Forty-four odor-active compounds were quantified in Scheurebe and Gewurztraminer wines, respectively. Calculation of odor activity values (OAVs) of odorants showed that differences in odor profiles...

Quantitation and Sensory Studies of Character Impact Odorants of Different White Wine Varieties

Flavour development in dairy fermentations, most notably cheeses, results from a series of (bio)chemical processes in which the starter cultures provide the enzymes. Particularly the enzymatic degradation of proteins (caseins) leads to the formation of key-flavour components, which contribute to the sensory perception of dairy products. More specifically, caseins are degraded into peptides and amino acids and the latter are major precursors for volatile aroma compounds. In particular, the conversion of methionine, the aromatic and the branched-chain amino acids are crucial. A lot of research has focused on the degradation of caseins into peptides and free amino acids, and more recently, enzymes involved in the conversion of amino acids were identified. Most data are generated on Lactococcus lactis, which is the predominant organism in starter cultures used for cheese-making, but also Lactobacillus, Streptococcus, Propionibacterium and species used for surface ripening of cheeses are characterised in their flavour-forming capacity. In this paper, various enzymes and pathways involved in flavour formation will be highlighted and the impact of these findings for the development of industrial starter cultures will be discussed.

Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese products

Protein/polysaccharide complexes and coacervates in food systems

Cheese flavour formation by amino acid catabolism

Foods make up some of the most complex examples of soft condensed matter (SCM) with which we interact daily. Their complexity arises from several factors: the intricacy of components, the different aggregation states in which foods are encountered, and the multitude of relevant characteristic time and length scales. Because foodstuffs are governed by the rules of SCM physics but with all the complications related to real systems, the experimental and theoretical approaches of SCM physics have deepened our comprehension of their nature and behaviour, but many questions remain. In this review we discuss the current understanding of food science, by considering established SCM methods as well as emerging techniques and theoretical approaches. With their complexity, heterogeneity and multitude of states, foods provide SCM physics with a challenge of remarkable importance.

Understanding foods as soft materials

Solid-phase microextraction (SPME) fibers were evaluated for their ability to adsorb volatile flavor compounds under various conditions with coffee and aqueous flavored solutions. Experiments comparing different fibers showed that poly(dimethylsiloxane)/divinylbenzene had the highest overall sensitivity. Carboxen/poly(dimethylsiloxane) was the most sensitive to small molecules and acids. As the concentrations of compounds increased, the quantitative linear range was exceeded as shown by competition effects with 2-isobutyl-3-methoxypyrazine at concentrations above 1 ppm. A method based on a short-time sampling of the headspace (1 min) was shown to better represent the equilibrium headspace concentration. Analysis of coffee brew with a 1-min headspace adsorption time was verified to be within the linear range for most compounds and thus appropriate for relative headspace quantification. Absolute quantification of volatiles, using isotope dilution assays (IDA), is not subject to biases caused by excess compound concentrations or complex matrices. The degradation of coffee aroma volatiles during storage was followed by relative headspace measurements and absolute quantifications. Both methods gave similar values for 3-methylbutanal, 4-ethylguaiacol, and 2,3-pentanedione. Acetic acid, however, gave higher values during storage upon relative headspace measurements due to concurrent pH decreases that were not seen with IDA.

Solid-phase microextraction method development for headspace analysis of volatile flavor compounds.

The potent odorants of regular-fat and low-fat Cheddar cheese were systematically characterized by aroma extract dilution analysis and gas chromatography/olfactometry of static headspace samples. Quantification of nine odorants using stable isotopes as the internal standards and calculation of odor activity values revealed methional, 2(5)-ethyl-5(2)-methyl-4-hydroxy-3(2H)-furanone (homofuraneol), diacetyl, acetic acid, and butyric acid as odorants with high aroma impact. Among the highly volatile compounds, the role of methanethiol and dimethyl sulfide for the nasal perception of the cheese flavor was established. The low-fat Cheddar cheese had a meaty-brothy odor defect that is believed to be caused by significantly higher amounts of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (Furaneol), homofuraneol, and methional in this cheese. Keywords: Cheddar cheese; regular fat; low fat; AEDA; static headspace; odor activity value

Identification and quantification of potent odorants in regular-fat and low-fat mild Cheddar cheese

Homogenates of salmon (A, B) and of cod (C, D) were stored at −60 °C (A, C) and at −13 °C (B, D). After boiling, A and C exhibited the mild flavor of the fresh fish, whereas B smelled fatty and train-oily and D showed a malty odor defect. The potent odorants of the four samples were screened by dilution experiments and then quantified by stable isotope dilution assays. Calculation of odor activity values (ratio of concentration to odor threshold) revealed (Z)-1,5-octadien-3-one (I), (E,Z)-2,6-nonadienal (II), propionaldehyde (III), acetaldehyde (IV), and methional (V) as the character impact odorants of A as well as I, II, IV, V, and (E,E)-2,4-decadienal as those of C. The off-flavors, which were formed when the raw material was stored at the higher temperature, were mainly caused by an increase of II, (Z)-3-hexenal, and (Z,Z)-3,6-nonadienal in B and of 3-methylbutanal in D. Keywords: Fish; cod; salmon; odor; off-flavor; lipid peroxidation; determination; AEDA

Changes in the odorants of boiled salmon and cod as affected by the storage of the raw material

Aroma extract dilution analysis of freshly harvested and boiled trouts (A) resulted in 24 odorants, of which 19 were identified. Twelve compounds were quantified by isotope dilution assays in sample A, in boiled trouts of which the raw material had been stored for 17 weeks at -13 o C (B), and in homogenates which were freshly prepared and boiled (C) or stored for 14 weeks at -13 o C and then boiled (D). Calculation of odor activity values (OAVs, ratio of concentration to odor threshold) revealed (Z)-1,5-octadien-3-one, (E,Z)-2,6-nonadienal, and methional are the most potent odorants of samples A and C

Changes in the odorants of boiled trout (Salmo fario) as affected by the storage of the raw material

Two headspace techniques based on mass spectrometry detection (MS), electronic nose, and solid phase microextraction coupled to gas chromatography−mass spectrometry (SPME-GC/MS) were evaluated for ...

Comparison of mass spectrometry-based electronic nose and solid phase microextraction gas chromatography-mass spectrometry technique to assess infant formula oxidation.

Christian Milo

Papers

Solid-phase microextraction method development for headspace analysis of volatile flavor compounds.

Identification and quantification of potent odorants in regular-fat and low-fat mild Cheddar cheese

Changes in the odorants of boiled salmon and cod as affected by the storage of the raw material

Changes in the odorants of boiled trout (Salmo fario) as affected by the storage of the raw material

Comparison of mass spectrometry-based electronic nose and solid phase microextraction gas chromatography-mass spectrometry technique to assess infant formula oxidation.