Burnt flavours

Canning of liver sausage encounters a problem from the formation of burnt off-odours,271 the intensity of which was found to be linearly related to the loss of free Gly, Glu, and Thr in model experiments. Addition prior to canning of reduced glutathione left flavour and colour unaffected, but the addition of /V-acctylcystcinc inhibited burnt flavour formation, optimally at 0.15%.272 However, an acid taste developed, but was prevented by the further addition of 0.25% diphosphate. 

It shall be manufactured under hygienic conditions, light to dark brown in colour, and the flavour should be characteristic of tamarind fruit. No burnt flavour should be present. It shall be free from harmless extraneous vegetable materials (fibre and rind common to tamarind, and stems up to... 

Amongst furans are several compounds of great importance in fragrances and flavours. The rose owes some of its odour to a terpenoid furan, rosefuran, coffee some of its characteristics to furylmethanethiol and related compounds. Compounds like the 3-furanone derivative furaneol (10) are particularly interesting for their odours depend upon concentration— furaneol can seem to resemble pineapple, caramel, burnt toast etc. Furaneol is a dihydrofuran-3-one dihydrofuran-2-ones are obviously lactones and are usually dealt with as such. 

Although sulfite occupies most of the stage in terms of modifying the Maillard reaction, other sulfur compounds have an effect too for example, the use of N-acetylcysteine to reduce burnt off-flavours in canned liver sausage272 (see Chapter 5). 

C. Hilmes and A. Fischer, Role of amino acids and glucose in development of burnt off-flavours in liver sausage during heat processing, Meat Scl, 1997, 47, 249-258, via Food Sci. Technol. Abstr., 1998, 05S0817. 

OD-R (curry, spicy burnt, spicy flavour of stored citrus soft drinks non-fat dry milk aroma... 

Both 4-hydroxy-2,5-dimethyl-3(2H)furanone (HDMF trade name Furaneol Fig. 3.60) and 4-hydroxy-5-methyl-3(2H)-furanone (HMF Fig. 3.60) contribute to flavour at normal usage level they are, however, also enhancers of fruity and creamy odour impressions (see Tab. 3.46). Both furanones have caramel-like odours with HDMF possessing an additional burnt pineapple odour [1, 21]. The odour threshold of Furaneol has been reported to be 0.00004 ppm in water at 20°C [21 ]. 

Sulphur compounds furfuryl mercaptane with its very strong roasted coffee, sulphurous burnt character. This unstable component varies its flavour profile with the concentration. Methanethiol has a strong rotten, disgusting sulphurous odour, but at low concentrations it enhances an interesting, freshly brewed character to the coffee flavour. 

Pyrrol 2-acetyl pyrrol contributes a caramel, burnt, slightly chemical note to the flavour. 

Heat transforms ketoacids to methylketones like 2-heptanone, 2-nonanone with a green fatty metallic blue cheese note. Hydroxyy acids form the corresponding lactones. The creamy, buttery, coconut-like 5-decanolide, 4-dodecanolide, 5-dodecano-lide contribute to the sweet creamy buttery flavour in cream and butter. Lactose undergoes a caramelisation reaction to develop sweet, caramelic maltol and 4-hy-droxy-2,5-dimethyl-furan-3(2H)-one. Lactose and milk proteins react in a Maillard reaction to roasted, nutty, burnt notes such as 2,5-dimethyl pyrazine. 

At one time the main uses of sulphur were in the manufacture of gunpowder and of sulphuric acid. Nowadays its use for these purposes is more restricted. Sulphur is used in the manufacture of carbon disulphide, ultramarine, vermilion and numerous other compounds. Vulcanisation of rubber may be effected with sulphur. Enormous quantities are converted to bisulphites for treating wood pulp in the manufacture of paper. Sulphur is employed as a preventive of the growth of fungus on vines, and mould on hops it is burnt in the oast house to improve the flavour of the hops it is used as a disinfectant, a familiar form being sulphur candles . 

Maple and burnt sugar flavours, vanilla, butterscotch, licorice and rum compositions. 

An example of a furanone with methylated hydroxyl in position C-4 is 4-methoxy-2,5-dimethyl-2H-furan-3-one, also known as mesifurane, which is derived from furaneol. (-F)-(R)-Mesifurane (8-163) has a burnt and caramel-Hke odour, but is more subtle and mellow than the odour of furaneol. Mesifurane accompanies furaneol in fruits (such as pineapple, raspberry, strawberry and grape) and other foods. 2,5-Dimethyl-2H-fiiran-3-one, which does not contain the C-4 hydroxy group occurs as a constituent of bread and coffee flavour its odour resembles bread. 

Descriptive terminologies for the odours of pyridines use terms such as green, bitter, astringent, roasted, burnt, pungent, solvent and fishy, none of which could be considered desirable. Their presence in some food commodities, such as beer and whisky, is disagreeable and associated with a cardboard, oxidised and harsh flavour. In roasted coffee, pyridines may contribute to a pleasant smell that is, however, less pleasant than the smell of pyrazines. 

It is remarkable that the flavour characteristics of these oxidation products can not be related to the hoppy flavour. The mixtures all display a burnt odour. The occurrence of hydrocarbons in Cg is peculiar. Such compounds have also been detected in the... 

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