Determination of effective moisture diffusivity, energy consumption and active ingredient concentration variation in Inula racemosa rhizomes during drying

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Determination of effective moisture diffusivity, energy consumption and active ingredient concentration variation in Inula racemosa rhizomes during drying Vasudha Agnihotri ∗ , Arvind Jantwal, Rajesh Joshi G.B. Pant National Institute of Himalayan Environment and Sustainable Development, Kosi-Katarmal, Almora, India

a r t i c l e

i n f o

Article history: Received 18 August 2016 Received in revised form 15 September 2016 Accepted 29 September 2016 Available online xxx Keywords: Inula racemosa Himalaya Drying Diffusion Alantolactone Isoalantolactone

a b s t r a c t Influence of drying temperature (30 ◦ C–60 ◦ C) and relative humidity (30%–80%) on moisture diffusivity, energy requirement and quality of Inula racemosa rhizomes, in terms of alantolactone and isoalantolactone, were analyzed. The rhizomes were dried in climate control chamber with constant values of temperature and relative humidity. At low relative humidity condition temperature was found as major controlling factor for drying rate but at high relative humidity conditions, it control drying rates in comparison to temperature. Effective diffusion coefficient (Deff) was found to decrease with increase in relative humidity of drying air. Energy requirement increases with increase in relative humidity and temperature. Concentration of alantolactone and iso-alantolactone was found to increase during drying in comparison to that in fresh I. racemosa rhizomes. © 2016 Published by Elsevier B.V.

1. Introduction Inula racemosa, commonly known as Pushkarmool, belongs to family Asteraceae. It is a traditional herb used as drug in Ayurvedic and Chinese system of medicines. The rhizome has medicinal properties and considered a specific for cough, dyspnea, asthma, pleurisy, tuberculosis and chest pain especially pre cordial pain. The aqueous extract of the fresh or dry roots is given orally in rheumatic pains and liver problems. Externally a paste or liniment is used for relieving pain. The root forms an important ingredient of several polyherbal fomulations for heart diseases and inflammatory conditions of spleen and liver (The Ayurvedic Formulary of India, 1978). Along with Commiphora mukul, the drug combination called ‘pushkar guggulu’ is a popular anti obesity, hypolipidemic indicated in cardiac ailments. Root powder is reportedly hypoglycemic and hypocholesterolemic in human subjects (Tripathy et al., 1979). Use of I. racemosa rhizomes is reported in drug preparation of asthama as part of ayurvedic drug Respiton–850 mg (Vermula et al., 2011). It is also used in the treatment of ailments like skin allergies, cough and cardiac diseases. Along with these properties, plant rhizomes are also having antifungal, anthelmintic, antimicrobial & hypolipi-

∗ Corresponding author. E-mail address: [email protected] (V. Agnihotri).

demic properties. As a traditional Chinese medicine, the rhizomes of I. racemosa usually were used to invigorate the spleen, regulate the function of the stomach, relieve the depression of the liver Qi, alleviate pain especially between the neck and the shoulders and to prevent abortion (Jiangsu College of New Medicine, 1977; Tsarong, 1994). Alantolactone (ALT) and isoalantolactone (IALT) are two important sesquiterpene lactones present in I. racemosa (Arora et al., 1980). These compounds are used as active principle of antiulcer drug Alanton (Milman, 1990). ALT and IALT are reported as antifeedant to granary pests (Streibl et al., 1983). These compound are anti-inflammatory (Dalvi and McGowan, 1982), antimicrobial, anthelmintic (Wordenbag et al., 1986) properties. Being such an important plant, it had been selected for the drying study. After harvesting of medicinal plants, plant material had to gone through various post harvest processing steps such as cleaning, drying for storage, packaging for transportation etc. It is estimated that as high as 30% of the raw material reaching the manufacturers is of low quality and hence is likely to be rejected. Therefore, improving quality, reducing losses and subsequent value addition would increase profitability. Among the various above mentioned steps, drying is the most common and fundamental step required for post harvest preservation of medicinal plants because it allows quick protection of medicinal qualities of the plant material in an uncomplicated manner (Muller and Heidnl, 2006). In order to optimize practices for thermal processing and drying of biological mate-

