Starter Strains Research Articles

Effect of grape pomace from red cultivar 'Nero d'Avola' on the microbiological, physicochemical, phenolic profile and sensory aspects of ovine Vastedda-like stretched cheese.

The purpose of this study was to functionalize an ovine stretched cheese belonging to 'Vastedda' typology with red grape pomace powder (GPP) of Nero d'Avola cultivar and to characterize the microbiological, physicochemical, phenolic profile and sensory characteristics of the final cheeses. Before cheeses production, GPP was characterized for its microbiological profile, antibacterial activity and polyphenolic content. No colonies of bacteria and yeasts were detected in the GPP. GPP showed a large inhibition spectrum against spoilage and pathogenic bacteria. Three classes of polyphenolic compounds belonging to flavan-3-ols, flavonol and phenolic acids were identified. Two cheeses [0 and 1% (w w-1 ) of GPP] were produced with pasteurized ewe's milk and commercial starter cultures. Plate counts and randomly amplified polymorphic DNA analysis demonstrated the ability of the starter strains to drive the fermentation process in the presence of GPP. GPP enrichment resulted in an increase of protein, phenolic compounds, sensory traits and reduced fat. GPP addition to cheese represents an optimal strategy for the valorization of winemaking by-products and to obtain polyphenol-enriched cheese. This study allowed to achieve an ovine cheese with specific physicochemical, nutraceutical and sensorial characteristics able to enlarge the functional dairy product portfolio.

Selection of Debaryomyces hansenii isolates as starters in meat products based on phenotypic virulence factors, tolerance to abiotic stress conditions and aroma generation.

Debaryomyces hansenii is a yeast widely used in meat fermentations as starter for the purpose of improving the aromatic quality of the final product. However, it has not been the subject of an extensive study regarding phenotypic characteristics important for starter selection, such as the capacity to grow at abiotic stress conditions occurring during fermentation, the ability to generate desirable aromas and the absence of virulence traits in yeasts. The aim of this study was to screen 60 strains of D. hansenii isolated from assorted foods for their potential application as starters in dry-cured fermented sausages manufacture. The abiotic stress factors tested were low aw and pH and high concentration of salt, acetic acid and lactic acid. The phenotypic virulence traits explored were growth at 37°C, pseudohyphal and biofilm generation, invasiveness and enzymatic activities present in virulent yeasts. The generation of desirable meat aromas was tested in models containing aroma precursors applying an olfactory analysis. A quantitative profiling of stress tolerance was used to test the potential performance of selected strains in meat fermentations. The results demonstrated that most strains displayed no virulence trait or were only positive for biofilm production. Moreover, the strains showed large heterogeneity regarding their tolerance to abiotic stress factors, although most of them could grow at intermediate to high levels of the traits. The sensory analysis was the criteria determining the selection of starter strains. The evaluation of the phenotypic traits demonstrates that D. hansenii is a safe yeast, it is able to tolerate the stress in meat fermentation and it is able to generate desirable aromas. The results of this study confirm the adequacy of selected D. hansenii strains to be applied as starters in meat products.

Probiotic potential of Tetragenococcus halophilus EFEL7002 isolated from Korean soy Meju

BackgroundProbiotic starters can improve the flavor profile, texture, and health-promoting properties of fermented foods. Tetragenococcus halophilus is a halophilic lactic acid bacterium that is a candidate starter for high-salt fermented foods. However, the species is known to produce biogenic amines, which are associated with neurotoxicity. Here, we report a probiotic starter strain of T. halophilus, EFEL7002, that is suitable for use in high-salt fermentation.ResultsEFEL7002 was isolated from Korean meju (fermented soybean) and identified as T. halophilus, with 99.85% similarity. The strain is safe for use in food as it is a non-hemolytic and non-biogenic amine producer. EFEL7002 is tolerant to gastrointestinal conditions and can adhere to Caco-2 cells. This strain showed antioxidant, anti-inflammatory, and protective effects against the human gut epithelial barrier. EFEL7002 grew well in media containing 0–18% NaCl showing maximum cell densities in 6% or 12% NaCl.ConclusionsT. halophilus EFEL7002 can be used as a health-promoting probiotic starter culture for various salty fermented foods.

