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Öğe Applied microwave power estimation of black carrot powders using spectroscopy combined with chemometrics(Taylor & Francis Inc, 2022) Keskin, Muharrem; Soysal, Yurtsever; Celiktas, Nafiz; Sekerli, Yunus EmreThe level of applied microwave power is a critical parameter for the quality of the dried product in microwave drying. It is impossible to assess the applied power of the dried product with the naked eye. This work aimed to predict the applied power of black carrot powders using a chromameter and near-infrared reflectance spectroscopy with partial least squares regression. A good correlation was found between applied power, color parameters, and near-infrared reflectance. The near-infrared spectroscopy predicted the applied power with better performance (R-2 = 0.99) and can be utilized to appraise the applied power of black carrot powders with acceptable accuracy.Öğe Appraisal of Three Proximal Sensing Systems to Estimate Macronutrient Contents of Detached Soybean Leaves(Taylor & Francis Inc, 2021) Keskin, Muharrem; Say, Sait M.; Sekerli, Yunus Emre; Sehri, MustafaOverapplication of fertilizers is common and may lead to plant toxicity and pollution of water resources in agriculture. A practical method is needed to estimate nutrient stress quickly, easily, and economically for a sustainable management. This study dealt with the prediction of leaf moisture content (MC) and macronutrient contents including nitrogen (N), phosphorus (P), and potassium (K) of soybean leaves using three different optical instruments of chromameter, chlorophyll meter and fluorometer. Forty-five leaf samples from a commercial soybean field were obtained. Color parameters (L*, a*, b*), SPAD (soil plant analysis development) values and quantum yield (QY) values were quantified for each leaf sample. Leaf and soil samples were analyzed using standard leaf and soil chemical analysis procedures. Correlation analysis, principal component analysis (PCA) and partial least square regression (PLSR) were used for data analysis. High correlation was found between two color parameters (L* and b*) with MC and macronutrient contents (r >= 0.65) and also, among SPAD, QY, MC, and macronutrient contents (r >= 0.70). The prediction models were evaluated based on the RMSEP (root mean square error of prediction) and R (2) (coefficient of determination) values. The results showed that soybean leaf N content can be estimated using all three optical instruments with chromameter giving slightly better results (RMSEP = 0.23%, R (2) = 0.80). Concerning the MC, chlorophyll meter gave slightly better prediction performance (RMSEP = 2.69%, R (2) = 0.73) than the other two instruments. Hence, results suggest that these three optical instruments can be used to assess the macronutrient contents of soybean leaves quickly, easily, and economically.Öğe Characterization of aroma and phenolic composition of carrot (Daucus carota 'Nantes') powders obtained from intermittent microwave drying using GC-MS and LC-MS/MS(Elsevier, 2020) Keser, Duygu; Guclu, Gamze; Kelebek, Hasim; Keskin, Muharrem; Soysal, Yurtsever; Sekerli, Yunus Emre; Arslan, AyselCarrot is an important food in human nutrition. The effects of different microwave (MW) powers on the aroma, phenolic and antioxidant properties of MW-dried and powdered carrot samples were investigated. Fresh carrot samples (Daucus ca rota 'Nantes') were dried using seven different MW power levels of 150, 200, 250, 300, 350, 400 and 450 W (0.50, 0.67, 0.83, 1.00, 1.17, 1.33 and 1.50 W/g, respectively). The aroma compounds of the carrot samples were extracted by purge and trap method and determined by gas chromatography-mass spectrometry (GC MS). In fresh samples, terpenes were identified as the dominant aroma group and a significant reduction was found in the amount of these compounds depending on the applied MW power level. Terpinolene, (E)-gamma-bisabolene, elemicin and myristicin were identified as dominant terpenes. In the dried samples, aldehydes, furans, alcohols, acids and pyrazines were determined as major components depending on the applied MW power levels. Hexanal, 3-methyl-butanal, acetic acid and hexanoic acid were dominant in the dried samples. For the determination of the phenolic compounds, the method of liquid chromatography coupled with tandem mass spectrometry (LC MS/MS) was employed. As a