填空题

Why does cream go bad faster than butter Some researchers think that it comes down to the structure of the food, not its chemical (36) --a finding that could help rid some processed foods of chemical preservatives. Cream and butter contain much the same (37) , so why cream should sour much faster has been a (38) . Both are emulsions--tiny globules of one liquid evenly (39) throughout another. The difference lies in what’s in the globules and what’s in the surrounding. In cream, fatty globules drift about in a sea of water. In butter, globules of a watery (40) are locked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the (41) . This means that in cream, the bacteria are free to grow throughout the mixture. When the situation is (42) , the bacteria are locked away in (43) buried deep in the sea of fat. (44) . They also slowly poison themselves with their waste products. In butter, there is a self-limiting system which stops the bacteria from growing. (45) . It is believed that it will be possible to make the emulsions used in salad cream, for instance, more like those in butter. (46) .