Science of Wine: Julie Pepi

By OSC on April 27, 2016 in What's New

Wine Tasting Science with Julie Pepi

The eclectic Julie Pepi of Southern Wine & Spirits is the host of the sold out Wine Seminar for the 6th Annual Science of Wine on Saturday, April 30!

Pepi’s innate ability to create a humanistic environment in her seminars allow all wine lovers, from the novice to the expert, to comfortably pursue their knowledge of the grape.

Her seminar may have sold out but she wants everyone to learn some science behind winemaking and tasting so she stopped by to teach us some wine science 101.

1. What is the science at work behind wine-making?

Winemakers are artists and scientists. While science is at work throughout the entire viniifcation process, I find the science behind the fermentation segment of winemaking to be the most beguiling. Below is the best brief explanation I have found…

The fermentation process is often considered the magic of winemaking. It is a natural process and human intervention is only necessary to increase clarity and consistency. The key element in the fermentation process is yeast: a microscopic, single-celled fungus. When yeast comes into contact with the grape juice, a chemical reaction converts the sugar into alcohol and carbon dioxide:

C6H12O6=>2C2H5OH + 2CO2(1)

Wild yeast is generally present on the grapes, and this allows fermentation to occur naturally; wild yeast, however, is difficult to control and predict. For this reason, many winemakers sterilize the must first before adding their own strain of yeast that they are better able to control. Modern winemakers also add a small amount of sulfur to the must to kill off the wild yeast.

Fermentation involves many considerations. For example, temperature plays a very crucial role. If the temperature is too low, the yeast will not consume any sugar but will instead remain dormant in the wine. If the temperature is too high, then the yeast will ferment but simultaneously increase the production of unwanted enzymes and other micro-organisms, which can tarnish the flavor of the wine. The ideal temperature for fermentation is around 72 °F, although this can vary for different types of yeast.

There are two stages of fermentation: aerobic (with air) and anaerobic (without air). In the first stage, the mixture is open to the air as the name suggests. During this stage, the yeast rapidly reproduces, and this usually only takes around two to four days. During the second stage, the mixture is sealed off from the air and this is when the majority of the alcohol is produced. Under ideal conditions, the anaerobic fermentation should only take approximately three weeks, but in reality, it may take months.

Once the wine has reached its ideal sugar content (for most wines, this is when the sugar is completely gone, but for a sweeter wine there will still be some sugar left), fermentation of the must is stopped by killing or removing the yeast cells. This can be done either by chilling the must or by filtering out the yeast cells.


2. Why does geographic location influence the taste of the wine?

The complex influences that result in a wine’s unique traits are embodied in the concept of “terroir,” a term that attempts to capture all of the myriad environmental and cultural influences in growing grapes and making wine. Terroir is derived from the Latin “terre” or “territoire,” and its first modern definition appears as “a stretch of land limited by its agricultural capacity.” The best way to describe terroir is the geology, geography, soil and climate of a certain area. With any agricultural product, all the factors mentioned above will affect the way the product taste.

The optimal growing season is as follows- Grape vines need approximately 100-120 days of sunshine during the growing season and around 27 inches of rainfall throughout the year in order to produce grapes suitable for winemaking. In ideal circumstances, the vine will receive most of the rainfall during the winter and spring months: rain at harvesttime can create many hazards, such as fungal diseases and berry splitting.

The optimum weather during the growing season is a long, warm summer that allows the grapes the opportunity to ripen fully and to develop a balance between the levels of acids and sugars in the grapes. Hot and sunny climates have a frost-free growing season of 200 days or more. These climates allow grapes to ripen faster with higher sugar levels and lower acidity. Cooler climates have a frost-free growing season of around 150–160 days. Cooler seasons force the grapes to ripen earlier which produces a fresher and more acidic harvest. In general, the average yearly temperature for most crops should average around 60 degrees in order for the highest quality to be achieved in each grape.


3. Tell us about the science behind corks. What is some advice you have for saving your wine. Is there a difference between real and plastic corks?

