Acidic flavour

Ice lollies are made from juice (water, sugar, citric acid, flavour and colour) and are frozen into shape using moulds immersed in a cold brine solution, in a similar manner to can ice making (see Section 12.4). The moulds are made from stainless steel or nickel, and pass in rows through a brine bath at - 45°C. Different layers of confection may be built up by allowing one outside layer to freeze, sucking out the unfrozen centre and refilling with another mix. The sticks are inserted before the centre freezes solid. The moulds finally pass... 

A pickle is a food preserved in vinegar (ethanoic acid). Pickles generally have a sharp, acidic flavour in consequence of the acid preservative. Many systems - especially living cells - require their pH to be maintained over a very restricted range in order to prevent catastrophic damage to the cell. Enzymes and proteins denature, for example, if the pH deviates by more than a fraction. Traces of the food we eat are readily detected in the blood quite soon after eating, so why does the concentration in the blood remain constant, rather than dropping substantially with the additional acid in our diet ... 

Scheme 7.3 Enzymatic production of sulfur-containing flavour compounds in Allium species from amino acid flavour precursors, a S-Alk(en)yl cysteine sulfoxides and b (+)-S-l-propenyl cysteine sulfoxide (isoalliin) P-5 -Ppyridoxal-5 -phosphate...

Although there are a number of food colours suitable for use in soft drinks, it should be appreciated that the contribution of any one of these cannot be entirely predictable. In any soft drink formulation, the colour component, as with all other ingredients, has to be carefully selected for its performance in the presence of certain acids, flavourings, antioxidants and even preservatives. It is essential, therefore, at all stages of development that meaningful storage trials are completed to ascertain the real contribution from colour in the newly finished beverage. 

This compound exists as a vehicle to introduce the characterising components into the beverage thirst-quenching properties from the acid, flavour and body from the juice (also contributing to mouthfeel). A major part of the identity of the final drink is provided by the flavouring ingredients. In order to stabilise and protect these, oil- and water-soluble antioxidants are included. 

Calcium carbonate is not an acceptable texturiser in products where there is an acid component to the flavour - obviously, the calcium carbonate reacts with the acid to produce carbon dioxide. Typically, acids are only used in fruit-flavoured products, and here, talc must be used as a texturiser. If, by accident, calcium carbonate is used the carbon dioxide generated could blow up a sealed package causing the packaging to fail. The acid flavour is also lost through the acid-carbonate reaction. 

The chief adulterants are mineral acids, flavouring agents such as cayenne and ginger, and metals derived from the vessels used. 

The growth of microorganisms may have an important effect on the flavour of food. An example is the lactic acid bacteria Lactococcus lactis, which produce mainly lactate providing a characteristic acidic flavour and contributing to the preservation of fermented food. In an innovative approach, in situ 13C NMR was used to investigate glycolysis by an L. lactis strain deficient in lactate dehydrogenase.272... 

Other common environmental examples of quantitative GC are in the determination of pesticides in water, dioxin levels in soil and air pollutants. It is routinely used to examine levels of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). It is also a very important technique in the food industry, where it is used extensively for assay of fatty acids, flavours, sterols and residues such as insecticides, herbicides, preservatives, solvents and veterinary drugs. 

Sour flavours can be improved with acid flavours probably in addition with sweet flavourings. Also substances that suggest a sour taste by smell or colour (for example, lemon + yellow or raspberry -i- red) can be used. 

During fermentation of sour dough, different amounts of lactic acid, acetic acid, flavour precursors and volatile compounds are produced... 

Camu-camu (Myrciaria dubia Me. Vaugh) is a small reddish round berry with very acidic flavour that grows near Amazonian rivers and lakes. It is cultivated in Brazil and Peru and is one of the richest sources of vitamin C ever studied, with levels ranging from 1.4 to 6.1 g/100 g of ifeshpulp (Maedaeta/. 2006 Yuyamaeta/ 2002). Nevertheless,camu-camu consumption is not widespread in Brazil, but it is concentrated in... 

Formation of acetic acid, gluconic acid, and glucuronic acid Characteristic acidic flavour... 

MSG, C8H8NNa04,H20. Flavouring agent extensively used as a food additive. Prepared from natural or synthetic L-glutamic acid. 

CaH803. Fine white needles, m.p. 82°C, b.p. 285°C, strong vanilla odour, characteristic taste. It occurs extensively in nature, and is the odoriferous principle of the vanilla pod it can be obtained from the glucoside coniferin. Vanillin is made commercially from the ligno-sulphonic acid obtained as a by-product in the manufacture of wood pulp. It is one of the most important flavouring and perfuming... 

There are a number of different ways that the molecular graph can be conununicated between the computer and the end-user. One common representation is the connection table, of which there are various flavours, but most provide information about the atoms present in the molecule and their connectivity. The most basic connection tables simply indicate the atomic number of each atom and which atoms form each bond others may include information about the atom hybridisation state and the bond order. Hydrogens may be included or they may be imphed. In addition, information about the atomic coordinates (for the standard two-dimensional chemical drawing or for the three-dimensional conformation) can be included. The connection table for acetic acid in one of the most popular formats, the Molecular Design mol format [Dalby et al. 1992], is shown in Figure 12.3. 

V. Karl, J. Gutser, A. Dietrich, B. Maas and A. Mosandl, Stereoisomeric flavour compounds. EXVIII. 2-, 3- and 4-alkyl-branched acids. Part 2 chirospeciflc analysis and sensoT y evaluation , Chirality 6 427 - 434 (1994). 

The corrosive effects to be considered (mainly simple corrosion of metals) are, as would be expected from the edible nature of foodstuffs which are not excessively either acidic or basic but which may contain sulphur, less severe than those often encountered with inedible materials containing reactive substances. The importance of corrosive efiects where foodstuffs are concerned lies not so much in the action of the foodstuffs on the metal involved as in the resultant metal contamination of the foodstuff itself, which may give rise to off-flavours, in the acceleration of other undesirable changes (by the Maillard reaction for example), and in the possible formation of toxic metallic salts. Metal ions generally have threshold values of content for incipient taste effect in different liquid foodstuffs. Except in the case of the manufacture of fruit juices and pickles, process plant failure through corrosion must be rare. Nevertheless all foodstuffs, particularly liquid ones, should be regarded as potentially corrosive and capable of metal pick-up which may be undesirable. 

The important commercial feature of these juices, especially significant with blackcurrant and tomato juices, is their ascorbic acid (or vitamin C) content, of which loss by oxidation is known to be accelerated both by heat and by metal (particularly copper) contamination. The effect of copper has been carefully investigated for pure ascorbic acid", and more recently ascorbic acid in blackcurrant juice and model systems. There are, however, oxidation inhibitors of different kinds (which may themselves be heat-sensitive) present in various fruits, which give differing results. The presence of metals will also affect flavours", may cause discoloration, and may give rise to clouding effects, as in apple juice. ... 

Mention should also be made of glutamic acid and invert sugar which are used in foodstuffs and demand the use of hydrochloric acid-resistant material in manufacture, and of the essential flavouring oils which should preferably be stored and prepared in stainless steel and aluminium equipment. 

Polysubstituted 3-thiofiirans which are receiving a great interest as flavour and odour chemicals have been obtained by mono-//J5osubstitution and ortho-metallation from 3,4-dibromofuran <96T4065>. Dihydrofuran is used in a new synthesis of ketones from acids via acyl hemiacetals (Scheme 8, <96JOC6071>). 

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