CHAPTER 1 INTRODUCTION TO WINE

INTRODUCTION TO WINE

History of wine

The exact origins of wine remain uncertain, but it is believed to be over 20 million years old, evolving alongside fermenting yeasts and fruit-bearing plants In ancient cultures, wine was viewed as a magical gift from nature Archaeological findings indicate that grape wine production began as early as 6000 BC in regions such as Georgia and Iran.

Winemaking originated in ancient civilizations such as Egypt, Phoenicia, and Greece between 5000 BC and 4500 BC, later spreading to Europe and northern Africa around 1500 BC By 1000 years later, wine production had also begun in India and China.

Advancements in production methods, including vine cultivation, pottery production, and winemaking practices, reached their peak between 200 and 400 AD, followed by a stagnation period lasting 1200 to 1400 years, primarily confined to monastic religious orders in Western Europe The Romans introduced barrel usage in the 3rd century AD, enhancing wine storage From the 1600s, cork became the standard stopper for wine, coinciding with the increased use of glass bottles, which significantly improved the transportation and storage of wine as glass production advanced.

The 18th century marked a significant acceleration in wine production methods, influenced by evolving trade relations in Europe, which led to the emergence of vintage, age-worthy wines The 19th and 20th centuries were transformative for the wine industry, characterized by groundbreaking discoveries and innovations Key milestones included Louis Pasteur's 1858 identification of bacteria in wine, Berthelot and De Fleurieu's 1864 observation of reduced wine acidity, and Pasteur's subsequent proof in 1864 that fermentation is driven by living yeast cells.

‘fermentation enzyme’ (Büchner, 1897) Also, in 1864, there was the first sighting of Phylloxera in France which destroyed much of the world's vineyards, outside of America’s for nearly 20 years

By the early 20th century, the devastation of the World Wars transformed vineyards into battlegrounds, yet scientists continued to make significant advancements in wine production The introduction of flor yeast in the 1910s and the initiation of vine improvement programs in the 1920s marked important milestones The 1930s saw further innovations, including the use of Bentonite for wine clarification and the elucidation of the life cycle of Saccharomyces cerevisiae yeast With the advent of refrigeration, wineries gained the ability to control fermentation temperatures, enabling the production of high-quality wines even in hot climates Additionally, the innovative bag-in-a-box concept emerged in 1964, revolutionizing wine packaging.

Introduction to Wine**: Wine is a complex and diverse beverage that has been enjoyed for centuries, offering a rich tapestry of flavors, aromas, and cultural significance This chapter serves as an essential guide for beginners, exploring the various types of wine, the winemaking process, and the key factors that influence taste and quality Understanding wine can enhance your appreciation and enjoyment, whether you are selecting a bottle for a special occasion or simply exploring new varieties Join us as we delve into the fascinating world of wine, uncovering its history, regions, and the art of tasting.

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Wine has rapidly gained popularity, contributing to a global industry valued in the billions of dollars In the 21st century, Italy, France, Spain, the United States, and China stand out as the leading wine producers.

Classification of wine

There are many ways to classify wine Table 1 below briefly illustrates how wines are classified based on five different standards

Table 1 Wine classification based on five different standards

Red wine fermented from grapes with skin

White wine removed skins and seeds of grapes before fermentation

Rosé wine made of red grape varieties after short-term impregnation and fermentation

Still wine with a carbon dioxide pressure of less than 0.05 MPa at 20℃

Sparkling wine with a carbon dioxide pressure greater than or equal to 0.05

According to the sugar content

Residual sugar in wine refers to the sugar that remains after fermentation if it has not been fully converted into alcohol Wines can be categorized into different levels based on their residual sugar content, distinguishing between still and sparkling varieties.

According to the wine body

Light-bodied wine lighter in color and have fewer tannins

Medium-bodied Wine darker and have more texture on the tongue.

