Flavors and Aromatic Compounds in Foods Comprehensive Notes

Flavors and Aromatic Compounds in Foods

Definition of Flavor

• Flavor substances encompass a wide range of chemical structures derived from major food constituents.

• Their common feature is stimulating taste or aroma receptors to produce an integrated psychological response known as flavor.

Overview

• Nonspecific or neural responses contribute to flavor perception by detecting pungency, cooling, umami, or delicious attributes.

• Non-chemical senses (sight, sound, and feeling) influence the perception of tastes and smells.

• "Flavor" implies an overall integrated perception of smell, taste, sight, feeling, and sound during food consumption.

Flavor Perception

• Gustatory, olfactory, and oral-somatosensory cues contribute directly to flavor perception.

• ISO 5492 1992 definition: Flavor is a "complex combination of the olfactory, gustatory and trigeminal sensations perceived during tasting."

• ISO 5492 2008 definition: Flavor may be influenced by tactile, thermal, painful, and/or kinesthetic effects.

Multisensory Perception

• Flavor is initially influenced by receptors in the eyes, nose, tongue, and mouth lining.

• The brain interprets the overall sensation occurring in the mouth (Taylor and Hort, 2004).

Smell (Aroma)

• Aroma can be sensed orthonasally (sniffed through the nostrils).

• Aroma compounds can reach the olfactory receptors retronasally via the throat after mastication (Taylor and Hort, 2004).

• The olfactory epithelium in the nasal cavity detects trace amounts of volatile odorants, accounting for variations in odor and flavor intensity and quality.

Taste

• Taste sensations (sweetness, sourness, bitterness, saltiness, and umami) are detected by taste buds in the oral cavity.

• Taste buds are found on the surface of the tongue in papillae.

• Four types of papillae: fungiform, filliform, foliate, and circumvallate (Meillgaard et al., 2007).

Touch

• The sense of touch is divided into somesthesis, kinesthesis, and chemesthesis (Kemp et al., 2009).

• Somesthetic sensation perceives force and particle size (Meilgaard et al., 2007).

• Nerve fibers sense tension and relaxation kinaesthetically, giving rise to the perception of sensory attributes of hardness and heaviness (Kemp et al., 2009).

Chemesthesis

• Chemesthesis is the chemical sensitivity of the skin and mucous membranes.

• It allows for the perception of hot, burning, tingling, cooling, or astringent sensations (Green, 2004).

Texture Evaluation

• Texture assessments are mainly performed in the mouth.

Sound

• Sound is sensed by tiny hair cells in the ear stimulated by vibrations (Kemp et al., 2009).

• The noise emitted by food during chewing/biting indicates texture, e.g., crispness of lettuce, crunchiness of an apple (Verhagen and Engelen, 2006).

• Acoustic emissions require a crack speed of ~$300-500 m/s for foods to be perceived as crispy (Luyten and Van Vliet, 2006).

Sight

• The color of a food/drink influences flavor identification (DuBose et al. 1980; Hall 1958; Kanig 1955; Levitan et al. 2008; Moir 1936; Oram et al. 1995; Shankar et al. 2009; Stillman 1993; Zampini et al. 2007, 2008).

Food Flavor – Physical Stimuli & Perception

• Physical Stimuli:

  • Light

  • Food Matrix

  • Temperature

  • Mastication

  • Volatile and non-volatile release

  • Auditory

  • Thermal

  • Tactile

  • Volatiles Composition

• Physiology:

  • Activation of sensory systems

    • Olfaction

    • Somatosensations

    • Taste

    • Vision

  • Saliva

  • Imitation

• Perception:

  • Central cognitive processing of information

  • Potential interactions within and between modalities

• Leads to Perceived Flavor of Food

Flavour Sensation and Components

• Flavour Sensation is composed of:

  • 70% Volatile Aroma Compounds

  • 30% Taste Compounds, Texture, Temp, Kinesthetic Effect, Sound

Uniqueness of Flavor Substances

• The uniqueness of many flavor substances relies upon their ability to stimulate the olfactory organ (Stanly and Yan, 2000).

Chemistry of Flavor

• Flavor is caused by receptors in the mouth and nose detecting chemicals found within food.

• These receptors produce signals interpreted by the brain as sensations of taste and aroma.

• Certain taste and aroma combinations are characteristic of particular foods.

• Example: A green apple's taste is due to the unique combination of chemicals perceived as a blend of sweet and sour tastes and volatile aromas.

Complex Chemistry of Flavor

• One natural flavor may contain hundreds or thousands of component substances, some in minute quantities.

• Example: One of the nine key aroma compounds in pineapple is detectable at 6 ppt (equivalent to a few grains of sugar in a 50m, 12-lane swimming pool).

History - Taste

• Aristotle (350 BCE) postulated that the two most basic tastes were sweet and bitter.

• Ayurveda (5000 BCE), an ancient Indian healing science, includes sweet, salty, sour, pungent, bitter & astringent as basic tastes.

