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Facoltā di Scienze Agrarie e Alimentari Universitā degli Studi di Milano
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Code: G2511-
Teacher:  Ileana Vigentini
CFU subdivision: Lectures: 4,5
Practices in laboratory:  1,5
Basic aims:  Aim of the course is to give basic knowledge for understanding the identity, the physiological properties and role of microorganisms that play a role in wine chain. Object of study are yeasts and bacteria of main interest in the winemaking process, as well as the microorganisms that can modify the final product. Advancement of knowledge and applications to operate the control of safety and quality of wine and oenological products along the supply chain. Implementation of HACCP system in oenology. Risk assessment of the development of micro-organisms in wine production.
Acquired skills:  Tools to isolate, identify and to cultivate microorganisms of oenological interest to monitor microbiologically the winemaking process and to recognize and prevent wine spoilage. Knowledge of direct and indirect methods by using general and selective growth media to monitor the development of yeasts and bacteria. Evaluation of the role played by positive and negative microorganisms in the winemaking process. Management of the starter. Set-up of a hygiene system and quality assurance system into the cellar. Competence in the determination of microbiological safety and quality of wine and oenological products.
Course contents:  Ecophysiological characterization of wine yeasts and taxonomic arrangement with particular attention to Saccharomyces sensu stricto. Microbiological analysis in oenology and strain classification techniques through the use of cultural and molecular (PCR) methods. Factors affecting yeast growth during the different phases of winemaking. Yeast growth in controlled and spontaneous fermentations. Selection principles and techniques for the technological characterization of yeast and LAB strains. Management of the starter. Yeast autolysis . Killer yeasts. Lactic acid bacteria in wine and malolactic fermentation and its contribution to wine flavor. Selection and commercial cultivation of wine yeasts and malolactic bacteria. Genetic improvement of wine yeasts. Wine spoilage by yeasts, bacteria and molds. Effect of SO2 on wine microorganisms and strategies to minimize its use in winemaking. Management of the hygiene into the cellar. Implementation of a HACCP system in wine-making.
Program:  1. Taxonomy and ecology of the wine yeasts. Classification criteria. The different yeast species in musts and wines: yeasts in winery and fermentation. The Saccharomyces sensu stricto group. Morphological characteristics of wine yeasts. Methods of yeasts isolation, identification and characterization of microorganisms of oenological use. Identification systems based on the analysis of the phenotype and genotype. Using miniaturized systems for microbial identification based on analysis of the phenotype. Theory and applications of PCR. The genotyping techniques.
2. Primary metabolism and its regulation: Pasteur, Crabtree and Custer effects. Nitrogen, sulfur compounds and organic acids metabolism. Formation of sulfur compounds.
3. Growth kinetics of yeasts and factors affecting yeast growth during fermentation. Microbiological analysis at different stages of vinification. Microbiological control of must (determination of S. cerevisiae yeast contaminants, acetic acid bacteria and lactic acid bacteria by plate count technique). Control of the fermenting must (enumeration of S. cerevisiae with counting chamber, dying and microscopic observations, determination of Saccharomyces by membrane filter technique). Sparkling wines and Yeast autolysis. The yeast of maloalcholic fermentation.
4. Spontaneous and controlled fermentations. Yeast starter cultures and their usage. Yeats genome organization. The life style of Saccharomyces cerevisiae. Yeast genetics: heterotallic and homotallic yeast strain. The genetic interconversion phenomena. Genetic improvement of wine yeasts. Selection and management of the starter yeast selection for technological characteristics and quality traits. The selection by territories, the selection through genetic improvement. Isolation, control and maintenance of a pure cultures. Determination of the fermentation, assessing the flocculation character, H2S production, killer character. The types of commercial starters. The operation for starter management. The techniques of multiplication and maintenance (the laboratory phase, the phase of the cellar, the direct inoculation). Microbiological aspects of stuck fermentation.
5. Lactic acid bacteria (LAB) in musts and wines and their interaction with yeasts during alcoholic fermentation. Metabolism of sugars, organic acids and aminoacids. Effect of ethanol and temperature on the LAB growth. Spontaneous and controlled malolactic fermentation. Malolactic starter cultures. Isolation, control and maintenance of a pure culture of malolactic bacteria. Determination of malolactic bacteria with plate count technique.
Good Manufacturing Practices in cellar. The HACCP method and the application of the hygiene system. The manual of good practice for the wine industry. Sources of contamination in the cellar. Sanitation of equipment and facilities. Detergents and disinfectants. Water management process. Checking the personal hygiene and surfaces by the use of Petri-Contact and Swab Test. The bioluminescence technique. Microbial air monitoring. Microbiological control of drinking water. Compliance of bottle caps and corks. The bottling. Wine spoilage by LAB, acetic bacteria and yeasts. Sulphur dioxide and wine microorganisms. Control of stability of the bottled wine (membrane filtration and microscopic observation in epifluorescence).
Prerequisites:  Info not available
Preparatory instructions:  Info not available
Learning materials:  Educational material provided by the professor.
Other info:  Written test
Program of Info not available (pdf version)
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