Effective Heat Treatment Techniques for Control of Mung Bean Sprout Rot, Incorporable into Commercial Mass Production

다국어 초록 (Multilingual Abstract)

Seedlot disinfection techniques to control mung bean sprout rot caused by Colletoricum acutatum and C. gloeosporioides were evaluated for commercial production scheme. Soaking seedlots in propolis (100 X) and ethanol (20% for 30 min) appeared promising with control values of 85.5 and 80.8 respectively, but still resulted in up to 20% rot incidence. None of the C. acutatum conidia survived through hot water immersion treatment (HWT) for 10 min at temperatures of 55, 60 and $65^{\circ}C$, whereas the effective range of the dry heat treatment (DHT) was $60-65^{\circ}C$. Tolerance of mung bean seedlot, as estimated by hypocotyl elongation and root growth, was lower for HWT than for DHT. Germination and growth of sprouts were excellent over the range of $55-65^{\circ}C\;at\;5^{\circ}C$ intervals, except for HWT at $65^{\circ}C$ for 5 min. At this marginal condition, heat damage appeared so that approximately 2% of seeds failed to sprout to normal germling and retarded sprouts were less than 5% with coarse wrinkled hypocotyls. These results suggested that DHT would be more feasible to disinfect mung bean seedlots for commercial sprout production. Heat treatment at above ranges was highly effective in eliminating the epiphytic bacterial strains associated with marketed sprout rot samples. HWT of seedlot at 55 and $60^{\circ}C$ for 5 min resulted in successful control of mung bean sprout rot incidence with marketable sprout quality. DHT at 60 and $65^{\circ}C$ for 30 min also gave good results through the small-scale sprouting system. Therefore, we optimized DHT scheme at 60 and $65^{\circ}C$ for 30 min, considering the practical value of seedlot disinfection with high precision and accuracy. This was further proved to be a feasible and reliable method against anthracnose incidence and those bacterial strains associated with marketed sprout rot samples as well, through factory scale mung bean sprout production system.