The use of hyperspectral imaging in the visible and near infrared region to discriminate between table grapes harvested at different times

Traditional analytical methods applied to the measurement of grape maturity and quality index in order to assess optimal harvest time have been proved to be slow and destructive. Therefore, non-destructive analytical techniques, including spectroscopy, can be a valid support for the choice of the best time to harvest. This study evaluated the feasibility of using a visible and near infrared spectral scanner (v. 1.4; DV Srl, Padova, Italy) with a detector in the region between 400-1000 nm to discriminate between grapes harvested at different times. Twelve clusters were harvested at 5 different times between October and December 2011. Spectra were acquired with a Spectral scanner on 3 intact berries from each bunch. These were randomly selected from top, medium and bottom zones, for a total of 180 spectra. Classification models were construed comparing 2 methods: soft independent modelling of class analogy (SIMCA) and partial least squares discriminant analysis (PLS-DA). The SIMCA model was developed building individual principal component analysis (PCA) models for the spectra of each harvest time. Different pre-treatment methods were tested in order to enhance the power of the model, thus enhancing the score differences among samples from different harvest times. The transformation that allowed the best statistical separation among scores of grapes from different harvest times was the second derivate of Norris. Therefore, the PCA model obtained from the spectra subjected to this pre-treatment was used for SIMCA classification. The PLS-DA model were developed applying the PLS2 algorithm. In order to construct discriminant models to classify bunch spectra according to the 5 harvest times, spectral variations were correlated with the 5 categories established. No pretreatments were previously applied in this last case since they did not improve the final result. The SIMCA method was unable to correctly classify grapes from harvest time 2 (59% of correct classification) and was less efficient compared to the PLS-DA model. Using the PLS-DA model, all the grapes were correctly classified (100%) with the exception of those from harvest time 5 (94%). The overall results demonstrate that this method has excellent potential for discriminating grape quality

Physio-chemical quality attributes of ‘Italia’ grapes from organic and conventional farming at harvest and during storage

This study was aimed to investigate the quality at harvest and during storage of organically and conventionally grown ‘Italia’ grapes, collected from 2 different locations in Southern Italy. Four vineyards were chosen in order to have an organic and a conventional farm in each location. Before harvest, six plants per vineyard were randomly selected and considered as treatment replicate. Three bunches were harvested and labelled from each plant. In laboratory each bunch was weighed and thirty berries per bunch were detached and used for initial determination which included morphological (berry weight and dimension, peel thick-ness) and physical (berry color and firmness) attributes, maturity indices (respiration rate, soluble solids content and titratable acidity), and nutritional composition (phenol content, antioxidant activity, sugar and organic acid composition, ascorbic acid content). Then, the bunches from each replicate were kept in individual 15-L jars at 0°C and connected to a humidified air flow throughout the whole experiment. After 7 and 14 days of storage, respiration rate, weight loss, physical and nutritional attributes were also monitored on 20 berries per bunch. Location and agricultural practices affected to a different extent several grapes quality attributes, both at harvest and during storage. Maturity stage, sugar content and berry color were significantly affected by the location, while antioxidant-related compounds were significantly higher in organic grapes. Plant production and bunch weight were significantly higher for conventionally grown grapes, which also received the highest evaluation of external appearance, in terms of stalk dehydration and berry general aspect. Differences among conventional and organic grapes were maintained, for each location, during storage at 0°C. Conventional grapes maintained a higher visual quality during storage, resulting after 14 days below the limit of marketability (score 3) but above the edibility limit (score 2); whereas in one location organic grapes were judged not edible. Results showed a higher nutritional value in grapes obtained with the organic farming system although in terms of visual quali-ty, storability and yield, conventional fruit had a better performance

The use of hyperspectral imaging in the visible and near infrared region to discriminate between table grapes harvested at different times

