S*********g
发帖数: 24893 | 1 熬鸡汤的时候，加一些盐，味道会更加鲜美。这是因为鸡肉当中富含谷氨酸这种氨基酸
，您又放了一些氯化钠盐进去，便在不知不觉当中就制造了谷氨酸钠，也就是味精。
人的味觉器官当中，有一个专门的氨基酸受体。我们知道，味精叫做谷氨酸钠，是一种
氨基酸盐，当它被用于菜肴而被人们食用的时候，就会刺激位于我们舌部味蕾上的氨基
酸受体，这样我们就可以感到可口的鲜味了。
我们都知道蔬菜当中富含多种维生素，非常有营养，但是还有很多人只喜欢吃肉，不喜
欢吃菜，甚至有人没有肉连饭都吃不下去，时间长了就会造成厌食和偏食。为什么呢？
这是因为肉中富含谷氨酸，味道较重，而蔬菜就比较素淡，所以，肉吃多了，谁愿意再
去吃淡而无味的蔬菜呢。因此，我们在炒菜的时候，稍微放一些味精，就可以使蔬菜的
味道更好，使人们更愿意吃它，从而抑制厌食症与偏食症的发生。中国的药膳学认为，
味精可以增进食欲，改善体质，也是这个道理。 | c***p
发帖数: 27645 | 2 现在我都尽量跳过此类文章，看多了容易混乱崩溃
不过坑王挖的还是来捧个场 | F***I
发帖数: 4170 | 3 坑王 needs to go back to his high school chemistry teacher and repeats his
chemistry course. | F***I
发帖数: 4170 | 4 Monosodium glutamate
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the chemical compound. For its use in food, see
glutamic acid (flavor). For glutamic acid in general, see glutamic acid.
Monosodium glutamate
Chemical composition of monosodium glutamate
Structure of monosodium glutamate
Crystalline monosodium glutamate
IUPAC name[hide]
Sodium 2-Aminopentanedioate
Identifiers
CAS number 142-47-2 Yes
PubChem 85314
ChemSpider 76943 Yes
UNII C3C196L9FG Yes
EC-number 205-538-1
Jmol-3D images Image 1
SMILES
[show]
InChI
[show]
Properties
Molecular formula C5H8NO4Na
Molar mass 169.111 g/mol
Appearance white crystalline powder
Melting point
232 °C, 505 K, 450 °F
Solubility in water 74g/100mL
Hazards
NFPA 704
NFPA 704.svg
0
0
0
LD50 16600 mg/kg (oral, rat)
Yes (verify) (what is: Yes/?)
Except where noted otherwise, data are given for materials in their standard
state (at 25 °C, 100 kPa)
Infobox references
Monosodium glutamate, also known as sodium glutamate or MSG, is the sodium
salt of glutamic acid, one of the most abundant naturally occurring non-
essential amino acids.[1] It was classified by the U.S. Food and Drug
Administration as generally recognized as safe (GRAS) and by the European
Union as a food additive. MSG has the HS code 29224220 and the E number E621
.[2] The glutamate of MSG confers the same umami taste of glutamate from
other foods, being chemically identical.[3] Industrial food manufacturers
market and use MSG as a flavor enhancer because it balances, blends and
rounds the total perception of other tastes.[4][5] Trade names of monosodium
glutamate include Ac'cent, Aji-No-Moto, and Vetsin.
Contents
1 History
2 Usage
3 Safety
3.1 Australia and New Zealand
3.2 United States
4 Production and chemical properties
5 See also
6 References
7 External links
History
Professor Kikunae Ikeda from the Tokyo Imperial University isolated glutamic
acid as a new taste substance in 1908 from the seaweed Laminaria japonica,
kombu, by aqueous extraction and crystallization, and named its taste "umami
".[6] He noticed that the Japanese broth of katsuobushi and kombu had a
peculiar taste that had not been scientifically described at that time and
differed from sweet, salty, sour and bitter.[6] To verify that ionized
glutamate was responsible for the umami taste, Professor Ikeda studied the
taste properties of many glutamate salts such as calcium, potassium,
ammonium, and magnesium glutamate. All salts elicited umami in addition to a
certain metallic taste due to the other minerals. Among those salts, sodium
glutamate was the most soluble and palatable, and crystallized easily.
