Influence of microbial communities on the chemical and sensory features of Falanghina sweet passito wines

From bioprotective effects to diversification of wine aroma: Expanding the knowledge on Metschnikowia pulcherrima oenological potential

Microbial diseases are of major concern in vitiviniculture as they cause grape losses and wine alterations, but the prevention with chemical substances represents a risk to human health and agricultural ecosystem. A promising alternative is the biocontrol and bioprotection activity of non-Saccharomyces yeasts, such as Metschnikowia pulcherrima, which also presents positive oenological traits when used in multistarter fermentations. The aim of this study was to assess the impact of a selected M. pulcherrima strain in the post-harvest withering and vinification of Garganega grapes to produce the sweet 'passito' wine Recioto di Gambellara DOCG (Italy). M. pulcherrima was firstly inoculated on grape at the beginning of the withering process, and afterwards in must for multistarter sequential microfermentation trials with Saccharomyces cerevisiae. Microbiological, chemical, and sensory analyses were carried out to monitor the vinification of treated and control grapes. Grape bunches during withering were a suitable environment for the colonization by M. pulcherrima, which effectively prevented growth of molds. Differences in grape must composition were observed, and the diverse inoculation strategies caused noticeable variations of fermentation kinetics, main oenological parameters, wine aroma profile, and sensory perception. M. pulcherrima proved effective to protect grapes against fungal infections during withering and contribute to alcoholic fermentation generating wine with distinguished aromatic characteristics.

Fine wine recognition and appreciation: It is time to change the paradigm of wine tasting

Wine quality maybe understood under two perspectives: (a) commercial quality, intended to satisfy overall consumers, and (b) fine wine quality, aimed at achieving a product with aesthetic value. The current food sensory techniques (e.g. Descriptive Analysis) have been successfully applied to develop wines accepted worldwide and characterized by pleasant sweetish flavours and smooth mouthfeel. On the contrary, these techniques are not suited to characterize fine wines given their dependence on sensory properties with aesthetic value. The conventional tasting approaches follow the sequence of vision, smell (orthonasal), taste and mouthfeel, ending by an overall evaluation. The sensory descriptors tend to be analytic (e.g. different aromas and tastes) or synthetic (e.g. body, structure) and the quality judgement is left for the final step. Some synthetic attributes may have an aesthetic significance (e.g. complexity, harmony, depth) and are more valued when the analytic or synthetic descriptors are highly praised (e.g. oakiness, silkiness, body, minerality). Consequently, these highly praised attributes are regarded as surrogates of fine wine quality. However, commercial wines are frequently judged of higher quality than fine wines irrespective of the taster expertise. We argue that the conventional sensory analysis sequence makes the overall evaluation secondary in relation to the previous analytical steps blurring the assessment of wine's aesthetic properties. Probably due to top-down processing, the initial evaluation of colour or flavours governs the final overall quality evaluation that may be inconsistently rated. Then, to promote the recognition of fine wines, tasting should begin by first acknowledging the aesthetic properties and only proceed to the analytical steps if necessary. A tasting method is proposed to consumer educational programs where emotional responses are used to explain the differences between commercial and fine wine styles. Furthermore, cultural aspects should be included to appreciate the wholeness of wine. Hopefully, this holistic perspective would turn wine appreciation more approachable and facilitate the recognition of fine wines among consumers, increasing their appreciation and enjoyment.

