Measurement of Water Vapor Condensation on Apple Surfaces during Controlled Atmosphere Storage

Apples 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

Chlordioxid zur Reduktion von humanpathogenen Mikroorganismen bei der Salatwäsche

Der 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.During recent years, the consumption of prepackaged readyto- eat salads has strongly increased. To facilitate the production of microbiological safe fresh-cut products, the potential of chlorine dioxide for decontamination of iceberg lettuce during washing and its effects on external and internal quality parameters of the produce were investigated. ClO2 application results in 5 to 6 log reduction of microorganisms in the washing water, depending on its chemical oxygen demand (COD). Colour parameters and vitamin C content of leaves were not affected by chlorine dioxide washing. Therefore, chlorine dioxide is an appropriate sanitizer to minimize human pathogens in lettuce washing water

TuberLog und Co. – Messverhalten künstlicher Früchte im Labor

Künstliche 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.Artificial fruits are used for measuring mechanical load in order to detect critical points in harvest and following processing lines. For realistic measurement of impact acceleration the measuring devices should have similar physical properties as the real products. Results are presented of drop experiments and measurements in a laboratory processing line. Therefore, different acceleration sensors with plastic cover and a sensor which is implanted in a potato tuber were used. The measuring systems TuberLog, IRD and Mikras are in a similar manner appropriate for detection of critical points in a processing line according to this study. Measuring with synthetic devices results in an overestimation of impacts onto firm material compared to measuring in a real product

Effect of Chlorine Dioxide Treatment on Human Pathogens on Iceberg Lettuce

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

Chlordioxid zur Reduktion von humanpathogenen Mikroorganismen bei der Salatwäsche

During recent years, the consumption of prepackaged ready-to-eat salads has strongly increased. To facilitate the production of microbiological safe fresh-cut products, the potential of chlorine dioxide for decontamination of iceberg lettuce during washing and its effects on external and internal quality parameters of the produce were investigated. ClO2 application results in 5 to 6 log reduction of microorganisms in the washing water, depending on its chemical oxygen demand (COD). Colour parameters and vitamin C content of leaves were not affected by chlorine dioxide washing. Therefore, chlorine dioxide is an appropriate sanitizer to minimize human pathogens in lettuce washing water

Effect of Chlorine Dioxide Treatment on Human Pathogens on Iceberg Lettuce

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 (&lt;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

Measurement of Water Vapor Condensation on Apple Surfaces during Controlled Atmosphere Storage

Apples are stored at temperatures close to 0 &deg;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

Measurement of Water Vapor Condensation on Apple Surfaces during Controlled Atmosphere Storage

Apples 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

Comparison of Two Impact Detecting Devices to Measure Mechanical Load on Potatoes

Mechanized production techniques cause numerous mechanical loads on perishable fruit and vegetables and, therefore, frequently mechanical damage and economical losses. Laboratory tests were conducted to measure and to compare two impact detecting devices, the artificial fruit PMS-60 measuring pressure and a data transmitting sensor for implantation into perishable fruit measuring acceleration. Both devices can be used to detect mechanical load in potato processing lines. A specific test device with three conveyor belts running in circuit at four velocities of 0.2, 0.4, 0.55 and 0.65 m/s and with several free fall steps was used for the experiments. The data transmitter was implanted in a real potato. This potato was run together with PMS-60 and other potatoes through the conveyor belt circuit. Results show significant differences between mechanical loads recorded with PMS-60 and the implanted sensor. Data transmitting sensor recorded higher average load values (51.81, 53.28, 54.94 and 54.03 N,s at belt velocities of 0.2, 0.4, 0.55 and 0.65 m/s respectively) than PMS-60 (41.84, 42.99,43.34 and 42.39 N,s).The results will be discusse

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