การควบคุมด้วงงวงข้าวโพด (Sitophilus zeamais) และมอดฟันเลื่อย (Oryzaephilus surinamensis) ด้วยเครื่องกำเนิดคลื่นความถี่วิทยุต้นแบบระดับวิสาหกิจขนาดกลางและขนาดย่อม

Abstract

The efficacy of Radio Frequency Generator Prototype for Small and Medium Enterprises (RF) was tested for the control of maize weevil, Sitophilus zeamais attacking in 1 kilogram of 70% mixed rice (70% Hom Mali rice: 30% white rice) in polyethylene (PE) bags (100 µm thickness) by applying 27.12 MHz radio frequency with electric power of 370, and 380 volts for 3 minutes. The result showed that adult maize weevil was the most tolerant stage to the RF heat treatment comparing among egg, larval and pupal stages. Maize weevil which its egg was found inside rice kernel when they were in rice bag and exposed to RF at 380 volts for 3 minutes. The result showed that egg was not able to hatch and showed 100% mortality. For the egg of sawtoothed grain beetle, Oryzaephilus surinamensis which easily infested in packaged rice, the RF electric power of 370 and 380 volts for the 3-minute exposure also caused completely 100% mortality. The effect of types of packageing PE bags and polypropylene (PP) bags (75 µm thickness) on the mortality of maize weevil was examined. The results showed mortality of maize weevil exposed to 380 volts for 3 minutes of RF treatment in those types of packaging were not significant difference in mortalily.The temperatures of rice kept in PP bags when exposed to RF at 370, 380, 390 and 400 volts were 76.74±14.96, 78.09±12.45, 86.15±6.90, and 86.44±7.18 degree Celcius, respectively. It was higher than in the PE bags with the temperature which showed as 64.82±3.44, 65.14 ±3.18,69.11±3.31, and 69.02±3.64 degree Celcius, respectively. Moisture content of 70% mixed rice (70% Hom Mali rice: 30% white rice) showed slightly changed, however it was about 11% . The RF treatment also performed on 100% Hom Mail rice to control maize weevil. The electric powers of 380 volts and exposure time at 3 and 4 minutes were applied to 100% Hom Mail rice. The completely control of maize weevil which infested in 100% Hom Mail rice was found using the RF heat treatment for 4 minutes with the electric power of 380 volts, while the heat treatment for 3 minutes caused 99.50±1.05, and 99.40±1.26% insect mortality in PE and PP, respectively. Rice temperature of 100% Hom Mail rice in PE rice bag (71.28±4.28◦C) was lower than in PP bag (78.31±6.60◦C) when treated with RF at 380 volts for 4 minutes. Moisture contents of 100% Hom Mali rice at before and after the RF treatment were slightly changed in the range of 9-10% but there were not significantly different (P>0.05). Rice quality assessment revealed that amylose content , rice cracking, whiteness and viscosity of the starch compared to control were slightly changed.