Propolis ethanolic extracts, with or without glycerol, were added into pasteurized, non-fat chocolate milk, which was artificially contaminated with Listeria monocytogenes. The addition of propolis ethanolic extracts dissolved into glycerol led to a definite anti-listerial effect in milk stored at 4 ℃, with both propolis concentrations tested (2 or 4 mg of dry propolis ethanolic extract per milliliter of chocolate milk) leading to inhibition of L. monocytogenes growth throughout 20 days of storage. The combined addition of propolis ethanolic extracts with glycerol was also effective in significantly reducing the rate of growth of L. monocytogenes in chocolate milk stored under improper (10 ℃) refrigeration storage conditions (more than five-fold increase in the generation time of L. monocytogenes compared to control trials). Finally, the combined addition of a deodorized propolis ethanolic extract with glycerol resulted in a significant anti-listerial effect upon storage of contaminated milk at 4 ℃ (more than three-fold increase in the generation time of L. monocytogenes compared to controls) and in a smaller anti-listerial effect upon milk storage at 10 ℃ (two-fold increase in the generation time of the pathogen compared to controls). Of note, chocolate milk containing deodorized propolis ethanolic extract and glycerol received a positive consumer acceptability score on the nine-point hedonic scale (median acceptability score of “7”). Hence, propolis may possess a promising role as a natural anti-listerial preservative in dairy drinks.

中文翻译：

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蜂胶和甘油对冷藏条件下巧克力牛奶中单核细胞增生李斯特菌的协同抑菌作用

蜂胶乙醇提取物，无论是否含有甘油，都被添加到巴氏杀菌的脱脂巧克力牛奶中，这种牛奶被人为地污染了单核细胞增生李斯特菌。添加溶解在甘油中的蜂胶乙醇提取物对 4 ℃ 储存的牛奶产生明确的抗李斯特菌作用，测试两种蜂胶浓度（每毫升巧克力牛奶 2 或 4 毫克干蜂胶乙醇提取物）导致 L . 单核细胞增生症在整个 20 天的储存中生长。蜂胶乙醇提取物与甘油的联合添加也能有效降低巧克力牛奶中单核细胞增生李斯特菌在不当（10 ℃）冷藏条件下的生长速度（L. monocytogenes 的产生时间增加了五倍以上）。单核细胞增生症与对照试验相比）。最后，除臭蜂胶乙醇提取物与甘油的组合添加在 4 ℃ 下储存受污染的牛奶时产生了显着的抗李斯特菌作用（与对照相比，单核细胞增生李斯特氏菌的产生时间增加了三倍以上），并且在较小的对 10 ℃ 牛奶储存的抗李斯特氏菌作用（与对照相比，病原体的产生时间增加了两倍）。值得注意的是，含有除臭蜂胶乙醇提取物和甘油的巧克力牛奶在九点享乐量表上获得了积极的消费者可接受性评分（可接受性中位数为“7”）。因此，蜂胶可能具有作为乳饮料中天然抗李斯特菌防腐剂的有希望的作用。