Kinetic of Drying of Sliced Turmeric with Modified Direct Sun Drying by Employing Greenhouse Effect

  

Kinetic of Drying of Sliced Turmeric with Modified Direct Sun Drying by

Employing Greenhouse Effect

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  1 Hanim Z. Amanah Silvia Insan Muliawati and Sri Rahayoe

  

Abstract

  Drying of sliced turmeric generally carried out by direct sun drying. This Research was conducted to evaluate the effectiveness of modified direct sun drying by employing greenhouse effect on the drying of sliced turmeric. The research also aimed to determine characteristics drying of sliced turmeric by finding the drying rate constant (k). In this research, turmeric was sliced with the thickness of 2 mm and then dried using direct sun drying and modified sun drying with employing greenhouse effect. The change of temperature and moisture content were observed every 30 minutes. Determining the drying rate constant (k) was done by using zero and first order kinetic equation.

  Result showed that ambient temperature inside dryer was always higher than temperature outside the dryer. The drying rate constant (k) with modified sun drying using greenhouse effect was higher than direct sun drying, respectively and this parameter could be used to predict water content of sliced turmeric during drying process accurately.

  Keywords: Kinetic, sun drying, greenhouse effect, turmeric

Introduction

  Turmeric may have originated from South or South-East Asia, its center of domestication is certainly the Indian subcontinent. Currently, India is the major producer of turmeric, and it is also the major user of its own production. Other producers in Asia include Bangladesh, Pakistan, Sri Lanka, Taiwan, China, Burma (Myanmar), and Indonesia. Turmeric is also produced in the Caribbean and Latin America: Jamaica, Haiti, Costa Rica, Peru, and Brazil

  Turmeric ready for harvest approximately 7 to 10 months after planting. However its depend on the cultivar, soil and the growing condition. The bunches of the rhizome are dug out manually with a spade, or the soil is first loosen with a small digger, and clumps manually lifted. It is better to cut the leaves before lifting the rhizomes. Rhizomes are cleaned from soil by soaking in water, and long roots are removed as well as leaf scales.

  Most agricultural commodities including turmeric require drying process in an effort to preserve the quality of the final product. The quality of the products depends on many factors including the drying temperature and duration of drying time (Fudholi et al, 2010). Recently, there have been many reports on drying kinetics of agricultural fruits and vegetables. Thin-layer drying models also have been widely used for analysis of drying of medical herbs.

  Direct sun drying has been used by farmer to dry many commodities. Solar energy as the source of energy on the drying process has some advantages such as renewable, non polluting nature and inexhaustible. Employing solar energy for drying activities especially for agricultural commodities will be a cheap method for farmer. In Indonesia, direct sun drying was conducted by direct exposure of the product spread on the ground or by use an improvised material to the sun ray. The effectiveness of this method are still unclear and at the same time it may expose commodities to the dust and pest infection (Alonge, 1997). Direct sun drying also has other disadvantages such us high labor cost, large area requirement, losses due to animals, low dying rate and possibility of microbial cross- contamination. Applying direct sun drying also difficult to obtain a uniform product. Therefore, to eliminate the losses and to increase the drying rate associate with direct sun drying, simple and low technology by employing greenhouse effect is preferable.

  Greenhouse dryer operates on the principle of heat gathered in a room that will lead to increase air temperature and then decrease humidity of air . Temperatures in the greenhouse

  o

  can reach 50

  C. The objective of this research is to evaluate the efectiveness of the greenhouse effect in increasing drying rate of sliced turmeric by determine the value of drying rate constant (k) using zero and firs order kinetic equation. This k parameter could be used to predict a decreasing moisture content of sliced turmeric during the drying process with the same method.

Materials and methods Equipments and material

  The dryer with employing greenhouse effect was manufactured in Yogyakarta. The experiment was conducted in the Laboratory of Postharvest and Food Engineering Faculty of Agricultural Technology, Universitas Gadjah Mada.

