Flavour Production

From its nature, a flavour is defined as a multicomponent blend of volatiles, non-volatiles and complex raw materials which is responsible for the final product properties. In flavour production, the volume-dominated operation units are mixing processes of liquids and dry blends. 

Under technical production aspects, the manufacturing of flavourings can be divided into  

Properties such as viscosity are very important for the production process. 

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In bakery products the pH of the product is important for several reasons. Acid foods are normally relatively safe microbiologically as a low pH inhibits the growth of bacteria. Fruit flavoured products such as fruit pie fillings normally have some acid component added to complement the fruit flavour. Where a hydrocolloid is present the pH of the product can be critical in terms of product stability or gelling. A hydrocolloid held at its isoelectric point, i.e. the pH at which there is no net charge, will likely come out of solution. 

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. 

Early fruit flavoured products were probably flavoured with jam and did not have a particularly strong flavour. Even with modern flavours the experiment of putting the wrong colour in the product will cause an appreciable proportion of tasters to misidentify the flavour. 

Genetic Engineering of Plants and Microbial Cells for Flavour Production. 615... 

About two thirds of the citrus produced worldwide is consumed as fresh fruit. Unfortunately, citrus utilised as fresh fruit cannot constitute a source of commercial flavours. However, in certain high-production countries such as the USA (Florida) and Brazil, the majority of the citrus crop is processed. In Florida over 90% of the orange crop is processed and is a major source for citrus flavouring material. Citrus fruits are processed primarily into juice, but oil from the outer layer of the peel, flavedo, and the condensate from making concentrated juice are also major sources of flavour products from citrus fruit. 

Ranjoanisafy X (1998) Purification et etude de quelques proprietes de la jS-glucosidase de la vanilla. Implications dans la preparation de la vanilla. Master s thesis, Ensia-Siarc, Montpellier Rao SR and Ravishankar GA (2000) Vanilla flavour Production by conventional and biotechnological routes. J Sci Food Agric 80 289-304... 

Liquid flavours can be divided into low-viscous liquids, medium-viscous liquids, emulsions, pastes and suspensions. The main processing of liquid flavour production is basically liquid blending. The most popular carriers for flavours for aqueous systems are ethanol, propylene glycol or glycerol. For fat-soluble flavours, triacetin or vegetable oils are the most important carriers. 

Table 23.1 Driving forces to use biotechnological methods for flavour production (adapted from [270]) ...

Table 23.2 summarises the main issues of microbial flavour production and how they may be addressed by biotechnological methods. 

Table 23.2 Main drawbacks during microbial flavour production and biotechnological strategies to address them... 

The flavour product from L-phenylalanine included 2-phenylethanol as the main product and 2-phenylethyl acetate as a side product, which is also a valuable rose-like flavour compound with a more fruity note and which is formed... 

Fig. 23.5 Aqueous-organic two-liquid-phase system for microbial production of flavour compounds. Here the formation of 2-phenylethanol from L-phenylalanine is exemplarily shown [120]. The organic solvent used for in situ extraction has to be carefully selected on the basis of multiple criteria, such as biocompatibility, non-flammability and legislative regulations. For a more detailed description of flavour production in two-phase systems, see Chap. 24 by Larroche et al.

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