Full-bodied Wine deepest color and abundant tannins

According to the grape harvest time

Ordinary Wine Material: grape is picked after natural maturity come down

Material: grapes are naturally ripe and wait a few days (weather permitting), and when picked, the resulting wine tends to be sweeter and more flavorful

Material: the harvest time of grapes is delayed first, when the weather permits, the grapes are often infected with certain noble rot bacteria

Ice Wine Material: Waiting until the temperature drops to -7℃ to -8℃, grapefruit is frozen and then harvested

Wine has a rich history and cultural significance that spans thousands of years Understanding the basics of wine, including its production, varieties, and tasting techniques, is essential for both enthusiasts and casual drinkers This introduction serves as a gateway to exploring the diverse world of wine, from the vineyards to the glass By delving into the fundamentals of wine, readers can enhance their appreciation and enjoyment of this timeless beverage Whether you're a novice or a connoisseur, this guide will provide valuable insights into the art of wine.

Wine making process

There are five basic stages to making wine: harvesting, crushing and pressing, fermentation, clarification, aging and bottling

Winemakers usually harvest grapes from a vineyard in late summer or early autumn when grapes are riped enough After harvested, grapes are classified to cull rotten and under-ripe grapes

Crushing the entire grape cluster is a crucial step in winemaking, which can be performed using industrial crushers or manually by individuals This process yields free-run juice and a mass of crushed grapes known as must The pressing technique employed varies based on the type of wine being produced.

To produce white wine, winemakers promptly press the must to extract the juice, ensuring that unwanted color and tannins from the grape skins do not contaminate the final product In contrast, red wine production involves leaving the must in contact with the skins, allowing for the infusion of color, flavor, and additional tannins during fermentation.

The conversion of grape juice into wine is a microbial process that typically lasts from ten days to over a month This process, known as alcoholic fermentation, transforms the main grape sugars, glucose and fructose, into ethanol and carbon dioxide In winemaking, this fermentation occurs in two key stages: natural fermentation followed by later fermentation.

Natural fermentation, occurring within the first 6 to 12 hours, is driven by wild yeasts present on grapes, influencing the wine's sensory characteristics such as flavors, aromas, and texture However, this process can also result in undesirable colors and off-flavors The unpredictable nature of wild yeast can disrupt the fermentation by overpowering the desired Saccharomyces yeast To mitigate these risks, winemakers often inoculate the must with a commercial yeast starter culture, ensuring a controlled fermentation process.

Commercial yeast strains experience a lag period during which they adapt to low substrate and high oxygen conditions This adaptation is crucial for promoting cell growth and fermentation, as it allows the yeast to acquire the sterols and unsaturated fatty acids essential for enhancing ethanol tolerance.

Saccharomyces metabolize glucose and fructose to pyruvate via the glycolytic pathway Primarily to recycle cofactors, pyruvate is decarboxylated to acetaldehyde, which is then reduced to ethanol One molecule

Wine is a complex and fascinating beverage that has been enjoyed for centuries Its rich history is intertwined with various cultures and traditions, making it a significant part of social gatherings and celebrations Understanding the basics of wine, including its production process, types, and tasting techniques, can enhance your appreciation and enjoyment This introduction serves as a gateway to the world of wine, inviting enthusiasts and novices alike to explore its diverse flavors and aromas Whether you’re looking to deepen your knowledge or simply enjoy a glass with friends, the journey into wine is both rewarding and enjoyable.

Page | 4 of glucose (or fructose) yields two molecules of ethanol as well as carbon dioxide The net equation for this reaction is:

Hexose + 2 ADP → 2 Ethanol + 2 CO2 + 2 ATP

Fermentation generates significantly less ATP than respiration, and most eukaryotes typically rely on it only in anaerobic conditions However, Saccharomyces can initiate fermentation even in the presence of oxygen if ample glucose is available The primary result of glycolysis is the conversion of hexose sugars into ethanol, while some glycolytic products are redirected to produce biomass, including glycerol and acetic acid This process is regulated by two key mechanisms: glucose repression, which inhibits the transcription of growth and metabolic genes in high glucose environments, and glucose inactivation, leading to the degradation of proteins affected by glucose levels Additionally, minor metabolites important for flavor are produced, influenced by the reducing environment and the release of volatiles in CO2 gas In a typical fermentation with 22-24% sugar, approximately 95% is transformed into ethanol and carbon dioxide, while 1% is used for cellular materials and 4% is converted into other byproducts.

Winemakers often allow oxygen to enter the must to boost yeast biomass prior to fermentation Subsequently, they create anaerobic and low-temperature conditions to optimize fermentation yield.