result of the analysis, a total of seven phenolic compounds, two of which were more dominant (3-caffeoylquinic acid and di-caffeic acid derivative) were identified. The total phenolic content of the carrot samples dried with lower MW power level of 150 and 200 W (0.50 and 0.67 W/g) was found to be relatively better preserved. When both aroma and phenolic compounds were evaluated, it was observed that they were better preserved in the carrot samples dried with low MW power levels (150 and 200W). (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Characterization of volatile compounds and organic acids in ultra-high-temperature milk packaged in tetra brik cartons(Taylor & Francis Inc, 2017) Dursun, Ahmet; Guler, Zehra; Sekerli, Yunus EmreA study was conducted to evaluate the basic chemical composition, organic acids and volatile compound profiles of ultra-high-temperature milk samples sold in Turkey. The organic acids were determined by reverse-phase high-performance liquid chromatography method, and volatile compounds were analyzed by headspace solid phase micro-extraction/gas chromatography/mass spectrometry technique. A total of 43 volatile compounds including 4 aldehydes, 5 alcohols, 10 ketones, 9 acids, 9 aromatic hydrocarbons, 3 nitrogenous, 2 sulfur containing compounds, and 1 alkane hydrocarbon, were identified in the ultra-high-temperature milk samples. The main compounds were found to be oxime methoxy phenyl, 2-heptanone, 2-mercapto-4-phenylthiazole, 2-amino-5-ethoxycarbonyl benzophenone, acetic acid, 2,6,10,14-tetramethyl pentadecane, and 2-nonanone. The main organic acid in the ultra-high-temperature milk was citric acid a mean value of 133 mg/100 mL, followed by formic, lactic, succinic, oxalic, acetic, orotic, propionic, pyruvic, hippuric, and uric acids.Öğe Comparative Appraisal of Three Low-Cost GPS Speed Sensors with Different Data Update Frequencies(Mdpi, 2021) Akkamis, Mustafa; Keskin, Muharrem; Sekerli, Yunus EmreLow-cost GPS (Global Positioning System) speed sensors have been available to quantify vehicle speed on different platforms including agricultural tractors in precision agriculture applications such as yield monitoring, variable rate fertilizer and pesticide applications. One of the advances in low-cost GPS receivers is the higher data update frequencies. However, we found no studies on the accuracy of low-cost GPS speed sensors with different update frequencies, especially under variable speed conditions. Thus, this work investigated the effect of the update frequency on the accuracy of low-cost GPS speed sensors under both constant and varying speed conditions. Three GPS speed sensors with update frequencies of 1 Hz, 5 Hz and 7 Hz (GPS1Hz, GPS5Hz and GPS7Hz) were simultaneously tested under the same conditions. A total of 144 tests were conducted on three different days and at three different times of each day with four speed levels and four repetitions. The percent errors were found to be up to 2.3%, 1.8% and 1.4% at constant speeds; up to -47%, -16% and -12% at the increasing speeds and 24%, 6% and 5% at the decreasing speeds, depending on the acceleration and deceleration levels, for GPS1Hz, GPS5Hz and GPS7Hz, respectively. The differences among the error values of the GPS speed sensors were found to be statistically significant (p < 0.05). The GPS speed sensors with higher update frequencies (5 and 7 Hz) provided higher accuracy compared to the one with lower frequency (1 Hz), particularly in the case of higher acceleration conditions. In sum, low-cost GPS speed sensors with higher update frequencies should be used for better accuracy, especially in variable speed conditions.Öğe Comparative assessment of volatile and phenolic profiles of fresh black carrot (Daucus carota L.) and powders prepared by three drying methods(Elsevier, 2021) Keskin, Muharrem; Guclu, Gamze; Sekerli, Yunus Emre; Soysal, Yurtsever; Selli, Serkan; Kelebek, HasimDrying is a common method in the post-harvest processing of fruits and vegetables and it can play a crucial role on the quality of the final product. This work examined the influence of three drying processes (freeze-drying: FD, intermittent microwave drying: IMWD and hot air convective drying: HACD) on the aroma and phenolic constituents of black carrot which is an essential vegetable in terms of its nutritive and health benefits. It was found that the drying process had substantial