Effect of polyvinylpolypyrrolidone treatment on rosés wines during fermentation: Impact on color, polyphenols and thiol aromas

Impact of pre- and post-fermentation fining with polyvinylpolypyrrolidone on the chemical stability and aromatic profile of Viognier wine

Polyvinylpolypyrrolidone (PVPP) is a synthetic, insoluble polymer that can be added to white wines to improve the chemical stability of the final product by precipitating unstable low molecular weight phenolic compounds responsible for visual defects and undesirable flavor characteristics (e.g., excessive bitterness and/or astringency). The objective of this study was to characterize the effects of PVPP on the quality characteristics of Viognier wine when added pre- or post-fermentation as compared to an untreated control wine. Both PVPP-treated wines contained significantly lower concentrations of monomeric phenolics and browning pigments than the control wine (p ≤ 0.05). The addition of PVPP prior to fermentation conferred protection against oxidation of the wine as measured by acetaldehyde concentration (p ≤ 0.05). Analysis of the volatile aroma profile of each wine by headspace solid phase microextraction gas chromatographymass spectrometry (HS-SPME-GC-MS) revealed that the overarching aroma profiles of the PVPP-treated wines were significantly different from the control wine, but there was no difference between wines treated with PVPP pre-fermentation versus those treated post-fermentation. Specifically, statistically significant differences were observed in 9 of the 22 quantified aroma compounds, including those notably associated with the "stone fruit" aroma of Viognier. A negative correlation was identified between aroma compound concentration removal and the hydrophobicity of each compound, suggesting that the observed differences in aroma may be due to adsorption of aroma compounds by PVPP. The findings from this study present risks and benefits to wine quality upon treatment with PVPP at commercially recommended levels, and provide potentially valuable information for industrial wine producers.

Separation and Purification of Bamboo Leaf Flavones by Polyvinylpolypyrrolidone Adsorption

In view of the adsorption performance of polyvinylpolypyrrolidone (PVPP) to flavones, the adsorption and purification of bamboo leaf flavones (BLFs) by PVPP were studied. The flavones solution was adsorbed by PVPP column chromatography, and then establish a relatively effective method for elution and purification of flavones from bamboo leaf. The optimal separation conditions of column chromatography were determined as the following: the feed concentration of 10 mg/mL, the ratio of diameter to height of 1:1.9, eluents of deionized water (21 mL) and 70% ethanol (800 mL) with a flow rate of 0.33 mL/min. The purity of flavones obtained from ethanol eluents (80-480 mL) was 96.2%. This showed that the PVPP had an ideal adsorption and purification effect on BLFs.

Effect of Protease Combined with Heat Treatment on the Volatile Composition and Aroma Quality in Liqueur Wine

The aim of this paper was to compare the effects of two clarification methods, protease combined with heat treatment and bentonite, on the aroma quality of liqueur wines, and to identify and analyze the overall differences between the basic components and volatile aroma compounds of liqueur wines after the two treatments by chemical analysis, headspace-solid-phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS), and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that total acidity, volatile acidity and pH in liqueur wines after protease combined with heat treatment were not significantly different from those of the blank control, and the ability to remove proteins was equal to that of the bentonite treatment. A total of 58 volatile aroma compounds were detected by HS-SPME-GC/MS. Compared with the blank control group (44 species, total 108.705 mg/L), 52 (83.233 mg/L) and 50 (120.655 mg/L) aroma compounds were detected in the bentonite and protease combined with heat treatments, respectively. Compared with the control and bentonite treatment, the protease combined with heat treatment significantly increased the total content of aromatic compounds in liqueur wines, and the types and contents of olefins, furans and phenols were higher. Among them, the compounds with major contributions in the protease combined with heat treatment were ionone, β-damascenone, 3-methyl-1-butanol, alpha-terpineol and limonene, which helped increase the content of terpenoids and enhance the floral and fruit aroma of the wine. Meanwhile, linalool, diethyl succinate, 2-methyl-3-heptanone, butanal diethyl acetal, hexanal and n-octanol were six compounds with high content of aromatic compounds unique to liqueur wines after protease combined with heat treatment. The sensory evaluation results were consistent with the results of aromatic compound detection, and the overall quality was better. The results may provide a reference for further exploration of protease-based clarifiers suitable for liqueur wines.

