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
2023-12-30
9
管理
问题
Natural flavorings and fragrances are often costly and limited in supply. For example, the essential 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] Brad jokes that it was a bit rough
having to
listen to carols all day at first but admits that they’ve grown so accustomed to
heard
them now that any other music just wouldn’t feel right.
选项
A、have to; hear
B、had to; hearing
C、to; hearing
D、had to; hear
答案
C
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3318342.html
相关试题推荐
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
Inspiteofrelativelycostly,thedieselengineishighlyefficientandneedss
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
随机试题
Itisplaincommonsense—themorehappinessyoufeel,thelessunhappiness
Economy,oneoftheprinciplesofsuccessinthedetailsofhousekeeping,co
Heisusedtoalotofattentionfromhiswife,whichwill________lessenwhenth
拟定菜单要结合宴请的()。A.形式和档次 B.宾客的身份 C.时间和季节
A.何首乌 B.苍术 C.麦冬 D.川牛膝 E.贝母皮部具有"云锦花纹"
工作人员在现场工作过程中,若因本身工作所引起异常情况或断路器(开关)跳闸、阀闭锁
从所给的四个选项中,选择最合适的一个填入问号处,使之呈现一定的规律性: A.如
关于因果关系,下列哪一选项是错误的?A:甲将被害人衣服点燃,被害人跳河灭火而溺亡
A.鹤虱 B.酸枣仁 C.金樱子 D.肉豆蔻 E.桑葚药用部位为干燥成熟
保留根管内的全部经失活的牙髓A.干髓术 B.根管充填术 C.塑化治疗 D.
最新回复
(
0
)