Some wine deposits their suspended material (yeast cells, particles of skin, etc.) very quickly Removal of this suspended material is called clarification The major procedures involved are:

• Fining: Proteins and yeast cells are adsorbed on fining agents such as bentonite, gelatin, silica, phytate, etc

• Filtration: Removal of yeast cells and most bacterial cells by sufficiently small pore size of filters

• Centrifugation: High-speed spinning used to clarify the must

• Refrigeration: Temperature reduction prevents both yeast growth and the evolution of carbon dioxide, which tends to keep the yeast cells suspended

• Ion exchange: If ion exchanger is charged with sodium, it will replace the potassium in potassium acid tartate with sodium, making a more soluble tartate

• Heating: Pasteurization at 70 to 82 o C can be used to preciptate proteins that cause clouding by reacting with copper or other metals

Wine is a fascinating beverage with a rich history and diverse varieties Understanding the basics of wine, including its production process, types, and tasting techniques, is essential for enthusiasts and casual drinkers alike This introduction to wine explores the fundamental aspects of viticulture, from grape cultivation to fermentation, and highlights the significance of terroir in shaping wine’s unique characteristics Additionally, it offers insights into the various wine styles, regions, and food pairings, making it a valuable resource for anyone looking to deepen their appreciation of this timeless drink.

Many wines enhance in quality through barrel and bottle aging, ultimately reaching a peak before declining with further maturation During this aging process, acidity diminishes, clarification and stabilization occur as unwanted substances settle, and the wine's components create complex compounds that influence flavors and aromas Typically, wines are aged in oak barrels, which facilitate oxygen entry and allow the evaporation of water and alcohol, thus reducing volume for the addition of more wine.

Before bottling, wine often undergoes blending, filtration, and the application of antiseptics to prevent microbial growth The shape and color of the bottle are influenced by tradition and cost considerations To protect certain white wines from light exposure, they are typically bottled in brown, brownish-green, or greenish-blue bottles Once bottled, red wines intended for long-term aging are sealed with corks measuring 5 centimeters in length.

Appropriate storage conditions include an absence of light and a low temperature at about 12 to 16 o C to prevent rapid aging and deterioration by microbial factors

Wine is a complex and fascinating beverage that has been enjoyed for centuries It is made through the fermentation of grapes, which can vary widely in flavor, aroma, and color depending on the grape variety and production methods Understanding the basics of wine, including its history, types, and tasting techniques, is essential for any wine enthusiast From the vineyards to the bottle, each step in the winemaking process contributes to the final product, making wine appreciation a rich and rewarding experience Whether you are a novice or a connoisseur, exploring the world of wine opens up a journey of sensory discovery and cultural significance.

YEASTS IN WINEMAKING

Sacchromyces cerevisiae

2.1.1 Taxonom: Morphology and special characteristics

Saccharomyces cerevisiae (S cerevisiae) is a unicellular eukaryotic microorganism classified within the fungus kingdom This dimorphic yeast exhibits two growth forms: unicellular and filamentous Additionally, some strains can display multicellular traits by producing pseudohyphae, also known as false hyphae.

Saccharomyces cerevisiae belongs to the kingdom of fungi (Mycophyta), class Ascomycetes, order

Endomycetes, specifically the family Saccharomycetaceae and the genera Saccharomyces and Cerevisiae, exhibit significant size variations throughout their developmental stages Generally, yeast cells are larger than bacterial cells, measuring approximately 7 µm in diameter and 8-12 µm in length Temperature influences their size; for instance, at growth temperatures above 18.5°C, the critical diameter of a single cell is 7.94 µm, while at lower temperatures, it can increase exponentially to 10.2 µm The vegetative cells of Saccharomyces cerevisiae, the most common and widely utilized domesticated yeast, typically appear egg-shaped, elliptical, or occasionally spherical However, their shape is not fixed and can vary based on factors such as age, variety, and environmental conditions In nutrient-rich media, cells tend to be oval, while they adopt a round shape in anaerobic conditions and become elongated in aerobic environments The characteristic color of these yeast cells is yellowish-green.

