Topics: Essential oil, Heat, Thermal conductivity Pages: 4 (1108 words) Published: September 14, 2011
Ohmic Heated Hydrodistillation of ‘Serai Wangi’.

1.1 General Overview
Hydrodistillation is a method to extract essential oil from various plant materials and was used to separate essential oil from Cymbopogon flexuosus (lemongrass). Mostly used by small scale producers of essential oils. In hydrodistillation the plant material is almost entirely covered with water as suspension in the still which is placed on a furnace. Water is made to boil and essential oil is carried over to the condenser along with the steam. The yield is dependent on various parameters like weight of raw material, volume of water, size of raw material and nature of raw material. (Parikh J. K., 2011)

Lemongrass commonly known as “East Indian Lemongrass” is a perennial and multicut aromatic grass. The prefix ‘lemon’ owes to its typical lemon like odour, which is mainly due to the presence of citral, a cyclic monoterpene. Lemongrass is the source of Lemongrass oil, a good source of natural citral, which is used as a basic raw material for synthesis of β-ionone used for synthesis of a number of useful aromatic compounds and Vitamin-A. Citral itself is used in perfumery for various grades of soaps detergents, cosmetics and flavour agent for soft drinks. Consumption of Lemongrass in Ayurvedic preparation like Balm is also increasing.

In ohmic heating processes, foods are made part of an electrical circuit through which alternating current (AC) flow causing heat to be generated within the food due to the electrical resistance of the foods. AC voltage is applied to the electrodes at both ends of the product such as both ends of vessel. The rate of heating is directly proportional to the square of the electric field strength and electrical conductivity. The most important factor that effectuates the rate of heating is electrical conductivity and its temperature dependence. (Ruan et. al, 2001)

The advantages of ohmic heating technology have been claimed in...

References: Arnoldi A., Richardson P. (ed.) (2001) Thermal Processing and Food Quality, Thermal Technologies in Food Processing, England: Woodhead Publishing Limited.
Hishamuddin J. (2011) Ohmic Heated Hydrodistillation, Universiti Kuala Lumpur Malaysia Institute of Chemical and Bioengineering Technology, Malaysia.
Nurul Azlina M. (2005) Study on Important Parameters Affecting the Hydrodistillation for Ginger Oil Production, Master Thesis, Universiti Teknologi Malaysia, Malaysia.
Ruan R., Ye X., Chen, Doona C.J., Richardson P. (ed.) (2001) Ohmic Heating, Thermal Technologies in Food Processing, England: Woodhead Publishing Limited.
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