Screening of Sourdough Starter Strains and Improvements in the Quality of Whole Wheat Steamed Bread.

In this study, yeast, lactic acid bacteria, and acetic acid bacteria were isolated from traditional Chinese sourdough to enhance the organoleptic quality of whole wheat steamed bread. The Saccharomyces cerevisiae, Lactobacillus johnsonii, and Acetobacter pasteurianum showed superior fermentability and acid production capacity when compared with other strains from sourdough, which were mixed to produce the compound starter. It was found that the volume of whole wheat steamed bread leavened with compound starter increased by 12.8% when compared with that of the whole wheat steamed bread made by commercial dry yeast (DY-WB). A total of 38 volatile flavors were detected in the whole wheat steamed bread fermented by the compound starter (CS-WB), and the type of volatile flavors increased by 14 species when compared to the bread fermented by the dry yeast. In addition, some unique volatile flavor substances were detected in CS-WB, such as acetoin, 3-hydroxy-butanal, butyraldehyde, cuparene, etc. Moreover, the hardness and the chewiness of CS-WB decreased by 31.1 and 33.7% when compared with DY-WB, respectively, while the springiness increased by 10.8%. Overall, the formulated compound starter showed a desirable improvement in the whole wheat steamed bread and could be exploited as a new ingredient for steamed bread.

Dynamics of Changes in pH and the Contents of Free Sugars, Organic Acids and LAB in Button Mushrooms during Controlled Lactic Fermentation.

The aim of the study was to assess changes in the basic quality parameters induced by controlled lactic fermentation of fruiting bodies of the button mushroom (Agaricus bisporus). Lactiplantibacillus plantarum 299v with documented probiotic properties and L. plantarum EK3, i.e., an isolate obtained from spontaneously fermented button mushrooms, were used as starter strains. The fruiting bodies of fresh, blanched, and fermented mushrooms were analyzed at different stages of the lactic fermentation process. The content of free sugars (high-performance liquid chromatography with charged aerosol detector method; HPLC-CAD) and organic acids (high-performance liquid chromatography with diode array detector method; HPLC-DAD) was determined both in the mushroom fruiting bodies and in the brine. Five free sugars (ribose, trehalose, sucrose, glucose, and fructose), mannitol, and six organic acids (lactic, malic, succinic, citric, acetic, and fumaric acids) were detected in the samples. Lactic acid dominated in the final products. The starter cultures exhibited varying degrees of utilization of available mushroom sugars and sucrose used as an additional substrate. Sucrose was utilized at a higher rate and in greater amounts by the L. plantarum EK3 isolate. This starter culture was characterized by a significantly higher final amount of produced lactic acid, a lower pH value, and higher numbers of LAB (lactic acid bacteria). These important quality parameters largely determine the stability of fermented products. Based on the analysis results and the high scores in the organoleptic evaluation of the fermented mushrooms, the L. plantarum EK3 isolate can be recommended as an appropriate starter culture for lactic fermentation of mushroom fruiting bodies.

Diversity of indigenous bacteria in fermented dough with Saccharomyces cerevisiae Y10 and Torulaspora delbrueckii Y22

There is a great diversity of indigenous microorganisms in flour, the number of which increased greatly during long-term dough fermentation, affecting dough fermentation and product quality. In this study, the diversity of indigenous bacteria in fermented dough inoculated with single Saccharomyces cerevisiae Y10 strain, Torulaspora delbrueckii Y22 strain and their co-culture was revealed by Illumina MiSeq sequencing. Compared with the dough without yeast inoculation, the bacteria diversity in yeast fermented dough was lower after 12 h fermentation. However, the abundance of lactic acid bacteria (LAB) in the dough inoculated with yeast was higher than that in dough without any yeast inoculated. Similar community structures of bacteria were found in doughs inoculated with different yeast, but their abundance were different. The abundance of the genus Clostridium in doughs inoculated with single S. cerevisiae Y10 was lower than non-inoculated dough, doughs inoculated with T. delbrueckii Y22 and co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 at the same fermentation stage. In comparison with the dough without yeast inoculation, the presence of T. delbrueckii Y22 and the co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 decreased the relative abundance of Staphylococcus, Cronobacter and Enterobacter in fermented dough. Furthermore, the relative abundance of Komagataeibacter increased in the presence of co-culture of S. cerevisiae Y10 and T. delbrueckii Y22. The results of this study suggested that the diversity of indigenous bacteria during dough fermentation was greatly influenced by the starter strain.