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Please cite this article in press as: Agnihotri, V., et al., Determination of effective moisture diffusivity, energy consumption and active ingredient concentration variation in Inula racemosa rhizomes during drying. Ind. Crops Prod. (2016), http://dx.doi.org/10.1016/j.indcrop.2016.09.068

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rials, extensive research has been carried out around the world on various drying methods. There are three major types of drying procedures; (i) shade drying (Khorshidi et al., 2009; Verma and Chauhan, 2011; Annamalai et al., 2011) (ii) sun drying (Asekun et al., 2006) and (iii) drying using artificial methods such as freeze drying (Koller, 1995), heating (Radunz et al., 2001; Braga et al., 2005; Venskutonis, 1997; Buggle et al., 1999; Omidbaigi et al., 2004), microwave drying (Soysal et al., 2009), drying using climate chamber (Reynolds, 1998) etc. Different types of drying methods have been used to optimize the drying of target materials where not all types of drying processes are suitable for all the biological materials (Sadykov et al., 1997). The quality of medicinally important biological materials is so specific that drying of each product should be studied on an individual basis (Dillard and German, 2000). The method of drying must be experimentally determined for each plant/plant part used as drug. The slow drying may cause harmful changes, by the action of enzymes, fungi and bacteria, before the process is completed. A very quick drying hardens the superficial layer of the cells and prevents the evaporation of water inside the organ, which also results in the action of enzymes (Bonazzi and Dumoulin, 2011). So drying process needs to be standardize which can reduce the loss of medicinally important compounds present in medicinal plants. This investigation aims to determine effective moisture diffusivity and energy required during drying of rhizomes, and to analyze the variation in alantolactone and iso-alantolactone content in Inula racemosa rhizomes dried at different drying conditions.

2. Material and methods 2.1. Drying equipment Drying was performed in Climate chamber (Jeio Tech, Korea; model: TH-PE-100) equipped with controllers for temperature and relative humidity (Fig. 1). A balance (make: Citizen) was placed outside the dryer and used for measurement of weight variations of sample during definite time intervals. 30°C-30% 30°C-50% 30°C-70%

Two-year-old freshly harvested Inula racemosa rhizomes were purchased from Shansha villege, Lahul, Himachal Pradesh (2868.2 amsl; 32◦ 36 52.64”N, 76◦ 54 05.31”E). After harvest, the material was immediately transported to laboratory, washed with water to remove soil particles and surface dried. Subsequently moisture content was determined and then kept in a refrigerator (4 ◦ C) until used. HPLC grade and analytical grade solvents were purchased from Rankem, India. Alantolactone (lot number: 00001511-305) and isoalantolactone (lot number: 00009175-203) standards were purchased from Chromadex, CA, USA.

30°C-40% 30°C-60% 30°C-80%

70 60 50 40 30 20

2.2. Plant material and chemicals

0

100000

200000

40°C-30% 40°C-50% 40°C-70%

80 Moisture content (% wb)

Moisture content (% wb)

80

Fig. 1. Climate chamber set up used for drying experiments.

70 60 50 40 30 20

300000

50000 100000 150000 200000 250000

0

Drying time (s)

Drying time (s) 50°C-30% 50°C-50% 50°C-70%

75

50°C-40% 50°C-60% 50°C-80%

65 55 45 35 25 15

0

50000

100000 150000 200000 250000 Drying time (s)

60°C-30% 60°C-50% 60°C-70%

85 Moisture content (%wb)

Moisture content (% wb)

85

40°C-40% 40°C-60% 40°C-80%

75

60°C-40% 60°C-60% 60°C-80%

65 55 45 35 25 15

0

100000

200000

3000

Drying time (s)

Fig. 2. Drying curves of I. racemosa rhizomes at different temperature (◦ C) and relative humidity (%) conditions.

