Higher alcohols and acetate esters belong to the most important yeast secondary metabolites that significantly contribute to the overall flavor and aroma profile of fermented products. In ...Saccharomyces cerevisiae, esterification of higher alcohols is catalyzed mainly by the alcohol acetyltransferases encoded by genes ATF1 and ATF2. Previous investigation has shown other Saccharomyces species, e.g., S. kudriavzevii and S. uvarum, to vary in aroma-active higher alcohols and acetate esters formation when compared to S. cerevisiae. Here, we aimed to analyze the enzymes encoded by the ATF1 and ATF2 genes from S. kudriavzevii (SkATF1, SkATF2) and S. uvarum (SuATF1, SuATF2). The heterologous expression of the individual ATF1 and ATF2 genes in a host S. cerevisiae resulted in the enhanced production of several higher alcohols and acetate esters. Particularly, an increase of 2-phenylethyl acetate production by the strains that harbored ATF1 and ATF2 genes from S. kudriavzevii and S. uvarum was observed. When grown with individual amino acids as the nitrogen source, the strain that harbored SkATF1 showed particularly high 2-phenylethyl acetate production and the strains with introduced SkATF2 or SuATF2 revealed increased production of isobutyl acetate, isoamyl acetate, and 2-phenylethyl acetate compared to the reference strains with endogenous ATF genes. The alcohol acetyltransferase activities of the individual Atf1 and Atf2 enzymes measured in the cell extracts of the S. cerevisiae atf1 atf2 iah1 triple-null strain were detected for all the measured substrates. This indicated that S. kudriavzevii and S. uvarum Atf enzymes had broad range substrate specificity as S. cerevisiae Atf enzymes. Individual Atf1 enzymes exhibited markedly different kinetic properties since SkAtf1p showed c. twofold higher and SuAtf1p c. threefold higher K m for isoamyl alcohol than ScAtf1p. Together these results indicated that the differences found among the three Saccharomyces species during the aroma-active acetate ester formation may be due, to some extent, to the distinct properties of Atf enzymes.
Sulfur dioxide (SO
2
) is probably one of the most versatile and efficient additives used in winemaking due to its antiseptic and antioxidant properties. This compound is also important for ...minimizing phenolic polymerization rate and color loss during wine aging. However, allergies caused by SO
2
-derived compounds, namely the sulfites, are becoming more frequent, causing symptoms such as headaches, nausea, gastric irritation, and breathing difficulties in asthma patients. Consequently, the legislated maximum concentration of SO
2
allowed in wines has been gradually reduced. For this reason, it is crucial in a competitive global winemaking market strategy, to reduce or even eliminate the use of SO
2
as a preservative and to search for new healthier and safe strategies. This work gives an overview of the main methodologies that have been proposed so far and that have potential to be used in winemaking as an alternative to SO
2
. The addition of compounds such as dimethyl dicarbonate, bacteriocins, phenolic compounds, and lysozyme, and the use of physical methods, namely pulsed electric fields, ultrasound, ultraviolet radiation, and high pressure are discussed and critically evaluated.
Introduction
Pectinolytic enzymes are of great importance for the clarification process of “Vinho Verde” wine must, contributing to the reduction of haze development. During the last decade, a ...growing body of knowledge has been established about the effects of electric fields on the activation of important food enzymes. However, the influence of electrical parameters on catalytic activity is enzyme-dependent and should be evaluated on a case-by-case basis. This work describes, for the first time, the effects of electric fields and electrical frequency on the activity of pectinase (PEC) in the accelerated clarification of “Vinho Verde” must.
Method
Moderate electric fields (MEF) with intensities below 20 V/cm and at electrical frequencies ranging from 50 to 20 kHz were applied at temperatures between 15 and 35°C. Enzymatic activity was measured for 25 min, and the initial rate of reaction was determined by the coefficient of the linear plot of galacturonic acid (GAL) production as a function of time.
