307 research outputs found
Optical properties of developing pip and stone fruit reveal underlying structural changes
Analyzing the optical properties of fruits represents a powerful approach for non-destructive observations of fruit development. With classical spectroscopy in the visible and near-infrared wavelength ranges, the apparent attenuation of light results from its absorption or scattering. In horticultural applications, frequently, the normalized difference vegetation index (NDVI) is employed to reduce the effects of varying scattering properties on the apparent signal. However, this simple approach appears to be limited. In the laboratory, with time-resolved reflectance spectroscopy, the absorption coefficient, μa, and the reduced scattering coefficient, μs′, can be analyzed separately. In this study, these differentiated optical properties were recorded (540-940 nm), probing fruit tissue from the skin up to 2 cm depth in apple (Malus × domestica 'Elstar') and plum (Prunus domestica 'Tophit plus') harvested four times (65-145 days after full bloom). The μa spectra showed typical peak at 670 nm of the chlorophyll absorption. The μs′ at 670 nm in apple changed by 14.7% (18.2-15.5 cm-1), while in plum differences of 41.5% (8.5-5.0 cm-1) were found. The scattering power, the relative change of μs′, was zero in apple, but enhanced in plum over the fruit development period. This mirrors more isotropic and constant structures in apple compared with plum. For horticultural applications, the larger variability in scattering properties of plum explains the discrepancy between commercially assessed NDVI values or similar indices and the absolute μa values in plum (R < 0.05), while the NDVI approach appeared reasonable in apple (R ≥ 0.80)
Clinical trial of time-resolved scanning optical mammography at 4 wavelengths between 683 and 975 nm
The first time-resolved optical mammograph operating beyond 900 nm (683, 785, 913, and 975 nm) is presently being used in a clinical trial to test the diagnostic potential of the technique in detecting and characterizing breast lesions. Between November 2001 and October 2002, 101 patients with malignant and benign lesions were analyzed retrospectively. Scattering plots, as derived from a homogeneous model, and late gated intensity images, to monitor spatial changes in the absorption properties, are routinely used. The intensity images available at four wavelengths provide sensitivity to the main tissue constituents (oxy- and deoxyhemoglobin, water, and lipids), in agreement with expected tissue composition and physiology, while the scattering plots mirror structural changes. Briefly, tumors are usually identified due to the strong blood absorption at short wavelengths, cysts to the low scattering, and fibroadenomas to low absorption at 913 nm and high at 975 nm, even though the optical features of fibroadenomas seem not to be uniquely defined. The effectiveness of the technique in localizing and discriminating different lesion types is analyzed as a function of various parameters (lesion size, compressed breast thickness, and breast parenchymal pattern).
Time-resolved reflectance spectroscopy as a management tool for late-maturing nectarine supply chain
The absorption coefficient of the fruit flesh at 670 nm (mu(a)), measured at harvest by time-resolved reflectance spectroscopy (TRS) is a good maturity index for early nectarine cultivars. A kinetic model has been developed linking the mu(a), expressed as the biological shift factor to softening during ripening. This allows shelf life prediction for individual fruit from the value of mu(a) at harvest and the fruit categorization into predicted softening and usability classes. In this work, the predictive capacity of a kinetic model developed using mu(a) data at harvest and firmness data within 1-2 d after harvest for a late maturing nectarine cultivar ('Morsiani 90') was tested for prediction and classification ability. Compared to early maturing cultivars, mu(a) at harvest had low values and low variability, indicating advanced maturity, whereas firmness was similar. Hence, fruit were categorized into six usability classes (from 'transportable-hard' to 'ready-to-eat-very soft') basing on mu(a) limits established analyzing firmness data in shelf life after harvest. The model was tested by comparing the predicted firmness and class of usability to the actual ones measured during ripening and its performance compared to that of models based on data during the whole shelf life at 20 degrees C after harvest and after storage at 0 degrees C and 4 degrees C. The model showed a classification ability very close to that of models based on data of the whole shelf life, and was able to correctly segregate the 'ready-to-eat-transportable', 'transportable' and 'transportable-hard' classes for ripening at harvest and after storage at 0 degrees C, and the 'ready-to-eat-very soft' and 'ready-to-eat-soft' classes for ripening after storage at 4 degrees C, with lower performance of models for fruit after storage at 4 degrees C respect to those of the other two ripening
