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
2024-01-02
61
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 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] ______ a substance can be synthesized.
选项
A、Upon identifying the basic components of it
B、Once chemically analyzed
C、When gas chromatography is used
D、If spectroscopy is adopted
答案
B
解析
见第二段倒数第二句(见75题答案),所以选项B为答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3326009.html
相关试题推荐
Sinceprehistoricpeoplefirstappliednaturalpigmentstocavewalls,______ha
[img]2012q1/ct_etoefm_etoeflistz_0438_20121[/img][br]Whatnaturalfeaturesof
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
"GeothermalEnergy"→Geothermalenergyisnaturalheat
EnergyfromNaturalGas1.Muchoftheworldgetsitsene
EnergyfromNaturalGas1.Muchoftheworldgetsitsene
随机试题
Youmightenjoyacupofcoffeeatyourlocalcoffeeshop.Butcoffeeispar
A、TowriteahumorcolumninScienceCareers.B、TowriteasciencecolumninSci
Sheboughtseveralclothesshopsandpreparedtobuildupachain.A、她盘下了几家服装店,并且
郊区型双坡道路断面图例中哪个是正确的?()A. B. C. D.
患者,女性,50岁。1型糖尿病,需注射胰岛素,护士对其进行的注射指导中,正确的是
根据公司信用类债券信息披露的有关规定,为债券提供担保的机构应当在每个会计年度结束
巨大脾脏常见于( )。A.急性粒细胞白血病 B.慢性粒细胞白血病 C.急性
六氟化硫湿度检测仪在使用前应先开机、自校准。
股指期货当存在期价低估时,交易者可反向套利。()
属于倍半萜的化合物是A.黄芪甲苷 B.银杏内酯 C.甘草酸 D.马兜铃酸
最新回复
(
0
)