Results
The results show that electrical frequency can increase enzymatic activity depending on temperature conditions; at 20°C and with electrical frequencies of 2 and 20 kHz, enzymatic activity increased by up to 40 and 20%, respectively, when compared with the control sample (without the application of MEF). Temperature dependence was evaluated through the Arrhenius equation, showing that energy of activation (Ea) can be reduced from 9.2 to 6.6 kJ/mol at sub-optimal temperatures for PEC activity when MEF is applied.
Discussion
Electrical parameters, when combined with temperatures below 20°C, reduced pectin concentration in “Vinho Verde” wine must by up to 42% of its initial content. This emergent treatment can be integrated in relevant environmental conditions, presenting an opportunity to increase enzyme efficiency even in low-temperature conditions, which favors the winemaking process.
This detailed study observed the yeasts present in the ecological niche of “wine must”. The dynamics and identity of non-
Saccharomyces yeasts during the cold maceration and alcoholic fermentation of ...grape must were investigated under real production conditions in the Bordeaux region. Furthermore, we studied the impact of two oenological parameters on the development and diversity of non-
Saccharomyces yeasts during cold maceration: temperature management and the timing of dried yeast addition.
The non-
Saccharomyces community underwent constant changes throughout cold maceration and alcoholic fermentation. The highly diverse non-
Saccharomyces microflora was present at 10
4–10
5 CFU/mL during cold maceration. The population increased to a maximum of 10
6–10
7 CFU/mL at the beginning of alcoholic fermentation, then declined again at the end. The population at this point, evaluated at around 10
3–10
4 CFU/mL, was shown to be dependent on the timing of yeast inoculation. The choice of temperature was the key factor for controlling the total yeast population growth, as well as the species present at the end of cold maceration.
Hanseniaspora uvarum was a major species present in 2005 and 2006, while
Candida zemplinina was very abundant in 2006. A total of 19 species were isolated.
Ochratoxin A (OTA), a mycotoxin classified as a possible human carcinogenic (IARC) is commonly present in cereals, grapes, coffee, species, cocoa and, due to its thermostability, in their ...derivatives. Its extraction from naturally contaminated grape occurs during the initial phase of wine processing, taking place by solid–liquid (berry-juice) contact.
In this paper, the effect of alcoholic fermentation on OTA concentration in must fortified with toxin was studied in presence or not of grape skins and using, as inoculum, two different commercial yeast strains. The OTA concentration was determined both by HPLC-fluorescence detection (HPLC-FL) and RIDASCREEN® Ochratoxin A kit, after immunoaffinity column clean-up. The two methods resulted reliable in the toxin concentration range tested (0.5–15μgkg−1) in red and white wine-musts analyzed. The study proves the detoxifying effect of alcoholic fermentation on OTA level, even if toxin depletion trend, starting within the first two days, is quite constant despite kinetic variability of metabolic phenomena during fermentation process.
OTA adsorption effect of grape skins (5–12%), appeared at beginning or ending of fastest ethanol production phase, seems to be related to skin tissue nature.
Both yeast strains tested, Zymaflor VL3 (Laffort) and VIN7 (Anchor-Lallemand), were able to reduce OTA level (from 57 to 79% of initial amount) during the alcoholic fermentation of red and white wine-must. The greatest detoxifying effect was observed for VIN7 strain.
► Two methods for OTA determination resulted reliable in concentration range 0.5–15ppb. ► Both yeast strains tested reduced OTA level during alcoholic fermentation. ► VIN7 strain presented the greatest detoxifying effect.
Protein stability in bottled white wine is an essential organoleptic property considered by consumers. In this paper, the effectiveness of an early enzymatic treatment was investigated by adding a ...food-grade microbial protease at two different stages of winemaking: (i) at cold settling, for a short-term and low temperature (10 °C) action prior to alcoholic fermentation (AF); (ii) at yeast inoculum, for a long-lasting and medium temperature (18 °C) action during AF. The results reveal that protease sufficiently preserved its catalytic activity at both operational conditions: 10 °C (during cold settling) and 18 °C (during AF). Furthermore, protease addition (dosage 50–150 μL/L) raised the alcoholic fermentation rate. The treatment at yeast inoculum (dosage 50 μL/L) had a remarkable effect in preventing haze formation, as revealed by its impact on protein instability and haze-active proteins. This minimally invasive, time and resource-saving enzymatic treatment, integrated into the winemaking process, could produce stable white wine without affecting color quality and phenol content.
