (Jinapong, Suphantharika, & Jamnong, 2008).

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2.3.7. Carr index (flowability)

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Carr index (CI) was calculated by the following equation (Carr, 1965): 45 =

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6789 − 6:;<= 100 6789

2.3.8. Water-holding and oil-holding capacities

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Water-holding capacity (WHC) and oil-holding capacity (OHC) of mushroom

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powders were determined according to methods of Ahmedna, Prinyawiwatkul, & Rao (1999).

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A 5 g powdered mushroom sample was weighed into a 50 mL pre-weighed centrifuge tube.

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For each sample, deionized water was added in small increments under continuous stirring

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with a glass rod till the mixture was thoroughly wetted. Samples were centrifuged (1000g) for

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5 min, the supernatant was decanted, and the test tube with sediment was weighed. WHC (g

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water g-1 sample) was calculated as;

?@4 =

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(? − ?A ) ?

Where W0 is the weight of the dry sample (g), W1 is the weight of the tube plus the dry sample (g), and W2 is the weight of the tube plus the sediment (g).

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For OHC, a 1 g of mushroom sample was weighed into a 50 mL pre-weighed

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centrifuge tube and thoroughly mixed with 10 mL of sunflower oil. The mixture was

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centrifuged at 2000g for 5 min. The supernatant was carefully removed, and the tube was

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weighed. OHC (g oil g-1 sample) was calculated as;

BCD =

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(E − EA ) E

Where F0 is the weight of the dry sample (g), F1 is the weight of the tube plus the dry

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sample (g), and F2 is the weight of the tube plus the sediment (g).

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2.4. Statistical analysis

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The procedures for powdered mushroom production were replicated three times

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and all analyses were carried out triplicate. Results were presented as mean ± standard

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deviation. Experimental data were subjected to analysis of variance (ANOVA) using SPSS

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version 20.0 (SPSS Inc., Chicago, IL, USA) and the P values less than 0.05 were taken into

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consideration. Duncan test was used as Post Hoc test after applying homogeneity test. 10

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3. Results and discussion

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3.1. The effects of impregnation treatments and temperature on drying rate

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The initial moisture content of fresh untreated mushroom was 9.37 kg water kg-1 dry

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matter and it has slightly decreased to 8.81 and 7.27 kg water kg-1 dry matter after vacuum

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(VI) and combined ultrasound assisted vacuum impregnation (VI+US) treatments,

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respectively. The decrements could likely be due to moisture removal with the effect of

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treatments and also due to the passage of impregnation solutes through the tissues. The effects

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of impregnation treatments and temperature on drying curves of sliced mushrooms during

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drying were depicted in Fig. 1.

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The moisture ratio (MR) values decreased exponentially in all cases and decreased

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faster in the samples treated with VI and VI+US. Results showed that drying times decreased

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greatly when the impregnation treatments were applied. According to results in Fig. 1 and

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Table 1, the highest moisture removal rates belonged to VI+US samples at all drying

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temperature levels examined. The vacuum application before drying alters the pores within

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tissues and thus influences the moisture removal rate from fruits and vegetables (Sulistyawati,

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Dekker, Fogliano, & Verkerk, 2018). The structural effect of VI is explained by

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hydrodynamic mechanism (HDM) and deformation relaxation phenomena (DRP) which take

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place at vacuum and restoration period. During vacuum period, the pores expand and gas

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output takes place. In the restoration period (at atmospheric pressure) after vacuum, the

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channels fill with the impregnation solution by pressure difference as driving force

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(Sulistyawati et al., 2018). The results of this study support the structural alteration of

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mushroom tissues as VI application led to higher Deff values (Table 1). The Deff values of N-

251

T, VI and VI+US samples dried at 55 ˚C were 2.14, 3.24 and 4.66 x 10-6 m2 s-1, respectively,

252

and there were concomitant increases in temperature and Deff values for all the treatments

