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Investigation about new concepts of yeast derivatives for winemaking with enhanced antioxidant properties and polysaccharides content
Full text linkI derivati di lievito vengono utilizzati nell’industria enologica allo scopo di arricchire il vino in sostanze colloidali, in particolare polisaccaridi e molecole antiossidanti, e di migliorarne la stabilità nel corso dell’affinamento. Questi prodotti sono ottenuti a partire da biomasse di lievito sottoposte a trattamenti termici o enzimatici, e spesso caratterizzati dalla presenza di sostanze (per es., pirazine, acidi grassi e composti aromatici) che, rilasciate nel vino, possono causare la comparsa di off-flavor. Inoltre, i ceppi attualmente autorizzati per la produzione di derivati appartengono al genere Saccharomyces spp.
Nella presente tesi di dottorato, l’obiettivo è stato quello di produrre derivati di lievito innovativi per scopi enologici, caratterizzati da una migliore composizione chimica, maggiore attività antiossidante e minore impatto sensoriale, a partire da ceppi non-Saccharomyces, mediante l’impiego di tecnologie emergenti, non-termiche.
Tra diversi ceppi di lievito non-Saccharomyces, isolati da mosto e vinacce, Hanseniaspora spp. ha mostrato una buona attitudine alla produzione di composti di interesse enologico - colloidi solubili e antiossidanti - con buone potenzialità di impiego come co-starter di fermentazione, per il miglioramento delle caratteristiche del vino durante l’affinamento o per la produzione di derivati.
Tra i parametri di processo valutati nel presente studio, diverse condizioni di crescita hanno determinato una diversa produzione di biomassa e un differente rilascio di molecole antiossidanti e colloidi solubili sia in fase di crescita che dopo lisi indotta, con risultati interessanti ottenuti ancora una volta da Hanseniaspora spp.
Sia il lievito di partenza che i trattamenti applicati per indurre l’autolisi hanno influenzato la composizione chimica dei derivati di lievito con interessanti risultati ottenuti utilizzando Pichia spp. e Torulaspora spp.; le tecnologie emergenti come l’alta pressione idrostatica e gli ultrasuoni sono apparse delle valide alternative ai metodi convenzionali per la produzione di derivati (trattamento termico e lisi enzimatica). In fase di affinamento di un vino bianco, l’aggiunta di derivati di lievito ha consentito una buona protezione nei confronti dell’ossidazione e una buona evoluzione del colore dopo sei mesi di contatto, in confronto ai controlli solfitati; vini addizionati con derivati ottenuti per via enzimatica e mediante ultrasuoni hanno mostrato una maggiore caratterizzazione aromatica, mentre derivati ottenuti mediante trattamento termico e alta pressione idrostatica hanno determinato un profilo aromatico più povero nei rispettivi vini.
L’impatto dei lieviti non-Saccharomyces è stato valutato anche in condizioni di vinificazione. Un ceppo selezionato di Hanseniaspora spp. è stato utilizzato come co-starter di fermentazione, al fine di valutarne l’impatto al termine del processo fermentativo e, soprattutto, in fase di affinamento. L’impiego di fecce ottenute da fermentazione sequenziale ha consentito un miglioramento della composizione chimica - con un maggiore rilascio di polisaccaridi (mannani) e molecole antiossidanti - una buona protezione nei confronti dell’ossidazione, un miglioramento del profilo aromatico e sensoriale del vino, in condizioni reali di vinificazione.
Infine, è stata valutato il potenziale uso dei derivati di lievito per l’alimentazione umana; è stata osservata una certa bioattività, soprattutto in termini di proprietà antiossidanti ed effetto ipolipidemico, rendendo tali prodotti potenzialmente utilizzabili come ingredienti nella preparazione di cibi funzionali o come integratori alimentari.Yeast derivatives are used in winemaking for enriching wine in colloidal substances, polysaccharides and antioxidant molecules, and for improving wine stability during aging. Currently, these products are produced starting from yeast biomass subjected to thermal or enzymatic treatments and often characterized by the presence of compounds (i.e., pyrazines, fatty acids, odor active compounds) that may lead to the appearance of off-flavors when released into the wine. In addition, the only strains currently authorized for yeast derivatives production belong to Saccharomyces spp.
The aim of the present research project was to produce innovative yeast derivatives for winemaking use, characterized by better chemical composition, high antioxidant properties and low odor impact, starting from non-Saccharomyces strains, by non-thermal approach.
Among different spontaneous non-Saccharomyces strains, isolated from grape must and pomace, Hanseniaspora spp. has showed a good aptitude to produce compounds of enological interest – soluble colloids and antioxidant compounds – with potential use as fermentation co-starter, for improving wine aging on lees or for yeast derivatives production.
Among the processing parameters evaluated in the present study, different growth conditions have differently impacted on biomass production and release of antioxidant molecules and soluble colloids, both after growth and induced lysis, with interesting results obtained once again by Hanseniaspora spp.
