Improved Principal Component Analysis and Linear Discriminant Analysis for the Determination of Origin of Coffee Beans using

In this work an improved Principal Component Analysis (pca) method is used for better determination of geographical origins of Ethiopian Green Coffee Beans. In the commercially available and widely employed pca methods the dataset is commonly normalized using Z-score procedure, which reduces the influence of the spread of data (or dispersion degree differences) on principal components (pcs). In the improved method, a new normalization procedure is introduced with the aim to improve the spread (dispersion) of data points around the mean. The pcs computed from the improved procedure could significantly better reflect information of the original dataset. The dispersion degree information in the original dataset was retained relatively much by using the improved pca than the Z-score-based pca. The improved pca was then used to identify the most discriminating variables corresponding to the coffee samples and, based on that, Linear Discrimination Analysis (lda) model was developed to classify and predict samples. The recognition and prediction abilities of the improved pca and lda at regional level respectively were 95.7% and 94% (using Chlorogenic Acids (cga s) content), 91% and 97% (using Fatty Acids (FA) content), 99% and 100% (and using the combined cga and FA contents). Mehari et al. (2016, 2019) reported recognition and prediction of the pca, they applied on the same dataset, at regional level were 91% and 90% (using cga s content) and 95% and 92 % (using fas content), respectively. The result reveals that the newly introduced method is superior and the best discriminations of coffee beans were achieved. The combined analysis of cga and fa concentrations is a useful tool for the determination of origin of coffee beans, and we recommend that the concerned bodies should use it to address the characterization, classification and authentication of Ethiopian coffee beans according to their geographical origins

Total phenolics and antioxidant capacity of the white and brown teff [Eragrostic tef (Zuccagni) trotter] varieties cultivated in different parts of Ethiopia

ABSTRACT. This study was aimed to determine the total phenolics contents and antioxidant capacity of white and brown teff grain samples. The free total polyphenolic content (TPPC), bound TPPC and total flavonoids content ranged from 62.1–129.9, 84.6–189.6 mg GAE/100 g and 84.4–195.1 mg QE/100 g, respectively, in white teff samples, and, 118.6–196.7, 141.1–195.1 mg GAE/100 g and 97.8–202.5 mg QE/100 g, respectively, in brown teff samples. Besides, the free 2,2-diphenyl-1-picrylhydrazyl (DPPH) and bound DPPH ranged from 74.8–98.3, 77.1–99.9 mg AAE/100 g, respectively, for white teff samples, and, 68.7–93.1 and 71.2–99.4 mg AAE/100 g, respectively, for brown teff samples. This study revealed that total phenolics content was higher in brown teff samples than white teff samples and is in agreement with other reports. However, their DPPH scavenging activities were nearly equal, indicating that both varieties of teff are relevant for human nutrition and health. Furthermore, the dendrogram has shown sharp separation of the samples based on their origin and variety related to the total phenolics parameters. Hence, findings of this study can help consumers appreciate the nutritional value of white and brown teff grains; provide them guidance for teff purchase and production.   KEY WORDS: Teff, Phenolics, Gallic acid, Ascorbic acid, Anti-oxidant, DPPH   Bull. Chem. Soc. Ethiop. 2022, 36(4), 749-766.                                                              DOI: https://dx.doi.org/10.4314/bcse.v36i4.3                                                       &nbsp

New analytical methods for the determination of ascorbic acid content in aqueous extracts of flesh, peel and seeds of pumpkin (Cucurbita maxima)