253

(Table 1). 11

254

The activation energies of drying for different treatments were calculated using

255

Arrhenius approach by plotting ln(Deff) versus reciprocal of absolute temperature (Fig. 2). The

256

activation energies and corresponding R2 values were given in Table 1. The activation

257

energies were 43.42 kJ mol-1 for the N-T, 27.05 kJ mol-1 for VI and 16.24 kJ mol-1 for

258

VI+US. VI and VI+US treatments brought about significant decreases in the activation

259

energies. Furthermore, it is clear from the data presented in this study that ultrasound

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application had more facilitating effect on drying kinetics compared to sole VI treatment. The

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facilitating role of ultrasound could be explained by cavitation and sponge effect phenomena

262

(Rodríguez et al., 2018). The formed and collapsed bubbles could act on deformed channels

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within the intact tissues simultaneously with vacuum. Studies also showed that ultrasonic

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waves create micro channels in the plant tissues, and thus, water could use these micro

265

channels as an easier pathway to diffuse toward the surface (Dehghannya, Gorbani, &

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Ghanbarzadeh, 2015).

267

3.2.

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powders

The effect of impregnation treatments on bioactive properties of mushroom

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The average TP and TF contents of the untreated mushroom were 6.99 mg GAE g-1

270

(d.b.) and 1.32 mg CE g-1 (d.b.), respectively. The TP and TF contents of the A. bisporus

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species were comparable with previously published data (Gąsecka, Magdziak, Siwulski, &

272

Mleczek, 2018; Palacios et al., 2011). The TP contents increased to 8.66 and 10.83 mg GAE

273

g-1 (d.b.) when sliced mushrooms were treated with VI and VI+US, respectively in the

274

presence of grape pomace extract. TF contents increased to 3.50 and 4.44 mg CE g-1 (d.b.)

275

after the same treatments. In parallel to TP and TF contents, both TEAC values obtained with

276

DPPH and ABTS assays significantly increased (P<0.05) after enrichment operations (Table

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2). According to results of analyses, ultrasound facilitated the infusion of more bioactive

278

compounds into mushroom tissue compared to N-T samples. The effectiveness of ultrasound 12

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could be explained by its acting on HDM and DRP. In HDM, the capillaries would expand

280

more with the collapsed bubbles, and thus, more trapped gas outlet would happen. Therefore,

281

more compounds would infuse through capillaries (Yılmaz & Ersus Bilek, 2018). In addition,

282

mass transfer rate would even increase by the oscillatory motion of sound waves which

283

cause acoustic streaming (Deng & Zhao, 2008). Similar observations were reported by other

284

studies as ultrasound application increased the passage of curcumin into banana slices

285

(Bellary & Rastogi, 2014), aroma compounds into apple sticks (Comandini, Blanda, Mújica

286

Paz, Valdez Fragoso, & Gallina Toschi, 2010) and phenolic compounds into apple disks

287

(Yılmaz & Ersus Bilek, 2018) compared to solely VI application. The US application created

288

forced mass transfer during VI operations that facilitate the passage of useful compounds.

289

Studies showed that VI operations with phenolic-free impregnation solution lead to decrease

290

in bioactive compounds mainly due to the leaching (Yılmaz & Ersus Bilek, 2017). The TP

291

contents, TF contents and TEAC values of mushroom slices in this study also decreased

292

when VI operations were carried out in the absence of grape pomace extracts (Data not

293

shown). However, the bioactive properties of mushroom samples significantly increased

294

(P<0.05) in the presence of grape pomace extract.

