1. Dictionaries say "apigenin," but research names another compound
The sharp scent you notice when cutting celery is often attributed to "apigenin" or "senkyunolide" in food explanations [4]. Yet, apigenin is described as a flavonoid glycoside (a molecule with sugar attached) and is known to be abundant in celery and parsley [5]. In 2023, a research group including Ritsumeikan University announced they had identified the gene for the enzyme that creates apigenin for the first time [5]. This confirms that apigenin is a well-studied component.
On the other hand, in studies that investigate scent components, the main contributors to celery's aroma are identified as a group of compounds called phthalides [1]. So, dictionaries list apigenin, while scent research lists phthalides.
2. Selecting the main scent players from 12 components
A Japanese research group (Kurobayashi et al., 2006) identified 12 components that contribute significantly to the aroma of both raw and boiled celery [1]. Among these, four were evaluated as contributing most to the overall celery scent: 3-n-butylphthalide, sedanenolide, trans-sedanolide, and cis-sedanolide [1]. The scent of this group is described using words like "celery," "herb," and "boiled celery" [2]. In terms of odor intensity (FD factor), phthalides were reported to have high values, reaching up to 3125 [2].
The same study showed that in raw celery, components with a grassy scent stand out, while different components become prominent when boiled [1]. However, the change in scent when boiled could not be explained by the amount of phthalides alone [1]. Phthalides contribute to the characteristic celery scent, but the difference between raw and boiled celery is not explained by quantity alone.
4. Overlapping components with other Apiaceae plants
Phthalides are not unique to celery. They are a group of compounds common in plants of the Apiaceae family (to which celery belongs), such as those in the Angelica and Ligusticum genera, and are said to be responsible for celery's characteristic scent [6]. The essential oil of lovage, an Apiaceae herb, also contains 3-butylphthalide and ligustilide, sharing components with celery [6]. However, just because components overlap does not mean the scent is the same. Only some components are shared, and the proportions and overall scent profile differ from plant to plant.
Celery seeds contain about 3% essential oil and have a strong celery scent [4]. Celery's scent is found not only in leaves and stalks but also in seeds.
5. Odorless scents that enhance the umami of soup
Some phthalides have been reported to change how taste is perceived, even though they have no taste themselves. The phthalides in celery's scent (3-n-butylphthalide, sedanenolide, sedanolide) have no flavor on their own. However, when added in very small amounts to chicken broth, umami and sweetness were felt more strongly, according to reports [3]. Sedanenolide had the greatest effect, and volatile components had a larger effect than less volatile ones [3].
The amount added was very small, about 0.2 to 0.7 ppm [3]. The test participants were 6 to 10 adult women, and the mechanism for why the taste felt stronger is not understood [3]. Therefore, we cannot say "adding celery makes everything delicious." However, it serves as an example of how scent affects the perception of food taste.
6. Check the scent with your own nose and read the original sources
If you have celery at home, tear off one leaf and smell it. Then, rub it in your hand and smell it again. Is the scent when cut the same as when just torn? If you have other Apiaceae herbs like parsley, you can compare the scents. Even if some components overlap, your nose might reveal that the overall scent is not the same.
When using a knife, do this with an adult. After smelling, think about which you think is closer to the scent: the dictionary's apigenin or the research's phthalides. If you want to read a source close to the original, the paper by Kurobayashi et al. [1] is available on J-STAGE.