Keep the open wine bottle out of light and stored under room temperature. In most cases a refrigerator goes a long way to keeping wine fresh longer; both red and white. When stored at colder temperatures the chemical processes slow down, including the process of oxidation that takes place when wine is exposed to oxygen. Wine stored by cork inside the fridge will stay relatively fresh for up to 3-5 days. Also store the wine upright to minimize surface area exposed to oxygen.

Here are some pros and cons of natural vs. synthetic vs. screw caps.

Natural Corks:

  • Traditionalists claim that “real” corks allow healthy gas exchange for flavorful wine.
  • Some claim that good sources of natural cork are dwindling.
  • Not all natural corks are alike, resulting in variable cork properties.
  • Higher chance of “corked” wines and trichloroanisole (TCA) taint.

Synthetic Corks:

  • Synthetics close 60% of the top 500 wines (sold by volume) in the US.
  • There is an untrue perception that synthetic corks let too much air into the wine bottle. They actually help regulate and manage oxygen.
  • Injection molded closures were so hard to take out of the bottle that most of those companies are out of business. Co-extruded synthetics can easily be extracted or reinserted into a
    wine bottle.

Screw Caps:

  • Less chance that wines will be “corked,” and probably fewer tainted wines.
  • Some say that air-tight screw caps are “suffocating” to wines.
  • Still considered by some to be the hallmark of a cheaper product.


4. What is the most unusual wine experience you’ve had in your career

It would definitely have to be doing a harvest in Germany wearing rocking climbing gear while scaling very steep vineyards. Unusual but incredibly awesome.

5. What is your advice for a novice wine drinker to best enjoy an event like Science of Wine?

This event comprises all of the most interesting aspects about the food and wine. My advice is to immerse yourself in everything offered to you and discover that wine is much more than fermented grape juice! Try everything that is being offered so you can learn about the many different wines we are offering from around the world and be sure to spit! Also, do a little research on food and wine pairings before you arrive so can take full advantage of all of the amazing culinary offerings! 

6. Your wine seminar is sold out but tell us about some of the other educational opportunities that will be at Science of Wine presented by Southern Wine & Spirits?

We SWS team will be on hand to discuss the wines we will be offering. The varietals, the regions, the different winemaking styles and also how to taste the wines. Learning how to taste wine really engages your ability to find different aromas and flavors. It’s going to be an incredibly informative, engaging evening filled with great wine, fantastic food and memorable experiences.

Meet Wine Seminar Presenter Julie Pepi

Julie Pepi (stage)Julie Pepi’s passion for wine began in 1991.  While pursuing a degree in interpersonal communication , she walked into what she thought would be a means to pay tuition and discovered a perfect mate for her first passion, which is working with people who truly love to experience life… The perfect match was, and still is wine. She has studied it’s history, romance, viniculture, viticulture, mystery and growth for over twenty years and continues to pursue and marvel at it’s evolution.

She is a second level sommelier with the prestigious Court of Master Sommeliers, Certified Wine Educator and Certified Sake Professional and is currently working towards Master Sommelier certification. Her career began doing harvests and working as an intern for wineries around the globe. She has furthered her experience by assisting or directing wine programs in highly profiled Inns and Restaurants-Vanguard establishments such as Glissandi in Lake Tahoe, The White Barn in Kennebunkport, Topper’s at the Wauwinet and the Straight Wharf on Nantucket, Chez Le Bear on Sanibel Island, Michaels On East in Sarasota and State Street Eating House in Sarasota.

Her innate ability to create a humanistic environment that allows all wine lovers, from the novice to the expert, to comfortably pursue their knowledge of the grape allows her to constantly achieve her professional goals while constantly enjoying her passion. Julie joined Southern Wine and Spirits in 2009 as a Sales Representative to further her knowledge of the business and is currently a the Fine Wine Director for North Florida.  She also hosts the popular Women and Wine Series in Sarasota, Bradenton, Longboat Key, Siesta Key and Venice and is also the educator for Sarasota Fine Wine’s immensely popular Wine Education Program.


Science of Wine at Orlando Science Center

April 30, 2016
7:00 – 10:00 p.m.

Members: $75
General: $95

Purchase Tickets

Sponsorships are available. Please contact Angela Mendolaro at 407.514.2019 or
Food partnerships available. Please contact Helen Tillem at 407.514.2290 or

Copyright 2018 | Orlando Science Center