Ecological Distribution and Oenological Characterization of Native Saccharomyces cerevisiae in an Organic Winery

The relation between regional yeast biota and the organoleptic characteristics of wines has attracted growing attention among winemakers. In this work, the dynamics of a native Saccharomyces cerevisiae population was investigated in an organic winery. In this regard, the occurrence and the persistence of native S. cerevisiae were evaluated in the vineyard and winery and during spontaneous fermentation of two nonconsecutive vintages. From a total of 98 strains, nine different S. cerevisiae biotypes were identified that were distributed through the whole winemaking process, and five of them persisted in both vintages. The results of the oenological characterization of the dominant biotypes (I and II) show a fermentation behavior comparable to that exhibited by three common commercial starter strains, exhibiting specific aromatic profiles. Biotype I was characterized by some fruity aroma compounds, such as isoamyl acetate and ethyl octanoate, while biotype II was differentiated by ethyl hexanoate, nerol, and β-damascenone production also in relation to the fermentation temperature. These results indicate that the specificity of these resident strains should be used as starter cultures to obtain wines with distinctive aromatic profiles.

Bottle Aging Affected Aromatic and Phenolic Wine Composition More than Yeast Starter Strains

Volatile and phenolic compounds play a key role in the sensory properties of wine, especially aroma and color. During fermentation, yeasts produce enzymes that affect the skin’s phenolic compounds extraction and synthesize some of the most important wine volatile compounds. Generally, selected yeasts of the Saccharomyces cerevisiae (Sc) strains are inoculated, which are responsible for carrying out the wine fermentation, enhancing and highlighting its sensory characteristics and contributing to help achieve the wine typicity, according to the winemaker’s criteria. After fermentation, all wines require aging in a bottle to modulate their composition and stability over time. Thus, four different Sc strains (Sc1–Sc4) were inoculated into tanks with Tempranillo grapes to carry out, in duplicate, their fermentation and subsequent aging in bottles (9 months), comparing the aromatic and phenolic composition between them. Results showed differences in the fermentation process (kinetic, ethanol yield), CI, TPI and content of alcohols, esters, anthocyanins, flavonols and flavanols in wines from the different Sc strains studied. Moreover, in the content in wines of most groups of aromas and phenols, except for total acetate esters and flavonols, aging in a bottle had more influence than the yeast strain used for fermentation.

Revealing the microbial heritage of traditional Brazilian cheeses through metagenomics

Brazilian artisanal cheeses date from the first Portuguese settlers and evolved via local factors, resulting in unique products that are now part of the patrimony and identity of different Brazilian regions. In this study, we combined several culture-independent approaches, including 16S/ITS metagenetics, assembly- and deep profiling-metagenomics to characterize the originality of the microbiota of five varieties of Brazilian artisanal cheeses from the South and Southeast regions of Brazil. Their core microbiota contained mainly lactic acid bacteria (LAB), of which Lactococcus lactis subsp. lactis was the most frequent, followed by Streptococcus thermophilus in the South region. Moreover, several samples from the Southeast region contained, as dominant LAB, two other food Streptococci belonging to a new species of the salivarius group and S. infantarius. Rinds of samples from the Southeast region were dominated by the halotolerant bacterium Corynebacterium variabile, and the yeasts Diutina catenulata, followed by Debaryomyces hansenii and Kodamaea ohmeri. Rinds from the South region contained mainly LAB due to their short ripening time, and the predominant yeast was D. hansenii. Phylogenomic analysis based on L. lactis metagenome-assembled genomes (MAGs) showed that most Brazilian strains are closely related and form a different clade from those whose genomes are available at this time, indicating that they belong to a specific group. Lastly, functional analysis showed that S. infantarius acquired a ∼ 26 kb DNA fragment from S. thermophilus starter strains that carry the LacSZ system, allowing fast lactose assimilation, an adaptation advantage for growth in milk. Finally, our study identified several areas of concern, such as the presence of somatic cell DNA and high levels of antibiotic resistance genes in several cheese microbiota, suggesting that milk from diseased animals may still be used occasionally. Overall, the data from this study highlight the potential value of the traditional and artisanal cheese production network in Brazil, and provide a metagenomic-based scheme to help manage this resource safely.

