Indian Journal of Agricultural Sciences 71 (4) : 287-9, April 2001 Effect of electro-mechanical colour sorting on seed quality in pigeonpea (Cajanus cajan) cuItivar 'Pusa 33'* J P SINHAI, MANO] KUMAR and VISHWAKARMA 2 Regional Station, Indian Agricultural Research Institute, Kamal, Haryana 132 001 Received: 7 September 2000 Key words: electro-mechanical colour sorting. seed quality, pigeonpea Pulse crops have been reported susceptible to weather damage (Lawan and Russel 1978) and this provides a major constraint in the availability of quality seeds of pulses. The most obvious symptoms of weather damage (rainwater wetting and field drying during the crop growth) are visual changes in seed coat of weathered seeds (William et at. 1995). These symptoms include fading/discoloration, wrinkling, cracking and! or sprouting of seed. The visual symptoms of weather damage are associated with underlying physiological changes to a seed and its seed coat, which in turn reduce the seed quality (germination value, vigour and storability). Fading and discoloration may be classified as primary weather damage and further deterioration as secondary damage. The conventional post harvest processing methods, ie winnowing, screen grading and specific gravity separation removes the secondary weather damaged seeds. However, the discoloured seed, which represent primary weather damage could not be removed and require special technique to get separated from the seed lot. The present study was conducted to analyze the performance of seed separation process by hand picking (manual sorting) and machine sorting on colour basis. Such separated seeds have been assessed for quality paramerters like germination percent, vigour index, electrical conductivity, particle density and test weight, to examine quality of separation. Performance indices for colour separation process were evaluated to examine the degree of separation. Experimental technique The experimental material was breeder seed of pigeonpea (Cajanus cajan) 'Pusa 33' of kharif1998. After conventional seed processing, seed germination percent was found much below the minimum seed certification standards. The processed seed lot contained significant amount of discoloured seed. Hence, in order to separate the undesirable discoloured seed from the jot, manual sorting and electro- *Short note iScientist, 2Assistant Foreman mechanical colour sorting methods were adopted. The electronic colour sorting machine (Make- Anazi Mfg. Co. Japan, Model - Alsomac BTC - 02) is comprised feeder, background filters, ejectors, photoelectric sensors, light source and a microprocessor. The sensors scan the seed individually and compare its colour with the colour of pre-selected background filter. If the colour of seed coat does not match with the colour of background filter, a signal through the microprocessor activates the ejectors to deflect the seed into reject port. Conversely, when the colour of seed coat match properly with color of background fi1 ler (desired colour), seed follows its normal path and collected in product port. At steady state of operation,. SOD g samples were drawn from product stream and reject stream. The samples were analysed for colour purity. The material collected in product and reject ports was weighed to reckon the recovery and rejection. A team of workers was deployed for manual sorting. Each worker was instructed to sort the desired coloured seed by comparing it with a reference colour card. The samples of feed, product and reject of both manual and machine sorting were subjected to seed quality analysis as per ISTA rules (ISTA 1993). The sampling was done in six replications. The germination per cent, number of abnonnal seedlings and dead seeds was recorded. Ten normal seedlings of each replication were drawn at random and were subjected to reckon vigour index (VI) on dry weight basis. The electrical conductivity (Ee) of seed leachates, true density (TJ)), test weight (TW) of 1000 seeds was also measured. In case of machine sorting, the material collected in product port and reject port were subjected to mUlti-pass to recover maximum number of good seeds from the seed lot. In addition, all exercise was done to find out the performance of colour sorter at different levels of colour purity. Analytical technique Good coloured seed was designated as "Product" and discoloured seed as "Reject". In ideal situation, all the good seed should go in product stream and all the discoloured seed in reject stream. Performance indices Ep, J, I were