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Author: Herppich, Werner B. × Subject: Fruit quality ×

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Now showing 1 - 2 of 2
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    Evaluating spatially resolved influence of soil and tree water status on quality of European plum grown in semi-humid climate
    (Lausanne : Frontiers Media, 2017) Käthner, Jana; Ben-Gal, Alon; Gebbers, Robin; Peeters, Aviva; Herppich, Werner B.; Zude-Sasse, Manuela
    In orchards, the variations of fruit quality and its determinants are crucial for resource effective measures. In the present study, a drip-irrigated plum production (Prunus domestica L. “Tophit plus”/Wavit) located in a semi-humid climate was studied. Analysis of the apparent electrical conductivity (ECa) of soil showed spatial patterns of sand lenses in the orchard. Water status of sample trees was measured instantaneously by means of leaf water potential, Ψleaf [MPa], and for all trees by thermal imaging of canopies and calculation of the crop water stress index (CWSI). Methods for determining CWSI were evaluated. A CWSI approach calculating canopy and reference temperatures from the histogram of pixels from each image itself was found to suit the experimental conditions. Soil ECa showed no correlation with specific leaf area ratio and cumulative water use efficiency (WUEc) derived from the crop load. The fruit quality, however, was influenced by physiological drought stress in trees with high crop load and, resulting (too) high WUEc, when fruit driven water demand was not met. As indicated by analysis of variance, neither ECa nor the instantaneous CWSI could be used as predictors of fruit quality, while the interaction of CWSI and WUEc did succeed in indicating significant differences. Consequently, both WUEc and CWSI should be integrated in irrigation scheduling for positive impact on 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.