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End date: 2021 × Start date: 2020 × DDC: 630 × Type: Text × Subject: Fruit quality ×

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    Optimization of short-term hot-water treatment of apples for fruit salad production by non-invasive chlorophyll-fluorescence imaging
    (Basel : MDPI AG, 2020) Herppich, Werner B.; Maggioni, Marco; Huyskens-Keil, Susanne; Kabelitz, Tina; Hassenberg, Karin
    For fresh ]cut salad production, hot-water treatment (HWT) needs optimization in terms of temperature and duration to guarantee a gentle and non-stressing processing to fully retain product quality besides an effective sanitation. One major initial target of heat treatment is photosynthesis, making it a suitable and sensitive marker for HWT effects. Chlorophyll fluorescence imaging (CFI) is a rapid and non ]invasive tool to evaluate respective plant responses. Following practical applications in fruit salad production, apples of colored and of green ]ripe cultivars ( eBraeburn f, eFuji f, eGreenstar f, eGranny Smith f), obtained from a local fruit salad producer, were hot ]water treated from 44 to 70 °C for 30 to 300 s. One day after HWT and after 7 days of storage at 4 °C, CFI and remission spectroscopy were applied to evaluating temperature effects on photosynthetic activity, on contents of fruit pigments (chlorophylls, anthocyanins), and on various relevant quality parameters of intact apples. In eBraeburn f apples, short ]term HWT at °C for 30 to 120 s avoided any heat injuries and quality losses. The samples of the other three cultivars turned out to be less sensitive and may be short-term heat-treated at temperatures of up to 60 °C for the same time. CFI proved to be a rapid, sensitive, and effective tool for process optimization of apples, closely reflecting the cultivar-or batch-specificity of heat effects on produce photosynthesis. © 2020 by the authors.
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    Thinning efficacy of metamitron on young 'RoHo 3615' (Evelina®) apple
    (Amsterdam [u.a.] : Elsevier Science, 2020) Penzel, Martin; Kröling, Christian
    To achieve a high quantity of premium class fruit, chemical thinning is an important component of crop load management in apples. For this purpose, the triazine-type photosynthetic inhibitor metamitron was registered for fruit thinning in Germany. Frequent studies demonstrated consistent thinning effects of metamitron on trees of different apple and pear cultivars. In the present study, the efficacy of metamitron applied at a low concentration (165 g ha−1) was investigated in 2016 and 2017 on young 'RoHo3615' apple trees, planted in 2014. The highest fruit set reduction was achieved when metamitron was applied twice. Single application, in contrast, led to variable results and pointed out the strong dependence of the thinning efficacy of metamitron on favourable weather conditions. Adding citric acid or the growth regulator prohexadione-Ca in combination with ammonium sulphate did not affect the thinning efficacy of metamitron. The fruit quality was high in any treatment and no effects of thinning treatment on fruit colouration or percentage of skin russeting were observed. Consequently, metamitron is an effective fruit thinning agent for young apple trees, which can be additionally used in combination with the mentioned substances, while maintaining a high fruit quality