การจัดการข้าวเปลือกชื้นโดยการอบแห้งในที่เก็บรักษาภายใต้สภาวะอากาศเขตร้อนชื้น

Managing Moist Paddy by In-Store Drying under Humid Tropical Atmosphere

Name: ยุทธนา ฏิระวณิชย์กุล

Organization : มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

Name: Yutthana Tirawanichakul

keyword: In-Store Drying

; Mathematical Model

; Paddy

; Quality

; Whiteness

Abstract: Drying process is important to maintain quality of product and the different drying techniques may provide dissimilar product quality. There have been a few researches on the effect of slow drying technique or, in other words, in-store drying technique on the quality of dried paddy, and the pretreatment system that is reasonably applicable to treat wet paddy in order to delay its deterioration before drying. These lead us to investigate the paddy drying process on field experience at a rice merchant and preliminary study of the pretreatment systems using ambient air ventilation and silica gel to reduce the moisture inside the paddy and the in-store drying. In addition, the mathematical model, was developed to describe the phenomenological and physicochemical change while paddy is dried in a cylindrical bin under the conditions of three drying configurations; continuous near ambient air ventilation (Condition 1), continuous aeration with relative humidity controlled below 70% (Condition 2) and intermittent drying by switching fan off at higher relative humidity of 70% (Condition 3). On the field experiments, the drying system of rice merchant was a high efficiency and can maintain the uniformity of dried paddy in each drying stage. For the preliminary study of pretreatment systems of fresh paddy before drying process, the pretreatment of paddy using air ventilation is technically feasible to reduce a certain extent of moisture content. In addition, this technique not only reduces the moisture of paddy bulk, but also can reduce the accumulation of heat liberated from grain respiration. For preliminary experiment on pretreatment of fresh paddy using silica gel (packed bed), it shows the low moisture reduction of grain bulk and the drawback of this approach removes inefficiently the heat generated from grain respiration if the high temperature in the bulk is maintained for a long time. For drying using adsorption technique, the adsorbent material should thus, be well mixed with moist particles in order to effectively adsorb the water vapor evaporating from the particles and initial moisture content of paddy should be lower than 21% wet basis in order to avoid heat accumulation from respiration. At the laboratory-scale equipment, two long grain Indica rice varieties, Suphanburi 1 with a high amylose content of 25-27% and Pathumthani 1 with a low amylose content of 15-17% were dried using airflow rates of 0.6 to 1.5 m3/min-m3 of paddy. Average mass of fresh paddy was about 240?10 kg, corresponding to the height of a fixed-bed as 1.0 m. The results have shown that three drying configurations insignificantly affect the physical quality (head rice yield and yellowness), physicochemical quality (gel consistency, alkaline spreading value, pasting viscosity and texture analysis), chemical quality (amylose content, protein and total fat) and cooking quality (sensory evaluation) comparing to those qualities of paddy dried gently by ambient air aeration in a thin layer (control sample) (p<0.05). However, the amount of fat acidity of dried rice shows the increasing trend, because of the auto-oxidation and hydrolysis. The near equilibrium model proposed can describe the experimental results in terms of moisture content of paddy and rice whiteness value for three drying configurations, with a high accuracy when the respiration effect was included in the model. In addition, the predicted results of three drying configurations simulated under the flow rate of 0.75 m3/min-m3 of paddy and initial moisture content of 20% wet basis and the wet season condition (average temperature of 28.9?C and average relative humidity of 75.4%), indicated that the continuous drying using near ambient air ventilation (Condition 1) seems to be the most of interest because the specific energy consumption and decrease of rice whiteness value are relatively low when compared to the latter two drying configurations (Condition 2 and 3) whereas the high dry matter loss in the first drying technique was obviously evident, with a value of 1.02%, comparing to the value of 0.8% for condition 2.

มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

Address: กรุงเทพมหานคร

Email: info.lib@mail.kmutt.ac.th

Name: Somkiat Prachayawarakorn

Role: Supervisor

Created: 2546

Issued: 2005-08-31

Modified: 2560-09-21

วิทยานิพนธ์/Thesis

ISBN: 9744565012

CallNumber: ET576

tha

DegreeName: วิศวกรรมศาสตรดุษฎีบัณฑิต

Level: ปริญญาเอก

Descipline: เทคโนโลยีพลังงาน

Grantor: มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

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