




































Agriculture and Food 

Sciences Research 
ISSN: 2411-6653 
Vol. 2, No. 2, 51-55, 2015 
http://www.asianonlinejournals.com/index.php/AESR 

  

 

* Corresponding Author 

 

 

51 

 

Effects of Drying Methods on Physico-Chemical Properties 

and Antioxidant Activity of Shiitake Mushrooms (Lentinus 

Edodes) 
 

Jiang-Lian Duan
1
 --- Jian-Guo Xu

2* 

 
1,2

College of Food Science, Shanxi Normal University, Linfen, Shanxi, China 

 

Abstract 
 

 

 

 

 

 

 

 

 

 

 

 

 
 

 

 
This work is licensed under a Creative Commons Attribution 3.0 License 

Asian Online Journal Publishing Group 

 

Contents 
1. Introduction ............................................................................................................................................................................... 52 

2. Materials and Methods ............................................................................................................................................................. 52 

3. Results ........................................................................................................................................................................................ 53 

4. Conclusions ................................................................................................................................................................................ 54 

References ...................................................................................................................................................................................... 54 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The effects of different drying methods including natural air-drying (ND), hot air drying (HD), vacuum 

drying (VD), microwave drying (MD), infra-red drying (ID), and freeze drying (FD) on physico-

chemical properties and antioxidant activities of shiitake mushroom were investigated in this paper. The 

results showed that drying methods had obvious effects on the color, proximate chemical compositions, 

total phenolics, antioxidant activity of shiitake mushroom. The FD and ND products exhibited the best 

rehydration and shrinkage ratio; the effect of FD on color was the least, followed by ND, while MD and 

ID influenced significantly the color of mushroom; six drying methods had no effects on the content of 

ash, crude fat and carbohydrate of shiitake mushroom. Drying resulted in the decrease of total phenolic 

content and antioxidant activity of shiitake mushroom. Among them, the mushroom dried with FD had 

no obvious changes compared with fresh mushroom. 

 
    Keywords: Lentinus edodes, Drying, Physical property, Chemical property, Phenolics, Antioxidant activity. 

 

 

http://creativecommons.org/licenses/by/3.0/


Agriculture and Food Sciences Research, 2015, 2(2): 51-55 

 

 

 

 

52 

 

1. Introduction 
In recent years, mushrooms are favorable all over the world not only because of their texture and flavour, their 

chemical, nutritional and functional properties such as antiallergic, antiatherogenic, antihypoglycemic properties are 

also well documented [1, 2]. Shiitake mushroom (Lentinus edodes) is a good source of nutrition because of its higher 

protein, dietary fibers and important mineral contents [3]. Besides, shiitake mushroom contains many different 

phytochemical contents such as phenolic compounds, tocopherols, ascorbic acid and carotenoids [4]. Therefore, 

mushroom (L. edodes) is a healthy food in our daily diet. 

However, the shelf life of shiitake mushroom is short because of its high respiration rate, tendency to turn brown 

and having no physical protection to avoid water loss or microbial attack [5]. As a result, it is necessary to find a 

method to extend their shelf life. Drying is the most common method for preserving mushrooms, but different drying 

methods have different effects on the quality of the products because of differences in characteristics and mechanism 

of drying and materials [6-8]. The effects of different drying methods including natural air-drying (ND), hot air 

drying (HD), vacuum drying (VD), microwave drying (MD), infra-red drying (ID), and freeze drying (FD) on 

physico-chemical properties and antioxidant activities of shiitake mushroom are investigated in this paper, which 

would provide some foundational information for the developing and application of shiitake mushroom. 

 

2. Materials and Methods 
2.1. Raw Materials 

Fresh mushrooms (Lentinus edodes) were purchased form local market in Linfen, China on May 8, 2014. The 

mushrooms with homogeneous color and size were selected and stored in a refrigerator maintained at 4
 o

C. The 

average initial moisture content of these mushroom samples was 88.4 ± 1.2% (w/w), as determined using a hot air 

oven at 105
 o
C. 

 

2.2. Sample Preparation and Drying 
The middle sections of mushrooms were sliced and then were divided into seven portions (accurately 250 g of 

each) at random. One of the samples was stored at 4 
o
C for further use, and other portions were dried by different 

methods in optimised conditions until the final moisture content was less than 10 % (w/w), respectively. Detailed 

procedures for each drying method are described below: (a) natural air-drying (ND) at 23–30 °C by sunshine and 

flowing air; (b) hot air drying (HD) at 45 °C; (c) microwave drying (MD) in a microwave oven at 240 W; (d) vacuum 

drying (VD) in a vacuum drying oven at 45 °C and vacuum of 0.08 MPa; (e) infra-red drying (ID) in an IR moisture 

analyzer at 45 °C; (f) freeze drying (FD) in a freeze drier at 20 °C with the condenser temperature and chamber 

vacuum at -55 °C and 30 Pa. The dried samples were packaged in aluminum foil bags for further quality analysis. 