Please cite this article in press as: Agnihotri, V., et al., Determination of effective moisture diffusivity, energy consumption and active ingredient concentration variation in Inula racemosa rhizomes during drying. Ind. Crops Prod. (2016), http://dx.doi.org/10.1016/j.indcrop.2016.09.068

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Drying rate (g/100g)wb.s)

0.05

Drying rate (g/100g wb.s)

30°C-30% 30°C-40% 30°C-50% 30°C-60% 30°C-70% 30°C-80%

0.06

0.04 0.03 0.02 0.01 0.00

20

40

60

80

0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00

40°C-30% 40°C-40% 40°C-50% 40°C-60% 40°C-70% 40°C-80%

20

40

Moisture content (% wb)

0.06 0.05

60°C-40% 60°C-50%

0.09

0.04 0.03 0.02 0.01 0.00

80

60°C-30%

0.10

50°C-30% 50°C-40% 50°C-50% 50°C-60% 50°C-70% 50°C-80%

0.07

60

Moisture content (% wb)

Drying rate (g/100g.s)

Drying rate (g/100g.s)

0.08

3

60°C-60%

0.08

60°C-70%

0.07

60°C-80%

0.06 0.05 0.04 0.03 0.02 0.01

20

30

40

50

60

70

80

0.00

35

15

55

75

Moisture content (%wb)

Moisture content (% wb)

Fig. 3. Changes in drying rate of I. racemosa rhizomes at different drying air relative humidity (%) and constant temperature (◦ C).

2.3. Controlled drying of raw materials The temperature of refrigerated plant material was normalized, then chopped into small pieces (appx 0.75 cm thick) and 30 g material (in triplicate) was dried under controlled conditions. During drying, temperature and relative humidity condition were varied from 30 ◦ C to 60 ◦ C and 30% to 80% respectively. The materials were dried until constant weight. 2.4. Determination of drying rate, effective moisture coefficient and specific energy requirement

MR =

The moisture ratio and drying rate of I. racemosa rhizomes during drying experiments were calculated using the following equations: MR = DR =

(M − Me ) (M0 − Me ) (Mt+dt − Mt ) dt

(1) (2)

where MR, DR, M, M0 , Me , Mt and Mt+dt are the moisture ratio, drying rate, moisture content at any time, initial moisture content, equilibrium moisture content, moisture content at t and moisture content at t + dt (kg water/kg dry matter), respectively, t is drying time (s). The effective diffusion coefficient is a function of temperature and moisture content of material, which is an important transport property used in modeling of drying process of medicinal plants. Fick’s second law of diffusion represents a mass and heat transfer equation for drying of plant materials as shown below: ıM = Deff ∇ 2 M ıt

Eq. (2) was solved by Crank, 1979 to understand diffusion process for various geometries of plant materials during the falling rate period with the application of several boundary conditions (Ozdemir and Devres, 2000). For the current study Fick’s second law of diffusion was used for infinite slab assuming unidimensional moisture movement volume change, constant temperature and diffusivity coefficients, and negligible external resistance (Zogzas et al., 1994):

(3)

1 8 n=∞ exp 2 n=0 (2n + 1)2



−Deff (2n + 1)2 2 t 4l2



(4)

where l is half thickness of the slab, n is the positive integer, and Deff is effective diffusivity coefficient. For long drying periods, only the first term of the equation is often applied as used by various researches (Velic et al., 2004; Aghbashlo et al., 2008). Thus the Eq. (4) becomes: MR =

8 exp 2



−

2 Deff 4l2



t

(5)

The above equation has been used in order to describe the diffusion. Eq. (5) can be further simplified and expressed as log-linear form (Doymoaz, 2012; Hii and Ogugo, 2014; Onwude et al., 2016) ln MR = ln

8  2

−

2

Deff 4l2



t

(6)

The diffusion coefficient is obtained by plotting experimental drying data in terms of ln (MR) versus time. The slope of Eq. (6) was calculated using following equation (Doymoaz, 2006): K1 =

2 Deff 4l2

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30°C-30% 50°C-30%

0.12

40°C-30% 60°C-30%

0.08 Drying rate (g/100g.s)

Drying rate (g/100g.s)

0.10 0.08 0.06 0.04 0.02 0.00

30°C-40% 50°C-40%

0.09

40°C-40% 60°C-40%

0.07 0.06 0.05 0.04 0.03 0.02 0.01

15

35

55

0.00

75

15

35

30°C-50% 50°C-50%

0.08

55

75

Moisture content (%w.b.)