Validation of time domain near infrared spectroscopy in muscle measurements: Effect of a superficial layer
Non-destructive analysis of anthocyanins in cherries by means of Lambert-Beer and multivariate regression based on spectroscopy and scatter correction using time-resolved analysis
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Selection Models for the Internal Quality of Fruit, based on Time Domain Laser Reflectance Spectroscopy
Time domain laser reflectance spectroscopy (TRS) was applied for the first time to evaluate internal fruit quality. This technique, known in medicine-related knowledge areas, has not been used before in agricultural or food research. It allows the simultaneous measurement of two optical characteristics of the sample: light scattering inside the tissues and light absorption. Models to estimate non-destructively firmness, soluble solids and acid contents in tomato, apple, peach and nectarine were developed using sequential statistical techniques: principal component analysis, multiple stepwise linear regression, clustering and discriminant analysis. Consistent correlations were established between the two parameters measured with TRS, i.e. absorption and transport scattering coefficients, with chemical constituents (soluble solids and acids) and firmness, respectively. Classification models were created to sort fruits into three quality grades (‘low’, ‘medium’ and ‘high’), according to their firmness, soluble solids and acidity
Detection of internal quality in kiwi with time-domain diffuse reflectance spectroscopy
Time-domain diffuse reflectance spectroscopy (TRS), a medical sensing technique, was used to evaluate internal kiwi fruit quality. The application of this pulsed laser spectroscopic technique was studied as a new, possible non-destructive, method to detect optically different quality parameters: firmness, sugar content, and acidity. The main difference with other spectroscopic techniques is that TRS estimates separately and at the same time absorbed light and scattering inside the sample, at each wavelength, allowing simultaneous estimations of firmness and chemical contents. Standard tests (flesh puncture, compression with ball, .Brix, total acidity, skin color) have been used as references to build estimative models, using a multivariate statistical approach. Classification functions of the fruits into three groups achieved a performance of 75% correctly classified fruits for firmness, 60% for sugar content, and 97% for acidity. Results demonstrate good potential for this technique to be used in the development of new sensors for non-destructive quality assessment
Electronic nose pattern, sensory profile and flavor components of cold stored 'Spring Belle' peaches: Influence of storage temperatures and fruit maturity assessed at harvest by time-resolved reflectance spectroscopy
Effect of a thin superficial layer on the estimate of hemodynamic changes in a two-layer medium by time domain NIRS
In order to study hemodynamic changes involved in muscular
metabolism by means of time domain fNIRS, we need to discriminate in the
measured signal contributions coming from different depths. Muscles are,
in fact, typically located under other tissues, e.g. skin and fat. In this paper,
we study the possibility to exploit a previously proposed method for
analyzing time-resolved fNIRS measurements in a two-layer structure with
a thin superficial layer. This method is based on the calculation of the timedependent
mean partial pathlengths. We validated it by simulating venous
and arterial arm cuff occlusions and then applied it on in vivo
measurements
Noninvasive optical estimation of CSF thickness for brain-atrophy monitoring
Dementia disorders are increasingly becoming sources of a broad range of
problems, strongly interfering with normal daily tasks of a growing number of
individuals. Such neurodegenerative diseases are often accompanied with
progressive brain atrophy that, at late stages, leads to drastically reduced
brain dimensions. At the moment, this structural involution can be followed
with XCT or MRI measurements that share numerous disadvantages in terms of
usability, invasiveness and costs. In this work, we aim to retrieve information
concerning the brain atrophy stage and its evolution, proposing a novel
approach based on non-invasive time-resolved Near Infra-Red (tr-NIR)
measurements. For this purpose, we created a set of human-head atlases, in
which we eroded the brain as it would happen in a clinical brain-atrophy
progression. With these realistic meshes, we reproduced a longitudinal tr-NIR
study exploiting a Monte-Carlo photon propagation algorithm to model the
varying cerebral spinal fluid (CSF). The study of the time-resolved reflectance
curve at late photon arrival times exhibited peculiar slope-changes upon CSF
layer increase that were confirmed under several measurement conditions. The
performance of the technique suggests good sensitivity to CSF variation, useful
for a fast and non-invasive observation of the dementia progression.Comment: 32 pages, double spaced, 11 figure
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