Isolation and Characterization of Cryotolerant Yeasts from Fiano di Avellino Grapes Fermented at Low Temperatures

A fermentation of Fiano di Avellino grape must was carried out at 9°C with the aim of selecting cryotolerant yeast strains and testing their fermentative performances and volatile production following molecular characterization. A total of 20 yeast cultures were isolated at different fermentation stages. Based on molecular identification and characterization, Metschnikowia (M.) pulcherrima, Hanseniaspora (H.) uvarum, Staremerella (St.) bacillaris, Saccharomyces (S.) cerevisiae, S. kudriavzevii, and S. paradoxus were found to be the yeast species dominating the fermentation. S. paradoxus has been rarely isolated in vineyards and never in the cellar environment. Moreover, in this study, S. kudriavzevii is detected for the first time in vine-wine environments. Both S. kudriavzevii and S. paradoxus co-occurred with S. cerevisiae when grapes were micro-fermented at low temperatures. The growth kinetics of the three species were greatly affected by the fermentation temperature. As a consequence, Fiano wines obtained with S. kudriavzevii and S. paradoxus significantly differed from those made by S. cerevisiae in terms of chemical and volatile composition.

Impact of Two Commercial S. cerevisiae Strains on the Aroma Profiles of Different Regional Musts

The present research is aimed at investigating the potential of two commercial Saccharomyces cerevisiae strains (EC1118 and AWRI796) to generate wine-specific volatile molecule fingerprinting in relation to the initial must applied. To eliminate the effects of all the process variables and obtain more reliable results, comparative fermentations on interlaboratory scale of five different regional red grape musts were carried out by five different research units (RUs). For this purpose, the two S. cerevisiae strains were inoculated separately at the same level and under the same operating conditions. The wines were analyzed by means of SPME-GC/MS. Quali-quantitative multivariate approaches (two-way joining, MANOVA and PCA) were used to explain the contribution of strain, must, and their interaction to the final wine volatile fingerprinting. Our results showed that the five wines analyzed for volatile compounds, although characterized by a specific aromatic profile, were mainly affected by the grape used, in interaction with the inoculated Saccharomyces strain. In particular, the AWRI796 strain generally exerted a greater influence on the aromatic component resulting in a higher level of alcohols and esters. This study highlighted that the variable strain could have a different weight, with some musts experiencing a different trend depending on the strain (i.e., Negroamaro or Magliocco musts).

Profiling the role of microorganisms in quality improvement of the aged flue-cured tobacco

Background

The aging process in the tobacco production, as in other food industries, is an important process for improving the quality of raw materials. In the spontaneous aging, the complex components in flue-cured tobacco (FT) improve flavor or reduce harmful compounds through chemical reactions, microbial metabolism, and enzymatic catalysis. Some believed that tobacco-microbe played a significant part in this process. However, little information is available on how microbes mediate chemical composition to improve the quality of FT, which will lay the foundation for the time-consuming spontaneous aging to seek ways to shorten the aging cycle.

Results

Comparing aged and unaged FT, volatile and non-volatile differential compounds (DCs) were multi-dimensionally analyzed with the non-targeted metabolomes based on UPLC-QTOP-MS (the ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry), GC–MS (gas chromatography-mass spectrometer) assisted derivatization and HP-SPME-GC/MS (headspace solid-phase micro-extraction assisted GC–MS). Products associated with the degradation pathways of terpenoids or higher fatty acids were one of the most important factors in improving FT quality. With the microbiome, the diversity and functions of microbial flora were analyzed. The high relative abundance function categories were in coincidence with DCs-related metabolic pathways. According to the correlation analysis, Acinetobacter, Sphingomonas and Aspergillus were presumed to be the important contributor, in which Aspergillus was associated with the highest number of degradation products of terpenoids and higher fatty acids. At last, the screened Aspergillus nidulans strain F4 could promote the degradation of terpenoids and higher fatty acids to enhance tobacco flavor by secreting highly active lipoxygenase and peroxidase, which verified the effect of tobacco-microbes on FT quality.

Conclusions

By integrating the microbiome and metabolome, tobacco-microbe can mediate flavor-related substances to improve the quality of FT after aging, which provided a basis for identifying functional microorganisms for reforming the traditional spontaneous aging.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02597-9.

