Tilda Wilson / Sun Staff Designer

Scientists at Cornell AgriTech go through extensive processes to make apples fit for producing apple cider — a staple of Upstate New York.

October 25, 2021

Hot Cider Fall: The Science Behind Ithaca’s Favorite Drink

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Autumn has returned to Upstate New York, marked by students flocking to Indian Creek Farm to enjoy the peak season of apples and the sweet taste of fresh apple cider.   

Apple cider, a drink made from apple juice, and sometimes with an alcohol content up to 7 percent, has long been an Ithaca staple for local producers and autumn enthusiasts. 

Chris Gerling, a senior extension associate of Cornell AgriTech Food Science, who has extensive experience in teaching how to make apple cider and analyzing cider samples, explained the process of cider production. 

According to Gerling, cider makers must first pick, wash and rinse apples before grinding them up. Then, the apples are pressed to make sweet cider, and if the producer wishes to make hard cider, the cider is fermented to convert sugars into alcohol. 

Even before the apples are picked, specific types of apples must be carefully bred and grown to give the cider a complexity of flavor, Gerling said. 

For one, a variety of apples are specifically used in cidermaking, known as cider apples. Gerling explained that in contrast to culinary or dessert apples — the sweet variety people buy from supermarkets to eat and make up 95 percent of apples grown in the U.S. today — cider apples contain tannin. These chemical compounds can also be found in red wine, and are responsible for adding acidity and bitterness. 

Farmers from Cornell and other local areas breed many species of apples, like those pictured here The Apple Harvest Festival. (Hannah Rosenberg/Sun Photography Editor)

Because of this, cider apples, while not as delicious to eat, bring more depth to the taste of apple cider. 

Cortni Stahl, extension aid of the New York State Agricultural Experiment Station and a cider maker for 10 years, added that tannins further add complexity to cider by creating a drying sensation in the mouth. Gerling and Stahl both explained that the blend of apples, as well as the freshness, contribute to the cider’s flavor. 

According to Stahl, cider makers often use a blend of apples, rather than a single variety, to allow for the unique characteristics of each apple variety to shine in the cider. Gerling added that a blend creates a balance of flavor in sugars and acids. 

“As for freshness, identifying ripe apples can be done by using a starch test to check low amounts of starch, which in turn indicates high amounts of sugar in apples, or relying on the grower’s knowledge,” Stahl said. 

But according to Gerling and Stahl, the quality of apples is not the only key factor to a good apple cider — microorganisms that perform fermentation, such as yeast, also play a significant role. 

Stahl has researched the effect of using different yeast strains, including beer and wine yeasts, for fermentation on the aroma and taste of apple cider. Stahl explained that yeasts that perform fermentation that produce esters, compounds that influence sweet and fruity aroma and flavor, pair well with apple cider. 

Various yeast strains also contribute different amounts of compounds, Gerling said, and the temperature and nutrients provided to yeasts by cider makers also affect the taste of apple cider. A cool temperature of around 7 to 14 degrees Celsius and space for carbon dioxide to be released are also necessary for yeast to properly ferment, Stahl explained. 

Besides the yeast involved in fermentation, bacteria and other microbes are also involved by causing apple cider to spoil. Stahl said due to a pH from 3.3 to 3.7 and suitable sugar content, as well low alcohol content, apple cider allows for these microbes to easily thrive. Cider makers must maintain a sanitary, sterile environment, to avoid these microbes causing spoilage during cider production. 

This year has been challenging for apple cider production, both Gerling and Stahl said. 

According to Stahl, a late freeze resulted in apple blossoms dying and dropping. The warmer fall may also cause apples to fall from trees before they become ripe. As a result, the spring has brought a lower yield in apple orchards. 

Gerling also said an overall increase in rain throughout the year, compared to past years, has caused difficulty for the apple growing season, as the humidity and moisture fosters growing conditions for diseases, mold, mildew and fungus. Furthermore, climate change has made fermentation more difficult, as higher temperatures require a greater need for cider makers to regulate cooler temperatures and maintain the process. 

Stahl and Gerling have various ideas for projects on apple cider in the future. Gerling hopes to build partnerships with other New York cider organizations and continue researching yeast strains and tannin extraction from apples. Stahl aims to develop a machine trained to analyze cider samples based on pH, sugars and alcohol.

“In the future, we hope the machine will help us produce cider at more affordable prices,” Stahl said.