POSTHARVEST TECHNOLOGY 136 58 LANDTECHNIK 3/2003 Fruit Stress during Road Transport of Tomatoes in Loose Bulk

Bernd Oberbarnscheidt, Bernd Herold, Martin Geyer, Potsdam-Bornim, Béla Borsa, László Kovács, Frigyes Jakovác, Gödöllö Ungarn
A t the receiving point of a tomato processing plant, quality and mass losses of tomato fruit frequently exceeded 20 %. These losses were mainly due to cracked fruit. Accordingly, the degree of damage was analysed on fruit samples taken on the one side from the conveyor belt of a combine harvester, and on the other side from the tomato stock during unloading of the truck in the processing plant. Visual inspection indicated appreciable lower degree of damage after harvest than after transport by
more » ... after transport by truck. For this reason, the transport conditions were assumed to be the main source of tomato fruit damage. Material and methods The process of mechanical damage of fruit is very complex. Therefore, studies were carried out that cover both the visual inspection of the degree of damage of well defined fruit samples as well as measuring the truck motion and the pressure load on tomato fruit in a bulky load during transportation. For the samples, tomato fruits were carefully picked from the plants. One half of these intact fruits were subjected to a well-defined mechanical pre-load, simulating the effect of the mechanical harvest including loading onto the truck. Each of these fruits was dropped from 1 m height onto a wooden plate. Every fruit with or without mechanical pre-load was numbered. Thereafter, equal numbers of fruits of each of both treatments were filled into test bags. These test bags were placed into the tomato bulk during the loading of the truck. For the tests with a common truck, one half of the test bags were placed in a height of 20 cm above the platform (bottom layer), the others were placed in a height of 60 cm (medium layer). Further tests were carried out simulating the truck by using a pickup car. In this case, the tomatoes were filled into a container with appropriate loading height (test bags placed only in bottom layer). In both tests, after loading onto common truck as well as onto pick up car, typical sapping of tomato juice was observed due to static load onto the lower fruit layers and cracking of fruit subjected to mechanical pre-load (Fig. 1). The transportation tests were carried out under similar road and speed conditions. The trip with the truck to the processing plant took about 1 h, while the trips with the pick up car lasted 10 and 60 min on the road. Before each road trip, the pick up car covered about 1 km on a country lane. Before and after the transportation test, visible fruit damage in the test bags was evaluated and classified into four levels (Fig. 2). During transportation, the tri-axial accelerations of the vehicle platform and the pressure load onto the fruit in the bottom layer were recorded with sampling rates of 200 Hz. The pressure load data were acquired using a modified version of Pressure Measuring Sphere PMS-60 and transferred via cable to the PC, because the capacity of PMS-60 internal memory would not be sufficient for long term measurements. Fruit damage due to transport Visual inspection of fruit in test bags showed that the degree of fruit damage for fruit without mechanical pre-load was very low. However , mechanical harvest always caused me-The mechanical harvest and transport of industrial tomatoes in Hun-gary cause considerable losses in quality and quantity. Tomatoes for industry are harvested with a complete harvester, similar to a potato harvester. The harvest is continuously loaded with a belt con-veyor on parallel driving lorries, which transport it afterwards to the processing facility. Mechanical stress and damage on tomatoes were tested jointly by the Institute of Agricultural Engineering of Gödöllö and ATB in a Hungarian cooperative. Results of this investigation are presented here.