Formation and Aroma Characteristics of Heterocyclic Compounds in Foods

Abstract

Heterocyclic compounds have been identified as important volatile components of many foods. The odor strength and complexity of these compounds makes them desirable as flavoring ingredients.Heterocyclic compounds are primarily formed through nonenzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the identification of pyrazines, pyridines, thiazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions.Our knowledge of the chemical composition of food flavors has made considerable progress during the last twenty years. This is mainly due to advances in analytical techniques, such as the coupling of GC with MS and the development of fused-silica capillary columns. Heterocyclic compounds occupy a prominent position among the more than 10,000 compounds occurring in the volatiles of foods. This results from their exceptional sensory properties (1). Heterocyclic compounds contain one or more heteroatoms (0, S and/or N) in rings or fused ring systems.The majority of heterocyclic compounds are formed through thermal interactions of reducing sugars and amino acids, known as the Maillard reaction.Other thermal reactions such as hydrolytic and pyrolytic degradation of food components (e.g. sugars, amino acids, vitamins) and the oxidation of lipids also contribute to the formation of heterocyclic compounds responsible for the complex flavor of many foodstuffs.Heterocyclic compounds may also be formed enzymatically in vegetables (tomatoes, bell peppers, aspara-1

Volatile components in flavour concentrates from crayfish processing waste

“…Twenty-six nitrogen-containing compounds, including 15 pyrazines and six pyridines, were identified. These heterocyclic compounds may be formed by Maillard and pyrolysis reactions during heating (Shibamoto and Bernhard 1976;Bailey and Einig 1989;Leahy and Reineccius 1989;Ho and Carlin 1989). The amounts of N-containing compounds were almost 2.3 times higher in the H concentrates than in the L concentrates ( Table 2).…”

“…The compound 2-thiophenecarboxaldehyde, having a raw green smell (Jayalekahmy and Narayanan 1989), was reported in roasted coffee (Vitzthum and Werkoff 1976) and white bread crust (Folkes and Gramshaw 1977). Thiazole has been reported to have a strong, nutty, popcorn-like odour, as well as a low threshold value in some foods (Ho and Carlin 1989;Shankaranarayana et a1 1989). The importance of the two thiazoles found in the crayfish flavour systems was not clear.…”

“…Kubota et aI (1980) reported that 33-dimethyl-1,2,4-trithiolane isomers ( Z -and E-forms) imparted onion-like odours in boiled Antarctic krills. These compounds can be produced by the reaction of aldehydes and hydrogen sulphide (Ho and Carlin 1989).…”

Comparison of Volatile Flavor Components in Four Kinds of Chinese Fermented Black Soybeans (Glycine max (L.) Merrill) by HS-SPME-GC/MS and Chemometrics

“…One ether named 1-Mmethoxy-4-(2-propenyl)-benzene (3.00%) was found in the 4 kinds of CFBS. 1-Methoxy-4-(2-propenyl)-benzene, also named anisole, was one important VFC in star aniseed (Guenther et al, 1977;Ho et al, 1989). Considering the desirable aromas of anisole, which mainly associate with anise-like aroma, this compound is considered to enhance spicy aroma.…”

Flavor Chemistry

“…While fat will make a flavor contribution due to primary degradation products (e.g., unsaturated aldehydes formed from chicken fat during heating), fat will also make a flavor contribution by participating in the browning reaction. Fat makes its contribution to browning flavors by yielding long chain aldehydes for participation in browning (Ho and Carlin 1989). There is no source of long chain aldehydes in foods except for the fatty acids.…”