Non-enzymatic degradation of flavan-3-ols by ascorbic acid- and sugar-derived aldehydes during storage of apple juices and concentrates produced with the innovative spiral filter press.

Potentially health-promoting concentrations of flavan-3-ols were previously shown to be retained in apple juices produced with the emerging spiral filter press. Due to the novelty of this technology, the factors governing the stability of flavan-3-ol-rich apple juices have only scarcely been studied. Therefore, we produced flavan-3-ol-rich apple juices and concentrates (16, 40, 70 °Brix) supplemented with ascorbic acid (0.0, 0.2, 1.0 g/L) according to common practice. Flavan-3-ols (DP1-7) and twelve flavan-3-ol reaction products were comprehensively characterized and monitored during storage for 16 weeks at 20 and 37 °C, employing RP-UHPLC- and HILIC-DAD-ESI(-)-QTOF-HR-MS/MS. Flavan-3-ol degradation followed a second-order reaction kinetic, being up to 3.5-times faster in concentrates (70 °Brix) than in single strength juices (16 °Brix). Furthermore, they diminished substantially faster compared to other phenolic compounds. For instance, after 16-weeks at 20 °C, the maximum loss of flavan-3-ols (-70 %) was greater than those of hydroxycinnamic acids (-18 %) and dihydrochalcones (-12 %). We observed that flavan-3-ols formed adducts with sugars and other carbonyls, such as 5-(hydroxymethyl)furfural and the ascorbic acid-derived L-xylosone. Increased degradation rates correlated particularly with increased furan aldehyde levels as found in concentrates stored at elevated temperatures. These insights could be used for optimizing production, distribution, and storage of flavan-3-ol-rich apple juices and other foods and beverages.

Analytical characterization of flavan-3-ol-rich apple juices produced with the innovative spiral filter press technology.

The retention of flavan-3-ols and other phenolic compounds during apple juice production at pilot plant scale (200 kg, cv. Boskoop) was investigated. An oxygen-excluding spiral filter press and a conventional decanter were used with and without pectinase mash treatment. Phenolic compounds were comprehensively identified and quantitated by RP-UHPLC and HILIC, both coupled to DAD-FLD and DAD-ESI(-)-QTOF-HR-MS/MS. These techniques combined with using a NIST cocoa flavan-3-ol standard allowed for the first time an individual quantification of flavan-3-ol fractions (DP 1-7) in apple juices. Spiral filter-pressed juices were exposed to less oxidation and exhibited four times higher total phenolic compound levels than decanter-made juices (1016 vs. 262 mg/L). Apple juices derived from pectinase-treated mashes had lower total phenolic compound levels than their non-treated counterparts. However, those made by spiral filter press still retained significantly higher concentrations (780 vs. 104 mg/L). Flavan-3-ols were especially well retained by spiral filter press processing, reaching unprecedentedly high concentrations of up to 713 mg/L. A 280 mL serving of non-treated spiral filter-pressed juice would therefore suffice to provide the daily intake of 200 mg flavan-3-ols, equaling the dose of cocoa flavan-3-ols associated with an authorized European health claim for healthy blood flow.

Additive and synergistic antifungal effects of copper and phenolic extracts from grape cane and apples.

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.

Comparative Evaluation of Juices from Red-Fleshed Apples after Production with Different Dejuicing Systems and Subsequent Storage.

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.