Traditional analytical methods applied to the measurement of grape maturity and quality index in order to assess optimal harvest time have been proved to be slow and destructive. Therefore, non-destructive analytical techniques, including spectroscopy, can be a valid support for the choice of the best time to harvest. This study evaluated the feasibility of using a visible and near infrared spectral scanner (v. 1.4; DV Srl, Padova, Italy) with a detector in the region between 400-1000 nm to discriminate between grapes harvested at different times. Twelve clusters were harvested at 5 different times between October and December 2011. Spectra were acquired with a Spectral scanner on 3 intact berries from each bunch. These were randomly selected from top, medium and bottom zones, for a total of 180 spectra. Classification models were construed comparing 2 methods: soft independent modelling of class analogy (SIMCA) and partial least squares discriminant analysis (PLS-DA). The SIMCA model was developed building individual principal component analysis (PCA) models for the spectra of each harvest time. Different pre-treatment methods were tested in order to enhance the power of the model, thus enhancing the score differences among samples from different harvest times. The transformation that allowed the best statistical separation among scores of grapes from different harvest times was the second derivate of Norris. Therefore, the PCA model obtained from the spectra subjected to this pre-treatment was used for SIMCA classification. The PLS-DA model were developed applying the PLS2 algorithm. In order to construct discriminant models to classify bunch spectra according to the 5 harvest times, spectral variations were correlated with the 5 categories established. No pretreatments were previously applied in this last case since they did not improve the final result. The SIMCA method was unable to correctly classify grapes from harvest time 2 (59% of correct classification) and was less efficient compared to the PLS-DA model. Using the PLS-DA model, all the grapes were correctly classified (100%) with the exception of those from harvest time 5 (94%). The overall results demonstrate that this method has excellent potential for discriminating grape quality

The effect of 1-methylcyclopropene (1-MCP) application before and after cutting on the shelflife extension of fresh-cut tomatoes

[ENG] Exposing partially ripe fruit to 1-methylcyclopropene (1-MCP) before or after cutting may be a useful supplement to proper temperature and relative humidity management for maintaining quality of fresh-cut fruit products. In this study tomato fruits were exposed to 0.5 ppm of 1-MCP for 24 hours, while tomato slices were exposed to the same concentration of 1-MCP for 6 hours. Untreated slices were used as control. Initially and after 3, 7, and 9 days of storage at 5 °C the following quality attributes were evaluated: flesh and skin color, firmness, total soluble solids content, titratable acidity and weight loss. In addition, respiration rate and ethylene production were measured. Fresh-cut tomato slices treated with 0.5 ppm of 1-MCP before cutting showed higher firmness retention than untreated slices, while slices treated after cutting showed an intermediate firmness value. Color development was delayed in both 1-MCP treated samples, which presented higher skin and flesh hue angle value compared with untreated slices. The initial decrease in skin hue angle value was reduced in slices treated either before or after cutting, while those treated after cutting showed the highest value of hue angle of the flesh. Application of 1-MCP did not affect the respiration rate, but slowed down C2H4 production in slices treated after cutting, compared to slices from untreated tomatoes. No significant effect of 1-MCP treatment was observed on titratable acidity, while for soluble solids content slices treated after cutting showed a value significantly higher than untreated slices. Application before processing resulted most effective for firmness retention, while all other effects were more visible when application followed cutting. [SPA] La exposición de tomate parcialmente maduro a 1-metilciclopropeno (1-MCP) antes o después del corte puede representar un método útil, sumado al control de la temperatura y humedad, para mantener la calidad del producto mínimamente procesado. En este estudio los tomates enteros han sido expuestos a 0,5 ppm de 1-MCP durante 24 horas, mientras las rodajas se expusieron a la misma concentración durante 6 horas. Como control se utilizaron rodajas de tomate no tratadas. Inicialmente y tras 3, 7, y 9 días de conservación a 5 ºC se evaluaron los siguientes atributos cualitativos: color (piel y pulpa), firmeza, contenido en sólidos solubles, acidez titulable y pérdida de peso. Además, se midieron la tasa respiratoria y de producción de etileno. Las rodajas de tomate tratadas con 0,5 ppm de 1-MCP antes del corte mostraron mayor mantenimiento de firmeza que las no tratadas, mientras que las rodajas tratadas después del corte han mostrado un valor intermedio de firmeza. El desarrollo del color se ha ralentizado en los dos tratamientos realizados con 1-MCP; las rodajas tratadas han mostrado un mayor valor del ángulo de tinta de la piel y de la pulpa respecto al control. La disminución inicial del ángulo de tinta de la piel se redujo en los dos tratamientos, mientras las rodajas tratadas después del corte han mostrado un mayor valor del ángulo de tinta de la pulpa. La aplicación del 1-MCP no ha afectado a la actividad respiratoria pero ha disminuido la emisión de etileno en rodajas tratadas después del corte respecto a las rodajas no tratadas con 1-MCP. No se ha observado efecto significativo del tratamiento sobre la acidez titulable, el contenido de sólidos solubles de las rodajas tratadas después del corte se ha mostrado más alto que el control. La aplicación del 1-MCP antes y después del procesado ha resultado más efectiva para el mantenimiento de la firmeza y del color, respectivamente