295

The TP contents, TF contents and TEAC values of mushrooms were affected by

296

drying operation independent of process temperature. The drying temperature and time

297

combination mutually affected the degradation rate of bioactive compounds. While drying

298

temperature increased from 55 to 75 ˚C, drying times significantly decreased (Table 1)

299

which would also lead to protect bioactive compounds from thermal effect. Moreover,

300

elevated drying temperature (>70 ˚C) would rapidly inactivate polyphenol oxidase (Gao, Wu,

301

Wang, Xu, & Du, 2012) which may be linked to non-destructive effect of higher temperature

302

levels in this study. There are numerous published data showing the effect of drying

303

temperature on degradation rate of bioactive compounds in plant tissues as increasing

13

304

temperature causes lower retention (Karaaslan et al., 2014), and contrary to that, increasing

305

temperature may lead to higher retention as a result of lowering process time (Uslu Demir,

306

Atalay, & Erge, 2019). Similar to results in this study, Nóbrega, Oliveira, Genovese, &

307

Correia (2015) and Kayacan, Sagdic, & Doymaz (2018) showed that bioactive compounds

308

were not affected mainly from increasing temperature. They concluded that temperature

309

and time profile determine the retention of antioxidant compounds. The retention

310

percentages of TF (57 – 75%) were considerably lower than TP (73 – 85%) in mushroom

311

powders. The flavonoids, subgroup of phenolics, are known to be more susceptible to thermal

312

effects mainly due to the structural differences (van der Sluis, Dekker, & van Boekel, 2005).

313

In addition, the VI and VI+US samples displayed relatively higher degradation rates of

314

bioactive compounds compared to N-T samples. For example, The TF retentions of VI and

315

VI+US samples were in the range between 57 and 64%, while N-T samples had 62 – 75% TF

316

retention at three different temperature levels. This may be due to the applied treatments prior

317

to the drying operations. The antioxidant compounds stored in cytoplasm would be more

318

vulnerable to heat as a result of deteriorations in cellular structure (de Torres, Díaz-Maroto,

319

Hermosín-Gutiérrez, & Pérez-Coello, 2010). The stored compounds within intracellular

320

structure would also be exposed to encounter polyphenol oxidase enzyme after treatments,

321

which may also cause degradation. Another possible explanation is that large percentages of

322

phenolic compounds are found in bound form with other structures within cells (Wojdyło,

323

Figiel, Lech, Nowicka, & Oszmiański, 2014) and grape pomace phenolics, as a free form,

324

would undergo more deterioration.

325

TP and TF contents seem to be good indicators of the antioxidant potentials and

326

several authors have reported correlations among these parameters (Slatnar, Klancar, Stampar,

327

& Veberic, 2011) which were also confirmed by this study. There were significant

14

328

correlations (P<0.01) among TP, TF, TEACDPPH and TEACABTS values for all of the Pearson

329

correlation analyses.

330

3.3. The effect of impregnation treatments and drying temperature on physical

331

properties

332

Moisture content and water activity of powder products are important properties which

333

have direct effects on other physical and chemical properties. They also determine stability of

334

a food material directly (Mohamad Saad et al., 2009). Moisture content and aw of mushroom

335

powders varied within the range of 13.08 - 13.94% (wet basis) and 0.60 - 0.64, respectively

336

(Table 3). Moisture content of the N-T mushroom powder dried at 55 °C had the lowest

337

value. However, as drying temperature increased to 65 and 75 °C, the moisture contents of

338

the pre-treated samples were lower than the N-T samples (P<0.05). The short drying time

339

with increasing drying temperature would lead to this result. In addition, the pores of the

340

mushroom slices would expand with the applied pre-treatments and the water movement from

341

the product would be facilitated. Studies showed that heat and mass transfer of air-drying

342

processes increase with vacuum impregnation (Castagnini, Betoret, Betoret, & Fito, 2015).

343

The drying temperature had no significant effect on aw values of VI and VI+US samples

344

(P>0.05). N-T samples had relatively lower aw values compared to treated samples at

345

each temperature (P<0.05). The aw values of mushroom powders were at acceptable level as

346

considering bacterial growth and aw relationship (Tang & Yang, 2004).