Moisture content (% wb)

40°C-50% 60°C-50%

Dryin rate (g/100g.s)

0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00

15

35 55 Moisture content (%w.b.)

75

Fig. 4. Changes in drying rate of I. racemosa rhizomes at different drying air temperature (◦ C) and constant relative humidity (%).

During the test, total dryer energy consumption and the energy required for drying one kilogram of rhizome were calculated using Eqs. (8) and (10) (Koyuncu et al., 2007; Motevali et al., 2011). Et = Ava Ca TDt

(8)

where, Et is the total energy in each drying phase (kWh), A is the cross sectional area of the holder (m2 ), v is the air velocity (m s−1 ), a is the air density (kg m−3 ), T is the temperature differences (◦ C), Dt total time for drying each sample (h) and Ca is the specific heat of air (kJ kg−1 ◦ C−1 ). Specific heat of air (Ca ) was calculated using Eq. (9) Ca = 1.004 + 1.88ω

(9)

where ω is humidity ratio Energy consumption for drying 1 kg of fresh I. racemosa rhizomes was obtained using Eq. (10): Ekg = Et /W0 is the required specific energy in kWh kg−1

where Ekg weight of water removed in kilogram.

(10) and W0 is the

2.5. Sample preparation for quantitative analysis using gas chromatography The rhizomes of I. racemosa were dried under different combinations of temperature ranging from 30 ◦ C to 60 ◦ C and relative humidity 30% to 80% using TH + PE −100(1 ph) Jeio Tech climate chamber. The dried plant material was powdered and 2 g powdered rhizome was macerated using ethanol (1:5 ratio) for 24 h on a rotary shaker. In case of fresh stage, 30 g crushed I. racemosa rhizomes were macerated for similar duration and similar solvent. The extract obtained was filtered and dried at room temperature. Dried extracts were dissolved in equal volume of ethanol. Quantitative estimation of alantolactone & isoalantolactone compounds present in dried sample was carried out using gas chromatograph with flame ionization detector (GC-FID). (Chemito Ceres 800 plus) using BP1 column (30 m in length x 0.25 mm i.d. x 0.25 ␮m). Column

temperature was increased up to 80 ◦ C and ramped at 15 ◦ C/min up to 210 ◦ C, temperature was increased 250 ◦ C at a rate of 5 ◦ C/min and then to 280 ◦ C at the rate of 20 ◦ C/min. Nitrogen was used as carrier gas, with the flow rate of 1.5 ml/min. The inlet temperature was maintained as 250 ◦ C. The data obtained was interpreted using Iris 32 software. Standard solution of 1000 ␮g/ml containing equal amount of alantolactone and isoalantolactone was prepared. Dilution of the mixed standards were prepared in the range of 10–100 ␮g/ml using ethanol. 0.5 ␮l aliquot was injected through injector for calibration curve preparation. The calibration curves were constructed by plotting the mean peak areas versus concentration. Limits of detection (LODs) were the lowest analyte concentration at which the signal-to-noise ratio (S/N) is equal to 3:1. Concentration of alantolactone and isoalantolactone obtained for 2 g dried material, were converted to 30 g fresh weight equivalent by using final dry weight obtained after drying 30 g material under different temperature and relative humdity conditions. 2.6. Statistical analysis The analysis of variance (ANOVA) was used to perform the effect of drying temperature and relative humidity on energy requirement during drying and on concentration of alantolactone and isoalantolactone during drying process. Mean values were considered at 95% significance level (p < 0.05). 3. Results 3.1. Drying characteristics of I. racemosa rhizomes Fig. 2 shows drying rate curves of I. racemosa rhizomes at different drying air relative humidity (%) and temperatures (◦ C). Drying period was found varying at different drying conditions, which indicates that drying process is determined mainly through diffusion process. Rate of removal of moisture from the material during the drying process varies with variation in air relative humidity at constant temperature, which depict that moisture removal, is