COLOR DEGRADATION KINETICS OF REHYDRATED ‘BORLOTTO’ BEANS STORED IN DIFFERENT GAS ATMOSPHERES AS MEASURED BY IMAGE ANALYSIS

Rehydrated legume seeds represent an important ingredient for ready-to-cook fresh soups packaged in a modified atmosphere. The aim of this work was to define an image analysis system for the evaluation of ‘Borlotto’ bean color changes during storage in different gas compositions. ‘Borlotto’ bean seeds were rehydrated in water for 12 hours and stored at 5 °C in controlled atmosphere using 4 different gas compositions: 3 % O2, 10 % CO2 in air, 3 % O2 + 10 % CO2, and air as control. An algorithm in Matlab was codified to measure color of the seed red stripes and ground color (L*, a*,b*, Hue angle and Chromaticity). Sensorial analyses based on the hedonic scale (from 5=excellent to 1=very bad) of the seed appearance were also carried out. Seed color and appearance changes over time were monitored initially and after 5, 10 and 15 days of storage at 5 °C. The obtained data were used to model the quality of degradation attributes over time, that were fit into first order kinetics. A gas composition with 3 % O2 + 10 % CO2 induced the least modification on the seed ground color, which received a highest appearance evaluation up to 10 days of storage, also showing that visual appearance changes were mostly affected by the variation of the seed ground color

Spectra evolution over on-vine holding of Italia table grapes: prediction of maturity and discrimination for harvest times using a Vis-NIR hyperspectral device

Measurement of certain grape quality parameters (sugars, acidity, and pH-value) is essential for the determination of the optimum harvest time. Non-destructive analytical techniques, including near infrared (NIR) spectroscopy, can be valid alternatives to traditional analytical methods for the determination of maturity indexes, enabling the possibility of on-field applications. This work aims to study the reliability to monitor spectra changes related with ripening of table grapes and to select optimal wavelengths for the discrimination of bunches from different harvests, in addition to the prediction of total soluble solids, pH, titratable acidity, phenols and antioxidant activity of table grapes. Grapes were harvested four times from the same plants at day 0 (I HT), and after 11 (II HT), 27 (III HT) and 48 (IV HT) days. Spectra were acquired from the images obtained using a spectral scanner Vis-NIR (ver 1.4.; DV Srl, Padova, Italy), with a detector in the region between 400-1000 nm principal component analysis was used to remove outliers followed by spectra pre-treatment. The best prediction model was achieved for soluble solids with the regression coefficient values of 0.91 for calibration and 0.88 for validation followed by titratable acidity (0.71 and 0.78) and antioxidant activity (0.68 and 0.62). In addition an excellent correlation was observed between spectra and days before harvest (R2 of 0.98 for calibration and prediction models) indicating that is possible to relate spectra changes with ripening, leading also to the effective discrimination of the fruits from the different harvest times. The results showed that this technique may be a valid support to select the optimal harvest time also based on the prediction of the maturity related constituents

