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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 Emre
The 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.
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, Mustafa
Overapplication 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.
Changes in the aroma and key odorants from white garlic to black garlic using approaches of molecular sensory science: A review
(Cell Press, 2023) Kilic-Buyukkurt, Ozlem; Kelebek, Hasim; Bordiga, Matteo; Keskin, Muharrem; Selli, Serkan
Black garlic is a relatively new product that has become very popular in recent years. It is obtained by fermenting raw (white) garlic by the application of heat treatment. The undesirable pungent odor of the white garlic disappears and the black garlic product with a sweet-sour flavor is formed after various reactions during the applied heat process. As a result, black garlic is more preferred and easily consumed by the consumers compared to white garlic. This review aims to summarize the studies on the changes in the odorants during the heat treatment employed in the production of black garlic as well as the factors affecting the changes in the aroma and aromaactive compounds and the use of molecular sensory science (MSS) approach, which has been applied in recent years as a new method for the determination of the aroma compounds. This work revealed that the use of the MSS on the aroma changes in black garlic is quite limited in the literature. Thus, more studies are needed to understand the aroma changes that occur during the formation of black garlic from white garlic in more detail.
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, Aysel
Carrot 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.
Çim bitkisinin azot ve su içeriği tahmini için Renk ölçer ve NDVI ölçerin karşılaştırılması
(2020) Keskin, Muharrem; Çam, Çağatay; Şekerli, Yunus Emre
Amaç: Geleneksel olarak çim bitkisinin azot (Aİ) ve suiçeriği (Sİ) tahmini zaman alıcı, yorucu, fazla iş gücügerektiren ve masraflı olan kimyasal laboratuvaranalizleriyle belirlenmektedir. Bu çalışmanın amacı, ikifarklı el tipi optik algılayıcının (GreenSeeker NDVI metreve renk ölçer) çim bitkisinin azot ve su içeriğinideğerlendirmedeki uygunluğunu incelemektir.Yöntem ve Bulgular: Çalışmada 1 m x 1 m'lik altı adet çimparselinde değişken düzeyli azotlu gübre uygulamasıyapılmıştır. NDVI ölçümleri arazide el tipi GreenSeekerNDVI ölçer ile gerçekleştirilmiştir. Biçme işlemindensonra, çim biçkilerinin renk değerleri laboratuvarda renk ölçer kullanılarak ölçülmüştür. Veriler korelasyon vekısmi en küçük kareler regresyon (PLSR) analizikullanılarak değerlendirilmiştir. Yaprak Aİ, Sİ ile NDVI verenk değerleri arasında yüksek korelasyon bulunmuştur.Yaprak Aİ (%)’nin NDVI (R2val=0.73, SEP=% 0.19) ve renkdeğerlerinden (L*a*b*C*h°) (R2val=0.76; SEP=% 0.18)tahmin edilebileceği tepit edilmiştir. Ayrıca, Sİ (%)’ninNDVI (R2val=0.40, SEP=% 5.07) ve renk değerlerinden(L*C*h°) (R2val=0.69; SEP=3.67 %) daha düşük doğrulukile tahmin edilebileceği belirlenmiştir.Genel Yorum: Sonuç olarak; çim yaprağı Aİ’nin, NDVIcihazı veya renk ölçer kullanılarak daha objektif veekonomik bir şekilde makul hassasiyet ile tahminedilebileceği tespit edilmiştir.Çalışmanın Önemi ve Etkisi: Azot ve su içeriği analizsüresindeki azalma dikkate alındığında, çalışmasonuçlarının çim saha bakım sorumluları için faydalıolacağı değerlendirilmiştir. Ayrıca algılayıcılar ileyapılacak azot içeriği tespitinin çim alan bakımsorumluları tarafından kullanılması halinde daha çevredostu bir yöntem olacağı düşünülmektedir.
Comparative Appraisal of Three Low-Cost GPS Speed Sensors with Different Data Update Frequencies
(Mdpi, 2021) Akkamis, Mustafa; Keskin, Muharrem; Sekerli, Yunus Emre
Low-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.
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, Hasim
Drying 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.
Comparative elucidation of colour, volatile and phenolic profiles of black carrot (Daucus carota L.) pomace and powders prepared by five different drying methods
(Elsevier Sci Ltd, 2022) Polat, Suleyman; Guclu, Gamze; Kelebek, Hasim; Keskin, Muharrem; Selli, Serkan
Black carrot pomace is a juice industry by-product that can be easily spoiled due to its high moisture content and usually considered as waste; however, it is a valuable product with high amount of bioactive compounds that can be recovered for further application in several industrial fields. Drying is an effective method for the preservation of this product. Thus, the influence of five drying methods (FD: freeze drying, MWD: microwave drying, CD: convective drying, VCD: vacuum/convective drying, CHD: conductive hydro drying) on colour, phenolics and volatiles of pomace were investigated. Findings revealed that drying process decreased the amount of anthocyanins, colourless phenolics and volatile compounds. CHD resulted in similar colour quality and yielded a better preservation of colour and phenolics while FD provided dried sample with an aroma quality similar to fresh sample. The shorter duration of the CHD makes it a better choice.
