Impact parameters related to bruising in selected fruits.

Impact testing with an instrumented free-fallingmass (50.4 g) device was applied to three varities of pears and two varieties of apples, forincreasing ripeness stages and impact energy (2 to 20 cm drops). Impact parameters were studied in relation to bruise and to ripeness, establishing relations between them and with the different characteristics of the fruits.

Impact bruises in pomaceae fruits: Evaluation methods and structural features.

Using a laboratory impact tester, impacts were applied to fruits of different varieties of apples and pears. The response to impact was analized, and many parameters were recorded, to be correlated to bruise susceptibility and to ripeness changes. Different methods for the detection and evaluation of the bruised Area and its features were studied, using direct observation and various reactives. Different types of bruises were established.

Impact parameters in relation to bruising and other fruit properties.

Impact response in fruits, primarily appl.es and pears (Pomaceae fruits), has been studied during the last five years. Using a laboratory impact testing device and also free-fall tests of instrumented apples, a significant body of results has been established, relative to the parameters which best characterize the impact response of these materials, and to their correlation with bruise damage, variety and ripeness level of the fruits. Bruise damage, measured as the size and/or volume of the affected fruit tissue is related primarily to applied energy (i.e. mainly drop height) for a given variety at a given ripeness stage. The relevant impact response parameters are maximum deformation (DM), permanent deformation (DP), maximum impulse (IM), maximum impact force (FM), maximum value of the force/time slope during impact (F/T) and impact time (T). The effect of ripeness differences was also studied in selected varieties of pears, being the most relevant parameters: maximum force (FM) and F/T slope.

Sensing physical stage of fruits by their response to non destructive impacts.

Fruits of two varieties of both apples and pears were tested in the laboratory to measure their response to a small energy impact applied by an impact tester. Samples of fruits of increasing maturity were tested during several weeks. Non-destructive impacts and other destructive and non-destructive measurements of post-harvest ripeness were applied. A new software was created to control the impact test, calculate the eleven parameters, and sort out the fruit. This software needs a data base and may create new ones. The implementation of an on-line impact device for automatic detection of texture is being designed (patent pending).

Factors influencing apple and pear physical properties and bruise susceptibility.

Fruit turgidity and firmness have shown to influence impact bruise susceptibility in apples and pears. Analysis of the impact response showed that stresses in the tissues are higher in turgid fruits, so they are more susceptible to bruising. A physical parameter, deformation at skin puncture, was able to detect fruit turgidity changes and showed to be related to bruise susceptibility.

Controlling moisture loss as a tool to reduce bruise susceptibility.

A method to reduce the bruise susceptibility of apples by controlling the moisture loss of the fruit was evaluated. Previous research indicates that reduction of the relative humidity of the storage air leads to an immediate effect on the weight loss and on skin properties and to a lower bruise susceptibility of apples. The diffusion equation is used to determine the waterpotential profile inside the fruit during storage. Characteristics of the waterpotential distribution in the fruit are related to measured bruise volumes. The results indicate how /this model can be used to control bruise susceptibility.

Influence of fruit turgidity and firmness on apple bruise susceptibility.

Bruise damage is a major cause of quality loss for apples. It would be very useful to establish a method of characterizing bruise susceptibility in order to improve fruit handling, sometimes Magness-Taylor firmness is used as an indirect guide to handling requirements. The objective of the present work was to achieve a better bruise susceptibility prediction.

Effect of impacting radius of curvature on firmness sensing of fruits in a sorting system.

Fruits of two varieties of both apples and pear were tested to measure their response to small energy impact applied by a impact tester with two spherical tips of different radious of curvature ( RA = 2.48 cm and RB = 0.98 cm) and equal mass were used. In the four varieties studied, the size of bruise was smaller with a spherical tip RA than with tip RB . The non-destructive impact test would cause less damage with a spherical impactor with a radious bigger than 0.98 cm.

Mealiness assessment in fruits using MRI techniques.

Mealiness is a sensory attribute that cannot be defined by a single parameter but through a combination of variables (multidimensional structure). Previous studies propose the definition of mealiness as the lack of crispiness, of hardness and of juiciness. Current aims are focused on establishing non destructive tests for mealiness assessment. MultiSliceMultiEcho Magnetic resonance images (MRI, 64*64pixels) have been taken corresponding to a 3ms of Echo time. Small samples of Top Red apples stored 6 months at controlled atmosphere (expected to be non mealy) and 2°C (expected to be mealy) have been used for MRI imaging. Three out of four apples corresponding to the sample maintained at controlled atmosphere did not develop mealiness while three out of four fruits corresponding to the sample stored at 2°C became mealy after 6 month of storage. The minimum T2 values/image obtained for the mealy apples shows to be significantly lower when compared with non mealy apples pointing that a more dis-aggregated structure leads to a quicker loss of signal Also, there is a significant linear correlation (r=-0.76) between the number of pixels with a T2 value below 35ms within a fruit image and the deformation parameter registered during the Magness-Taylor firmness test. Finally, all the T2 images of the mealy apples show a regional variation of contrast which is not shown for non mealy apples. This variation of contrast is similar to the MRI images of water-cored apples indicating that in these cases there is a differential water movement that may precede the internal browning.

Fruit by fruit identification of mealy peaches. Extraction of storage features.

