Keiko Tokuoka

Purification and Some Properties of an Erythrose Reductase from an Aureobasidium sp. Mutant

An erythrose reductase was obtained from the cells of an Aureobasidium sp. mutant having high erythritol-producing activity. This enzyme was purified 600-fold over the cell-free extract by ammonium sulfate precipitation, ion exchange chromatography, affinity chromatography, and hydrophobic chromatography. It gave a single band on polyacrylamide gel electrophoresis, and had a molecular weight of 37,000 and an isoelectric point of 4.8. This enzyme had maximum reductive activity at 45°C and pH 6.5. The optimum pH of the oxidative reaction was 9.5. It was stable at pH 6.0-8.0 and below 40°C. The enzyme showed the maximum activity to D-erythrose. D-Glyceraldehyde was reduced at a rate 66% of that for D-erythrose. p-Nitrobenzaldehyde, L-erythrulose, dihydroxyacetone, and D-glucuronate were also reduced, although at slower rates. The oxidative activity was less than 0.1% of the reductive one.

Temperature Rising Indicators over 7 or 13°C for Food

低温流通用示温材を開発し,その特性と実際の食品における低温流通用示温材の指示と細菌の増殖の関係について検討を行った.示温材は呈色温度が7℃あるいは13℃であり,その浸透誤差は10%未満であった.また,呈色開始温度に再現性が認められた.示温材の呈色は,低温細菌や一般細菌の増殖以前に起こるため温度上昇の警告となり,食品や原材料等の品質管理において有効な手段になりうると考えられた.

Database System for Wholesomeness Evaluation and Trouble-shooting of Food

食性病害あるいは食品の苦情事例のデータベースシステムを試作し,運用しつつ改良を行った.各事例ならび参考文献等をカード型データベースとして分類・記録し,必要に応じて検索した.このシステムの導入により,従来の勘にたよりがちな資料の検索に比べ,見落としやムダが少なくなり,食品の健全性評価のための資料の収集や調査方針の決定が早くなった.また,このシステムは,食品の健全性確保や苦情原因の調査等に不慣れな初任者の教材としての利用も可能であった.