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Construction of an oxygen detection-based optic laccase biosensor for polyphenolic compound detection
摘要： A fiber optic biosensor was constructed from Pleurotus ostreatus laccase for the detection of polyphenolic compounds. Laccase was immobilized on the surface of the commercially available fiber optic oxygen sensor spots by using 3-aminopropylsilanetriol, tetramethyl orthosilicate (TMOS), glutaraldehyde, and amino-modified carboxycellulose. A diffusion layer containing trimethoxymethylsilane (Tri-MOS), and polyvinyl alcohol (PVA) was added to the immobilized laccase layer. The consumption of oxygen as a result of laccase activity was monitored using a fiber optical measuring setup with catechol as a model substrate. The optimal enzyme amount was determined as 1.5 mg per 50 μL of enzyme layer mixture, and with one diffusion layer and at pH 6.9, optimum detection conditions were attained. The biosensors have high reproducibility, stability (at least 85 days if stored in PBS at 4 °C), and convenient measurement duration (ca. 25 min between two successive measurements). The biosensor was found to have a broad linear working range for catechol (40–600 μM) and to be applicable to a flow-through system. In summary, an easy-to-produce, reproducible, and stable laccase sensor with a broad linear working range was produced. The sensor has potential in the food industry as well as in environmental monitoring for the detection of phenolic compounds.
关键词： catechol,phenolic compounds,oxygen-based optic sensor,Laccase biosensor
更新于2025-09-23 15:23:52
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Development of predictive models for quality and maturation stage attributes of wine grapes using vis-nir reflectance spectroscopy
摘要： The viticulture business has an increasing demand for high quality products directly impacting on their market acceptance. Hence, the constant monitoring activities of vineyards, specially quality and maturation stage attributes, are important to assure the production of special wines, justified by their high value-added characteristic. Therefore, optical technologies appear as promising techniques for non-destructive analysis of wine grapes in view of reducing agricultural inputs and analysis duration. The main objective of the present work was to develop predictive models for quality and maturation stage attributes of wine grapes using visible/near infrared (VIS-NIR) reflectance spectroscopy. A total of 432 ‘Syrah’ and 576 ‘Cabernet Sauvignon’ berries were collected and their reflectance spectra were acquired using FieldSpec 3 spectroradiometer for a spectral range from 450 to 1800 nm. In a posterior step, total soluble solids, total anthocyanins and yellow flavonoids were determined as the reference standards. Before elaborating mathematical models, the spectral data were submitted to several pretreatments, such as smoothing, derivate and corrections. Principal Component Regression (PCR) and Partial Least Squares Regression (PLSR) were utilized as predictive models using both the complete spectrum data (450–1800 nm) and a smaller set of spectral samples selected by the Jack-Knife method. Other predictive models were also developed utilizing Multiple Linear Regression (MLR) with spectral signatures from quality attributes. Maturation stages were discriminated using Principal Component Analysis – Linear Discriminant Analysis (PCA-LDA), Principal Component Analysis – Quadratic Discriminant Analysis (PCA-QDA), Principal Component Analysis – Linear Discriminant Analysis using Mahalanobis distance (PCA-LDA Mahalanobis), and Partial Least Squares Discriminant Analysis (PLS-DA) classification techniques. The construction of the PCR, PLSR and MLR regression models has provided robust predictions for total soluble solids and anthocyanins contents (R2 ≥ 0.90), as well as flavonoids contents with a certain degree of precision (R2 ≥ 0.70). Moreover, it was possible to differentiate distinct maturation stages of vines with 93.15% of accuracy using PLS-DA. Therefore, VIS-NIR reflectance spectroscopy is a powerful tool for non-destructive evaluation of quality and maturation stage attributes of intact grapes from ‘Syrah’ and ‘Cabernet Sauvignon’ grapes.
