There’s nothing like celebrating the winter with a glass of warm, mulled wine—and understanding the science behind it

The Spanish have Sangría, the Germans have Glühwein, and it’s known by many other diverse names; in English, we call it mulled wine. Mulled wine is a spiced alcoholic beverage, usually made from red wine, aromatic spices and fruit, and served hot. In Europe, it is considered a traditional drink for the winter months, particularly around Christmas and the New Year's Eve festivities.

Evidence of the spiced mulled wine tradition can be traced as far back as the 2nd century BCE. It was introduced to central Europe by the Roman Legions and the merchants who accompanied them. Vineyards spread rapidly along the Rhine and Danube rivers, together with a plethora of recipes for mulled wines and various other beverages. Today, numerous recipes for spiced mulled wine exist, with most of them incorporating combinations of citrus fruits, strongly flavored spices and aromatic herbs.

Before we delve into the science behind the widespread  popularity of mulled wine, let’s have a go at preparing the drink. The following recipe is a product of repeated experiments to prepare mulled wine conducted in our home while hosting friends during the winter season. 


The ingredients: red wine, lemon, apples and various spices. A chef pours red wine into a pot | Rabusta,Shutterstock

Ingredients

 

  • 1 bottle of red wine

  • 1 ½ cups applesauce, or adjust to desired sweetness level

  • Juice from 3 oranges

  • Juice from 2-3 lemons

  • Water

  • 3 sour apples, diced

  • 3-4 cinnamon sticks

  • Additional spices to taste (ginger, cardamom, cloves, etc.)

  • 3 sprigs of rosemary

Instructions - 

  • In a medium-sized pot, combine the red wine, applesauce, orange juice, lemon juice and diced apples

  • Add water to achieve a total volume of about 2 liters

  • Heat the mixture until it is almost boiling, then remove it from the heat.

  • Add the cinnamon sticks, rosemary and other spices.

  • Serve hot and enjoy!


A cheery, piping hot drink for cold nights. A pot full of wine, fruit and spices | GoncharukMaks, Shutterstock

And Now For The Science

Wine is an acidic solution made from grapes. It consists mainly of water and alcohol (ethanol), along with small quantities of hundreds of compounds that impart flavor to the beverage. The compounds come from the grapes themselves, combined with yeast, bacteria, substances from the oak barrels in which the wine ages, and the effects of the weather and the soil on grape development. Each type of wine has a unique composition of substances—some are astringent and irritate the throat, others are colorful due to anthocyanins, or have a characteristic fruity aroma or taste.

Wine is the backbone of mulled wine beverages. It is accompanied by a long list of additives, such as fruit, spices and herbs, each ingredient contributing uniquely to the taste and smell of the mulled wine. The most common additives are orange, lemon, cinnamon, nutmeg, fennel or anise seeds, cloves, cardamom and ginger.

Each wine has its own distinctive composition. Grape treading in a mosaic from the 1st century CE in Madeira, Spain | Source: Sheila Terry, Science Photo Library

 

Citrus Fruit

Citrus fruit, particularly lemon and orange, are very popular for eating and drinking and also very common in recipes for mulled wine. It seems that historically, their  main appeal stemmed from their strong aroma, since the flavor of their wild fruit tended to be very sour or bitter. Over time, agricultural progress led to the development of citrus varieties ranging from mildly tart to sweet.

Citrus peels are used in various culinary applications. The outer layer of the peel, the epidermis, contains glands that produce aromatic oils, mainly limonene, which are responsible for the characteristic aromas of citrus fruits. The white, spongy pith is rich in pectin—a polysaccharide that is used, among other things, to thicken jams, and other compounds such as phenols, which have a typically strong aroma, and antioxidants, which are bitter, but water-soluble. Chefs recommend thoroughly washing the peel well in hot water to remove the bitter compounds before adding the peels to your cooking.

Fruit, including citrus fruit, are also rich in acids such as citric acid, ascorbic acid (Vitamin C) and malic acid—which is highly abundant in apples. They also contribute greatly to the flavor of the wine.