effects on the aroma and phenolic compositions of the black carrot powder samples. GC-MS analysis revealed a total of 32 volatiles in all samples. The FD samples had more numbers of aroma compounds after the fresh samples. Prevailing aroma groups were terpenes and alcohols. The highest amount of volatiles was found in the FD samples meaning that the FD played a crucial role in conserving the volatiles as compared to the HACD and IMWD. HPLC-DAD-ESI-MS/MS analysis yielded 34 constituents including 22 colorless phenolics and 12 anthocyanins. Regarding the phenolics, the highest amount was quantified in the HACD and IMWD samples. Chlorogenic acids were the major phenolic acids. The FD and IMWD caused a decline in the amount of anthocyanins while HACD resulted in an increase. Sensory analysis revealed that the FD method conserved the aroma to a greater extent and its overall acceptability was higher.Öğe Comparison of a Low-cost Prototype Optical Sensor with Three Commercial Systems in Predicting Water and Nutrient Contents of Turfgrass Prediction performance of low-cost optical sensor(Taylor & Francis Inc, 2021) Sekerli, Yunus Emre; Keskin, Muharrem; Soysal, YurtseverChemical soil and plant analyses are time-consuming, expensive, and labor-intensive. There are some optical systems used for this purpose; however, they are expensive and require expertise for their operation. The aim of this study was to develop a low-cost prototype optical sensor and compare it with three commercial systems (GreenSeeker NDVI (Normalized Difference Vegetation Index) meter, chromameter, Fourier transform-near infrared reflectance spectroscopy (FT-NIRS)) to determine water and nutrient concentrations including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) of turfgrass (Lolium perenne L.). Study was conducted on an experimental field to which four different levels of nitrogen fertilizer were applied. Prediction models were developed using PLSR (Partial Least Square Regression) and their performances were evaluated using the criteria of SEP (Standard Error of Prediction) and R-2. With the prototype optical sensor, NDVI gave the best result among 10 different vegetation indices for the prediction of water (SEP = 1.43%) and N (SEP = 0.28%). The best results (lowest SEP) were obtained with the FT-NIRS. However, there are some disadvantages of this system along with the other two instruments (chromameter and NDVI meter) of being expensive and requiring expertise in their operation. Low-cost and easy-to-use prototype optical sensor gave similar results with the NDVI meter and chromameter to predict water and nutrient concentrations except K, Cu, and Zn. An optical sensor similar to the prototype sensor could be developed commercially with low cost and used to estimate the water and nutrient concentration of turfgrass.Öğe Efficiency of GNSS-based Tractor Auto Steering for the Uniformity of Pass-to-Pass Plant Inter-Row Spacing(Univ Namik Kemal, 2024) Topcueri, Mustafa; Keskin, Muharrem; Sekerli, Yunus EmrePrecision agriculture (PA) includes advanced technologies to increase efficiency and profitability of agricultural operations from tillage to harvest and offers sustainability of the natural resources and the environment. Automatic steering (AS) is the mostly-used PA technology in the world and in Turkiye providing many benefits. It has potential for efficient and sustainable agronomic practices including soil ridge tillage and sowing. Adequate spacing is needed to provide equal living area for each plant in sowing. Thus, in mechanized planting, pass-to-pass plant inter-row spacing (PIRS) should be equal in parallel passes. Research on the benefits of the AS for providing uniform PIRS in sowing is very limited. This work aimed to appraise the pass-to-pass PIRS deviations in planting with GNSS-based AS with three signal correction sources (RTK, CORS, SBAS) and without AS (manual steering) for comparison. The data were obtained from 24 farmer fields (cotton and corn) with PIRS set values of 70-75 cm located in the Cukurova region of Turkiye. Pass-to-pass PIRS values were manually measured and the deviations from the set value were analyzed in terms of root mean square error (RMSE). The mean PIRS variations in sowing by manual steering (7.4 cm) were found as significantly higher than the AS based soil ridge tillage and / or sowing (CORS: 5.0 cm, SBAS: 5.9 cm, RTK: 6.7 cm) (p<0.05). In sum, it was found that the AS technology offers benefits in lowering the pass-to pass PIRS variations but the level of benefit changes from farmer to farmer; hence, the AS should be used cautiously with proper settings for greater benefits.