Figure 1 Some images of yeast: S cerevisiae TBS (a&b) and S cerevisiae TNS (c&d)

Introduction to Wine**: Wine is a beloved beverage with a rich history and diverse varieties Understanding the basics of wine, including its production process, types, and tasting notes, is essential for both enthusiasts and casual drinkers This chapter serves as an introduction to the fascinating world of wine, exploring its cultural significance, the art of winemaking, and tips for selecting the perfect bottle Whether you're a novice or a seasoned connoisseur, this guide will enhance your appreciation of wine and its complexities.

2.1.1.2 Typical characteristics of cell structures

Figure 2 Structure of S cerevisiae cell

As a eukaryote, S cerevisiae features membrane-bound organelles, distinguishing it from prokaryotic bacteria The evolution of the nucleus and nuclear division mechanisms, including membranous nuclei and chromosomes, has led to the development of various cellular structures unique to eukaryotes Yeast cells exhibit a complex architecture and diverse cellular components, which can be categorized into intracellular organelles and inclusions.

A typical S cerevisiae cell would be composed of: a cell wall; plasma membrane; cytosol; nucleus; endoplasmic reticulum; vacuole; Golgi apparatus; mitochondrion; and peroxisome

The cell envelope of yeast consists of protein-polysaccharide complexes, phosphate groups, and lipids, measuring approximately 25 nm in thickness and accounting for 25% of the cell's mass It primarily contains glucan and mannan in its polysaccharide component This dense, soft, and elastic membrane surrounds the yeast cell, providing shape and protection against external influences and toxins Additionally, the yeast cell envelope is electrically charged and plays a crucial role in maintaining intracellular osmotic pressure while regulating the intake of low-molecular-weight nutrients and mineral salts through small pores.

Between the cell wall and the cytoplasmic membrane, a variety of hydrolytic enzymes, including B-fructofuranozidase (invertase) and acid phosphatase, are present Some of these enzymes are attached to the cell wall, with invertase being a mannoprotein that contains up to 50% mannan, which is crucial for stabilizing the enzyme's molecular structure.

Wine is a fascinating beverage that has captivated cultures throughout history This chapter explores the origins of wine, its various types, and the processes involved in its production Understanding the basics of wine can enhance appreciation and enjoyment, whether for casual drinkers or connoisseurs Key components such as grape varieties, fermentation methods, and aging techniques are discussed to provide a comprehensive overview By delving into the world of wine, readers can develop a deeper connection to this timeless drink, making informed choices and discovering new favorites along the way.

The cytoplasmic membrane, a delicate structure measuring just 0.1 nm in thickness, serves as a luminous boundary around the cytoplasm It performs four essential functions: acting as an osmotic barrier, regulating the influx of nutrients and the efflux of metabolic products, and facilitating biosynthesis Additionally, it synthesizes key cell components, housing specific enzymes and organelles like ribosomes.

For small granules or rods, filaments, shape changes during culture, rod, single strand, or chained The

S cerevisiae cells maintained at various glucose concentrations have distinct mitochondrial morphologies

Mitochondria in cells cultivated on 0.5 percent glucose exhibit a structure similar to those in respiring cells, while higher glucose concentrations (2 and 4%) lead to mitochondrial fragmentation due to acetic acid formation In contrast, yeast cells in low glucose environments can possess 100-200 mitochondria The transition from aerobic to anaerobic conditions results in simplified mitochondrial structures, consisting of two membranes without folds in the absence of lipids; however, the introduction of lipids induces the development of folds.

Eukaryotic cells, including yeast strains, feature immutable components such as DNA and RNA, with varying nuclei sizes observed both among different strains and within the same strain Additionally, these cells contain organelles like vacuoles, ribosomes, and the Golgi apparatus, which share structural similarities with plant cells.

Saccharomyces cerevisiae, a diverse fungal species, consists of various strains and is classified as a heterotroph, meaning it derives its nutrients from other organisms Its yeast cells are primarily composed of water, organic compounds, and ash, which enable them to oxidize sugars, fats, and proteins for energy S cerevisiae can ferment several sugars, including glucose, galactose, maltose, sucrose, raffinose, and simple dextrin, but it does not ferment lactose, mannitol, nitrate, or starch Optimal growth occurs at temperatures between 33-35°C in environments with 10%-30% glucose, with a minimum growth temperature of 4°C in 10% glucose and 13°C in 50% glucose, while the maximum is around 38-39°C This yeast can utilize various amino acids, small peptides, and nitrogen bases as nitrogen sources, with galactose and fructose being the most effective sugars for fermentation S cerevisiae exhibits both aerobic and anaerobic respiration, although some strains cannot grow anaerobically on sucrose and trehalose, effectively converting sugars through these respiration processes.