Comparative elucidation on the phenolic fingerprint, sugars and antioxidant activity of white, orange and purple-fleshed sweet potatoes (Ipomoea batatas L.) as affected by different cooking methods
(Cell Press, 2023) Guclu, Gamze; Dagli, Mumine Melike; Aksay, Ozge; Keskin, Muharrem; Kelebek, Hasim; Selli, Serkan
In this study, three cooking methods (baking, boiling, sous vide (SV)) were applied to Turkish sweet potatoes with three flesh colors (white, orange, purple) to examine the effects of the product color and cooking methods on the total phenolics, antioxidant activity, sugars, phenolic acids, and anthocyanins. LC-MS-MS was employed in the characterization of these compounds. It was observed that the product color and cooking method significantly affected the concentrations of bioactive compounds like polyphenols. Both the highest total phenolic content (11.36 mg/g) and antioxidant activity (DPPH (50.3 & mu;M TE/g) and ABTS (63.53 & mu;M TE/g)) were determined in the purple sweet potato cooked with the SV method. 10 phenolic acids were quantified in all samples which were in the highest amounts in the orange colored samples followed by the purple samples. Baking resulted in the highest total phenolic acids in all samples. 13 anthocyanins were detected in the purple-colored samples, while the SV cooking best preserved the anthocyanins. In sum, purple sweet potatoes cooked by SV are recommended for higher phenolic contents, antioxidant capacity and anthocyanins.
Comparative Investigation of Drying and Quality Characteristics of Organic and Conventional Black Carrots Dried by Intermittent Microwave and Hot Air
(Univ Namik Kemal, 2023) Arslan, Aysel; Soysal, Yurtsever; Keskin, Muharrem
The quality of agricultural crops is influenced by growing conditions and post-harvest processes, including drying. Moreover, the total phenolic and total antioxidant content in the product's structure and composition can be either positively or negatively affected by the heat treatments applied during drying. Additionally, the specific growing conditions and methods of water removal can lead to the development of distinct drying characteristics. There was no study comparing the drying kinetics and quality parameters of organic (OBC) and conventional (CBC) black carrot in the literature studies. In this study were aimed that mathematically modelling the drying kinetics for OBC and CBC with IMW (150, 300, 450 W) and HA (60, 70, 80 degrees C), determining their differences and evaluating the effects of methods on quality properties. The results showed that L* and Delta E values of the final products increased significantly by increasing the power and temperature levels applied during drying and the powder samples were lighter in color compared to the fresh samples. The total phenolic and total antioxidant capacity values were higher in fresh OBC samples compared to the conventional variety. This result shows that OBC is superior to the CBC in terms of higher total phenolic and total antioxidant content. The activation energy (E-a) values of OBC and CBC dried by IMW and HA were calculated as 8.41x10(-3); 8.40x10(-3) Wg(-1) and 25.50; 19.72 kJ mol(-1), respectively. The Logistic and Verma were the best fit models for describing IMW and HA drying kinetics, respectively. The samples obtained with IMW drying, which resulted in a shorter drying time, were more effect in terms of preserving and increasing the total phenolic and antioxidant content compared to dried samples with HA. The results showed that that the temperature/power levels applied to the products during the drying process, thus the drying times and the methods of removing moisture from the product are effective in the preservation of the total phenolic components.
