Shuji Yoshikawa

α-Glucosidase Inhibitory Activity of a 70% Methanol Extract from Ezoishige (Pelvetia babingtonii de Toni) and Its Effect on the Elevation of Blood Glucose Level in Rats

The 70% methanol extract from ezoishige (Pelvetia babingtonii de Toni) inhibited the rat-intestinal α-glucosidase, sucrase and maltase activities, with IC50 values of 2.24 and 2.84 mg/ml. Sucrose was orally administered with or without the extract to rats at 1000 mg/kg. The postprandial elevation in the blood glucose level at 15 and 30 min after the administration of sucrose with the extract was significantly suppressed when compared with the control. These results suggest that the extract from ezoishige has potent α-glucosidase inhibitors and would be effective for suppressing postprandial hyperglycemia.

Effect of halotolerant starter microorganisms on chemical characteristics of fermented chum salmon (Oncorhynchus keta) sauce.

Chum salmon sauce mash was inoculated with barley koji (barley steamed and molded with Aspergillus oryzae ) and halotolerant microorganisms (HTMs), Zygosaccharomyces rouxii , Candida versatilis , and Tetragenococcus halophilus , in nine different combinations under non-aseptic conditions similar to the industrial fish sauce production and fermented at 35 +/- 2.5 degrees C for 84 days. The changes in the chemical components, color, and sensory properties during fermentation were investigated. Free amino acid content was increased, and the browning of fish sauce was enhanced by the usage of barley koji during fermentation. The halotolerant yeast (HTY) produced ethanol and repressed the browning by consumption of reducing sugar. Inoculated Z. rouxii in the fish sauce mash produced 2-phenylethanol (2-PE) and 4-hydoxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), and C. versatilis in the fish sauce mash produced 4-ethylguaiacol (4-EG), known as characteristic flavor compounds in soy sauce, adding soy-sauce-like flavor to the fish sauce. Thus, inoculation of HTMs and barley koji was effective for conferring the soy-sauce-like flavor and increasing free amino acid and ethanol contents in fish sauce product.

Microbiota during fermentation of chum salmon (Oncorhynchus keta) sauce mash inoculated with halotolerant microbial starters: Analyses using the plate count method and PCR-denaturing gradient gel electrophoresis (DGGE)

Nine different combinations of mugi koji (barley steamed and molded with Aspergillus oryzae) and halotolerant microorganisms (HTMs), Zygosaccharomyces rouxii, Candida versatilis, and Tetragenococcus halophilus, were inoculated into chum salmon sauce mash under a non-aseptic condition used in industrial fish sauce production and fermented at 35 +/- 2.5 degrees C for 84 days to elucidate the microbial dynamics (i.e., microbial count and microbiota) during fermentation. The viable count of halotolerant yeast (HTY) in fermented chum salmon sauce (FCSS) mash showed various time courses dependent on the combination of the starter microorganisms. Halotolerant lactic acid bacteria (HTL) were detected morphologically and physiologically only from FCSS mash inoculated with T. halophilus alone or with T. halophilus and C. versatilis during the first 28 days of fermentation. Only four fungal species, Z. rouxii, C. versatilis, Pichia guilliermondii, and A. oryzae, were detected throughout the fermentation by PCR-denaturing gradient gel electrophoresis (PCR-DGGE). In FCSS mash, dominant HTMs, especially eumycetes, were nonexistent. However, under the non-aseptic conditions, undesirable wild yeast such as P. guilliermondii grew fortuitously. Therefore, HTY inoculation into FCSS mash at the beginning of fermentation is effective in preventing the growth of wild yeast and the resultant unfavorable flavor.

A dry starter of Tetragenococcus halophila for miso (soybean paste) fermentation

A dry starter of Tetragenococcus halophila was developed by fluidized-bed drying. Protective reagents from dehydration, cell supporting substances in fluidized-bed drying, and various conditions of the drying were investigated. Among the protective reagents tested, the highest cell viability wasderived from 20% (w/v) sucrose. Skim milk was adequate as a cell supporting substance. Good results were obtained at 8 m//min for a flow rate of cell suspension and 11 m/sec as a hot air velocity under the conditions tested. Under the conditions, the viability of T. halophila cells was 98.6%. Development of a dry starter of T. halophila is expected to provide an easy handling method of handling of the lactic acid bacterium for miso producers.

Fermentation of Scallop Paste with Lactic Acid Bacteria.

ホタテガイの貝柱は,生で食べるとソフトかつジューシーで,ほどよい甘みを持つなど優れた特徴がある素材である.本研究では,ホタテガイ貝柱を乳酸菌で発酵させ,発酵食品を製造する方法を開発した.ホタテガイ貝柱の発酵にはL.plantarumの粉末スターターを用いた.発酵させたホタテガイ貝柱は強い弾力性を持つ歯ごたえのあるゲルを形成した.さらに発酵による風味も感じられ,従来にない食品を作ることができた.