Frank B. Whitfield

Volatiles from interactions of Maillard reactions and lipids.

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).

Phthalate and adipate esters in Australian packaging materials

A total of 136 food packaging materials were analysed for the presence of six phthalate esters and one adipate ester. All of the sample materials were manufactured from either synthetic polymers or from wood pulp and most were in immediate contact with their food contents. The esters in the packaging materials were extracted into a 2:1 mixture of chloroform and methanol, and analysed by gas chromatography-mass spectrometry. All of the materials examined were found to contain two or more of these compounds above a detection limit of 0.01 μg/kg. Total phthalate concentrations ranged from 5 to 8160 μg/g and adipate concentrations ranged from not detected to 1728 μg/g. In general, materials with the most surface coverage of printing inks had the greatest concentrations of phthalates. Variations were noticed in the occurrence and concentrations of phthalate and adipate esters in the packaging materials over a 12 month period during 1996 and 1997.

4-Hydroxybenzoic acid : a likely precursor of 2,4,6-tribromophenol in Ulva lactuca

Abstract The green marine alga Ulva lactuca is known to contain simple bromophenols, especially 2,4,6-tribromophenol, but the precursor of these compounds in the alga is not known. With the aim of identifying potential precursors, the alga was analyzed for the presence of phenolic compounds. The compounds identified by gas chromatography–mass spectrometry were phenol, 4-hydroxybenzoic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenyllactic acid, 4-hydroxybenzaldehyde, 3,5-dibromo-4-hydroxybenzoic acid and 2,4,6-tribromophenol. Free l -tyrosine and free l -phenylalanine were also present in the alga. Furthermore, a crude enzyme extract from the alga, which contained bromoperoxidases, was used to brominate a range of phenolic compounds and the formation of bromophenols was monitored. The compounds forming 2,4,6-tribromophenol were phenol, 4-hydroxybenzoic acid, 4-hydroxyphenylacetic acid, 4-hydroxybenzyl alcohol and 2-hydroxybenzyl alcohol. 4-Hydroxybenzoic acid is designated as the most likely precursor of 2,4,6-tribromophenol in U. lactuca and a pathway for its formation from l -tyrosine, via 4-hydroxyphenylpyruvic acid, is proposed.

The role of fungi in the production of chloroanisoles in general purpose freight containers

Abstract Samples of timber from the flooring of six general-purpose freight containers allegedly involved in the contamination of foodstuffs by 2,4,6-trichloroanisole were analysed for chlorophenol, chloroanisole and fungal content. All containers were found to be contaminated with 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol and in all but one container their corresponding chloroanisoles. The concentrations of these compounds varied over a range of five orders of magnitude. In addition, 38 species of fungi were isolated from the timber. The species identified consisted of a variety of Alternaria (1), Aspergillus (7), Cladosporium (2), Eurotium (4), Mucor (1), Paecilomyces (1), Penicillium (16), Phoma (1), Trichoderma (4) and Ulocladium spp. No one species was found in all containers; however, Penicillium chrysogenum was isolated from five containers and six other species, Eurotium amstelodami , E. repens, E. rubrum, Penicillium corylophilum, P. aurantiogriseum and Ulocladium sp. were each found in three containers. Of the 38 species isolated, 19 are known to biomethylate chlorophenols in wood and pulped wood products. At least three species of fungi with this ability were found in each container. An attempt has been made to relate the presence of individual fungi in a container to the observed concentrations of the chloroanisoles.

Biosynthesis of bromophenols in marine algae

The green marine alga Ulva lactuca is known to contain high concentrations of bromophenols. However, the biosynthetic pathways of their formation is not known. This study was aimed at identifying possible precursors of bromophenols. The bromophenol content and bromoperoxidase activity were measured in the alga collected every month from January to August 1997. Bromoperoxidases were extracted and incubated with various possible precursors of bromophenols and brominated reaction products were identified by gas chromatography-mass spectrometry. The results show that U. lactuca contains a bromoperoxidase which can convert phenol, 4-hydroxybenzoic acid and 4-hydroxybenzyl alcohol to bromophenols. L-tyrosine and 4-hydroxybenzaldehyde could not be converted to bromophenols. Bromophenol content and bromoperoxidase activity exhibited a seasonal variation with high productivity in summer and low in winter.