Professor Ikeda named this product monosodium glutamate and submitted a
patent to produce MSG.[7] Suzuki brothers started the commercial production
of MSG in 1909 as Aji-no-moto, meaning "essence of taste" in Japanese, the
first time that monosodium glutamate was produced in the world.[8][9][10]
Usage
Pure MSG does not have a pleasant taste until it is combined with a
consonant savory smell.[11] As a flavor and in the right amount, MSG can
enhance other taste-active compounds, improving the overall taste of certain
foods. MSG mixes well with meat, fish, poultry, many vegetables, sauces,
soups, and marinades. Since MSG mixes well with many foods, it can also
increase the overall preference of certain foods like beef consommé.[4] But
like other basic tastes, except sucrose, MSG improves the pleasantness only
in the right concentration: an excess of MSG is unpleasant. The optimum
concentration varies with the type of food; in clear soup, the pleasantness
score rapidly falls with more than 1 g of MSG per 100 ml.[12] There is also
an interaction between MSG and salt (sodium chloride), and other umami
substances such as nucleotides. With these properties, MSG can be used to
reduce salt intake (sodium), which predisposes to hypertension, heart
diseases and stroke.[13] The taste of low-salt foods improves with MSG even
with a 30% salt reduction. The sodium content (in mass percent) of MSG is
roughly 3 times lower (12%) than in sodium chloride (39%).[14] Other salts
of glutamate have been used in low-salt soups, but with a lower palatability
than MSG.[15]
Safety
See also: Safety of glutamic acid as a flavor enhancer
MSG has been used for more than 100 years to season food. During this period
, extensive studies were conducted to elucidate the role, benefits and
safety of MSG. At this point, international and national bodies for the
safety of food additives consider MSG safe for human consumption as a flavor
enhancer.[16] The "MSG symptom complex" was originally termed as the "
Chinese Restaurant Syndrome" when Robert Ho Man Kwok anecdotally reported
the symptoms he felt after an American-Chinese meal. Kwok suggested multiple
reasons behind the symptoms, including alcohol from cooking with wine, the
sodium content, or the MSG seasoning. But MSG became the focus and the
symptoms have been associated with MSG ever since. The effect of wine or
salt content was never studied.[17] With the years, the list of non-specific
symptoms has grown on anecdotal grounds. In normal conditions, humans have
the ability to metabolize glutamate that has a very low acute toxicity. The
oral lethal dose to 50% of subjects (LD50) is between 15 to 18 g/kg body
weight in rats and mice respectively, five times greater than the LD50 of
salt (3 g/kg in rats). Therefore, the intake of MSG as a food additive and
the natural level of glutamic acid in foods do not represent a toxicological
concern in humans.[16]
A report from the Federation of American Societies for Experimental Biology
(FASEB) compiled in 1995 on behalf of the United States Food and Drug
Administration (FDA) concluded that MSG is safe when "eaten at customary
levels" and although there seems to be a subgroup of apparently healthy
individuals that respond with the MSG symptom complex when exposed to 3 g of
MSG in the absence of food, causality by MSG has not been established
because the list of MSG Symptom complex was based on testimonial reports.[18
] This report also indicates that there is no data to support the role of
glutamate in chronic and debilitating illnesses. A controlled double-blind
multicenter clinical trial failed to demonstrate the relationship between
MSG symptom complex and the consumption of MSG in individuals that believed
to react adversely against MSG. No statistical association has been
demonstrated, there were few responses and they were inconsistent. Symptoms
were not observed when MSG was given with food.[19][20][21][22]
Adequately controlling for experimental bias includes a double-blind placebo
-controlled experimental design (DBPC) and the application in capsules
because of the strong and unique after-taste of glutamates.[20] In a study
performed by Tarasoff and Kelly (1993) 71 fasting participants were given 5
g of MSG and then administered a standard breakfast. There was only one
reaction, and it was to the placebo in a self-identified MSG-sensitive
individual.[17] In a different study done by Geha et al. (2000), they tested
the reaction of 130 subjects that reported sensitivity to MSG. Multiple
DBPC trials were performed and only subjects with at least two symptoms
proceeded. Only two people out of the whole study responded in all four
challenges. Because of this low prevalence, the researchers concluded that
the response to MSG was not reproducible.[23]
Additional studies that have looked into whether MSG causes obesity have
given mixed results.[24][25] There have been several studies investigating
an anecdotal link between MSG and asthma; current evidence does not support
any causal association.[26]
Since glutamates are important neurotransmitters in the human brain, playing
a key element in learning and memory, there is ongoing study by
neurologists about possible side-effects of MSG in food but no conclusive
studies drawing any connections.[27]
Australia and New Zealand
Food Standards Australia New Zealand[28] (FSANZ) cites "overwhelming
evidence from a large number of scientific studies" to explicitly deny any
link between MSG and "serious adverse reactions" or "long-lasting effects",
declaring MSG "safe for the general population". It does, however, describe
that in less than 1% of the population, sensitive individuals may experience
"transient" side effects such as "headache, numbness/tingling, flushing,
muscle tightness, and generalised weakness" to a large amount of MSG taken
in a single meal. People who consider themselves sensitive to MSG are
encouraged to confirm this through an appropriate clinical assessment.