Streptococcus thermophilus Phages in Whey Derivatives: From Problem to Application in the Dairy Industry.

Fifteen samples of whey protein concentrate (WPC) were tested against 37 commercial Streptococcus thermophilus strains to detect infective bacteriophages. Seventy-three diverse phages were isolated from 12 samples, characterized by using DNA restriction patterns and host range analyses. Sixty-two of them were classified as cos, two as pac, and nine as 5093, according to PCR multiplex assays. Phage concentration was greater than 104 PFU/g for 25.3% of isolated phages. Seven phages showed an unusual wide host range, being able to infect a high number of the tested strains. Regarding thermal resistance, pac phages were the most sensitive, followed by cos phages, those classified as 5093 being the most resistant. Treatments at 85 °C for 5 min in TMG buffer were necessary to completely inactivate all phages. Results demonstrated that the use, without control, of these whey derivatives as additives in dairy fermentations could be a threat because of the potential phage infection of starter strains. In this sense, these phages constitute a pool of new isolates used to improve the phage resistance of starter cultures applied today in the fermentative industry.

Production and characterization of bioactive peptides in novel functional soybean chhurpi produced using Lactobacillus delbrueckii WS4

A novel soy chhurpi product was developed by fermentation of soymilk using proteolytic Lactobacillus delbrueckii strains isolated from traditional chhurpi production of Sikkim Himalaya. Soymilk fermentation by L. delbrueckii WS4 was associated with the hydrolysis of globulin proteins, with observed antioxidant, and ACE-inhibitory activity which further increased upon simulated in vitro gastrointestinal digestion. Peptidomics analysis of soy chhurpi and its gastrointestinal digest resulted in the identification of bioactive peptides with ACE-inhibitory and antioxidant properties. In silico antihypertensive property prediction followed by molecular docking study demonstrated strong binding affinity of selected peptides with ACE. The glycinin-derived peptide, SVIKPPTDE escaped gastrointestinal digestion and demonstrated strong non-bond interactions with ACE catalytic residues. QSAR models predicted an ACE-inhibitory IC50 of 21.29 µM for SVIKPPTDE. This is the first report on the production of novel functional soy chhurpi cheese using defined starter strains and the identification of bioactive peptides in undigested and gastrointestinal digested soy chhurpi.

Genomics divergence of Lactococcus lactis subsp. lactis isolated from naturally fermented dairy products

Lactococcus lactis subsp. lactis (L. lactis subsp. lactis) is commonly found in naturally fermented dairy products (NFDPs). This subspecies is of high economic value due to its wide application in dairy industry. However, the genetic background and evolutionary history of L. lactis subsp. lactis are still poorly understood, analysis of its genetic background and functional genome will lay a genetic foundation for its application. This study analyzed the whole genomes of 227 novel L. lactis subsp. lactis isolated from NFDPs and investigated the genetic history of this subspecies from a population genetic perspective. These strains were classified into four phylogenetically distinct groups, which were likely derived from only a few wild ancestors through three divergence events, resulting in genetic and phenotypic divergence. Functional genomic analysis found that the divergence events caused strong lineage-specific selection for carbohydrate utilization and lactic acid production genes. Moreover, the time of the divergence coincided with mass migration of nomads due to climate change and decrease in average annual temperature, suggesting that these drastic environmental changes might be evolutionary drivers of the divergence. Genome-wide association analysis results showed that the single nucleic acid polymorphic loci we associated with pepF and CoiA genes were significantly correlated with fermentation capability, and based on this, a rapid screening model for potential starter strains was constructed. Our findings shed light on the evolutionary history and genomic diversity of NFDP-originated L. lactis subsp. lactis, and provide a new insight for screening strains with excellent characteristics.