The main goal of this article deals with effect of storage temperature on the partially fermented wine must viscosity. Four samples of partially femrented wine must (Pinot Gris) wre observed. Two ...samples were stored in cold temperature 5 °C and another two samples were stored at the room temperature ~20 °C. The kinematic viscosity has measured for 132 hours from start of stormy fermetation (in the interval about 16 hours). Rotary viscometer with standard spinde and low-volume adapter was used to experimental measured. Results of kinematic viscosity process were mathematically modelled using logarithms function. Created mathematical models were precision because correlation coefficients and values of significance achieved very high values. Results and trends form this article can be used to the partially fermented wine must viscosity process prediction.
Irregularities in grape yields can often affect wine production both quantitatively and qualitatively. Hence concentration systems, such as those based on reverse osmosis, are often employed to ...overcome such problems. The present study illustrates the results of a life cycle assessment approach implemented as means to improve the existing performance and sustainability of a specific industrial reverse osmosis concentration system used in a southern Italian winery to concentrate a specific must. The application of lifecycle approaches to reverse osmosis must concentration is sparsely documented in scientific literature with little or no specific data. The life cycle assessment of this study, developed using large amounts of inventory data and other novel information gathered from industrial testing, has highlighted the use phase as the most impacting one due to the energy consumption during the concentration operations and due to the membrane cleaning operations. In view of these results, the machine setup was improved and tested by varying the feed-flow velocity and the resulting new setup re-assessed via a life cycle approach. The final results exhibit the relationship between permeate production and feed flow velocity that does not appear to have been sufficiently investigated in other work found in literature regarding wine must. Specifically, the curve fitted to the experimental readings indicates that the maximum performance of the reverse osmosis system under analysis is achieved with a feed-flow velocity of approximately 2 m/s. Furthermore the new optimised setup of the machine lowered the environmental profile of all impact categories within a range from a minimum of 25.3% to a maximum of 26.7%, due to lower energy consumption, higher permeate production and reduced cleaning operations for the membranes. Concurrently to the environmental optimisation a technical improvement was identified, namely the substitution of the over-dimensioned piston pump, together with a potential reduction of purchase, running and labour costs of the optimised reverse osmosis system. Overall the study highlights the utility of analysing industrial machinery, such as reverse osmosis must concentration systems, from a life cycle analysis perspective, that can bring about not only environmental sustainability improvements but also technical and economic developments.
This study investigates the recovery of a wine-must aroma profile, formed by Saccharomyces cerevisiae during a muscatel wine-must fermentation, using organophilic pervaporation. Experiments were ...carried out along two independent, but organoleptically similar, fermentations. The wine-must samples and the aroma concentrates obtained were characterized organoleptically by a sensory panel and analytically with regard to eight major wine-must components: four alcohols; three esters; and one monoterpenic compound. Pervaporation performance was studied under fermentation conditions, and the permeate concentration, partial fluxes, and enrichment of the respective compounds were determined. The muscatel wine-must aroma profile was recovered purely and faithful to its origin between wine-must densities of 1075 and 1055 g L. At the beginning of the fermentation, too few aromas were present in the must for recovery. Toward the end of the fermentation, high ethanol concentrations in the wine-must caused a dramatic enrichment of two esters in the permeate, whereas other components investigated seemed unaffected. This shift resulted in an unbalanced aroma. In conclusion, it was shown that organophilic pervaporation can be highly suitable for the continuous recovery of very complex and delicate aromatic profiles produced during microbial fermentation.
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