 

2.3. Rehydration Ratio (RR) 
The RR of dried mushroom was determined by immersing the dried samples in distilled water (50 mL of water 

per gram of mushroom) at room temperature for 30 min. Following this, the samples were taken out from the water, 

and the excess water was removed from the surface using a dry blotting paper and the mass of the samples was 

measured. The RR was calculated according to the formula [9] RR= (W1-W0)/Wo, where W1 and Wo are the mass 

values of the rehydrated and dried samples, respectively. The RR values were determined in triplicate. 

 

2.4. Shrinkage Ratio 
The volume of the test sample was measured using an excluding method, and the clean sea sand was selected as 

filling material [10]. The mean particle diameter of sand is about 0.6 mm. Five replicates were performed for each 

sample and mean value was calculated. The shrinkage ratio was calculated as: RS (%)=100×(V0−V1)/V0, where RS is 

the shrinkage ratio of the sample, V0 is the initial volume of the sample before drying, V1 is the volume of the dried 

sample. 

 

2.5. Surface Colour Measurement 
The colour of sample was measured through the CIE L*a*b* system using a CR-330 Minolta Colorimeter 

(Minolta, Ramsey, NJ) calibrated with a white standard tile. The results were expressed as Hunter colour values of 

L*, a* and b*, where L* was used to denote lightness, a* redness and greenness, and b* yellowness and blueness. 

Hunter values of the fresh and dried samples were measured in triplicate. 

 

2.6. Chemical Analysis 
The crude protein, fat, fibre and ash were determined following the AOAC procedures [11]. The crude protein 

content (N×4.38) of the samples was estimated by the macro-Kjeldahl method; the crude fat was determined by 

extracting a known weight of the sample with petroleum ether, using a Soxhlet apparatus; the crude fibre was 

estimated by acid/alkaline hydrolysis of insoluble residues; the ash content was determined by incineration at 600±15 

°C; the carbohydrate content was calculated by subtracting the other proximate compounds from 1 g dry sample. The 

content of all compositions are expressed as grams per 100 gram dry matter basis (DM). 

 

2.7. Antioxidant Activity 

2.7.1. Determination of Total Phenolic Content (TPC) 
The ground samples are blended with methanol and shaken at 25 °C at 150 rpm for 2 h, and then the 

homogenates are centrifuged for 15 min at 4 
o
C and 5 000 g. After centrifugation, the supernatants are vacuum-

evaporated to dryness at 40 
o
C, redissolved in methanol at 10 mg/mL, and stored at 4 

o
C for further use.  



Agriculture and Food Sciences Research, 2015, 2(2): 51-55 

 

 

 

 

53 

 

The TPC was determined based on the Folin-Ciocalteu colourimetric method as described by Hu and Xu [12]. 

Briefly, an aliquot (0.5 mL) of the suitable diluted extracts, 2.5 mL of deionized water and 0.5 mL of 1.0 M Folin-

Ciocalteu reagent were mixed within 10 mL volumetric flasks and vortexed. After 8 min, 1.5 mL of 7.5% sodium 

carbonate solution was added and mixed thoroughly. The absorbance of the reaction mixtures was measured using a 

spectrophotometer at 765 nm wavelength after incubation for 2 h at room temperature. Extraction solvent was used 

as the blank and gallic acid (GA) was used for calibration of standard curve. Phenolic content was expressed as 

milligrams of gallic acid equivalents (GAE) per 100 g of DM. 

 

2.7.2. Antioxidant Activity by DPPH Radical Scavenging Assay 
DPPH radical scavenging activity was determined according to the method of Hu and Xu [12] with some 

modifications. Briefly, each of sample solutions (1 mg/mL in methanol) was serially diluted to various 

concentrations in methanol respectively, and then a 0.5 mL of samples was mixed with 2.5 mL of 60 μM DPPH 

dissolved in methanol. The mixture was shaken vigorously and left to stand for 30 min in the dark, and the 

absorbance was measured at 517 nm against a solvent blank. The scavenging rate on DPPH radicals was calculated 

according to the formula, scavenging rate (%) = [(Ao-A1)/Ao]×100, where Ao is the absorbance of the control 

solution, A1 is the absorbance in the presence of samples in DPPH solution.  