Chapter 1: Introduction to Wine explores the rich history and cultural significance of wine It delves into the various types of wine, including red, white, and sparkling, and discusses the winemaking process from grape selection to fermentation This chapter also highlights the importance of terroir, which influences the flavor profiles of wines Understanding wine tasting techniques and food pairings is essential for enhancing the wine experience Overall, this introduction serves as a foundational guide for both novice and seasoned wine enthusiasts, providing insights into the art and enjoyment of wine.

Yeast cells are essential for life as they contain vital substances like proteins, carbohydrates, lipids, enzymes, vitamins, amino acids, and minerals Sulfur plays a crucial role in protein structure and coenzyme A; its deficiency can impair metabolism and enzyme synthesis Under anaerobic conditions, sulfur is converted into hydrogen sulfide (H2S).

Aerobic Respiration: C6H12O6 (sugar) + 6 O2 → 6 CO2 + 6 H2O + energy

Anaerobic Respiration: C6H12O6 (sugar) → 2 C2H5OH (alcohol) + 2 CO2 + energy

Yeast cells exist in two forms during their life cycle: haploid and diploid Under optimal conditions, haploid cells replicate through budding When haploid mating types encounter each other, they form gametophytes, initiating sexual reproduction The resulting zygote undergoes budding to produce multiple larger diploid cells These diploid cells, like their haploid counterparts, replicate through budding In adverse conditions, the diploid cells become spherical and function as parent cells Meiosis then divides the parent cell's nucleus into four haploid nuclei, which gather cytoplasm to form spores Each ascospore is a thick-walled, spherical structure with ascospore septa compartments, and upon germination, ascospores produce haploid dwarf cells.

Figure 3 Reproductive cycle Saccharomyces cerevisiae

(1): Asexual reproduction (budding) (2): Sexual reproduction

(3): The process of cyst formation containing 4 spores

Under severe conditions, diploid cells undergo meiosis to produce four haploid spores, comprising two (a) spores and two (α) spores These haploid cells can fuse with other haploid cells of the opposite mating type to form a diploid zygote The cytoplasm of the haploid cells merges, leading to fertilization Subsequently, the zygote undergoes meiosis, resulting in an ascus that divides into four ascospores Ultimately, these haploid spores can germinate and revert to haploid cells.

Spoilage yeast strains

This yeast, often present in wineries and oak barrels, can act as a contaminant in wine production Its growth may produce volatile phenol compounds, resulting in undesirable odors reminiscent of "barnyard," "horse sweat," or "band-aid." A key chemical associated with this yeast is 4-ethyl phenol.

Kloeckera apiculata is a yeast that plays a crucial role in the initial phases of natural fermentation It has the ability to generate significant amounts of esters, particularly ethyl acetate and methyl butyl acetate, which can lead to an undesirable vinegar-like aroma known as ester taint.

Table 2 shows some of the most common yeasts often found in grape, musts and wines that can be considered spoilage yeast species in a wide range of food products

Table 2 Some common yeasts in grape, musts and wines that can be considered spoilage yeast species in a wide range of food products

Yeast species Food product Spoilage compounds Effect observed

Product with 50% sugar Alcohol, esters Gas production: bubbling and package expansion

Sweet wines Refermentation and CO2 production Mould-ripened soft cheeses

Fruit juices, sauces, carbonated soft drinks, salad dressings, ketchup

Alcohol, esters Gas production: bubbling and package expansion

Bulk, barrel matured and bottled wines

4-ethylphenol, 4-ethylguaiacol, Acetic acid, Tetrahydropyrindines

Off aromas, cloudiness formation in sparkling wine, mousy aroma Unpleasant mousy and medicinal taints

Food products with SO2 as antiseptic

Bottle wines Spoilage by sediment or cloudiness formation

Wine High acetoin level Flocculent sediment

Wine is a fascinating beverage with a rich history and cultural significance It is produced through the fermentation of grapes, resulting in a diverse range of flavors and styles Understanding the basics of wine, including its types, production methods, and tasting techniques, is essential for both enthusiasts and casual drinkers This chapter serves as a comprehensive introduction to the world of wine, exploring its origins, varieties, and the art of appreciation By delving into the nuances of wine, readers can enhance their tasting experiences and deepen their knowledge of this timeless drink.

