Biomedical subjects

J M Ames

Publications and source records attributed to J M Ames.

22 records · Page 2Linked to original sources

PubMed1999

Effect of hexanal and iron on color development in a glucose/phenylalanine model system.

Aqueous glucose/phenylalanine (0.1 M with respect to each reactant) systems were heated in an autoclave for 30 min at 140 degrees C, in the presence of hexanal (0.04, 0.1, and 0.2 M) or FeCl(2) (0.01 M). Results show that hexanal significantly inhibited color development at pH 5 and 6 and led to an increase of 5-(hydroxymethyl)furfural. Iron addition had similar effects at pH 5, but only small effects at pH 6. The reaction routes proposed give key roles to the alpha-dicarbonyl compounds, to the Strecker aldehyde, and to the Schiff base formed by the reaction between hexanal and phenylalanine.

Aldehydes↗

PubMed1999

Volatile compounds from potato-like model systems.

The volatile reaction products of aqueous mixtures comprising combinations of methionine, glucose, linoleic acid, and starch heated in a modified Likens-Nickerson apparatus were extracted and analyzed by gas chromatography-mass spectrometry (GC-MS). The majority of volatile compounds were formed from linoleic acid degradation, hexanal, 2,4-decadienal, and 2-pentylfuran being identified in the greatest amounts. Dimethyl disulfide and dimethyl trisulfide were detected in every system containing methionine. 3-(Methylthio)propanal (methional) and other sulfur compounds were detected when methionine was heated with another precursor. No binding of volatile compounds to starch was observed; rather, starch appeared to act as an additional source of reactive carbohydrate. Almost all the components identified have been identified among the aroma components of cooked potato. No pyrazines, pyridines, or thiazoles were identified, probably due to the relatively low temperature/high moisture conditions.

Cooking↗

PubMed1999

Effect of high hydrostatic pressure on the volatile components of a glucose-lysine model system.

An aqueous glucose-lysine model system (initial pH 10.1) was incubated at 60 degrees C and atmospheric pressure (system A) or 600 MPa (system B) to the same absorbance value at 420 nm. Volatile reaction products were isolated by solvent extraction and analyzed by gas chromatography/mass spectrometry. Thirty-two compounds were identified; most contained nitrogen, and pyrazines predominated. Yields of all compounds were suppressed at 600 MPa. Further incubation, at either atmospheric pressure (system C) or 600 MPa (system D), of system A, resulted in lower yields of many compounds at 600 MPa, compared to prolonged incubation at atmospheric pressure. Many of the compounds reported may be formed by, or subsequently react via, aldol condensation. The observed differences among the systems in the profiles and yields of volatile compounds suggest that aldol condensations increase in rate in the systems under pressure.

Furans↗

PubMed1999

The effect of a model melanoidin mixture on faecal bacterial populations in vitro.

The Maillard reaction produces coloured, macromolecular materials (melanoidins) in a variety of foods, on heating. Significant quantities may enter the human gut on a daily basis, but there is little information on their metabolism in the human colon. As the large bowel contains a diverse population of bacteria involved in normal bowel function, it is possible that melanoidins are metabolized therein. Depending on the bacteria involved, there may be disease or health implications. The aim of the present study was to use in vitro models to determine the digestibility of melanoidins and the effect of melanoidins on colonic bacteria in the gastrointestinal tract. Melanoidins were prepared and the effects of simulated upper-gut secretions on their stability determined in a model system. The effects of faecal bacteria were also determined, in batch culture, with a combination of phenotypic and genotypic (probes) criteria being used to identify the microbial diversity involved. Simulation of peptic and pancreatic digestion showed that the melanoidins did not produce detectable amounts of low-molecular-mass degradation products. However, melanoidins affected the growth of gut bacteria during mixed culture growth. The effect was to cause a non-specific increase in the anaerobic bacteria enumerated. This in vitro study indicates that melanoidins can affect the growth of human large-bowel bacteria and serves to demonstrate possible effects that may occur in vivo. Given the large and varied number of food items that contain Maillard reaction products, this may have relevance for lower-gut health.

Adult↗