L. Lleó - Academia.edu (original) (raw)

Papers by L. Lleó

Agricultural Engineering International: The CIGR Journal, 2015

Visible-near infrared reflectance spectra are proposed for the characterization of IRMM 481 peanu... more Visible-near infrared reflectance spectra are proposed for the characterization of IRMM 481 peanuts variety in comparison to powder food materials: wheat flour, milk and cocoa. Multidimensional analysis of reflectance spectra of powder samples shows a specific NIR band centred at 1200 nm that identifies peanut compared to the rest of food ingredients, regardless compaction level and temperature. Spectral range of 400-1000 nm is not robust for identification of blanched peanut. The visible range has shown to be reliable for the identification of pre-treatment and processing of unknown commercial peanut samples. A spectral index is proposed based on the combination of three wavelengths around 1200 nm that is 100% robust against pre-treatment (raw or blanched) and roasting (various temperatures and treatment duration).

3D front-face fluorescence spectroscopy and principal component analysis (PCA) were used to diffe... more 3D front-face fluorescence spectroscopy and principal component analysis (PCA) were used to differentiate between Extra Virgin Olive (EVOO) and Olive Oil (OO). The results showed that 3D front-face fluorescence could be an effective tool to characterize EVOO and OO. Fourteen samples of olive oils were acquired directly from producers and from retail markets and their 3D fluorescence spectra were measured and analyzed. The first principal component of the PCA model retained the most important variability as a combination of freshness due to the presence of antioxidant compounds and chlorophyll; and of oxidation stage due to the presence of oxidation products. Olive oil samples presented different spectral patterns providing different scores for EVOO and OO in the PCA model. EVOO samples selected according to the differences in their scores in the PCA were exposed to indirect light. The evolution of their emission spectra was monitored with a right-angle set-up showing differences in ...

In this study a vision system was applied for assessing enzymatic browning evolution in fresh-cut... more In this study a vision system was applied for assessing enzymatic browning evolution in fresh-cut apples slices stored at 7.5 °C and 85 % HR. Twenty-four slices were analyzed per day: at zero time and after storage for 1,3,7 and 9 days. A classification procedure was applied to virtual images obtained as a combination of the red (R) and blue (B) channel (B/R, R-B and R-B/R+B). In all cases, three images based browning reference classes were generated. An external validation was applied to a second set of samples submitted to the same treatments, obtaining a high percentage of samples correctly classified. Camera classification was evaluated according to colorimetric measurements usually utilized to evaluate enzymatic browning: CIE L*a*b* colour parameters and browning index (Bl). Virtual image based on B/R showed the best sensitivity to reflect the change in colours associated with browning.

Le Centre pour la Communication Scientifique Directe - HAL - Diderot, Aug 22, 2010

The engineer is someone who carries out develops technological solutions to social, industrial or... more The engineer is someone who carries out develops technological solutions to social, industrial or economic by using knowledge of science, mathematics and appropriate experience to find the best solutions to specific problems. Therefore, all engineering studies include core subjects that are taught mainly in the first courses such as mathematics and physics, they provide essential training in order to pursue certain subjects that are applied directly related, such as electrical, construction, topography or engines and machinery, among others, that solve certain technological problems specific to the engineer. A study was carried out with a total of 206 students, focused on the degree of Agricultural Engineer (Curriculum 1999) which is taught at the Technical University of Madrid, was designed to determine the degree of correlation between the results obtained by students in basic engineering materials ("Mathematics I", "Mathematics II", "Physics I" and &...

Resumen Soluble solids content and firmness are some of the most important attributes of peach qu... more Resumen Soluble solids content and firmness are some of the most important attributes of peach quality. These attributes are usually measured by destructive methods, but in the last decades non destructive techniques have given good results in the evaluation of different ...

Food adulteration is an issue of growing concern, specially delicate throughout early stages of f... more Food adulteration is an issue of growing concern, specially delicate throughout early stages of food processing, regarding the control of the original ingredients included in the process and crossed contaminations. The use of Hyperspectral Imaging (HSI) to detect nuts contamination in powder food products is explored in this work. This study deals with two specific problems of using HSI for the detection of food adulterants: the low dose at which they need to be detected and a high similarity between the spectral NIR signatures of adulterating substances. A chemometric method, issued from a pharmaceutical context, is adapted and tested to detect and identify the presence of different species of oily seeds and nuts in a specific type of commercial wheat flour. The proposed approach was able to detect the presence of 5 kinds of contaminants in percentages from 1 to 5%, but not to identify the contaminant species.

The present research is focused on the application of artificial vision to peach ripening assessm... more The present research is focused on the application of artificial vision to peach ripening assessment, avoiding multiplicative and additive effect. Original images were acquired with a hyperspectral camera. Vision allows a spatially detailed determination of the ripening stage of the fruit. Optical indexes are proposed, based on the combination of wavelengths close to the chlorophyll absorption peak at 680 nm. Ind1 corresponds approximately to the depth of the absorption peak, and Ind 2 corresponds to the relative absorption peak. An artificial image of each index was obtained by computing the corresponding reflectance images. Score images have been also computed from Principal Components and Partial Least Squares Analysis. In any case the best performances correspond to such images that correct multiplicative and additive effects. Ind 2 is the preferred index; it showed the highest discriminating power between ripening stages and no influence of convexity. Ind 2 also allowed the dif...

