The Sensory Philosophy Behind Deliciousness: Unveiling the Chemical Mechanisms and Physiological Effects of Aroma and Taste

Nutrients in food can be broadly categorized into three types based on their function. First, nutrients that provide energy or calories: carbohydrates are the cheapest energy source; lipids produce the most energy per unit weight; proteins are also an energy source, but their more important role is as a building block of the body. Second, nutrients that regulate bodily functions: vitamins and some minerals. Third, nutrients that constitute body tissues and replenish energy: water, proteins, and minerals.

Before even starting a meal, we first notice the color and shape of the dishes. The sizzling sound and aroma of meat grilling on a hot griddle greatly stimulate your appetite. Once the food enters your mouth, you can savor its flavor and experience its texture. In addition, there's the sensation of beer going down your throat, the warming feeling in your stomach when drinking whiskey, and so on. What we call deliciousness is a comprehensive sensory experience of the various physical and chemical properties of food, perceived through our senses of taste, smell, hearing, sight, and touch. Among these, aroma and flavor are paramount.

Experiments show that when one cannot perceive aroma, it is impossible to distinguish between pineapple juice, apple juice, and orange juice. In Europe, where meat consumption is high, there is a strong demand for spices such as pepper, which originate from the tropics. Columbus's discovery of the New World (1492) and Magellan's circumnavigation of the globe (1519) were essentially undertaken in search of spice-producing regions. The Netherlands, Spain, Portugal, and England were once among the most developed countries in the world. Aroma is the result of the interaction between approximately 20 million olfactory cells located in the olfactory mucosa of the upper nasal cavity and flavor molecules.

This stimulus undergoes various modifications (chemical changes) in the olfactory bulb, tonsils, and lower optic nerve before reaching the olfactory center, where the scent is perceived. Light is an electromagnetic wave with a wavelength of 380–780 nanometers; sound is a vibrational wave with a wavelength of 16–20,000 Hz. Both are physical phenomena. Odor, however, is different; it is the result of a chemical reaction between odor-producing substances and olfactory cells. Various theories have been proposed regarding how odor stimulates olfactory cells. In 1890, Augur proposed that odor-producing substances act on olfactory neuropigments, generating heat, which is the olfactory factor.

In addition, there are vibrational theories such as the molecular ultraviolet theory, the absorption vibration theory related to the Raman effect, the absorption of infrared radiation emitted by the olfactory part of flavor molecules, and the resonance theory of olfactory nerve electrical vibration and flavor molecule vibration, as well as chemical theories such as the two binding parts theory of flavor molecules and the aroma-generating group theory. Recently, a strong theory has emerged: the physicochemical theory, which states that flavor molecules embed themselves into cavities on olfactory cells that match their shape, thus producing an odor. However, flavor substances are extremely numerous, and this theory cannot explain them all. It can be said that, to date, there is no definitive theory regarding the mechanism of olfaction.

In daily life, we all have the experience that the aroma of barbecue immediately stimulates our appetite, while an unpleasant odor can cause nausea or even vomiting. This suggests that odors have a strong influence on the digestive system. Furthermore, odors have various physiological functions. Numerous experiments have reported on the effects of odors on the reproductive and endocrine systems. Odors also affect the respiratory system; when we smell an unpleasant odor, we reflexively hold our breath; conversely, when we smell a pleasant odor, we instinctively take a deep breath.

Experiments have shown that upon smelling ammonia or chloroform, blood pressure initially decreases, then subsequently rises. However, it remains unclear whether this is a direct effect of the sense of smell on the circulatory system, or an effect of the odor molecules on the circulatory system through blood flow after inhalation. Furthermore, salmon and sturgeon migrate from the ocean to rivers to reproduce, often choosing tributaries. Their migratory ability stems from their keen olfactory memory of water scents, allowing them to locate their breeding grounds. Several experiments have confirmed this.

Preferences for food aromas can change. These preferences differ based on ethnicity, gender, and age. For example, women tend to prefer strawberries more than men because men and women have different tastes in their preferred aroma. Girls around 10 years old especially love strawberries, but this preference gradually decreases with age. The Japanese enjoy the aromas of yuzu, Sichuan peppercorns, and wild jasmine, while recently avoiding strong smells like garlic. However, neighboring South Korea has a particular fondness for garlic. This is quite interesting.

In the past, fresh, live food was readily available in Japan. Fresh vegetables and live fish had excellent flavor. Japanese cuisine often used fresh ingredients with subtle aromas, such as cauliflower and mushrooms, to create unique dishes. However, obtaining fresh food ingredients has become increasingly difficult. Moreover, the development of processed and cooked foods, the increasing consumption of oils and meat products, the Westernization of dietary habits, and the popularity of traditional Japanese cuisine are all contributing to the rapid changes in Japanese food culture.

Recently, there has been an increase in the use of Western-style spices and vegetables with Western flavors, such as celery, onions, and tomatoes. Beverage preferences have also changed, shifting from a preference for green tea to a fondness for coffee, black tea, Coca-Cola, and oolong tea. There's also a shift from a preference for medicinal flavors to a preference for spices, and this trend is expected to intensify in the future. Some foods don't inherently have a special aroma, but adding even a tiny amount of a certain substance can significantly enhance their flavor; this substance is called a flavor enhancer.

If you soak shiitake mushrooms in water, enzymes will produce mushroom flavoring. Adding just one part per million of this mushroom flavoring to food will make it incredibly delicious. It's estimated that substances with similar effects exist in other spices as well. The aroma perceived before food is eaten is called fragrance, while the taste perceived while eating is called flavor. Whether it's fragrance or flavor, the taste and aroma of food are ultimately a combined sensation from the senses, including the tongue.