Fermented Flavourings

Enzymatic modification of milk fats with lipolytic enzymes has already been mentioned above. Besides this it is possible to manufacture complex cheese flavours today also by fermentation of raw materials of cheese processing with defined microorganisms. Roquefort and other blue cheese flavours fermented by the mould Penicil-lium Roqueforti are currently in commercial production. 

In China some teas, such as Pu-er tea, are made through microbial fermentation and called post-fermented teas. The typical characteristic of these teas is a mouldy or aged flavour the more intense this flavour, the better the quality. Other kinds of tea, such as white, yellow and dark, are produced in small quantities and consumed locally. Further processing of these teas produces scented and brick teas. 

Sour dough bread has a range of flavours that are not present in other bread also it keeps relatively well. The keeping properties, no doubt, originate from some of the products of the side-reactions that have taken place in the dough. There is no need to add propionic acid as a mould inhibitor as some is likely to be present naturally. Quite possibly, some of the substances produced by the fermentation would not be permitted as additives ... 

A larger proportion of wholemeal than white bread is still made by bulk fermentation methods. One reason for this is that although old fashioned wholemeal bread is a minority taste the minority who consume it like it that way. They like the close texture and flavour of the traditional product. 

Flavour of Spirit Drinks Raw Materials, Fermentation, Distillation, and Ageing... 

Table 10.1 gives a summary of the main by-products of fermentation by yeasts and other microbiological activities which can be identified in distilled spirits from different raw materials, like fruits, wine, grain, sugar cane, or other carbohydrate-containing plants. Since the sensory relevance of a flavour compound is related to its odour thresholds and odour quality. Table 10.1 presents also odour qualities and a review of threshold values of the fermentation by-products in ethanol solutions [9-10] and/or water [11-14] (Christoph and Bauer-Christoph 2006, unpublished results). 

Some of the volatile substances which are produced during fermentation, like acrolein, diacetyl, 2-butanol, allyl alcohol, or acetic acid, are a result of enhanced microbiological activities and may cause an unpleasant flavour (off-flavour) at certain levels thus, elevated concentrations of such compounds are markers for spoilage of the raw material, negative microbiological influences during or after the fermentation process, or a poor distillation technique. 

Fig. 10.1 Precursors, intermediates, and metabolites of the main groups of flavour compounds produced during alcoholic fermentation of carbohydrates by Saccharomyces cerevisiae yeast... 

The biosynthesis of fatty acids produced during alcoholic fermentation is initiated in the yeast cell by the formation of acetylcoenzyme A, which reacts with malonylcoenzyme A to form mainly saturated straight-chained fatty acids with an even number of four to 18 carbon atoms the appearance of relatively low levels of fatty acids with odd numbers of carbon atoms as well as unsaturated fatty acids depends on the fermentation conditions [6]. The volatile fatty acids contribute to the flavour of fermented beverages like wine or beer and their concentration usually lies between 100 and 250 mg 0.1 L p.e. In distilled spirits the concentration of free fatty acids is significantly lower owing to the esterification... 

Table 10.2 presents a summary of odour qualities, odour thresholds in water, and concentrations of some selected volatile compounds, which are characteristic flavour impact compounds, owing to their typical flavour quality and their rather low odour thresholds. These compounds are not formed during fermentation but originate from the raw material and contribute significantly to the typical flavour of a fruit. The components summarised in Table 10.2 are important compounds in wine and different fruits and are discussed later. 

Distilled spirits are produced from different fermented plant materials grown all over the world. The most important criteria of quality and authenticity of each type of distilled spirits are the typical flavour composition originating from the raw material and/or the special techniques of fermentation, distillation, and ageing. In the following sections, specific flavour compounds and flavour-related technologies as well as peculiarities of the most important categories of distilled spirits are summarised. 

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