首页
登录
职称英语
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
2024-01-01
44
管理
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 identify 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 industry of producing hundreds of artificial flavors and fragrances probably appeared in______.
选项
A、2000
B、1953
C、1909
D、1810
答案
C
解析
细节题型。见第一段第三句:Since the early twentieth century, success in reproducingthese substances has created a new industry that…符合“二十世纪早期”条件的选项只有C,所以是答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3323239.html
相关试题推荐
[img]2012q1/ct_etoefm_etoeflistz_0438_20121[/img][br]Whatnaturalfeaturesof
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
EnergyfromNaturalGas1.Muchoftheworldgetsitsene
EnergyfromNaturalGas1.Muchoftheworldgetsitsene
随机试题
要他放弃职位是困难的,虽然他的年纪不允许他再在那位子上待下去。Itisdifficultforhimtogiveuphisposition,
Intheatmosphere,carbondioxideactsratherlikeaone-waymirrortheglas
Theopeningbetweentherockswasverynarrow,buttheboysmanagedto_________
Evidencecameup______animalswillbehaveabnormallyifthereisgoingtobea
型材表面应整洁,部分允许有裂纹、起皮、腐蚀和气泡等缺陷存在。
外国文艺表演团体来华演出名称中不能含有“国立”、”国家”、“皇家”等字样(
在实验实施过程中,一定要遵循的原则不包括A.随机 B.随意 C.对照 D.
督脉之络穴位于A、头项部 B、上腹部 C、下腹部 D、胸胁部 E、尾骶部
我国数学家华罗庚在一次报告中以“一支粉笔多长为好”为例来讲解他所倡导的优选法。对
钢筋宜在()状态下弯制。A、低温 B、常温 C、高温 D、加热
最新回复
(
0
)