Impact of different sugars and glycosyltransferases on the assertiveness of Latilactobacillus sakei in raw sausage fermentations

Latilactobacillus sakei comprises a biodiversity of strains, which display different assertiveness upon their application as starter cultures in raw sausage fermentation. While the assertiveness of winning partner strains has been referred to competitive exclusion based on genomic settings enabling occupation of multiple niches of the sausage habitat, single strain assertiveness of L. sakei remained unexplained. In this study we assessed the impact of the expression of a glycosyltransferase enabling the production of a glucan from sucrose to the assertiveness of L. sakei TMW 1.411, which expresses a plasmid-encoded glycosyltransferase (gtf). In a sausage fermentation model wild type L. sakei TMW 1.411 and its plasmid-cured mutant were employed in competition with each other and with other Latilactobacillus sakei strains. To differentiate any effects resulting from general sugar utilization from those of glucan formation, the experiments were carried out with glucose, fructose, and sucrose, respectively. It was shown that the type of sugar affects the individual strains behaviour, and that the wild type was more competitive than the mutant in the presence of any of these sugars. In direct competition between wild type and mutant, a clear competitive advantage could also be demonstrated for the strain possessing the plasmid with the glycosyltransferase. Since this competitive advantage was observed with all sugars, not just sucrose, and Gtf expression has been shown as independent of the employed sugar, it is suggested that possession of the gtf gene-carrying plasmid confers a competitive advantage. It appears that the Gtf contributes to competitive exclusion and the establishment of colonization resistance, to a larger extent by an adhesive functionality of the Gtf on the cellular surface than by the production of glucan. Hence, gtf genes can be used as a possible additional marker for the selection of assertive L. sakei starter strains in sausage fermentation.

Elaboration of a Semi-Hard Cheese, ”Gouda” Type, with Autochthonous Strains and Analysis of its Physicochemical and Sensory Composition

Objectives : The technological characteristics and flavour formation capacities of cheeses depend on the starter strains and the ripening conditions. The present study aimed at using autochthonous lactic acid bacteria strains with interesting technological and enzymatic properties, suitable as starter cultures to produce semi-hard cheese, such as Gouda, based on pasteurized cow’s milk. Methods: This study allowed the formulation of local lactic ferments, with autochthonous strains; thanks to which we have made a semi-hard cheese, Gouda type, made from pasteurized cow’s milk. Physicochemical (dry matter, fat, protein, chloride, and ash) and organoleptic (texture, color, taste, odor, aroma) analysis were carried out. Findings: The protein composition is very important (average value of 24.18  0.46g / 100g). The results of the sensory analysis did not show any defects in the cheese studied. The taste is sweet, characteristic; the aroma is pure, pleasant, well developed. The color is uniform yellowish, the rind is dry. Novelty: The use of pasteurized milk and autochthonous lactic ferments have helped maintain the typical characteristics of the cheeses. Keywords: Cheese; Gouda; Lactic ferment; physicochemical analysis; Semihard paste; Sensory analysis

Studies on cellulases of some cellulose-degrading soil fungi.

