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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 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 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 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, MuharremThe 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.Öğe Comparing hot air drying kinetics and color quality of organic and conventional sweet red peppers(Mustafa Kemal Üniversitesi, 2020) Arslan, Aysel; Soysal, Yurtsever; Keskin, MuharremAims: 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: 39.6210-10 – 58.5810-10 m2 s -1 ; CSRP: 38.9210-10 – 57.5910-10 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.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 Drying Characteristics and Quality Parameters of Microwave-Dried Grated Carrots(Springer, 2012) Arikan, Mehmet Fatih; Ayhan, Zehra; Soysal, Yurtsever; Esturk, OkanThe effectiveness of various microwave-convective drying treatments was compared with convective drying to determine the most favourable treatments in terms of drying kinetics, specific energy consumption and dried product quality of grated carrots. The quality of the dried products differed among drying treatments depending on the microwave power level, pulse ratio and drying temperature. The intermittent microwave-convective drying at ambient temperature with a pulse ratio of 3.0 at 2.23 W g(-1) provided considerable savings in drying time and specific energy consumption when compared to convective drying and produced high-quality product with better physical (colour and texture) and sensory attributes for carrots. The intermittent microwave-convective drying conducted at lower drying temperature with relatively long power-off time resulted in a more stable and gentle drying process and could be preferred to produce high-quality products.Öğe Drying of sage (Salvia officinalis L.) inflorescences by intermittent and continuous microwave-convective air combination(Gaurav Soc Agricultural Research Information Centre-Aric, 2011) Esturk, Okan; Arslan, Mehmet; Soysal, Yurtsever; Uremis, Ilhan; Ayhan, ZehraThe effect of microwave-convective air (M-CA) drying (continuous and intermittent) and convective air (CA) drying of sage (Salvia officinalis L.) inflorescences on drying kinetics and essential oil content was studied. For M-CA drying, four pulse ratio levels (PR1, PR2, PR3 and PR4) at 25 degrees C drying air temperature were used. The average drying rates were 0.211, 0.105, 0.067 and 0.053 kg H2O/kg DM/min for PR1, PR2, PR3 and PR4, respectively. The experimental data were fitted to nine different moisture ratio (MR) models to describe the drying kinetics under various drying conditions. Page model was found satisfactory to describe the drying curves of sage inflorescences. The total quantity of essential oils of sage inflorescences decreased considerably during M-CA drying, whereas the loss of essential oils was limited during CA drying. Compared to shade drying, two essential oil components, sabinene and p-cymene, were lost during CA drying. On the other hand, in addition to these two, alpha-pinene, campene, beta-pinene, limonene, gamma-terpinene, camphor, bornyl acetate, alpha-copaene, gamma-cadinene, delta-cadinene and caryophyllene oxide were disappeared during M-CA drying. M-CA drying may not be proper technique for drying of sage inflorescences when essential oil content is important.Öğe Drying properties and quality parameters of dill dried with intermittent and continuous microwave-convective air treatments(2010) Eştürk, Okan; Soysal, YurtseverIn this study, influence of various microwave-convective air drying applications on drying kinetics, color and sensory quality of dill leaves (Anethum graveolens L.) were investigated. In general, increasing the drying air temperature decreased the drying time, and increased the drying rate. Increasing microwave pulse ratio increased the drying time. Page, Logarithmic, Midilli et al, Wang & Singh and Logistic models were fitted to drying data and the Page model was found to satisfactorily describe the microwave-convective air drying curves of dill leaves. Comparing to the fresh dill, lightness (L*), greenness (-a*) and yellowness (+b*) decreased for all drying applications. The deviation from fresh product color (∆E*) increased as pulse ratio increased and drying air temperature decreased. Considering the product quality, continuous microwave-convective air drying combinations gave better results than intermittent microwave-convective air drying in terms of color and sensory evaluation results.Öğe Drying Properties and Quality Parameters of Dill Dried with Intermittent and Continuous Microwave-convective Air Treatments(Ankara Univ, Fac Agr, 2010) Esturk, Okan; Soysal, YurtseverIn this study, influence of various microwave-convective air drying applications on drying kinetics, color and sensory quality of dill leaves (Anethum graveolens L.) were investigated. In general, increasing the drying air temperature decreased the drying time, and increased the drying rate. Increasing microwave pulse ratio increased the drying time. Page, Logarithmic, Midilli et al, Wang & Singh and Logistic models were fitted to drying data and the Page model was found to satisfactorily describe the microwave-convective air drying curves of dill leaves. Comparing to the fresh dill, lightness (L*), greenness (-a*) and yellowness (+b*) decreased for all drying applications. The deviation from fresh product color (Delta E*) increased as pulse ratio increased and drying air temperature decreased. Considering the product quality, continuous microwave-convective air drying combinations gave better results than intermittent microwave-convective air drying in terms of color and sensory evaluation results.