Pre-fermentative replacement of sulphur dioxide by lysozyme and oenological tannins: Effect on the formation and evolution of volatile compounds during the bottle storage of white wines

Influence of vinification process over the composition of volatile compounds and sensorial characteristics of greek wines

Wine is one of the most traditional consumed alcoholic beverages in the world. Millions of wine enthusiasts worldwide duly appreciate a wine of excellent quality in terms of physicochemical and sensorial properties. Different classes of wines have different volatile compositions and sensorial properties, which can be altered, depending on the vinification process and use of additives. Among the widely employed additives in wine production is sulfite (SO₂). The popularity of sulfite lies in its ability to preserve the flavor and freshness of wine; however, depending on the quantity, sulfite can pose serious health risks to consumers and affect the quality of the drink. The present study evaluated and compared the compositions of volatile compounds and sensorial properties of sparkling and traditional wines (with and without SO₂) produced from Greek grapes 'Grechetto', 'Greco bianco' and 'Greco di tufo'. The results obtained of the composition of volatile compounds in these wines pointed to differences between SO₂-containing, SO₂-free and sparkling wines, with different amounts of compounds such as alcohols, esters, fatty acids, phenols and differences in sensorial properties. The 'Grechetto' wine, prepared without SO₂, exhibited greater quality, better volatile composition, and better sensorial properties compared to the wines produced with SO₂.

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The online version contains supplementary material available at 10.1007/s13197-021-05160-y.

Impact of tannin addition on the antioxidant activity and sensory character of Malagousia white wine

Enological tannins are assessed as promising alternative to SO2 in order to control oxidative process during winemaking, due to allergic reactions incurred by sulfite sensitive individuals. In the present study, the commercial enological Tara tannin "Vitanil B″ was added, as alternative to the addition of sulfites, at different concentrations (100-500 mg/L) in white wine from grapes of Vitis vinifera L. var. Malagousia in order to enhance antioxidant stability and sensory character of the wine. Considering photometric analyses and chromatic parameters results, tannin addition (300 mg/L) in Malagousia enhanced total phenolic content, antioxidant and antiradical activity and prevented color deterioration, for a storage period of 100 d, compared to control and sulfited wines. Moreover, aroma quality, body, after taste and overall acceptance of wine treated with 300 mg/L tannin, were highly appreciated and received the highest scores. The overall evaluation of tannin addition was performed by Principal Component Analysis, leading to discrimination of wines, according to photometric, color and sensory analysis parameters. Conclusively, tannin addition resulted in a considerable increase of total phenolic content, antioxidant and antiradical activity, compared to the control and sulfited wines, maintaining the sensory parameters and overall acceptance of Malagousia wine.

Moment of Bentonite Addition, Co-Addition of Tannins, and Bentonite Type Affect the Differential Affinity of Pathogenesis-Related Grape Proteins towards Bentonite during Fermentation

To test the effect of the moment of bentonite addition, co-addition of tannins, and bentonite type on the differential affinity of pathogenesis-related (PR) proteins towards bentonite during grape must fermentation, three separate experiments were set up. PR proteins in the obtained wines were analyzed by reverse phase and size exclusion high-performance liquid chromatography (HPLC). The most significant reduction of bentonite dose and PR protein concentration was achieved by applying bentonite in the last third of fermentation. Particular thaumatin-like proteins (TLP) and proteins with lower molecular mass in general were more affected than others, while TLPs were more affected than chitinases. Exogenous enological tannins interacted with particular PR proteins, mostly TLPs, and lowered the total bentonite dose required. The combined application of tannins and bentonite in fermentation removed more PR proteins than bentonite alone, but did not achieve a synergistic effect in reducing the bentonite dose. Various bentonite types, including two Na-activated bentonites, an activated Na bentonite with specifically adsorbed silica, and an active Na-Ca bentonite, exhibited differential affinity towards different PR proteins. The results obtained could be used in developing wine fining protocols which combine treatments with complementary affinity for adsorption and removal of PR proteins, and in this way achieve greater efficiency of bentonite fining by reducing its total dose, which is of significant interest to the wine industry.

