công dụng của vitamin c

THE PRODUCTION OF VITAMIN C 1 Chemical structure The official chemical designation for vitamin C is ascorbic acid.. 2 Production Vitamin C has been produced commercially by extract

TRƯỜNG ĐẠI HỌC CÔNG NGHỆ SÀI GÒN KHOA CÔNG NGHỆ THỰC PHẨM Môn: Anh Văn Chuyên Ngành 2

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PRESENTATION:

GVHD: TS LE QUANG TRI

SVTH: PHAM DUONG DAN

NGUYEN THANH THAO

I INTRODUCTION

 Humans, in common with other primates, guinea pigs, and fruit-eating bats, rely on their diet to provide vitamin C in the form of ascorbic acid.

 Vitamin C is a water-soluble vitamin, meaning that your body doesn't store it You have to get what you need from food, including citrus fruits, broccoli, and tomatoes.

 Ascorbic acid is generally regarded as being nontoxic, although excessive daily amounts can cause an increased production of oxalic acid in some individuals, leading to an increased risk of kidney stone formation

 Ascorbic acid is used extensively in food technology as a stabilizer for the processing of beverages, wines, and meat products Ascorbyl palmitate is

a stable, fat-soluble form of the vitamin which does not occur in nature.

 Excellent sources of vitamin C include oranges, green peppers,

watermelon, papaya, grapefruit, cantaloupe, strawberries, kiwi, mango, broccoli, tomatoes, Brussels sprouts, cauliflower, cabbage, and citrus juices or juices fortified with vitamin C Raw and cooked leafy greens (turnip greens, spinach), red and green peppers, canned and fresh

tomatoes, potatoes, winter squash, raspberries, blueberries, cranberries, and pineapple are also rich sources of vitamin C Vitamin C is sensitive to light, air, and heat, so you'll get the most vitamin C if you eat fruits and vegetables raw or lightly cooked.

II THE PRODUCTION OF VITAMIN C

1) Chemical structure

The official chemical designation for vitamin C is ascorbic acid It was discovered in 1912 and first isolated in lemons in 1933 Its chemical structure, which was determined in 1933, is shown below

2) Production

Vitamin C has been produced commercially by extraction from plants, by chemical synthesis, by fermentation and by mixed fermentation/chemical synthesis methods (Fermentation is a chemical reaction in which a micro-organism or enzyme causes an organic compound to split into simpler substances.) The manufacture of vitamin C is now carried out in two ways.2 Figure 1 shows the main steps in the two processes

In the first step of both the traditional Reichstein process and the newer two-stage fermentation process, sorbitol is oxidized into sorbose by fermentation All producers use the same micro-organism for this fermentation (Sorbitol itself is made by reducing glucose at high temperature.) Neither the Reichstein process, nor the two-stage fermentation process, involves the use of genetically modified organisms (GMOs)

a Reichstein process

The Reichstein process is a mixed fermentation/chemical synthesis method It was first used in 1933 and is still employed by Roche, BASF and Takeda In it, sorbose is transformed into di-acetone- ketogulonic acid (DAKS) in a two-stage chemical process The first step involves a reaction with acetone This produces di-acetone sorbose, which is then oxidized using chlorine and sodium hydroxide

to produce DAKS

In the next step, DAKS is dissolved in a mix of organic solvents and its structure is rearranged to form vitamin C, using an acid catalyst (This stage of the process is similar in the two-stage fermentation process.) In the last production step, the crude vitamin C is purified by recrystallization (This step is identical for both

processes.)

Many technical and chemical modifications have been made to the Reichstein process to optimize and shorten the various reaction routes Consequently, each step now has a yield of over 90 per cent The overall yield of vitamin C from glucose is about 60 per cent

Various stages of the Reichstein process use considerable quantities of organic and inorganic solvents and reagents These include acetone, sulphuric acid and sodium hydroxide Although some of these compounds can be recycled, stringent environmental control is required, resulting in significant

waste disposal costs.

b Two-stage fermentation process

The newer of the two main production processes was developed in China and is used by all Chinese producers The use of the process has also been licensed to a number of Western manufacturers, including Roche and a joint venture involving BASF and Merck It has lower fixed and capital costs,

resulting in an overall production cost saving of about a third compared with the Reichstein method

In the two-stage fermentation process, a second fermentation step replaces

the chemical reactions used to produce DAKS in the Reichstein method This fermentation results in a different intermediate product, KGA All producers use the same micro-organism

Two chemical steps similar to the final stages of the Reichstein process then complete the synthesis of vitamin C

Compared with the Reichstein process, the two-stage fermentation process makes less use of toxic solvents and reagents There is, therefore, a reduction in the cost of processing waste products.

