Bernd Herold

Fruit contact pressure distributions : equipment

A commercially available tactile sensing system allows the pressure distribution between contacting surfaces to be determined in real time. This sensor has been used to determine the pressure distribution between fruits, mainly apples, in contact with flat and curved surfaces. The sensor consists of a thin flexible plastic film containing a grid of sensitive material that responds according to the pressure at each point on the mesh. Details of the sensor and examples of experimental results obtained with the system are described. The device was found to have a non-linear output, and the data needed to be calibrated to improve the accuracy of the results. Examples of the surface pressure distribution generated in the contact area as apple fruit were loaded to failure, and the effects of commercial packaging materials on pressure distribution are presented.

A PRESSURE MEASURING SPHERE FOR MONITORING HANDLING OF FRUIT AND VEGETABLES

Abstract An “artificial fruit” was developed to detect damage sources for perishable fruit and vegetables during practical harvesting and handling. This Pressure Measuring Sphere (PMS) is designed robustly in order to tolerate usual mechanical loads under practical conditions. It consists of a liquid-filled rubber ball with a pressure data acquisition system embedded inside. The system contains a stand-alone microcomputer, a fluid pressure sensing unit and a battery. The PMS is capable to collect all load events touching its skin, if they exceed a preset threshold, and to store them together with time from an internal clock. Calibration tests confirmed that the PMS senses static as well as dynamic mechanical loads. Measured load data were nearly reproducible under static load conditions (variation coefficient about 4%). Under dynamic load conditions a minimum of 15 measuring runs provide for representative results (variation coefficient about 20%).

Comparison of Electronic Fruits for Impact Detection on a Laboratory Scale

Mechanical loads cause severe damage to perishable agricultural products. In order to quantify the mechanical impact during harvest and postharvest processes, several electronic fruits have been developed. The objective of the work described here was to compare on a laboratory scale different types of impact acceleration recording electronic fruits: Mikras implanted in a real potato tuber as well as in a dummy tuber, IRD, Smart Spud and TuberLog. The acquisition of mechanical impacts was performed using a drop simulator with optional steel or PVC as impact material as well as a processing line simulator. Our results show that drops from 10 cm height on PVC caused similar peak accelerations of Mikras implanted in a real potato or a dummy, IRD and TuberLog. When dropped onto steel however, IRD, TuberLog and Mikras implanted in a dummy recorded higher peak values than Mikras in real potatoes. Impact on the flat side of a tuber led to higher peak values than impact on the apical region. This could be caused by different elastic compliance of synthetic materials as well as material thickness. Running through the processing line simulator TuberLog recorded the most impact; Smart Spud recorded a low number of impacts compared to the other electronic fruits. In all experiments the least sensitive measurements were recorded using Smart Spud.

Non-destructive evaluation of apple fruit maturity on the tree.

Non-Destructive Evaluation of Apple Fruit Maturity on the Tree The evaluation of apple fruit maturity (Malus domestica Borkh.) is based on destructive analyses, analysing starch conversion, fruit flesh firmness and Brix value. Specific threshold values exist for each cultivar and according to post-harvest treatment and storage. A rapid non-destructive method to evaluate the fruit maturity could be very important to obtain more reliable results. Since miniaturised spectrometer modules were available, visible/near infrared spectroscopy has been used to build up portable spectrometer equipment. Measurements were carried in weekly intervals on three cultivars in a commercial orchard in 2003 to 2005 during the period from August to October. The fruit maturity stage was described by two non-destructive spectral indices i) the chlorophyll decrease and ii) the anthocyanins increase. Both indices demonstrated the high variability of fruit maturity stage in orchard. The characteristics of several apple cultivars could be used to evaluate the actual differences in maturity stage. The spectral indices pointed out the influence of fruit yield and of temperature on the fruit maturity. Niedestrukcyjna Ocena Stopnia Dojrzałości Jabłek Na Jabłoni Ocena stopnia dojrzałości jabłek (Malus domestiuca Borkh.) jest oparta na destrukcyjnych analizach, dotyczących przemian chemicznych skrobi, jędrności miąższu w skali Brixa. Specyficzne wartości progowe są określone dla każdej odmiany w zależności od pozbiorczego traktowania i przechowywania. Szybka, niedestrukcyjna metoda do oceny stopnia dojrzałości jabłek mogłaby być pomocna do otrzymania bardziej wiarygodnych wyników. Do konstrukcji przenośnego spektrometru wykorzystano zminimalizowane moduły spektrometryczne w oparciu o spektroskopię w zakresie widma widzialnego i bliskiej podczerwieni. Pomiary były wykonywane w odstępach tygodniowych na trzech odmianach w sadzie przemysłowym w latach 2003 - 2005, w okresie od sierpnia do października. Stopień dojrzałości owoców był określany na podstawie dwóch niedesktrukcyjnych wskaźników spektralnych: i) spadku poziomu chlorofilu ii) wzrostu poziomu antocyjanów. Obydwa wskaźniki uwidoczniły wysoką różnorodność stopnia dojrzałości owoców w sadzie. Cechy charakterystyczne kilku odmian jabłek zostały wykorzystane do oceny rzeczywistych różnic w stopniu dojrzałości owoców. Spektralne wskaźniki wyraźnie wykazały wpływ wysokości plonu i temperatury na dojrzewanie owoców.

