Kenji Kumazawa

Character impact odorants of high-heat skim milk powder isolated by simultaneous distillation-extraction.

To identify the character impact odorant of high-heat skim milk powder (HHSMP), a comparative study using ultrahigh-temperature (UHT) milk was performed. Aroma concentrate was prepared by column adsorption combined with simultaneous distillation-extraction. Aroma extract dilution analysis (AEDA) revealed 58 aroma peaks with flavor dilution (FD) factors ranging from 10 to 3000; from these, 41 compounds were identified and 7 compounds were tentatively identified (FD factor > or = 300). Among these HHSMP and UHT milk components, methyl 2-methyl-3-furyl disulfide and bis(2-methyl-3-furyl) disulfide, which appeared to be generated during the processing of each product, were identified. When the results of the AEDA of both samples were compared, it was considered that the characteristic aroma of HHSMP was not explained by a single compound but instead formed from a mixture of several types of compounds contained in common with the UHT milk. The contribution of these compounds to the aroma of HHSMP was confirmed by an aroma simulation experiment.

New factor characterizing the in-mouth release of odorants (volatile thiols): compositional changes in odorants exhaled from the human nose during drinking.

The aim of this research was to investigate the relationship between the odorants in the model drink and the odorants reaching the olfactory epithelium using the Retronasal Flavor Impression Screening System (R-FISS). By application of the R-FISS to the odorants in the model drink, it was found that a methylthio ether [1-methoxy-3-methyl-3-(methylthio)butane] was detected with the original volatile thiol (4-methoxy-2-methyl-2-mercaptobutane) in the air exhaled through the nostrils via the nasal cavity after the model drink (including the original thiol) had been swallowed. In addition, this phenomenon was also observed in other volatile thiols (furfuryl mercaptan, ethyl 2-mercaptopropionate, 2-methyl-1-mercaptobutane, and 4-mercapto-4-methyl-2-pentanone). These compositional changes in thiols that were observed in the air exhaled through the nostrils could be affected by the chemical structure of each tested thiol and individual differences. These results pointed to a possibility that the odorants reaching the olfactory receptor via the throat during consumption of foods could not always retain their original chemical structures and compositions in foodstuffs. Therefore, the characteristic odor of volatile thiols might be perceived due to the stimuli of multiple compounds. To understand in detail flavor perception during the consumption of foods, not only the compositions or amounts of odorants in foodstuffs but also the compositional changes in odorants induced by biological reactions (reduction or methylation) need to be taken into consideration.

Sensory and structural characterisation of an umami enhancing compound in green tea (mat-cha)

Aimed at defining the key components for the umami taste of mat-cha a series of analysis were carried out on freshly prepared samples. The analyses included a bioactivity-guided fractionation using solvent extraction, solvent precipitation, preparative chromatographic separations and human psychophysical experiments. The LC-MS/MS and 1D/2D-NMR studies on isolated fractions led to the identification of (1R,2R,3R,5S)-5-carboxy-2,3,5-trihydroxy-cyclohexyl 3,4,5-trihydroxybenzoate known as theogallin, an umami enhancing compound in mat-cha. Sensory analysis showed that this compound can increase the umami intensity of sodium L-glutamate proportionally.