Some researchers think they have 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 (小球体) 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 locked 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 (隔仓
室) buried deep in the sea of fat. Trapped in this way, individual colonies cannot spread
and rapidly run out of nutrients (养料). 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.
36. The significance of Brocklehurst’s research is that ________.
A) it suggested a way to keep some foods fresh without preservatives
B) it discovered tiny globules in both cream and butter
C) it revealed the secret of how bacteria multiply in cream and butter
D) it found that cream and butter share the same chemical composition
37. According to the researchers, cream sours fast than butter because bacteria
________.
A) are more evenly distributed in cream
B) multiply more easily in cream than in butter
C) live on less fat in cream than in butter
D) produce less waste in cream than in butter
38. According to Brocklehurst, we can keep cream fresh by ________.
A) removing its fat
B) killing the bacteria
C) reducing its water content
D) altering its structure
39. The word “colonies” (Line 2, Para. 4) refers to ________.
A) tiny globules
B) watery regions
C) bacteria communities
D) little compartments
40. Commercial application of the research finding will be possible if salad cream can be
made resistant to bacterial attack ________.
A) by varying its chemical composition
B) by turning it into a solid lump
C) while keeping its structure unchanged
D) while retaining its liquid form
Part III Vocabulary and Structure (20 minutes)
Directions: There are 30 incomplete sentences in this part. For each sentence there are
four choices marked A), B), C) and D). Choose the ONE that best completes
the sentence. Then mark the corresponding letter on the Answer Sheet with a
single line through the center.
41. She ought to stop work; she has a headache because she ________ too long.
A) has been reading
B) had read
C) is reading
D) read
42. Niagara Falls is a great tourist ________, drawing millions of visitors every year.
A) attention
B) attraction
C) appointment
D) arrangement
43. I don’t mind ________ the decision as long as it is not too late.
A) you to delay making
B) your delaying making
C) your delaying to make
D) you delay to make
44. The hopes, goals, fears and desires ________ widely between men and women,
between the rich and the poor.
A) alter
B) shift
C) transfer
D) vary
45. Corn originated in the New World and thus was not known in Europe until
Columbus found it ________ in Cuba.
A) being cultivated
B) been cultivated
C) having cultivated
D) cultivating
46. The sale usually takes place outside the house, with the audience ________ on
benches, chairs or boxes.
A) having seated
B) seating
C) seated
D) having been seated
47. This kind of glasses manufactured by experienced craftsmen ________ comfortably.
A) is worn
B) wears
C) wearing
D) are worn
48. Some diseases are ________ by certain water animals.
A) transplanted
B) transformed
C) transported
D) transmitted
49. Wouldn’t you rather your child ________ to bed early?