Structure-Odor Correlations in Homologous Series of Mercapto Furans and Mercapto Thiophenes Synthesized by Changing the Structural Motifs of the Key Coffee Odorant Furan-2-ylmethanethiol.

Furan-2-ylmethanethiol (2-furfurylthiol; 2-FFT, 1) is long-known as a key odorant in roast and ground coffee and was also previously identified in a wide range of thermally treated foods such as meat, bread, and roasted sesame seeds. Its unique coffee-like odor quality elicited at very low concentrations, and the fact that only a very few compounds showing a similar structure have previously been described in foods make 1 a suitable candidate for structure-odor activity studies. To gain insight into the structural features needed to evoke a coffee-like odor at low concentrations, 46 heterocyclic mercaptans and thio ethers were synthesized, 32 of them for the first time, and their odor qualities and odor thresholds were determined. A movement of the mercapto group to the 3-position kept the coffee-like aroma but led to an increase in odor threshold. A separation of the thiol group from the furan ring by an elongation of the carbon side chain caused a loss of the coffee-like odor and also led to an increase in odor thresholds, especially for ω-(furan-2-yl)alkane-1-thiols with six or seven carbon atoms in the side chain. A displacement of the furan ring by a thiophene ring had no significant influence on the odor properties of most of the compounds studied, but the newly synthesized longer-chain 1-(furan-2-yl)- and 1-(thiophene-2-yl)alkane-1-thiols elicited interesting passion fruit-like scents. In total, only 4 out of the 46 compounds also showed a coffee-like odor quality like 1, but none showed a lower odor threshold. Besides the odor attributes, also retention indices, mass spectra, and NMR data of the synthesized compounds were elaborated, which are helpful in possible future identification of these compounds in trace levels in foods or other materials.

Historical Review on the Identification of Mesifurane, 2,5-Dimethyl-4-methoxy-3(2 H)-furanone, and Its Occurrence in Berries and Fruits.

Mesifurane, 2,5-dimethyl-4-methoxy-3(2 H)-furanone, is a natural compound used a worldwide as a flavoring for foods, beverages, and cosmetics. Global sales of mesifurane are around $100 million. Its significance as a flavor-impact compound in some Nordic berries was discovered in the early 1970s in Finland. Synthesized mesifurane was used as a key compound in aroma mixes exploited in a Finnish patent. Mesifurane is a significant flavorant in arctic brambles, mangoes, strawberries, and many other fruits and berries and is an enzymatic methylation product of 2,5-dimethyl-4-hydroxy-3(2 H)-furanone. Because of the obscurity of the information on the history of the commonly used trivial name, mesifurane, it is time to lift the veil and reveal the background of the present situation. The key player was a northern berry, arctic bramble ( Rubus arcticus), the Finnish name of which is mesimarja. Forty years ago, aroma research was limited by technical factors, but nowadays there is a surplus of information.

Rubemamine and Rubescenamine, Two Naturally Occurring N-Cinnamoyl Phenethylamines with Umami-Taste-Modulating Properties.

Sensory screening of a series of naturally occurring N-cinnamoyl derivatives of substituted phenethylamines revealed that rubemamine (9, from Chenopodium album) and rubescenamine (10, from Zanthoxylum rubsecens) elicit strong intrinsic umami taste in water at 50 and 10 ppm, respectively. Sensory tests in glutamate- and nucleotide-containing bases showed that the compounds influence the whole flavor profile of savory formulations. Both rubemamine (9) and rubescenamine (10) at 10-100 ppm dose-dependently positively modulated the umami taste of MSG (0.17-0.22%) up to threefold. Among the investigated amides, only rubemamine (9) and rubescenamine (10) are able to directly activate the TAS1R1-TAS1R3 umami taste receptor. Moreover, both compounds also synergistically modulated the activation of TAS1R1-TAS1R3 by MSG. Most remarkably, rubemamine (9) was able to further positively modulate the IMP-enhanced TAS1R1-TAS1R3 response to MSG ∼ 1.8-fold. Finally, armatamide (11), zanthosinamide (13), and dioxamine (14), which lack intrinsic umami taste in vivo and direct receptor response in vitro, also positively modulated receptor activation by MSG about twofold and the IMP-enhanced MSG-induced TAS1R1-TAS1R3 responses approximately by 50%. In sensory experiments, dioxamine (14) at 25 ppm in combination with 0.17% MSG exhibited a sensory equivalent to 0.37% MSG.