3) Forms of vitamin C produced

Many raw vitamins can be unstable if affected by temperature, light, acidity

or alkalinity To prevent degradation in use, these vitamins may be combined with other products or, alternatively, various chemical derivatives of the vitamins may be produced

Producers market vitamin C in various forms These include powder and granular forms, different purity levels, and chemical derivatives such as sodium ascorbate and calcium ascorbate BASF said that sodium ascorbate was preferred as an antioxidant as it would not discolour meat; in other respects it was almost identical in its biochemical properties to ascorbic acid Calcium ascorbate is also commonly produced for use as a combined source of calcium and vitamin C in supplements

BASF's range of vitamin C products includes ascorbic acid in three particle sizes, sodium ascorbate, and calcium ascorbyl-monophosphate, a product for the feed industry designed to resist severe heat and pressure treatments It does not produce a DC grade of vitamin C for use in tablets

We were also told about some other minor speciality vitamin C products These included stay-C, a low-solubility product made by Roche, which is

suitable for use in fish feeds Roche said that BASF had an equivalent product for the fish farming industry, but Takeda did not

III CONSUME

IV.

body It helps the body make collagen, an important protein used to make skin,

cartilage, tendons, ligaments, and blood vessels Vitamin C is needed for healing wounds, and for repairing and maintaining bones and teeth It also helps the body absorb iron from nonheme sources

many people may have low levels of vitamin C Smoking cigarettes lowers the amount of vitamin C in the body, so smokers are at a higher risk of deficiency

including high blood pressure, gallbladder disease, stroke, some cancers, and atherosclerosis, the build up of plaque in blood vessels that can lead to heart attack and stroke Getting enough vitamin C from your diet by eating lots of fruit and vegetables may help reduce the risk of developing some of these conditions There is no conclusive evidence that taking vitamin C supplements will help or prevent any of these conditions

preventing heart attack or stroke are mixed Vitamin C doesn't lower cholesterol levels or reduce the overall risk of heart attack, but evidence suggests it may help protect arteries against damage

slow down the progression of atherosclerosis (hardening of the arteries) It helps prevent damage to LDL ("bad") cholesterol, which then builds up as plaque in the arteries and can cause heart attack or stroke Other studies suggest that vitamin C may help keep arteries flexible

more likely to have a heart attack, stroke, or peripheral artery disease, all potential results of having atherosclerosis

Peripheral artery disease is the term used to describe atherosclerosis of the blood vessels to the legs This can lead to pain when walking, known as intermittent claudication But there is no evidence that taking vitamin C supplements will help

That way, you also get the benefit of other antioxidants and nutrients contained in food If you have low levels of vitamin C and have trouble getting enough through the foods you eat, ask your doctor about taking a supplement

 Population-based studies (which involve observing large

groups of people over time) suggest that people who eat foods rich in antioxidants, including vitamin C, have a lower risk of high blood pressure than people who have poorer diets Eating foods rich in vitamin C is important for your overall health, especially if you are at risk for high blood pressure The diet physicians most frequently recommend for treatment and prevention of high blood pressure, known as the DASH

(Dietary Approaches to Stop Hypertension) diet, includes lots

of fruits and vegetables, which are loaded with antioxidants

cold, scientific evidence doesn't support that theory Taking vitamin C supplements regularly (not just at the beginning of a cold) produces only a small reduction in the duration of a cold (about 1 day) The only other piece of evidence supporting vitamin C for preventing colds comes from studies examining people exercising in extreme environments (athletes, such as skiers and marathon runners, and soldiers in the Arctic) In these studies, vitamin C did seem to reduce the risk of getting a cold

foods rich in vitamin C may be associated with lower rates of cancer, including skin cancer, cervical dysplasia (changes to the cervix which may be cancerous or precancerous, picked up

by pap smear), and, possibly, breast cancer But these foods also contain many beneficial nutrients and antioxidants, not only vitamin C, so it's impossible to say for certain that vitamin

C protects against cancer Taking vitamin C supplements, on the other hand, has not been shown to have any helpful effect

vitamin C once diagnosed with cancer will help your treatment

In fact, some doctors are concerned that large doses of

antioxidants from supplements could interfere with

chemotherapy medications More research is needed If you are

undergoing chemotherapy, talk to your doctor before taking vitamin C or any supplement

part of normal cartilage Cartilage is destroyed in osteoarthritis (OA), putting pressure on bones and joints In addition, some researchers think free radicals molecules produced by the body that can damage cells and DNA may also be involved

in the destruction of cartilage Antioxidants such as vitamin C appear to limit the damage caused by free radicals However,

no evidence suggests that taking vitamin C supplements will help treat or prevent OA What the evidence does show is that people who eat diets rich in vitamin C are less likely to be diagnosed with arthritis

levels of vitamin C If you take these drugs regularly for OA, you might want to take a vitamin C supplement

including zinc (80 mg), beta-carotene (15 mg), and vitamin E (400 IU) to protect the eyes against developing macular

degeneration (AMD), the leading cause of legal blindness in people over 55 in the United States The people who seem to benefit are those with advanced AMD It isn't known whether this combination of nutrients helps prevent AMD or is

beneficial for people with less advanced AMD This

combination includes a high dose of zinc, which you should only take under a doctor’s supervision

E may help prevent pre-eclampsia in women who are at high risk Pre-eclampsia, characterized by high blood pressure and too much protein in the urine, is a common cause of premature births Not all studies agree, however

 Studies are mixed when it comes to the effect of vitamin C on asthma Some show that low levels of vitamin C are more common in people with asthma, leading some researchers to think that low levels of vitamin C might increase the risk for this condition Other studies seem to show that vitamin C may help reduce symptoms of exercise-induced asthma

Although the information is limited, studies suggest that vitamin C may also be helpful for:

middle part of the eye)

and hay fever (called allergic rhinitis)

(called erythema)