In situ Creation of the Natural Phenolic Aromas of Beer: A Pulsed Electric Field Applied to Wort-Enriched Flax Seeds

To fine tune the production of phenolic aromas in beer, a pulsed electric field (PEF) was applied to beer wort, which was enriched with flax seeds. The choice of flax seeds as a source of FA is based on its high content of ferulic precursors and their intrinsic nutritional value. PEF was applied to ground flax seeds, with and without beta glycosidase. Fermentation was carried out with Saccharomyces and non-Saccharomyces yeast strains. Moreover, 4-vinylguaiacol (4-VG), a flavor highly active derived from volatile phenol, was produced by decarboxylation of ferulic acid (FA), or its precursor and flavor-inactive (4-hydroxy-3-methoxycinnamic acid). All yeast strains could metabolize FA into 4-VG, using the pure compound in the synthetic medium or in flax seeds, with the best quantity produced by Saccharomyces cerevisiae as a precursor. The method yields 4-VG production efficiencies up to 120% (mgL−1). Experimental treatment conditions were conducted with E= 1 kV/cm, total time treatment 15 min (peak time ti = 1 μs, pause time tp = 1 ms, Total pulses 9003). Treatment efficacy is independent of the fermentation yeast. © Copyright © 2020 Tsapou, Ntourtoglou, Drosou, Tataridis, Dourtoglou, Lalas and Dourtoglou

Determination of 1-aminocyclopropane-1-carboxylic acid and its structural analogue by liquid chromatography and ion spray tandem mass spectrometry

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Extraction of volatile aroma compounds from toasted oak wood using pulsed electric field

The effect of pulsed electric field (PEF) on the extraction of volatile compounds from toasted oak wood chips immersed in various aqueous ethanol solutions (5%, 12%, 50%, and 70% vol/vol) was determined by Gas chromatography/mass spectrometry (GC/MS) after ultrasound-assisted extraction. PEF treatment showed the highest impact in the 5% solution, increasing vanillin, syringaldehyde, oak lactone (cis- and trans-), and furfural by 75%, 371%, 13%, and 50%, respectively. PEF was also tested on Agiorgitiko red wine and on malt and wine distillates. In wine distillate, 4-vinylguaiacol was also detected. For red wine, a PEF of 1.2 kV/cm increased the efficiency of extraction of wood aroma compounds from 5% to 200%. Differences in the extracted volatile compound concentrations between the control and PEF-treated samples were also observed in the malt and wine distillates. The sensory evaluation showed that the PEF-treated malt was similar to an aged whiskey, having nuances of toasted oak. Practical applications: This work was done as a preliminary investigation for our on-going research into the application of PEF technique for the extraction of aromatic compounds from oak wood, and the acceleration of both wine and malt distillate aging. The findings suggest that PEF could be introduced in wine, brandy, and whiskey industry as a novel technology for the acceleration of the aging process. © 2021 Wiley Periodicals LLC

Pulsed electric field: A “green” extraction technology for biomolecular products from glycerol with fermentation of non-Saccharomyces yeasts

Glycerol is the main organic by-product of the biodiesel industry and it can be a source of carbon for fermentations or a substrate for biotransformations. This work investigates a process that uses pulsed electric field (PEF) to enhance polyol and propanediols extraction from a glycerol/glucose fermentation broth. Three different commercial, non-Saccharomyces strains, Torulaspora delbrueckii Prelude (Hansen), Torulaspora delbrueckii Biodiva 291 (Lallemand) and Metschnikowia pulcherrima (Lallemand) were studied. The results revealed that PEF had a positive impact on the extraction of polyols ranging from 12 to 191%, independently of fermentation conditions. Torulaspora delbrueckii Biodiva 291 (Lallemand) was found to be more efficient at pH 7.1. An optimized chromatography-based method for the qualitative and quantitative determination of the formed products evaluated. The experiments were carried out either in flasks or in a bioreactor. Copyright © 2022 Tsapou, Ntourtoglou, Drosou, Tataridis, Lalas and Dourtoglou

Pulsed Electric Field Extraction of α and β-Acids From Pellets of Humulus lupulus (Hop)

This paper investigates the process of extracting hop pellets (hops) utilizing the pulsed electric field (PEF) technique and the contrasting effects of the technique between two distinct hop varieties (one bitter and one aromatic). The effect of PEF on the extraction was evaluated by measuring the concentration of α-acids and β-acids (humulones and lupulones). Regarding the aromatic character, the hop’s volatile caryophyllene, humulene and β-myrcene were analyzed both with and without employing the PEF treatment. In order to analyze the acids and the volatile fraction, the analytical method of UV–vis spectrophotometry was applied followed by gas chromatography coupled with mass spectrometry. For the second technique, the extracts were previously purified through a Graphitized Carbon Black syringe for Solid Phase Extraction. The results revealed that PEF had a positive impact on the alpha acids of bitter hops by increasing the extraction rate of these acids by 20%, while the volatiles demonstrated an increase of 5.6 and 7.4% for humulene and caryophyllene, respectively. Concerning the aromatic variety of hops, the PEF treatment appeared to have no noteworthy effects. © Copyright © 2020 Ntourtoglou, Tsapou, Drosou, Bozinou, Lalas, Tataridis and Dourtoglou

Hyphenated Extraction of Valuable Compounds from Aesculus carnea: Ultrasound Extraction with Pulsed Electric Field Pretreatment

Wood-related procedures, such as lumberjacking and pruning, inevitably result in big piles of leaves, which are considered a major by-product. Extracting valuable compounds from natural by-products is an ongoing trend. In this work, the use of Pulsed Electric Field (PEF) was evaluated as a pretreatment step, prior to the ultrasound-assisted extraction of phenolic compounds from Aesculus carnea leaves. In addition, various solvent systems were examined, as well as the time of pretreatment with PEF. According to the results, up to 33% more phenolic compounds can be extracted, under optimum conditions (30% ethanol in water as solvent and PEF pretreatment for 30 min, compared to the same solvent, without PEF). Moreover, PEF treatment time was not (i.e., 30 and 60 min) and no differences were recorded, suggesting that a lower treatment time can yield the same extraction of phenolic compounds. As such, the use of PEF is highly recommended in combination with ultrasound extraction, to maximize the yield of phenolic compounds extracted from the leaves of Aesculus carnea. © 2022 by the authors

Humic and Fulvic Acids as Specific Sorbents of Herbicides in Water

The ability of humic and fulvic acids (isolated from lignite with a simple, quick, and inexpensive method) to bind the active ingredients of herbicides contaminating drinking water is evaluated. During this study drinking water samples are contaminated with formulated herbicides (imazamox or a mixture of thifensulfuron methyl and tribenuron methyl), while humic and fulvic acids are used as reducing agents. The maximum reducing ability presented by humic and fulvic acids is 72.72% for thifensulfuron methyl and tribenuron methyl and 37.52% for imazamox. Humic acids’ binding ability is superior to that of fulvic acids. © 2021 Wiley-VCH Gmb