Valorization of Traditional Alcoholic Beverages: The Study of the Sicilian Amarena Wine during Bottle Aging

Traditional alcoholic beverages have always been part of the Mediterranean culture and, lately, they have been re-evaluated to valorize both the territory and local customs. In this study, the Amarena wine, a fortified wine included in the national list of the traditional agri-food products, was characterized during bottle aging for oenological parameters, chromaticity, volatiles, and inorganic elements. Then, experimental data were visually interpreted by a principal component analysis (PCA). PCA revealed that most of oenological parameters (i.e., alcoholic grade, total dry extract, sugars, organic acids, and phenolic compounds) had a scarce discriminating power. Additionally, ethyl esters were only present in younger products, while remaining at quite constant levels. Conversely, certain metals (i.e., Mg, Na, Mn, Zn, and Cu), chromatic properties, and pH differentiated older Amarena bottles from the younger counterpart. Particularly, acetaldehyde and furanic compounds proved to be valid aging markers. A sensorial analysis highlighted that fruity and floral odors and flavors characterized younger beverages, while dried fruity, nutty, and spicy notes were displayed by older products, along with the valuable attribute of “oxidized” typically observed in aged Sherry wines. Overall, this study may encourage the production and commercialization of the Amarena wine, thus preserving the cultural heritage of the Mediterranean area.

The Use of Hanseniaspora occidentalis in a Sequential Must Inoculation to Reduce the Malic Acid Content of Wine

In this study, the impact of the apiculate yeast Hanseniaspora occidentalis as a co-partner with Saccharomyces cerevisiae was investigated in a sequential-type mixed-culture fermentation of Muscaris grape must. As with other fermentation trials using Hanseniaspora strains, a significant increase in ethyl acetate was observed, but most intriguing was the almost complete abolition of malic acid (from 2.0 g/L to 0.1 g/L) in the wine. Compared to the pure S. cerevisiae inoculum, there was also a marked increase in the concentrations of the other acetate esters. Modulation of some of the varietal elements, such as rose oxide, was also observed. This work shows the promising use of H. occidentalis in a mixed-culture must fermentation, especially in the acid modulation of fruit juice matrices.

Genetic, Physiological, and Industrial Aspects of the Fructophilic Non-Saccharomyces Yeast Species, Starmerella bacillaris

Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast species, frequently found in enological ecosystems. Peculiar aspects of the genetics and metabolism of this yeast species, as well as potential industrial applications of isolated indigenous S. bacillaris strains worldwide, have recently been explored. In this review, we summarize relevant observations from studies conducted on standard laboratory and indigenous isolated S. bacillaris strains.

Cultivable microbial ecology and aromatic profile of "mothers" for Vino cotto wine production

The aim of the present study was to assess the cultivable microbiota of "mothers" of Vino cotto collected from production of different years 1890, 1895, 1920, 1975, 2008. A total of 73 yeasts and 81 bacteria were isolated. Starmerella lactis-condensi, Starmerella bacillaris, Hanseniaspora uvarum, Saccharomyces cerevisiae, Hanseniaspora guillermondi and Metschnikowia pulcherrima were identified. Bacteria isolates belonged to lactic acid bacteria (Lactiplantibacillus plantarum and Pediococcus pentosaceus) and acetic acid bacteria (Gluconobacter oxydans). Remarkable biodiversity was observed for Starm. bacillaris, as well as L. plantarum and G. oxydans. Organic acids and volatile compounds were also determined. Malic and succinic acids were the main ones with values ranging from 8.49 g/L to 11.76 g/L and from 4.15 g/L to 7.73 g/L respectively, while citric acid was present at low concentrations (<0.2 g/L) in all samples. Esters and higher alcohols were the main volatile compounds detected followed by alkanes. This study permits to better understand the microbial communities associated to this product and could be considered a starting point for the definition of tailored starter cultures to improve the quality of Vino cotto preserving its typical traits.