In this study, novel cellulolytic fungal strains were isolated, purified, and identified. The ability of these isolates to biodegrade cellulosic materials was examined. The potential of the isolates to produce cellulolytic enzymes and optimize the cellulose degradation process was also investigated. The nylon net bag technique was used to separate cellulose-degrading fungi from soil. A total of 37 species were isolated and tested for their capacity to break down rice straw as a cellulose source. Qualitative assays for cellulase were carried out by Congo red plate assay, while quantitative assays were carried out using the dinitrosalicylic acid (DNS) method at 546nm. Following morphological and molecular identification, the isolates that exhibited the highest cellulase activities were identified as Neurospora intermedia (Assiut University Mycological Center (AUMC) 14359), Fusarium verticillioides (AUMC 14360), and Rhizopus oryzae (AUMC 14361). For N. intermedia, the optimal conditions for maximum activity were a 2% carboxymethylcellulose (CMC) concentration, beef extract and peptone as nitrogen sources, pH 7, 30°C, and an inoculum size of 2.5 (v/v). For F. verticillioides, the optimal conditions were 2.5% CMC concentration, yeast extract as a nitrogen source, pH 6, 30°C, and an inoculum size of 2 (v/v). For R. oryzae, the optimal conditions were 2% CMC concentration, beef extract as a nitrogen source, pH 7, 30°C and an inoculum size of 2.5 (v/v). The identified strains represent new starter strains with high efficiency under optimum conditions for prospective large-scale application in cellulose degradation and nanocellulose production-dependent water purification.

Characterization of native lactic acid bacteria from traditionally fermented chhurpi of Sikkim Himalayan region for the production of chhurpi cheese with enhanced antioxidant effect

Lactic acid bacteria (LAB) were isolated and characterized from chhurpi, a traditionally produced cheese product of Sikkim Himalaya. Enterococcus durans was the most dominant LAB making up 34% of the identified LAB, followed by Lactobacillus delbrueckii (25%). Chhurpi was produced using milk curdling LAB strains followed by simulated in vitro gastrointestinal digestion of chhurpi. Evaluation of protein hydrolysis and antioxidant activity was performed. Chhurpi produced using Lactobacillus delbrueckii WS4 had a relatively higher yield (10.4%), protein hydrolysis, and antioxidant activity as compared to other starter strains (P < 0.05). Gastrointestinal digestion of chhurpi increased the antioxidant activity, with the highest activity observed for gastrointestinal digests of chhurpi produced by using Lb. delbrueckii WS4. The EC50 for DPPH radical scavenging activity of chhurpi produced by using Lb. delbrueckii WS4 was observed to decrease significantly (from 239.16 to 48.87 mg sample/ml) after digestion with pepsin and pancreatin (P < 0.05). Protein hydrolysis and antioxidant activity in whey were comparable to that of chhurpi, indicating the potential of using the chhurpi whey to develop nutraceuticals. This is the first report on evaluating the antioxidant activity of chhurpi produced using defined LAB strains and the effect of gastrointestinal digestion on chhurpi functionality.

Microbial Exopolysaccharides in Traditional Mexican Fermented Beverages

Exopolysaccharides (EPS) are biopolymers produced by many microorganisms, including some species of the genus Acetobacter, Bacillus, Fructobacillus, Leuconostoc, Lactobacillus, Lactiplantibacillus, Pediococcus, Pichia, Rhodotorula, Saccharomycodes, Schizosaccharomyces, and Sphingomonas, which have been reported in the microbiota of traditional fermented beverages. Dextran, levan, glucan, gellan, and cellulose, among others, are EPS produced by these genera. Extracellular biopolymers are responsible for contributing to specific characteristics to fermented products, such as modifying their organoleptic properties or contributing to biological activities. However, EPS can be easily found in the dairy industry, where they affect rheological properties in products such as yogurt or cheese, among others. Over the years, LAB has been recognized as good starter strains in spontaneous fermentation, as they can contribute beneficial properties to the final product in conjunction with yeasts. To the best our knowledge, several articles have reported that the EPS produced by LAB and yeasts possess many both biological and technological properties that can be influenced by many factors in which fermentation occurs. Therefore, this review presents traditional Mexican fermented beverages (tavern, tuba, sotol, and aguamiel) and relates them to the microbial EPS, which affect biological and techno-functional activities.

Limosilactobacillus fermentum MG7011: An Amylase and Phytase Producing Starter for the Preparation of Rice-Based Probiotic Beverages.

