Influence of Fluidized-bed Drying Temperature on Chemical and Physical Properties of Paddy

อิทธิพลของอุณภูมิของการอบแห้งด้วยฟลูอิไดซ์เบตต่อสมบัติทางเคมีและทางกายภาพบางประการของข้าวเปลือกชื้น

Name: Supawan Tirwanichakul

Organization : King Mongkut's University of Technology Thonburi. School of Energy, Environment and Materials. Energy Technology

keyword: Amylose Content

; Fluidized-bed Drying

Abstract: The main objective of this work was to study the influence of fluidized-bed drying using air at temperatures from 40- 150•?C on various quality parameters of Suphanburi 1 (SP1) and Pathumthani l(PT1) local Indica rice. The moisture diffusivity of paddy was determined. In addition, the mathematical model of a continuous fluidized bed drying using drying temperatures of 60-150•?C was developed for predicting the evolution of moisture and specific energy consumption.Fresh paddy was dried from the initial moisture contents of 25.0-32.5% dry-basis to 22.5f 1.2% dry-basis. After fluidized-bed drying, paddy was tempered and aerated using ambient air until its final moisture content was reduced to 16.3f0.5% dry-basis. From the moisture diffusion model, it was concluded that the effective moisture diffusivity in the Arrhenius type equation could suitably describe the moisture change.The effective moisture diffusivity was strongly related to the absolute temperature of the drying air while the Arrhenius factor depended slightly on the initial moisture content of paddy.The physical results showed that the head yield of SP1 rice, with a high amylose content, was significantly related to the inlet drying temperature and initial moisture content. On the contrary, there was no significant relationship between the head rice yield, the drying temperature and the initial moisture content for PT1, with a low amylose content (p<0.05). In addition, the whiteness value of both rice verities decreased slightly with an increase inlet air temperature and initial moisture content.From chemical analysis, the amylose content, protein content and total fat of rice after drying was not significantly different from the control sample, which was thin-layer dried using ambient air aeration, except for fat acidity which shows a decreasing trend with increased drying air temperature. This was due to the inactivation of enzyme and biological matter after drying using hot air temperature. Furthermore, percentage of germination of dried paddy was directly decreased with increase of drying air temperature and the dried paddy had no germination when it was dried using inlet drying temperature above 80•?C.From the physicochemical analysis, the alkali spreading value and gel consistency of rice flour do not change with initial moisture content and inlet drying air temperature. The change of hardness with drying temperature had a distinct difference between SPl and PT1 rice variety. However, the hardness of PT1 at individual initial moisture content was less sensitive to temperature change (p<0.05), whilst the hardness of the SPl rice was positively associated with the initial moisture content and drying temperature. For the pasting property analysis, peak and final viscosity for both rice flour with dried at low temperature drying have an insignificant difference comparing to the control rice while those of rice flour tended to decrease with increase of drying temperature. This is due to partial gelatinization effect.The thermal analysis using the differential scanning calorimeter (DSC) showed that partial gelatinization occurred during drying at inlet air temperatures above 90•?C, corresponding to morphology of the rice kernel in cross section views. The sensory evaluation of cooked rice showed that the sensory taste of cooked rice after fluidized bed drying had no significant correlation with the drying air temperatures and initial moisture contents of paddy. However, the sensory taste of cooked rice was dependent on rice variety.Considering the mathematical model of continuous fluidized bed of drying paddy, which has been developed and used for predicting the evolution of moisture and specific energy consumption, indicates that the simulated results have a good agreement to the experimental results. The paddy drying with low temperatures and low initial moisture content give higher specific thermal energy consumption and electrical energy consumption than that dried at high temperatures and high initial moisture content. The specific total energy consumption increases with decrease of fraction of air recycle. According to the simulation results, the paddy drying with fluidization technique underhigh initial moisture content and drying air temperature above 100•?C is recommended.

King Mongkut's University Technology Thonburi. Library

Address: กรุงเทพมหานคร

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

Name: Somkiat Prachayawarakorn

Role: Advisor

Name: Somchart Soponronnarit

Role: Advisor

Name: Warunee Varanyanond

Role: Advisor

Created: 2004

Issued: 2007-12-07

Modified: 2011-03-06

วิทยานิพนธ์/Thesis

CallNumber: ET638

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Energy Technology

Grantor: King Mongkut's University of Technology Thonburi

©copyrights King Mongkut's University of Technology Thonburi

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