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中文摘要：
为探讨焦亚硫酸钠的保鲜防腐机制,采用毒理学方法研究保鲜剂对酵母细胞的毒性效应。结果表明：在100~1 000μmol/L浓度范围内,焦亚硫酸钠可抑制酵母细胞生长分裂,诱发细胞死亡;随着焦亚硫酸钠浓度升高和作用时间延长,其对酵母细胞的毒性效应也逐渐增强。经100μmol/L焦亚硫酸钠作用2 h后,酵母细胞生长曲线与对照组产生差异;300μmol/L焦亚硫酸钠处理6 h后,酵母细胞死亡率显著高于对照组,用抗坏血酸或LaCl3预处理可阻止焦亚硫酸钠诱发的酵母细胞死亡,表明焦亚硫酸钠通过诱导酵母细胞内活性氧和Ca2＋水平升高来引发细胞死亡。研究还发现,相同浓度的焦亚硫酸钠作用后,pH 4.0组酵母细胞的死亡率明显高于pH 7.0组,即酸性环境能增强焦亚硫酸钠对酵母细胞的毒性作用,有助于保鲜剂的抑菌防腐。
英文摘要：
Sodium metabisulfite is commonly used as a food preservative and antioxidant for dried foods, fruit concentrate juices and fresh fruits. It is the most efficiently preservative for table grape since table grapes are subject to serious water loss and decay while making the long trip from the vine to tables around the world. Herein, the effects of sodium metabisulfite on cell viability were explored in the model eukaryote Saccharomyces cerevisiae. The growth curve of yeast cells was measured by optical density, and cell viability was examined based on methylene blue staining method. Randomly selected views on the tested yeast cells were monitored under a microscope to determine the number of dead cells and the total number of scored cells. The results indicated that sodium metabisulfite could inhibit yeast cell growth and division, and even cause cell death. The toxicity of sodium metabisulfite was increased with increasing concentration and prolonged duration. Either high concentration for a shorter-term exposure or low concentration for a long-term exposure showed significant toxic effects on yeast cells. Exposure to 100 to 1 000 μmol/L sodium metabisulfite for 6 h could cause significant cell death, and both antioxidant ascorbic acid and plasma membrane Ca2＋ channel inhibitor La Cl3 blocked sodium metabisulfite-induced cell death. These results indicated that sodium metabisulfite could cause yeast cell death via reactive oxygen species（ROS） production and Ca2＋ influx. However, the death rate increased in acidic environment. The cell death rate in pH 4.0 treatment group was higher than that in pH 7.0 treatment group, demonstrating the enhanced sulfur dioxide（SO2） toxicity in acidic medium. It was found that the p H of waterdrop on the surface of SO2-fumigated table grapes was around 3.5 to 4.0, which was lower than the control without SO2 fumigation, suggesting that acid environment caused by SO2 fumigation is a way to prevent infection and prolong the shelf life of table grapes.
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