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0 -1

0

50000

100000

150000

200000

(a) 0

slope II at 30% RH slope II at 40% RH slope II at 50% RH slope I at 60% RH slope II at 60% RH

-4

slope II at 60% RH

slope II at 70% RH slope II at 70% RH slope I at 80% RH

-7

slope II at 80% RH

Drying time (s)

50000

100000

150000

slope III at 80% RH

200000

slope I at 40% RH slope II at 40% RH slope I at 50% RH slope II at 50% RH slope III at 50% RH

-4

slope I at 60% RH

-5

slope I at 70% RH

-6

slope III at 70% RH

-1

slope I at 30% RH slope II at 30% RH

slope I at 60% RH slope II at 60% RH

-5

slope I at 70% RH

-6

slope II at 79% RH

-7

slope I at 80% RH

slope III at 70% RH slope II at 80% RH

ln MR

-4

slope I at 80% RH slope II at 80% RH

Drying time (s)

0

50000

100000

150000

slope II at 80% RH

200000

slope I at 30% RH slope II at 30% RH slope I at 40% RH slope II at 40% RH slope I at 50% RH

-3

slope I at 50% RH slope II at 50% RH

slope II at 70% RH

-2

slope I at 40% RH

-3

slope I at 30% RH slope II at 30% RH

-7

slope II at 40% RH

ln (MR)

200000

-3

(b) 0 0

-2

-8

150000

slope II at 60% RH

slope I at 70% RH

-6

-1

100000

slope III at 40% RH

-5

(b) 0

50000

-2

slope I at 50% RH

-3

0

-1

slope I at 40% RH

-2

ln (MR)

slope I at 30% RH

ln MR

(a)

5

slope II at 50% RH slope I at 60% RH

-4

slope II at 60% RH

-5

slope I at 70% RH

-6

slope I at 80% RH

slope II at 70% RH slope III at 80% RH

-7 -8

slope III at 80% RH slope II at 80% RH

Drying time (s)

slope III at 50% RH

Drying time (s) Fig. 6. ln MR versus time (s) when temperature is (a) 50 ◦ C; (b) 60 ◦ C.

Fig. 5. ln MR versus time (s) when temperature is (a) 30 ◦ C; (b) 40 ◦ C.

proportional to concentration of product water. So it might be dependent on effective diffusion and can be modeled using Fick’s second law. Relative humidity of drying air at constant temperature has significant affect (p < 0.05) on final moisture content of the material as it controls the rate of water vapour transport from its surface to the air and influences the value of equilibrium moisture content. Kaya and Aydinv, 2008 and Hosseini, 2005 had also found influence of drying air conditions on behaviour of plant material during drying. At low relative humidity condition i.e. at 30%, temperature is major controlling factor for drying rate but as relative humidity increases, it become major controlling factor in drying process (Figs. 3 and 4). Time taken to achieve constant weight con-

dition is highest at 30 ◦ C drying air temperature and 80% relative humidity i.e. 277,200 s (77 h) while lesser in case of 60 ◦ C drying air temperature and 40% relative humidity i.e. 46,800 s (13 h), that corresponds to reduction in time of approximately 44% between these two conditions (Fig. 5). These results are attributed to the fact that with an increase in relative humidity of drying air decreases its saturation deficit and so diminish the capacity of absorbing humidity from surroundings and as a result drying time increases. 3.2. Effective moisture diffusivity and energy requirement Process of drying was continued until the constant weight of I. racemosa rhizomes. Effective diffusion coefficient was calculated

Fig. 7. GC chromatogram of I. racemosa rhizomes dried under drying air temperature 40 ◦ C and relative humidity 70%.