Both strain and treatment for inducing yeast autolysis have also affected the chemical composition of derivatives, with interesting results obtained by Pichia spp. and Torulaspora spp.; emerging, non-thermal technologies – high hydrostatic pressure and ultrasounds – have seemed to be good alternatives to traditional methods for producing yeast derivatives (thermal inactivation and enzyme addition). During wine aging, the addition of yeast derivatives has allowed a good protection against wine oxidation and good wine color evolution after six months, compared to sulfite samples; wines added with derivatives obtained by enzyme addition and ultrasounds have showed the most characterized volatile profile, whereas the addition of derivatives obtained by thermal inactivation and high hydrostatic pressure have determined the poorest volatile profile in the respective added wines.
The impact of non-Saccharomyces yeasts has also been evaluated under winemaking conditions. Selected strain of Hanseniaspora spp. has been used as fermentation co-starter in order to assess its impact during alcoholic fermentation and, above all, during aging on lees. The use of lees from sequential fermentation has allowed to improve the chemical composition of wine - with highest release of soluble colloids (mannan) and antioxidant compounds - together with good protection against oxidation and an improved volatile and sensory profile under real winemaking conditions.
Lastly, the potential use of yeast derivatives for human nutrition has also evaluated; a certain bioactivity was observed, especially concerning antioxidant properties and hypolipidemic effect, potentially making them suitable as ingredients for functional foods preparation or dietary supplements
Characterization of Non-Saccharomyces Yeast Strains Isolated from Grape Juice and Pomace: Production of Polysaccharides and Antioxidant Molecules after Growth and Autolysis
Full text linkNon-Saccharomyces yeasts (NSY) represent a relevant part of must and wine microbiota, contributing remarkably to the composition of lees biomass. Despite a number of studies indicate their capacity to increase wine polysaccharide content, their contribution to wine quality during aging on lees (AOL) has not been well elucidated yet. In the present study, twenty yeast strains (13 non-Saccharomyces and 7 Saccharomyces) were isolated from grape must and pomace and identified by morphologic and genetic characterization. Biomass production, cell growth and the release of soluble molecules (polysaccharides, amino acids, thiol compounds and glutathione) were evaluated after growth and after autolysis induced by β-glucanases addition. Differences between strains were observed for all parameters. Strains that produced higher amounts of soluble compounds during growth also showed the highest release after autolysis. Hanseniaspora spp. showed the greatest production of polysaccharides and antioxidant molecules, and biomass production and cell viability comparable to the commercial S. cerevisiae and T. delbrueckii used as reference. The aptitude of certain NSY to release antioxidants and polysaccharides is an interesting feature for managing AOL through sequential or mixed fermentations or for the production of inactive autolyzed yeasts for winemaking
Effect of a yeast autolysate produced by high pressure homogenization on white wine evolution during ageing
Full text linkThe enological characteristics and the performances of a yeast autolysate produced by high pressure homogenization (HPH-YD) were investigated for the first time in white wine and model solution, in comparison with a thermolysate (T-YD) and a commercial yeast derivative (COMM). In wine-like medium, HPH-YD showed a significant release of glucidic colloids (on average, slightly higher than the other products), also leading to a greater glutathione solubilization with respect to T-YD. Concerning the volatile composition of the autolysates, HPH-YD was characterized by the highest concentration of alcohols and esters, while showing an average amount of fatty acids, carbonyls and heterocyclic compounds lower than COMM. These features are potentially linked to a more favorable impact of this product on the composition of wine aroma, should these compounds be released into the wine itself. HPH-YD determined minor modifications on wine volatile profile when added for short contact times, without releasing unwanted compounds and with a slightly lower binding capacity towards wine esters. The effects of the three yeast derivatives (YDs) on wine color during ageing was also investigated in comparison with sulfur dioxide (SO2). HPH-YD was the most efficient preparation, limiting wine color changes due to oxidation during four months and behaving more similarly to SO2. The use of HPH for the production of yeast autolysates for winemaking may represent an interesting alternative to thermal treatments, improving the enological characteristics of these additives, particularly their antioxidant capacity, leading anyhow a significant release of colloidal molecules and a limited impact on wine aroma composition
Exploring an eco-friendlier strategy for chitosan production and valuable compounds recovery from mushroom by-products with modified subcritical water
No full textChitosan is the deacetylated derivative of chitin, the second most abundant polysaccharide in nature. It is a
promising eco-friendly polymer with immense potential owing to its unique properties and high versatility,
offering notable contributions to various industries. Conventionally, chitosan is recovered from several biomasses, primarily from marine sources, using chemical or biological methods. Subcritical water (SCW) extraction is a promising sustainable and innovative technology that can address the main drawbacks of conventional methods. This study explores the use of SCW to extract chitosan from mushroom (Pleurotus ostreatus) by-products, considering different temperatures (120 ◦C, 150 ◦C and 180 ◦C) and malic acid concentrations (0 %, 5 % and 10 %). The highest chitosan yield (6.26 % ± 0.09 %) was achieved with SCW at 120 ◦C and 10 % (w/v) of malic acid, which is 4.8 times higher than that of conventional methods. SCW modified the polymer’s structure, which may have influenced its functionality. A partial deacetylation of chitin, as indicated by a 20 % decrease in acetylation degree, and a decrease in the crystallinity index were highlighted. In addition, the remarkable simultaneous recovery of valuable compounds in liquid residues was achieved, attributed to the hydrolysis mechanisms facilitated by SCW