  The design of dryer is shown in Figure 1. The dryer is a cabinet dryer that constructed by an iron and glass of thickness of 5 mm and consist of two tray. The cross sectional area of the dryer is 1000 mm x 2000 mm. The vertical distance beetween the second tray from the top of the roof is 1000 mm. The bottom of the dryer covered by aluminium sheet and the vertical distance from the groud is 40 cm. This dryer is completed by an air ventilator to allow proper air circulation.The distance between ventilator and ground is 2100 mm. There is hole beetween the roof and the wall for air circulation. The total dimention of dryer is 1000 mm x 2000 mm x 2100 mm. The inside of dryer was painted black to serve an absorber of dryer. This has capacity of 5 - 10 kg of raw material. During experiment, the digital thermocouple with four-channel was used to measure the product and ambient temperature, while thermo hygrometer was used to measure ambient relative humidity (RH).

  The materials used are fresh turmeric with 80% - 90% (wb) moisture content and then dried to 12% moisture content. About 5 kg of turmeric was used in one running for each method of drying.

  Experimental design

  The experiments were conducted by two drying method, direct sun drying and modified sun drying by employing greenhouse effect. The two method was done at the same time to obtain a similar weather condition.

  The turmeric were sliced of 2 mm thickness and spread into the tray of the dryer and then dried from 80% - 90% water content to about 12% water content. At the same time, sliced turmeric also dried by direct sun drying. Ambient temperature inside and outside dryer was measured by digital thermocouple. The data of temperature and water content was collected every 30 minutes during the drying process. Notes:

  1. Ventilator

  Figure 2 shows the typical of ambient and inside dryer temperature during drying process. It was quite clear that dryer temperature was higher than ambient temperature. The result shows that greenhouse effect (GE) can raise ambient to higher value for efective drying. The highest temperature inside dryer is about 44

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  Figure 2. Temperature and relative humidity history inside and outside dryer during drying

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  C higher than the highest ambient temperature. Figure 2 also shows that humidity in the dryer was lower than outside and became an important factor to increase drying rate.

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  C or almost 10

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  5. Covered chamber Figure 1. The design of dryer by employing green house effect for sliced turmeric

  6. Aluminium sheet painted black

  sampling point

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  4. Second tray 9. 3

  sampling point

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  3. First tray 8. 2

  sampling point

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  2. Glasses wall 7. 1

Results and discussion

  Temperature and humidity are important factor on drying. High temperature and low humidity will increase dryng rate. Figure 3a shows decreasing water content of sliced turmeric during drying with employing greenhouse effect with 3 replication. It shows that reduction of water content is different for each replication due to different weather. Direct sun drying show the same data (Figure 3b). From the reduction in moisture content it can be observed that there are two drying rate periods, i.e. periods of constant rate and the rate of falling period. The calculation of constant drying rate (k) shows that in every replication, drying with employing greenhouse effect is higher than those with direct sun drying (Table

  rd 1). In this research, the highest value of drying rate is obtained at the 3 replication , i.e.

  0.15%/min for constant periods and 0.038%/min for falling rate periods. All of them are for drying by employing greenhouse effect. It is clear that greenhouse effect increase ambient temperature and decrease humidity for effective drying. a.Drying by employing greenhouse effect

  b. Direct Sun Drying Figure 3. The moisture change of sliced turmeric during drying Table 1. The drying rate of constant periods and falling periods

  Number Drying with GE Direct Sun Drying of Constant rate Falling rate Constant rate Falling rate (%/min) replication (%/min) (%/min) (%/min) 1 0.14 0.019 0.09 0.011

  2 0.07 0.016 0.09 0.012

  3 0.15 0.038 0.14 0.017

  Figure 4 shows the plotting observation and prediction of moisture content of turmeric by applying both the drying rate value of constant periods and falling rate periods. The figure reveals that the prediction has high correlation with observation data. Figure 4. The prediction and observation of moisture content (MC) on sliced turmeric by employing greenhouse effect

Conclusion

  It can be concluded that, the design of dryer with employing greenhouse effect can dry sliced turmeric into desired moisture content and more effective than direct sun drying. In particular, it also can be concluded that: 1) Modified sun dryer with employing greenhouse

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  effect could increase ambient temperature inside dryer to 44 C or 10 C higher than the temperature outside of the dryer. 2)Drying rate at constant periods for dryer with employing greenhouse effect are ranged from 0.07%/min to 0.15%/min, while direct sun drying are ranged 0.09%/min to 0.14%/min. 3)Drying rate at falling rate periods for dryer with employing greenhouse effect are ranged from 0.019%/min to 0.38%/min, while direct sun drying are ranged 0.11%/min to 0.17%/min

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