Fermented Honey and Manna Ash Products: Novel Ecological Niches of Wine Yeasts

The selection of novel strains of yeasts is still relevant to improve flavour of wines produced around the word. Several food niches have not been microbiologically investigated and they might represent important sources of microorganisms with technological aptitudes, e.g. in wine industry. To this purpose, two novel yeast communities associated with matrices rich in carbohydrates and characterized by low levels of water activity (aw), such as fermented honey by-products (FHP) and “Manna” ash products (MAP) extracted from Fraxinus angustifolia (Oleaceae), were investigated. FHP contain mainly fructose and glucose, while MAP ash is mainly characterized by high concentrations of mannitol, fructose and mannotriose. The values of aw of both matrices is around 0.5-0.6. Yeasts were isolated, subjected to the genotypic identification and then technologically characterized to evaluate their oenological potential. The species Lachancea fermentati, Pichia anomala, Pichia kudriavzevii, Saccharomyces cerevisiae, Wickerhamomyces anomalus, Zygosaccharomyces bailii and Zygosaccharomyces rouxii were genetically identified from FHP samples. During the spontaneous alcoholic fermentation, the dominating species were S. cerevisiae, Z. bailii and Z. rouxii whose feed conversion ratio of sugars into ethanol was about 53%. On the other hand, MAP was characterized by the presence of Candida aaseri, Candida lactis-condensi, Citeromyces matritensis, Lachancea thermotolerans, Saccharomyces cerevisiae and Zygosaccharomyces bailii. Interestingly, both matrices showed the presence of S. cerevisiae at consistent levels and a high number of L. thermotolerans strains were isolated from MAP. Both species have interesting eonological potential. Six strains of S. cerevisiae were tested as starters to ferment grape must from Grillo, Catarratto and Chardonnay cultivars at industrial winery-scale over two consecutive years. Interestingly, four strains isolated from FHP showed a fructophilic potential and the experimental wines were characterized by an intense floral flavour. Among non-Saccharomyces yeasts, L. thermotolerans strains showed resistance to ethanol up to 12-13 % (v/v) and ability to ferment grape must with a feed conversion ratio of sugars into ethanol of about 45-55%. Eonological potential was showed by C. lactis-condensi and C. aaseri since a high content of glycerol was produced at the end of alcoholic fermentation and a fructophilic aptitude was found. In conclusions, the present research provided novel microbiological and physicochemical insights on the alcoholic fermentation conducted by novel starters belonging to S. cerevisiae and L. thermotolerans species and, for the first time, the species C. lactis-condensi and C. aaseri were found to be of relevance for wine application

Biotechnological innovations in fermentation process of brewing and honey-based beverages industry

La ricerca di microrganismi fermentanti in grado di migliorare le proprietà microbiologiche, fisiche, chimiche, sensoriali e organolettiche delle bevande alcoliche fermentate come vino, birra, idromele, sidro, è considerata ad oggi un punto chiave per lo sviluppo del settore. Negli ultimi anni, l'aumento della domanda al consumo di nuove bevande fermentate ha causato un enorme bisogno di tecnologie di produzione innovative al fine di ottenere diverse tipologie di prodotti caratterizzati da proprietà sensoriali peculiari. Per raggiungere tale obiettivo, l’impiego di nuovi microrganismi, sia fermentanti che non fermentanti, in grado di conferire al prodotto caratteristiche organolettiche peculiari ed uniche, può rappresentare una valida alternativa ai classici ceppi attualmente in commercio. Il settore vitivinicolo-enologico risulta quello in cui la ricerca ha sviluppato conoscenze sufficienti ad applicare nuove specie e nuovi ceppi di lieviti su scala industriale. La ricerca di lieviti non convenzionali applicabili alle bevande alcoliche che nell’Europa meridionale sono considerate secondarie rispetto al vino, ovvero birra, sidro ed idromele, risulta essere ancora poco investigata, essendo scarsi gli studi disponibili sulla fermentazione di queste bevande. In particolare, il settore birrario sta riscoprendo un rinnovato interesse nei confronti di lieviti isolati da matrici territoriali, considerati responsabili del miglioramento e della creazione di bouquet particolari, che consentono di ottenere produzioni legate al territorio e differenziate su un mercato in forte espansione. Analogamente alla produzione di birra artigianale, la produzione di idromele sta attualmente vivendo un interesse a livello amatoriale e professionale in tutto il mondo. Sebbene non sia una bevanda molto popolare, il suo consumo in Europa è in costante crescita. Anche in questo settore la letteratura scientifica risulta limitata, specialmente in ambito microbiologico, dato che per condurre le fermentazioni alcoliche sono spesso usati ceppi di S. cerevisiae di origine enologica. Diversamente dal mosto d’uva, il mosto-miele risulta carente in fattori nutrizionali che limitano la crescita microbica. Per tale motivo, la ricerca di lieviti appropriati in grado di crescere e fermentare queste matrici risulta essere un punto cruciale per mantenere un elevato standard qualitativo di questa bevanda. Sulla base di queste premesse, durante il triennio di Dottorato di ricerca è stata condotta uno studio inerente: l’ecologia microbica di matrici zuccherine; l’isolamento, la caratterizzazione genotipica e tecnologica di lieviti, sia Saccharomyces che non-Saccharomyces; la loro applicazione, sia singolarmente che in combinazione, durante le fermentazioni sperimentali di mosto di birra e mosto-miele; la valutazione della cinetica di fermentazione, metaboliti secondari, composti organici volatili ed analisi sensoriale dei prodotti ottenuti

Influence of salt of different origin on the microbiological characteristics, histamine generation and volatile profile of salted anchovies (Engraulis encrasicolus L.)