FACTORS THAT AFFECT THE WINE FERMENTATION

Temperature

Depending on the floating or sinking yeast, adjust the ambient temperature accordingly For floating yeast, the suitable temperature is from 20-28 o C; for submerged yeast, the suitable temperature is from 5-10 o C

In addition, at a temperature of 28-30 o C, the alcohol evaporates, making the fermentation process happen faster, and at a temperature of 50 o C onwards and below 0 o C, the yeast is inactive

Temperature plays a crucial role in yeast activity; cold conditions can render them dormant, while excessive heat can lead to uncontrolled fermentation, resulting in undesirable flavors Elevated temperatures also promote the formation of fusel alcohols, which are heavier and can impart harsh, solvent-like tastes to the final product.

Sugar concentration

Yeasts primarily ferment simple sugars, including monosaccharides like glucose and fructose, as well as disaccharides such as maltose and sucrose Notably, lactose can only be fermented by the Saccharomyces lactic acid yeast Additionally, yeasts are unable to hydrolyze polysaccharides, limiting their fermentation capabilities to simpler sugar forms.

Alcohol fermentation is inhibited when sugar concentration exceeds 30% For optimal fermentation, specific sugar concentrations are utilized based on the desired product In alcohol production, a sugar concentration of 14-20% is ideal, allowing for a robust fermentation process that depletes the sugar before distillation Wine, on the other hand, typically requires a sugar concentration of 16-25% and employs submerged yeast, resulting in a slower fermentation that retains some residual sugar, giving wine its characteristic sweetness In beer production, the sugar concentration is generally maintained between 9-12%.

pH

pH is crucial in the fermentation process, with yeast thriving best at a pH range of 4 to 4.5 While yeast can grow at a pH of 2 to 8, bacteria start to proliferate at pH levels of 4.2 and above; below this threshold, only yeast can survive To optimize fermentation, it's essential to maintain the pH below 4, as yeast growth declines significantly at pH 8, where bacteria flourish Conversely, at a pH of 3.8, yeast experiences robust growth while bacterial development is minimal.

To achieve the optimal pH level in yeast culture medium, it is essential to incorporate an acid that preserves yeast activity Citric acid is frequently utilized for pH adjustment in fermentation processes.

Wine has a rich history that dates back thousands of years, making it a significant aspect of various cultures Understanding wine involves exploring its origins, production processes, and the diverse varieties available today This introduction to wine highlights its importance in culinary traditions and social gatherings, emphasizing the art of wine tasting and appreciation As we delve deeper, we will uncover the intricate relationship between wine and food, along with tips for selecting the perfect bottle for any occasion.

The pH level of the environment is crucial in determining the type of product produced during fermentation When the medium is acidic, the primary product is ethyl alcohol In a weakly acidic environment, both ethyl alcohol and glycerin are generated Conversely, if the medium remains weakly acidic, the resulting products include ethyl alcohol, acetic acid, and glycerol.

Oxygen

Oxygen plays a crucial role in the growth of yeast cell biomass, but it can lead to product damage in later stages of fermentation Initially, a limited amount of oxygen is required to promote yeast cell proliferation Once the fermentation broth has sufficient yeast cells, it is essential to minimize oxygen exposure, allowing the yeast to effectively ferment sugar into alcohol and carbon dioxide.

Oxygen is essential for the synthesis of biological components such as sterols and unsaturated fatty acids in various organic molecules While yeast can produce energy without oxygen during winemaking, it needs ample free oxygen for optimal growth A reduction in oxygen availability inhibits fatty acid and sterol biosynthesis in yeast, leading to decreased biomass production and glycolysis rates.

Yeast accelerates its growth by utilizing available oxygen in the wort, which enhances its efficiency Although yeast can adapt and thrive without oxygen through alternative mechanisms, the presence of oxygen significantly boosts their growth rate Under normal conditions, yeast typically completes the adaptation phase and initiates primary fermentation within 12 hours.