Vinification without Saccharomyces: Interacting Osmotolerant and "Spoilage" Yeast Communities in Fermenting and Ageing Botrytised High-Sugar Wines (Tokaj Essence)

The conversion of grape juice to wine starts with complex yeast communities consisting of strains that have colonised the harvested grape and/or reside in the winery environment. As the conditions in the fermenting juice gradually become inhibitory for most species, they are rapidly overgrown by the more adaptable Saccharomyces strains, which then complete the fermentation. However, there are environmental factors that even Saccharomyces cannot cope with. We show that when the sugar content is extremely high, osmotolerant yeasts, usually considered as “spoilage yeasts“, ferment the must. The examination of the yeast biota of 22 botrytised Tokaj Essence wines of sugar concentrations ranging from 365 to 752 g∙L⁻¹ identified the osmotolerant Zygosaccharomyces rouxii, Candida (Starmerella) lactis-condensi and Candida zemplinina (Starmerella bacillaris) as the dominating species. Ten additional species, mostly known as osmotolerant spoilage yeasts or biofilm-producing yeasts, were detected as minor components of the populations. The high phenotypical and molecular (karyotype, mtDNA restriction fragment length polymorphism (RFLP) and microsatellite-primed PCR (MSP-PCR)) diversity of the conspecific strains indicated that diverse clones of the species coexisted in the wines. Genetic segregation of certain clones and interactions (antagonism and crossfeeding) of the species also appeared to shape the fermenting yeast biota.

Changes in the physicochemical components, polyphenol profile, and flavor of persimmon wine during spontaneous and inoculated fermentation

Changes in the oenological parameters, total phenols, total flavonoids, and individual phenols of persimmon during spontaneous and inoculated fermentation were investigated. The volatile compounds and sensory character of the persimmon wine were compared and evaluated simultaneously. Results show that at the end of fermentation, spontaneous persimmon wine (SPW) has higher contents of total flavonoids, total phenols yet lower concentrations of alcohol and volatile compounds than inoculated persimmon wine (IPW). Catechin, salicylic acid, quercetin, and vanillic acid were the main phenolic compounds in both types of persimmon wine. There are six volatile components in the IPW with an OAV greater than 1, which are isoamyl acetate, ethyl hexanoate, methyl octanoate, ethyl octanoate, phenethyl acetate, and 2, 4-di-tert-butylphenol, and these compounds contribute to the IPW with brandy and fruity sensory properties, while only three volatile components in SPW have OAV greater than 1, which are isoamyl acetate, ethyl hexanoate, and ethyl octanoate. Spontaneous fermentation increased the proportion of esters and alcohols in the overall volatile compounds. During sensory evaluation, IPW was characterized by "brandy," "bitterness," and low "sweetness," and SPW has a high score of "sweetness," "balance," desirable "color," and "body."

Vineyard calcium sprays shift the volatile profile of young red wine produced by induced and spontaneous fermentation

Calcium supplements have increasingly been used at pre-harvest stages for improving fruit firmness, aiming at mitigating environmental stress. However, as recent studies demonstrated that calcium modifies the polyphenolic profile of grape berries, we hypothesize in this study that it also affects wine volatile profile. In a two-year study, grapevines cv. "Vinhão" were sprayed with 2% CaCl₂ throughout the fruiting season, and musts were prepared at a laboratory scale. Musts from calcium-treated fruits contained higher calcium levels and less anthocyanins. Increased calcium content did not affect the course of fermentation induced with a S. cerevisiae starter inoculum, but impacted the course of spontaneous fermentations carried out by endogenous berry microflora. Several compounds associated to varietal and fermentative aromas were largely influenced by the calcium treatment. For instance, volatile phenols decreased, together with β-damascenone, benzaldehyde and γ-nonalactone, while several acetates and alcohols increased. Principal component analysis showed that the volatile profile of control wines produced by spontaneous fermentation substantially differed between replicates, but calcium treatment lowered replicate variability. Volatile profiles were also influenced by the vintage and fermentation type. The shift in wine volatile profile upon calcium treatment may be relevant from an oenological perspective.