Bacteriophages as an Up-and-Coming Alternative to the Use of Sulfur Dioxide in Winemaking

Certain acetic and lactic acid bacteria are major causes of quality defects in musts and wines, giving rise to defects such as a "vinegary," "sharp, like nail polish-remover" taste or preventing alcoholic and/or malolactic fermentation. Sulfur dioxide is the major tool currently used in the control of these bacteria in wine. The aim of this work was to isolate bacteriophages from musts and wine of different grape varieties that were able to eliminate lactic and acetic acid bacteria spoilages at the laboratory scale. Musts obtained from grape-berries of Vitis vinifera cv. Chardonnay and Moscatel and a red wine made with V. vinifera cv. Tintilla de Rota were used to isolate bacteriophages. Bacteriophages were obtained from each of the musts and the wine and belonged to the order Caudovirals and the family Tectivirals. They were isolated by classical virology methods and identified by electron microscopy. The host bacteria used in the study were lactic acid bacteria of the species Lactobacillus hilgardii, Lactobacillus plantarum, and Oenococcus oeni and the acetic bacteria Acetobacter aceti. A comparative study was performed by adding phage titrations and SO2 to musts and wines, which had been previously inoculated with bacteria, to study the effectiveness of bacteriophages against bacteria. The comparative study showed that some bacteriophages were as effective as sulfur dioxide at low concentrations.

Chemical hazards in grapes and wine, climate change and challenges to face

Climate change has an impact on the chemical risks associated to wine consumption related with grape development and microbial contamination. We can classify chemical hazards in wine into two groups: those present in grapes due to agricultural practices, environmental contamination or fungal growth and those coming from fermentation and the winemaking process. The first group includes mycotoxins, whilst the second encompasses ethyl carbamate, biogenic amines, sulfur dioxide and proteins used as technological ingredients such as fining material. Usually the effective control of chemical hazards is achieved by assuring that they either are minimized or absent in the final product since their removal is somewhat difficult and sometimes it may affect sensory properties, which is a major issue in wine. Interestingly, it is possible to give recommendations to avoid excess of these compounds, but more research is needed to face future challenges related to climate change and consumer demands.

Influence of Glutathione and Ascorbic Acid Treatments during Vinification of Feteasca Regala Variety and Their Antioxidant Effect on Volatile Profile

Volatile profiles were determined for white wines of Feteasca regala variety produced from musts in which the antioxidants glutathione and ascorbic acid were added in different proportions before inception of alcoholic fermentation. Treatments with these antioxidants affect some volatile compound evolution and positively influence the wine volatile profile. After one year of storage in bottles with and without carbon dioxide protection the volatile profiles of the wines were assessed by using a Fast GC Alpha MOS Heracles e-Nose by applying a DFA multivariate statistical method and AroChemBase database for compound identification. The analyses showed that some higher alcohols, such as 2-phenylethanol and 2-methyl-1-butanol were in lower concentrations in wines treated with reduced glutathione, while the main ethyl fatty acid esters, such as ethyl butanoate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate were better preserved when higher concentrations of any of the antioxidants were added in must. On the other hand, it was observed that some other volatile compounds were not affected by these applied treatments.

Natural extracts from grape seed and stem by-products in combination with colloidal silver as alternative preservatives to SO2 for white wines: Effects on chemical composition and sensorial properties

The search for alternative additives to sulfur dioxide, with antioxidant and antimicrobial activity, in the production of wines is one of the current objectives of the enological industry. In the present study, aqueous extracts obtained from winery byproducts (grape seeds and stems), alone or in combination with colloidal silver complex, have been used in white vinification. The antimicrobial effect of the extracts was similar to that of sulfur dioxide, being more effective on lactic and acetic bacteria in those wines to which colloidal silver was added. The effect on the color, the phenolic compounds and the volatile fraction of the wines was evaluated, as well as their sensory profile. The use of both extracts modified the color of the wines, increasing the chromatic parameters a* and b*, indicating a browning tendency, although no other signs of oxidation were found. Wines with seed extracts contained higher amounts of flavan-3-ols, and a significant increase in some volatile compounds such as fatty acid ethyl esters and benzene compounds, which were identified in the extracts. From a sensorial point of view, the wines with stem extracts were the most similar to those elaborated with SO₂, detecting a certain bitterness in wines with seed extracts.