ABSTRACT. The main objective of this research was to develop a simple, rapid, cost-effective, and environmentally friendly methods for determining ascorbic acid in flesh, peel, and seeds of pumpkin. Ascorbic acid was extracted from the different parts of the pumpkin in water. The content of ascorbic acid in three parts of the pumpkin was determined using ATR-FTIR and UV-VIS methods. The ATR-FTIR method was validated to determine ascorbic acid at 1046 cm-1, and the results indicated a linear range of 5 to 50 g/L; R2, 0.999; LOD, 1.7 g/L; LOQ, 5.2 g/L; RSD, 0.09% to 0.65%, and %recovery of 95.86%. Ascorbic acid was also determined at 265 nm by the UV-VIS method that revealed a linear range of 1 to 12 mg/L; R2, 0.999; LOD, 0.25 mg/L; LOQ, 0.75 mg/L; RSD, 0.12% to 0.43%, and %recovery of 96.96%. Accordingly any of the two newly developed methods can easily be applied for quantitative determination of ascorbic acid in pumpkin flesh, peel, and seeds. Both methods yielded higher ascorbic acid content in pumpkin seeds than in pumpkin flesh and peel. Both ATR-FTIR and UV-VIS spectroscopic methods are green, low cost and rapid method. However, UV-VIS method showed higher sensitivity than the ATR-FTIR method.   KEY WORDS: Pumpkin, Cucurbita maxima, Ascorbic acid, ATR-FTIR spectroscopy, UV-VIS spectrophotometry   Bull. Chem. Soc. Ethiop. 2022, 36(2), 277-290.                                                             DOI:https://dx.doi.org/10.4314/bcse.v36i2.3                                                        &nbsp

Hocheffiziente photorefraktive Gläser auf Basis eines nicht aggregierenden elektrooptischen Chromophors

In dieser Arbeit wurden neue hocheffiziente photorefraktive Gläser auf Basis des Chromophors IDOP20 entwickelt. Der Chromophor wurde zunächst anhand der Kerr-Gütezahl auf seine Eignung für PR-Anwendungen überprüft. Es konnte eine relativ große Kerr-Gütezahl bestimmt werden. Durch die sterisch anspruchsvollen 3,3’-Dimethylmethylen-Gruppen wird in diesem Chromophor die Neigung zur Dimerenbildung weitgehend unterdrückt. Für mehrere photorefraktive Gläser mit IDOP20 als elektrooptischem Chromophor konnten sehr hohe Verstärkungskoeffizienten Gamma erzielt werden. Für das Glas der Zusammensetzung IDOP20:2BNCM:DPP:TPD:TNFM 30:25:20:24:1 Gew.-% wurde mit einer Nettoverstärkung von Gamma_net = 178 1/cm ein der bisher größten Werte bei einer Feldstärke von E = 45 V/µm erzielt. Weiterhin konnte der Polymeranteil in den photorefraktiven Gläsern vollständig durch glasbildende Co-Chromophore ersetzt werden. Dadurch wurde die Phasenseparation und Kristallbildung in den photorefraktiven Gläsern unterdrückt und die Stabilität und die optische Qualität der Gläser verbessert. Die glasbildenden Eigenschaften von IDOP20 wurden durch dynamische Differenz-Kalorimetrie-Messungen nachgewiesen werden. Der Chromophor bildet einen Charge-Transfer-Komplex mit dem Sensibilisator TNFM. Weitere quasistationäre und zeitabhängige holographische und ellipsometrische Messungen wurden an einem Glas mit zugesetztem Weichmacher DPP (zur Herabsetzung der Glasübergangstemperatur) der Zusammensetzung IDOP20:DPP:TNFM 69:30:1 Gew.-% durchgeführt. Dabei konnte eine Brechungsindexmodulation von Delta n = 0.009 bei einer Feldstärke 60 V/µm ermittelt werden. In zeitabhängigen Messungen wurde ein monoexponentieller Verlauf des photorefraktiven Gitteraufbaus beobachtet. Weiterhin wurde eine sehr starke Temperaturabhängigkeit der Antwortzeiten festgestellt und die Dynamik der Molekülorientierung als zeitbestimmender Prozess identifiziert. Die photorefraktive Leistung der IDOP20-Gläser wurde im Vergleich zu ATOP1-Gläsern diskutiert

Hocheffiziente photorefraktive Gläser auf Basis eines nicht aggregierenden elektrooptischen Chromophors

