Effects of post-fermentation addition of green tea extract for sulfur dioxide replacement on Sauvignon Blanc wine phenolic composition, antioxidant capacity, colour, and mouthfeel attributes.

This study examines the feasibility of replacing SO2 in a New Zealand Sauvignon Blanc wine with a green tea extract. The treatments included the control with no preservatives (C), the addition of green tea extract at 0.1 and 0.2 g/L (T1 and T2), and an SO2 treatment at 50 mg/L (T3). Five monomeric phenolic compounds were detected in the green tea extract used for the experiment, and their concentrations ranged in the order (-)-epigallocatechin gallate > (-)-epigallocatechin > (-)-epicatechin > (-)-epicatechin gallate > gallic acid. At the studied addition rates, these green tea-derived phenolic compounds contributed to ∼70% of the antioxidant capacity (ABTS), ∼71% of the total phenolic index (TPI), and âˆ¼ 84% of tannin concentration (MCPT) of the extract dissolved in a model wine solution. Among wine treatments, T1 and T2 significantly increased the wine's colour absorbance at 420 nm, MCPT, gallic acid and total monomeric phenolic content. TPI and ABTS were significantly higher in wines with preservatives (i.e., T2 > T1 â‰… T3 > C, p < 0.05). These variations were observed both two weeks after the treatments and again after five months of wine aging. Additionally, an accelerated browning test and a quantitative sensory analysis of wine colour and mouthfeel attributes were performed after 5 months of wine aging. When exposed to excessive oxygen and high temperature (50 °C), T1 and T2 exhibited ∼29% and 24% higher browning capacity than the control, whereas T3 reduced the wine's browning capacity by ∼20%. Nonetheless, the results from sensory analysis did not show significant variations between the treatments. Thus, using green tea extract to replace SO2 at wine bottling appears to be a viable option, without inducing a negative impact on the perceptible colour and mouthfeel attributes of Sauvignon Blanc wine.

Contents of ɑ-dicarbonyl compounds in commercial black tea and affected by the processing.

The species and contents of ɑ-dicarbonyls in commercial black tea were examined, along with the effects of the manufacturing process and drying temperature on the formation of ɑ-dicarbonyls. Ten ɑ-dicarbonyls were quantified in commercial and in-process black tea samples by using UPLC-MS/MS and their derived quinoxalines. The ɑ-dicarbonyls content in commercial black tea decreased significantly (p < 0.05) in the following order: 3-deoxyglucosone > glucosone > 3-deoxypentosone = threosone > galactosone ≥ methylglyoxal = glyoxal ≥ 3-deoxygalactosone = 3-deoxythreosone = diacetyl. Except for 3-deoxyglucosone and 3-deoxygalactosone, a further eight ɑ-dicarbonyls were identified in all manufacturing steps of black tea. Except for the drying step, the rolling and fermenting played important roles in the formation of ɑ-dicarbonyls. The total contents of ɑ-dicarbonyls in black tea infusion ranged from 16.48 to 75.32 µg/g based on our detected ten ɑ-dicarbonyls.

Elucidation of Endogenous Aroma Compounds in Tamarillo (Solanum betaceum) Using a Molecular Sensory Approach.

Glycosidically bound volatiles (GBVs) are flavorless compounds in fruits and may undergo hydrolysis during fruit maturation, storage, and processing, releasing free aglycones that are odor active. However, the contribution of glycosidic aglycones to the sensory attributes of fruits remains unclear. Herein, the key odor-active aglycones in tamarillo fruits were elucidated through the molecular sensory approach. We extracted GBVs from three cultivars of tamarillo fruits using solid-phase extraction and subsequently prepared aglycone isolates by enzymatic hydrolysis of GBVs. Gas chromatography-mass spectrometry-olfactometry (GC-MS-O) coupled with odor activity value (OAV) calculation, comparative aroma extract dilution analysis (cAEDA), and omission tests were used to identify key aromatic aglycones. A total of 42 odorants were determined by GC-MS-O analysis. Among them, trans-2,cis-6-nonadienal, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), linalool, 4-vinylguaiacol, geraniol, and α-terpineol showed high OAVs. The cultivar Amber had more aglycones with flavor dilution (FD) factors >16 than the Mulligan cultivar (27 vs 21, respectively), and the Laird's Large fruit showed the highest FD of 1024 for glycosidic DMHF. Omission tests indicated 14 aglycones as essential odorants related to GBVs in tamarillo fruits. Moreover, the enzymatic liberation of aglycones affected the sensory attributes of the tamarillo juice, resulting in an intensified odor profile with noticeable fruity and sweet notes. This study gives insights into the role of endogenous aroma during tamarillo-flavor perception, which lays the groundwork for developing tamarillo-based products with improved sensory properties.

Free and Glycosidic Volatiles in Tamarillo (Solanum betaceum Cav. syn. Cyphomandra betacea Sendt.) Juices Prepared from Three Cultivars Grown in New Zealand.

This study investigated the free and glycosidic-bound volatiles in the juice samples of three tamarillo cultivars (i.e. Amber, Mulligan, and Laird's Large) that are widely grown in New Zealand. Juice samples were prepared from fruits at different ripening stages (green, middle, and ripe). Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was applied to analyze the free volatiles in the samples. A total of 20 free volatiles were detected. Among the samples, the ripe Mulligan juice gave the highest contents of free terpenoids (424 µg/L) and esters (691 µg/L). The glycosidic-bound volatiles were prepared by solid-phase extraction. The matrix effect was evaluated based on the recovery rate of analytes containing multiple aglycone classes. From the results, phenyl ß-d-glucopyranoside was selected to compensate the matrix effect caused by insufficient acquisition of glycosidic volatiles during analyte preparation. In all the ripe-fruit juice samples, the aglycones 4-hydroxy-2,5-dimethyl-3(2H)-furanone and trans-2, cis-6-nonadienal were found to give high odor activity values. According to multivariate statistical analysis, 11 free volatiles and 22 glycosidic volatiles could be potentially applied as volatile makers to distinguish the juice samples. This study has provided a comprehensive understanding of the flavor chemistry of tamarillo juices, with a focus on the potential role of glycosidic aglycones as aroma contributors to tamarillo products.