Öğe Feasibility of a chromameter and chemometric techniques to discriminate pure and mixed organic and conventional red pepper powders: A pilot study(Wiley, 2022) Keskin, Muharrem; Arslan, Aysel; Soysal, Yurtsever; Sekerli, Yunus Emre; Celiktas, NafizFood adulteration is a major problem causing significant economic and health risks for consumers. Non-destructive, quick, and inexpensive methods are needed for food authentication. No study has been found on the adulteration of organic pepper powders. This study examined the feasibility of a chromameter to discriminate pure and adulterated (mixed) organic red pepper powders obtained from intermittent microwave drying for the first time. PCA, SIMCA, and PLSR were used for the data analysis. The PCA exhibited a very good distinction based on product type (organic and conventional) and drying powers (150, 300, and 450 W), while the SIMCA effectively classified the samples as organic or conventional with a correct classification ratio of 94%. Also, the adulteration rate (%) of the organic pepper powders was predicted using PLSR with promising results (R-2 = 0.90). To summarize, the chromameter has a good potential to classify the red pepper powders as organic or conventional. Novelty Impact Statement Food adulteration has become a major problem on a global scale but no study has been conducted on the adulteration of organic pepper powders to the best knowledge of the authors. This work investigated the feasibility of a chromameter and chemometric techniques for the discrimination of organic red pepper powders from the ones adulterated with the same type of conventional pepper powders. The results revealed that a chromameter has a promising potential to classify the red pepper powders as organic or conventional.Öğe Impact of production and drying methods on the volatile and phenolic characteristics of fresh and powdered sweet red peppers(Elsevier Sci Ltd, 2021) Guclu, Gamze; Keser, Duygu; Kelebek, Hasim; Keskin, Muharrem; Sekerli, Yunus Emre; Soysal, Yurtsever; Selli, SerkanAroma, phenolic compounds and sensory properties of fresh and powdered organic and conventional sweet red peppers dried by three methods (hot air, intermittent microwave and infrared) were studied. The number of aroma compounds was higher in both fresh and powdered organic pepper samples; however, the total amount was higher in conventional samples. In both organic and conventional samples, alcohols were the dominant aroma group. (E)-beta-ionone and beta-ocimene, which are important compounds in peppers, were determined only in organic peppers. Among the drying methods, intermittent microwave drying was more effective in creating new aroma compounds. The liquid chromatography, coupled with tandem mass spectrometry (LC-MS/MS) revealed that luteolin derivative compounds comprised an average of 70% of the phenolics. Higher amount of phenolic were determined in organic samples. Infrared drying was more effective in retaining of phenolics than the other two methods. Sensory analysis revealed that hot air-dried samples were least preferred.Öğe Influence of Leaf Water Content on the Prediction of Nutrient Stress in Strawberry Leaves using Chromameter(Friends Science Publ, 2018) Keskin, Muharrem; Sekerli, Yunus Emre; Gunduz, KazimChemical soil and plant tissue analyses require considerable amount of labor, time, and cost. Non-destructive prediction of nutrient stress from chromameters may save time and labor. Previous studies did not assess multiple nutrient stresses together with the effect of leaf water content (WC). The aim of this work was to investigate the effect of leaf WC on the prediction of leaf nutrient stress from leaf color. A commercial strawberry field with a significant amount of leaf color variability was selected in Hatay province of Turkey. Forty eight leaf samples with varying colors were collected. A hand-held chromameter was used for leaf color measurements in two color systems as L*a*b* and L*C*h degrees. Leaf WC was determined using oven drying method. Leaf nutrient contents of N, P, K, Ca, Mg, Mn, Fe, and Cu were obtained using chemical analysis. Correlation and