Etsuko Sugawara

The formation mechanism by yeast of 4-hydroxy-2(or 5)-ethyl-5(or 2 ) -methyl -3 (2H) -furanone in miso

The mechanism of the formation of 4-hydroxy-2(or 5)-ethyl-5-(or 2)-methyl-3(2H)-furanone (HEMF) with yeast under caltivation in a medium containing amino-carbonyl reactants of ribose and glycine was investigated using stable isotopes of the corresponding compounds. It was confirmed that the skeleton of the five-membered ring and the methyl group of the side chain of HEMF was formed from ribose, and that the ethyl group was derived from the glucose metabolite by yeast. The formation of HEMF was confirmed when acetaldehyde as the glucose metabolite and a cell-free extract from yeast were added to the medium containing amino-carbonyl reactants. These results suggest that the role of yeast in HEMF formation is not only to provide the glucose metabolite, but also in combining the amino-carbonyl reactants with the glucose metabolite.

Production and characterization of an interspecific hybrid between leek and garlic.

An interspecific hybrid between leek (Allium ampeloprasum L.) and garlic (Allium sativum L.) was produced by hybridization using a fertile garlic clone as a pollen donor and an ovary culture. The hybridity was confirmed by chromosome observation (2n = 3x = 24) and randomly amplified polymorphic DNA (RAPD) analysis. The interspecific hybrid showed a vigorous growth habit, and its foliage was larger than that of the parental species. The bulb of the interspecific hybrid was heavier than that of the parents, containing an intermediate number of cloves. The hybrid could be propagated vegetatively by planting cloves. The odor compounds of garlic, which leek did not have, were detected in the volatiles of the hybrid with a certain concentration. The results of the study suggest the possibility of direct use of an interspecific hybrid between A. ampeloprasum and A. sativum as a new crop.

Flavor Components of Shoyu and Miso Japanese Fermented Soybean Seasonings

The name soybean come form “bean of soy” which is derived from Portuguese Soya. In the 16th century, Portuguese imported Japanese soy sauce 
shoyu” and distributed it in the European countries. The name Soya is an alteration of the Japanese word “shoyu.” In this respect, shoyu has been an international food item since that time.

Effects of the Amino-Carbonyl Reaction of Ribose and Glycine on the Formation of the 2(or 5)-Ethyl-5(or 2)-methyl-4-hydroxy-3(2H)-furanone Aroma Component Specific to Miso by Halo-Tolerant Yeast

The formation of HEMF[2(or 5)-ethyl-5(or 2)-methyl-4-hydroxy-3(2H)-furanone], the aroma component specific to miso and soy sauce, was promoted by cultivating the halo-tolerant yeast, Zygosaccharomyces rouxii, in a medium including the amino-carbonyl reaction products based on ribose and glycine. The glucose concentration in the medium influenced the HEMF formation by Z. rouxii.

Diversity of odor-active compounds from local cultivars and wild accessions of Iwateyamanashi (Pyrus ussuriensis var. aromatica) revealed by Aroma Extract Dilution Analysis (AEDA)

Some local cultivars and wilds of Iwateyamanashi (Pyrus ussuriensis var. aromatica) that grows wild in Northern Tohoku, Japan have good aromatic fruit. Iwateyamanashi may be valuable germplasms as a donor of odor compounds in breeding of Japanese pear (Pyrus pyrifolia), because almost all Japanese pear cultivars have faint odor. Fruits odors from a local cultivar ‘Sanenashi’, a wild accession (i0830) in Iwateyamanashi, cultivars of ‘Kosui’ and ‘La France’ were characterized at first with comparative Aroma Extract Dilution Analysis (AEDA). Application of AEDA, based on Gas chromatography/Olfactometry analysis (GC/O), on the odor concentration prepared from ‘Sanenashi’ indicated the presence of 33 odor-active compounds including methyl and ethyl esters, aldehydes and alcohol. The eleven odor compounds from 16 accessions of Iwateyamanashi showed various combinations and wide range of odor concentrations by Principal Component Analysis (PCA). Especially 2 accessions of local cultivar ‘Natsunashi’ plotted in the highly ethyl ester group might be useful for Japanese pear breeding.

Formation by yeast of 2-furanmethanethiol and ethyl 2-mercaptopropionate aroma compounds in Japanese soy sauce

Two aroma compounds of volatile thiols, 2-furanmethanethiol (2FM) and ethyl 2-mercaptopropionate (ET2MP), were formed in five types of Japanese soy sauce during fermentation by yeast. The concentrations of 2FM and ET2MP in the soy sauce samples increased during alcoholic fermentation. The concentrations of 2FM and ET2MP were higher in the soy sauce fermented by Zygosaccharomyces rouxii than in that fermented by Candida versatilis. The enantiomers of ET2MP were separated by gas chromatography in a capillary column. The average enantiomeric ratio of ET2MP in the soy sauce was approximately 1:1. 2FM was formed by yeast in a medium prepared from cysteine and furfural, and cysteine is considered the key precursor of 2FM by yeast in soy sauce. Graphical Abstract Two important aroma compounds of volatile thiols, 2-furanmethanethiol etc., were formed in Japanese soy sauce during fermentation by yeast.

Contribution of 2-methyl-3-furanthiol to the cooked meat-like aroma of fermented soy sauce

The cooked meat-like aroma compound, 2-methyl-3-furanthiol (2M3F), was detected in fermented soy sauce (FSS) by GC-olfactometry and GC-MS. 2M3F was present in FSS at a concentration considerably greater than the perception threshold, and the 2M3F concentration increased with heating temperature. Sensory analysis indicated that with the addition of only 0.2 μg/L of 2M3F to the soy sauce sample, the cooked meat-like aroma is significantly stronger than that of sample without the addition of 2M3F. Hence, 2M3F contributes to the cooked meat-like aroma of FSS, which constitutes the key aroma component of FSS. In addition, 2M3F was generated from the addition of ribose and cysteine in FSS by heating at 120 °C, but it was not detected in a phosphate buffer under the same condition. Furthermore, 2M3F was not detected in acid-hydrolyzed vegetable-protein-mixed soy sauce (ASS) and heated ASS. These results indicated that fermentation by micro-organisms facilitates the generation of 2M3F in FSS. Graphical abstract 2-methyl-3-furanthiol (2M3F)contribute to the cooked meat-like aroma of fermented soy sauce, and this compound is a very important aroma component of fermented soy sauce.

Key compounds contributing to the fruity aroma characterization in Japanese raw soy sauce

In order to clarify the aroma characteristics of raw soy sauce (RS), the application of gas chromatography−olfactometry analysis to the aroma concentrate from a RS revealed 76 aroma peaks, of which 25 peaks showed fruit-like aromas. Furthermore, the head space aromatic compounds of RS were analyzed with 32 peaks detected. Ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, and ethyl 4-methylpentanoate were detected with higher flavor dilution factor (FD factor) than other aroma compounds by aroma extract dilution analysis. Quantitative analysis suggested that these compounds were common in all RS samples tested in this study, and were present at higher concentrations than their perception thresholds. The concentrations and the FD factors of these compounds were significantly decreased during the heating of the RS. Fruitiness is one of the key aroma characteristics of RS and the ethyl esters identified in this study are the key components contributing to this distinct aroma. Graphical abstract Fruitiness is one of the key aroma characteristics of raw soy sauce and the ethyl esters identified in this study are the key components contributing to this distinct aroma.