Alternative Methods to SO2 for Microbiological Stabilization of Wine

The use of sulfur dioxide (SO₂ ) as wine additive is able to ensure both antioxidant protection and microbiological stability. In spite of these undeniable advantages, in the last two decades the presence of SO₂ in wine has raised concerns about potential adverse clinical effects in sensitive individuals. The winemaking industry has followed the general trend towards the reduction of SO₂ concentrations in food, by expressing at the same time the need for alternative control methods allowing reduction or even elimination of SO_2. In the light of this, research has been strongly oriented toward the study of alternatives to the use of SO₂ in wine. Most of the studies have focused on methods able to replace the antimicrobial activity of SO₂ . This review article gives a comprehensive overview of the current state-of-the-art about the chemical additives and the innovative physical techniques that have been proposed for this purpose. After a focus on the chemistry and properties of SO₂ in wine_, as well as on wine spoilage and on the conventional methods used for the microbiological stabilization of wine, recent advances on alternative methods proposed to replace the antimicrobial activity of SO₂ in winemaking are presented and discussed. Even though many of the alternatives to SO₂ showed good efficacy, nowadays no other physical technique or additive can deliver the efficacy and broad spectrum of action as SO₂ (both antioxidant and antimicrobial), therefore the alternative methods should be considered a complement to SO₂ in low-sulfite winemaking, rather than being seen as its substitutes.

Inoculation of Torulaspora delbrueckii as a bio-protection agent in winemaking

In oenology, bio-protection consists in adding bacteria, yeasts or a mixture of microorganisms on grape must before fermentation in order to reduce the use of chemical compounds such as sulphites. More particularly, non-Saccharomyces yeasts are used as a total or partial alternative to sulphites. However, scientific data capable of proving the effectiveness of adding these yeasts on grape must is lacking. This study reports the analysis of antimicrobial and antioxidant effects of one non-Saccharomyces yeast, Torulaspora delbrueckii, inoculated at the beginning of the white winemaking process in two Burgundian wineries as an alternative to sulphiting. The implantation of the T. delbrueckii strain was successful in both wineries and had no impact on fermentation kinetics. Adding T. delbrueckii reduced biodiversity during the pre-fermentation stages compared to sulphited controls and it also effectively limited the development of spoilage microorganisms in the same way as the addition of sulphites. T. delbrueckii could protect must and wine from oxidation as demonstrated by the analysis of colour and phenolic compounds. This is the first evidence that early addition of T. delbrueckii during winemaking can be a microbiogical and chemical alternative to sulphites. However, its contribution seems to be matrix dependent.

The Effects of Pre-Fermentative Addition of Oenological Tannins on Wine Components and Sensorial Qualities of Red Wine

Today in the wine industry, oenological tannins are widely used to improve wine quality and prevent oxidation in wine aging. With the development of tannin products, new oenological tannins are developed with many specific functions, such as modifying antioxidant effect, colour stabilization and aroma modifications. The aim of this work is to investigate effects of pre-fermentative addition of oenological tannins on wine colour, anthocyanins, volatile compounds and sensorial properties. In this case, Syrah juice was extracted with classic flash thermovinification from fresh must in order to release more colour and tannins. Three types of oenological tannins, which are, respectively, derived from grape skin, seed (Vitis vinifera) and French oak (Quercus robur and Querrus petraea), were selected to carry out the experiments with seven treatments. Results indicated that tannin treatments significantly improved wine aroma complexity and sensorial properties. However, the concentration of some stable pigments such as Vitisin A, Vitisin A-Ac and Vitisin B was negatively affected by tannin additions. Nevertheless, by means of cluster analysis and principal component analysis, it was observed that higher alcohols were significantly promoted by grape seed tannin while most anthocyanins can be improved by addition of grape tannins. In conclusion, low amount of oenological tannin derived from grape seed is a promising method to be applied especially for young red wine making.

Improvement of wine aromatic quality using mixtures of lysozyme and dimethyl dicarbonate, with low SO2 concentration

The use of sulphur dioxide (SO2) in the treatment of foodstuffs presents some problems as it could lead to pseudo-allergies in some people. The aim of this research work was to study the addition of different preservative mixtures and their influence on the concentration of volatile compounds and sensorial quality in wine. To do so, vinifications were carried out using Garnacha must to which lysozyme, dimethyl dicarbonate (DMDC) and mixtures of these with SO2 were added at different doses (25 and 50 mg l(-1)). The results were compared with a control sample to which only SO2 had been added (50 mg l(-1)). In general, mixtures of SO2 with lysozyme and DMDC favoured the formation of volatile compounds in the wines. Wines obtained from the mixtures of lysozyme and DMDC with 25 mg l(-1) of SO2 had better sensorial quality than the wines obtained with 50 mg l(-1) as the only preservative used.