Stability of polyphenols in food processing

In recent years, polyphenols have attracted considerable attention due to their diverse potential health-beneficial effects on humans. Polyphenols are widely distributed in natural plants, and therefore play an important role in human food. Thermal processing, irradiation, fermentation, high pressure, microwave, and drying are several popular food processing methods. However, polyphenols are instable in food processing, which easily degrade and react with other components because of their polyhydroxy characteristic. Traditional and advanced technologies have been used to characterize the stability of polyphenols. The main influence factors of stability of polyphenols such as pH, temperature, light, oxygen, enzymes, metal ions, as well as macromolecules, are summarized. Besides, thermal processing greatly promoted the degradation of polyphenols. Thermal degradation mechanisms and products of some polyphenols, such as quercetin and rutin, have been intensively demonstrated. Nevertheless, the structural changes of polyphenols caused by food processing, may lead to different bioactivities from the obtained results based on unprocessed polyphenols. Therefore, to maximize the beneficial effects of polyphenols ingested by human from processed food, the stability of polyphenols in food processing must be thoroughly investigated to assess their real bioactivities. In addition, some available technologies for improving the stability of polyphenols in food processing have been proposed.

Wine Faults: State of Knowledge in Reductive Aromas, Oxidation and Atypical Aging, Prevention, and Correction Methods

The review summarizes the latest scientific findings and recommendations for the prevention of three very common wine faults of non-microbial origin. The first group, presented by the reductive aromas, is caused mainly by excessive H₂S and other volatile sulfur compounds with a negative impact on wine quality. The most efficient prevention of undesirable reductive aromas in wine lies in creating optimal conditions for yeast and controlling the chemistry of sulfur compounds, and the pros and cons of correction methods are discussed. The second is browning which is associated especially with the enzymatic and non-enzymatic reaction of polyphenols and the prevention of this fault is connected with decreasing the polyphenol content in must, lowering oxygen access during handling, the use of antioxidants, and correction stands for the use of fining agents. The third fault, atypical aging, mostly occurs in the agrotechnics of the entire green land cover in the vineyard and the associated stress from lack of nutrients and moisture. Typical fox tones, naphthalene, or wet towel off-odors, especially in white wines are possible to prevent by proper moisture and grassland cover and alternating greenery combined with harmonious nutrition, while the correction is possible only partially with an application of fresh yeast. With the current knowledge, the mistakes in wines of non-microbial origin can be reliably prevented. Prevention is essential because corrective solutions for the faults are difficult and never perfect.

1H-NMR Metabolomics as a Tool for Winemaking Monitoring

The chemical composition of wine is known to be influenced by multiple factors including some viticulture practices and winemaking processes. 1H-NMR metabolomics has been successfully applied to the study of wine authenticity. In the present study, 1H-NMR metabolomics in combination with multivariate analysis was applied to investigate the effects of grape maturity and enzyme and fining treatments on Cabernet Sauvignon wines. A total of forty wine metabolites were quantified. Three different stages of maturity were studied (under-maturity, maturity and over-maturity). Enzyme treatments were carried out using two pectolytic enzymes (E1 and E2). Finally, two proteinaceous fining treatments were compared (vegetable protein, fining F1; pea protein and PVPP, fining F2). The results show a clear difference between the three stages of maturity, with an impact on different classes of metabolites including amino acids, organic acids, sugars, phenolic compounds, alcohols and esters. A clear separation between enzymes E1 and E2 was observed. Both fining agents had a significant effect on metabolite concentrations. The results demonstrate that 1H-NMR metabolomics provides a fast and robust approach to study the effect of winemaking processes on wine metabolites. These results support the interest to pursue the development of 1H-NMR metabolomics to investigate the effects of winemaking on wine quality.

