This article provides current information on the production of volatile compounds from interactions of Maillard reactions and lipids. It includes a brief introduction outlining the Maillard reactions, the Strecker degradation of amino acids, and the oxidation of lipids. It highlights those compounds derived from these reactions that could interact to form volatile flavor components during the processing or cooking of food. The article discusses results obtained from model systems involving interactions between (1) Maillard reaction products and carbonyl compounds, (2) amino acids and carbonyl compounds, (3) amino acids and derivatives of fatty acids, and (4) Maillard reaction products, triglycerides and phospholipids. The qualitative and quantitative effects that triglycerides and phospholipids have on the formation of volatile Maillard products are also discussed. Particular attention is given to those long-chain alkyl heterocyclic compounds formed during these reactions, proposed methods for their formation, and their aromas. The role that such compounds play in food flavors is discussed with reference to those volatile compounds identified in certain cooked foods, such as meat (beef, lamb, and pork), chicken, potatoes (baked, French-fried, and crisps), and beverages (coffee, tea, and cocoa).

A survey has been made of the occurrence and relative amounts of 3-isopropyl-, 3-sec-butyl-and 3-isobutyl-2-methoxypyrazines in a broad selection of raw vegetables. At least one of these compounds was detected in all but four and all three were identified in 13 of the 27 vegetable tissues examined. The technique is described for their separation, identification and estimation. This involved headspace collection of total volatiles on porous polymer traps, separation by trapping and transfer between capillary columns and mass spectral identification. A general synthesis of 3-substituted-2-methoxypyrazines giving high yields and single end products is described. A possible biogenesis of the named compounds is discussed.

Forty-nine species (87 samples) of marine macroalgae from eastern Australia were analyzed by GC/MS for the key seafood flavor components 2- and 4-bromophenol, 2,4- and 2,6-dibromophenol, and 2,4, 6-tribromophenol. All five bromophenols were found in 62% of samples, four in 32% of samples, and three in the remaining 6% of samples. 2, 4,6-Tribromophenol was found in all samples and, with few exceptions, was present in the highest concentrations. The total bromophenol content determined on a wet-weight basis varied widely across species from 0.9 ng/g in the green alga Codium fragile to 2590 ng/g in the red alga Pterocladiella capillacea. Species with the highest concentrations of bromophenols were all collected from sites exposed at low tide. The study demonstrates the wide occurrence of bromophenols in marine algae and provides a possible source of such compounds in fish that feed predominantly on ocean plants. The possible effect that dietary marine algae has on the flavor of omnivorous ocean fish is discussed.

Thirty samples of 9 species of prawns (shrimp) harvested from sites along the eastern coast of Australia and 10 samples of two cultivated species were analyzed by GC/MS for the key flavor components, 2- and 4-bromophenol, 2,4- and 2,6-dibromophenol, and 2,4,6-tribromophenol. In the commercially important wild-harvested species, Penaeus plebejus, P. esculentus, and P. latisulcatus, the total bromophenol content was found to vary between 9.5 and 1114 ng/g, while in the major cultivated species, P. monodon, the total bromophenol content was <1 ng/g. Sensory analyses of 10 samples of wild-harvested prawns showed that the meat of these animals had briny, ocean-like, and prawn-like flavors, whereas all five samples of cultivated prawns were described as bland. Furthermore, analysis by GC/MS of the heads (including the gut) and tails of these animals showed that in wild-harvested prawns the average total bromophenol content in the heads was 6.8 times greater than that in the tails; in cultivated animals it was only 3 times greater. These observations support the opinion that bromophenols are derived from components of the diets of these animals. The paper discusses the likely dietary sources of these compounds in Australian prawns and a possible controlled dietary procedure to improve the flavor of cultivated animals. Keywords: Prawns; bromophenols; GC/MS analysis; flavor; sensory analysis; dietary origins

Volatile extracts of moderately off-flavoured frozen peas, prepared by vacuum sublimation followed by concentration of the sublimate by low temperature vacuum distillation, were examined by gas chromatography, silica gel chromatography and combined gas chromatography-mass spectrometry. The constituents identified included alcohols (29), carbonyls (31), esters (12), hydrocarbons (19), terpenes (6) and 3-alkyl-2-methoxypyrazines (3). Olfactory monitoring of the gas chromatographic column effluent indicated that most of the strong odours were associated with alkanals, alk-2-enals, alka-2,4-and 2,6-dienals, octa-3,5-dien-2-ones, 3-alkyl-2-methoxypyrazines and hexanol. However, no compound which, by itself, could account for the "hay-like" off-flavour of peas was evident. The ofF-flavour is considered to be complex and composed largely of the more odorous unsaturated carbonyls derived from the enzymic breakdown of the unsaturated pea lipids. The volatiles of pea shells similarly examined were found to contain many of the compounds present in peas.