Standard 1.2.4 of the Australia and New Zealand Food Standards Code requires
the presence of MSG as a food additive to be labeled in packaged foods. The
label must bear the food additive class name (e.g., flavour enhancer),
followed by either the name of the food additive, MSG or its International
Numbering System (INS) number, 621.[29]
United States
Monosodium glutamate (MSG) is one of several forms of glutamic acid found in
foods, in large part because glutamic acid, being an amino acid, is
pervasive in nature. Glutamic acid and its salts can be present in a wide
variety of other additives, including hydrolyzed vegetable protein,
autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, and protein
isolate, which must be labeled with these common and usual names. Since 1998
, MSG cannot be included in the term "spices and flavorings". The food
additives disodium inosinate and disodium guanylate, which are
ribonucleotides, are usually used in synergy with monosodium glutamate-
containing ingredients. However, the term "natural flavor" is used by the
food industry when using glutamic acid (which is similar to MSG, lacking
only the sodium ions). Because of lack of FDA regulation, it is impossible
to determine what percentage of "natural flavor" is actually glutamic acid.[
citation needed]
The FDA considers labels such as "No MSG" or "No Added MSG" to be misleading
if the food contains ingredients that are sources of free glutamate, such
as hydrolyzed protein. In 1993, the FDA proposed adding the phrase "contains
glutamate" to the common or usual names of certain protein hydrolysates
that contain substantial amounts of glutamate.
Production and chemical properties
Since MSG was released into the market, it has been produced by three
methods: hydrolysis of vegetable proteins with hydrochloric acid to disrupt
peptide bonds (1909–1962), direct chemical synthesis with acrylonitrile (
1962–1973), and bacterial fermentation: the current method.[8]
Initially, wheat gluten was used for hydrolysis because it contains more
than 30 g of glutamate and glutamine in 100 g of protein. But as the
production to achieve the ever-increasing demand for MSG augmented, new
production processes were studied: chemical synthesis and fermentation. The
polyacrylic fiber industry began in Japan in the mid 1950s and acrylonitrile
was adopted then as starting material to synthesize MSG.[30]
Currently, most of the world production of MSG is by bacterial fermentation
in a process similar to wine, vinegar, yogurt and even chocolate. Sodium is
added later through the steps of neutralization. During fermentation,
selected bacteria (coryneform bacteria) cultured with ammonia and
carbohydrates from sugar beets, sugar cane, tapioca or molasses, excrete
amino acids into the culture broth from where L-glutamate is isolated. Kyowa
Hakko Kogyo Co Ltd developed the first industrial fermentation to produce L
-glutamate.[31] Nowadays, the conversion yield and production rate from
sugars to glutamate continues to improve in the industrial production of MSG
, which allows for keeping up with demand.[8] The final product after
filtration, concentration, acidification and crystallization is pure
glutamate, sodium and water. It appears as a white, odorless crystalline
powder that in solution dissociates into glutamate and sodium. It is freely
soluble in water but not hygroscopic and practically insoluble in common
organic solvents such as ether.[32] In general, MSG is stable under the
conditions of regular food processing. During cooking, MSG does not
decompose: Like other amino acids, browning or Maillard reactions will occur
in the presence of sugars at very high temperatures.[9] | z*********n
发帖数: 94654 | 5 精彩，刺激，好文！
【在 F***I 的大作中提到】
: Monosodium glutamate
: From Wikipedia, the free encyclopedia
: Jump to: navigation, search
: This article is about the chemical compound. For its use in food, see
: glutamic acid (flavor). For glutamic acid in general, see glutamic acid.
: Monosodium glutamate
: Chemical composition of monosodium glutamate
: Structure of monosodium glutamate
: Crystalline monosodium glutamate
: IUPAC name[hide]
| c***p
发帖数: 27645 | 6 好多字不认识，汗！
【在 F***I 的大作中提到】
: Monosodium glutamate
: From Wikipedia, the free encyclopedia
: Jump to: navigation, search
: This article is about the chemical compound. For its use in food, see
: glutamic acid (flavor). For glutamic acid in general, see glutamic acid.