Online Sensing the Mechanical Impacts of Real Perishables During Handling

Mechanized production techniques cause numerous mechanical impacts on perishable fruit and vegetables and, therefore frequently mechanical damage and economical losses. Currently used criteria for evaluation of the damage risk of perishable fruit and vegetables in practice are not sufficiently adapted to real produce properties. Moreover, given certification instruments for fruit and vegetable production systems do not contain methods and means suited to acquire reliable information on actual mechanical impacts. A new approach is directed to acquire data under conditions how the real produce is subject to mechanical impacts. Recently, a miniaturized impact detecting device has been developed consisting of a data transmitting part suited for implantation into perishables like fruit, potato or carrot and a portable part to receive the data in real-time. The impact detecting device has been tested to acquire data of impacts occurring during packaging of washed carrots into foodtainers. The data transmitter was implanted in real carrot, and this carrot was enabled to run together with other carrots through the packaging process. The data transmitted were recorded by using portable PC. Two types of packaging machines were included in the tests. Test results showed significant differences between the both machines, for type A about 200 impacts, and for type B about 100 impacts. But the peak values of the impacts did not significantly differ, 30 g’s (type A), and 36 g’s (type B). However, a considerable variation of both parameters occurred. The reason for the difference in the number of impacts could be the inadequate high feeding rate on packaging machine type A.

Impact characterization of agricultural products by fall trajectory simulation and measurement

Abstract Since 40 years, artificial fruits or dummies are built similar to real agricultural produce in order to measure mechanical load caused due to harvest and post-harvest handling systems. As shown by Praeger et al., 2013 the evaluation of how close these electronic fruits reflect real products impact behavior has been largely neglected during their design. The paper dealt with development of a test method for comparison of elastic characteristics of real potato tubers and of dummy materials (built based on 2 component polyurethane elastomers) falling on metal or plastic materials. Therefore, the trajectory of the produce center of the whole drop process was simulated based on measurements with a miniaturised 3-axis accelerometer inside the samples, force measurements at the impact position and videos made with a high speed camera of the fall and rebound process. A simulation model of the impact was developed and impacts were characterised by forces, coefficients of restitutions, accumulated energy and deformation features obtained by quasi- rigid body impact simulations. Exemplary impact characteristics are presented for real potatoes of different water status and artificial tuber dummies using force-deformation courses and coefficients of restitution. The testing procedure showed to be useful for the systematic design of optimised dummy materials, for instance based on polyurethane elastomers, for a highly realistic replication of impact performance of real fruit and to improve the applicability and accuracy of dummies in field measurements. The drop tests and simulations for tuber dummies and real potatoes showed a wide range of impact characteristics when falling onto steel. In general, impact forces of the currently used dummies were higher and deformations were reduced compared to those of potato tubers. One dummy tested in this study showed impact characteristics widely similar to potato tuber material.

Wirkung dynamischer Belastung auf Schwarzfleckigkeit in Kartoffeln

Am ATB wird ein schon fruher beschriebener mikrotechnischer Sensor zur Beschleunigungsmessung in landwirtschaftlichen oder gartenbaulichen Produkten wahrend des Ernte- und Nachernteprozesses [1] gemeinsam mit zwei mittelstandischen Unternehmen weiterentwickelt. Die bisherige telemetrische Datenubertragung zum Computer wird durch interne Datenerfassung ersetzt. Um den Sensor fur Schadensprognosen zu Schwarzfleckigkeit von Kartoffeln in der Praxis einzusetzen, wurden Untersuchungen uber den Zusammenhang zwischen dynamischer Belastung und Schadigung durchgefuhrt. Da der Sensor eine triaxiale Erfassung der Stosbeschleunigung ermoglicht, ist die Wirkung wiederholter Belastung in einer Richtung im Unterschied zu Belastungen an verschiedenen Stellen fur die Auswertung von besonderer Bedeutung.

Physiologische Einflüsse auf das Schneidverhalten von Radieschen

In Zeiten zunehmender Arbeitsuberlastung nimmt der Markt fur gebrauchsfertig zubereitete Frischsalate weltweit zu. Zur Herstellung dieser Produkte ist immer ein Zerschneiden notwendig. Eine niedrige Verarbeitungsqualitat vergrosert das Verderbnisrisiko und verringert die Haltbarkeit der Produkte. Eine Optimierung der Bearbeitungsverfahren kann die Verluste begrenzen. Auch physiologische Produkteigenschaften beeinflussen die Schnittqualitat in hohem Mase. Optimiertes Vorkonditionieren konnte die Produktverluste reduzieren. In diesem Beitrag wurden die Einflusse von Temperatur, Wasser- und Entwicklungszustand auf die Schnittqualitat von Radieschen naher charakterisiert.

Water Content Variations in Carrot Tissue by Hyperspectral Imaging

The objective of the work reported here was to analyze the variations in the water content of carrot during the storage by hyperspectral imaging and to determine relationship between spectral characteristic and water content reduction. Relative absorption spectrum was recorded on the tissues in the wavelength range from 900 to 1750 nm. The results show that the reduction in the water content of carrot provides with a definite increase in the absorption signal level measured by hyperspectral imaging in the range below 1400 nm wavelength. Relationship was found between the spectral parameter and storage time. Consequently, hyperspectral imaging is suitable for prediction of water content of carrots on the basis of the relationship between the spectral parameter and relative mass reduction.

Stoßbelastung von Möhren beim maschinellen Verpacken

Washed carrots are mechanically harvested, transported, graded and packed. During these handling processes they undergo intensive mechanical impact that can decrease quality and shelf life. In particular, packaging in foodtainers is one of the processes with very high mechanical impact. In order to quantify it, an impact detector was implanted directly into a single carrot to determine mechanical impact accelerations occurring during transport through the packaging machine. By analyzing the impact data, the frequency and magnitude could be measured, and critical aspects of each technical section identified. The impact data recorded can be used to reduce mechanical impacts during mechanical handling in the future.