The polyphenol oxidase (o-diphenol : oxygen oxidoreductase, EC. 1.10.3.1, PPO) of leaf lettuce was purified about 23.4-fold with a recovery rate of 13.3% by ammonium sulfate fractionation, ion exchange chromatography, hydrophobic chromatography, and gel filtration. The purified enzyme appeared as a single band on polyacrylamide gel electrophoresis (PAGE) and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The estimated molecular weights of the enzyme were about 45, 000 and 46, 000 as determined by gel filtration and SDS-PAGE, respectively. The purified enzyme strongly oxidized chlorogenic acid and (-) -epicatechin. The Km (Michaelis constant) values of the enzyme were 1.0 mM for chlorogenic acid (pH 5.0, 30°C) and 1.4 mM for (-) -epicatechin (pH 8.0, 30°C). The optimum pHs of the enzyme were 5.0 for chlorogenic acid oxidase (ChO) and 8.0 for (-) -epicatechin oxidase (EpO). In the pH range from 5 to 8, both activities of ChO and EpO were stable at 4°C for 22h. The optimum temperatures of both activities were 30°C. Both activities were stable up to 50°C after heat treatment for 10 min. The purified enzyme was strongly inhibited by L-ascorbic acid and L-cysteine at 5 mM. These results suggest that the enzymatic browning of leaf lettuce is prevented by treatment with sodium chloride, L-ascorbic acid or L-cysteine at 5 mM.

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In this study, we investigated the postharvest changes in glutamine synthetase (GS; EC 6. 3. 1. 2), 1-aminocyclopropane-1-carboxylate (ACC) synthase (EC 4. 4. 1. 14), ACC oxidase (EC 1. 4. 3) and phenylalanine ammonia lyase (PAL; EC 4. 3. 1. 5) activities in relation to ammonia content, ethylene production, respiration rate, and texture and color changes after harvest of moso bamboo (Phyllostachys edulis) shoots stored at 1 and 20°C for up to 9 days. GS activity decreased in shoots stored at 20°C with increasing ammonia content up to approximately 6-fold the initial content after a 9-day storage period. Although the highest ACC oxidase activity corresponded to the highest ethylene production, the highest ACC synthase activity was delayed 8 h or more compared with that in the previous study. The development of PAL activity coincided with an increase in breaking strain at 20°C up to 3 days. Low-temperature storage of shoots at 1°C retained good shoot color and quality since it was effective in decreasing respiration rate, ammonia accumulation, ACC synthase, ACC oxidase, and PAL activities after the harvest of moso bamboo shoots.

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The transitions of a molasses pigment and polyphenol during the decolorization of molasses during the cultivation of Mycelia sterilia M1 were investigated by gel filtration chromatography. In the chromatogram of the molasses pigment, two peaks were confirmed, corresponding to molecular weights of approximately 11, 800 and 5, 900. The molecular weight distribution of the molasses pigment corresponded to that of polyphenol. When M. sterilia M1 was cultured in 100g/l molasses at 30°C for 10days under an aerobic condition, approximately 80% of the molasses pigment and 95% of polyphenol were removed. With increases in decolorization efficiency and polyphenol removal efficiency during M. steriliaM1 cultivation, the two peaks observed in the molecular weight distributions of both, the molasses pigment and polyphenol decreased in area. The cultivation of M. sterilia M1 decreased the molecular weights of the molasses pigment (approximately 13, 700 and 5, 700) and polyphenol during the decolorization of molasses.

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The effects of storage temperature on antioxidant activity and total phenolic content were investigated in sweet basil (Ocimum basilicum L.) leaves. Sweet basil leaves were sealed in 0.068mm polyethylene packages and stored at 3°C and 25°C. The leaves stored at 3°C exhibited a higher weight loss and severer chilling injury symptoms in the form of browning than those stored at 25°C. There were slight changes in fresh weight and leaf color during storage at 25°C. Antioxidant activity on the first day of storage decreased markedly regardless of storage temperature, and showed little correlation with total phenolic content. The respiration rate of the leaves stored at 3°C was almost twice as high as that of the leaves stored at 25°C after two days of storage. Neither of the tested storage temperatures prevented the decrease in antioxidant activity after harvest.

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Vanadium concentration in 105 bottles of various commercial mineral waters was measured by inductively coupled plasma mass spectrometry (ICP-MS). (1) The calibration curve of vanadium concentration obtained by ICP-MS showed a good linearity. (2) The chloride (Cl^-) affecting the measurement of vanadium concentration did not affect the recovery rate of vanadium up to 100 ppm when Cl^-was added as NaCl. (3) The average vanadium concentration in all the commercial mineral waters was 0.013mg/l, whereas the average vanadium concentration in groundwater from the foot of Mt. Fuji was 0.059mg/l. Forty-five percent of the mineral waters showed a vanadium concentration below 0.001mg/l. (4) One of the imported bottles of commercial mineral waters showed the same vanadium concentration as groundwater around Mt. Fuji.

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