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 Infrared Drying Kinetics and Color Qualities of Organic and Conventional Sweet Red Peppers(Univ Namik Kemal, 2021) Arslan, Aysel; Soysal, Yurtsever; Keskin, MuharremThis study compares the infrared drying kinetics, effective moisture diffusivity, activation energy and color qualities of organically and conventionally produced sweet red peppers (Capsicum annum L.) dried at three different temperatures (60, 70 and 80 degrees C). Results showed that the entire drying process for both organic and conventional sweet red peppers took place mainly in falling rate period. Increasing the drying temperature decreased the drying time considerably. No significant difference was found between the drying times of organic and conventional red peppers. The Midilli model yielded the best fit for all data points for organic and conventional peppers. The drying coefficient of the Midilli model increased with the increase in the drying temperature. The effective moisture diffusivity and activation energy values of organic pepper samples were found slightly higher than those of the conventional samples. This result was found to be compatible with the drying coefficient of Midilli model and characteristic drying rate curves. Higher drying temperatures resulted in brighter red pepper powder color which is more preferable by consumers. Infrared drying at 60 degrees C for organic pepper samples produced the best pepper powders in terms of color quality. Moreover, infrared drying at 60 degrees C and 70 degrees C was also judged as the acceptable drying applications in terms of color quality since they gave the nearest redness to yellowness ratios and higher brightness values as compared to the color of fresh peppers. Overall, infrared drying at 70 degrees C instead of 60 degrees C resulted in about 22% savings in drying time and can be used to produce high quality organic or conventional sweet red pepper powder with better color quality.Öğe 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 Mathematical Modeling, Moisture Diffusion and Color Quality in Intermittent Microwave Drying of Organic and Conventional Sweet Red Peppers(Mdpi, 2020) Arslan, Aysel; Soysal, Yurtsever; Keskin, MuharremThe aims of this research were to evaluate the influence of intermittent microwave drying on the moisture diffusion and color qualities of organically and conventionally grown sweet red peppers and mathematically express drying kinetic data. Pepper samples of 150 g were dried at 150, 300 and 450 W using a microwave oven. Results showed that intermittent microwave drying at 450 W occurred mainly in the falling rate period, whereas drying at lower powers resulted in relatively longer constant rate periods for both peppers types. The Midilli model provided the best fit for all data. The moisture diffusivity (D-eff) values of organic and conventional samples ranged from 59.69 x 10(-10) to 182.01 x 10(-10) m(2)s(-1) and from 59.11 x 10(-10) to 181.01 x 10(-10) m(2)s(-1), respectively, and the difference was insignificant. The pre-exponential factor for the Arrhenius equation (D-0) and activation energy (E-a) values were almost identical for both product types. Overall, organic or conventional growing did not alter the structural features related to the heat transfer properties. Intermittent microwave drying at 150 and 300 W for organic peppers and 150 W for conventional peppers gave the highest Delta L*, Delta a* and a*/b* values, producing the most bright and red pepper powders. Thus, these treatments can be used to produce higher color quality powders.Öğe Rapid and non-destructive detection of organic carrot powder adulteration using spectroscopic techniques(Academic Press Inc Elsevier Science, 2023) Arslan, Aysel; Keskin, Muharrem; Soysal, YurtseverAdditives used for food adulteration are difficult to detect because they have properties similar to the samples they are added to. Organic foods have more positive effects on food safety compared to their conventional counterparts. Therefore, it is important to assess the detectability of additives that resemble the main ingredient and are used for adulteration purposes in organic powdered products. In this study, the feasibility of using a chromameter and near infrared spectroscopy (NIRS) to discriminate adulterated organic black carrot powders, which were dried by hot air (HA) and intermittent microwave (IMW), was investigated. Principal component analysis (PCA) and partial least squares regression (PLSR) were used for data analysis. The best PLSR models for estimating the adulteration level (%) were obtained using NIRS data (R2val=0.98, RMSEP=4.9%) for samples dried by HA. Furthermore, results showed that temperature or power levels applied during drying affected the efficiency of adulteration determination in samples.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.Öğe Utilization of color parameters to estimate moisture content and nutrient levels of peanut leaves(2013) Keskin, Muharrem; Karanlık, Sema; Görücü Keskin, Serap; Soysal, YurtseverLeaf nutrient levels are traditionally quantified by laboratory chemical analysis, which is time-consuming and requires intensive labor and investment. The objective of this study was to predict the moisture content (MC) and nutrient content of peanut leaves from color parameters (CIE Lab) using a chromameter. This method is faster and requires less labor and investment compared to laboratory chemical analysis. Fifty peanut leaf samples were collected from a commercial peanut field. The samples were analyzed for MC, N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu concentrations after color parameters were acquired by chromameter. A positive and high correlation was found between MC and brightness (L*; r = 0.91) and MC and yellowness (b*; r = 0.95). The results show the possibility of predicting the MC of peanut leaves from color data (R2 = 0.88). A strong relationship was also observed between the measured and predicted levels of P and K based on the PLS2 regression model (R2 = 0.88 and R2 = 0.90, respectively). P and K concentrations of peanut leaves can be predicted from the color parameters to within approximately ±0.03% and ±0.15%, respectively. In contrast to MC, P, and K, concentrations of N, Mg, Mn, Zn, and Cu had only moderate correlation, and Fe concentration had the lowest correlation with color parameters (|r| ≤ 0.27).
