Engineering Properties of Biological Materials and Food Quality 3(2+1)

Lesson 17. Concept of Flavor in food quality

Definition of Flavor

1. “Flavor is the sensation produced by a material taken in the mouth, perceived principally by the senses of taste and smell, and also by the general pain, tactile, and temperature receptors in the mouth. Flavor also denotes the sum of the characteristics of the material which produces that sensation.”

2. “ Flavor is one of the three main sensory properties which are decisive in

the selection, acceptance, and ingestion of a food.

3. “A mingled but unitary experience which includes sensations of taste, smell, and pressure, and often cutaneous sensations such as warmth, color, or mild pain”.

How do we recognize flavor:

The five basic taste sensations are mediated by specialised epithelial cells, the taste receptor cells,that are located within the taste buds of the papillae on the surface of the tongue. These elongated taste receptors cells are deeply embedded in the surrounding epithelium and just contact the outside world in the gustatory porus of the taste buds. Thus, the porus is the place where tastants interact with the taste receptor molecules that are located at the apical site of the taste receptor cells. In contrast to obsolete textbook knowledge, humans can perceive all taste qualities on any area of the tongue that contains papillae.  Only the perceived intensities of the taste qualities differ depending on the tongue region and papilla type. Sweet taste saccharin for instance is highest at the tip of the tongue whereas the bitter taste of quinine is best perceived at the back of the tongue. Interestingly, the anterior part of the tongue is innervated by the VII cranial nerve whereas the posterior part of the tongue is innervated by the IX cranial nerve. These innervations are also reflected by the distribution of the taste papilla types. The fungiform papillae are located at the anterior part of the tongue and thus are innervated by VII cranial nerve. In contrast, the foliate and vallate papillae that is located at the back of the tongue that is innervated by the IX cranial nerve. This nerve also innervates isolated taste buds in the palate and epiglottis.

Fig. Human Tongue and taste areas on the human tongue

Fig. Human Olfactory system

Flavor is typically described by aroma (odor) and taste. Aroma compounds are volatile—they are perceived primarily with the nose, while taste receptors exist in the mouth and are impacted when the food is chewed. While color and appearance may be the initial quality attributes that attract us to a food product, the flavor may have the largest impact on acceptability and desire to consume it again.

The five basic taste qualities are exclusively mediated by specialized epithelial receptor cells that are located in taste buds. Most taste buds lie within taste papillae on the human tongue, but some of them are also distributed on the palate and epiglottis. The taste buds in the oral cavity are innervated by gustatory fibres of the VII, IX and X cranial nerve.

Thus, the perception of Taste has been divided into five primary tastes:

• Sweet: Sweet taste is predominantly elicited by carbohydrates and indicates energy-rich food sources.

• Sour: Strong sour taste is also repulsive and prevents the ingestion of unripe fruits and spoiled food, which often contain acids.

• Salty: Salt taste is elicited by sodium chloride and other salts and contributes to electrolyte homeostasis, salt taste is attractive at low concentrations and repulsive at high concentrations.

• Bitter:  Bitter taste is evoked by many compounds that belong to multiple chemical classes.  The common denominator of most bitter compounds is their pharmacological activity or toxicity. Therefore, due to its task to avoid harmful compounds strong bitter taste is aversive. Nevertheless humans can accept moderate bitter taste or even find it attractive. A reasonable explanation for this observation is that bitter and sour tastes should not deter us from advantageous food containing low concentrations of harmful compounds.

• Umami(a taste associated with salts of amino acids and nucleotides): The broth-like umami taste, that is mainly triggered by glutamate and enhanced by ribonucleotides such as inositol monophosphate (IMP), identifies protein-rich food.

Odors are much more diverse and classified as:

• Spicy:

• Flowery: 

• Fruity: 

• Resinous or balsamic:

• Burnt:

• Foul:

Flavors in food:

• Desirable flavor: orange juice, potato chip, roast beef

• Undesirable flavors: oxidized, stale, rancid, warmed-over

Classification of flavors:

