Suchergebnisse

Systeme zum Management von Lebensmittelqualität und -sicherheit stellen eine der zentralen Herausforderungen für die europäische Agri-Food Chain dar. Die BSE-Krise und die damit einhergehende politische Agrarwende sowie eine gestiegene Nachfrage der Konsumenten nach Informationen über die Produktion und Qualität von Lebensmitteln haben dazu geführt, dass Qualitätssicherungssysteme in den zurückliegenden Jahren zunehmend an Relevanz gewonnen haben. Wesentliche Teile der Wertschöpfungskette sind bereits nach Standards wie QS (QS Qualität und Sicherheit GmbH), IFS (International Food Standard) oder GLOBALGAP (Global Partnership for Good Agricultural Practice) zertifiziert.Im Kontrast zu dieser rasanten Entwicklung der europäischen Zertifizierungssysteme steht jedoch die noch vernachlässigte Auseinandersetzung mit der Frage, ob diese Form der Qualitätssicherung ihre Aufgaben überhaupt zuverlässig erfüllen kann. Auch nach dem Aufbau der Systeme ist es bekanntlich weiterhin zu Qualitätsskandalen (z. B. Gammelfleisch oder Dioxin in Futtermitteln) gekommen, die hinreichenden Anlass geben, die Kontrollvalidität und -reliabilität kritisch zu hinterfragen. Darüber hinaus sind die primären Destinatare der Qualitätssicherungsstandards (z. B. Landwirte oder die verarbeitenden Unternehmen) nicht immer zufrieden mit den Systemen, so dass Akzeptanzprobleme wahrscheinlich werden. Akzeptanz und positive Motivation sind jedoch wichtige Voraussetzungen für Qualitätssicherungsstandards, denn ein System, das als bürokratische Last wahrgenommen wird, führt langfristig nicht zu Qualitätsverbesserungen, da intrinsische Motivation verdrängt wird.Die vorliegende kumulative Dissertation greift diese Problemfelder und weitere Fragestellungen aus theoretischer und empirischer Perspektive auf. Insgesamt umfasst die Arbeit fünfzehn publizierte bzw. bei Zeitschriften eingereichte Beiträge, die vier inhaltlichen Schwerpunkten zugeordnet sind: Status-Quo-Analysen zur Qualitätssicherung in der Agri-Food Chain, Analysen zur Akzeptanz und Bewertung von Qualitätssicherungssystemen, Analysen zur Verbesserung der Prüfungsqualität von Qualitätssicherungssystemen und Exkurse. ; Food quality and security management systems represent one of the major challenges for the European agri-food chain. The BSE crisis and the agricultural chain ( Agrarwende ) as well as an increased consumer demand for information about production and quality of food led to the fact that quality assurance systems have become increasingly relevant for the agribusiness in recent years. Substantial parts of the supply chain are already certified against standards such as QS (QS Qualität und Sicherheit GmbH), IFS (International Food Standard) or GLOBALGAP (Global Partnership for Good Agricultural Practice).In contrast to this rapid diffusion, the debate on the question of whether this type of quality assurance can reliably perform its tasks has so far largely been neglected. In Germany, there have been several quality scandals, even after the set-up of certification schemes (spoiled meat, dioxin in animal feed). Therefore, it seems reasonable to critically review the validity and reliability of audits. In addition, the main parties involved in quality assurance systems (e.g. farmers or processing companies) have not always been satisfied with the standards, so that problems of acceptance become probable. However, acceptance and positive motivation are important because a scheme which is recognized as a bureaucratic burden will not lead to quality improvements.The present cumulative thesis takes up these problem fields and further questions from a theoretical as well as an empirical perspective. Altogether the work contains fifteen contributions which are either already published in or submitted to journals. The emphasis is put on four fields: status quo analyses for the quality assurance in the agri-food chain, analyses of the acceptance and evaluation of quality assurance systems, analyses for the improvement of the audit quality of quality assurance systems and excursions.

A highly sensitive and rapid food-screening test based on disposable screen-printed biosensors was developed, which is suitable for monitoring infant food. The exposure of infants and children to neurotoxic organophosphates and carbamates is of particular concern because of their higher susceptibility to adverse effects. The European Union has therefore set a very low limit for pesticides in infant food which must not contain concentrations exceeding 10 μg/kg for any given pesticide. The maximum residue limit (MRL) has been set to be near the determination threshold that is typically achieved for pesticides with traditional analytical methods. The biosensor method could detect levels lower than 5 μg/kg and thus clearly fulfills the demands of the EU. To substantiate these measurements, recovery rates were determined and amounted on average to 104 % in food. Matrix effects were eliminated by the introduction of a special electrode treatment. The test was compared with two traditional pesticide multiresidue analysis methods (GC/MS, LC/MS) using 26 fruit and vegetable samples from local markets and 23 samples of processed infant food from Germany, Spain, Poland and the USA. Three infant food samples exceeded the MRL of 10 μg/kg when analyzed by either biosensor test or multiresidue methods.

Subjective tinnitus is the conscious perception of sound in the absence of any acoustic source. The literature suggests various tinnitus mechanisms, most of which invoke changes in spontaneous firing rates of central auditory neurons resulting from modification of neural gain. Here, we present an alternative model based on evidence that tinnitus is: (1) rare in people who are congenitally deaf, (2) common in people with acquired deafness, and (3) potentially suppressed by active cochlear implants used for hearing restoration. We propose that tinnitus can only develop after fast auditory fiber activity has stimulated the synapse formation between fast-spiking parvalbumin positive (PV+) interneurons and projecting neurons in the ascending auditory path and coactivated frontostriatal networks after hearing onset. Thereafter, fast auditory fiber activity promotes feedforward and feedback inhibition mediated by PV+ interneuron activity in auditory-specific circuits. This inhibitory network enables enhanced stimulus resolution, attention-driven contrast improvement, and augmentation of auditory responses in central auditory pathways (neural gain) after damage of slow auditory fibers. When fast auditory fiber activity is lost, tonic PV+ interneuron activity is diminished, resulting in the prolonged response latencies, sudden hyperexcitability, enhanced cortical synchrony, elevated spontaneous y oscillations, and impaired attention/stress-control that have been described in previous tinnitus models. Moreover, because fast processing is gained through sensory experience, tinnitus would not exist in congenital deafness. Electrical cochlear stimulation may have the potential to reestablish tonic inhibitory networks and thus suppress tinnitus. The proposed framework unites many ideas of tinnitus pathophysiology and may catalyze cooperative efforts to develop tinnitus therapies. ; German Research Foundation (DFG) DFG-Kni-316-4-1 SPP16-08 DFG Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1161155 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) BASAL FB008 ICM P09-015F European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant 764604 722046 National Institute for Health Research (NIHR)