347

Impregnation treatments also affected colour values of samples. Anthocyanin

348

transferred to the mushroom slices resulted a decrease in L* values and increase in a* values

349

of the pre-treated samples (Table 3). Chroma (C*) values of the N-T samples were found

350

lower than pre-treated samples, but opposite situation was observed for hue (h°) values at all

351

temperatures examined. The decrease in L* and increase in C* values indicate increasing

352

colour intensity caused by incorporation of grape pomace extract into mushroom 15

353

powder. Similar to this result, Duangmal, Saicheua, & Sueeprasan (2008) reported that C*

354

value is strongly correlated to amount of anthocyanin. The observed higher a* with lower h°

355

values in pre-treated samples may also be directly related to anthocyanin pigment. VI+US

356

samples exhibited lower h° value than VI samples at 55 °C possibly due to better infusion of

357

anthocyanin towards mushroom slices. However, at 65 and 75 °C, VI+US samples had

358

relatively lower a* values and higher h° values compared to VI samples. That may be

359

because anthocyanins as being sub-groups of phenolic compounds and flavonoids are more

360

vulnerable to thermal effects (Karaaslan et al., 2014).

361

Particle sizes of mushroom powders ranged between 118 and 356 µm (Table 4). Both

362

temperature and treatments affected the final particle sizes of the powders (P<0.05). The

363

drying temperature increments led to increase in particle size of samples in all

364

treatments. Particles sizes of the VI+US samples were highest followed by VI and N-T

365

samples at each temperature, except for the samples treated at 55 ˚C. The faster drying

366

rates could enable the larger particle sizes than slower drying. Ultrasound application

367

combined with fast drying at high temperatures resulted in the highest particle sizes in

368

this study.

369

The bulk properties (bulk and tapped density, flowability) of mushroom powders were

370

presented in Table 4. Both bulk and tapped densities are important features for classification

371

of powdered foods (Zhao, Yang, Gai, & Yang, 2009). Bulk and tapped densities of

372

mushroom powders changed between 455 and 592 kg m-3, and 560 and 682 kg m-3,

373

respectively (Table 4). Bulk density of the N-T samples at 55 °C was lower than other

374

samples, but the bulk density of the pre-treated samples was found higher than N-T samples at

375

higher drying temperatures (at 65 and 75 °C). The applied vacuum impregnation and

376

ultrasound treatments in combination with increasing temperature would cause changes in

377

surface morphology, and may lead to increase in the surface area of the products (Magalhães 16

378

et al., 2017; Schulze, Hubbermann, & Schwarz, 2014); thus, it has resulted in different

379

bulk and tapped densities of the powdered products.

380

Carr index (CI) values represent the flowability properties of powders and high CI values

381

indicate that powder has poor flowability (Carr, 1965). According to Santhalakshmy, Don

382

Bosco, Francis, & Sabeena (2015), the classification of powder flowability based on Carr

383

index (CI) are as follows: Very good (<15), good (15–20), fair (20–35), bad (35–45), and

384

very bad (>45). According to the results, VI and VI+US samples had better flowability than

385

N-T samples. Flowability of food powders could easily be influenced by the surface

386

composition and structure (Ghodki & Goswami, 2016) which support effectiveness of pre-

387

treatments applied in this study.

388

Oil and water holding capacities of mushroom powders were presented in Table 4.

389

VI+US samples had higher OHC and WHC than other samples (P<0.05). OHC and WHC

390

strongly depend on chemical and physical structures of the powders (Dana & Saguy, 2006)

391

and they are also related with particle size. VI+US treatment led to highest OHC and WHC

392

while VI resulted lowest WHC at all temperature levels. Food additives having higher OHC

393

and WHC values are favourable for emulsion type food commodities to increase their

394

stability and to improve their textural attributes (Ağar, Gençcelep, Saricaoğlu, &

395

Turhan, 2016; Kurt & Gençcelep, 2018). OHC values obtained in this study were in

396

agreement with previously published data which were about food additives prepared for

397

food emulsion (Afoakwah et al., 2015; Alfredo, Gabriel, Luis, & David, 2009) On the

