Naturally occurring flavor compounds

Many compounds found in nature contain an aldehyde or ketone functional group. Vanilla and cinnamon flavorings are naturally occurring aldehydes. Two isomers of the ketone carvone impart the characteristic flavors of spearmint leaves and caraway seeds. 

Perfumes, Flavors, Cosmetics, and Soap. Many naturally occurring esters in essential oils and some synthetic esters are important fragrance and flavor compounds (61,62). They are used in perfumes, flavors, cosmetics, soaps, detergents, and air fresheners. Benzyl, butyl, ethyl, methyl, and phenyl esters of benzoic acid are used as flavors, perfumes, and food preservatives. Glyceryl 4-aminobenzoate [136-44-7] and 2-ethyUiexyl 4-dimethylaminobenzoate [21245-02-3] are used in cosmetic sunscreen preparations. Alkyl esters of 4-hydroxybenzoic acid, called parabens, have been used under various names for fungus infections of the skin, and as preservatives in lotions and creams (101). Soap and cosmetic fragrances use large amounts of amyl and benzyl saHcylate. Benzyl saHcylate [118-58-1] is also used in deodorant sprays. 2-Ethylhexyl saHcylate [118-60-5] and 2-ethylhexyl 4-methoxycinnamate [5466-77-3] are used in sunscreen formulations (102). 

Humans may be programmed to be more sensitive to natural food contaminants. For instance, (-)geosmin (rrans-l,10-dimethyl-rran5-9-decalol) occurs in earth, natural surface water, and in foods in contact with soil or water, such as beets, clams, or fish. Geosmin is a microbial, fungal, or algal metabolite. It is a water pollutant and off-flavor compound. The naturally occurring (-)enantiomer has a threshold 11 times lower than the (-I-) enantiomer (Polak and Provasi, 1992). 

In most European countries, flavors that occur naturally or are generated during healing or processing by enzymatic reactions or modification generally arc considered natural flavors. Flavors that arc often referred to in the United Stales as synthetic are usually termed "artificial" in Europe. These would include such compounds as ethyl vanillin, allyl-of-iononc, and ethyl maltol. However, substances that are synthesized but chemically identical to the naturally occurring substances arc classified as "natural-identical." This class would include diacetyl, benzaldehyde, antsyl acetate, and benzophenone. 

In summary, model studies are very efficient for the identification and structure elucidation of important flavor components. Most of the compounds reported here have not been identified in meat and have not yet been reported as constituents of food volatiles. Nevertheless, there are good reasons to believe that minute traces of these sulfur-containing components are present in roasted and/or cooked meat volatiles because our model system was based solely on naturally occurring precursors. We believe that only minute trace amounts of these types of components need to be present in natural products to be of prime significance due to their extremely low odor threshold values. 

Potato taste is not characterized by one of the primary taste sensations. Especially sweet, sour or bitter notes are considered off-flavors. However, free amino acids and 5 -nucleotides are important compounds that convey an agreeable basic taste to potato products. The amino acids occur naturally in free form the 5 -nucleotides are liberated during the heat preparation of potatoes by a specific enzymatic degradation of RNA. Starch forms a matrix for all potato preparations. Although it is tasteless, is has an influence on taste quality due to textural characteristics, and due to its pronounced capability to form stable complexes with flavor compounds either in a thermal gradient or under isothermal conditions. 

This chapter discusses some of the more important natural products terpenes, steroids, alkaloids, fats, and prostaglandins. (Fats are primary natural products, but it is convenient to include them in this chapter.) The structures and various aspects of their biosynthesis and chemical reactions are presented in subsequent sections. Because entire books have been written on each of these groups of compounds, the coverage here is necessarily incomplete. However, the intent is to present some of the flavor of their chemistry. Many other classes of naturally occurring organic compounds are not included for reasons of space. 

Carbonyl compounds are everywhere. In addition to their uses as reagents and solvents, they are constituents of fabrics, flavorings, plastics, and drugs. Naturally occurring carbonyl compounds include proteins, carbohydrates, and nucleic acids that make up all plants and animals. In the next few chapters, we will discuss the properties and reactions of simple carbonyl compounds. Then, in Chapters 23 and 24, we apply this carbonyl chemistry to carbohydrates, nucleic acids, and proteins. 

To produce an edible fat (an oil having the desired color, flavor and oxidative stability, and functional properties), naturally occurring and undesired compounds must be removed as efficiently as possible, with maximally preventing damage to the naturally occurring antioxidants and neutral oil fraction. Formation of new compounds, precipitated processing adjuncts, and contaminants are all undesirable. 

Our food supply contains naturally occurring chemicals and frequently synthetic chemical compounds ( 1 5). There is no chemical distinction between a flavor compound synthesized by nature and the same compound prepared in the laboratory. Yet the perception that anything natural is "good for you and that which is synthetic is harmful, is prevalent among consumers. 

The number of synthetically produced fragrance and flavor chemicals has since expanded continually as a result of the systematic investigation of essential oils and fragrance complexes for odoriferous compounds. Initially, only major components were isolated from natural products their structure was then elucidated and processes were developed for their isolation or synthesis. With the development of modem analytical techniques, however, it became possible to isolate and identify characteristic fragrance and flavor substances that occur in the natural products in only trace amounts. The isolation and structure elucidation of these components re-... 

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