Comparing a chromameter and a hand held NDVI meter to predict nitrogen and water content of turfgrass
(Hatay Mustafa Kemal Üniversitesi, 2020) Keskin, Muharrem; Çam, Çağatay; Şekerli, Yunus Emre
Aims: Nitrogen content (NC) and water content (WC) of turfgrass is traditionally determined by laboratory analysis which is time-consuming, tiresome, laborious and costly. The aim of this study was to examine the suitability of two hand held optical instruments (GreenSeeker NDVI meter and chromameter) to evaluate NC and WC of turfgrass. Methods and Results: Six turfgrass plots of 1 m x 1 m with a mixture of five different species were used and variable rate nitrogen fertilizer (N0: 0 g N m-2 , N1: 2.5 g N m-2 , N2: 5 g N m-2 ) was applied. NDVI measurements were taken at around noon with a GreenSeeker NDVI instrument from the plots. After mowing, the color values of the clippings were measured using a hand-held chromameter. The data were analyzed using correlation and partial least square regression (PLSR). A high correlation was found between leaf NC, WC, NDVI and color values. The leaf NC (%) can be estimated from the NDVI (R2 val=0.73, SEP=0.19%) and color values (L*a*b*C*h°) (R2 val=0.76; SEP=0.18%). Also, it was found that the WC (%) can be predicted from the NDVI (R2 val=0.40, SEP=5.07%) and color values (L*C*h°) (R2 val=0.69; SEP=3.67%) with slightly lower accuracy. Conclusions: Turfgrass leaf NC can be estimated with either an NDVI instrument (R2=0.73, SEP=0.19%) or a chromameter (R2=0.76, 0.18%) with reasonable accuracy in a more objective and economical way. Significance and Impact of the Study: Considering the reduction in time and cost required in the NC and WC analysis, we think that results of this study may be useful for turf field managers. Also, nitrogen determination with sensors will be a more eco-friendly way if used by managers.
Comparing hot air drying kinetics and color quality of organic and conventional sweet red peppers
(Mustafa Kemal Üniversitesi, 2020) Arslan, Aysel; Soysal, Yurtsever; Keskin, Muharrem
Aims: This study was conducted to compare the hot air drying kinetics and color quality of organically and conventionally produced sweet red peppers. Methods and Results: The pepper samples were dried at 60, 70 and 80°C using a hot air dryer. Drying kinetics, effective moisture diffusivity (Deff), activation energy (Ea) and color quality were studied. The drying process for both organic (OSRP) and conventional sweet red peppers (CSRP) occurred mainly in falling rate period. Increasing the drying temperature reduced the drying time considerably. Except 60°C, significant difference was found between the drying times of OSRP and CSRP samples. The Midilli model gave the best fit for all data points for pepper types. A positive relationship was found between the drying temperature and Deff values (OSRP: 39.6210-10 – 58.5810-10 m2 s -1 ; CSRP: 38.9210-10 – 57.5910-10 m2 s -1 ). Differences between the Deff values of OSRP and CSRP samples were not significant. Conclusions: Characteristic drying curve profiles, Deff and Ea values followed the similar trajectory showing that the growing practice of the peppers did not significantly change the structural features related to heat transfer. The hot-air drying at 70°C and 80°C gave brighter and redder pepper powders; hence, these treatments are suggested as the suitable drying applications to produce high quality OSRP and CSRP powders in terms of color quality. By using 80°C instead of 60°C, about 25% and 32% savings in drying times could be obtainable for CSRP and OSRP samples, respectively. Significance and Impact of the Study: Organic production has an increasing trend in the world; however, research on the evaluation of drying kinetics and color quality of organic products is very limited. Thus, this study aimed at studying appraisal of the drying kinetics and related parameters of CSRP and OSRP samples.
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, Yurtsever
Chemical 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.
Effect of Deficit Irrigation on the Estimation of Cucumber Leaf Area under Greenhouse Conditions
(Friends Science Publ, 2018) Bozkurt, Sefer; Keskin, Muharrem
Simple, accurate, and nondestructive methods of quantifying leaf area are important for many experimental comparisons. The aims of this study were to establish models to estimate the leaf area of cucumber plants grown under greenhouse conditions and evaluate the effects of different irrigation water levels on this estimation. Six irrigation levels based on evaporation from a Class A Pan (I-20:20%, I-40:40%, I-60:60%, I-80:80%, I-100:100% and I-120:120% of) were utilized A total of about 690 leaves from different irrigation levels were collected and relationships among leaf width (W), length (L) and leaf area (LA) were investigated. Estimation models were derived using Multiple Linear Regression (MLR) method and Full Cross Validation was used to validate the models. The Root Mean Square Error of Prediction (RMSEP) and R-2 values were used to compare the models. It was found that mean leaf area values were affected by different irrigation amounts. Mean leaf areas in I-20 and I-40 were significantly lower than the other irrigation treatments. A strong non-linear relationship was found between cucumber W, L and LA (R-2 >= 0.94). Three LA prediction models with W (Model 1), L (Model 2) and W and L (Model 3) were developed for each irrigation levels and for the combined data. RMSEP and R-2 values were 16.3 cm(2) and 0.99 for the model of combined data for all leaves from all different irrigation treatments. In conclusion, for various physiological and morphological studies, model developed in this study can be used as non-destructive technique to estimate cucumber leaf area from leaf size for each irrigation levels and for the combined data in a shorter time with less labor and budget. (C) 2018 Friends Science Publishers
