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- ItemChlordioxid zur Reduktion von humanpathogenen Mikroorganismen bei der Salatwäsche(Darmstadt : KTBL, 2014) Hassenberg, Karin; Herppich, Werner B.; Praeger, UlrikeDer Markt für abgepackte verzehrfertige Frischsalate ist in den vergangenen Jahren stark gewachsen. Für die Herstellung von mikrobiologisch unbedenklichen Produkten wurde der Zusatz von Chlordioxid (ClO2) zum Waschwasser auf sein Potenzial zur Minimierung relevanter humanpathogener Mikroorganismen getestet. Dabei wurden auch wichtige Parameter der Produktqualität, wie z. B. Farbe und Inhaltsstoffe, berücksichtigt. Eine ClO2-Behandlung ermöglicht es, die Konzentration von Mikroorganismen im Waschwasser um 5 bis 6 log-Einheiten zu reduzieren, abhängig vom chemischen Sauerstoffbedarf (CSB-Wert). Farbe und Vitamin-C-Gehalt der Salatblätter werden von der Behandlung nicht beeinflusst. Demnach ist ClO2 zur Hygienisierung von Salatwaschwasser geeignet.
- ItemTuberLog und Co. – Messverhalten künstlicher Früchte im Labor(Darmstadt : KTBL, 2013) Praeger, Ulrike; Surdilovic, Jelena; Geyer, MartinKünstliche Früchte werden eingesetzt, um Stoßbelastungen bei der Ernte und Aufbereitung von empfindlichen Produkten zu detektieren. Für die realistische Erfassung der Stoßbeschleunigung sollten die Messkörper den Produkten möglichst ähnlich sein. Hier werden Ergebnisse von Fallversuchen und von Messungen in einer Laborförderstrecke mit verschiedenen elektronischen Früchten sowie eines in eine Kartoffel implantierten Sensors vorgestellt. Die Messsysteme TuberLog, IRD und Mikras sind nach dieser Untersuchung in ähnlicher Weise geeignet, kritische Stellen in einem Aufbereitungsprozess zu detektieren. Beim Aufprall auf feste Unterlagen wird die Stoßintensität durch die verwendeten Messkörper aus Kunststoff im Vergleich zur Messung im echten Produkt überbewertet.
- ItemEffect of Chlorine Dioxide Treatment on Human Pathogens on Iceberg Lettuce(Basel : MDPI AG, 2021) Hassenberg, Karin; Praeger, Ulrike; Herppich, Werner B.In the vegetable processing industry, the application of chlorine dioxide (ClO2) as a disinfectant solved in washing water to eliminate undesirable microorganisms harmful to consumers’ health and the shelf life of produce has been discussed for years. The disinfection efficacy depends on various factors, e.g., the location of microorganisms and the organic load of the washing water. The present study analyzed the sanitation efficacy of various concentrations of water-solved ClO2 (cClO2: 20 and 30 mg L−1) on Escherichia coli (1.1 × 104 cfu mL−1), Salmonella enterica (2.0 × 104 cfu mL−1) and Listeria monocytogenes (1.7 × 105 cfu mL−1) loads, located on the leaf surface of iceberg lettuce assigned for fresh-cut salads. In addition, it examined the potential of ClO2 to prevent the cross-contamination of these microbes in lettuce washing water containing a chemical oxygen demand (COD) content of 350 mg L−1 after practice-relevant washing times of 1 and 2 min. On iceberg leaves, washing with 30 mg L−1 ClO2 pronouncedly (1 log) reduced loads of E. coli and S. enterica, while it only insignificantly (<0.5 × log) diminished the loads of L. monocytogenes, irrespective of the ClO2 concentration used. Although the sanitation efficacy of ClO2 washing was only limited, the addition of ClO2 to the washing water avoided cross-contamination even at high organic loads. Thus, the application of ClO2 to the lettuce washing water can improve product quality and consumer safety.
- ItemMeasurement of Water Vapor Condensation on Apple Surfaces during Controlled Atmosphere Storage(Basel : MDPI, 2023) Linke, Manfred; Praeger, Ulrike; Neuwald, Daniel A.; Geyer, MartinApples are stored at temperatures close to 0 °C and high relative humidity (up to 95%) under controlled atmosphere conditions. Under these conditions, the cyclic operation of the refrigeration machine and the associated temperature fluctuations can lead to localized undershoots of the dew point on fruit surfaces. The primary question for the present study was to prove that such condensation processes can be measured under practical conditions during apple storage. Using the example of a measuring point in the upper apple layer of a large bin in the supply air area, this evidence was provided. Using two independent measuring methods, a wetness sensor attached to the apple surface and determination of climatic conditions near the fruit, the phases of condensation, namely active condensation and evaporation, were measured over three weeks as a function of the operating time of the cooling system components (refrigeration machine, fans, defrosting regime). The system for measurement and continuous data acquisition in the case of an airtight CA-storage room is presented and the influence of the operation of the cooling system components in relation to condensation phenomena was evaluated. Depending on the set point specifications for ventilation and defrost control, condensed water was present on the apple surface between 33.4% and 100% of the duration of the varying cooling/re-warming cycles.
- ItemMeasuring device for air speed in macroporous media and its application inside apple storage bins(Basel : MDPI, 2018) Geyer, Martin; Praeger, Ulrike; Truppel, Ingo; Scaar, Holger; Neuwald, Daniel A.; Jedermann, Reiner; Gottschalk, KlausIn 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.
- ItemComparison of electronic fruits for impact detection on a laboratory scale(Basel : MDPI, 2013) Praeger, Ulrike; Surdilovic, Jelena; Truppel, Ingo; Herold, Bernd; Geyer, MartinMechanical 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.