Why does cream go bad faster than butter? Some researchers think they the answer, and it comes down to the structure of the food, not its chemical composition - a finding that could help rid some processed foods of chemical preservatives. Cream and butter contain pretty much the same substances, so why cream should sour much faster has been a mystery. Both are emulsions - tiny globules of one liquid evenly distributed throughout another. The difference lies in what's in the globules and what's in the surrounding liquid, says Brocklehurst, who led the investigation. In cream, fatty globules drift about in a sea of water. In butter, globules of a watery solution are l ocked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the mixture. "This means that in cream, the bacteria are free to grow throughout the mixture,” he says. When the situation is reversed, the bacteria are locked away in compartments buried dee p in the sea of fat. Trapped in this way, individual colonies cannot spread and rapidly run out of nutrients. They also slowly poison themselves with their waste products. ”In butter, you get a self-limiting system which stops the bacteria growing,” says Brocklehurst. The researchers are already working with food companies keen to see if their products can be made resistant to bacterial attack through alterations to the food's structure. Brocklehurst believes it will be possible to make the emulsions used in salad cream, for instance, more like that in butter. The key will be to do this while keeping the salad cream liquid and not turning it into a solid lump.
为什么奶油比黄油变质更快？一些研究人员认为他们找到了答案，这取决于食物的结构，而不是它的化学成分——这一发现可能有助于去除一些加工食品中的化学防腐剂。奶油和黄油含有几乎相同的物质，所以为什么奶油会更快变酸一直是一个谜。两者都是乳液——一种液体均匀分布在另一种液体中的小球状物质。负责这项调查的布罗克赫斯特说，区别在于小球中的物质和周围液体中的物质。在奶油中，脂肪球在水的海洋中漂移。在黄油中，水溶液的球被困在脂肪的海洋中。使食物变质的细菌更喜欢生活在混合物的水区域。“这意味着在奶油中，细菌可以在整个混合物中自由生长，”他说。当情况逆转时，细菌会被锁在深深埋在脂肪海洋中的隔间里。这样，单个菌落就无法传播，营养物质也会迅速耗尽。它们还会用废弃物质慢慢毒害自己。布罗克赫斯特说：“在黄油中，你会获得一个自我限制的系统，它可以阻止细菌的生长。”研究人员已经在与食品公司合作，希望通过改变食品结构，看看他们的产品是否能抵抗细菌攻击。布罗克赫斯特相信有可能使沙拉奶油中使用的乳液更像黄油中的乳液。关键是要做到这一点的同时保持沙拉奶油的液体，不把它变成固体。
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