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Chlorophyllfluoreszenz als Werkzeug für die DCA-Lagerung von Äpfeln (Malus x domestica BORKH.)
(2024)
Äpfel besitzen mehrere Allergene, die beim Essen innerhalb von 5–10 min zu Symptomen im Mundbereich führen – und deshalb von Apfelallergikern nicht gegessen werden können. In Deutschland haben rund 7,5 Mio. Menschen spezifische Antikörper gegen das Hauptallergen (Mal d 1) in Äpfeln entwickelt und sind damit sensibilisiert. Mindestens 3,5 Mio. von ihnen entwickeln die teilweise erheblichen allergischen Symptome als Ausdruck eines Oralen Allergie-Syndroms. Es gibt bisher keine medikamentöse Therapie gegen diese Allergie.
Apfelallergiker können daher nur auf Äpfel ganz verzichten, oder vorher erhitzte Äpfel essen oder Sorten suchen, die wenig Allergene enthalten und deshalb als allergikerfreundliche Apfelsorten bezeichnet werden können.
Alleinige Bestimmungen von Allergenen im Labor können nicht voraussagen, ob ein Apfel ohne allergische Symptome von Apfelallergikern gegessen werden kann; dazu bedarf es klinischer Prüfungen.
Wir beschreiben eine standardisierte klinische, orale Provokationstestung, die zur Charakterisierung eines allergenarmen, allergikerfreundlichen Apfels bzw. Apfelsorte benutzt werden kann.. Die Ergebnisse solcher mindestens dreijährigen Tests können zur Verleihung des ECARF-Siegels für allergikerfreundliche Produkte genutzt werden.
Currently, only non-imaging chlorophyll fluorescence measurements are used to identify the Lower Oxygen Limit (LOL) in Dynamic Controlled Atmosphere - Chlorophyll Fluorescence (DCA-CF) storage. The disadvantage of non-imaging fluorescence is that no statement can be made about the spatial heterogeneity of the sample. In contrast, chlorophyll fluorescence imaging can detect spatial heterogeneity of photosynthetic activity and has been established in research for some decades because the information benefit is higher. In this study, the chlorophyll fluorescence (Fo, Fm, Fv, Fv/Fm) of apples (Malus x domestica, BORKH.) was measured with a fluorescence imaging system in situ during storage. Intact apples of ‘Braeburn’ and ‘Golden Delicious’ were stored under low-oxygen stress conditions (< 1 kPa). The metabolic shift from aerobic to fermentative metabolism was made visible with the chlorophyll fluorescence imaging and was spatially localized on the sample. Furthermore, a method was developed to identify the LOL based on the chlorophyll fluorescence imaging combined with the histogram division method. This method considers the heterogeneity of the fluorescence and bundles the measured Fo data as histograms. Our results showed that the fluorescence imaging combined with the histogram division method can be a powerful tool for identifying the LOL.
Dynamic Controlled Atmosphere-Chlorophyll Fluorescence storage (DCA-CF) uses a fluorescence-based measurement method to detect fermentation in apples (Malus × domestica BORKH.) caused by low-oxygen levels at an early stage. In recent years, it has been observed that individual apples of the same variety and origin can exhibit different fermentation behavior when stored under completely identical conditions. The causes of the different fermentation behavior must be found in order to be able to use DCA storage optimally. This study aimed to find the causes of the different fermentation behaviors of individual apples. Our results show that fruit ripeness can affect the lower oxygen limit (LOL), especially immediately after harvest, when the starch degradation in the fruit is not yet complete. A significant increase in the LOL was observed in ‘Elstar’ (2020: 0.3 kPa, 0.6 kPa, 0.9 kPa; 2021: 0.3 kPa, 0.4 kPa, 0.6 kPa). ‘Braeburn’ also exhibited this behavior regarding the LOL at a lower level. The LOL could not be identified for some of the fruit (varying from 12.5% to 41.7% of the examined apples) previously stored in Ultra Low Oxygen (ULO) storage for 4 months. Also, the chlorophyll content in the apple skin influences the fluorescence measurement method. Within 2 weeks, the chlorophyll content in the apple skin was halved. If the chlorophyll content drops, the reliability of the fluorescence measurement also decreases. It turned out that apples with an Fv/Fm < 0.7 were unsuitable for valid LOL identification.