Furfuryl alcohol is a precursor for furfurylthiol in coffee.

This study investigated the role of furfuryl alcohol (FFA) in the formation of furfurylthiol (FFT), the most important odorant in roasted coffee, using in-bean and spiking experiments. Green beans were spiked with FFA, and after roasting FFT was quantified by stable isotope dilution analysis. The FFT level in the roasted beans increased dose-dependently with addition of FFA. Additionally, beans were spiked with isotopically labelled d2-FFA which generated isotopically labelled d2-FFT after roasting. However, no labelled furfural was observed. The results unambiguously show that FFA serves as a precursor of FFT in coffee. On the other hand, the data indicate that furfural stems not from oxidation of FFA and plays no major role as precursor for FFT formation during coffee roasting. The suggested formation pathway leads from FFA to the furfuryl cation, then protein-bound S-furfuryl-l-cysteine and by subsequent elimination to FFT.

Characterization and quantification of odor-active compounds in unsaturated fatty acid/conjugated linoleic acid (UFA/CLA)-enriched butter and in conventional butter during storage and induced oxidation.

Dairy products enriched in unsaturated fatty acids (UFA) and conjugated linoleic acids (CLA) have a higher nutritional value and are suggested to have beneficial health effects. However, such acids are susceptible to oxidation, and off-flavors may be formed during storage. This study was aimed to compare the most important odorants in UFA/CLA-enriched butter to that of conventional butter during storage and induced oxidation. Volatiles were isolated by solvent-assisted flavor evaporation and identified by gas chromatography-olfactometry and mass spectrometry. Aroma extract dilution analysis revealed 18 odorants that were quantified by stable isotope dilution analysis. Another important odorant, 3-methyl-1H-indole (mothball-like odor), was quantified by high-performance liquid chromatography. After storage, UFA/CLA-enriched butter showed higher concentrations of pentanal (fatty), heptanal (green), butanoic acid (cheesy), and delta-decalactone (peach-like). Photo-oxidation of butter samples induced increases in heptanal, (E)-2-octenal, and trans-4,5-epoxy-(E)-2-decenal, especially in conventional butter. The higher vitamin content in UFA/CLA samples may protect this butter from oxidation.

Winter/spring changes in fatty acid composition of farmhouse Idiazabal cheese due to different flock management systems.

Typically, two different flock managements are employed by basque sheepherders in winter and spring. Thus, seasonal changes in the fatty acid (FA) composition of Idiazabal PDO farmhouse cheeses were studied. Ewe's raw milk cheeses elaborated in winter and spring were collected after 120 days of ripening from 10 Idiazabal PDO farmhouses. In winter, concentrate and conserved forages were fed, whereas a part-time grazing system was adopted from spring onward. Spring cheeses had less (P

Synthesis and sensory characterization of novel umami-tasting glutamate glycoconjugates.

Two glycoconjugates of glutamic acid, namely, the N-glycoside dipotassium N-(d-glucos-1-yl)-l-glutamate (1) and the corresponding Amadori compound N-(1-deoxy-d-fructos-1-yl)-l-glutamic acid (2), have been synthesized in yields of 35 and 52%, respectively, using new Maillard-mimetic approaches, and their chemical structures have unequivocally been elucidated by 1D- and 2D-NMR and MS experiments. Systematic sensory studies revealed that both glycoconjugates exhibit pronounced umami-like taste with recognition taste thresholds of 1-2 mmol/L, close to that of monosodium glutamate (MSG). Contrary to an aqueous solution of MSG, 1 does not show the sweetish and slightly soapy by-note, but evokes an intense umami taste. Aqueous solutions of 2 were described by the descriptors umami, seasoning, and bouillon-like. Added to a bouillon base, which did not contain any taste enhancers, both glycoconjugates imparted a distinct umami character similar to the control sample containing the same amount of MSG on a molar basis. To the best of our knowledge, these types of glycoconjugates in general and, in particular, N-glucosyl glutamate and N-deoxyfructosyl glutamate have never been reported as taste active compounds having umami-like properties. Therefore, 1 and 2 represent a new class of umami-type taste compounds showing properties similar to the umami reference compound MSG. Systematic (13)C NMR measurements revealed that 1 was fairly stable in aqueous solutions under alkaline conditions (pH 8-10) as well as in dry form. However, it rapidly hydrolyzes in neutral and acidic solutions, giving rise to glucose and glutamate. In contrast, glycoconjugate 2 was observed to be rather stable in aqueous solution as well as in the presence of human saliva.

Hydrophilic interaction liquid chromatography coupled to electrospray mass spectrometry of small polar compounds in food analysis.

Reversed-phase liquid chromatography (RPLC) is commonly used to analyze nonvolatile components in food. However, polar low-molecular-weight compounds such as hydrophilic amino acids, di- and tripeptides, and organic acids are often not sufficiently retained and represent a challenge for RPLC. Hydrophilic interaction liquid chromatography in combination with electrospray mass spectrometry (HILIC-ESI-MS) on a carbamoyl-derivatized stationary phase was successfully employed to separate free amino acids and small polar peptides in complex food matrixes such as wheat gluten hydrolysate and Parmesan cheese. Glutamyl dipeptides were separated in a sequence-specific order with peptides with N-terminal glutamic acid residues eluting prior to their reverse sequence analogues. ESI-MSn detection in the positive ionization mode provided the necessary information to unambiguously identify isobaric peptides due to their characteristic fragmentation patterns. The technique also proved useful to separate and identify glycoconjugates between amino acids and reducing sugars (Amadori compounds). The investigation of organic acids present in food used a mobile phase comprising ammonium acetate buffer at pH 7 and mass spectrometric detection in the negative ionization mode.

Design of virtual libraries of umami-tasting molecules.

The introduction of molecular tools in food research offers the possibility to the food industry to benefit from the experience gained in the field by pharmaceutical companies. In this work we are showing how in silico virtual screening techniques based on molecular similarity were applied for identifying novel umami-tasting compounds. The results obtained suggest that 5'-ribonucleotides and monosodium glutamate might elicit the fifth basic taste via the same molecular mechanism. New algorithms were developed and used in this work, such as the dimension reduction of data sets by singular value decomposition and the introduction of the correlation dimension as a natural dimension of a chemical space. It is shown that the representations of molecular data sets in chemical spaces possess self-similar properties, characteristic of fractal objects.

Analysis of taste-active compounds in an enzymatic hydrolysate of deamidated wheat gluten.

Hydrolyzed plant proteins are widely used as ingredients in culinary products for their glutamate-like ("umami") taste. Three hydrolysates were prepared from wheat gluten using different enzymatic approaches. Comparison of their taste profiles revealed the enzymatic hydrolysate of an acid-deamidated wheat gluten (WGH-3) to be the least bitter of all and to elicit an intense glutamate-like taste. Its umami taste intensity was similar to that of an enzymatic hydrolysate in which glutaminase had been employed to convert free glutamine to glutamic acid and which had a 3-fold higher concentration of free glutamate. Reconstitution studies based on the results of the chemical analysis of WGH-3 and sensory comparison of the model solution and WGH-3 indicated that other components in addition to glutamate and organic acids contribute to its glutamate-like taste. WGH-3 was fractionated by gel permeation chromatography and reversed phase high-performance liquid chromatography, and two fractions with a pronounced glutamate-like taste were obtained. In one of them four pyroglutamyl peptides were tentatively identified: pGlu-Pro-Ser, pGlu-Pro, pGlu-Pro-Glu, and pGlu-Pro-Gln. Apparently, these peptides were formed by cyclization of the N-terminal glutamine residues during the preparation of the hydrolysates.