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Table 1 Effective diffusion coefficients during two falling rate periods at different temperature and relative humidity conditions. Effective Diffusion coefficients

Temperature (◦ C)

Deff-I

30 40 50 60 30 40 50 60

Deff-II

Relative humidity 30%

40%

50%

60%

70%

80%

6.83E-10 6.83E-10 6.83E-10 9.11E-10 1.14E-09 1.37E-09 9.11E-10 1.59E-09

4.56E-10 4.56E-10 4.56E-10 6.83E-10 1.37E-09 1.14E-09 1.82E-09 1.82E-09

4.56E-10 4.56E-10 2.28E-10 4.56E-10 9.11E-10 1.59E-09 6.83E-10 1.59E-09

2.28E-10 4.56E-10 2.28E-10 4.56E-10 6.83E-10 6.83E-10 1.14E-09 1.82E-09

2.05E-10 2.28E-10 2.28E-10 2.28E-10 4.56E-10 6.83E-10 6.83E-10 6.83E-10

2.28E-10 2.28E-10 2.05E-10 2.28E-10 2.28E-10 4.56E-10 6.83E-10 4.56E-10

Table 2 Energy consumption at different drying conditions studied for I. racemosa rhizome. Drying conditions ◦

30 C-30% 30 ◦ C-40% 30 ◦ C-50% 30 ◦ C-60% 30 ◦ C-70% 30 ◦ C-80% 40 ◦ C-30% 40 ◦ C-40% 40 ◦ C-50% 40 ◦ C-60% 40 ◦ C-70% 40 ◦ C-80% 50 ◦ C-30% 50 ◦ C-40% 50 ◦ C-50% 50 ◦ C-60% 50 ◦ C-70% 50 ◦ C-80% 60 ◦ C-30% 60 ◦ C-40% 60 ◦ C-50% 60 ◦ C-60% 60 ◦ C-70% 60 ◦ C-80%

Et

Ekg

16.45 ± 0.15 15.26 ± 0.00 16.75 ± 2.46 24.24 ± 0.45 28.58 ± 1.20 40.55 ± 3.00 15.44 ± 1.02 18.73 ± 1.55 21.82 ± 2.79 25.49 ± 2.03 28.01 ± 3.30 34.00 ± 0.39 25.97 ± 0.00 24.57 ± 0.41 25.97 ± 0.00 25.98 ± 0.00 33.23 ± 3.63 42.13 ± 0.00 19.34 ± 0.72 13.08 ± 2.45 20.16 ± 1.44 31.06 ± 4.03 40.88 ± 1.70 55.88 ± 3.82

548.54 ± 4.99 508.66 ± 0.00 558.55 ± 82.10 807.93 ± 14.96 952.59 ± 39.90 1351.62 ± 100.12 514.97 ± 34.06 624.43 ± 51.50 727.48 ± 92.85 849.84 ± 67.83 933.6 ± 110.02 1133.26 ± 12.88 865.61 ± 0.00 818.9 ± 13.51 865.78 ± 0.00 865.87 ± 0.00 1107.79 ± 121.11 1404.38 ± 0.00 644.5924.02 435.85 ± 81.72 672.04 ± 48.06 1035.47 ± 134.42 1362.68 ± 56.73 1862.63 ± 127.2

Et : total energy requirement during drying (kW h). Ekg : Specific energy requirement during drying (kW h/kg).

using Eq. (3). Figs. 5–6 show the ln MR versus time (s) at constant temperature and different levels of relative humidity (%). Drying process of agricultural produce takes place at two different rates i.e. fixed and falling rate, which may be due to the capillary and cellular structure of plant material under study affecting evaporation rate during drying process (Adabi et al., 2013). Increase in relative humidity decreases slope of straight line, i.e. value of effective diffusion coefficient (Deff ) decreases with increase in relative humidity value (Table 1). The effective moisture diffusivity for I. racemosa rhizomes varied from 2.05 × 10−10 to 9.11 × 10−10 m2 /s for slope I and 2.28 × 10−10 to 9.11 × 10−9 m2 /s for slope II which in the ranges of Deff values reported for food materials (Babalis et al., 2006; Aghbashlo et al., 2008; Zogzas et al., 1994). Similar results have been reported for drying studies on other plant materials eg. thyme leaves (Adabi et al., 2013), celery leaves (Alibas and Köksal, 2014), black grapes (Doymoaz, 2006). Increase of Deff value with time has also observed by Simal et al., 1994 and Velic et al., 2004 who have studied drying behaviour of potato and apple respectively. Total energy required for drying one charge of heater and specific energy requirement for drying one kg of I. racemosa rhizomes were calculated for each drying condition as shown in Table 2. Maximum value of total energy and specific energy needed which is 55.87 kWh and 1862.62 kWh/kg respectively was obtained at 60 ◦ C drying temperature and 80% relative humidity. Minimum value of total energy and specific energy needed was 13.07kWh