 

2.8. Statistical Analysis 
All results are expressed as mean ± SD (n=3). In order to evaluate the significant differences between sample 

means, one-way analysis of variance (ANOVA) and Duncan’s test were performed with significant level being 

considered at p < 0.05. 

 

3. Results 
3.1. The Effects of Drying Methods on Rehydration Ratio 

Colour, rehydration and shrinkage ratio are three important factors to evaluate appearance and texture of 

dehydrated products. The rehydration capacities of mushroom samples dried with different drying methods are 

presented in Fig. 1. Among all the treatments, MD got the lowest rehydration radio which reaches at 5.2-fold of dried 

body, whereas FD and ND got the highest rehydration radio which reaches at 8.7 and 8.4-fold of dried body 

respectively. This may be due to the changes in the structure and texture of the samples during different drying 

processing [13, 14]. We postulated that FD and ND provides enough interval time, leading the internal moisture 

diffuse to the surface which avoids the shrinking of surface. For all samples, rehydration radio is fast at the beginning 

of re-watering process and falling to equilibrium state at the end, which was been reported by other authors [15, 16]. 

 

3.2. The Effects of Drying Methods on Shrinkage Ratio 
Fig. 1 showed effects of different drying methods on the shrinkage ratio of mushroom samples, and the influence 

of drying methods on the shrinkage ratio was evident. Contrary to the results of rehydration ratio, shrinkage ratio of 

mushroom dried with FD and ND were the smallest, and were 14.5% and 15.2%, respectively. The shrinkage ratio of 

other samples ranged from 18.5% to 28.6%. This is because much more moisture of samples was removed rapidly at 

higher temperature, which resulted in greater changes of shrinkage ratio under the same drying condition. Therefore, 

temperature of drying may be the main factor affecting the shrinkage ratio of dried mushroom. The changes in 

shrinkage ratio also directly affect rehydration ratio of samples. 

 

3.3. The Effects of Drying Methods on Color 
The effects of drying methods on color of dried mushroom are shown in Table 1. CIE L*, a*, and b* values were 

significantly different among drying methods. As an objective evaluation of dehydrated products, CIE L* values 

appear to be important and sensitive to color evaluation, which can be an indicator of lightness of color. The CIE a* 

value indicates the redness (positive a*) and greenness (negative a*), while the CIE b* value indicates the 

yellowness. The CIE L*, a*, and b* values of fresh mushroom were 26.33, 0.95, 1.13 respectively. However, after 

drying CIE L*, a*, and b* values ranged from 31.56 to 42.34, from 1.08 to 3.86, and from 2.51 to 6.31, respectively. 

These changes in the CIE L*, a*, and b* values implied that drying treatment had obvious effects on the color of 

dried mushroom. Among them, the effect of FD on color was the least, followed by ND, while MD and ID 

influenced significantly the color of dried mushroom. The phenomenon can be attributed to the enzymatic browning 

which may be the main reason for brown stain of the products [17, 18]. 

 

3.4. The Effects of Drying Methods on Proximate Chemical Compositions  
The effects of drying methods on the chemical compositions of dried shiitake mushroom are shown in Table 2. 

Based on dry weight, it can be easily seen that the crude ash ranged from 6.3 to 6.6 g/100 g DW, crude fat ranged 

from 4.2 to 4.8 g/100 g DW, and the carbohydrate ranged from 54.1 to 54.7 g/100 g DW, which indicate that six 

drying methods had no effects on the content of ash, crude fat and carbohydrate of shiitake mushroom. The content 

of crude fiber of fresh mushroom was 11.2 g/100 g DW, and it increased and ranged from 11.5 to 16.1 g/100 g DW 

after drying, especially MD and ID. The protein are found in high levels and varied between 18.5 to 20.6 g/100 g 

DW. ND and FD had no obvious effect on protein content compared with fresh mushroom, while other drying 

methods can result in decrease of protein. Overall, FD is the best drying method which basically retains 

the proximate chemical compositions of fresh mushroom, followed by ND. 

 

3.5. The Effects of Drying Methods on Phenolics 
The effects of drying methods on phenolic content of shiitake mushroom are shown in Fig. 2. The results showed 

that the drying methods had a satisfactory effect on the phenolic content of shiitake mushroom. The total phenolic of 



Agriculture and Food Sciences Research, 2015, 2(2): 51-55 

 

 

 

 

54 

 

fresh shiitake was 35.3 mg/100 g. A reduction in total phenolic contents of dried samples was found. During FD, the 

loss of phenolics was the lowest, followed by VD, ND, MD, HD, and ID. Investigates its reason, the loss may be 

come from enzymatic and non enzymatic reaction of phenolic compounds during the drying process [19]. The 

internal temperature of materials was very high although the heating time was short during microwave drying 

process, while the heating time was longer during hot air drying. Therefore, the higher drying temperature and the 

longer drying time lead to oxidation of phenolic compounds. 