Precision agriculture ’21, 2021

Within the framework of the European project named "SPARKLE" an online course was created after s... more Within the framework of the European project named "SPARKLE" an online course was created after studying educational needs on precision agriculture (PA), state of the art of technologies and a prospective study of the commercial sector. Five educational and research institutions, high-tech farms and enterprises specialized in technology transfer created the syllabus of the course and the platform contents. The course was designed to provide 30 h of student dedication, via online presentations, documents and videos for each topic. A free pilot course started in April 2020 and 385 students from Italy, Portugal, Greece & Spain enrolled. To trace performance and acquisition of competences, questionnaires were completed by students for each topic and a final overall test. Students' opinions about the course were also registered using anonymous polls, and results evaluated, to be able to enhance the Sparkle course for subsequent editions. Students also took part in a business model competition, to solve real challenges proposed by farms, related to the use of these technologies.

Soil and irrigation salinity are key factors in the growth of most of vegetables, causing problem... more Soil and irrigation salinity are key factors in the growth of most of vegetables, causing problems in agriculture, mainly in arid or semi-arid regions. Industrial development and population growth have caused contamination and salinization of surface and underground water and, thereby of agricultural soil. Saline soils represent a great area in the southeast of Spain, where are the main region of horticultural crops in the country. Lettuce (Lactuca sativa L.) is one of the most important crops in this region, being Murcia the main producer region in the European Union. This production is employed mainly for fresh consumption and ready-to-eat product. In general, lettuce presents a moderate sensitivity to salinity. In moderated levels of salinity lettuce crops do not show visible damages in the leaves and seem to be normal, although their growth and yield decrease. They could have deep green leaves, with more density and thickness, and more succulent tissues. When salinity induces im...

Fresh-cut or minimally processed fruit and vegetables have been physically modified from its orig... more Fresh-cut or minimally processed fruit and vegetables have been physically modified from its original form (by peeling, trimming, washing and cutting) to obtain a 100% edible product that is subsequently packaged (usually under modified atmosphere packaging-MAP) and kept in refrigerated storage. In fresh-cut products, physiological activity and microbiological spoilage, determine their deterioration and shelf-life. The major preservation techniques applied to delay spoilage are chilling storage and MAP, combined with chemical treatments (antimicrobial solutions antibrowning, acidulants, antioxidants, etc.). The industry looks for safer alternatives. Consequently, the sector is asking for innovative, fast, cheap and objective techniques to evaluate the overall quality and safety of fresh-cut products in order to obtain decision tools for implementing new packaging materials and procedures. In recent years, hyperspectral imaging technique has been regarded as a tool for analyses conducted for quality evaluation of food products in research, control and industries. The hyperspectral imaging system allows integrating spectroscopic and imaging techniques to enable direct identification of different components or quality characteristics and their spatial distribution in the tested sample. The objective of this work is to develop hyperspectral image processing methods for the supervision through plastic films of changes related to quality deterioration in packed readyto-use leafy vegetables during shelf life. The evolutions of ready-to-use spinach and watercress samples covered with three different common transparent plastic films were studied. Samples were stored at 4 ºC during the monitoring period (until 21 days). More than 60 hyperspectral images (from 400 to 1000 nm) per species were analyzed using ad hoc routines and commercial toolboxes of MatLab®. Besides common spectral treatments for removing additive and multiplicative effects, additional correction, previously to any other correction, was performed in the images of leaves in order to avoid the modification in their spectra due to the presence of the plastic transparent film. Findings from this study suggest that the developed images analysis system is able to deal with the effects caused in the images by the presence of plastic films in the supervision of shelf-life in leafy vegetables, in which different stages of quality has been identified.

Journal of Food Engineering, 2009

Two multispectral maturity classifications for red soft-flesh peaches ('Kingcrest', 'Rubyrich' an... more Two multispectral maturity classifications for red soft-flesh peaches ('Kingcrest', 'Rubyrich' and 'Richlady' n = 260) are proposed and compared based on R (red) and R/IR (red divided by infrared) images obtained with a three CCD camera (800 nm, 675 nm and 450 nm). R/IR histograms were able to correct the effect of 3D shape on light reflectance and thus more Gaussian histograms were produced than R images. As fruits ripened, the R/IR histograms showed increasing levels of intensity. Reference measurements such as firmness and visible spectra also varied significantly as the fruit ripens, firmness decreased while reflectance at 680 nm increased (chlorophyll absorption peak).