关键词： Total soluble solids,S?o Francisco Valley,Phenolic compounds,Viticulture,Non-destructive methods,Chemometrics
更新于2025-09-19 17:15:36
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Laser-induced fluorescence spectroscopy for early disease detection in grapefruit plants
摘要： Both biotic and abiotic stress causes considerable decrease in chlorophyll content in plant leaves which provide the means of early disease diagnosis. The emergence of disease affects the fluorescence of phenolic compounds and chlorophyll which have been appeared at 530, 686 and 735 nm. It has been found that the intensity of emission band of phenolic compounds at 530 nm increases and that of chlorophyll at 735 nm decreases with the onset of disease. Statistical analysis through principal component analysis (PCA) and partial least square regression (PLSR) has been performed which demonstrated the classification of apparently healthy leaf sites with diseased ones which provide the basis for the detection of disease at early stages. PLSR model was validated through the coefficient of determination (R2), standard error of prediction (SEP) and standard error of calibration (SEC) with the values 0.99, 0.394 and 0.401 which authenticated the model. The prediction accuracy of the model was evaluated through root mean square error in prediction (RMSEP) of 0.14 by predicting 22 unknown emission spectra of different leaf sites. Both PCA and PLSR models produced similar results and proved fluorescence spectroscopy as an excellent tool for early disease detection in plants.
关键词： Early disease diagnosis,Principal component analysis (PCA),Chlorophyll fluorescence,Partial least square regression (PLSR),Phenolic compounds
更新于2025-09-19 17:13:59
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Antioxidant capacity of Camellia japonica cultivars assessed by near- and mid-infrared spectroscopy
摘要： Main conclusion Camellia japonica antioxidant capacity highly differs among its cultivars and could be successfully predicted by near- and mid-infrared spectroscopy. Camellia japonica is a Theaceae family species which are mainly used as an ornamental plant due to its colourful flowers presenting over than 32,000 recognized cultivars. However, this species have been somehow neglected due to the popular tea source, Camellia sinensis. In this study, the antioxidant profile (total phenolic and flavonoid content and total antioxidant capacity—TPC, TFC and TAC) of 31 C. japonica cultivars leaves was determined and further assessed by near- and mid-infrared spectroscopy. The leaves’ antioxidant profile was revealed to be highly dependent on the cultivars analysed being in some cases distinct even for different trees of the same cultivar. Near- and mid-infrared spectroscopy proved to be suitable techniques to predict the total phenolic and flavonoid content as well as the total antioxidant capacity. The best results were obtained with near-infrared spectroscopy whose root mean square error of the prediction set samples was of 5.7?mg of gallic acid/g dry leaf; 3.5?mg catechin/g dry leaf and 3.3?mM Trolox/g dry leaf for TPC, TFC and TAC (with coefficients of the determinations equal to or higher than 0.93). Moreover, the range error ratios were higher than 15 meaning that the developed partial least-squares models are very good for calibration and quantification determinations according to the guidelines for near-infrared models development and maintenance. In this work, the antioxidant profile of several C. japonica cultivars leaves was determined for the first time, being that a rapid and low cost spectroscopic-based method was also proposed for its determination.
关键词： Antioxidants,Camellia japonica cultivars,Chemometrics,Phenolic compounds,Flavonoids,Infrared spectroscopy
更新于2025-09-10 09:29:36
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The potential use of the UV-A and UV-B to improve tomato quality and preference for consumers
摘要： Solanum lycopersicum L. is among the healthiest fruits/vegetables due to its richness in bioactive compounds. However, its fruits from off-season (usually obtained in greenhouses that block UV-rays) have lower reputation than the ones of in-season/field productions. We hypothesise that moderate UV-A/UV-B irradiation during fruit development is able to improve its bioactive compounds and sensorial attributes, increasing its healthy properties. We supplemented for 30 days ‘MicroTom’ fruiting plants with two daily doses of UV-A (1 or 4 h) and UV-B (2 or 5 min). Irradiated plants showed higher ripening synchronization and produced more and smaller fruits. UV-A irradiation stimulated the fruit’s antioxidant capacity, and the antiradical activity by the accumulation of phenolic compounds including the flavonoids. Only the UV-A1 h condition promoted the accumulation of ortho-diphenols in tomato fruits. Regarding the consumers’ preference for aroma/taste, a consumers’ panel test ranked the tomatoes as UV-A 1 h, UVA 4 h, Control, UV-B 5 min and UV-B 2 min. We conclude that the supplementation of UV-A during pre-harvest is particularly effective in increasing ripening synchronization and fruit’s nutritional properties, potentially making these fruits more appealing to consumers.
关键词： Nutritional value,Antioxidants,Pre-harvest-irradiation,Metabolism modulation,Phenolic compounds,Ultraviolet supplementation
更新于2025-09-10 09:29:36