Influence of sulfur amino acids on the volatile and nonvolatile components of cooked salmon (Salmo salar)

Volatile and nonvolatile compounds, which could contribute to flavor, were analyzed in salmon. One hundred twenty-three volatile compounds were identified in the headspace of two different samples of cooked salmon, including lipid-derived volatiles, Maillard-derived volatiles, sulfur volatiles, Strecker aldehydes, nitrogen heterocyclic compounds, terpenes, and trimethylamine. Significant differences between samples were found for 104 of the volatiles. Although the levels of free cysteine and methionine were low in the salmon, sulfur volatiles were formed in the cooked fish, demonstrating that there were sufficient sulfur amino acids present for their formation. Notable differences in sulfur compounds between the samples suggested that small changes in sulfur amino acids could be responsible. When this hypothesis was tested, salmon heated with cysteine had increased levels of many thiophenes, thiazoles, alicyclic sulfides, and nitrogen heterocycles. With the addition of methionine, levels of dimethyl sulfides, two alicyclic sulfides, pyrazines, some unsaturated aldehydes, and alcohols and 2-furanmethanethiol increased. The largest difference found among the nonvolatile (low molecular weight water-soluble) compounds was in inosine monophosphate.

Mechanisms of alkylpyrazine formation in a potato model system containing added glycine

The use of glycine to limit acrylamide formation during the heating of a potato model system was also found to alter the relative proportions of alkylpyrazines. The addition of glycine increased the quantities of several alkylpyrazines, and labeling studies using [2-C-13]glycine showed that those alkylpyrazines which increased in the presence of glycine had at least one C-13-labeled methyl substituent derived from glycine. The distribution of C-13 within the pyrazines suggested two pathways by which glycine, and other amino acids, participate in alkylpyrazine formation, and showed the relative contribution of each pathway. Alkylpyrazines that involve glycine in both formation pathways displayed the largest relative increases with glycine addition. The study provided an insight into the sensitivity of alkylpyrazine formation to the amino acid composition in a heated food and demonstrated the importance of those amino acids that are able to contribute an alkyl substituent. This may aid in estimating the impact of amino acid addition on pyrazine formation, when amino acids are added to foods for acrylamide mitigation.

Effect of citric acid and glycine addition on acrylamide and flavor in a potato model system

Acrylamide levels in cooked/processed food can be reduced by treatment with citric acid or glycine. In a potato model system cooked at 180 degrees C for 10-60 min, these treatments affected the volatile profiles. Strecker aldehydes and alkylpyrazines, key flavor compounds of cooked potato, were monitored. Citric acid limited the generation of volatiles, particularly the alkylpyrazines. Glycine increased the total volatile yield by promoting the formation of certain alkylpyrazines, namely, 2,3-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, tetramethylpyrazine, and 2,5-diethyl-3- methylpyrazine. However, the formation of other pyrazines and Strecker aldehydes was suppressed. It was proposed that the opposing effects of these treatments on total volatile yield may be used to best advantage by employing a combined treatment at lower concentrations, especially as both treatments were found to have an additive effect in reducing acrylamide. This would minimize the impact on flavor but still achieve the desired reduction in acrylamide levels.

Effects of plant sulfur nutrition on acrylamide and aroma compounds in cooked wheat

Wheat flour from plants deficient in sulfur has been shown to contain substantially higher levels of free amino acids, particularly asparagine and glutamine, than flour from wheat grown where sulfur nutrition was sufficient. Elevated levels of asparagine resulted in acrylamide levels up to 6 times higher in sulfur-deprived wheat flour, compared with sulfur-sufficient wheat flour, for three varieties of winter wheat. The volatile compounds from flour, heated at 180 degrees C for 20 min, have been compared for these three varieties of wheat grown with and without sulfur fertilizer. Approximately 50 compounds were quantified in the headspace extracts of the heated flour; over 30 compounds were affected by sulfur fertilization, and 15 compounds were affected by variety. Unsaturated aldehydes formed from aldol condensations, Strecker. aldehydes, alkylpyrazines, and low molecular weight alkylfurans were found at higher concentrations in the sulfur-deficient flour, whereas low molecular weight pyrroles and thiophenes and sugar breakdown products were found at higher concentrations in the sulfur-sufficient flour. The reasons for these differences and the relationship between acrylamide formation and aroma volatile formation are discussed.

