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Vitamin C Determination by Ultraviolet Spectroscopy and Multiproduct Calibration
摘要： In this work the vitamin C was determined in industrialized nectar juices through ultraviolet (UV) spectroscopy and multiproduct multivariate calibration, based on partial least squares (PLS) regression. Since samples with different flavors, sugar content (light or not) were together in the model construction, it can be considered as a multiproduct and, due to the heterogeneity of the samples, it was necessary to optimize the calibration and validation sets by outliers elimination. The model was developed and validated by the evaluation of the figures of merit such as: accuracy, sensitivity, analytical sensitivity, adjust, linearity, relative prediction deviation, limits of detection and quantification, indicating that the multiproduct model developed from UV spectroscopy and PLS regression can be used in the industrial routine analysis as an alternative to titration or other time and reagent consuming methods. Here, it was evidenced that the UV-PLS multiproduct model provides advantages as being free of sample preparation steps, is suitable to be updated in order to measure other parameters, does not generates residues and is feasible to be implemented for on-line monitoring. Furthermore, the application of multivariate calibration in multiproduct models is extremely attractive from the industrial point of view.
关键词： multiproduct calibration,vitamin C,PLS,UV spectroscopy
更新于2025-09-23 15:21:21
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Effect of a topical antioxidant serum containing vitamin C, vitamin E, and ferulic acid after Qa??switched 1064a??nm Nd:YAG laser for treatment of environmenta??induced skin pigmentation
摘要： Background: Extrinsic skin aging caused by atmospheric pollutants is associated with a sustained inflammatory response which is a significant risk factor for lentigines and melasma. Aims: The aim of this study was to evaluate the efficacy of topical application of combination formulation of vitamin C, vitamin E, and ferulic acid as an adjuvant to Q-switched Nd:YAG (QSNY) lasers treatment in individuals with lentigines and melasma. Methods: A single blinded, prospective, randomized split-face trial was conducted. Eighteen men and women between 26 and 53 years old were treated with a combination antioxidant serum on one randomized side of their face immediately after QSNY laser and twice daily for 2 weeks. Patients were evaluated using digital photography and spectrometry to assess the melanin index and erythema index. Melasma severity score and global improvement scores also were assessed. Results: The treated side of the face exhibited a significantly greater reduction in the melanin index. There was no significant difference in post-treatment erythema. More clinical improvement was observed on the treated side compared with the untreated side. Conclusions: Our study suggests that topical application of a combination vitamins C, E, and ferulic acid antioxidant formula may be effective as an adjuvant option in QSNY lasers.
关键词： air pollution,lentigo,QS Nd:YAG laser,vitamin C,antioxidant
更新于2025-09-23 15:19:57
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Effects of LED lighting recipes on postharvest quality of leafy vegetables grown in a vertical farm
摘要： Vertical farming is a technology that controls climate, water, nutrients and light to grow food in a closed environment. This allows vegetables to grow pesticide free and without other contaminants. We investigated how to influence the postharvest quality by controlling the preharvest growth conditions while keeping a high production rate. Several standard LED lighting recipes (red/blue or red/white either with or without far red) are in use in commercial farms. For this research we used lettuce, baby leaf spinach, rocket and basil from various cultivars all grown in a vertical farm research facility. We used the standard red white LED light recipe as control, while we changed the spectrum with higher blue and/or higher far-red or apply few days of continuous light stimulation just before the harvest (preharvest). Quality at harvest and quality loss during postharvest storage was monitored. We observed that light quality affects shelf life of baby leaf spinach and rocket by several days. The best light recipe for shelf life had a high blue content (35%) while the worst was with a high far red (25%). In addition, contents of vitamin C, K, nitrate, chlorophyll and flavonols were different under various light quality. Nitrate (in lettuce, rocket and spinach) and vitamin C in rocket were strongly affected by preharvest continuous light, offering a way to reduce the nitrate and improve the antioxidant level. In addition, taste was also found to change as a function of light quality but magnitude of this change is shown to be strongly cultivar dependent.
关键词： LED lighting,nitrate,vitamin K,shelf life,vertical farming,taste,vitamin C
更新于2025-09-16 10:30:52
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Light regulation of vitamin C in tomato fruit is mediated through photosynthesis
摘要： Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300-600 μmol m-2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.
关键词： photosynthesis,respiration,vitamin C,irradiance,ascorbic acid,spectrum
更新于2025-09-04 15:30:14