Mealiness is a negative attribute of sensory texture, characterised by the lack of juiciness decrease in the total amount of of water content of tissues. Peach mealy textures are known as \ and leatheriness. Besides the lack of juiciness and flavour, that characterises mealy fruits, in associated with internal browning near the stone and an incapacity of ripening although there i ripe appearance. It is considered as a physiological disorder that appears in stone fruits probably < unbalanced pectolitic enzyme activity during storage. Since January 1996, a wide EC Project entitled: "Mealiness in fruits. Consumer perception and i detection" is being carried out. Within it, the Physical Properties Laboratory (ETSIA-UPM) working to develop instrumental procedures to detect mealiness in different types of fruits (s contributions by Barreiro to AgEng). The results obtained have shown to correlate well with \ measurements in apples (Barreiro et al), also we have succeeded in identifying individual mealy j the basis of instrumental measurement in peaches. The definition of these texture categories will be used in further studies as a base for new individual classification.

Non-destructive optical characterisation of fruits with time-resolved reflectance spectroscopy.

Increasing attention is being paid to the possible development of non-invasive tests for the assessment of the quality of fruits We propose a novel non-destructive method for the measurement of the internal optical properties of fruits and vegetables by means of time resolved reflectance spectroscopy in the visible and NIR range. A fully automated instrumentation for time-resolved reflectance measurements was developed It is based on mode-locked laser sources and electronics for time-correlated single photon counting, and provides a time-resolution of 120-160 ps The system was used to probe the optical properties of several species and varieties of fruits and vegetables in the red and NIR range (650-1000 nm). In most fruits, the absorption line shape is dominated by the absorption peak of water, centred around 970 nm Generally, the absorption spectra also show the spectral features typical of chlorophyll, with maximum at 675 nm In particular, for what concerns apples, variations in peak intensity are observed depending on the variety, the degree of ripeness as well as the position on the apple. For all the species and varieties considered, the transport scattering coefficient decreases progressively upon increasing the wavelength.

Non-destructive optical characterization of fruits in the red and near infrared.

Increasing attention is being paid to the possible development of non-invasive tests for the assessment of the quality of Fruits. We propose a novel non-destructive method for the measurement of the internal optical properties of fruits and vegetables by means of lime-resolved reflectance spectroscopy in the visible and NIR range. A Fully automated instrumentation for time-resolved reflectance measurements was developed. It is based on mode-locked laser sources and electronics for time-correlated single photon counting, and provides a time-resolution of 120-160 ps. The system was used to probe the optical properties of several species and varieties of Fruits and vegetables in the red and NIR range (650-1000 nm). In most Fruits, the absorption line shape is dominated by the absorption peak of water, centred around 970 nm. Generally, the absorption spectra also show the spectral features typical of chlorophyll, with maximum at 675 nm. In particular, for what concerns apples, variations in peak intensity are observed depending on the variety, the degree of ripeness as well as the position on the apple. For all the species and varieties considered, the transport scattering coefficient decreases progressively upon increasing the wavelength.

A procedure for testing padding materials in fruit packing lines.

Padding materials are commonly used in fruit packing lines with the objective of diminishing impact damage in postharvest handling. Two sensors, instrumented sphere IS 100 and impact tester, have been compared to analyze the performance of six different padding materials used in Spanish fruit packing lines. Padding materials tested have been classified according to their capability to decrease impact intensities inflicted to fruit in packing lines. A procedure to test padding materials has been developed for "Golden" apples. Its basis is a logistic regression to predict bruise probability in fruit. The model combines two kinds of parameters: padding material parameters measured with IS, and fruit properties.

New version of a laboratory impact device for firmness sensing of fruits.

Results of previous studies conducted by different researchers have shown that impact techniques can be used to evaluate firmness (Delwiche et al., 1989; Delwiche et al.;1996; Jaren et al., 1992; Ruiz Altisent et al., 1996). To impact the fruit with a small spherical impactor of known mass and radius of curvature and measure the acceleration of the impactor is a technique described by Chen et al. (1985) and used by several researchers for sensing fruit firmness (Jaren et al., 1992; Correa et al.; 1992). The advantages of this method vs. a force sensor that measures the force as a function of time is that the measured impact-acceleration response is independent of the fruit mass and is less sensitive to the variation in the radius of curvature of the fruit (Chen et al., 1996). Ruiz Altisent et al. (1993) developed and used a 50 g impactor with a 19 mm diameter spherical tip, dropping from different height for fruits (apples, pears, avocados, melons, peaches ...). Another impact device for firmness sensing of fruits was developed by Chen and Ruiz Altisent (1996). They designed and fabricated an experimental low-mass impact sensor for high-speed sensing of fruit firmness. The impactor consisted of a semi-spherical impacting tip attached to the end (near the centre of percussion) of a pivoting arm. Impact is done by swinging the impactor to collide with the fruit. It has been implemented for on-line use. In both devices a small accelerometer is mounted behind the impacting tip. Lateral impactor and vertical impactor have been used in laboratory and the results from non-destructive impact tests have contributed to standardise methods to measure fruit firmness: Barreiro (1992) compared impact parameters and results of Magness-Taylor penetration tests for apples, pears, apricots [and peaches; Agulheiro (1994) studied the behaviour of the impact parameters during seven weeks of cold storage of two melon varieties; Ortiz (1998) used low energy impact and NIR procedures to segregate non crispy, non firm and soft peaches. Steinmetz (1996) compared various non-destructive firmness sensors, based on sound, impact and micro-deformation.

Desarrollo de un procedimiento para tipificar materiales amortiguadores para su uso en líneas de manipulación de fruta.

Two sensors, instrumented sphere IS 100 and impact tester, have been compared to analyze the performance of six different padding materials used in Spanish fruit packing lines. Padding materials tested have been classified according to their capability to decrease impact intensities inflicted to fruit in packing lines. A procedure to test padding materials has been developed for "Golden" apples. Its basis is a logistic regression to predict bruise probability in fruit. The model combines two kinds of parameters: padding material parameters measured with IS, and fruit properties.