Journal of Food Science, 2011

The main objective of this research was to develop an automatic procedure able to classify Rich L... more The main objective of this research was to develop an automatic procedure able to classify Rich Lady commercial peaches according to their ripeness stage through multispectral imaging techniques. A classification procedure was applied to the ratio images calculated as red (R, 680 nm) divided by infxared (IR, 800 nm), that is, R/IR images. Four imagebased ripeness reference classes (A: unripe to D: overripe) were generated from 380 fxuit images (season 1: 2006) by a nonsupervised classification method and evaluated according to reference measurements of the ripeness of the same samples: Magness-Taylor penetrometry firmness, low-mass impact firmness, reflectance at 680 nm (R680, and soluble solids content. The assignment of unknown sample images from those season 1 images (internal validation, n = 380) and of 240 images from the 2nd season (season 2: 2007) to the ripeness reference classes (external validation) was carried out by computing the minimum Euclidean distance (classification distance, C¿) between each unknown image histogram and the average histogram of each ripeness reference class. For both validation phases, firmness valúes decreased and R680 increased for increasing alphabetical order of image-based class letter, reflecting the ripening process. Moreover, 70% (season 1) and 80% (season 2) of the samples below bruise susceptibility firmness were classified into class D.

Food and Bioprocess Technology, 2017

Detailed regions of excitation and emission wavelengths for extra virgin olive oil samples have b... more Detailed regions of excitation and emission wavelengths for extra virgin olive oil samples have been extracted from three dimensional front-face fluorescence spectra. Information was applied to establish a right-angle fluorescence procedure. A right-angle device was assembled and tested with simultaneous excitation from 200 to 400 nm and registration of the fluorescence signal emitted from 400 to 850 nm. A principal component analysis was performed on the signal ranging from 400 to 550 nm from spectra of olive oils officially categorized as extra virgin in order to model the expected variability of compounds related to oxidative processes. Such model was useful to monitor the spectral evolution of extra virgin olive oil samples acquired at retail markets, which were exposed to indirect light during 2 months, through the analysis of the effect on their scores. Three relevant peaks characterized such evolution, with local maxima at around 434 to 437, 464 to 469 and 510 to 518 nm. Polynomial relationship was found between the evolution of those peaks and that of the chlorophyll, at around 670 to 673 nm, with R 2 values of 0.98 and 0.99.

Postharvest Biology and Technology, 2013

The present research is focused on the application of hyperspectral images for the supervision of... more The present research is focused on the application of hyperspectral images for the supervision of quality deterioration in ready to use leafy spinach during storage (Spinacia oleracea). Two sets of samples of packed leafy spinach were considered: (a) a first set of samples was stored at 20 degrees C (E-20) in order to accelerate the degradation process, and these samples were measured the day of reception in the laboratory and after 2 days of storage; (b) a second set of samples was kept at 10 degrees C (E-10), and the measurements were taken throughout storage, beginning the day of reception and repeating the acquisition of Images 3,6 and 9 days later. Twenty leaves per test were analyzed. Hyperspectral images were acquired with a push-broom CCD camera equipped with a spectrograph VNIR (400-1000 nm). Calibration set of spectra was extracted from E-20 samples, containing three classes of degradation: class A (optimal quality), class B and class C (maximum deterioration). Reference a...

Scientific Reports

Total oil content (OC) is one of the main parameters used to characterize the whole of olives ent... more Total oil content (OC) is one of the main parameters used to characterize the whole of olives entering a commercial mill, quantified by the total fresh weight of the lot and the oil concentration (%) assessed in a representative sample on olive paste, by means of chemical extraction. Nuclear magnetic resonance (NMR) and NIR spectroscopy are alternative methods even at individual olives. This work evaluates several strategies to calibrate precise NIR models for the estimation of the total OC. To this end, 278 olives were analysed covering whole season variability in terms of olive fresh-weight and the corresponding OC by chemical extraction in 31 batches. The average spectra from hyperspectral NIR images (1003–2208 nm) were computed for each fruit and the actual OC (g) of those olives determined by NMR (0.09 to 1.29 g with a precision of 0.017 g). According to the results, current batch based assessment of the OC (Soxhlet, %) in mills only reproduces 44% of the underlying heterogenei...

Acta Horticulturae

Fluorescence spectroscopic techniques were applied in a study in order to monitor the evolution o... more Fluorescence spectroscopic techniques were applied in a study in order to monitor the evolution of the spectral pattern of extra virgin olive oil (EVOO) samples exposed to indirect light at room temperature. Detailed information was extracted from three-dimensional front-face (FF) fluorescence spectra with excitation wavelengths ranging from 230 to 646 nm and emission wavelengths ranging from 250 to 698.5 nm. Relevant emission regions were revealed in FF experiments that were useful to study the variability of the characteristic spectral patterns and to develop fast inspection procedures. Such procedures include simultaneous excitation at wavelengths lower than 400 nm, which was proposed and implemented in a rightangle prototype in order to monitor the evolution of EVOO samples exposed to indirect light. Emission signals at local maxima around 400, 434, 464, 513 and 674 nm were found to be relevant. Ongoing research highlights that hyperspectral images provide spectral patterns of the olives, allowing more precise sorting into categories, which would enable the classification into lots of oils with more homogeneous characteristics for subsequent modelling.