Mouthfeel is a product's physical and chemical interaction in the mouth, an aspect of food rheology

Food rheology

Food rheology is the study of the rheological properties of food, that is, the consistency and flow of food under tightly specified conditions. The consistency, degree of fluidity, and other mechanical properties are important in understanding how long food can be stored, how stable it will...

. It is a concept used in many areas related to the testing and evaluating of foodstuffs, such as wine-tasting and rheology

Rheology

Rheology is the study of the flow of matter, primarily in the liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force....

. It is evaluated from initial perception on the palate

Palate

The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...

, to first bite, through mastication

Mastication

Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...

 to swallowing

Swallowing

Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...

 and aftertaste

Aftertaste

Aftertaste is the taste intensity of a food or beverage that is perceived immediately after that food or beverage is removed from the mouth. The aftertastes of different foods and beverages can vary by intensity and over time, but the unifying feature of aftertaste is that it is perceived after a...

. In wine-tasting, for example, mouthfeel is usually used with a modifier (big, sweet, tannic, chewy, etc.) to the general sensation of the wine in the mouth. Some people, however, use the traditional term, "texture". Mouthfeel is often related to a product's water activity

Water activity

Water activity or aw was developed to account for the intensity with which water associates with various non-aqueous constituents and solids. Simply stated, it is a measure of the energy status of the water in a system...

, hard or crisp products having lower water activities and soft products having intermediate to high water activities.

Qualities perceived

• Cohesiveness: Degree to which the sample deforms before rupturing when biting with molar
  Molar (tooth)
  Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
  
  s.
• Density: Compactness of cross section of the sample after biting completely through with the molars.
• Dryness: Degree to which the sample feels dry
  Dry
  Dry or dryness may refer to:* Lack of water* Prohibiting alcohol * Dryness , the lack of sugar in a drink, especially an alcoholic one * Dryness * Dryness...
  
   in the mouth.
• Fracturability: Force
  Force
  In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
  
   with which the sample crumbles, cracks or shatters. Fracturability encompasses crumbliness, crispiness
  Crispiness
  Crispiness or crispness is the gustatory sensation of brittleness in the mouth, such that the food item shatters immediately upon mastication. Crispiness differs from crunchiness in that a crunchy food continues to provide its material sensation after a few chews...
  
  , crunchiness and brittle
  Brittle
  A material is brittle if, when subjected to stress, it breaks without significant deformation . Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses ...
  
  ness.
• Graininess: Degree to which a sample contains small grainy particles.
• Gumminess: Energy
  Energy
  In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
  
   required to disintegrate a semi-solid food to a state ready for swallowing.
• Hardness: Force required to deform the product to given distance, i.e., force to compress between molars, bite through with incisors, compress between tongue and palate.
• Heaviness: Weight
  Weight
  In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
  
   of product perceived when first placed on tongue.
• Moisture absorption: Amount of saliva
  Saliva
  Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
  
   absorbed by product.
• Moisture release: Amount of wetness/juiciness released from sample.
• Mouthcoating: Type and degree of coating in the mouth after mastication (for example, fat
  Fat
  Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
  
  /oil
  Oil
  An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
  
  ).
• Roughness: Degree of abrasive
  Abrasive
  An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away...
  
  ness of product's surface perceived by the tongue.
• Slipperiness: Degree to which the product slides over the tongue.
• Smoothness: Absence of any particles, lumps, bumps, etc., in the product.
• Uniformity: Degree to which the sample is even throughout; homogeneity
  Homogeneity and heterogeneity
  Homogeneity and heterogeneity are concepts relating to the uniformity or lack thereof in a substance. A material that is homogeneous is uniform in composition or character; one that is heterogeneous lacks uniformity in one of these qualities....
  
  .
• Uniformity of Bite: Evenness of force through bite.
• Uniformity of Chew: Degree to which the chewing characteristics of the product are even throughout mastication.
• Viscosity
  Viscosity
  Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
  
  : Force required to draw a liquid from a spoon over the tongue.
• Wetness: Amount of moisture perceived on product's surface.

Further reading

• Dollase, Jürgen, Geschmacksschule [engl.: Tasting School], 2005 Tre Tori, Wiesbaden
  Wiesbaden
  Wiesbaden is a city in southwest Germany and the capital of the federal state of Hesse. It has about 275,400 inhabitants, plus approximately 10,000 United States citizens...
  
  , Germany (ISBN 3937963200). German-language textbook by a renowned food critic covering some, but not all of the above mentionend properties/mouthfeelings.
• Katz, E.E. and Labuza, T.P. (1981) Effect of water activity on the sensory crispness and mechanical deformation of snack food products. J. Food Sci. 46: 403–409

External links

• http://www.decagon.com/food_science/info/safety.php Stability diagram outlining ranges where product crispness is lost.