Partial Least Square Regression (PLSR) methods were utilized for data analysis. Leaf WC ranged from 58.3 to 65.7%. High correlation existed between color parameters and N, Ca, and WC (|r|>0.66). Also, correlation was high between leaf WC and leaf N content (r=0.75), suggesting that the leaves with high WC had also high N content. Using color data, it was possible to predict leaf N content (R-2=0.66), Ca content (R-2=0.70), and WC (R-2=0.65). Using WC as a variable together with the color parameters slightly improved the model performance to predict strawberry leaf nutrient concentrations. (C) 2018 Friends Science PublishersÖğe A low-cost prototype optical sensor to evaluate water, macro and micro elements of turfgrass clippings(Elsevier Science Sa, 2021) Sekerli, Yunus Emre; Keskin, Muharrem; Soysal, YurtseverA low-cost prototype optical sensor system was developed to determine water and nutrient concentrations of turfgrass clippings. The indoor sensor included three photodiodes and interference filters (550, 650, and 800 nm). Clipping samples of turfgrass (Lolium perenne L.) were obtained from 12 plots having four different levels of nitrogen (N). Ten different vegetation indices (VIs) were calculated and evaluated. Prediction models were developed by using PLS (Partial Least Square) regression. Normalized Difference Vegetation Index (NDVI) gave the best result for the prediction of water and N concentrations (R-2 = 0.73; SEP = 1.43 % for water, R-2 = 0.68; SEP = 0.28 % for N). Also, NDVI performed well (R-2 > 0.60) with reasonable SEP values for P (SEP = 0.04 %) and K contents (SEP = 0.23 %). GRVI and DVI (G-R) yielded the best result for Ca (R-2 = 0.66; SEP = 0.03 %) and Mg contents (R-2 = 0.47; SEP = 0.01 %). Yet, the prototype sensor did not provide good results for Fe, Cu, Mn and Zn (R-2 < 0.40). The performance of the prototype sensor was also evaluated based on classifying the sample into three groups (low, medium and high). The highest classification success ratio (SR = 80.4 %) was obtained for K while its success for the other nutrients (N, P, Ca, Mg) and water content was lower (50-70 %). A simple and low-cost optical sensor developed in this study offers promising results as it is capable of giving prior knowledge about a number of macro and micro nutrients and water content of turfgrass clippings. (C) 2021 Elsevier B.V. All rights reserved.Öğe Performance of two low-cost GPS receivers for ground speed measurement under varying speed conditions(Springer, 2017) Keskin, Muharrem; Sekerli, Yunus Emre; Kahraman, SuleymanA global positioning system (GPS) receiver is an important sensor used in modern farming, particularly in precision agriculture to determine geographic location and ground speed. The aim of this study was to investigate the effectiveness of two low-cost GPS receivers for measuring ground speed under varying speed conditions on four different dates. A rotary shaft encoder on an auxiliary wheel mounted on an agricultural tractor was used as a reference. A significant time lag between the rotary encoder speed and the GPS speed was found over a range of speeds. It was observed that the GPS speed lagged the encoder speed in both increasing and decreasing speeds. The average time lag was found to be between 3.6 and 5.2 s for Receiver 1 while Receiver 2 had a time lag from 1.7 to 2.5 s. A significant difference was found between the two receivers for increasing and decreasing speeds in terms of time lags (P < 0.05). A post correction by shifting the GPS speed increased the accuracy of the speed measurement capability of both receivers resulting in an average correlation coefficient of 0.30-0.90 for Receiver 1 and 0.65-0.98 for Receiver 2. Effect of USB-to-COM converter was also studied and it did not have a significant effect on time delay. The GPS receivers provided reliable data during constant speed operating conditions; however, caution should be exercised in varying speed conditions when using low-cost GPS receivers. Also, the companies that produce GPS-based speed sensors should supply technical specifications related to velocity estimates during acceleration and deceleration.