398

contrary, literature findings (Afoakwah et al., 2015; Alfredo et al., 2009; Chau &

399

Huang, 2003) exhibited higher WHC values (5.21, 10.85, 15.41 and 16.7 g g-1 sample)

400

compared to our study (1.04 – 2.05 g g-1 sample) which could be linked to nature of the

401

mushroom. However, results of this study showed that VI+US treatment could increase

402

WHC values of mushroom powders to some extent. 17

403

4. Conclusions

404

The applied pre-treatments for enrichment purposes in this study had dual role by facilitating

405

drying kinetics and by providing higher bioactive contents with better physical properties. The

406

simultaneous application of ultrasound assisted vacuum impregnation seemed to be

407

convenient treatment as considering enhanced bioactive and physical properties of mushroom

408

powders. The developed phenolic enriched mushroom powder could be utilized in food

409

emulsion systems when new formulations were intended to be enriched by both

410

mushroom and antioxidant compounds. By this way, small proportion of grape pomace

411

extract within mushroom powders could be homogeneously distributed in the new

412

formulas. Future research is needed in the future to determine effects of phenolic enriched

413

mushroom powders within different formulations such as meat, bakery and dairy products.

414

Results of this study could be an insight to researchers and food technologist who would like

415

to carry out studies on similar subjects.

416

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Figure Captions Fig. 1. The effects of impregnation treatments and air-drying temperature on drying curves of mushroom slices (N-T: non-treated; VI: Vacuum impregnation; VI+US: Ultrasound assisted vacuum impregnation) at different temperatures (Circle, triangular, and diamond markers indicate 55, 65, and 75 ºC, respectively; while black, gray, and white marker face colors represent N-T, VI, and VI+US, respectively). Fig. 2. Arrhenius-type relationship between effective moisture diffusivity (Deff) and reciprocal absolute temperature (Triangular marker represents VI+US, circle markers with black and white face colors represent N-T and VI, respectively; while solid lines indicate the prediction of the model).

Table 1. The effects of treatments (N-T: non-treated; VI: Vacuum impregnation; VI+US: Ultrasound assisted vacuum impregnation) and air - drying temperature on drying time, effective moisture diffusivity (Deff), and activation energy (Ea) values.

Treatment N-T

VI

VI+US

Temperature (°C) 55 65 75 55 65 75 55 65 75

Drying time (min) 200 145 115 125 110 100 110 85 80

Deff (m2 s-1) 2.14 × 10-6 3.75 × 10-6 5.33 × 10-6 3.24 × 10-6 4.16 × 10-6 5.73 × 10-6 4.66 × 10-6 5.44 × 10-6 6.57 × 10-6

Ea (kJ mol-1)

R2

43.42

0.9872

27.05

0.9928

16.24

0.9944

Table 2. Total phenolic (TP), total flavonoid (TF) contents and trolox equivalent antioxidant capacity (TEAC) values of mushroom slices and powders as affected by impregnation treatment and air-drying temperature (N-T: non-treated; VI: Vacuum impregnation; VI+US: Ultrasound assisted vacuum impregnation)*. N-T

VI TP (mg GAE g-1 d.b.) 6.99 ± 0.82a,C 8.66 ± 0.64b,C Before drying a,A 5.07 ± 0.12 7.33 ± 0.33b,B 55 ºC a,B 5.31 ± 0.17 7.08 ± 0.32b,AB 65 ºC a,A 5.10 ± 0.11 6.82 ± 0.09b,A 75 ºC TF (mg CE g-1 d.b.) a,C 1.32 ± 0.06 3.50 ± 0.03b,B Before drying a,A 0.83 ± 0.01 2.05 ± 0.09b,A 55 ºC a,B 2.11 ± 0.20b,A 0.95 ± 0.11 65 ºC a,B 0.99 ± 0.02 1.98 ± 0.09b,A 75 ºC TEACDPPH (µmol TE g-1 d.b.) a,D 9.88 ± 0.36 13.56 ± 0.10b,B Before drying a,B 3.75 ± 0.06 4.47 ± 0.03b,A 55 ºC a,C 3.84 ± 0.04 4.52 ± 0.10b,A 65 ºC a,A 3.48 ± 0.07 4.49 ± 0.05b,A 75 ºC TEACABTS (µmol TE g-1 d.b.) a,B Before drying 150 ± 15 199 ± 13b,B a,A 55 ºC 86 ± 10 154 ± 9b,A a,A 65 ºC 97 ± 15 155 ± 8b,A a,A 75 ºC 93 ± 6 140 ± 4b,A *Data were represented as mean ± standard deviation.

