2. 职称英语
  3. Natural flavorings and fragrances are often costly and limited in supply. Fo

Natural flavorings and fragrances are often costly and limited in supply. Fo

游客2024-01-02  30
问题     Natural flavorings and fragrances are often costly and limited in supply. For example, the vital ingredient in a rose fragrance is extracted from natural rose oil at a cost of thousands of dollars a pound; an identical synthetic substance can be made for 1% of this cost. Since the early twentieth century, success in reproducing these substances has created a new industry that today produces hundreds of artificial flavors and fragrances.
    Some natural fragrances are easily synthesized; these include vanillin, the aromatic ingredient in vanilla, and benzaldehyde, the aromatic ingredient in wild cherries. Other fragrances, however, have dozens, even hundreds of components. Only recently has it been possible to separate and identit3, these ingredients by the use of gas chromatography and spectroscopy. Once the chemical identity is known, it is often possible to synthesize them. Nevertheless, some complex substances, such as the aroma of fresh coffee, have still not been duplicated satisfactorily.
    Many of the chemical compounds making up these synthetics are identical to those found in nature, and are as harmless or harmful as the natural substances. New products must be tested for safety, and when used in food, must be approved by the U.S. Food and Drug Administration.
The availability of synthetic flavors and fragrances has made possible a large variety of products, from inexpensive beverages to perfumed soap to used cars with applied "new car odor." [br] The underlined word "duplicated" in Paragraph 2 is closest in meaning to ______
选项 A、make double
B、make a copy of
C、produce something equal to
D、take from
答案 C
解析 从第二段前几句得知：Some natural fragrances are easily synthesized．(有些天然香料可以很容易地进行人工合成。)Other fragrances，however，have dozens， even hundreds of components．(而有些却包含有几十甚至上百种成分——言外之意，较难合成。)Only recently has it been possible to separate and identify these ingredients by the use of gas chromatography and spectroscopy．(只是到了最近，由于使用气相色谱分析和分光镜才能分离或鉴别出这些成分。)Once the chemical identity is known，it is often possible to synthesize them．(一旦了解了它们的化学成分，人们就有可能将之合成。)Nevertheless, some complex substances, (然而仍有一些复杂的成分，如新鲜咖啡的香味难以合成得令人满意。)；由此可推断出很难合成与新鲜咖啡香味相同的香料。选项C内容与此意最接近，所以是答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3326007.html
相关试题推荐
随机试题
最新回复(0)