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Drying modelling of amylose fatty acid complex formation for reducing rapidly available glucose of geographical indication rice during high-temperature fluidisation
(2022-04-01)
Junka, Nittaya
;
Rattanamechaiskul, Chaiwat
This study analysed changes in the available glucose of geographical indication rice, Sang Yod variety, from Thailand after drying through the fluidisation technique in the temperature range of 85–115 °C. When the rice with an initial moisture content of 33.3% dry basis was dried at temperature over 85 °C, starch gelatinisation occurred. As the starch underwent gelatinisation, the orderly structure of the starch granules was partially disrupted. Thus, amylose leached out of the granules and simultaneously formed fatty acids in the rice. This created amylose fatty acid complexes (AFCs). This change was detected from the A and V type crystallinity patterns of the starch and complexes using X-ray diffractometry. When drying the rice at 115 °C, the formation of AFCs resulted in rapidly available glucose of dehulled rice decreasing from a medium-high level to a medium-low level; the slowly available glucose value also increased. The drying modelling was developed based on experimental data to explain the observed changes. The developed mathematical model could predict changes in A type crystallinity with the R<sup>2</sup> value and average of relative root mean square error of 0.9855 and 6.34%, while those of the V type changes were 0.9879 and 4.64%, respectively. This data can explain the mechanism underlying the available glucose response observed during drying.
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Mathematical modelling to control fungal growth in paddy dried using fluidisation
(2021-04-01)
Junka, Nittaya
;
Rattanamechaiskul, Chaiwat
Fungi can infect paddy from the planting process through to storage. Contaminating fungi can produce aflatoxins that can persist in the paddy and in storage until it is used to make other products. In the interests of food safety, in this study, we aimed to control the growth of fungi in paddy during storage using mathematical modelling of a drying method that uses fluidisation at temperatures of 70–150 °C. We found experimentally that an increase in the drying rate was related to an increase in the drying temperature. Drying paddy at a high temperature hardened the texture of rice when cooked, owing to the starch gelatinisation. Drying could decrease fungal growth (FG) and aflatoxin content during storage; however, it also resulted in a decrease in the antioxidant properties of paddy. Mathematical modelling and a proposed FG equation were applied to predict a suitable drying condition. The optimal drying condition reduced the risk of FG in stored paddy by ~50% without affecting antioxidant properties.
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Drying and mathematical modelling for the decelerated rancidity of treated jasmine brown rice using different drying media
(2021-01-01)
Junka, Nittaya
;
Rattanamechaiskul, Chaiwat
;
Wongs-Aree, Chalermchai
;
Soponronnarit, Somchart
Jasmine brown rice (JBR) attains a rancid odour because of lipid deterioration, which reduces its shelf life. This study focused on preserving JBR's stability through drying in a fluidised bed at 100–150 °C using different drying media: hot air (HA), humidified hot air (HHA), and superheated steam (SHS). The JBR and the rancid odour caused by thiobarbituric acid (TBA) were analysed. A mathematical model was developed for the drying process, and associated equations were formulated to predict the mechanism underlying changes in TBA during 180 days of storage. The dried samples became harder owing to gelatinisation of starch and decrease in 2-acetyl-1-pyrroline volatility. Changes in JBR quality were correlated to the drying temperature and drying media used. SHS drying at 150 °C decelerated TBA formation the most. The proposed mathematical model and associated equations can predict changes in TBA during storage accurately and be applied to JBR under most drying conditions.
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Drying guideline to control colour quality of para rubber sheet by computation method
(2018-12-01)
Junka, Nittaya
;
Rattanamechaiskul, Chaiwat
;
Prachayawarakorn, Somkiat
;
Soponronnarit, Somchart
Colour is one of the most important basic physical characteristics of dried para rubber sheets. This characteristic is used to determine the standards and trading prices. In this research, a mathematical model and a colour change equation were developed for para rubber sheet drying in a hot air oven, with the yellowness index (YI) as an indicator. The results show that the mathematical model provides validation of the moisture change and that the first-order rate reaction equation gives a satisfactory prediction of the colour change. The determination coefficient for every drying condition is between 0.9080–0.9742 and 0.9273–0.9813. Suitable drying conditions were used in the simulation using the model and equation, and the shortest drying time was applied in the study. Moreover, the colour value of the simulated para rubber sheet is not higher than that of the reference Unsmoked Sheet (USS) whose moisture is decreased by sun drying and is still in the best standard range.

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