Kinetic modeling of the generation of 2-and 3-methylbutanal in a heated extract of beef liver

Quantitative control of aroma generation during the Maillard reaction presents great scientific and industrial interest. Although there have been many studies conducted in simplified model systems, the results are difficult to apply to complex food systems, where the presence of other components can have a significant impact. In this work, an aqueous extract of defatted beef liver was chosen as a simplified food matrix for studying the kinetics of the Mallard reaction. Aliquots of the extract were heated under different time and temperature conditions and analyzed for sugars, amino acids, and methylbutanals, which are important Maillard-derived aroma compounds formed in cooked meat. Multiresponse kinetic modeling, based on a simplified mechanistic pathway, gave a good fit with the experimental data, but only when additional steps were introduced to take into account the interactions of glucose and glucose-derived intermediates with protein and other amino compounds. This emphasizes the significant role of the food matrix in controlling the Maillard reaction.

Humans ignore motion and stereo cues in favor of a fictional stable world

As we move through the world, our eyes acquire a sequence of images. The information from this sequence is sufficient to determine the structure of a three-dimensional scene, up to a scale factor determined by the distance that the eyes have moved [1, 2]. Previous evidence shows that the human visual system accounts for the distance the observer has walked [3,4] and the separation of the eyes [5-8] when judging the scale, shape, and distance of objects. However, in an immersive virtual-reality environment, observers failed to notice when a scene expanded or contracted, despite having consistent information about scale from both distance walked and binocular vision. This failure led to large errors in judging the size of objects. The pattern of errors cannot be explained by assuming a visual reconstruction of the scene with an incorrect estimate of interocular separation or distance walked. Instead, it is consistent with a Bayesian model of cue integration in which the efficacy of motion and disparity cues is greater at near viewing distances. Our results imply that observers are more willing to adjust their estimate of interocular separation or distance walked than to accept that the scene has changed in size.

The eMinerals project: developing the concept of the virtual organisation to support collaborative work on molecular-scale environmental simulations

The eMinerals project has established an integrated compute and data minigrid infrastructure together with a set of collaborative tools,. The infrastructure is designed to support molecular simulation scientists working together as a virtual organisation aiming to understand a number of strategic processes in environmental science. The eMinerals virtual organisation is now working towards applying this infrastructure to tackle a new generation of scientific problems. This paper describes the achievements of the eMinerals virtual organisation to date, and describes ongoing applications of the virtual organisation infrastructure.

ENABLE - a view on user's needs

The ENABLE project, which is partly funded by the European Commission, aims to assist elderly people to live well, independently and at case. In this project a wrist unit with both integrated and external sensors, and with a radio frequency link to a mobile phone. will be developed. ENABLE will provide a number of services for elderly people. among them also a remote control service for the home environment. This paper briefly describes the project in general and then focuses on the initial user needs investigation which was carried Out in early 2007 in six different European countries. The provisional findings are discussed and an outlook on the ongoing and future project work is given. A special focus of this paper is on the environmental control service.

The eMinerals Collaboratory: Tools and Experience

Collaboratories provide an environment where researchers at distant locations work together at tackling important scientific and industrial problems. In this paper we outline the tools and principles used to form the eMinerals collaboratory, and discuss the experience, from within, of working towards establishing the eMinerals project team as a functioning virtual organisation. Much of the emphasis of this paper is on experience with the IT tools. We introduce a new application sharing tool.

Biomimetic approach to Galbulimina type I alkaloids

On treatment with trifluoroacetic acid the tetraene precursor 23 underwent Boc deprotection, condensation and an iminium ion accelerated intramolecular Diels-Alder cycloaddition resulting in an iminium species 12, which was further converted into himbacine 1, himbeline 3 and himandravine 4, three out of four Galbulimina type I alkaloids thus providing strong evidence for the proposed biogenesis of this important family of alkaloids.