In dieser Arbeit wurden neue hocheffiziente photorefraktive Gläser auf Basis des Chromophors IDOP20 entwickelt. Der Chromophor wurde zunächst anhand der Kerr-Gütezahl auf seine Eignung für PR-Anwendungen überprüft. Es konnte eine relativ große Kerr-Gütezahl bestimmt werden. Durch die sterisch anspruchsvollen 3,3’-Dimethylmethylen-Gruppen wird in diesem Chromophor die Neigung zur Dimerenbildung weitgehend unterdrückt. Für mehrere photorefraktive Gläser mit IDOP20 als elektrooptischem Chromophor konnten sehr hohe Verstärkungskoeffizienten Gamma erzielt werden. Für das Glas der Zusammensetzung IDOP20:2BNCM:DPP:TPD:TNFM 30:25:20:24:1 Gew.-% wurde mit einer Nettoverstärkung von Gamma_net = 178 1/cm ein der bisher größten Werte bei einer Feldstärke von E = 45 V/µm erzielt. Weiterhin konnte der Polymeranteil in den photorefraktiven Gläsern vollständig durch glasbildende Co-Chromophore ersetzt werden. Dadurch wurde die Phasenseparation und Kristallbildung in den photorefraktiven Gläsern unterdrückt und die Stabilität und die optische Qualität der Gläser verbessert. Die glasbildenden Eigenschaften von IDOP20 wurden durch dynamische Differenz-Kalorimetrie-Messungen nachgewiesen werden. Der Chromophor bildet einen Charge-Transfer-Komplex mit dem Sensibilisator TNFM. Weitere quasistationäre und zeitabhängige holographische und ellipsometrische Messungen wurden an einem Glas mit zugesetztem Weichmacher DPP (zur Herabsetzung der Glasübergangstemperatur) der Zusammensetzung IDOP20:DPP:TNFM 69:30:1 Gew.-% durchgeführt. Dabei konnte eine Brechungsindexmodulation von Delta n = 0.009 bei einer Feldstärke 60 V/µm ermittelt werden. In zeitabhängigen Messungen wurde ein monoexponentieller Verlauf des photorefraktiven Gitteraufbaus beobachtet. Weiterhin wurde eine sehr starke Temperaturabhängigkeit der Antwortzeiten festgestellt und die Dynamik der Molekülorientierung als zeitbestimmender Prozess identifiziert. Die photorefraktive Leistung der IDOP20-Gläser wurde im Vergleich zu ATOP1-Gläsern diskutiert

Development of new analytical methods for the determination of caffeine content in aqueous solution of green coffee beans

Abstract Background This study was conducted to develop fast and cost effective methods for the determination of caffeine in green coffee beans. In the present work direct determination of caffeine in aqueous solution of green coffee bean was performed using FT-IR-ATR and fluorescence spectrophotometry. Caffeine was also directly determined in dimethylformamide solution using NIR spectroscopy with univariate calibration technique. Results The percentage of caffeine for the same sample of green coffee beans was determined using the three newly developed methods. The caffeine content of the green coffee beans was found to be 1.52 ± 0.09 (% w/w) using FT-IR-ATR, 1.50 ± 0.14 (% w/w) using NIR and 1.50 ± 0.05 (% w/w) using fluorescence spectroscopy. The means of the three methods were compared by applying one way analysis of variance and at p = 0.05 significance level the means were not significantly different. The percentage of caffeine in the same sample of green coffee bean was also determined by using the literature reported UV/Vis spectrophotometric method for comparison and found to be 1.40 ± 0.02 (% w/w). Conclusion New simple, rapid and inexpensive methods were developed for direct determination of caffeine content in aqueous solution of green coffee beans using FT-IR-ATR and fluorescence spectrophotometries. NIR spectrophotometry can also be used as alternative choice of caffeine determination using reduced amount of organic solvent (dimethylformamide) and univariate calibration technique. These analytical methods may therefore, be recommended for the rapid, simple, safe and cost effective determination of caffeine in green coffee beans

New fluorescence spectroscopic method for the simultaneous determination of alkaloids in aqueous extract of green coffee beans