Activity of lysozyme on Lactobacillus hilgardii strains isolated from Port wine

This work evaluated the effect of lysozyme on lactobacilli isolated from Port wine. Bacterial growth experiments were conducted in MRS/TJ medium and inactivation studies were performed in phosphate buffer (KH2PO4), distilled water and wine supplemented with different concentrations of lysozyme. The response of bacteria to lysozyme was found to be highly strain dependent. Some strains of Lactobacillus hilgardii together with Lactobacillus collinoides and Lactobacillus fructivorans were found to be resistant to concentrations of lysozyme as high as 2000 mg/L. It was observed that among the L. hilgardii taxon the resistant strains possess an S-layer coat. Apparently, the strains of L. collinoides and L. fructivorans studied are also S-layer producers as suggested by the total protein profile obtained by SDS-PAGE. Thus, the hypothetical protective role of the S-layer against the action of lysozyme was investigated. From the various treatments used to remove the protein from the surface of the cells, the one employing LiCl (5 M) was the most effective. LiCl pre-treated cells exposed to lysozyme (2000 mg/L) in KH2PO4 buffer maintained its resistance. However, when cells were suspended in distilled water an increased sensitivity to lysozyme was observed. Moreover, it was found that the addition of ethanol (20% v/v) to the suspension medium (distilled water) triggered a strong inactivation effect especially on cells previously treated with LiCl (reduction of >6 CFU log cycles). The results suggest that the S-layer exerts a protective effect against lysozyme and that the cell suspension medium influences the bacteriolysis efficiency. It was also noted that ethanol enhances the inactivation effect of lysozyme.

Application and bioactive properties of proteins and peptides derived from hen eggs: opportunities and challenges

Several proteins and peptides that are released in vitro and/or in vivo from hen eggs are biologically active and have a variety of functional properties in humans beyond normal nutrition, for which extensive studies have been performed. This review focuses on their biological activities, including antihypertensive, antioxidant, antimicrobial, antiadhesive, immunomodulatory and antithrombotic activities and enhancement of mineral absorption. These proteins and peptides have been shown to regulate the nervous system, cardiovascular system, immune system and gastrointestinal system. The potential application and future directions of research on these bioactive peptides and proteins in the food industry are also addressed.

Hen egg white lysozyme permeabilizes Escherichia coli outer and inner membranes

Natural preservatives answer the consumer demand for long shelf life foods, synthetic molecules being perceived as a health risk. Lysozyme is already used because of its muramidase activity against Gram-positive bacteria. It is also described as active against some Gram-negative bacteria; membrane disruption would be involved, but the mechanism remains unknown. In this study, a spectrophotometric method using the mutant Escherichia coli ML-35p has been adapted to investigate membrane disruption by lysozyme for long durations. Lysozyme rapidly increases the permeability of the outer membrane of E. coli due to large size pore formation. A direct delayed activity of lysozyme against the inner membrane is also demonstrated, but without evidence of perforations.

Edge-tailored graphene oxide nanosheet-based field effect transistors for fast and reversible electronic detection of sulfur dioxide

Graphene oxide was tailored into GO nanosheets with periodic acid treatment. Interestingly, the latter have a superior sensing performance for the fast and reversible detection of SO(2) compared with the former at room temperature. Its sensing mechanism was proposed from the structural changes of the GO nanosheets during the sensing and recovering processes.

Distillation and detection of SO2 using a microfluidic chip

A miniaturized distillation system is presented for separating sulfurous acid (H(2)SO(3)) into sulfur dioxide (SO(2)) and water (H(2)O). The major components of the proposed system include a microfluidic distillation chip, a power control module, and a carrier gas pressure control module. The microfluidic chip is patterned using a commercial CO(2) laser and comprises a serpentine channel, a heating zone, a buffer zone, a cooling zone, and a collection tank. In the proposed device, the H(2)SO(3) solution is injected into the microfluidic chip and is separated into SO(2) and H(2)O via an appropriate control of the distillation time and temperature. The gaseous SO(2) is then transported into the collection chamber by the carrier gas and is mixed with DI water. Finally, the SO(2) concentration is deduced from the absorbance measurements obtained using a spectrophotometer. The experimental results show that a correlation coefficient of R(2) = 0.9981 and a distillation efficiency as high as 94.6% are obtained for H(2)SO(3) solutions with SO(2) concentrations in the range of 100-500 ppm. The SO(2) concentrations of two commercial red wines are successfully detected using the developed device. Overall, the results presented in this study show that the proposed system provides a compact and reliable tool for SO(2) concentration measurement purposes.