and 435.85 kWh/kg respectively at 60 ◦ C drying temperature and 40% relative humidity. Energy requirement increases with increase in relative humidity and temperature except at 40 ◦ C drying temperature. Variation of drying air temperature and relative humidity is significantly affecting the energy requirement during complete drying (p < 0.05) as shown in Table S1. Water absorption capacity decreases as the relative humidity increases, thereby needing a major quantity of air mass flow for evaporation rate in drying. Therefore energy consumption to heat the air increases as relative humidity increases, leading to an increase of water absorption capacity due to absorption of more moisture (Kajiyama and Jin Park, 2010). Similar type of results were also found by Adabi et al., 2013.

3.3. Effect on Alantolactone and iso-alantolactone concentration Fig. 7 shows typical chromatogram of extract of dried I. racemosa rhizome. Two representative chemical markers namely Alantolactone and iso-alantolactone were determined quantitatively in the final dried material for knowing affect of drying on their concentration, which is shown in the chromatogram at the retention time of 10.74 and 11.29 min when rhizomes were dried at 40 ◦ C and 70% relative humidity of drying air in the climate chamber. LOD for alantolactone and isoalantolactone for the method used was 1.17 and 5.25 ␮g/ml respectively. Table 3 presents the concentration of alantolactone and iso-alantolactone concentration in I. racemosa rhizomes after drying along with their concentration in fresh material. Concentration of Alantolactone ranges from 1.82 to 15.71% and iso-alantolactone from 0.89 to 11.40% in samples dried under different conditions. The concentration of Alantolactone and iso-alantolactone was highest at 40 ◦ C temperature and 70% relative humidity of drying air inside climate chamber. Variation of drying air temperature and relative humidity is significantly affecting the alantolacotne and iso-alanto lactone% content in dried material (p < 0.05) as shown in Table S2. Such an increase in Alantolactone and iso-alantolactone content in this study might be attributed to the increase in rate of bioconversion of precursor of alantolactones, which needs to be further examined. Similar type of observation was found in the case of Artemisia annua (Ferreira and Luthria, 2010), where increase in artemisinin content in leaves was 43% in plants dried in oven and shade, and 94% in sun-dried plants. This increase was observed due to rapid bioconversion of dihydroartemisinic acid (DHAA) to artemisinin (ART) during drying conditions. In a separate study by Hansen et al., 2011 with Taxus baccata plant parts, concentration of taxol lower at 30 ◦ C (0.008% of oil related to the mass of plant) while higher at high temperature eg 40 ◦ C, 50 ◦ C or 60 ◦ C (0.014%). So far no study has been reported to examine the effect of drying conditions on Alantolactone and iso-alantolactone content of I. racemosa rhizomes and hence these findings are valuable not only for commercial production of Alantolactone and iso-alantolactone but also useful for disinfections, and long term preservation of the plant material (Schweiggert et al., 2007).