Flavor class	Subdivision	Representative sample
Fruit flavour	Citrus type flavor (terpeny) Berry type flavor (non- terpeny)	Grape fruit , orange Apple, banana
Vegetable flavour		Lettuce, celery
Spice flavor	Aromatic Lachrymogenic hot	Cinnamon, peppermint Onion, garlic Pepper, ginger
Beverage flavor	Unfermented flavor Fermented flavor Compounded flavor	Juices, milk Wine, beer, tea Soft drinks
Meat flavor	Mammal flavor Sea food flavor	Lean beef Fish, clams
Fat flavor		Olive oil, coconut fat, pork fat, butter fat
Cooked flavor	Broth Vegetable Fruit	Beef bouillon Legume, potatoes marmalade
Processed flavor	smoky flavor Broiled, fried flavor Roasted , toasted, baked flavor	Ham Processed meat products Coffee, snack foods, processed cereals
Stench flavor		cheese

 

 

Other Factors That Affect Flavor Perception                        

• Temperature

• Consistency

• Presence of contrasting tastes

• Presence of fats

• Color

Sources of flavors

• Natural flavors

• herbs and spices (Reaction after cutting)

• Fruit (Biosynthesis during ripening)

• Process flavors

• browning

• lipid oxidation

• fermentations

• Artificial flavors

• character impact compounds

Food Flavor Profiles:

• Top notes or high notes: The sharpest first flavors or aromas

• Middle notes: The second wave of flavor, more subtle

• Low notes: The most dominant lingering flavor

• Aftertaste or finish: The final flavor

• Roundness: The unity of a dish’s various flavors

• Depth of flavor: A broad range of flavors

Mechanism of flavor development:

• Enzymatic reaction: Volatile flavors developed in most food plants mainly at   the ripening stage - the result of plant metabolism through enzymatic reaction.

• Non-enzymatic reaction: Raw meat must be heated before it develops any  organoleptically acceptable flavor, flavor development in baked cereals, nuts, coffee etc.

Flavor analysis: Flavor may be evaluated with either instrumental or sensory methods, but most scientists would agree that sensory methods are the most critical to this particular quality attribute. Instrumental techniques may determine that tens or hundreds of compounds are present in a particular food product, but such methods do not give a measure of the contribution of that specific compound unless they are accompanied by a sensory measurement of odor or flavor activity. For this reason, flavor may be the most challenging quality attribute to both measure and correlate to consumer acceptability. There are some characteristics of flavor that may be determined instrumentally.

• Sensory Analysis

• Discrimination tests

• Difference tests

• Threshold tests

• Analytical intensity rating testsConsumer tests

• Types of scales

• Descriptive analysis

• Time-intensity

• Consumer tests

• Instrumental Methods

• Flavor Identification by Spectrometric MethodsElectronic nose

• Ultra Violet Spectrometry

• Infrared Spectrometry

• Nuclear Magnetic Resonance Spectrometry

• Mass Spectrometry

• Electronic nose

Sweetness can be approximated by HPLC determination of individual sugars, or more rapidly but less accurately by a refractometer or hydrometer that measures total soluble solids. Indicator papers exist for rapid determination of glucose in some commodities, such as potatoes. It is possible to measure chloride and/or sodium content as an approximation of saltiness. Sourness may be determined by either pH or more accurately by measurement of total acidity. Both indicator papers and pH meters are available for the determination of pH. Astringency may be indicated by measuring total phenolics and bitterness by analysis of compounds such as alkaloids or glucosides.

Some terms in flavor:

1)    Seasoning: An item added to enhance the natural flavors of a food without changing its taste, eg. Salt is the most common seasoning.

2)    Flavoring: An item that adds a new taste to food and alters its natural flavors, eg.  Herbs (Any of a large group of aromatic plants whose leaves, stems or flowers are used as a flavoring, used either dry or fresh), spices (Any of a large group of aromatic plants whose bark, roots, seeds, buds or berries are used as flavoring. Usually used in dry form, whole or ground), vinegars and condiments (Any item added to a dish for flavor, including herbs, spices and vinegars. Also refers to cooked or prepared flavorings such as prepared mustards, relishes, bottled sauces and pickles).

Reference:

Barrett, D. M., Beaulieu, J.C. and Shewfelt, R. (2010). Color, Flavor, Texture, and Nutritional Quality of Fresh-Cut Fruits and Vegetables:  Desirable Levels, Instrumental and Sensory Measurement, and the Effects of Processing, Critical Reviews in Food Science and Nutrition, 50: 5, 369-389.

Voilley A. and Etievant P. (ed). 2006. Flavour in food. WOODHEAD PUBLISHING LIMITED, Cambridge, England.