The goal of this study was to develop a starter strain of Limosilactobacillus fermentum which is beneficial for human health and suitable for rice fermentation. To achieve the goal, the characteristics of 25 strains of L. fermentum were compared in terms of health promoting potentials and rice fermenting abilities. L. fermentum MG7011 was selected as a superior strain to meet the required properties. First, as probiotic traits, the strain had tolerance to gastrointestinal conditions and ability to adhere to Caco-2 and HT-29 cells. The strain showed the antioxidative activity, anti-inflammatory activity, and a protective effect on the epithelial barrier. Next, as starter traits for rice fermentation, MG7011 exhibited proper fermentation profiles in rice solution, such as fast growth rate, pH and metabolite changes, amylase and phytase activities, and optimal viscosity changes for beverage. In conclusion, L. fermentum MG7011 has excellent probiotic activities and proper starter traits in rice, thereby it can be used as a suitable probiotic starter for rice fermentation.

Effects of different yeast strains, nutrients and glutathione-rich inactivated yeast addition on the aroma characteristics of Catarratto wines

Catarratto is one of the most common non-aromatic white grape varieties cultivated in Sicily (Southern Italy). In order to improve the aromatic expression of Catarratto wines a trial was undertaken to investigate the effect of yeast strain, nutrition and reduced glutathione. Variables included two Saccharomyces cerevisiae strains, an oenological strain (GR1) and one isolated from honey by-products (SPF52), three different nutrition regimes (Stimula Sauvignon Blanc™ (SS), Stimula Chardonnay™ (SC) and classic nutrition practice), and a specific inactivated yeast rich in reduced glutathione to prevent oxidative processes [Glutastar™ (GIY)] ensuing in ten treatments (T1-T10).Microbiological and chemical parameters demonstrated the aptitude of strain SPF52 to successfully conduct alcoholic fermentation. During fermentation, the Saccharomyces yeast populations ranged from 7 to 8 logarithmic CFU/mL. All wines had a final ethanol content ranging between 12.91 and 13.85% (v/v). The dominance of the two starter strains over native yeast populations was higher than 97% as estimated by interdelta analysis. The addition of nutrients SS or SC increased the aromatic complexity of the wines as reflected by volatile organic compounds (VOCs) composition and sensory profiles. In particular, 32 VOCs were identified; alcohols (62.46–81.1%), thiols (0.27–0.87%), ethers (0.09–0.16%), aldehydes (0–1.21%), ketones (0–2.28%), carboxylic acids (4.21–12.32%), esters (0–10.85%), lactones (0.9–1.49%) and other compounds (0.77–6.9%). Sensory analysis demonstrated a significant impact on wine aroma in relation to yeast starter strain used, the type of nutrition (SS, SC or classic nutrition) and the presence/absence of GIY. The wines produced with GR1 yeast strain and SS (T2), SPF52 with SC (T9) both in presence of GIY showed higher overall quality. Trials T2 and T9 showed the highest scores for 13 and 18 attributes, respectively. The different nutrition, addition of GIY and the yeast starter strains diversified and enhanced sensory expression of Catarratto wines.

Biotechnological exploitation of Saccharomyces jurei and its hybrids in craft beer fermentation uncovers new aroma combinations

Hybridisation is an important evolutionary mechanism to bring about novel phenotypes and may produce new hybrids with advantageous combinations of traits of industrial importance. Within the Saccharomyces genus, Saccharomyces jurei is a newly discovered species and its biotechnological potential has not yet been fully explored. This yeast was found to be able to grow well in unhopped wort and at low temperatures, qualities necessary in good candidates for fermented bevarages. Here, we analysed its fermentation and aroma profile and created novel non-GMO hybrids between S. jurei and S. cerevisiae ale yeasts to develop new starter strains with interesting flavours for the craft brewing and beverage industry in general. Pilot beer fermentations with specific hybrids showed a good fermentation performance, similar to the ale parent strain, while eliminating the hyper-attenuation characteristic and a more complex flavour profile. This study exploits the genetic diversity of yeasts and shows how inter-specific hybridisation and clone selection can be effectively used in brewing to create new products and to eliminate or increase specific traits.