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Table 3 Variation of alantolactone and iso-alantolactone concentration in I. racemosa rhizomes at different drying conditions. Sample status

Alnatolactone conc. (%) ± SE

Iso-alnatolactone conc. (%) ± SE

Fresh Dried at 30 ◦ C-30% Dried at 30 ◦ C-40% Dried at 30 ◦ C-50% Dried at 30 ◦ C-60% Dried at 30 ◦ C-70% Dried at 30 ◦ C-80% Dried at 40 ◦ C-30% Dried at 40 ◦ C-40% Dried at 40 ◦ C-50% Dried at 40 ◦ C-60% Dried at 40 ◦ C-70% Dried at 40 ◦ C-80% Dried at 50 ◦ C-30% Dried at 50 ◦ C-40% Dried at 50 ◦ C-50% Dried at 50 ◦ C-60% Dried at 50 ◦ C-70% Dried at 50 ◦ C-80% Dried at 60 ◦ C-30% Dried at 60 ◦ C-40% Dried at 60 ◦ C-50% Dried at 60 ◦ C-60% Dried at 60 ◦ C-70% Dried at 60 ◦ C-80%

0.78 ± 0.04 4.01 ± 0.03 2.84 ± 0.19 5.67 ± 0.45 1.83 ± 0.11 5.40 ± 0.12 7.75 ± 0.35 6.97 ± 0.04 3.94 ± 0.01 6.98 ± 0.91 8.60 ± 0.04 15.72 ± 0.23 5.51 ± 0.14 2.11 ± 0.09 2.27 ± 0.14 1.90 ± 0.09 4.11 ± 0.13 10.06 ± 0.28 2.61 ± 0.12 2.54 ± 0.04 6.31 ± 0.15 8.62 ± 0.26 6.68 ± 0.22 5.69 ± 0.15 3.51 ± 0.17

0.47 ± 0.02 2.06 ± 0.01 1.47 ± 0.08 3.46 ± 0.34 1.05 ± 0.06 2.95 ± 0.04 4.70 ± 0.19 3.79 ± 0.03 1.84 ± 0.02 3.72 ± 0.50 5.17 ± 0.10 11.41 ± 0.01 3.49 ± 0.08 1.26 ± 0.06 0.97 ± 0.06 0.90 ± 0.05 2.00 ± 0.08 5.87 ± 0.18 1.38 ± 0.07 1.13 ± 0.03 2.94 ± 0.09 4.85 ± 0.21 4.46 ± 0.11 2.89 ± 0.08 1.96 ± 0.08

Temperature (◦ C) and relative humidity (%).

4. Conclusion This study has shown the effect of drying temperature and relative humidity on moisture diffusion from the I. racemosa rhizomes under drying, energy requirement at each drying condition and quality in terms of alantolactone and iso-alantolactone concentration in I. racemosa rhizomes dried under different conditions in climate chamber. Drying conditions mainly the temperature and relative humidity significantly affecting the moisture removal rate from I. racemosa rhizomes, effective diffusion coefficient (Deff ) decreases with increase in relative humidity value, while energy requirement increases with increase in relative humidity and temperature at constant temperature and relative humidity. Alantolactone and iso-alantolactone concentration increases during drying in comparison to that in fresh material. Funding This work was supported by the National Medicinal Plant Board, Ministry of AYUSH, Government of India, New Delhi (Project No. R&D/UA-01/2012). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.indcrop.2016.09. 068. References Adabi, M.E., Minaei, S., Motavalli, A., Taghizadeh, A., Azadbakht, M., 2013. Energy consumption, effective moisture diffusion and activation energy in drying of thyme leaves. Int. J. Agron. Plant Prod. 4 (9), 2404–2412. Aghbashlo, M., Kianmehr, M., SamimiAkhijahani, H., 2008. Influence of drying conditions on the effective moisture diffusivity, energy of activation and energy consumption during the thin-layer drying of berberis fruit (Berberidaceae). Energy Convers. Manag. 49, 2865–2871. Alibas, I., Köksal, N., 2014. Mathematical modeling of microwave dried celery leaves and determination of the effective moisture diffusivities and activation energy. Food Sci. Technol. Campinas 34 (2), 394–401.

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Please cite this article in press as: Agnihotri, V., et al., Determination of effective moisture diffusivity, energy consumption and active ingredient concentration variation in Inula racemosa rhizomes during drying. Ind. Crops Prod. (2016), http://dx.doi.org/10.1016/j.indcrop.2016.09.068