One Kreppel - Many Scents
a Carnival Pastry from Mainz
In Mainz, a Kreppel is much more than just a pastry – it belongs to the Fastnacht carnival season as naturally as the cathedral belongs to the market square. In February, when the streets fill with costumes and shouts of “Helau!” echo through the city, the air carries the scent of hot frying oil, yeasted dough and sweet jam.
Where does the Kreppel come from?
The Mainz Kreppel belongs to a large European family of jam-filled pastries made from yeast dough and fried in fat. Across different regions they go by different names. In Berlin and northern Germany, they are usually called Berliner or Pfannkuchen. In Bavaria and Austria, the same pastry is known as a Krapfen. In the Rhine–Main region, however, the name Kreppel is common.
The idea itself is surprisingly old. Already in medieval Europe, sweet balls of dough were fried in fat. Similar preparations go back even further to antiquity: in the Roman Empire, small pieces of dough were fried and sweetened with honey.
The close connection between these pastries and Carnival has historical roots. Before the start of the Christian fasting period of Lent, households had to use up rich ingredients that would not be eaten during the fast – especially sugar, butter or other fats, and eggs. These ingredients were turned into particularly indulgent sweets, enjoyed one last time before the fasting season began. Over time, this tradition developed into the carnival pastries that are still eaten during Fastnacht today.
In Mainz, the Kreppel has therefore become more than a pastry – it is a symbol of the carnival season. During Fastnacht, bakeries open early in the morning and the smell of freshly fried dough drifts through the streets. People bring boxes of Kreppel to the office, share them with colleagues, or place them on tables during meetings and preparations for carnival parades. Along the parade routes, they are just as much a part of the celebration.
Traditionally, Kreppel are filled with jam – most often strawberry or apricot – and generously dusted with powdered sugar.
What does a Kreppel smell like?
The aroma of a Kreppel is built from several layers: the scent of yeast dough, slightly oily notes from the frying fat, caramelised sugar from the baked dough, and the fruity sweetness of the jam filling.
The chemistry of this aroma begins already in the raw dough. As yeast causes the dough to rise, it breaks down amino acids and produces so-called fusel alcohols. In our measurements we find compounds such as 3-methyl-1-butanol (isoamyl alcohol), 2-methyl-1-propanol (isobutanol) and 2-methyl-1-butanol. These molecules originate from the amino acids leucine, valine and isoleucine and contribute slightly alcoholic, malty background notes typical of yeast fermentation.
When the dough enters the hot oil, the aroma changes dramatically. Heating triggers Maillard reactions, in which sugars and amino acids react to form a wide range of roasted flavour compounds. One example is 3-methylbutanal, a molecule also found in bread crust and roasted grains that contributes malty, bread-like notes.
At the same time, the hot oil produces its own characteristic aroma. As fatty acids oxidise, they form aldehydes such as hexanal, nonanal and 2,4-decadienal. These compounds are typical of heated vegetable oils and are responsible for the warm, slightly oily smell associated with freshly fried foods.
Within the dough itself, other substances appear as well, including lactic acid and 2-oxopropanoic acid (pyruvate). These compounds arise from microbial metabolism and sugar breakdown. They are usually less noticeable in smell but form part of the chemical environment in which the aroma develops.
The final aromatic layer comes from the filling. Strawberry jam contains various fruity esters, such as ethyl butanoate or isoamyl acetate, which contribute sweet, fruity notes. It also contains plant-derived terpenes like limonene, β-pinene and trans-β-ocimene, which add fresh and slightly floral nuances. Many of these molecules occur only in very small amounts, but they are highly odour-active, which means we can perceive them easily.
The scent of a Kreppel therefore emerges step by step: from fermentation in the yeast dough, from roasted aromas during frying, and from the fruity molecules of the jam filling. Together, they create the characteristic smell that many people in Mainz associate with childhood memories, carnival celebrations and the beginning of the festive Fastnacht season each year.
That aroma fits perfectly on our city scent map Mainz: a blend of bakery notes, sugar, fruit and lightly caramelised tones that instantly evokes memories of carnival mornings and local bakeries.
Text: Alexandra Gutmann