Effects of equipments and processing conditions on quality of fresh-cut produce

A wide range of fresh conveniently packaged, minimally processed products are available on both local and global market in response to consumer demand for ready to eat food. Majority of these products are leafy vegetables, which are highly susceptible to quality changes during minimal processing operations (trimming, cutting, washing, drying, and packaging). Despite the available precautionary measures for maintaining quality attributes of raw and processed material, quality degradation due to minimally processing is unavoidable, also considering that a peeling, trimming and/or cutting operation is always present except than for baby leaves and small fruits. In addition, other operations as washing and drying are known to cause mechanical stresses and loss of sugars and nutrients. However, the extent to which quality is compromised depends on the produce and on the processing conditions, including equipment and their operational settings. This review aims to describe the main processing operations and equipment used, resuming the available information on their impact on final quality of fresh-cut products over storage, in order to identify areas for future research aiming to the enhancement of product qualit

Designing a modified atmosphere packaging (MAP) for fresh-cut artichokes

‘Catanese’ artichoke quarters were packaged in active modified atmosphere (5% O2+10% CO2) in four different materials or in air in macro-perforated bags used as control (CTRL), and stored at 4°C. Materials used for modified atmosphere packaging (MAP) were: polylactic acid (PLA), polylactid acid with one line of micro-perforation (PLA MF1), polypropilene with two lines of micro-perforations (PP MF2), and polypropylene + polyamide with two lines of microperforations (PP+PA MF2). Initially and after 2, 4, and 9 days, overall artichoke appearance, color and weight loss were monitored. O2 and CO2 concentrations within the packages were detected initially and after 1, 2, 17, 24.5, 41.5, 49.5, 120 and 216 h (end of the experiment). Also, at the last sampling date ethanol and acetaldehyde accumulations in artichoke tissue were measured. All the micro-perforated films maintained gas levels within the range of O2>3% and CO2<15%, defined as “safe”, with a positive effect on quality: all samples remained above the limit of marketability until the end of the experiment, without significant differences among them, but showed a slight better overall appearance and, accordingly, a better retention of color parameters when compared with CTRL samples. Complete anaerobic condition (16% CO2 and 0% O2) developed in PLA bags where blackening of cut bracts and receptacle was observed, while black spots appeared on outer bracts, causing drastic quality reduction; samples fell below the limit of marketability after just 2 days. Also a significant accumulation of ethanol and acetaldehyde was found in these samples. Optimizing MAP made it possible to maintain the desired gas condition, with positive effects on quality of the produce in absence of any stabilizing treatment, for 9 days

Design and preliminary test of a fluidised bed photoreactor for ethylene oxidation on mesoporous mixed SiO2/TiO2 nanocomposites under UV-A illumination

Ethylene (C2H4) is a plant hormone that has numerous effects on many horticultural and ornamental crops. It accelerates senescence, stimulates chlorophyll loss, enhances excessive softening, promotes discoloration and browning during storage of fresh produce. Among the techniques used to remove or inhibit ethylene action during postharvest handling of fresh products (potassium-based system, high temperature catalytic oxidation, inhibition of ethylene receptors), the use of titanium oxide (TiO2)-based materials with photocatalytic activity under ultraviolet (UV) light is one of the most promising. A fluidised-bed photoreactor (FBP) was designed to decompose ethylene in the storage room atmosphere, and the relative prototype was manufactured. Since TiO2 powder alone is not suitable for use within a fluidised bed, preliminary tests to select the best support were performed. Alumina microspheres showed a good fluidisation behavior; its functionality was tested with different kind of support material and actual photocatalytic activity was tested using SiO2/TiO2-coated alumina microspheres. A reduction of approximately 72% of ethylene concentration in the tested 40 ppm ethylene gas mixture was observed after 4.5 h of 36W UV light exposure. FBP resulted to be suitable to avoid the detrimental presence of C2H4 in the atmosphere surrounding fresh products within cold storage rooms