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Impact of processing method and growing location on overall differences of brewed coffee using electronic tongue and sensory panel
(2017-11-25)
Kulapichitr, F.
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Suppavorasatit, I.
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Borompichaichartkul, C.
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Chodjarusawad, T.
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Phatthara-aneksin, A.
Arabica coffee beans from two different locations (Doi Tung and Doi Chang, Chiang Rai, Thailand) were processed through civet cat (free-range), civet cat (caged) and normal wet processing. The beans were ground and brewed using a standard steeping method. Coffee samples were evaluated using an electronic tongue and a sensory panel for overall differences. Coffee samples from different processes and locations were clearly differentiated by the electronic tongue. Differences between the processes (civet cat (free-range), civet cat (caged) and normal wet-processing) were perceivably significant (>78% clearly detecting differences) between coffees from the same location (Doi Tung). However, when the location factor was introduced (Doi Chang vs. Doi Tung), the differences were reduced, and only civet coffee from different locations and different feeding methods (free-range vs. caged) was significantly different. Postharvest processing of coffee beans had a great impact on a cup of coffee; however, this impact seemed to be masked by the different locations.
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Differences in volatile compounds and antioxidant activity of ripe and unripe green coffee beans (Coffea arabica L. ‘Catimor’)
(2017-11-25)
Kulapichitr, F.
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Borompichaichartkul, C.
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Pratontep, S.
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Lopetcharat, K.
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Boonbumrung, S.
Aroma characteristics and antioxidant activity are main quality markers for a good cup of coffee. These attributes are influenced by the degree of ripeness of the coffee berries. Therefore, the aim of this study was to study the differences between ripe and unripe green coffee beans in volatile compounds and antioxidant activities to evaluate the selection process of coffee berries. Two types of green coffee beans processed from ripe and unripe coffee berries from the same plantation were characterized for their volatile components by solid-phase micro-extraction gas chromatography/mass spectrometry (SPME-GC/MS) using 2-methyl-3-heptanone as an internal standard. More than 200 peaks of volatile constituents were found in both unripe and ripe green coffee. Alcohols and ketones were the most abundant groups of volatile compounds in unripe green coffee, while the concentrations of these two groups decreased during the ripening process. In contrast, aldehydes, acids, and esters increased. Various compounds were found only in ripe green coffee, such as 1-hexanol, 2-heptanol, 2-ethyl-1-hexanol, 2,2-dimethyl-3-4-pentadienal, methyl hexanoate, methyl phenylacetate, methyl salicylate, methyl-(2E)-2-methyl-2butenoate, and 2,7-dimethyl-oxepine. In terms of antioxidant activity measurements, total phenolic content of ripe and unripe green coffee beans was 59.94±4.14 and 54.56±0.73 mg gallic acid equivalents (GAE) g-1 coffee beans; diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (%) was 71.74±5.26 and 70.68±4.78, and reducing antioxidant power by ferric-reducing antioxidant potential (FRAP) assay was 66.98±4.70 and 52.72±3.20 mg Trolox g-1 coffee beans, respectively. These results can be used as information for correct selection of coffee berries prior to other stages of coffee processing.
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Non-enzymatic urea sensor using molecularly imprinted polymers surface modified based-on ion-sensitive field effect transistor (ISFET)
(2016-11-25)
Rayanasukha, Y.
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Pratontep, S.
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Porntheeraphat, S.
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Bunjongpru, W.
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Nukeaw, J.
A novel molecularly imprinted electrochemical sensor based on ISFET device has been developed for urea detection sensor. The molecularly imprinted polymers (MIPs) were prepared by photopolymerization on the surface of ISFET device using PMMA and urea as the functional polymer and molecular template, respectively. The fabricated sensors were characterized by potentiometry and UV-Vis spectroscopy. The preparation conditions were optimized for performance of the sensors, i.e. drop-cast volume and incubation time. The MIP modified ISFET sensors has linear range response from 1.0 × 10− 4 to 1.0 × 10− 1 M with the limit of detection of 1.0 × 10− 4 M (S/N = 3). The MIP modified ISFET sensors also exhibit excellent reproducibility, repeatability and stability, as well as high selectivity to urea.
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Theoretical investigation of rhodamine6g derivative as fluorescence metal ion sensor
(2014-07-24)
Puingam, R.
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Chindaduang, A.
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Tumcharern, G.
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Sae-Tang Phromyothin, D.
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Pratontep, S.
The structural, energetic and optical properties of a Rhodamine6G derivative as the fluoroionphore for metal ion detection, particularly mercury, have been investigated using the time-dependent density functional theory (TD-DFT), compared to experiments. The TD-DFT calculations with the B3LYP method were conducted in the absence and the presence of metal ions. The results indicate that the absorption peaks of the pristine molecules are located at 236 and 282 nm, whereas the selective Hg2+ binding peaks emerge at 263, 371 and 551 nm. A distinctive new band emerges around 550 nm, in accordance with the experiments, attributed to the metal-to-ionophore electron transfer. © 2014 Taylor & Francis Group, LLC.
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A density functional theory study on the metal binding properties and electronic transitions of dithienopyrole derivatives
(2014-07-24)
Thanakit, P.
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Chittratan, P.
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Pratontep, S.
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Sae-Tang Phromyothin, D.
The metal binding energies and electronic properties of the complexes M-Py1A (M: Cd, Fe, Co, Cu, Hg, Ni, Pb, Zn; Py1A = deprotonated cyanoacetic) were studied using density functional theory (DFT) with B3LYP method. Comparative metal binding energies of metal complexes are as follows: Pb2+> Cu2+>Ni2+>Co2+>Fe2+> Hg2+>Cd2+>Zn2+. The electronic transitions of Fe, Ni, Co, Zn, Cd, Hg, Cu, and Pb are assigned as LLCT, LLCT, LMCT, LMCT, LMCT/LLCT, MLCT and LMCT, respectively. Solvation effect of Cu-Py1A complex was calculated in gas phase and tetrahydrofuran(THF). The results provide slightly red-shifted spectra from 540 to 541 nm. © 2014 Taylor & Francis Group, LLC.
