Research for Development of Food Quality Estimation System Using Oxygen Sensor

本研究旨在开发一套氧传感器化学食品质量评价系统。采用抗坏血酸氧化酶（ASOD）法，在氧传感器的水封反应池中测定溶解氧（DO）的减少量，通过抗坏血酸的酶促氧化反应快速测定果蔬的新鲜度指数。考察了反应温度、pH和缓冲液浓度对DO吸收率（DO降低率）的影响。脱氢抗坏血酸（DHA，氧化维生素C）用SH还原剂和葡萄糖，葡萄糖氧化酶（GOD）氧化，化学还原为ASA，用测定DO减少量的方法测定。采用上述方法监测贮藏后绿豆芽的ASA还原量、ASA总含量和葡萄糖含量的变化。监测成分的减少与感觉新鲜度有良好的相关性。为了节省测定鱼或肉的k值（新鲜度指数）所需的酶（酶价格昂贵）的使用，将核苷酸氧化酶（NP）和黄嘌呤氧化酶（XO）共固定在多孔尼龙膜上。所得到的酶电极可用于肉类新鲜度的重复酶测定。提出了一种基于氧传感器过氧化氢酶测定的食品微生物活细胞计数快速测定方法。在酵母和大肠杆菌细胞悬浮液上的实验结果表明，过氧化氢酶活性与细胞计数高度相关，范围为10 -10个细胞/ml。构建了一套便于食品微生物检测的全自动计算机辅助检测系统。该系统不仅可用于食品的新鲜度测定，还可用于其它化学食品的分析。测定溶解氧增加的方法也被用于检查牛奶、“味噌”和“纳豆”中的细胞计数。

This research was done to develop chemical food quality estimation system using oxygen sensor.1. Freshness index of fruits and vegetables was determined rapidly by enzymatic oxidation reaction of ascorbic acid using ascorbate oxidase (ASOD), following the method for measorement of the decrease in dissolved oxygen (DO) in a water sealed reaction cell of the oxygen sensor. The effect of temperature, pH and buffer concentration of the reaction mixture on the DO uptake (DO decrease) were determined.Dehydroascorbic acid (DHA, oxidized vitamin C) chemically reduced to ASA using SH reducing agent and glucose, oxidized by glucose oxidase (GOD) were determined by the method for measuring the decrease in DO. Changes in reduced ASA, total ASA and glucose content of stored mungbean sprouts were monitored using the same method mentioned above. Decrease of monitored components showed good correlation with sensory freshness.2. In order to save the use of enzymes (enzymes are very expensive) for the determination of K-value (freshness index of fish or meat), co-immobilization of nucleotide oxidase (NP) and xanthine oxidase (XO) on porous nylon membrane was carried out. The resulting enzyme electrode was useful for a repeated enzyme assay of meat freshness.3. A rapid method for estimating viable cell count of food microbes based on catalase assay using oxygen sensor was proposed. Results of the experiments on yeast and E. Coli cell suspension showed a high correlation between catalase activity and cell count ranging from 10 -10 cells/ml. A fully antomated computer-aided system, convenient for microbial test of foods was constructed. Future development of the system was expected not only for freshness index determination but also for other chemical food analysis. The method for measuring the increase in dissolved oxygen was also applied to check cell count in milk, "miso" and "natto".