Two-Dimensional Infrared Correlation Spectroscopy, Conductor-like Screening Model for Real Solvents, and Density Functional Theory Study on the Adsorption Mechanism of Polyvinylpolypyrrolidone for Effective Phenol Removal in an Aqueous Medium

The discharge of industrial effluents, such as phenol, into aquatic and soil environments is a global problem due to its serious negative impacts on human health and aquatic ecosystems. In this study, the ability of polyvinylpolypyrrolidone (PVPP) to remove phenol from an aqueous medium was investigated. The results showed that a significant proportion of phenol (up to 74.91%) was removed using PVPP at pH 6.5. Isotherm adsorption experiments of phenol on PVPP indicated that the best-fit adsorption was obtained using Langmuir models. The response peaks of the hydroxyl groups of phenol (OH) and the carboxyl groups (i.e., C=O) of PVPP were altered, indicating the formation of a hydrogen bond between the PVPP and phenol during phenol removal, as characterized using 1D and 2D IR spectroscopy. The resulting complexes were successfully characterized based on their thermodynamic properties, Mulliken charge, and electronic transition using the DFT approach. To clarify the types of interactions taking place in the complex systems, quantum theory of atoms in molecules (QTAIM) analysis, reduced density gradient noncovalent interaction (RDG-NCI) approach, and conductor-like screening model for real solvents (COSMO-RS) approach were also successfully calculated. The results showed that the interactions that occurred in the process of removing phenol by PVPP were through hydrogen bonding (based on RDG-NCI and COSMO-RS), which was identified as an intermediate type (∇2ρ(r) > 0 and H < 0, QTAIM). To gain a deeper understanding of how these interactions occurred, further characterization was performed based on adsorption mechanisms using molecular electrostatic potential, global reactivity, and local reactivity descriptors. The results showed that during hydrogen bond formation, PVPP acts as a nucleophile, whereas phenol acts as an electrophile and the O9 atom (i.e., donor electron) reacts with the H22 atom (i.e., acceptor electron).

Selenium bio-enrichment of Mediterranean fruit juices through lactic acid fermentation

This work was carried out to elaborate selenium (Se) bio-enriched fermented Mediterranean fruit juices. To this purpose, pomegranate and table red grape juices were added with sodium selenite (Na₂SeO₃) and fermented by Levilactobacillus brevis CRL 2051 and Fructobacillus tropaeoli CRL 2034 individually or combined. To better evaluate the effect of selenite addition and starter strain inoculums on the total bacterial community of the fruit juices, fermentation trials were performed with raw and pasteurized fruit juices. No statistical significant differences were observed for total mesophilic microorganisms (TMM) and rod-shaped lactic acid bacteria (LAB) levels among raw and pasteurized juices inoculated with the starter strains, while significant differences between those juices with and without selenite were registered. LAB cocci, Pseudomonadaceae and yeasts were detected only for the raw juice preparations. The dominance of L. brevis CRL 2051 and F. tropaeoli CRL 2034 was confirmed by randomly amplified polymorphic DNA (RAPD)-PCR analysis. After fermentation, pH dropped for all inoculated trials and control raw juices. The soluble solid content (SSC) levels of the raw juices were higher than the corresponding pasteurized trials. The thermal treatment affected consistently yellowness of grape juice trials and redness of pomegranate juices. No microbial Se accumulation was registered for pomegranate juices, while F. tropaeoli CRL 2034 accumulated the highest amount of Se (65.5 μg/L) in the grape juice. For this reason, only trials carried out with raw grape juices were investigated by metagenomics analysis by Illumina MiSeq technology. Non-inoculated grape juices were massively fermented by acetic acid bacteria while Fructobacillus and Lactobacillus (previous genus name of Levilactobacillus) represented the highest operational taxonomy units (OTUs) relative abundance % of the trials inoculated with the starter strains as confirmed by this technique.

