Ulrike Praeger

Remote quality monitoring in the banana chain

Quality problems occurring during or after sea transportation of bananas in refrigerated containers are mainly caused by insufficient cooling and non-optimal atmospheric conditions, but also by the heat generated by respiration activity. Tools to measure and evaluate these effects can largely help to reduce losses along the banana supply chain. The presented green life model provides a tool to predict the effect of deviating temperature, relative humidity, and CO2 and O2 gas concentrations on the storage stability of bananas. A second thermal model allows evaluation of the cooling efficiency, the effect of changes in packaging and stowage and the amount of respiration heat from the measured temperature curves. Spontaneous ripening causes higher respiration heat and CO2 production rate. The resulting risk for creation of hot spots increases in positions in which the respiration heat exceeds the available cooling capacity. In case studies on the transport of bananas from Costa Rica to Europe, we validated the models and showed how they can be applied to generate automated warning messages for containers with reduced banana green life or with temperature problems and also for remote monitoring of the ripening process inside the container.

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.

Aqueous chlorine dioxide treatment of horticultural produce: Effects on microbial safety and produce quality–A review

ABSTRACT Microbial load on fresh fruit and vegetables causes decay and losses after harvest and may lead to foodborne illness in case of contamination with human pathogens on raw consumed produces. Washing with tap water only marginally reduces microorganisms attached to produce surfaces. Chlorine is widely used for decontamination on fresh horticultural produces. However, due to harmful by-products and the questionable efficacy it has become increasingly challenged. During the last 20 years, the interest to study ClO2 treatments as an alternative sanitation agent for industrially prepared fresh produce has largely increased. For a wide range of commodities, the application of gaseous ClO2 has meanwhile been investigated. In addition, since several years, the interest in aqueous ClO2 treatments has further risen because of the better manageability in postharvest processing lines compared to gaseous application. This article critically evaluated the effects of postharvest application of aqueous ClO2, either alone or in combination with other treatments, on microbial loads for various horticultural produces. In laboratory investigations, application of aqueous ClO2 at concentrations between 3 and 100 ppm effectively reduced counts of natural or inoculated microorganisms (bacteria, yeasts, and mold) in the range of 1 and 5 log. However, various effects of ClO2 treatments on produce quality have been described. These mainly comprise implication on sensory and visual attributes. In this context, there is increasing focus on the potential impacts of aqueous ClO2 on relevant nutritional components of produces such as organic acids or phenolic substances.

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.

Measuring Device for Air Speed in Macroporous Media and Its Application Inside Apple Storage Bins

In cold storage facilities of fruit and vegetables, airflow is necessary for heat removal. The design of storage facilities influences the air speed in the surrounding of the product. Therefore, knowledge about airflow next to the product is important to plan the layout of cold stores adapted to the requirements of the products. A new sensing device (ASL, Air speed logger) is developed for omnidirectional measurement of air speed between fruit or vegetables inside storage bins or in bulk. It consists of four interconnected plastic spheres with 80 mm diameter each, adapted to the size of apple fruit. In the free space between the spheres, silicon diodes are fixed for the airflow measurement based on a calorimetric principle. Battery and data logger are mounted inside the spheres. The device is calibrated in a wind tunnel in a measuring range of 0–1.3 m/s. Air speed measurements in fruit bulks on laboratory scale and in an industrial fruit store show air speeds in gaps between fruit with high stability at different airflow levels. Several devices can be placed between stored products for determination of the air speed distribution inside bulks or bin stacks in a storage room.

TuberLog und Co. – Messverhalten künstlicher Früchte im Labor

Kunstliche Fruchte werden eingesetzt, um Stosbelastungen bei der Ernte und Aufbereitung von empfindlichen Produkten zu detektieren. Fur die realistische Erfassung der Stosbeschleunigung sollten die Messkorper den Produkten moglichst ahnlich sein. Hier werden Ergebnisse von Fallversuchen und von Messungen in einer Laborforderstrecke mit verschiedenen elektronischen Fruchten sowie eines in eine Kartoffel implantierten Sensors vorgestellt. Die Messsysteme TuberLog, IRD und Mikras sind nach dieser Untersuchung in ahnlicher Weise geeignet, kritische Stellen in einem Aufbereitungsprozess zu detektieren. Beim Aufprall auf feste Unterlagen wird die Stosintensitat durch die verwendeten Messkorper aus Kunststoff im Vergleich zur Messung im echten Produkt uberbewertet.

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.