New Umami Amides: Structure-Taste Relationship Studies of Cinnamic Acid Derived Amides and the Natural Occurrence of an Intense Umami Amide in Zanthoxylum piperitum.

A series of aromatic amides were synthesized from various acids and amines selected from naturally occurring structural frameworks. These synthetic amides were evaluated for umami taste in comparison with monosodium glutamate. The effect of the substitution pattern of both the acid and the amine parts on umami taste was investigated. The only intensely umami-tasting amides were those made from 3,4-dimethoxycinnamic acid. The amine part was more tolerant to structural changes. Amides bearing an alkyl- or alkoxy-substituted phenylethylamine residue displayed a clean umami taste as 20 ppm solutions in water. Ultraperformance liquid chromatography coupled with a high quadrupole-Orbitrap mass spectrometer (UPLC/MS) was subsequently used to show the natural occurrence of these amides. (E)-3-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenethyl)acrylamide was shown to occur in the roots and stems of Zanthoxylum piperitum, a plant of the family Rutaceae growing in Korea, Japan, and China.

Evaluation of different methods for immobilization of Candida antarctica lipase B (CalB lipase) in polyurethane foam and its application in the production of geranyl propionate.

With the aim of studying the best method for the interaction of polyurethane (PU) foam and Candida antarctica lipase B, different methods of CalB immobilization were studied: adsorption (PU-ADS), bond (using polyethyleneimine) (PU-PEI), ionic adsorption by PEI with cross-linking with glutaraldehyde (PU-PEI-GA) and entrapment (PU). The characterization of immobilized enzyme derivatives was performed by apparent density and Fourier transform infrared spectroscopy. The free enzyme and enzyme preparations were evaluated at different pH values and temperatures. The highest enzyme activity was obtained using the PU method (5.52 U/g). The methods that stood out to compare the stabilities and kinetic parameters were the PU and PU-ADS. Conversions of 83.5 and 95.9 % for PU and PU-ADS derivatives were obtained, in 24 h reaction, using citronella oil and propionic acid as substrates.

Study of production and pyrolysis characteristics of sweet orange flavor-ß-cyclodextrin inclusion complex.

Flavor plays an important role and has been widely used in foods. Encapsulation can prevent the loss of volatile aromatic ingredients, provide protection and enhance the stability of the flavor. Kinetic and thermodynamic parameters are helpful in understanding the mechanism of molecular recognition between hosts and guests. This work focused on the study of production of a sweet orange flavor-ß-cyclodextrin (CD) inclusion complex, and investigated the combination of flavor and ß-CD by thermogravimetric analysis. Pyrolysis characteristics, kinetic and thermodynamic parameters of the flavor-ß-CD inclusion complex were determined. The results showed that the flavor-ß-CD inclusion complexes can form large aggregates in water. During thermal degradation of blank ß-CD and flavor-ß-CD inclusion complex, three main stages can be distinguished. The thermogravimetric (TG) curve of blank ß-CD shows a leveling-off from room temperature to 250°C, while the TG curve of flavor-ß-CD inclusion complex is downward sloping in this temperature range.

Hemisynthesis of dihydroumbellulols from umbellulone: new cooling compounds.

Although menthol is a common ingredient used in food products, other molecules also evoke coolness through stimulation of the somatosensory system. To discover new molecules having cooling properties, we virtually screened the chemical structures of terpenes and sesquiterpenes to find structures that are similar to (-)-menthol. We realized that dihydroumbellulols could be good candidates. Although their occurrence was reported in Hyptis pectinata Poit, we were unable to obtain these molecules from the plant or to prove their natural occurrence. Therefore, we extracted (-)-(R)-umbellulone from Umbellularia californica Nutt. The (-)-(R)-umbellulone was reduced to prepare (1R,2R/S)-1-isopropyl-4-methylbicyclo[3.1.0]hex-3-en-2-ol, (1R,4R/S)-1-isopropyl-4-methylbicyclo[3.1.0]hexan-2-one, and (1R,2RS,4RS)-1-isopropyl-4-methylbicyclo[3.1.0]hexan-2-ols, named dihydroumbellulols. Sensory analysis suggested that (1R,2R,4S)-dihydroumbellulol has a pleasant, trigeminal cooling effect, about 2-3 times less cooling than (-)-menthol, with a weak odor slightly reminiscent of eucalyptol. In addition, a previously unreported compound was discovered, (-)-(1R)-1-isopropyl-4-methylenebicyclo[3.1.0]hexan-2-one.