Wine Polyphenol Content and Its Influence on Wine Quality and Properties: A Review

Wine is one of the most consumed beverages around the world. It is composed of alcohols, sugars, acids, minerals, proteins and other compounds, such as organic acids and volatile and phenolic compounds (also called polyphenols). Polyphenols have been shown to be highly related to both (i) wine quality (color, flavor, and taste) and (ii) health-promoting properties (antioxidant and cardioprotective among others). Polyphenols can be grouped into two big families: (i) Flavonoids, including anthocyanidins, flavonols, flavanols, hydrolysable and condensed tannins, flavanones, flavones and chalcones; and (ii) Non-flavonoids, including hydroxycinnamic acids, hydroxybenzoic acids, stilbenes, tyrosol and hydroxytyrosol. Each group affects in some way the different properties of wine to a greater or a lesser extent. For that reason, the phenolic composition can be managed to obtain singular wines with specific, desirable characteristics. The current review presents a summary of the ways in which the phenolic composition of wine can be modulated, including (a) invariable factors such as variety, field management or climatic conditions; (b) pre-fermentative strategies such as maceration, thermovinification and pulsed electric field; (c) fermentative strategies such as the use of different yeasts and bacteria; and (d) post-fermentative strategies such as maceration, fining agents and aging. Finally, the different extraction methods and analytical techniques used for polyphenol detection and quantification have been also reviewed.

A new cyanine from oxidative coupling of chlorogenic acid with tryptophan: Assessment of the potential as red dye for food coloring

A red pigment was prepared by reaction of chlorogenic acid (CGA) with tryptophan (TRP) in air at pH 9 (37% w/w yield) and evaluated as food dye. The main component of pigment was formulated as an unusual benzochromeno[2,3-b]indole linked to a TRP unit, featuring a cyanine type chromophore (λ_max 542, 546 nm, 1% extinction coefficient of the sodium salt = 244 ± 2). The chromophore showed a minimal pH dependence and proved stable for at least 3 h at 90 °C, both at pH 3.6 or 7.0, whereas red wine anthocyanins showed a substantial (30%) and betanin a complete abatement after 1 h at the acidic pHs. An intense coloring of different food matrices was obtained with the pigment at 0.01 % w/w. No toxicity was observed up to 0.2 mg/mL on hepatic and colonic cell lines. These data make this dye a promising alternative for red coloring of food.

Graphene Oxide-Crospolyvinylpyrrolidone Hybrid Microspheres for the Efficient Adsorption of 2,4,6-Trichlorophenol

Microspheres of the graphene oxide and crospolyvinylpyrrolidone composite (GO-PVPP) were prepared via suspension polymerization and investigated for the adsorption of 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. The microspheres were thoroughly characterized using scanning electron microscopy, infrared spectroscopy, N2 physisorption, elemental analysis, X-ray diffraction, and thermogravimetric analysis. The GO-PVPP microspheres comprised GO sheets on the surface and demonstrated good thermal stability, good swelling rate, and excellent adsorption capacity of 2,4,6-TCP (up to 466.77 mg/g). The adsorptions were determined as a function of pH, temperature, adsorbent loading, adsorption time, and initial content of 2,4,6-TCP in the solutions. The sorption kinetics was satisfactorily modeled using the pseudo-second-order rate equation, and the sorption equilibrium can be described using the Freundlich model. The 2,4,6-TCP adsorption by GO-PVPP was shown to be endothermic and spontaneous. The reusability of GO-PVPP was also demonstrated by the adsorption and desorption cycles.

