Search: aroma perception

This simple descriptive analysis provides a method for articulately communicating sensory attributes. The method can be utilized to formulate a list of attributes for the profile test. The list of attributes must then be statistically corroborated and reference samples employed to ensure that all of the testers identify the same reference substance for each of the given attributes (e.g., rancid butter, sweaty = reference substance butyric acid).

A joint project in 2005 was organized by industry partners Hopsteiner, HVG and Johann Barth & Sohn along with the Central Marketing Organization of the German Agricultural Industries (CMA) and became known as the CMA scheme. This objective of this tasting scheme is to determine hop-related factors influencing the sensory analysis of beer.

First of all, the intensity and quality of the hop aroma and flavor are evaluated in their entirety according to a ten-point scale with 0 as unpleasant and 10 as very good/very pleasant. Then, the intensities of individual characteristics are also ranked on a ten-point scale, with 0 as imperceptible and 10 as very intense. For beer with a pronounced hop aroma, the following descriptors have become established in recent decades: fruity, floral, citrus, green-grassy and hop-spicy. These are available for specific training in the evaluation of hop oil fractions. Distinctive aromas detected by tasters can be described in the space provided. In order to characterize the overall impact of the hops, the bitterness is also evaluated sensorially. Both the intensity and the quality/harmony are evaluated on a ten-point scale, with 0 rated as completely lacking balance and 10 as very harmonious.

The mean values of the intensity of the hop aroma and flavor as well as the intensity of the bitterness are given on the score sheet (i.e., the sum of the scores divided by the number of tasters). The mean value of each aroma characteristic is reproduced as a spider diagram. The individual values should be checked for outliers prior to the calculating the mean. Since quality assessments are subjective by nature, the mean values can only be of limited value. However, they can be beneficial in determining whether any distinctive aroma or flavor characteristics were judged by the majority to be pleasant or unpleasant. The same applies to assessing the quality of the bitterness. 

Terms

Aroma:
Aroma represents the overall sensory impression encompassed by the olfactory organs, some of which is perceived in the mouth and thus partly attributed to the sense of taste.

Flavor/Off-flavor:
For the sake of thoroughness, these two terms, which are defined in DIN 10950 part 2 Sensorische Prüfung, allgemeine Grundlagen, are mentioned here. According to definition put forth by DIN, flavor is defined as the “sum of olfactory, gustatory, temperature-related and/or trigeminal and tactile sensations in the mouth”. Off-flavors are sensory stimuli, which are perceived as unpleasant.

Odor:
Organoleptic properties perceived with the olfactory organ(s), whereby certain volatile substances are breathed in through the nose.

Flavour:
The overall sensory impression perceived through the sense of taste in the mouth, throat and nose. The sense of taste can be influenced by thermal or tactile stimuli, through pain or kinesthesia or any combination thereof. According to DIN, flavor is defined as the “sum of olfactory, gustatory, temperature-related and/or trigeminal and tactile sensations in the mouth”.

Mouthfeel:
Aside from the basic tastes, tactile stimuli – detected through haptic perception in the oral cavity – play a role in the sensory perception of comestibles as they are ingested. Tactile stimuli can be divided into the following:

• tactile (touch)

• kinesthetic (perception of weight, movement, resistance, etc.)

• trigeminal (pain)

• temperature-dependent

The term “mouthfeel” is often employed to describe haptic perception in the oral cavity. The following sensory attributes of beverages can be detected primarily by means of mouthfeel:

• viscosity, rheological properties

• liberation of gas, bubble formation, foaming (carbon dioxide)

• general after-effects in the mouth (refreshing, warming, thirst-quenching)

Aftertaste:
The sensory impression, which remains in the mouth, once a beverage has been swallowed. This is often employed as a criterion for the sensory evaluation of beverages.
An aftertaste described as “harmonious” provides incentive to continue drinking.

Orthonasal perception of odors:
Sensory perception commonly referred to as “smelling”. Odorants in the air enter the nasal cavity through the external nares, or nostrils, during the act of breathing. From there, the odorants are transported to the receptor cells where olfactory perception occurs.

Retronasal perception of odors:
Retronasal (lat. retro: “backwards, back”, nasal: “pertaining to the nose”) perception describes the transport of odorants from the oral cavity into the pharynx, then up through the internal nares and nasal cavity to the olfactory receptor cells. Odors are liberated through the mastication of food and beverages, thus providing olfactory (lat. olfacere: “to smell”) stimulus. The retronasal aroma profile of comestibles may differ from the orthonasal aroma profile owing to various factors (e.g. mastication or saliva).

Fullness:
Fullness is a kinesthetic sensation in the oral cavity, which – as it relates to beer – may range from “watery” to “satiating/excessive”. A frequently used synonym for fullness in beer is the term “body”.

Liveliness:
Liveliness as it pertains to beer is the tactile sensation in the oral cavity induced through the action of carbon dioxide, which may range from “flat/stale” to “gassy”.
A synonym often encountered for liveliness is “effervescence”.

The aroma compounds in hops are driven out through steam distillation and are captured in a special apparatus. The determination is carried out through reading the volume transferred into the apparatus.

Kaltner (2000) developed a score sheet for assessing beers with a strong hop flavor, which on one hand is based on the DLG quality assessment of beer (refer to S.590.53.700 Einzelprobenprüfung zur Qualitätskontrolle von Bier - DLG-Prüfschema für Bier). The criteria aroma, flavor, fullness, liveliness and bitterness are evaluated using a five-point scale in half-point steps, where 5 denotes a pure attribute and 1 indicates major faults. On the other hand, the quality and distinction of the hop aroma and bitterness are assessed. The aroma and flavor of the hop impression are also distinguished. The evaluation is also based on a five-point scale with an intensity of 5 corresponding to the attribute “perfume-like” and 1 to “not perceptible”. Under “quality of the hop aroma” a score of 5 is considered “pleasant” and 1 “unpleasant”. Additionally, the score sheet provides space for describing the sensory impression of the appeal of a particular hop note. The intensity of the bitterness is also evaluated on a five-point scale, and in this case, 5 denotes a very strong impression, and 1 a very weak one.

The appeal of the bitterness has been plotted on a graph and is expressed using the following terms:

• rapidly diminishing (low intensity)

• fine, harmonious (moderate intensity and pleasantly lingering)

• hard (high intensity and fleeting)

• lingering (high intensity and persistently lingering)

One of the fundamental prerequisites for a properly structured sensory evaluation of beverages is training members of the tasting panel.