 

3.6. The Effects of Drying Methods on Antioxidant Activities 
The effects of drying methods on the antioxidant activities of shiitake mushroom are shown in Fig. 2. The results 

showed that the drying methods had obvious effects on the antioxidant activities of shiitake mushroom, and the effect 

was similar to TPC. The drying resulted in the decrease of scavenging activity on DPPH radicals. The scavenging 

rate of fresh shiitake on DPPH radicals was 75.4%, while the scavenging activity of FD products on DPPH radicals 

was the near to fresh shiitake with 70.5%, followed by VD, ND, MD, ID and HD. In addition, we found that the 

content of phenolics was highly associated with antioxidant activity, indicating that the phenolic compounds 

contributed significantly to the antioxidant activity of shiitake mushroom, which was in agreement with the previous 

studies [19, 20]. 

 

4. Conclusions 
In conclusion, this work showed that drying methods had obvious effects on the color, proximate chemical 

compositions, total phenolics, antioxidant activity of mushroom. The FD and ND products exhibited the best 

rehydration and shrinkage ratio; the effect of FD on color was the least, followed by ND; six drying methods had no 

effects on the content of ash, crude fat and carbohydrate of shiitake mushroom. Drying resulted in the decrease of 

total phenolics, antioxidant activity of shiitake mushroom. Among them, the mushroom dried with FD had no 

obvious changes compared with fresh mushroom. 

 

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Table-1. The color of fresh and dried shiitake mushroom 

 L* a* b* 

Fresh 26.33 ± 0.55 f 0.95 ± 0.05 d 1.13 ± 0.06 c 

ND 33.32 ± 1.46 de 1.13 ± 0.08 cd 2.56 ± 0.14 b 

HD  35.11 ± 1.65 cd 1.85 ± 0.52 cd 2.64 ± 0.52 b 

VD 37.27 ± 1.25 bc 2.18 ± 0.34 bc 2.93 ± 0.31 b 

ID 40.55 ± 1.54 ab 3.25 ± 0.25 ab 5.84 ± 0.55 a 

MD 42.34 ± 1.13 a 3.86 ± 0.84 a 6.31 ± 0.24 a 

FD 31.56 ± 0.82 e 1.08 ± 0.10 cd 2.15 ± 0.13 b 

 
Numbers represent mean values of three independent replicates ± SD. Different letters indicate statistically 

significant differences between the means (P < 0.05) for each parameter. 

 
Table-2. Proximate compositions (g/100 g DM) of fresh and dried shiitake mushroom  

 Crude Protein Crude Fat Carbohydrate Crude Fiber Crude Ash 

Fresh 20.2 ± 0.4 a 4.5 ± 0.2 ab 57.7 ± 1.8 a 11.2 ± 0.6 de 6.3 ± 0.5 a 

ND 20.4 ± 0.2 a 4.4 ± 0.1 ab 56.2 ± 0.9 a 12.5 ± 0.3 d 6.4 ± 0.8 a 

HD  18.5 ± 0.1 c 4.7 ± 0.2 a 55.8 ± 1.4 a 14.5 ± 0.2 c 6.4 ± 0.6 a 

VD 19.4 ± 0.1 b 4.7 ± 0.1 a 54.7 ± 1.3 a 14.8 ± 0.5 bc 6.3 ± 0.5 a 

ID 18.9 ± 0.2 bc 4.8 ± 0.3 a 54.1 ± 0.8 a 15.6 ± 0.1 ab 6.5 ± 0.4 a 

MD 18.9 ± 0.3 bc 4.2 ± 0.4 ab 54.2 ± 1.4 a 16.1 ± 0.4 a 6.6 ± 0.2 a 

FD 20.6 ± 0.2 a 4.6 ± 0.2 ab 56.9 ± 1.2 a 11.5 ± 0.3 e 6.3 ± 0.5 a 

 

Numbers represent mean values of three independent replicates ± SD. Different letters indicate statistically      

significant differences between the means (P < 0.05) for each parameter. 
 

 
Fig-1. Effect of drying methods on rehydration and shrinkage ratio 

 

 
Fig-2. The effects of drying methods on phenolic content and antioxidant activity of shiitake mushroom 

. 

 

 

 

 
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