Development of volatile organic compounds and their glycosylated precursors in tamarillo (Solanum betaceum Cav.) during fruit ripening: A prediction of biochemical pathway.

Key metabolites and flavour-regulation pathways in tamarillo were investigated to explore the development of free and glycosylated volatile organic compounds (VOCs) during fruit maturation. The concentrations of free and bound VOCs were determined by gas chromatography-mass spectrometry analysis. Changes of physical parameters, concentrations of flavour precursors, and activities of key endogenous enzymes were also monitored. A total of 22 free VOCs were identified with C6 alcohols and esters being the major compounds. From the 83 glycosylated VOCs detected, phenols and terpenoids were the dominant components. The concentration of total bound VOCs increased up to 4 times during fruit ripening. Lipoxygenase pathway is confirmed as an important biosynthetic mechanism for the generation of free and glycosylated VOCs during tamarillo ripening. This biosynthesis pathway is highly correlated with the activities of key enzymes and the contents of substrates, especially linolenic acid (p < 0.05 or p < 0.01).

Optimizing the extraction process of natural antioxidants from chardonnay grape marc using microwave-assisted extraction.

The aim of this work was to extract phenolic compounds from Chardonnay grape marc employing a microwave-assisted extraction (MAE). Firstly, the effect of solvent concentration (30-60%), solid mass (1.0-2.0 g) and extraction time (5-15 min) on the recovery of phenolic content and antioxidant capacity was evaluated using a response surface methodology (RSM). The optimal parameters found by RSM were 48% ethanol for the solvent content, 10 min for the extraction time, and 1.77 g for the solid mass. The extraction was carried out at room temperature to increase scaling-up opportunities at industrial level. It was found that the phenolic profile was mainly composed of flavanols, such as procyanidins, catechin and epicatechin. Furthermore, the polyphenols obtained by MAE showed a DPPH· inhibition value of 87 ±â€¯5% and the total phenolic content was 1.21 ±â€¯0.04 mg GAE/mL. Finally, it was observed that the degradation temperature of the extract (≈ 200 °C) was above the temperature commonly used for the manufacture of protein films by thermo-mechanical processes. This highlights the potential use of this extract as a bioactive additive in protein film forming formulations for food and pharmaceutical applications.

Effect of apple cell walls and their extracts on the activity of dietary antioxidants.

The effect of dietary fiber in the form of apple cell walls and pectin extracts on natural antioxidants was examined. Cell walls (CW), isolated from apples ( Malus domestica Borkh. cv. "Pacific Rose"), were incubated with ascorbic acid (AA) or quercetin in N-2-hydroxyethylpiperazine- N'-2-ethanesulfonic acid (HEPES) buffer (pH 6.5) at 37 degrees C for 2 h. The resulting supernatants were characterized by a ferric reducing antioxidant power (FRAP) assay and cyclic voltammetry (CV). The experiments were repeated with pectin isolated from the apple cell walls and commercial pectins and showed that polysaccharide preparations stabilized AA effectively but offered little protection against quercetin oxidation. The water-soluble components from cell walls appeared to be responsible for the observed effects of cell-wall polysaccharide preparations on antioxidant activity.

Label-free electrochemical DNA sensor based on functionalised conducting copolymer.

A simple and label-free electrochemical sensor for recognition of the DNA hybridization event was prepared based on a new functionalised conducting copolymer, poly[pyrrole-co-4-(3-pyrrolyl) butanoic acid]. This precursor copolymer can be easily electrodeposited on the electrode surface and shows high electroactivity in an aqueous medium. An amino-substituted oligonucleotide (ODN) probe was covalently grafted onto the surface of the copolymer in a one step procedure and tested on hybridization with complementary ODN segments. The cyclic voltammogram of ODN probe-modified copolymer showed very little change when incubated in presence of non-complementary ODN, while a significant, and reproducible, modification of the voltammogram was observed after addition of complementary ODN. The AC impedance spectrum showed an increased charge transfer resistance (Rct) and double layer capacitance of the sensor film after hybridisation. Sensors with thinner films showed higher sensitivity than thicker films, suggesting that hybridisation at or near the surface of the film produces a larger change in electrical properties than that within the body of the film.

Chain-breaking antioxidant activity and cyclic voltammetry characterization of polyphenols in a range of green, oolong, and black teas.

A series of eight green, eight oolong, and 17 black teas have been analyzed for polyphenol content by absorbance at 272 nm and cyclic voltammetry response at an inert carbon electrode, a new method developed to provide a rapid measure of easily oxidizable polyphenols in beverages. The chain-breaking antioxidant activity of the teas has also been determined during the chain oxidation of methyl linoleate in a pH 7.4 micellar solution, for which realistic kinetic parameters have been derived. While higher mean values were obtained for green teas than for oolong and black teas, the differences were not large, and the spread of values within each type was considerable. The absorbance at 272 nm correlated well with the cyclic voltammetry response only for green teas and black teas taken on their own. The cyclic voltammetry measure and the antioxidant activity correlated well only for the green teas, where the polyphenol content is dominated by epigallocatechin gallate.