จลนพลศาสตร์และสมบัติทางกายภาพของการอบแห้งลำไยเนื้อที่ผ่านสนามไฟฟ้าแบบพัลส์

Abstract

In this study, pulsed electric field was pretreated prior to drying of flesh longan in order to study the effects of pulsed electric field on physical properties and drying time. Peeled and pitted longan was treated in the pulse electric field intensity of 3 kV/cm, 3 frequencies of 6 ,8 and 10 Hz. The treated flesh longan was dried with hot air tray dryer at the constant temperature of 70 C until the moisture content reached 16% (w.b.). Analyze the drying kinetics and measure the energy consumption. Including checking the physical properties that have changed. The cell structure were examined with a 2,000-time scanning electron microscope(SEM). The results showed that cells of dried longans pre-treatment by PEF provided more porosity increase in void space varies with the frequency of the electric field compared to normal longan. The change of porosity provided drying time 405 370 and 355 minutes according to frequency 6 8 and 10 Hz respectively. The drying time of no PEF was 452 minutes. Resulting in a 26% reduction in drying energy. All PEF-treated dried longan samples had Aw values lower than 0.6 according to the dried fruit standard. The texture is softer because the stress value is reduced by 35.29%. It was clearly shown that the PEF causes more porosity in the cell affecting the higher water mass transfer while drying. Energy consumption decreased. As a result, the drying time is reduced and better appearance due to shorter time of drying process. The quality of the dried longan pre-treatment by pulsed electric field was within the acceptable range.