Taro Nagasawa’s research while affiliated with Tamagawa University and other places

抄録 80℃, 30分間殺菌した豆乳にLactobacillus bulgaricus, Streptococcus thermophilusおよびBifidobacterium longumを混合接種して調製した発酵豆乳および発酵植物油添加豆乳ならびに市販プレーンヨーグルトを10日間冷温保蔵 (5℃) し, 48時間ごとにpH, 酸度, 乳酸菌およびビフィズス菌の生菌数およびホエー量を測定した。 発酵豆乳および発酵植物油添加豆乳では, 日数の経過とともにpHは低下し, 酸度が上昇した。 乳酸菌数は, いずれも減少傾向を示したが, 10日間保蔵で生菌数107以上を確保することができた。また, B.longumは, 10日間保蔵で108の菌数を保持した。 ホエー量は, 保蔵日数の経過とともに, いずれもわずかに増加したが, ヨーグルトより少なかった。 次に, 殺菌温度 (80℃, 90℃, 100℃, 30分間および121℃, 15分間) の異なる豆乳を用いて, 発酵豆乳および発酵植物油添加豆乳を調製して冷温保蔵した。その結果, 90℃, 30分間加熱の発酵豆乳は, 0日目のpHが最も高く, 酸度が最も低かったが, 冷温保蔵時にはその変化が, 最も大きかった。生菌数は, いずれの殺菌温度で冷温保蔵によって減少傾向を示したが, 10日間冷温保蔵で107以上を保持した。ホエー量は, いずれの発酵豆乳も殺菌温度が低いほど多かったが, ヨーグルトより低値であった。なお, 植物油添加の有無による差異はとくに認められなかった。

Effects of heat treatment and enrichment of vegetable fat on the fermentation of soymilks by lactic acid bacteria and bifidobacteria were examined. The marked acid development was observed in soymilks fermented by bifidobacteria compared with those by lactic acid bacteria. The heat treatment of soymilk at the temperatures higher than 100°C decreased titratable acidity, and increased hardness of the curd in the fermented soymilk with Bifidobacterium longum. Enrichment of vegetable fat to the soymilk did not affect the acidity and texture of the fermented soymilk. However, homogenization of the soymilk with high pressure lowered hardness of the curd.

ビフィズス菌の単独培養,または乳酸菌との混合培養による発育性ならびに大豆オリゴ糖の資化性について観察した.(1) 豆乳中におけるビフィズス菌の発育性について,24時間培養後のpHは,いずれの菌も4.53～4.76まで低下し,酸度は, 0.67～0.90%まで上昇した.また,培養20時間後の菌数は,いずれの菌種も10 3個のオーダーで増加し,豆乳中におけるビフィズス菌の増殖性はきわめて良好であった.(2) B. breveおよびB. longum とL. acidophilusとの混合培養では,ビフィズス菌数,生酸性は単独培養時のそれらを上回ったが,L. acidophilusの菌数は単独培養時のそれよりも低い傾向を示した.(3) ビフィズス菌による豆乳中のガラクトオリゴ糖の資化性は,特にスタキオースに対して優れていた.また,生成したグルコースは発酵に利用されたが,フルクトースおよびガラクトースは蓄積される傾向がみられた.(4) スクロース,ラフィノースまたはスタキオースを添加したMGLP培地において, B. breveの発育性は,スタキオース添加培地で優れていた.さらに,これらの糖を2種類または3種類含有する培地では,後者の方が良好な発育性を示した.

The effects of phytate on the hydrolysis of lactose with β-galactosidases from bovine liver and Escherichia coli were investigated. The activities of both β-galactosidases were decreased to the same extent by increased concentrations of phytate. The rates of inhibition of β-galactosidase activity from E. coli in a reaction mixture containing 10 mm of phytate were 78.9% and 64.4%, respectively, in the absence of and with 4 mm of Mg2 +. Therefore, it was found that the stimulatory effect of Mg2+ was hardly affected by the presence of phytate in the range from 2 to 10 mm. The β-galactosidase activity was also not influenced by preincubating β-galactosidase or lactose with phytate. Kinetic studies showed that the inhibition of β-galactosidase activity by phytate was of an uncompetitive type with a Ki value of 3.46 mm. Therefore, it is considered that phytate may interact with a complex of ß-galactosidase and lactose.

The effects of phytate on the hydrolysis of lactose with β-galactosidases from bovine liver and Escherichia coli were investigated. The activities of both β-galactosidases were decreased to the same extent by increased concentrations of phytate. The rates of inhibition of β-galactosidase activity from E. coli in a reaction mixture containing 10 mM of phytate were 78.9% and 64.4%, respectively, in the absence of and with 4mM of Mg²⁺. Therefore, it was found that the stimulatory effect of Mg²⁺ was hardly affected by the presence of phytate in the range from 2 to 10mM. The β-galactosidase activity was also not influenced by preincubating β-galactosidase or lactose with phytate. Kinetic studies showed that the inhibition of β-galactosidase activity by phytate was of an uncompetitive type with a Ki value of 3.46 mM. Therefore, it is considered that phytate may interact with a complex of β-galactosidase and lactose. © 1987, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.

Lactoferrin and serum albumin were measured immunologically in human colostrum and milk. Colostrum and milk contained .51 ± .11 and .19 ± .50 g of lactoferrin and .043 ± .016 and .030 ± .009 g of serum albumin per 100 ml.Precipitated lactoferrin in colostrum and in milk at pH 4.7 was .016 ± .005 and .017 ± .005 g per 100 ml. Precipitated serum albumin was less than 1.5% of total serum albumin in the milk.Acid casein, prepared by repeated isoelectric precipitation, contained 2.5 g of lactoferrin per 100 g protein. Lactoferrin was not detectable immunilogically in the major gel electrophoretic components of isoelectric human casein but was located in separate zones near the origin. Data relate to binding of lactoferrin and serum albumin by human casein.

Human casein was separated by gel filtration on a column of Sephadex G 200 with 0.1 M Tris buffer (pH 8.5) containing 1.0 M NaCl. The effluent which increased in turbidity at 25°C was centrifuged at 25,000 x g for 30 min and the precipitate was obtained as Fraction 6. After centrifugation, the effluent was separated into 5 elution fractions. Disc gel electrophoretic patterns of each fraction showed occurrence of secondary bands other than major bands especially in Fractions 3, 4 and 5. The casein solutions unheated and heated at 100°C for 5 and 10 min were kept at 5°C for 5 days. No marked changes of electrophoretic pattern were observed among these casein solutions. However, when a casein solution heated at 100°C for 5 min was chromatographed under the same condition, secondary bands also appeared.

Hydrogen ion, nitrogen distribution, ~-lactalbumin and serum albumin of hu- man milk at t~rst to fourth month of lac- tation were investigated. The average pH of milk was 7.34. Total N, casein N, whey protein N and nonprotein N of the milk were 179.0, 45.8, 90.5 and 41.5 mg per 100 ml respectively. Quantitative amounts of ~-lactalbumin and serum al- bumin in milk by disc gel electrophoresis were .224 and .072 g, respectively, per 100 ml of milk.