Öğe Rapid and cost-effective assessment of nutrients in pistachio (Pistacia vera L.) leaves through Fourier transform near-infrared spectroscopy (FT-NIRS)(Wiley-V C H Verlag Gmbh, 2024) Sekerli, Yunus Emre; Buyuk, Gokhan; Keskin, Muharrem; Celiktas, NafizBackground: Pistachio nuts provide many health benefits in human diet. Nutrient levels in plant leaves and fertilizer schedules are determined based on traditional soil and leaf chemical analyses. However, these methods require additional labor, time, and cost, which is why most farmers do not prefer them and cannot detect nutrient deficiencies in time. Fast, easy-to-use and low-cost nutrient level assessment techniques are needed. AimThis study aims to explore the viability of near-infrared reflectance spectroscopy (NIRS) as a fast, user friendly, and cost effective technique for evluating the major macro- and micronutrient contents of dried and ground pistachio leaf sample. Methods: The feasibility of NIRS for estimating nutrient contents was investigated by analyzing samples from 200 pistachio trees. Dried and ground pistachio leaves were subjected to NIRS analysis. PLSR (Partial least square regression) analyses were performed to develop nutrient content prediction models using spectral information of samples. Results: It was found that the NIRS system had a very good potential to estimate the K, Ca, Cu, and Mg contents of the leaf samples (R-2 > 0.80). It was also found that Fe and Mn concentrations could also be estimated with good accuracy (R-2 = 0.70-0.80). However, the NIRS system did not give good results for the prediction of N, P, and Zn (R-2 < 0.40). Conclusion: In conclusion, the NIRS system can be used to quickly, easily, and economically assess the K, Ca, Cu, Mg, Fe, and Mn contents of dried and ground pistachio leaves. This technique has the potential to improve nutrient management practices in pistachio farming within a sustainable and environmentally conscious framework. Fourier transform NIRS (FT-NIRS) can provide valuable insights by complementing rather than replacing traditional chemical analysis. Laboratory analysis is still required for definitive nutrient content information, but FT-NIRS can significantly reduce the reliance on such analysis, thereby mitigating the environmental impact caused by the excessive use of chemical fertilizers and minimizing the health risks to laboratory staff. In addition, the rapid information-gathering capabilities of the FT-NIRS can be emphasized.Öğe Testing of three sensor systems to predict water and nutrient contents of soccer field turfgrass clippings(Elsevier Gmbh, 2021) Sekerli, Yunus Emre; Keskin, Muharrem; Soysal, YurtseverNatural turfgrass sport fields have some advantages as compared to the synthetic sport fields. They are cheaper; can be repaired cost-effectively and provide water filtration, soil stabilization, temperature regulation, CO2 absorption and O-2 release to atmosphere. Yet, the maintenance procedures especially fertilization should be carried out carefully to prevent pollution of natural resources due to excessive use of chemical fertilizers. The standard method for determining the fertilizer requirement is chemical leaf and soil analysis but it is lengthy process also it requires high amount of labor and costs. Hence, a low-cost and practical technique is needed to determine the nutrient contents of turfgrass. The aim of this work was to test the performance of a low-cost prototype reflectance-based indoor sensor system to assess water and nutrient contents (N, P, K, Ca, Mg, Fe, Cu, Mn, and Zn) of turfgrass clippings (Lolium perenne L.) and to compare it with two optical instruments (hand-held color meter and near infrared spectroscopy system, FT-NIRS). Turfgrass clippings samples (n = 30) were obtained from a soccer field. FT-NIRS system gave the best prediction performance for water and nutrient contents except for Cu. The prototype sensor gave similar results with the color meter for water content and other studied nutrients except Fe, Mn, and Zn. With the prototype sensor, NDVI gave the best result for the prediction of water (SEP = 0.96 %; R-2 = 0.75) and N concentration (SEP = 0.28 %; R-2 = 0.50). FT-NIRS system gave better prediction performance but it is expensive and its operation requires knowledge and experience and tiresome sample preparation as drying and grinding (extra time, energy, labor, and cost). Results depicted that an optical sensor similar to the prototype sensor could be commercially developed with low cost and ease of use and be utilized to estimate the nutrient concentration of turfgrass clipping samples with moderate performance.