VI+US 10.83 ± 0.72c,C 8.62 ± 0.07c,B 8.57 ± 0.17c,B 8.16 ± 0.20c,A 4.44 ± 0.19c,C 2.54 ± 0.07c,A 2.86 ± 0.10c,B 2.75 ± 0.10c,B 15.24 ± 0.16c,C 5.25 ± 0.04c,B 5.17 ± 0.07c,B 5.04 ± 0.07c,A 248 ± 24c,B 212 ± 6c,A 210 ± 6c,A 199 ± 11c,A

d.b.: dry weight basis. Different small letters (a, b, c) in each row of analysis indicate statistically significant (P<0.05) differences among treatments. Different capital letters (A, B, C) in each column of analysis indicate statistically significant (P<0.05) differences among temperature levels.

Table 3. Moisture content (MC), water activity (aw) and colour properties of mushroom powders as affected by impregnation treatment and air-drying temperature (N-T: non-treated; VI: Vacuum impregnation; VI+US: Ultrasound assisted vacuum impregnation)*. N-T

VI MC (% w.b.) 13.08 ± 0.04a,A 13.50 ± 0.14c,B 55 ºC b,C 13.94 ± 0.20 13.54 ± 0.34a,B 65 ºC c,B 13.57 ± 0.04 13.42 ± 0.71b,A 75 ºC aw 0.60 ± 0.00a,A 0.63 ± 0.02b 55 ºC a,B 0.61 ± 0.00 0.64 ± 0.01b 65 ºC a,B 0.61 ± 0.01 0.63 ± 0.00c 75 ºC L* 62.5 ± 0.2b,A 57.5 ± 0.2a,C 55 ºC b,A 55.6 ± 0.1a,A 61.1 ± 0.1 65 ºC b,B 56.7 ± 0.1a,B 66.0 ± 0.2 75 ºC a* a,B 3.4 ± 0.1 6.6 ± 0.1b,A 55 ºC a,B 3.4 ± 7 7.0 ± 0.1b,B 65 ºC a,A 7.1 ± 0.2b,B 3.1 ± 8 75 ºC b* 17.4 ± 0.1b,A 16.9 ± 0.1a,B 55 ºC a,AB 16.3 ± 0.0 18.5 ± 0.2b,B 65 ºC a,A 16.0 ± 0.0 19.5 ± 0.1b,C 75 ºC C* 17.2 ± 0.1a,B 18.6 ± 0.1ab,A 55 ºC a,AB 16.7 ± 0.0 19.8 ± 0.2b,B 65 ºC a,A 16.3 ± 0.0 20.7 ± 0.1b,C 75 ºC h° 78.5 ± 0.3b,B 69.4 ± 0.3a,A 55 ºC b,A 78.1 ± 0.2 69.2 ± 0.0a,A 65 ºC b,C 70.6 ± 0.2a,B 78.9 ± 0.1 75 ºC *Data were represented as mean ± standard deviation.