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Tantalum oxide bio-photonics thin film grown by gas-timing innovation technique
(2013-09-18)
Khemasiri, N.
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Porntheeraphat, S.
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Horprathum, M.
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Chananonnawathorn, C.
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Bunjongpru, W.
Tantalum oxide (TaxOy) as high refractive index material has been grown on p-type silicon and quartz substrates by R.F. magnetron sputtering with our innovative technique called "reactive-gas timing". The reactive gas timing technique is an on-off time period sequence between argon (Ar) and oxygen (O2) plasma during sputtering process. The technique of gas-timing plays the effect on the properties of TaxOy thin film. The bombarded Ar-plasma was varied at 2, 5 and 8 sec, while the period of reactive O2-plasma was kept at 5 sec in this experiment. The physical and optical properties were investigated by using X-ray diffraction (XRD), Atomic Force Microscope (AMF), UV-Visible spectrometer and Spectroscopic Ellipsometer, respectively. The XRD spectra and AFM photographs show all films are amorphous phase with smooth feature. Meanwhile the transmittance of sputtered thin film decreases with 10% and the absorption edge shifts to lower energy with the increasing of the argon period from 2 sec to 8 sec. The refractive index as showed by ellipsometry slightly increases from 2.08 to 2.17 at wavelength 550 nm with the increasing of argon period from 2 sec to 8 sec. The increasing of the refractive index might dues to tantalum (Ta) rich which consists in thin films. The Ar-plasma period in the deposited film plays an important role on the properties of the TaxOy thin films especially as optical refractive index material. © 2013 SPIE.
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Effect of trichlorobenzene additive on the performance and morphology of polyfluorene and fullerene derivative bulk heterojunction solar cells
(2012-08-01)
Koetniyom, W.
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Keawprajak, A.
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Piyakulawat, P.
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Jiramitmongkon, K.
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Nukeaw, J.
The influence of additive, namely 1,3,5-trichlorobenzene (TCB), on the morphology and performance of bulk heterojunction (BHJ) organic solar cells was studied based on a 1:2 (w/w) blend of benzothiadiazole/thiophene-based copolymers (PFTBzTT) to [6,6]-phenyl-C <inf>61</inf> butyric acid methyl ester (PCBM). The active layers were deposited by spin-coating from solutions using chloroform, with different additive concentrations from 0 to 36mg/ml. The addition of solvent additive into the polymer solution was able to improve the performance of BHJ solar cells. The maximum power conversion efficiency (%PCE) of 0.85% was obtained for a cell with the TCB concentration of 12mg/ml after annealing at 180°C for 20min. From atomic force microscopy (AFM) images, the films processed without TCB appear smoother than those with the TCB additive. A large extent of segregation was also observed in the films processed with a high TCB concentration. The optical images of the thin films suggest that the optimum concentrations of the additive cause the polymer self-organisation, resulting in some aggregation of large PCBM crystals. © 2011 Canadian Society for Chemical Engineering.
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Theoretical and experimental problems at IPhO 42 in Thailand
(2012-01-01)
Kusamran, S.
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Srongprapa, A.
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Pruttivarasin, T.
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Kittara, P.
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Prachyabrued, W.
This paper presents both the theoretical (without solutions) and the experimental problems for the 42nd International Physics Olympiad (IPhO42) organized in Bangkok, Thailand, 1018 July 2012. Experimental problems on electrical and mechanical black boxes are given with detailed solutions. The performance of the contestants in the theoretical and the experimental sections is compared. © 2012 IOP Publishing Ltd.
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Effect of nano particle sizes on high pressure raman scattering in nanocrystalline cerium dioxide
(2011-12-20)
Jimlim, P.
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Bovornratanaraks, T.
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Chaimayo, W.
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Pratontep, S.
Nanocrystalline CeO<inf>2</inf> with different particle sizes has been studied under high pressure using Raman spectroscopy techniques and diamond anvil cell at room temperature. The pressure shift of the first-order Raman frequency for each particle sizes was measured. Linear dependence of the first order Raman frequency on pressure for each particle sizes has been observed. We found that the first order Raman frequency decreases with the decreasing particle sizes under ambient condition and the lattice constant increases with the decreasing particle size. The increasing molar fraction of oxygen vacancies with the decreasing particle size is responsible for the lattice expansion.
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Composite polymer electrolyte for dye-sensitized solar cells: Role of multi-walled carbon nanotubes
(2010-02-05)
Chindaduang, A.
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Duangkaew, P.
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Pratontep, S.
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Tumcharern, G.
We focus on the energy conversion improvement of dye-sensitized solar cells by using poly(ethylene oxide)-multi-walled carbon nanotube (PEO-MWCNT) electrolyte. Compared with the MWCNT-free solar cells, the addition of 0.05 wt.% MWCNTs in the polymer electrolyte results in a dramatic increase of the short-circuit current (J<inf>sc</inf>), consequently raising the device performance by approximately 9% under a direct light of the Air Mass 1.5 irradiation at 100 mW cm-2. The role of the conductive carbon materials in the polymer electrolyte have been investigated by means of ionic conductometry, electrochemical impedance spectroscopy and UV-visible spectroscopy. This work demonstrates that MWCNT additives in polymer electrolytes is a convenient yet effective strategy for improving the performance of photovoltaic devices. © (2010) Trans Tech Publications.

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