Abstract Background There is no fluorescence spectroscopic method for the determination of trigonelline and theobromine in green coffee beans. Therefore, the objective of this study was to develop a new fluorescence spectroscopic method to determine the alkaloids simultaneously in the aqueous extract of green coffee beans. Results The calibration curves were linear in the range 2–6, 1–6, 1–5 mg/L for caffeine, theobromine and trigonelline, respectively, with R2 ≥ 0.9987. The limit of detection and limit of quantification were 2, 6 and 7 µg/L and 40, 20 and 20 µg/L for caffeine, theobromine and trigonelline, respectively. Caffeine and trigonelline exhibited well separated fluorescence excitation spectra and therefore the two alkaloids were selectively quantified in the aqueous extract of green coffee. While theobromine showed overlapping fluorescence excitation spectra with caffeine and hence theobromine could not be determined in the aqueous extract of green coffee beans. The amount of caffeine and trigonelline in the three samples of green coffee beans were found to be 0.95–1.10 and 1.00–1.10% (w/w), respectively. The relative standard deviations (RSD ≤ 4%) of the method for the three compounds of interest were of very good. The accuracy of the developed analytical method was evaluated by spiking standard caffeine and trigonelline to green coffee beans and the average recoveries were 99 ± 2% for both the alkaloids. Conclusions A fast, sensitive and reliable fluorescence method for the simultaneous determination of caffeine and trigonelline in the aqueous extract of green coffee beans was developed and validated. The developed method reflected an effective performance to the direct determination of the two alkaloids in the aqueous extract of green coffee beans

Chemical Composition of Yushania alpina (K. Schum.) W.C.Lin (1974) (Highland Bamboo) Grown in Ethiopia

Chemical properties of any lignocellulose species are one of the major properties that used to select the material for any purpose either chemical or biological. Since bamboo is one of the woody grass species used for various applications worldwide; therefore knowing the chemical composition plays greater a role. Based on the above assumption, this research was conducted to study the major chemical composition of Yushania alpina (K. Schum.) W.C.Lin (1974) (Highland Bamboo) grown around Enjibara in Ethiopia. In the work, Yushania alpina (Highland Bamboo) sample was harvested, dried, milled using a Wiley Mill, sieved and all chemical composition were determined based on the National Renewable Energy Laboratory (ASTM) approaches, except that the Kurschner-Hoffer method (1931) was applied for cellulose determination. Based on the study, the chemical composition characterization shows that Yushania alpina has 46.76% cellulose content, 25.27% lignin content, 12.18% hemicellulose, 3.77% ash, 12.23% hot-water extractive and 3.93% ethanol-toluene extractives

MOESM1 of Preparative HPLC for large scale isolation, and salting-out assisted liquid–liquid extraction based method for HPLC–DAD determination of khat (Catha edulis Forsk) alkaloids

Additional file 1: Figure S1. Optimization of volume of 1% HAc and H2O for extraction of (a) norpseudoephedrine (NPE) or cathine, (b) norephedrine (NE) and (c) cathinone (CA)

Improvement in Analytical Methods for Determination of Sugars in Fermented Alcoholic Beverages

The main objective of this study was to improve the performance of analytical methods for the determination of sugars in fermented alcoholic beverages based on mid-infrared-partial least squares (MIR-PLS), high-performance liquid chromatography with the ultraviolet detector (HPLC-UV), high-performance liquid chromatography with the refractive index detector (HPLC-RI), and sulfuric acid methods. The MIR-PLS method was found to give good prediction of individual sugars: glucose, fructose, sucrose, and maltose in the alcoholic beverages with less than 4% error. The HPLC-UV method can be used for the determination of glucose in alcoholic beverages after derivatization with p-aminobenzoic acid ethyl ester. The HPLC-RI method was found to be applicable for the determination of individual sugars: glucose, fructose, sucrose, and maltose in the alcoholic beverages. The limit of detection (%, w/w) and recovery (%) of the individual sugars by the HPLC-RI method were fructose 0.001, 89.4–106; glucose 0.002, 92.4–109; and sucrose 0.002, 94.2–95.1. The sulfuric acid method was found to be useful for the determination of total sugar in the alcoholic beverages. The limit of detection (%, w/w) and recovery (%) of the total sugar by the sulfuric acid method were found to be 0.009, 98.2–109. The HPLC-RI method was applied to determine the level of individual sugars, while the sulfuric acid method was used to determine total sugar in Ethiopian traditional fermented alcoholic beverages: Tella, Netch Tella, Filter Tella, Borde, Tej, Korefe, Keribo, and Birz. The sugar contents in the real samples were found in the ranges (%): glucose 0.07–5.60, fructose 0.09–8.50, sucrose and maltose 0.08–3.00, and total sugar 12.0–64.5. The levels of sugars in Ethiopian traditional fermented alcoholic beverages were found to be comparable with literature data