Food Flavors and Sensory Perception

Definition of Flavor

Flavor refers to the overall sensory experience produced when a substance is consumed. It is primarily perceived by:

• Taste: The sensation detected by taste buds on the tongue, which can sense five basic tastes—salty, sweet, sour, bitter, and umami.
• Smell (Odor): The aroma of food, detected by olfactory receptors in the nose.
• Other Sensory Receptors: Additional sensations are sensed by general pain, tactile, and temperature receptors in the mouth, contributing to the feeling of texture and temperature, which also affect the perception of flavor.

Flavor is a complex interaction of these sensory experiences and plays a vital role in food selection, acceptance, and ingestion. Along with appearance (which includes size, shape, and color) and kinesthetics (which refers to texture and consistency), flavor is a key determinant of how food is perceived and enjoyed.

Components of Flavor

1. Taste: The basic sensations detected by taste receptors on the tongue, including:
   • Salty: Perceived due to the presence of sodium chloride.
   • Sweet: Caused by sugars like sucrose.
   • Sour: Resulting from acids like citric and tartaric acid.
   • Bitter: Often associated with compounds like quinine.
   • Umami: A savory taste often associated with glutamic acid, found in foods like meats and aged cheeses.
2. Odor: The aroma detected by the olfactory system is composed of various compounds that contribute to the overall flavor. Common odor types include:
   • Camphoraceous: E.g., camphor.
   • Pungent: E.g., formic acid (found in mustard).
   • Etheral: E.g., chloroform.
   • Floral: E.g., terpineol.
   • Pepperminty: E.g., menthone.
   • Musky: E.g., androsan-3-ol.
   • Putrid: E.g., skatole.

Flavor Compounds Flavor compounds, particularly volatile ones, contribute to the aroma and overall flavor of food. These compounds include aliphatic esters, aldehydes, ketones, and others.

Types of Flavoring Compounds:

1. Flavonoids: Found in citrus fruits (like oranges and lemons), flavonoids contribute to the flavor of these fruits. Examples include hesperidin (tasteless) and naringenin (bitter), which are glycosides found in fruit peels.
2. Terpenoids: Common in plants, terpenoids contribute to the flavor of citrus fruits and other aromatic plants. Limonene is a major component of citrus oils, making up about 90% of their composition.
3. Sulfur Compounds: Volatile sulfur-containing compounds play a role in the aroma of foods like onions, garlic, cabbage, cauliflower, and broccoli. These compounds belong to classes like thioglucosides and isothiocyanates, contributing to the distinctive smell of these foods.
4. Other Volatile Flavor Compounds: Foods can be classified based on the complexity of their aromatic compounds:
   • Single Compound Aroma: Some foods have a dominant aroma from a single compound, such as banana (isopentyl acetate), lemon (citral), or almonds (benzaldehyde).
   • Mixture of Compounds: Certain foods like apples contain a small number of compounds contributing to their aroma (e.g., 2-methyl butyrate as the main component).
   • Complex Mixtures: Foods like pineapple and walnuts have a more complex mixture of compounds that contribute to their aroma.
   • Unique Aromas: Some foods, like strawberries and chocolate, have unique aromas that cannot be easily reproduced by a mixture of compounds.

Classes of Volatile Flavor Compounds:

• Carbonyl Compounds: Examples include acetaldehyde (butter), hexanal (apples), benzaldehyde (almonds, cherries), geranial (lemon), and 2-3-butanedione (butter, celery).
• Acids: Compounds like acetic acid (vinegar) and 2-methylbutyric acid (cranberries) contribute to sourness or tangy flavors.
• Esters: Found in various fruits, esters like pentyl acetate (banana), octyl acetate (orange), and ethyl butyrate (strawberry) are responsible for sweet and fruity aromas.
• Hydroxyl Compounds: Examples include cis-3-hexen-1-ol (tomato, raspberry), 1-octen-3-ol (mushroom), phenol (some cheeses), and eugenol (cloves), contributing to earthy, spicy, or herbal flavors.

Types of Flavors

Flavors can be broadly categorized into three types based on how they are developed:

1. Developed Flavor: This flavor results from the food processing methods, including chemical reactions such as decomposition, fractionation, or other processes (e.g., the creation of perfumes or complex chemical reactions in cooked foods).
2. Processed Flavor: Processing through heating or cooking can change the flavor of many compounds. For example, roasting coffee beans or peanuts can develop unique flavors through the Maillard reaction or caramelization.
3. Added Flavor: Some flavors are deliberately added to foods:
   • Essential Oils or Oleoresins: These are extracts from aromatic plants, such as peppermint oil, that impart characteristic flavors to food.
   • Synthetic Flavors: These are man-made flavor compounds that may mimic naturally occurring substances. Examples include benzaldehyde (almond), acetylmethylcarbinol (butter), citral (orange), eugenol (clove), limonene (lemon), and vanillin (vanilla).

Flavor Enhancement Flavor enhancement involves using specific compounds that intensify or improve the perceived flavor of foods.

1. Monosodium Glutamate (MSG): MSG is a flavor enhancer derived from glutamic acid found in wheat gluten, beet sugar waste, and soy protein. It imparts a unique savory taste known as umami. It is commonly used in processed foods like meats, poultry, soups, and vegetables. MSG is known for enhancing the flavor without overpowering it and is especially effective when used with salt.
2. Maltol: Maltol is a compound that enhances sweetness and is formed during the roasting of malt, coffee, cacao, and grains. It also forms in the crust of bread during baking. Maltol has antioxidant properties and increases the storage life of products like coffee and roasted cereals. It is used as a flavor enhancer in chocolates, candies, ice cream, baked goods, instant coffee, tea, liqueurs, and flavorings.