Plants aroma chemicals from

Many important food aromas originate from biochemical pathways. These pathways comprise microbial reactions, endogenous and exogenous enzymatic action, and plant metabolism. In the past, flavour research concentrated on characterising the important chemicals in foods responsible for their specific aroma. Less information is therefore available on the biogeneration of flavours. At present, however, a renaissance of studies of natural flavours, including their biogeneration can be observed [1]. 

For a perfumer a rare and great challenge is to be confronted with a new material, one that has as yet no known history of perfumery use. It may be a newly synthesized aroma chemical or a material derived from a not commercially cultivated plant. 

Hatanaka shows in detail the reaction scheme in plants whereby linolenic acid is converted via lipoxygenase and lyase enzymes to cis-3-hexenal. This is subsequently converted by other enzyme systems to leaf aldehyde and leaf alcohol. These three aroma chemicals are important "green" aroma notes in strawberries and other berries. If these enzymes were commercially available, then the production of natural cis-3-hexenal from inexpensive vegetable oil is theoretically feasible. 

One category of aroma chemical is supplied by the petrochemical and coal industry. Termed synthetic ingredients, we deal in semantics. Since petrochemicals and coal are derived from long dead plant matter, they could equally be termed natural. Because man tweaks a spanner here and releases a pressure valve there, they are termed synthetic. If the difference is one of life force within the natural plant material, which is absent from the petrochemical route materials, then there is a case for the difference. But it is a moot point in the fragrance industry when either route achieves the desired aroma. The tie to the oil and coal industry though affects price stability and is a key concern to the industry when OPEC flexes its price-rise muscles. 

The rst commercial scent production was produced in the United Kingdom, in Mitcham, Surrey, in the seventeenth century, using lavender (Festing, 1989). In 1865, cinnamaldehyde, the rst synthetic, was made. Adulteration and substitution by the essential oil or component of another plant species became rampant. Aroma chemicals synthesized from coal, petroleum by products, and terpenes are much cheaper than the equivalent plant products, so perfumes became cheap. 

Aroma chemicals are an important group of organic molecules used as ingredients in flavor and fragrance composition. Aroma chemicals consist of natural, nature-identical, and artificial molecules. Natural products are obtained directly from the plant or animal sources by physical procedures. Nature-identical compounds are produced synthetically, but are chemically identical to their natural counterparts. Artificial flavor substances are compounds that have not yet been identified in plant or animal products for human consumption. 

Essential oils occur mainly in plants and are produced solely from the same source. The production of essential oils from animals such as musk, civet, and sperm whale has been banned to protect biodiversity. Essential oils and their constituents are indispensable raw materials for the flavor and fragrance industries. Essential oils are either used as such, or a pure aroma chemical or an oil fraction can be added to flavor or fragrance compositions. However, flavor and fragrance industries prefer to use their synthetic derivatives in compounding because of their lower cost. Essential oils also are used in food industries, especially in flavoring sauces and package food (13-21). 

As discussed, nature provided the source of inspiration for the synthesis of aroma chemicals. This remains as true today as it was in the nineteenth century. One of the reasons to explore the rain forests is biodiversity prospecting, which is the search for novel chemicals from biological sources. Rain forests are home not only to the majority of the world s flowering plants but to the majority of insects as well. This diversity of new flowers and pollinators increases the probability of discovering new aroma chemicals. 

Since early antiquity, spices and resins from animal and plant sources have been used extensively for perfumery and flavor purposes, and to a lesser extent for their observed or presumed preservative properties. Fragrance and flavor materials vary from highly complex mixtures to single chemicals. Their history began when people discovered that components characteristic of the aroma of natural products could be enriched by simple methods. Recipes for extraction with olive oil and for distillation have survived from pre-Christian times to this day. 

The market for flavours and aromas is large and was worth 16 billion in 2003 [7,8]. There are about 6,500 flavours known but of these only 300 are commonly used. At present 50-100 are produced by microbial fermentation, and many of the rest are chemically synthesised. In many cases, flavours and aromas are very complex mixtures extracted from pulp, bark, peel, leaf, bud, berry and flowers of fruit, vegetables, spices and other plants. The particular flavour or aroma will depend on the balance of these compounds, although a number are due to a single compound. 

It has long been known that honey differs not only in color, aroma, and flavor, but also in chemical, biological, and curative properties. The chemical composition of honey depends in a certain measure on the plants from which they are collected and even on the soil on which the plants grow ... 

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