History of glutamate production.

In 1907 Kikunae Ikeda, a professor at the Tokyo Imperial University, began his research to identify the umami component in kelp. Within a year, he had succeeded in isolating, purifying, and identifying the principal component of umami and quickly obtained a production patent. In 1909 Saburosuke Suzuki, an entrepreneur, and Ikeda began the industrial production of monosodium l-glutamate (MSG). The first industrial production process was an extraction method in which vegetable proteins were treated with hydrochloric acid to disrupt peptide bonds. l-Glutamic acid hydrochloride was then isolated from this material and purified as MSG. Initial production of MSG was limited because of the technical drawbacks of this method. Better methods did not emerge until the 1950s. One of these was direct chemical synthesis, which was used from 1962 to 1973. In this procedure, acrylonitrile was the starting material, and optical resolution of dl-glutamic acid was achieved by preferential crystallization. In 1956 a direct fermentation method to produce glutamate was introduced. The advantages of the fermentation method (eg, reduction of production costs and environmental load) were large enough to cause all glutamate manufacturers to shift to fermentation. Today, total world production of MSG by fermentation is estimated to be 2 million tons/y (2 billion kg/y). However, future production growth will likely require further innovation.

Synthesis and evaluation of new alkylamides derived from alpha-hydroxysanshool, the pungent molecule in szechuan pepper.

Szechuan pepper is widely used in Asia as a spice for its pleasant pungent and tingling sensations, produced by natural alkylamides called sanshools. alpha-Hydroxysanshool, the main alkylamide found in the pericarp of the fruit, stimulates sensory neurons innervating the mouth by targeting two chemosensitive members of the transient receptor potential (TRP) channels, TRPV1 and TRPA1. As it was previously found that configuration of the unsaturations in the alpha-hydroxysanshool alkyl chain is required for TRPA1 but not TRPV1 selectivity, this study aimed at obtaining more potent and selective TRPA1 agonists using alpha-hydroxysanshool as a starting material. This paper reports the preparation of new alkylamides derived from sanshool and their efficacy in stimulating TRPA1 and TRPV1 receptors. The data provide knowledge of the main sanshool chemical functionalities required for TRP channel activation, but they also evidence new selective and potent TRPA1 agonists based on alpha-hydroxysanshool.

Lipases for biotechnology.

Lipases constitute the most important group of biocatalysts for biotechnological applications. The high-level production of microbial lipases requires not only the efficient overexpression of the corresponding genes but also a detailed understanding of the molecular mechanisms governing their folding and secretion. The optimisation of industrially relevant lipase properties can be achieved by directed evolution. Furthermore, novel biotechnological applications have been successfully established using lipases for the synthesis of biopolymers and biodiesel, the production of enantiopure pharmaceuticals, agrochemicals, and flavour compounds.

Practical synthesis of 3-methylnonane-2,4-dione, an intense strawlike and fruity flavored compound.

A practical synthesis of 3-methylnonane-2,4-dione, which is an intense strawlike and fruity flavored compound, has been performed by the aldol condensation of n-hexanal and methyl ethyl ketone, followed by oxidation using sodium hypochlorite in the presence of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxide in an overall yield of 59%. The purification of 3-methylnonane-2,4-dione with high purity was performed via copper complexes.

Prospects for the bioengineering of isoprenoid biosynthesis.

Over the last decade, our understanding of isoprenoid biosynthesis has progressed to the stage where specific strategies for the bioengineering of essential oil production can be considered. This review provides a current overview of the enzymology and regulation of essential oil isoprenoid biosynthesis. The reaction mechanisms of the synthases which produce many of the basic isoprenoid skeletons are described in detail. Coverage is also provided of the regulation of isoprenoid biosynthesis, including the roles played by tissue and subcellular compartmentation, and by partitioning of intermediates between different branches of isoprenoid metabolism. This provides necessary context for rationally targeting specific enzymes of metabolic pathways for bioengineering essential oil production. Wherever possible, emphasis is placed on research specific to essential oil isoprenoid biosynthesis, although relevant work related to other isoprenoids is also considered when it can provide useful insights. Finally, building upon this understanding of essential oil isoprenoid biosynthesis, several approaches to the bioengineering of isoprenoid metabolism are considered.