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.

Differences in the structural response of 'granny-smith' apples under mechanical impact and compression

Apple fruits, cv. Granny Smith, were subjected to mechanical impact and compression loads utilizing a steel rod with a spherical tip 19 mm diameter, 50.6 g mass. Energies applied were low enough to produce enzymatic reaction: 0.0120 J for impact, and 0.0199 J for compression. Bruised material was cut and examined with a transmission electron microscope. In both compression and impact, bruises showed a central region located in the flesh parenchyma, at a distance that approximately equalled the indentor tip radius. The parenchyma cells of this region were more altered than cells from the epidermis and hypodermis. Tissues under compression presented numerous deformed parenchyma cells with broken tonoplasts and tissue degradation as predicted by several investigators. The impacted cells supported different kinds of stresses than compressed cells, resulting in the formation of intensive vesiculation, either in the vacuole or in the middle lamella region between cell walls of adjacent cells. A large proportion of parenchyma cells completely split or had initiated splitting at the middle lamella. Bruising may develop with or without cell rupture. Therefore, cell wall rupture is not essential for the development of a bruise, at least the smallest one, as predicted previously

Damage mechanisms in the handling of fruits

The recognition of an increasing and worldwide demand for high quality in fruits and vegetables has grown in recent years. Evidence of severe problems of mechanical damage is increasing, and this is affecting the trade of fruits in European and other countries. The potential market for fresh high-quality vegetables and fruits remains restricted by the lack of quality of the majority of products that reach consumers; this is the case for local as well as import/export markets, so a reduction in the consumption of fresh fruits in favour of other fixed-quality products (dairy in particular) may become widespread. In a recent survey (King, 1988, cited in Bellon, 1989), it appears that, for the moment, one third of the surveyed consumers are still continuing to increase their fresh produce consumption. The factors that appear as being most important in influencing the shopping behaviour of these consumers are taste/flavour, freshness/ripeness, appealing look, and cleanliness. Research on mechanical damage in fruit and vegetables has been underway for several years. The first research made on physical properties of fruits was in fact directed towards analysing the response to slow or rapid loading of selected fruits (Fridley et al, 1968; Horsefield et al., 1972). From that time on, research has expanded greatly, and different aspects of the problem have been approached. These include applicable mechanical models for the contact problem, the response of biological tissues to loading, devices for detecting damage causes in machines and equipment, and procedures for sensing bruises in grading and sorting. This chapter will be devoted to the study of actual research results relative to the cause and mechanisms of mechanical damage in fruits (secondarily in vegetables), the development of bruises in these commodities, the models that have been used up to now, and the different factors which have been recognized as influencing the appearance and development of mechanical damage in fruits. The study will be focused mainly on contact-damage - that is, slow or rapid loads applied to the surface of the products and causing bruises. (A bruise is defined as an altered volume of fruit tissues below the skin that is discoloured and softened.) Other types of mechanical damage, like abrasion and scuffing, punctures and cuts, will be also mentioned briefly.

Study of packing lines for stone fruits and citrus using two instrumented spheres in some cooperatives in the region of Murcia (Spain).

Two instrumented spheres IS 100 were used to evaluate the quality of post-harvest operations. Results obtained from measurements made with both IS (8.8 cm 0 and 6.2 cm 0) show significant differences. Both IS measure the same values of the same variables for soft materials, but not for hard surfaces. Four packing lines belonging to different cooperatives of the region of Murcia (two for stone fruits and two for citrus) were tested. IS values obtained in transfers belonging to the tested lines lay well above 50 g's in most of them Much higher impact intensities are registered in citrus lines than in stone fruit packing lines. To study the incidence of a certain packing line on different products an interaction fruit-packing line test was perf01med. In all cases, more than 50% of fruits belonging to the post-handling sample showed some kind of damage. Bruises evolve after 48 hours storage at room temperature.

Models for the prediction of handling damage in citrus and peaches grading lines, related to their physical properties.

Fruit damage during harvesting and handling is a standing problem, particularly for susceptible fruits like peaches and apricots. The resulting mechanical damage is a combination of fruit properties and damage inflicting effects due to procedures and to the equipment. Nine packing lines in the region of Murcia (SE Spain) have been tested with the aid of two different-size electronic fruits IS-100. Probabilities of impacts above three preset thresholds (50 g's, 100 g's and 150 g's) were calculated for each transfer point. Interaction fruit-packing line tests have been also performed in order to study the real incidence of packing lines on natural produce: apricots (1 variety), peaches (3 v.), lemons (1 v.) and oranges (3 v.). Bruises of handled and not handled samples of fruits were compared.

Quality assurance systems in the production and marketing of fresh peaches.

Due to the fast rate of peach post-harvest ripening, damage due to mechanical handling, externally appreciated as bruises and soft areas, is a real problem that leads to an early harvesting and poor quality of the fruits, as perceived by the consumers. More and more, the European consumer asks for good taste and freshness of fruits and vegetables, and these quality factors are not included in standards, nor in most of the producers' practices. Fruit processing and marketing centres (co-operatives) are increasingly interested in adopting quality controls in their processes. ISO 9000 procedures are being applied in some food areas, primarily milk and meat processors, but no generalised procedures have been developed until the present time to be applied to fresh product processes. All different peach and nectarine varieties that are harvested and handled in Murcia cooperatives and sold in a large supermarket in Madrid were analysed during the whole 1997 season (early May to late August). A total number of 78 samples of 25 fruits (co-operative) or 10 fruits (market), were tested in the laboratory for mechanical, optical, chemical and tasting quality. The variability and relationships between all these quality parameters are presented and discussed, and sampling unit sizes which would be advisable for quality control are calculated.