The aromas of sake are composed of many different substances, and many people in particular enjoy the fruity, floral aromas called ginjo-ka. Literally meaning “ginjo aroma,” as the name suggests, ginjo-ka is mainly a characteristic of ginjo type sakes (including junmai ginjo, daiginjo, and junmai daiginjo), and refer to the fruity aromas of the sake. Laboratory experiments and research performed by the Gekkeikan General Research Institute under the direction of Professor Yukihiro Yada of the University of Tsukuba suggest that these aroma components can also help relax a person’s mind and body. These findings are the world’s first results.
The findings of this research prove that the aroma components that make up the ginjo-ka aroma of sake are not merely highly regarded from a preference and taste perspective, but that they also have a strong calming and relaxing effect on the human mind and body. We hope that these findings lead people — not just in Japan but around the world as well — to relax with and appreciate the rich fragrance of sake, in particular sake which strongly express ginjo-ka aromas. We also hope that the results of this research will open up new avenues for developing sake with strong ginjo-ka aromas, and we are considering further research into whether and how the aromas of sake have an effect of alleviating stress in our everyday lives.
In recent years, there has been growing interest in how odors can affect psychology and physiology of human beings, and there have been reports about not just scented and fragranced products, but also food and beverage products and the sedative or stimulant effects they can have. Two of the main substances that are found in sake are ethyl caproate, which produces floral, aromatic apple fragrances, and isoamyl acetate, which produces rich banana-like aromas. These are both esters produced from rice by yeast in sake brewing. Recent trends in the sake market have seen an increase in popularity in more aromatic sake types, and demand for these more luxurious types is rising. Due to their growing prominence, we were determined to look further into what effects these pleasant aromas have. However, until now there have been no detailed studies that consider the effects of smelling the aromas of sake. Furthermore, personal bias is a difficult challenge to overcome in research that aims to discover the effects of something as subjective as the appreciation of aroma. With this in mind, our experiments were designed with aroma preference, psychological and integrative physiological evaluation to discover a new appreciation of the aromas of sake, and in particular, the effects that ethyl caproate and isoamyl acetate compounds can have on the human mind and body.
Subjects of the trial were 18 women in good health in their 30s and 40s. Measurements were taken when breathing normally, with different samples of air, 15% ethanol as a control, and ethyl caproate or isoamyl acetate compounds (8 ppm added to 15% ethanol). A multiple mood scale was used to measure psychological and mood changes, while skin temperature and the miosis rate in pupillary light reflex was measured was observed to determine autonomic sensory changes, and thus physiological reactions to the smell. We also surveyed the subjects’ levels of preference towards the aromas. This experiment was performed after being submitted to the Ethical Review Board of Chiyoda Paramedical Clinic for approval, and consent forms received from the test subjects. Furthermore, this experiment does not represent any conflict of interest.
A Visual Analogue Scale (VAS) was used to determine the aromas’ relative perception and impression. Both ethyl caproate and isoamyl acetate received roughly the same points in each rating: preference, soothing aroma, elegant aroma, and relaxing aroma.
Ethyl caproate generated an overall stronger reaction in subjects than isoamyl acetate, with the ethyl caproate aroma having significantly higher score in particular floral, fruity, and sweeter than that of isoamyl acetate (p<0.05).
The effects of smelling these aromas on the mind and body are shown below.
Different effects of smelling ethyl caproate and isoamyl acetate
Before and after smelling the aroma samples, subjects’ mood and feelings were observed using the multiple mood scale and the VAS. After smelling ethyl caproate and isoamyl acetate samples, the scores for stress, desire, depression (anxiety), hostility and liveliness, perhaps reflecting heightened emotion and nervousness, were significantly decreased compared to before smelling the aroma samples.
［Left］Image of miosis rate measuring
［Right］Image of pupil diameter
The light reflex of pupil refers to the transient shrinking in size of the pupil (constriction) by light stimulation. This reaction is controlled by autonomic innervated muscle in the eyes. When in a relaxed state, the parasympathetic nervous system becomes dominant, and the miosis rate* should increase.
*Miosis rate = (pupil diameter prior to light stimulation (D1) – smallest pupil diameter after light stimulation (D2)) / D1
Compared to the miosis rate after smelling regular air and the control ethanol, miosis rate significantly increased after the subjects inhaled the ethyl caproate and isoamyl acetate samples, due to this reflex being controlled by the parasympathetic nervous system (p<0.01). We can therefore conclude that these two aromas have physiological sedative effects. Next, we investigated how these two aromas affect autonomic nervous system activity.
Recorded temperature increases after smelling isoamyl acetate sample
Image of skin temperature recording (forehead and finger)
When humans are nervous or stressed, there is a phenomenon that the fingertips grow colder. This reflex, and skin temperature as a whole, is also controlled by the sympathetic nervous system. As sympathetic nervous system activity is increased, i.e. the body enters a more aware, awake, or “on-edge” stressed state, peripheral blood vessels constrict, leading to reduced blood flow, and ultimately decreased skin temperature. On the contrary, when sympathetic nervous system activity is suppressed, i.e. the body enters a calm, relaxed state, peripheral blood vessels dilate, leading to greater blood flow, and higher skin temperature. Smelling the isoamyl acetate sample was proven to lead to a significantly greater increase in skin temperature than the increase in temperature after smelling air or the ethanol control. These results suggest that isoamyl acetate suppresses activity in the sympathetic nervous system, leading to dominance of the parasympathetic nervous system. Conversely, the ethyl caproate sample did not lead to a statistically significant change in skin temperature, suggesting that it possibly directly affects the activation of the parasympathetic nervous system. These two aromas both have physiological sedative effects, but the mechanisms are different.
Japan Society for Bioscience, Biotechnology, and Agrochemistry 2020 Annual Meeting
“The aromas of Japanese Sake have a physiological and psychological relaxing effect”
- Sachiko Suzuki, Yukihiro Yada, Miho Takeuchi, Hiroki Ishida
Yukihiro Yada: Effectiveness of fragrances and foods with function claims assessed by integrative physiological evaluation
Journey of Healthy Psychology Research Vol. 30, Page 259-269 (2018)