The effect of six salts of different geographical areas on the quality of salted anchovies was evaluated. The crude salts were chemically characterized by determination of inorganic and volatile organic compounds (VOCs). Salted anchovies, corresponding to six experimental trials, were subjected to microbiological, chemical (including histamine content) and sensory analysis during the entire period of ripening (150 days). The salts were characterized by marked differences in terms of major cations and trace element amounts. Among the 27 VOCs detected, octadecane was the most abundant compound and the main differences of the salts were registered for alkanes and alcohols. During maturation, significant microbiological differences between the salts were found for the levels of total aerobic mesophilic microorganisms, lactic acid bacteria, Staphylococcaceae and Enterobacteriaceae counts. All salted anchovies contained histamine below the thresholds allowed by current regulations, but statistical differences were registered for the concentrations of the different trials. Consistent differences were also revealed for their sensory profiles, in particular concerning odour and taste and overall acceptability. Several differences were also detected for dryness, brown colour, putrid odour, rancid and raw blood taste sensory attributes. Especially the differences in the composition (chemical and VOC's) of the raw salts used for the production of salted anchovies has a significant effect on the sensory characteristics of the final product

Ricerca di lieviti autoctoni per migliorare il profilo aromatico delle birre artigianali

In corso d’opera un’analisi di matrici appartenenti a diverse nicchie ecologiche con l’obiettivo di individuare lieviti dalle caratteristiche tecnologiche e qualitative ottimal

Improving the Aromatic Profiles of Catarratto Wines: Impact of <i>Metschnikowia pulcherrima</i> and Glutathione-Rich Inactivated Yeasts

Catarratto is one of the most widely cultivated grape varieties in Sicily. It is an indigenous non-aromatic white grape variety. Despite its widespread use in winemaking, knowledge of the aroma and chemical and microbiological properties of Catarratto wines is quite limited. The influence of Metschnikowia pulcherrima combined with Saccharomyces cerevisiae on the aromatic expression of Catarratto wines was investigated with and without the addition of glutathione-rich inactivated yeast. The substance is a natural specific inactivated yeast with a guaranteed glutathione level used to limit oxidative processes. The aromatic profiles of the final wines were determined through analysis of the volatile organic compounds using a solid-phase microextraction technique that identified 26 aromatic compounds. The addition of M. pulcherrima in combination with the natural antioxidant undoubtedly increased the aromatic complexity of the wines. Dodecanal was exclusively detected in the wines processed with glutathione-rich inactivated yeasts. Furthermore, the presence of this natural antioxidant increased the concentration of six esters above the perception threshold. Sensory analysis was also performed with a panel of trained judges who confirmed the aromatic differences among the wines. These results suggest the suitability of glutathione-rich inactivated yeasts for determining the oxidative stability of Catarratto wines, thus preserving its aromatic compounds and colour

Improving the Aromatic Profiles of Catarratto Wines: Impact of Metschnikowia pulcherrima and Glutathione-Rich Inactivated Yeasts

Catarratto is one of the most widely cultivated grape varieties in Sicily. It is an indigenous non-aromatic white grape variety. Despite its widespread use in winemaking, knowledge of the aroma and chemical and microbiological properties of Catarratto wines is quite limited. The influence of Metschnikowia pulcherrima combined with Saccharomyces cerevisiae on the aromatic expression of Catarratto wines was investigated with and without the addition of glutathione-rich inactivated yeast. The substance is a natural specific inactivated yeast with a guaranteed glutathione level used to limit oxidative processes. The aromatic profiles of the final wines were determined through analysis of the volatile organic compounds using a solid-phase microextraction technique that identified 26 aromatic compounds. The addition of M. pulcherrima in combination with the natural antioxidant undoubtedly increased the aromatic complexity of the wines. Dodecanal was exclusively detected in the wines processed with glutathione-rich inactivated yeasts. Furthermore, the presence of this natural antioxidant increased the concentration of six esters above the perception threshold. Sensory analysis was also performed with a panel of trained judges who confirmed the aromatic differences among the wines. These results suggest the suitability of glutathione-rich inactivated yeasts for determining the oxidative stability of Catarratto wines, thus preserving its aromatic compounds and colour

Use of sequentially inoculation of Saccharomyces cerevisiae and Hanseniaspora uvarum strains isolated from honey by-products to improve and stabilize the quality of mead produced in Sicily

Mead is a beverage produced by alcoholic fermentation of honey-must. The starter yeasts that are commonly used for the alcoholic fermentation of honey-must are oenological Saccharomyces cerevisiae strains. The objective of the present work was, for the first time, to apply yeasts of honey by-products origin to evaluate the influences the taste-olfactory attributes of mead. For this purpose, three experimental productions were set up, which included: (i) single inoculation of S. cerevisiae; (ii) single inoculation of Hanseniaspora uvarum; (iii) sequential inoculation of H. uvarum/S. cerevisiae. Two control trials were performed, using a commercial strain of S. cerevisiae of oenological origin and a spontaneous fermentation. The results of the chemical parameters showed differences between the trials in terms of residual sugars, acetic acid, glycerol, ethanol and volatile organic compounds. Sensorial analysis also showed a high heterogeneity among trials. The attributes of sweetness, honey and floral were found in mead fermented with H. uvarum, whereas all meads obtained with S. cerevisiae were dry, balanced and without off-odors and off-flavours. The results obtained showed that the controlled application of conventional and non-conventional yeast strains isolated from honey by-products origin could be a promising approach to improve the quality of meads