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
2023-12-31
37
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] Why does the author mention fresh coffee in Paragraph 2?
选项
A、As an example of complex substances having not been duplicated satisfactorily.
B、Because the coffee fragrance is hard to produce.
C、To conclude the passage.
D、The smell of fresh coffee is inviting.
答案
A
解析
推断题型。见上题推理:作者之所以提及新鲜咖啡,是借此例来说明一些成分复杂的物质很难令人满意地合成出来。所以选项A为答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3321922.html
相关试题推荐
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
With2005fastbecoming"theyearofthenaturaldisaster",itistimetor
Thefirstrecordeduseofnaturalgastolightstreetlampsitwasinthetowno
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
Naturalflavoringsandfragrancesareoftencostlyandlimitedinsupply.Fo
随机试题
()删除文件()移动光标至右边一字符[br]()移动光标至屏幕右下端(
Whenamagazineforhighschoolstudentsaskeditsreaderswhatlifewouldb
Highereducationhasaresponsibilitytoprovideaworkforcewiththedesign
下列关于人乳和牛乳中矿物质的比较,正确的有( )。A.牛乳中的钙含量比人乳低
A.高渗盐水试验 B.可的松水试验 C.胰高血糖素激发试验 D.血清总T测
患者女,32岁,患急性再生障碍性贫血入院,给予丙酸睾酮治疗,应定期检查A.肝功能
根据下列材料回答问题 20081-8月,公路客运量比上年同期增长A.6
下列费用中,应计入建设工程项目投资中“生产准备费”的有()。A.生产职工培训费
安全阀的出口管道应接向安全地点,安全阀安装应满足()。A.垂直安装 B.倾角
病例摘要:患者,男性,58岁,干部,高血压史多年,不规则服药,因由半身偏瘫麻木1
最新回复
(
0
)