 

Herbs and Spices

Seasonings enrich the flavor of food in addition to camouflaging undesired flavors. Adequate seasoning can transform eating into a multi-sensory experience. When we eat, all of our senses are engaged, not only our sense of taste and smell - our eyes perceive, our ears hear, and our sense of touch discerns temperature and texture. Our senses are finely attuned and seasonings challenge and stimulate them.

Herbs and spices, derived from various parts of plants, are used in small amounts to infuse dishes with flavors and aromas. Herbs typically come from the green parts of the plant, usually the leaves, such as parsley and rosemary, while spices usually come from other parts, such as seeds (nigella, poppy seeds), bark (cinnamon), underground stems and roots (ginger), fruit (black pepper) and more.

Cinnamon (Cinnamomum zeylanicum) originates from the island of Sri Lanka, south of India; other species of Cinnamomum grow in China and tropical parts of Asia. The spice is the dried, inner bark of the tree, which is a distant relative of bay laurel. To produce cinnamon, young trees are coppiced so that they will produce several new trunks. The best ones are retained, growing into long, strong trunks. The outer bark, which has a very strong flavor, is used to produce ground cinnamon. The remainder of the trunk is cut, peeled and dried until the inner bark disconnects and becomes the familiar cinnamon sticks. The flavor and strong aroma of cinnamon come from multiple substances, mainly cinnamaldehyde—a component of the essential oil present in its bark.

Ginger is a species from the Zingiberaceae family, comprising five distinct genera. These are tropical plants with branched, and often thickened underground stems known as rhizomes. Many species in this family are ornamental plants and spices, with some carrying medicinal properties. The spice we know as ginger, from the species Zingiber officinale, has a slightly pungent taste, and is typically dried and ground into a powder. It is used to season baked goods, sauces, curries, sweets, pickled vegetables and beverages such as ginger ale.

The fresh rhizome is also used in cooking. In Japan and other places, slices of ginger are consumed between courses to clean the taste palette. Its spiciness comes from a family of compounds known as gingerols, which are related to capsaicin (the spicy element in chili peppers), and piperine (found in black pepper). Among these, the spiciness of the gingerols is the mildest, and it becomes even weaker during cooking.

Another spice is cardamom (Elettaria cardamomum), considered one of the most expensive spices in the world besides saffron and vanilla. The spice is the seed of a herbaceous plant from the Zingiberaceae family that originates in the mountains of south-western India. Cardamom seeds grow in bunches of small, fibrous boxes that ripen at different times, thus they are harvested by hand a short time before ripening. The flavorings and aromas are concentrated in the thin layer just beneath the seed coat.

Lastly, nutmeg and mace come from the same tree, Myristica fragrans, which is a tropical tree native to Asia. The part of the tree used for the spice is actually not a nut, but a seed, which grows inside plum-sized fruits. When ripe, the fruit splits open,  exposing a shiny, red seed coat that resembles a mesh, from which mace is produced. The seed itself (the “nut”) is ground to a powder or sold whole. The shiny color and abundance of sugars in the fruit attract many birds, who eat the fruit and carry the seeds with them. The flavorings are concentrated in the fatty tissue present in the starchy parts of the seed. The flavor and aroma of nutmeg and mace are similar, but those of mace are slightly more delicate.

 

 

And What About the Alcohol?

After mixing and heating up the components of mulled wine, we can ask how does the alcohol in the wine not evaporate completely during the heating? In fact, it’s impossible to remove all the alcohol from the wine, unless we cook the mixture until all the liquid evaporates. The proportion of alcohol remaining depends, of course, on the temperature and duration of the heating. Although alcohol boils at a lower temperature than water, only 78 degrees Celsius, strong electrostatic bonds form between the alcohol and water molecules. This attraction between the molecules is enough to ensure that sufficient alcohol will remain in the mixture even during boiling.

Physicist Richard Feynman was once quoted saying “If we look closely enough at a glass of wine, we’ll see the entire universe”. As we pour the mulled wine into a glass we can imagine hundreds of chemical compounds flowing with it—compounds that formed from minerals in the soil, water, air and light, turned into juicy grapes of varieties that have been improved over many years, and became wine with the help of bacteria and human intervention. These are joined by additional components that contribute a plethora of flavors, aromas, colors, and even atmosphere, that in cold Europe is associated with the early winter holidays. Here’s to a successful year!