: Monosodium glutamate
: Chemical composition of monosodium glutamate
: Structure of monosodium glutamate
: Crystalline monosodium glutamate
: IUPAC name[hide]
| y*****8
发帖数: 18140 | 7 同意
味精肯定没有在国内的人吃得多的，国内上亿人不也活得好好的。
【在 c***p 的大作中提到】
: 现在我都尽量跳过此类文章，看多了容易混乱崩溃
: 不过坑王挖的还是来捧个场
| w********r
发帖数: 8704 | 8 哦。。。
【在 S*********g 的大作中提到】
: 熬鸡汤的时候，加一些盐，味道会更加鲜美。这是因为鸡肉当中富含谷氨酸这种氨基酸
: ，您又放了一些氯化钠盐进去，便在不知不觉当中就制造了谷氨酸钠，也就是味精。
: 人的味觉器官当中，有一个专门的氨基酸受体。我们知道，味精叫做谷氨酸钠，是一种
: 氨基酸盐，当它被用于菜肴而被人们食用的时候，就会刺激位于我们舌部味蕾上的氨基
: 酸受体，这样我们就可以感到可口的鲜味了。
: 我们都知道蔬菜当中富含多种维生素，非常有营养，但是还有很多人只喜欢吃肉，不喜
: 欢吃菜，甚至有人没有肉连饭都吃不下去，时间长了就会造成厌食和偏食。为什么呢？
: 这是因为肉中富含谷氨酸，味道较重，而蔬菜就比较素淡，所以，肉吃多了，谁愿意再
: 去吃淡而无味的蔬菜呢。因此，我们在炒菜的时候，稍微放一些味精，就可以使蔬菜的
: 味道更好，使人们更愿意吃它，从而抑制厌食症与偏食症的发生。中国的药膳学认为，
| l*****1
发帖数: 3650 | 9 蘑菇、虾皮虾米等也都很鲜，弄一点炒青菜，青菜就好吃多了。 | S*********g
发帖数: 24893 | 10 1908年，池田菊苗教授採用水提取和結晶的方法，從海帶（昆布(kombu)，一種海草）
中分離出谷氨酸，一種新型的調味品，並將其味道命名為umami（鮮味）。[6]他注意到
乾鰹魚削片|日本木魚和海帶的魚湯均具有一種特別的滋味，而當時他並未對這種味道
進行過任何科學描述，而且這種味道與甜味、鹹味、酸味和苦味截然不同。 [3]為了證
實是因電離化谷氨酸鹽而產生了這種鮮味，池田教授研究了許多關於谷氨酸鹽的味覺特
性，當中包括鈣、鉀、銨和鎂的谷氨酸鹽。除了其他礦物質所產生的某種金屬味道外，
所有的鹽均會形成這種鮮味。在這些鹽中，谷氨酸鈉可溶性最好，味道最佳，兼且易於
結晶。池田教授將這種產物命名為谷氨酸鈉，並為生產MSG申請專利。[7][3]1909年，
鈴木兄弟開始了商業化生產MSG，名稱為味之素（AJI-NO-MOTO），意即日本風味之精華
，這也是世界上首次製成谷氨酸鈉。[ | S*********g
发帖数: 24893 | 11 医学上谷氨酸主要用于治疗肝性昏迷，还用于改善儿童智力发育。食品工业上，味精是
常用的仪器增鲜剂，其主要成分是谷氨酸钠盐。过去生产味精主要用小麦面筋（谷蛋白
）水解法进行，现改用微生物发酵法来进行大规模生产。
谷氨酸是生物机体内氮代谢的基本氨基酸之一，在代谢上具有重要意义。L－谷氨酸是
蛋白质的主要构成成分，谷氨酸盐在自然界普遍存在的。多种食品以及人体内都含有谷
氨酸盐，它即是蛋白质或肽的结构氨基酸之一，又是游离氨基酸，L型氨基酸美味较浓
。
1987年2月16日至25日，在荷兰海牙的联合国粮农组织和世界卫生组织食品添加剂专家
联合委员会第19次会议上，根据对味精各种毒理性实验的综合评价结果作出了结论，即
味精作为风味增强剂，食用是安全的，宣布取消对味精的食用限量，确认了味精是一种
安全可靠的食品添加剂。就营养价值而言，味精是谷氨酸的单钠盐，谷氨酸是构成蛋白
质的氨基酸之一，是人体和动物的重要营养物质，具有特殊的生理作用。 | g*********o
发帖数: 20357 | 12 屁胡！
【在 c***p 的大作中提到】
: 好多字不认识，汗！
| g*********o
发帖数: 20357 | 13 请问第37句话什么意思？谢谢。
【在 z*********n 的大作中提到】
: 精彩，刺激，好文！
|
|