• Ancient Chinese regarded spiciness as a basic taste.

Tastes

• Bitter

• Sour

• Sweet

• Salt

• Umami

Sour

• H^+ ions.

• Concentration is proportional to taste intensity among inorganic ions.

• Organic ions are stronger than inorganic ions at the same concentration.

• The intensity of taste depends on the potential of the acid (i.e., A weak acid tastes the same as a strong acid at the same concentration).

• Examples: Acetic acid, Citric acid, Tartaric acid, Lactic acid, gamma-amino butyric acid (decarboxylation of glutamic acid).

Salt

• Na^+

• K, Ca & Mg salts of adipic, succinic, glutamic, carbonic, lactic, hydrochloric, tartaric and citric acids.

• Monopotassium phosphate, adipic and glutamic acids and potassium sulfate.

• Choline salt of acetic, carbonic, lactic, hydrochloric, tartaric and citric acids.

• Potassium salt of guanylic and inosinic acids

• Sodium chloride is sweet at low (e.g., 0.020 M), but salty at higher (0.050 M) concentrations.

Sweet

• Lactose, Glucose, Maltose, Sucrose

• Glycerol

• Mannitol, Maltitol, Xylitol

• Ketones (after exercise)

• Saccharine

• Aspartame

Bitter

• Phenolic compound

• Cinnamic acid

• Tannins to Green Tea

• Glycocidic compounds

• Nicotine to Pan Beetle Mix

• Caffeine to Coffee

• Alkali metals

• Inorganic salts of Mg, Ca, NH_4^+ to hard water

Umami

• Glutamate

• Glutamic acid

• Specific ribonucleotides

• Salts of glutamic acid

• Salts of glutamate:

  • MSG

  • KG

  • CaG

Structure and Functional Groups

• Esters

• Linear terpenes

• Cyclic terpenes

• Aromatic

• Amines

Esters

• Geranyl acetate – Rose

• Methyl acetate – sweet nail polish

• Methyl propionate – Rum like

• Methyl butyrate – pineapple

• Ethyl acetate – wine

• Ethyl butyrate – Orange

• Isoamyl acetate – Banana

• Pentyl butyrate – Pear

• Pentyl pentanoate - apple

Linear Terpenes

Cyclic Compounds

Aromatic

Amine

Functional Group

• Alcohol – Furaneol, Menthol, cis-Hehanol

• Aldehydes – Acetaldehyde, Cinamaldehyde, Cuminaldehyde

• Esters – Frutone, Ethyl methylphenylglycidate

• Ketones - Oct-1-en-3-one (blood, metallic, mushroom-like)

• Lactones - gamma-Decalactone intense peach flavor, gamma-Nonalactone coconut odor

• Thiols - Allyl thiol (2-propenethiol; allyl mercaptan; CH2=CHCH2SH$$) (garlic volatiles and garlic breath)

Oholf Classification

Natural Flavorings (FDA Definition)

• The essential oil, oleoresin, essence or extractive, protein hydrolysate, distillate, or any product of roasting, heating or enzymolysis.

• Contains flavoring constituents derived from a spice, fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, seafood, poultry, eggs, dairy products, or fermentation products thereof.

• Significant function in food is flavoring rather than nutritional.
  //refers to substance with significant function is seasoning rather than nutritional

Natural Flavoring (European Definition)

• "Natural flavours” and “Natural Flavouring substances” means flavour preparations and single substance respectively, acceptable for human consumption, obtained exclusively by physical processes from vegetables, sometimes animal raw materials, either in their natural state or processed for human consumption.

Nature Identical (FSSAI Definition)

• “Nature-identical flavoring substances” means substances chemically isolated from aromatic raw materials or obtained synthetically.

• They are chemically identical to substances present in natural products intended for human consumption, either processed or not.

• Nature identical in EU but Artificial in US+

Artificial Flavoring (FDA Definition)

• Any substance, the function of which is to impart flavor, which is not derived from a spice, fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, fish, poultry, eggs, dairy products, or fermentation products thereof.

Artificial Flavoring (FSSAI Definition)

• “Artificial Flavouring substances” means those substances which have not been identified in natural products intended for human consumption either processed or not.

Spices (FDA Definition)

• Any aromatic vegetable substance in the whole, broken, or ground form, except for those substances which have been traditionally regarded as foods, such as onions, garlic and celery.

• Significant function in food is seasoning rather than nutritional; that is true to name; and from which no portion of any volatile oil or other flavoring principle has been removed.

Maillard Browning

• When aldoses or ketoses are heated in solution with amines, a variety of reactions ensue, producing numerous compounds, some of which are flavors, aromas, and dark- colored polymeric materials, but both reactants disappear only slowly.

• The flavors, aromas, and colors may be either desirable or undesirable.

• They may be produced by frying, roasting, baking, or storage.

Maillard Browning

• Amino acid + Sugar → Maillard reaction

Thermal Degradation of Thiamine

• Thermal degradation of Thiamine produces Thiazoles