VI+US 13.23 ± 0.76b,B 13.52 ± 0.15a,C 13.12 ± 0.41a,A 0.63 ± 0.00b 0.63 ± 0.02ab 0.62 ± 0.00b 59.0 ± 0.2ab,A 61.5 ± 0.3b,B 58.6 ± 0.3a,A 6.9 ± 0.0b,B 6.2 ± 0.1b,A 6.9 ± 0.1b,B 17.5 ± 0.1b,A 18.8 ± 0.1b,B 21.8 ± 0.1c,C 18.8 ± 0.1b,A 19.8 ± 0.1b,B 23.0 ± 0.1c,C 68.4 ± 0.1a,A 71.7 ± 0.2a,B 71.9 ± 0.3a,B

w.b.: wet weight basis. Different small letters (a, b, c) in each row of analysis indicate statistically significant (P<0.05) differences among treatments. Different capital letters (A, B, C) in each column of analysis indicate statistically significant (P<0.05) differences among temperature levels.

Table 4. Bulk properties, oil holding capacity (OHC), water holding capacity (WHC) and surface mean diameter (D[3, 2]) values of mushroom powders as affected by impregnation treatment and air-drying temperature (N-T: non-treated; VI: Vacuum impregnation; VI+US: Ultrasound assisted vacuum impregnation)*. N-T

VI ρbulk (kg m-3) 55 ºC 521 ± 6b,B 502 ± 5a,A a,A 65 ºC 455 ± 6 504 ± 2b,A a,A 75 ºC 461 ± 6 512 ± 2b,B ρtap (kg m-3) b,B 55 ºC 603 ± 7 567 ± 8a a,A 65 ºC 575 ± 7 563 ± 9a b,C 75 ºC 649 ± 8 575 ± 13a CI 55 ºC 13.6 ± 1.5b,A 11.5 ± 2.1ab c,B 65 ºC 20.8 ± 0.3 10.6 ± 1.1a b,C 75 ºC 28.9 ± 0.0 10.8 ± 2.2a -1 OHC (g g sample) 2.26 ± 0.16a,B 2.38 ± 0.09ab,B 55 ºC a,A 1.88 ± 0.03 1.91 ± 0.14a,A 65 ºC a,A 1.94 ± 0.10 2.23 ± 0.20b,B 75 ºC -1 WHC (g g sample) 1.28 ± 0.01b, B 1.13 ± 0.00a,C 55 ºC b,B 1.24 ± 0.07 1.07 ± 0.00a,B 65 ºC b, A 1.16 ± 0.04 1.04 ± 0.01a,A 75 ºC D[3, 2] (µm) 118 ± 11a,A 131 ± 12b,A 55 ºC a,B 160 ± 15 223 ± 20b,B 65 ºC a,C 253 ± 16 314 ± 28b,C 75 ºC *Data were represented as mean ± standard deviation.

VI+US 514 ± 8ab,A 592 ± 10c,B 506 ± 1b,A 560 ± 5a,A 682 ± 9b,B 562 ± 2a,A 8.1 ± 1.9a,A 13.2 ± 0.9b,B 9.9 ± 0.1a,A 2.42 ± 0.05b,B 2.32 ± 0.10b,AB 2.25 ± 0.11b,A 2.05 ± 0.04c,B 1.97 ± 0.04c,B 1.85 ± 0.11c,A 124 ± 10ab,A 292 ± 13c,B 356 ± 22c,C

Different small letters (a, b, c) in each row of analysis indicate statistically significant (P<0.05) differences among treatments. Different capital letters (A, B, C) in each column of analysis indicate statistically significant (P<0.05) differences among temperature levels.

Fig. 1.

Moisture Ratio (MR)

In (Deff)

Fig. 2.

Highlights •

Phenolic enriched mushroom powders were produced using grape pomace extract.

•

Bioactive and physical properties of mushroom powders were analysed.

•

Impregnation treatments had significant effects on drying kinetics and product qualities.

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VI+US treatment revealed highest phenolic compounds and antioxidant capacities.

•

VI+US treatment enhanced bulk properties and water/oil holding capacities.

Declaration of interests ☒ 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. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: