In this work, two vintages (2019 and 2020) of red-fleshed ‘Weirouge’ apples were processed with the innovative spiral filter press technology to investigate juice production in an oxygen-reduced atmosphere. After pressing, a more brilliant red color and appreciably higher amounts of oxidation-sensitive constituents (ascorbic acid, anthocyanins, and colorless (poly)phenols) were seen in spiral filter pressed juices compared to those produced with conventional systems (horizontal filter press and decanter). In a subsequent stability study (24 weeks storage at 4, 20, and 37 °C), the color and phenolic compounds were monitored and differences in the juices produced with the different pressing-systems were widely maintained during the storage period. The analyses of the anthocyanins and colorless (poly)phenols were conducted by UHPLC-DAD-ESI-QTOF-HR-MS/MS and UHPLC-DAD. The spiral filter press emerged as a promising technology for the production of juices with a more attractive color and a better retention of oxidation-sensitive constituents during processing and storage compared to conventional juices.
Background Organic viticulture seeks sustainable alternatives for eco‐toxic copper fungicides to control downy mildew caused by Plasmopara viticola. (Poly)phenol‐rich extracts of agricultural byproducts are known to possess antifungal activity, but high production costs often limit their actual implementation. Results We developed and produced novel ligninsulfonate‐based grape cane extract (GCE) formulations and an apple extract on a pilot plant scale, including a detailed (poly)phenol characterization by high‐performance liquid chromatography photodiode array mass spectrometry (HPLC‐PDA‐MS). Our GCE formulations alone reduced downy mildew disease severity in greenhouse trials by 29%–69% in a dose‐dependent manner, whereas a standard application of the copper‐based agent alone reached ~56%. When applied together, disease severity was diminished by 78%–92%, revealing a synergistic effect that depended on the mixture ratio. Combining GCE formulations with the apple extract, additive effects were found (80% disease severity reduction). Conclusion The studied plant extracts are proposed to both substitute for and synergistically reinforce copper fungicides in grapevine downy mildew control. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Blackcurrant juices were produced with an oxygen-excluding spiral filter press and two conventional pressing systems exerting common oxygen exposure at pilot plant scale (200 kg) in technological duplicate in two subsequent years (n = 4). In contrast to findings on previously studied fruits, contents of total and individual anthocyanins were not significantly higher after spiral filter (1636–1872 mg/L) than after conventional pressing (1529–2083 mg/L). During storage for 52 weeks at 4, 20 and 37 °C, anthocyanin levels depended strongly on storage temperature, but not on the used pressing system (conventional vs. oxygen-reduced). Other juice quality parameters like ascorbic acid behaved likewise. Furthermore, a D-optimal design of experiments was used to study the influence and interactions of the factors oxygen, ascorbic acid, sugar and pH value on anthocyanin levels during a heat treatment in a model solution made with preparatively isolated blackcurrant anthocyanins. In agreement with our production trials at pilot plant scale, oxygen levels were only marginally important for the rate of anthocyanin degradation, but the influence of sugar content, ascorbic acid content and pH value was highly relevant as discussed in this report.
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