Effectiveness of GNSS-based tractor auto steering systems in crop spraying
(Hatay Mustafa Kemal Üniversitesi, 2019) Topçueri, Mustafa; Keskin, Muharrem
Aims: This study aimed to compare pass-to-pass overlaps and spacings in adjacent parallel passes in spraying with and without tractor automatic steering (AS). Methods and Results: The data were obtained from 13 farmer fields (cotton, corn and peanut) to assess the performance of AS systems in real farmer conditions. Root mean square errors (RMSE) of overlaps and spacings were determined on the maps generated from the coordinates of the tractor recorded while spraying. Variations between the fields were also examined. The RMSE was lowest (7.5 ± 1.7 cm) in the fields on which farmers used AS (with RTK correction signal) in all three operations of tillage, sowing and spraying. RMSE values were comparatively higher for the fields on which farmers used AS only in ridge tillage but not in sowing and spraying (CORS-GSM: 46.1 ± 6.5 cm, SBAS: 76.5 ± 13.9 cm). The fields with manually-steered ridge tillage, sowing and spraying (all three) had the highest RMSE value of 100.8 ± 27.8 cm (p<0.05). The mean RMSE in the manual spraying (without AS) were found to be significantly higher than those using the AS (p<0.05). Conclusions: AS systems were found to be beneficial in reducing the mean pass-to pass overlap and spacing errors (RMSE) in spraying. However, most of the farmers used AS only in soil ridge tillage and made the spraying without AS by referencing marking flags and/ or soil ridges which were formed using AS. Main reason of this is the high cost of the AS systems and farmers cannot afford to equip all of their tractors. The use of AS systems not only in ridge tillage but also in planting and spraying reduced the errors and increased the benefit of AS usage. The level of benefit from the AS could change from farmer to farmer; thus, farmers should use the AS systems carefully with appropriate equipment settings to obtain a higher level of benefits. Significance and Impact of the Study: Appropriate use of AS systems in spraying offers benefits to reduce overlap and gaps and the amount of pesticides resulting in lower amount of environmental pollution and pesticide residues on crops, lower application time, lower fuel and labor consumption.
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 Emre
Precision 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.
Evaluation of a low-cost GPS receiver for precision agriculture use in Adana province of Turkey
(2009) Keskin, Muharrem; Say, Sait Muharrem; Görücü Keskin, Serap
The most vital factor in the application of precision agriculture technology is the cost of the required high-technology equipment. The equipment cost is the major obstacle in adopting the precision agriculture. GPS receiver is one of the most essential tools with high initial costs in this technology. The aim of this study was to evaluate a low-cost GPS receiver in 3 different tests including static, dynamic circular area, and dynamic straight line tests. It was observed that the tested low-cost GPS receiver yielded a deviation of less than 1.50 m, 1.60 m, and 1.48 m in static, circular area, and straight line tests, respectively. It can be concluded that the low-cost GPS receiver without differential correction can be used for variable fertilizer application and soil and yield mapping since it has an appropriate accuracy values for these applications. On the other hand, it would not be suitable for some precision agriculture applications that require an accuracy of less than 1 m such as variable herbicide application and row crop planting. Instead, a GPS receiver with differential correction service should be employed for such applications. In addition, the mean percent error values were -1.3% and -0.5% in all tests in the circle area calculation. These values can be considered to be acceptable for the field area calculation studies.
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, Nafiz
Food 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.
Feasibility of low-cost GPS receivers for ground speed measurement
(Elsevier Sci Ltd, 2006) Keskin, Muharrem; Say, Sait M.
Ground speed measurement is required in many agricultural machinery operations. There are a number of techniques for the determination of the ground speed; however, each of these methods has some disadvantages. It is known that a GPS receiver is capable of calculating travel speed; however, no study has been reported on the performance of low-cost GPS receivers in measuring the ground speed in agricultural machinery operations. The objective of this work was to study the effectiveness of low-cost GPS receivers for measuring ground speed. Computer programs were written to read, store, and process the GPS data from two different low-cost GPS receivers. Differential correction was not used in the study since there was no correction service in the study area. A very strong relationship between the average GPS speeds and the average calculated speeds was found in the study (R-2 > 0.99). Also, the results showed that the GPS receivers followed the speed change quite well. GPS receivers can be used to determine both the position and the speed of the agricultural machinery. In this way, there is no need to use a separate speed sensor leading to simpler and more affordable instrumentation systems. In conclusion, low-cost GPS receivers can be confidently used to measure the ground speed in agricultural machinery operations. (c) 2006 Elsevier B.V. All rights reserved.
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, Serkan
Aroma, 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.

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