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Analytical investigations to evaluate bitter sensation using a taste sensing system
Gastl, M., Hanke, S., Back, W.

The bitter impression created by hops is a special characteristic of beer. The range of bitter units in beer is normally between 20 and 50 IBU (International Bitter Units). Apart from their preservative effects hops are used to give the beer the right bitterness and aroma. [1] The influence of hops to the aroma and flavour of beer can be enhanced by the use of hop products and pre-isomerized hop products in the brewhouse or after fermentation.Iso-alpha-acids are intensely bitter and are the main origin of bitter flavour because they are responsible for more than 75 % of beer bitterness. [2] Beside the influence of iso-alpha-acids there are many other influencing factors, which affect the sensation of bitterness. The beer matrix is very complex and as a result of those various ingredients causes matrix effects and interactions between the ingredients. The matrix effects are able to cover the bitter sensation. This is already well known by the sensorial evaluation of flavour stability and ageing effects of beer. In this case for example the hop flavour could have a positive masking effect. A search of the literature reveals that humans have an inherent preference for sweet and umami and an inherent dislike for bitter and sour. The sensory perception is not linear nor is bitterness a taste attribute which is extremely well developed in human beings (compared to herbivorous animals) and is significantly influenced by matrix effects and therefore with regard to sensory aspects there is always a discrepancy in analytical measuring and sensory evaluation. [1] In cooperation with "TecLabS" we are testing an electronic tongue (Taste Sensing System SA402B, Intelligent Sensor Technology, Inc.) with regard to bitter sensation. The human gustatory system is able to detect very complex matrices and detects the taste as harmonic or inharmonic. The bitter sensation is a typical characteristic of beer and hopped beverages. Sensory evaluation in the food industry is usually done by a human taste panel. The problem with human panels is the motivation of the tasters, the availability and the physiological situation of the tasters. The project to test an analytical method to evaluate the bitter sensation against the sensory evaluation by a human taste panel was investigated together with the German company TecLabS using a Taste Sensing System which is already established in Japanese breweries. The Taste Sensing System mimics the human gustatory sensory system. This publication shows first results comparing the information from the Taste Sensing System with a human taste panel with respect to bitter taste sensations in aqueous solutions of different compositions. The investigations showed good correlation between the measurement of iso-alpha-acids and the human sensory panel. These trials are limited to the bitter sensation caused by iso-alpha-acids. Following this work the plan is to transfer the results in aqueous solution and to repeat the trials in beer matrix to get more information on matrix effects. It is noticeable that matrix effects have a great influence on the perceived bitter sensation. In beverage industry the term "drinkability" is commonly used. Nevertheless there is no uniform definition for the true meaning of the term "drinkability". Many different influencing factors are known, which are important for good drinkability. However drinkability is linked to the matrix composition of beer definitely. The composition of the matrix, especially a specific harmony, seems to be most important. In this context the bitter impression created by hops has to be considered and the influence of matrix effects on the sensorial bitter sensation. The use of an electronic tongue could potentially be used to help understand the complex subject of drinkability with regard to bitter sensation. ...

Descriptors: taste sensor, beer matrix, matrix effects, iso-alpha-acids, drinkability

BrewingScience - Monatsschrift fr Brauwissenschaft, 60 (March/April 2007), pp. 48-54