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
2025-01-31
31
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] ______, 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
细节题型。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/3936483.html
相关试题推荐
______scientistshaveobservedincreasedpollutioninthewatersupply.A、LateB、
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Thefirstrecordeduseofnaturalgastolightstreetlampsitwasinthetowno
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
随机试题
Youwillsurelyfailintheexam______youworkhard.A、butB、ifC、unlessC如果你不努力学
43岁,女性,GP,带环避孕10年。近5年来经量渐增多,痛经逐渐加重,并经期低热
太阳热能发电,这是在不久的将来发展前景最光明的太阳能技术。这类系统将太阳的热汇集
(2020年真题)甲企业采用成本法核算长期股权投资,被投资方发生的下列事项中,导
惩罚是个体不断或重复受到某种刺激而对该刺激的反应逐渐减弱的现象。( )
下列一般应制成倍散的是A.眼用散剂 B.外用散剂 C.含低共熔成分的散剂
虽然太阳黑子变弱和地球变冷表面看有着70年的重合,但没有证据表明“小冰期”是由太
复印机在使用过程中会排放出对人体有害的气体,主要是:A.一氧化碳 B.二氧
票据丧失的补救措施主要有( )。A.挂失止付 B.让出票人重新补发 C.提
甲(女)乙(男)夫妻共有一套房,登记在甲女名下,后夫妻感情破裂,甲女与丙男伪造结
最新回复
(
0
)