Effetto della permeabilità della chiusura e di diverse variabili ambientali sull'evoluzione di vini bianchi in bottiglia
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Emerging biotechnologies and non-thermal technologies for winemaking in a context of global warming
Full text linkIn the current situation, wine areas are affected by several problems in a context of global warming: asymmetric maturities, pH increasing, high alcohol degree and flat wines with low freshness and poor aroma profile. The use of emerging biotechnologies allows to control or manage such problems. Emerging non-Saccharomyces as Lachancea thermotolerans are very useful for controlling pH by the formation of stable lactic acid from sugars with a slight concomitant alcohol reduction. Lower pH improves freshness increasing simultaneously microbiological stability. The use of Hanseniaspora spp. (specially H. vineae and H. opuntiae) or Metschnikowia pulcherrima promotes a better aroma complexity and improves wine sensory profile by the expression of a more complex metabolic pattern and the release of extracellular enzymes. Some of them are also compatible or synergic with the acidification by L. thermotolerans, and M. pulcherrima is an interesting biotool for reductive winemaking and bioprotection. The use of bioprotection is a powerful tool in this context, allowing oxidation control by oxygen depletion, the inhibition of some wild microorganisms, improving the implantation of some starters and limiting SO2. This can be complemented with the use of reductive yeast derivatives with high contents of reducing peptides and relevant compounds such as glutathione that also are interesting to reduce SO2. Finally, the use of emerging non-thermal technologies as Ultra High-Pressure Homogenization (UHPH) and Pulsed Light (PL) increases wine stability by microbial control and inactivation of oxidative enzymes, improving the implantation of emerging non-Saccharomyces and lowering SO2 additions
Potential of High Pressure Homogenization for the production of yeast autolysates for winemaking
No full textYeast derivatives (YDs – e.g. inactive dry yeasts and yeast autolysates) are extensively used in winemaking for a wide series of applications: fermentation enhancers, flavor and aroma modulators, scavengers against undesired compounds and antioxidant preparations. Their ability in releasing soluble compounds and macromolecules suggests their potential application to simulate the traditional practice of ageing on the lees. Nevertheless, one of the problems connected with the use of such additives during wine ageing is that they may be responsible of the release off-odors into the wine. These compounds are mostly originated from the development of Maillard reaction or lipid oxidation, during the thermal treatments applied for YDs manufacturing. Thus, the development of non-thermal alternative processes for the obtainment of such products may open new opportunities for the production of commercial preparations, specifically tailored for winemaking use. High pressure homogenization (HPH) is a mechanical processing method, used since 1970s to promote the extraction of intracellular components from microorganisms, including Saccharomyces spp. The ability of HPH to induce cell breakdown is connected with different phenomena (i.e. turbulence, cavitation and shear), occurring when a yeast suspension is forced through the homogenization valve. In the present study, HPH was tested in different conditions (pressure, number of passes) and temperature regimes (controlled vs. uncontrolled), concerning its potential application for the production of yeast autolysates. The performances of this technology were assessed on a commercial strain of Saccharomyces bayanus for winemaking. The autolysates obtained were characterized for their ability to release soluble molecules (e.g. proteins and free amino acids) and glucidic colloids (e.g. glycoproteins) in wine-like medium, for the number of viable cells after the treatment, as well as for their composition regarding volatile compounds, in comparison with both thermolysis and a commercially available YD preparation. HPH demonstrated its capacity in promoting yeast autolysis in a short time and without intensive heating. The release of glucidic colloids increased by increasing the pressure applied and the number of passes and was comparable, or slightly higher, respect to the amounts detected in both thermolysates and the commercial YD preparation. HPH processing variables affected the volatile composition of the final products and their content in amino acids and colloids: in particular, the choice to control or not the processing temperature may allow to obtain autolysates with different characteristics, and suitable for different winemaking applications (i.e. fermentation enhancers or ageing supplements). Compared to thermal treatment, HPH was less effective in promoting Saccharomyces bayanus inactivation. The autolysates produced by HPH showed a more interesting volatile composition, with respect to those obtained by thermolysis, because of the higher content of ethyl esters
Application of multi-pass high pressure homogenization under variable temperature regimes to induce autolysis of wine yeasts
Full text linkThe effects of the number of passes and processing temperature management (controlled vs. uncontrolled)
were investigated during high pressure homogenization-induced autolysis of Saccharomyces
bayanus wine yeasts, treated at 150 MPa. Both variables were able to affect cell viability, and the release
of soluble molecules (free amino acids, proteins and glucidic colloids), but the effect of temperature was
more important. S. bayanus cells were completely inactivated in 10 passes without temperature control
(corresponding to a processing temperature of 75 C). The two processing variables also affected the volatile
composition of the autolysates produced: higher temperatures led to a lower concentration of volatile
compounds. The management of the operating conditions may allow the compositional characteristics of
the products to be modulated, making them suitable for different winemaking applications
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