Taste-active substances

In literature standard concentrations may be stated but they usually refer to foods and beverages, not to bad tasting active substances. The necessary concentration very much depends on the taste and concentration of the active substance, pH etcetera, and only can be determined experimentally. For testing the performance of taste correction specific methods have been developed. 

Syrups (see Sect. 23.4.4) are widely used for the improvement of unpleasant tasting active substances. A disadvantage of using sucrose-containing syrups is that these are cario-genic bacteria in the mouth convert sucrose into acids, which cause cavities. 

The odor- and taste-active substances essentially determine the type of beer. The bitter taste of Pilsener beers is produced by relatively high concentrations of isohumulons, and humulenes (including oxidation products), while larger amounts of furaneol are responsible for the caramel note of dark beers. 

Swollen raw coffee can also be decaffeinated with supercritical CO2 (crit. point 31.06 °C 73.8 bar) at 40-80 °C and a pressure of 200-300 bar. The high vapor pressure of carbon dioxide under normal conditions guarantees a product that is free from solvent residues. Apart from the extraction of caffeine, this process can also be applied in the extraction of odor- and taste-active substances from hops and other plant materials. 

Depending on their origin, the odour- and taste-active substances can be divided into two basic groups ... 

Taste-active substances are usually water-soluble polar andnon-volatQe substances. Some taste-active substances may additionally be odour-active substances, but not necessarily. The complex (uniform) sensory perception of taste and smell is called flavour a strong pleasant smell, usually from food or drink is called aroma, and aromatic food or drink is that which has a pleasant smell. However, the term aromatic substance has a completely different meaning in organic chemistry. An aromatic substance, put simply, is a benzene derivative. The unwanted, altered, modified, unnatural or unpleasant odour, taste and flavour are called off-odour and off-taste or off-flavour, respectively. 

Glycols and polyols are non-volatile compounds that are formed in foods as secondary products of fermentation processes and of the Maillard reaction, or maybe used as food additives. Frequently occurring polyols present in foods are sugar alcohols, which act as taste-active substances. 

Volatile aldehydes and ketones are the most important odour-and taste-active substances. They occur in foods as primary substances, as components of various essential oils and also result from enzymatic and chemical reactions from various precursors as secondary substances. They are often desirable flavour-active components of foods, but in some cases may also carry undesirable odour and taste. Then they serve as indicators of unwanted changes in sensory or nutritional value of foods (such as autoxidation of lipids). 

Carbonyl compounds also include a range of non-volatile polar compounds, such as reducing sugars or some products of their transformation (degradation), which are often taste-active substances, usually with a sweet taste. A special group of carbonyl compounds are oxocarboxyUc acids and, in a broader sense, all carboxyhc acids, which often carry a sour taste. A special group of unsaturated diketones derived from aromatic systems are quinones, which are often significant natural dyes in foods. 

It is mainly the lower carboxylic acids and some aromatic carboxylic acids that are active as odour- or taste-active compounds. Taste-active substances are predominantly polyhydric carboxylic acids and some aliphatic carboxylic acids such as acetic and lactic acids, which are major carriers of the sour taste in food raw materials and foods. Short chain fatty acids also have some importance as flavour-active substances (C and Cg) and medium chain fatty acids (Cg-Ci2). A number of carboxylic acids can become precursors of important flavour-active derivatives, such as, for example, esters and lactones. 

Oral ingestion of food and other substances in humans and higher animals are inseparable from the subjective taste sensations. The stimulae for irritation of taste receptors localised in the mouth, especially on the tongue, are taste-active substances. They are usually polar, water-soluble and non-volatile compounds. The resulting sensation is usually a combination of fundamental and other tastes ... 

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