Yeast is a facultative respirator Under aerobic conditions in the presence of oxygen, the following reaction will occur:

C6H12O6 +6O2 → 6H2O + 6CO2 +Q1 ➔ increase biomass Only under anaerobic conditions does it proceed to alcoholic fermentation according to the equation:

Therefore, in the presence of oxygen, alcohol fermentation will be inhibited

The Pasteur effect refers to the suppression of alcohol fermentation when oxygen is present, leading to a shift from fermentation to respiration This transition not only decreases the production efficiency of alcohol and carbon dioxide but also diminishes the effectiveness of sugar utilization.

The initial phase of fermentation necessitates the presence of air to promote yeast growth, while subsequent stages thrive in anaerobic conditions, where oxygen is no longer required, optimizing the process for efficient alcoholic fermentation.

Chapter 1: Introduction to Wine explores the rich history and cultural significance of wine It delves into the various types of wine, their production processes, and the regions renowned for their vineyards Understanding wine involves appreciating its diverse flavors, aromas, and the art of tasting This chapter serves as a foundational guide for both novices and enthusiasts, emphasizing the importance of wine in social and culinary contexts By the end, readers will gain a deeper appreciation for wine and its role in different cultures around the world.

Wine concentration and carbon dioxide (CO 2 )

Alcohol accumulation in the fermenter, along with CO2 production, negatively impacts yeast growth and fermentability Yeast growth begins to slow at an alcohol concentration of 1%, and concentrations between 4% and 6% further hinder fermentation Most yeast strains effectively ferment alcohol concentrations of 12-14%, while only a select few can tolerate levels of 17-20% Excessive alcohol concentrations ultimately inhibit all yeast activity.

Yeast alcohol tolerance refers to the maximum alcohol concentration that can be sustained without hindering yeast growth and activity after 72 hours of cultivation at 30°C While carbon dioxide (CO2) production can inhibit fermentation, its release ultimately supports the fermentation process.

Starter culture

The quantity of yeast cells introduced to the yeast juice significantly influences the fermentation process An optimal number of yeast cells ensures efficient fermentation, leading to higher recovery rates and improved product quality Conversely, insufficient yeast cells result in a sluggish fermentation rate, while excessive yeast biomass can deplete the fermentation medium, causing yeast cell death, off-flavors in the product, and considerable waste of yeast.

This chapter provides a comprehensive overview of wine, exploring its history, production processes, and cultural significance Wine has been an integral part of human civilization, celebrated for its diverse flavors and varieties Understanding the basics of wine, including types, tasting techniques, and food pairings, enhances the appreciation of this ancient beverage Whether you're a novice or a connoisseur, this introduction aims to deepen your knowledge and enjoyment of wine.

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[5] Wine History (2021) Retrieved 29 November 2021, from http://winehistory.com.au/wiki/Wine_History

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[8] Karki, G (2018, December 18) Yeast: Morphology and life cycle Online Biology Notes Retrieved November 22, 2021, from https://www.onlinebiologynotes.com/yeast-morphology-life-cycle

[9] Lương Đức Phẩm (chủ biên), Nấm Men Công Nghiệp, NXB Khoa Học và Kỹ Thuật, 2009

[10] Parapouli, M., Vasileiadis, A., Afendra, A.-S., & Hatziloukas, E (2020, February 11) saccharomyces cerevisiae and its industrial applications AIMS microbiology Retrieved November 22, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7099199/

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[12] Seo, D (n.d.) The saccharomyces cerevisiae world - Daniel Seo The Saccharomyces cerevisiae World - Daniel Seo Retrieved November 22, 2021, from http://danielseobiodiversity.blogspot.com/

Chapter 1: Introduction to Wine explores the rich history, diverse varieties, and cultural significance of wine This chapter provides a foundational understanding of wine production, including the fermentation process and the importance of terroir It also delves into the different types of wines, such as red, white, and sparkling, highlighting their unique characteristics and flavor profiles Additionally, the chapter emphasizes wine's role in social gatherings and culinary pairings, making it an essential element of many cultures around the world Understanding these fundamentals sets the stage for a deeper appreciation of wine and its complexities.

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