Microwave Spectroscopy and its Applications in online Processing Neelam Upadhyay*, Ankit Goyal and Gopal Rathod National Dairy Research Institute, Karnal, Haryana. India-13200f neelam_29 I 2 @yahoo. co.in Abstract M icrowave spectroscopy or rotati o nal spectroscopy studies absorption of microwaves (usually measured in 0.3 to 3.20 CHz) by molecules associated with a corresponding change in the rotational quantum number of the molecule. The transmission coefficient can be determined by computing the attenuation and phase shift which deoends on dielectric constant and dielectric loss of the molecules. Non-contact reflectance mode microrvave and guidedmicrowave spectroscopy are the different instrumental principles used in online monitoring of different components of food. lt marksa significant step forward in food processing technology- its abilityto deliver consistent measurements and generate usable data eliminates the need for multiplelaboratory samples, saving bothtime and valuable resources. lt optimizes up time and promotes continuous productivity. The main drawback of this technique is the complexspectra that are not easily interpretable than mostothertechniques. Introduction Spectroscopy is the branch of science which deals with the study of interaction of electromagnetic radiations with matter.The term 'electromagnetic radiation' represents the radiant energy emitted from any source in the form of light, heat, etc. some important characteristics of these electromagnetic radiations aregiven below: They havedual character i.c. particle character aswell as wave character. For example, a beamof lightis a stream of particles called photons moving through the space in the form of waveS. Thesewaves are associated with electric and magnetic f i el d s oscillating perpendicular to eachother and also perpendicular to the direction of propagation. ]0-12 l0't Frequcncy (Hr,) AII electromagnetic radiations travel with the velocity o f light, c (:2.998 x 108 msl). Thewavelength )" of the electromagnetic radiation is related to their frequency (v) and velocity (c) according to the equation c: )"v. Electromagnetic radiations are made up of photons. Each photonis a packet of energy whose energy is givenby Planck's equation viz. E: hv n,here, h is Planck's constant (: 6.6262x 101) .ls). Regions of Electromagnetic spectrum: When the different types of electronragnetic radiations are arranged in order of their inr reasing w'avelengths or decreasing frequencies, the complete arrangenrent is called electromagnetic. spe'<:trum. The regions into rvhich the electromagnetic radiations have beenclassified is on the basis of theirsource and detectors required. The different radiations differin their physical and chenrical effects because they possess different enerSres. Core Valcnce elcctrons clectons Vibrations Rotations @@i 106 10r 'i t l0-r 10.{ tt)-e 1 X U.V. I fR. Extra High (mn) High Frequency F.nergy (eV) Lon Frequency *66, 2.4.5 6tlz visible {0.4,0.8$) SuPra High (cm) Ultra High (dm) il) Thatis why theyarecalled electromagnetic waves lndian Food Industry r 30 (5 & 6),Sept. - Dec. 2011 @