Brominated anisoles and cresols in the red alga Polysiphonia sphaerocarpa

The red marine alga Polysiphonia sphaerocarpa was extracted by a simultaneous steam distillation-solvent extraction technique and several brominated compounds were identified by gas chromatography-mass spectrometry. The compounds detected were 2,4-dibromoanisole, 2,4,6-tribromoanisole, 3-bromocresol, 3,5-dibromocresol, 3-bromo-4-hydroxybenzaldehyde, 3,5-dibromo-4-hydroxybenzaldehyde, 2-bromophenol, 4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol and 2,4,6-tribromophenol. This is the first time brominated anisoles and cresols have been detected in marine algae.

Seasonal variation in bromophenol content andbromoperoxidase activity in Ulva lactuca

Seasonal variation in bromophenol content and bromoperoxidase activity in the greenmarine alga, Ulva lactuca, was studied. Bromophenols were extracted from the alga bysimultaneous steam distillation-solvent extraction, followed by identification and quantificationby gas chromatography–mass spectrometry. A method for the extraction of bromoperoxidasesfrom the alga was developed, which includes homogenisation in Milli-Q water and addition ofglycerol. The results obtained show that both bromophenol content and bromoperoxidase activityexhibit extreme seasonal variation, with high values in summer and low ones in winter.

Role of Yersinia intermedia and Pseudomonas putida in the development of a fruity off-flavour in pasteurized milk.

Analysis by gas chromatography-mass spectrometry of pasteurized milk with a fruity (pineapple like) off odour and a sour, rancid and soapy taste indicated the presence of concentrations at microg/ml levels of ethyl butanoate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, octanoic acid, decanoic acid and dodecanoic acid. The off-odour and taste were attributed to the presence of these compounds in the milk. Microbiological examination confirmed that the milk was also contaminated with a series of psychrotrophic bacteria including Yersinia intermedia, Pseudomonas putida and Rahnella aquatilis. Growth of isolates of these bacteria in UHT milk at 23 degrees C for 7 d showed that Yer. intermedia produced significant quantities of the C4-C12 alkanoic acids; Ps. putida produced only small quantities of these acids and Rah. aquatilis produced none. In addition, Yer. intermedia and Ps. putida also produced small but significant quantities of the corresponding ethyl esters. In milk inoculated with both Yer. intermedia and Ps. patida, the quantity of ethyl esters produced was greater than that found in cultures containing only one of the isolates. These studies indicated that Yer. intermedia was the principal source of the alkanoic acids in the tainted milk and that the major producer of the corresponding ethyl esters was Ps. patida. This is the first report that Yer. intermedia and Ps. putida can cause an off-odour or taste in dairy products.

Role of feed ingredients in the bromophenol content of cultured prawns

Commercial and experimental pelleted feeds were fed to prawns (Penaeus monodon) in aquaculture ponds and laboratory tanks to assess the effect of different ingredients on the bromophenol content of cultivated animals. Ingredients with bromophenols typically used in commercial feeds were fish, shrimp head, krill and squid meals and those additionally used in experimental feeds were dried marine algae, dried polychaetes, free bromophenols and bromophenol sulphate esters. After harvest, prawns and feed were analysed by GC/MS for 2- and 4- bromophenol, 2,4- and 2,6-dibromophenol and 2,4,6-tribromophenol. The total bromophenol content of commercial feeds ranged from 1.4 to 153 ng/g and those of experimental feeds from 2.9 ng to 18.9 μg/g. Retention of bromophenols by prawns was low for all ingredients; prawns fed commercial feeds ranged from 0.3 to 9.7 ng/g and those fed experimental feeds ranged from trace to 22.2 ng/g. Sensory analysis showed that the flavour of most prawns was bland and lacked the characteristic ocean flavour of wild crustaceans. Possible reasons for the low retention of bromophenols in prawns fed pelleted feeds are discussed.

Extraction of volatile compounds from green peas (Pisum sativum).

The volatile fractions extracted from unblanched changes in the volatile fraction during extraction. green peas by three distillation techniques and by Vacuum sublimation, conducted under conditions vacuum sublimation were of similar qualitative but which provide maximum practical protection against markedly different quantitative composition. With enzymic, microbial, and thermal changes, is recomblanched peas the extracts provided by all the mended as a reference method for assessing the methods examined were identical. The use of authenticity of extracts derived by distillation distillation methods to extract biologically active methods. materials involves a serious risk of compositional