美国科学60秒 SSS 2013-02-27
时间：2018-12-24 作者：英语课 分类：Scientific American(二)月
英语课
As many San Franciscans have noticed, sourdough bread stays fresher longer than the regular stuff. Sourdough’s extended freshness is due to extra fermentation that traps more moisture in the dough 1. But now we know that sourdough’s longevity 2 is also because it can ward 3 off mold. Because bacteria in some sourdough starters(起动装置；开胃菜；发酵剂；酵母) actually produce mold-killing compounds - essentially 4 natural preservatives 5(防腐剂).
Most sourdough starters contain strains(气质；性情；种类) of Lactobacillus(乳酸菌) bacteria, like the poster child Lactobacillus sanfranciscensis. Eight years ago, researchers isolated 6 another strain called Lactobacillus hammesii from a French sourdough starter.
They've now discovered that the strain pumps out a potent 7 antifungal as it digests bread flour. So they baked bread with the L. hammesii starter, sliced it, and waited. The loaf resisted mold for 12 days, a few days more than L. sanfranciscensis sourdough, and twice as long as typical bread. Those results are in the journal Applied 8 and Environmental Microbiology.
L. hammesii isn't the most common sourdough strain. But the researchers say it could eliminate the need for added preservatives, which would mean store-bought sourdough that's additive-free and lasts for weeks. Assuming you can wait that long to eat it.
1 dough
n.生面团；钱，现款
- She formed the dough into squares.她把生面团捏成四方块。
- The baker is kneading dough.那位面包师在揉面。
2 longevity
n.长命；长寿
- Good habits promote longevity.良好的习惯能增长寿命。
- Human longevity runs in families.人类的长寿具有家族遗传性。
3 ward
n.守卫，监护，病房，行政区，由监护人或法院保护的人（尤指儿童）；vt.守护，躲开
- The hospital has a medical ward and a surgical ward.这家医院有内科病房和外科病房。
- During the evening picnic,I'll carry a torch to ward off the bugs.傍晚野餐时，我要点根火把，抵挡蚊虫。
4 essentially
adv.本质上，实质上，基本上
- Really great men are essentially modest.真正的伟人大都很谦虚。
- She is an essentially selfish person.她本质上是个自私自利的人。
5 preservatives
n.防腐剂( preservative的名词复数 )
- The juice contains no artificial preservatives. 这种果汁不含人工防腐剂。
- Meat spoils more quickly without preservatives. 不加防腐剂，肉会坏得快。 来自《现代英汉综合大词典》
6 isolated
adj.与世隔绝的
- His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
- Patients with the disease should be isolated. 这种病的患者应予以隔离。