Reaction flavours

Milk solids are normally used as either milk powder or sweetened condensed milk in food manufacturing. Skim milk solids are an essential part of toffees as well as contributing useful colour and Maillard reaction flavours to baked goods. 

Reaction flavours Thermal treatment of amino acids and reducing carbohydrates based on Maillard reaction Caramel and malt flavours... 

The production of a closely related furanone starts with natural 5-oxo-glu-conic acid production from glucose with Gluconobacter suboxydans the acid is recovered by precipitation as the calcium salt for flavour applications, it is converted by heating to 4-hydroxy-5-methyl-2H-furan-3-one, a typical savoury reaction flavour with a meat-like taste [70] (Scheme 23.19). 

The preparation of reaction flavours is known to be improved by the presence of phosphate in the reaction mixture. The enhancing effect of phosphate on the rate of browning during the reaction of glycine with several hexoses has already been shown by Swimmer et al (11). 

J. Kerler, and C. Winkel, The basic chemistry and process conditions underpinning reaction flavour production, in Food Flavour Technology, A. J. Taylor (ed), Sheffield Academic Press, Sheffield, 2002, 27-59. 

As a result of acid-catalysed reactions during steam distillation, a number of terpenes and sesquiterpenes [66] of the native cold-pressed oils undergo transformation /9, 67-69]. This applies mainly to the pinenes, sabinene, thujene and some sesquiterpenes. While cold-pressed lime oils contain up to 2.3% of the reactive germacrenes, only traces of germacrene B can be found in distilled oils ]70]. When compared to their educts, the newly formed constiments, mainly alcohols, such as a-terpineol or fenchyl alcohol, possess completely different sensory properties. Additionally, cyclisations and hydratisations of aldehydes result in a reduced presence of these constituents in distilled products. Many compounds which characterise the flavour of distilled lime are formed during production. The extremely different composition of cold-pressed and distilled oils accounts for their completely different flavour profile and they, therefore, have to be considered as a reaction flavouring. 

The Middle Notes are based on reaction flavourings to impart specific complex roasted, meaty and smoky notes roasted chicken, boiled beef, smoked ham. They improve the overall taste with a general meaty background and a good mouthfeeling. Meaty middle notes are often based on the reaction of vitamin Bl, cystein and reducing sugars. Fat included in the reaction modifies the product into a specific animal direction chicken, beef, mutton, pork. 

The process to produce reaction flavourings is not just simple therefore the variability of the middle notes is also limited for economic reasons. 

The systematic use of gas chromatography coupled with olfactometry [27, 28] in the last 20 years has resulted in a number of new high-impact aroma chemicals found in natural extracts, food products and reaction flavours. In general, sulphur-containing odorants play a particularly important role in food products and savoury flavours [30]. Some of them are shown in Fig. 5.54. Usually, the odour threshold is one key attribute showing the potential impact of the odorant. This may be as low as 0.00002 pg/L water reported for bis-(2-methyl-3-furyl)disulphide (BMFD) (Fig. 5.55) found in cooked meat with a typical meaty, sulphury note. 

A wide range of flavouring substances is used in powdery or pasty convenience foods. Reaction flavours based on hydrolysed plant proteins, natural flavours, artificial flavours and meat, vegetable, yeast and spice extracts are added to the products to generate the desired flavour profile. The most common savoury flavour types used for dehydrated convenience foods are chicken, beef and vegetable flavours. However various other flavour types are used while formulating dehydrated convenience foods. Amongst them are mutton, crawfish, fish, wine and various spice and herb flavours. 

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. 

Like enzymes, whole cells are sometime immobilized by attachment to a surface or by entrapment within a carrier material. One motivation for this is similar to the motivation for using biomass recycle in a continuous process. The cells are grown under optimal conditions for cell growth but are used at conditions optimized for transformation of substrate. A great variety of reactor types have been proposed including packed beds, fluidized and spouted beds, and air-lift reactors. A semicommercial process for beer used an air-lift reactor to achieve reaction times of 1 day compared with 5-7 days for the normal batch process. Unfortunately, the beer suffered from a mismatched flavour profile that was attributed to mass transfer limitations. 

Problems Pear ester (43) is an important industrial flavouring compound with a pear-like taste and smell. Consider all possible Wittig disconnections and choose a reaction which should give the right geometrical isomer. 

Replacement of organic solvents by water may be done for environmental, cost e.g. reduction in raw materials and VOC containment costs) or technical reasons. In the flavour and fragrance industry, where the presence of even trace amounts of volatile impurities can be detected by the expert nose , significant process costs are entailed in ensuring complete removal of solvent. If reactions can be carried out in water then these additional costs can be saved. As an example geraniol can be isomerized to the important fragrance intermediates a-terpinol and linalol in water at 220 °C (Scheme 5.9). 

A book like the present one, which is not intended as a textbook for students, cannot be written by a single author. In fact, it is a multidisciplinary subject and the authors have not tried to omit all jargon and the flavour of the various disciplines involved. The consequence, of course, is that parts are not easy to understand for chemists, while others are difficult for chemical reaction engineers. It is hoped that this book will strongly contribute to bridging the gap between chemists and chemical engineers in the field. The authors will be grateful for comments from the readers. 

No attempt is made to provide comprehensive coverage of all the work carried out in these different media, but rather to give a flavour of the kind of systems for which the different approaches may be appropriate. In all the chapters, a more detailed discussion of the rhodium catalysed hydroformylation of 1-octene to nonanal, as a representative example of the synthesis of a long chain aldehyde with relatively low volatility, is provided [13, 14], This reaction has been chosen because ... 

Alternatively, hydrogen sulfide could be produced alongside ammonia and acetaldehyde by the breakdown of the mercaptoimino-enol intermediate of the decarboxylation reaction of the cysteine-dicarbonyl condensation product. Fisher also points out that hydrogen sulfide is forms many odiferous an hence intensely flavoured products.2 Cysteine is important as it is one of the major sources of sulfur. 

Anthocyanins usually give a purple red colour. Anthocyanins are water soluble and amphoteric. There are four major pH dependent forms, the most important being the red flavylium cation and the blue quinodial base. At pHs up to 3.8 commercial anthocyanin colours are ruby red as the pH becomes less acid the colour shifts to blue. The colour also becomes less intense and the anthocyanin becomes less stable. The usual recommendation is that anthocyanins should only be used where the pH of the product is below 4.2. As these colours would be considered for use in fruit flavoured confectionery this is not too much of a problem. Anthocyanins are sufficiently heat resistant that they do not have a problem in confectionery. Colour loss and browning would only be a problem if the product was held at elevated temperatures for a long while. Sulfur dioxide can bleach anthocyanins - the monomeric anthocyanins the most susceptible. Anthocyanins that are polymeric or condensed with other flavonoids are more resistant. The reaction with sulfur dioxide is reversible. 

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 ... 

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