A Study of Overripe Seed Byproducts from Sun-Dried Grapes by Dispersive Raman Spectroscopy

Overripe seeds from sun-dried grapes submitted to postharvest dehydration constitute a scarcely investigated class of vinification byproduct with limited reports on their phenolic composition and industrial applications. In this study, Raman spectroscopy was applied to characterize a selection of overripe seed byproducts from different white grapes (cv. Moscatel, cv. Pedro Ximénez and cv. Zalema) submitted to postharvest sun drying. The Raman measurements were taken using a 1064 nm excitation laser in order to mitigate the fluorescent effect and the dispersive detection scheme allowed a compactness of the optical system. Spectroscopic data were processed by a principal component analysis to reduce the dimensionality and partner recognition. The evolution of the Raman spectrum during the overripening process was compared with the phenolic composition of grape seeds, which was determined by rapid resolution liquid chromatography/mass spectrometry (RRLC/MS). A multivariate processing of the spectroscopic data allowed the classification of overripe seeds according to the grape variety and the monitoring of stages of the postharvest sun drying process.

Prediction Models for Assessing Lycopene in Open-Field Cultivated Tomatoes by Means of a Portable Reflectance Sensor: Cultivar and Growing-Season Effects

Reflectance spectroscopy represents a useful tool for the nondestructive assessment of tomato lycopene, even in the field. For this reason, a compact, low-cost, light emitting diode-based sensor has been developed to measure reflectance in the 400-750 nm spectral range. It was calibrated against wet chemistry and evaluated by partial least squares (PLS) regression analyses. The lycopene prediction models were defined for two open-field cultivated red-tomato varieties: the processing oblong tomatoes of the cv. Calista (average weight: 76 g) and the fresh-consumption round tomatoes of the cv. Volna (average weight: 130 g), over a period of two consecutive years. The lycopene prediction models were dependent on both cultivar and season. The lycopene root mean square error of prediction produced by the 2014 single-cultivar calibrations validated on the 2015 samples was large (33 mg kg^-1) in the Calista tomatoes and acceptable (9.5 mg kg^-1) in the Volna tomatoes. A more general bicultivar and biyear model could still explain almost 80% of the predicted lycopene variance, with a relative error in red tomatoes of less than 20%. In 2016, the in-field applications of the multiseasonal prediction models, built with the 2014 and 2015 data, showed significant ( P < 0.001) differences in the average lycopene estimated in the crop on two sampling dates that were 20 days apart: on August 19 and September 7, 2016, the lycopene was 98.9 ± 9.3 and 92.2 ± 10.8 mg kg^-1 FW for cv. Calista and 54.6 ± 13.2 and 60.8 ± 6.8 mg kg^-1 FW for cv. Volna. The sensor was also able to monitor the temporal evolution of lycopene accumulation on the very same fruits attached to the plants. These results indicated that a simple, compact reflectance device and PLS analysis could provide adequately precise and robust (through-seasons) models for the nondestructive assessment of lycopene in whole tomatoes. This technique could guarantee tomatoes with the highest nutraceutical value from the production, during storage and distribution, and finally to consumers.

Fibre-optic sensors in health care

Biomedical fibre-optic sensors are attractive for the measurement of physical, chemical and biochemical parameters and for spectral measurements directly performed on the patient. An overview of fibre-optic sensors for in vivo monitoring is given, with particular attention paid to the advantages that these sensors are able to offer in different application fields such as cardiovascular and intensive care, angiology, gastroenterology, ophthalmology, oncology, neurology, dermatology and dentistry.

Circular-array optical-fiber probe for backscattering photon correlation spectroscopy measurements

A miniaturized probe comprising a circular array of optical fibers coupled to a graded-index microlens has been designed for analyzing colloidal solutions by photon correlation spectroscopy (PCS). The system's suitability for PCS measurements was validated by experimental testing performed in bulk solutions and small drops of monodisperse and bimodal test colloidal solutions.

Fiber-optic sensor for simultaneous and independent measurement of vibration and temperature in electric generators

A fiber-optic sensor designed to operate inside high-power electric plants is presented. The probe is based on a fiber-optic proximity sensor that detects the light intensity modulation induced by an elastic transducer. The nonlinear response of the optical head is exploited in an original manner to obtain the simultaneous and ndependent measurement of temperature and vibration at 100 Hz. The particular working principle provides an intrinsically lead-insensitive response.

Fiber optic vibration sensor for remote monitoring in high power electric machines

A novel fiber optic vibration sensor is presented, based on the motion detection of an elastic cantilever by means of the optical triangulation technique. The sensor was designed to work at a fixed frequency of 100 Hz for applications in high power electrical plants where insulation and EM immunity requirements make fiber optic sensing the most suitable choice. The working linear range reaches a peak amplitude of 0.25 mm; resolution is 0.1 microm; accuracy is better than +/-3%; and sensitivity is 10 mV/microm. Design details and experimental results are reported.

Fiber-optic thermometric probe utilizing GRIN lenses

A multimode optical fiber thermometer is described, which makes use of a single fiber for light guiding and a thermochromic solution as a differential absorption temperature transducer. The probe has a novel design and utilizes graded-index microlenses to achieve high coupling efficiency between fiber and transducer. Technical data of the electrooptic unit, along with the working principle of the probe are presented, and calibration tests of the thermometer are given.

Large core diameter fiber-optic branching coupler

A technique based on evanescent wave coupling is used to construct branching couplers utilizing large core PCS fibers. Details of the construction technique are given along with the values of the characteristic parameters measured on two sets of couplers.