Effect of Different Clarification Treatments on the Volatile Composition and Aromatic Attributes of 'Italian Riesling' Icewine

The aim of this study was to evaluate the influence of clarification treatments on volatile composition and aromatic attributes of wine samples. ‘Italian Riesling’ icewines from the Hexi Corridor Region of China were clarified by fining agents (bentonite (BT) and soybean protein (SP)), membrane filtration (MF), and centrifugation (CF) methods. The clarity, physicochemical indexes, volatile components, and aromatic attributes of treated wines were investigated. Both the fining agents and mechanical clarification treatments increased the transmittance and decreased the color intensity of icewine samples. Bentonite fining significantly influenced the total sugar content, total acidity and volatile acidity. Total acidity decreased 2–3.5% and volatile acidity 2–12%. MF showed the greatest influence on total phenol content, decreasing the initial content by 12%, while other treatments by less than 8%. Volatile analysis indicated that both the categories and contents of volatile compounds of wine samples decreased. MF treatment showed the most significant influence, while SP fining showed much lower impact. Odor activity values indicated the compound with the highest odor activity in Italian Riesling icewines was β-damascenone. For this compound, BT and SP did not show significant differences, however, in MF and CF it decreased by 20% and 63%, respectively. Furthermore, with high impact on aroma were: ethyl hexanoate which reduced by 20–80% especially in MF; rose oxide which extremely reduced in MF and undetected in BT, SP, and CF; isoamyl acetate which reduced by 3–33% and linalool decreased by 10–20% and undetected for BT. Principle component analysis indicated that icewine clarified by different methods could be distinguished and positively correlated with odor-active compounds. Floral and fruity were the dominant aroma series in icewine samples followed by fatty, earthy, spicy, vegetative and pungent flavor. The total odor active value of these series significantly (p < 0.5) decreased in different clarification treatments. Sensory evaluation showed similar results, but the SP and CF wine samples achieved better sensory quality. This study provides information that could help to optimize the clarification of ice wines.

The enantioselective effects and potential risks of paclobutrazol residue during cucumber pickling process

For decades, pesticides have been widely used for controlling pests and protecting crops around the world, and the food safety issues caused by these compounds have raised widespread concern. However, the different enantioselective behaviors and biological activities of chiral pesticide enantiomers are often ignored. In this work, a novel method was put forward to investigate the enantioselective effects and potential risks of two paclobutrazol enantiomers during cucumber pickling process. The degradation kinetics indicated that when paclobutrazol reside in cucumber and was introduced into the pickling process, the half-time of paclobutrazol isomers were significantly different (9.24 d and 16.6 d), and the conversion phenomenon between the two enantiomers could also be observed. In addition, results from 16S rRNA and ITS sequencing shown that (2R, 3R)-paclobutrazol and (2S, 3S)-paclobutrazol have an obviously enantiomeric effects on microbial community of pickling system and the degradation of paclobutrazol was probably attributed to the presence of Pseudomonas and Serratia. Finally, the microorganisms functions were found to be disrupted under the exposure of (2R, 3R)-paclobutrazol and metabolic function of microorganisms to xenobiotic was inhibited, which might cause potential risks to the quality of preserved foods. In summary, we have devised a method and provided a novel insight into the potential risks of chiral pesticide residues on food safety and human health.

Use of Oak and Cherry Wood Chips during Alcoholic Fermentation and the Maturation Process of Rosé Wines: Impact on Phenolic Composition and Sensory Profile

There is a lack of knowledge about the use of different wood species on rosé wine production. Thus, this work focused on the impact of the addition of wood chips from oak and cherry trees during the alcoholic fermentation and maturation process on rosé wine characteristics. Therefore, phenolic composition and sensory characteristics were monitored during the rosé wines' production. The use of wood chips during alcoholic fermentation induced a significant increase of phenolic content in rosé musts. During rosé wine maturation, the wood chip contact induced significantly higher values of colored anthocyanins, color intensity, and polymeric pigments, and significantly lower values of color hue in the corresponding rosé wines. In terms of sensory profile, a tendency for lower scores of "overall appreciation" were attributed to control rosé wine, while significantly higher scores for "color intensity" descriptor were attributed to all rosé wines matured in contact with wood chips. For the majority of phenolic parameters and individual phenolic compounds quantified, a clear and specific influence of the use of oak and cherry wood chips was not detected, except for (+)-catechin, where the rosé wines produced in contact with cherry chips showed the highest values. This study provides relevant information for winemakers about the impact of the use of wood chips on rosé wine quality.