Active flavours

Stereoselectivity of lipases is often used to yield pure optically active flavour compounds from racemic precursors. This fact is important if one isomer of a molecule has more desirable properties than the other one. 

Cumin oil is usually obtained by steam distillation of the milled spice hydrodiffusion gives a higher yield and, more recently, supercritical gaseous extraction is claimed to give oil closer to the aroma and taste of the spice (Eikani et al., 1999). The yields of cumin seed oil with steam distillation are 2.3-3.6%, with liquid carbon dioxide it is 4.5% and with ethanol it is 12%. The major components are cuminaldehyde, cuminyl alcohol, p-mentha and 1.3-dien-7-al, the minimum perceptible levels being at 0.2 ppm. Naik et al. (1989) reported that liquid C02 extraction was quicker than steam distillation for the quantitative extraction of cumin oil without loss of active flavour components, at 58 bar and 20°C. 

GRIFFIN, S.G., WYLLIE, S.G., MARKHAM, J.L., LEACH, D.N., The role of structure and molecular properties of terpenoids in determining their antimicrobial activity, Flavour and Frangrance J., 1999,14,322-332. 

Spray drying is recognised as an efficient method of converting liquid flavours into powders. By spray drying it is possible to produce a powder with controlled physical properties such as flowability, residual moisture content and bulk density. At the same time it is possible to control the properties of the active flavour component in terms of its controlled release, its organoleptic quality etc. 

Griffin SG, Wyllie SG, Markham JL, Leach DN (1999) The role of stmcture and molecular properties of terpenoids in determining their emtimicrobial activity. Flavour Fiagr J 14 322-332... 

Naik et al. [16] reported the quantitative extraction of cumin oil in a faster time than steam distillation, without loss of active flavour components. They showed that at 58 bar and 20°C, L.CO2 yielded 4.5% in 2 hours compared to the steam distillation of the same spice giving 2.5% in 4 hours. Assuming the distillation exhausted the spice, it must be presumed that the extra yield was only lipids (reviewer s comment). 

Strategy Problem 7 Synthesis of a single enantiomer. Many compounds such as pharmaceuticals, flavourings, and insect control chemicals must not only have the right relative stereochemistry but must be optically active too if tliey are to be of any use. Consider the strategy of synthesising one enantiomer ... 

Phytochemicals are biologically-active, non-nutritive secondary metabolites which provide plants with colour, flavour and natural toxicity to pests. The classification of this huge range of compounds is still a matter of debate, but they fall into three main groups ... 

The discovery that, in industrialised societies, diets deficient in fruits and vegetables can effectively double the risk of developing many different types of cancer has focused renewed attention on the beneficial properties of these foods (Block e/a/., 1992 Patterson ef a/., 1990 Southon and Faulks, 2002). As we have seen, plant foods are rich in micronutrients, but they also contain an immense variety of biologically active secondary metabolites providing colour, flavour and natural toxicity to pests and sometimes humans (Johnson et ah, 1994). The chemistry and classification of such substances is still a matter for much research and debate, but this has not prevented attempts to isolate and exploit substances that have variously been termed protective factors , phytoprotectants , phytochemicals and nutraceuticals . Phytochemical compounds include ... 

A huge variety of biologically active phenolic compounds containing one or more aromatic rings are found naturally in plant foods, where they provide much of the flavour, colour and texture. The simpler phenolic substances include ... 

Similarly, low volume chemicals are classified according to whether they are sold primarily on the basis of specification or performance. Specialties are generally formulations that are sold on the basis of their performance and their prices reflect their value rather than cost of production. Producers of specialty chemicals often provide extensive technical service to their customers. Examples of specialty chemicals include pharmaceuticals, pesticides, flavours and fragrances, specialty polymers, etc. Fine chemicals, on the other hand, are produced to customer specifications and are often intermediates or active ingredients for specialty chemicals, e.g. pharmaceutical and agrochemical intermediates and bulk actives. 

In the case of chiral molecules that are biologically active the desired activity almost always resides in only one of the enantiomers. The other enantiomer constitutes isomeric ballast that does not contribute towards the desired activity and may even exhibit unwanted side effects. Hence, there is a marked trend in pharmaceuticals, agrochemicals and flavours and fragrances towards the marketing of products as enantiomerically pure compounds. This, in turn, has generated a demand for economical methods for the synthesis of pure enantiomers (Sheldon, 1993a). 

Structure/Activity Comparison in the Ability of Some Terpenoid Food Flavours to Cause Peroxisome Proliferation. Literature References, Georges-Louis Friedli, September 1992, University of Surrey, School of Biological Sciences, http //friedli.com/research/MSc/literature.html... 

The restricted shelf life of liquid milk continues to be a problem that is often more influenced by the type of milk being sold rather than the pasteurisation technique. The shelf life of processed milk is determined primarily by the quality of the raw milk from the dairy herd. Increasing cell counts in the milk and a higher concentration of free fatty acids, contribute to rancidity in both liquid milk and milk products. Janzen (1972) reported that the 0-14 day shelf life of pasteurised milk is influenced by the somatic cell concentration in the raw milk and found that after 14 days any observed changes in the flavour and stability of the milk were attributable to microbial activity during storage. 

Traditionally, butter was made by allowing cream to separate from the milk by standing the milk in shallow pans. The cream is then churned to produce a water in oil emulsion. Typically butter contains 15% of water. Butter is normally made either sweet cream or lactic, also known as cultured, and with or without added salt. Lactic butter is made by adding a culture, usually a mixture of Streptococcus cremoris, S. diacetylactis and Betacoccus cremoris. The culture produces lactic acid as well as various flavouring compounds, e.g. diacetyl, which is commonly present at around 3 ppm. As well as any flavour effect the lactic acid inhibits any undesirable microbiological activity in the aqueous phase of the butter. Sweet cream butter has no such culture added but 1.5 to 3% of salt is normally added. This inhibits microbiological problems by reducing the water activity of the aqueous phase. It is perfectly possible to make salted lactic butter or unsalted sweet cream butter if required. In the UK most butter is sweet cream while in continental Europe most butter is lactic. 

There is a practice of making holes in this sort of cake and pouring in spirits such as whisky, brandy or rum. While this may be done to enhance the flavour it will almost certainly improve the keeping properties. The alcoholic mixture will not only reduce the water activity as ethanol has considerable mould inhibitory and antibacterial properties. 

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