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    Determination of pesticide residual levels in strawberry (Fragaria) by near-infrared spectroscopy
    (Wiley, 2020) Yazici, Arzu; Tiryaki, Gulgun Yildiz; Ayvaz, Huseyin
    BACKGROUND In this study, an infrared-based prediction method was developed for easy, fast and non-destructive detection of pesticide residue levels measured by reference analysis in strawberry (Fragaria x ananassa Duch, cv. Albion) samples using near-infrared spectroscopy and demonstrating its potential alternative or complementary use instead of traditional pesticide determination methods. Strawberries of Albion variety, which were supplied directly from greenhouses, were used as the study material. A total of 60 batch sample groups, each consisting of eight strawberries, was formed, and each group was treated with a commercial pesticide at different concentrations (26.7% boscalid + 6.7% pyraclostrobin) and varying residual levels were obtained in strawberry batches. The strawberry samples with pesticide residuals were used both to collect near-infrared spectra and to determine reference pesticide levels, applying QuEChERS (quick, easy, cheap, rugged, safe) extraction, followed by liquid chromatographic-mass spectrometric analysis. RESULTS AND CONCLUSION Partial least squares regression (PLSR) models were developed for boscalid and pyraclostrobin active substances. During model development, the samples were randomly divided into two groups as calibration (n = 48) and validation (n = 12) sets. A calibration model was developed for each active substance, and then the models were validated using cross-validation and external sets. Performance evaluation of the PLSR models was evaluated based on the residual predictive deviation (RPD) of each model. An RPD of 2.28 was obtained for boscalid, while it was 2.31 for pyraclostrobin. These results indicate that the developed models have reasonable predictive power. (c) 2019 Society of Chemical Industry
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    Öğe
    Quantification of soybean oil adulteration in extra virgin olive oil using portable raman spectroscopy
    (Springer, 2017) Tiryaki, Gulgun Yildiz; Ayvaz, Huseyin
    Extra virgin olive oil is produced through either a cold press procedure or a centrifugation with no thermal and chemical treatments and it is considered as the best quality oil under the category of olive oils. The superior properties of olive oil due to its rich in phenolic and antioxidant content and its contribution to prevent several health problems has increased the demand for olive oil over the years. Consequently, it is nowadays sold at remarkably higher price than regular vegetable oils in the market. Unfortunately, extra virgin olive oil (EVOO) has been adulterated with other cheap oils due to potential high commercial profit. Even though, there are methods available to detect the adulteration in EVOO (such as chromatographic methods and PCR),alternative simpler and faster methods are being studied. In this study, performance of portable Raman spectroscopy to quantify soybean oil (SO) adulteration [up to 25 % (w/w)] in EVOO has been evaluated. Partial Least Square Regression (PLSR) calibration models were developed and both internally (using cross-validation, leave-one-out approach) and externally (using an independent sample set) validated. The model gave standard error of prediction (SEP) of 1.34 % (w/w) SO in EVOO and correlation coefficient of prediction (rPred) of 0.99. Additionally, the residual predictive deviation (RPD) value calculated for the model was found to be 5.71, indicating that the model was considered as good and could be used for routine analysis and quality control applications.
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    Öğe
    Revealing Seed Coat Colour Variation and Their Possible Association with Seed Yield Parameters in Common Vetch (Vicia sativa L.)
    (Wiley, 2016) Tiryaki, Gulgun Yildiz; Cil, Abdullah; Tiryaki, Iskender
    The seed coat colour variation of 70 common vetch genotypes were determined by using uniform colour scale (L*a*b*) and their possible correlation with seed yield parameters including the number of pods per plant, the number of seeds per pod, pod dimension, and seed yield (kg/da) was determined. The results revealed presence of highly significant (p < 0.01) variations for both the seed yield and the seed coat colour parameters measured. The number of pods per plant, the number of seeds per pod, and seed yield ranged from 5.8 to 16.03, from 5.2 to 7.66, and from 143.37 to 531.1, respectively. The lightness value varied from 19.00 to 40.28 while chromaticity a* and b* values ranged from -0.16 to 8.99 and from 0.79 to 22.11, respectively. The highest correlation coefficients were determined between b* and L* (r = 0.73), and a* and L* (r = 0.55). The seed coat colour traits and seed yield parameters generally showed weak negative correlations. Seed yellowness (b*) and seed yield had correlation coefficient of -0.25, while correlation between L* and seed yield was determined as -0.23. The results indicated that lightness and yellowness of seed coat may be used as an important parameter to prescreen high yield genotypes of common vetch.