Fructooligosaccharide (FOS), also known as fructooligosaccharide or sucrose oligosaccharide, has the molecular formula of G-F-Fn, n = 1 ~ 3 (where G is glucose group and F is fructosyl group), and is prepared from sucrose and 1 ~ 3 fructosyl groups through β 2, 1 bond. Their molecular formulas and relative molecular weights are shown in table 1.
Bacon and Edelman, Blanchard and Albon independently found that invertase not only has hydrolysis function, but also has transfer function in 1950. When sucrose is hydrolyzed, different amounts of glucose and fructose will be produced. In addition, some oligosaccharides are produced. The structures of these oligosaccharides have been further determined and named as fructotriose oligosaccharides. In 1952, Huali et al. used yeast invertase to act on sucrose, and obtained sucrose for the first time. The following year, Bacon and Bell acted on sucrose with peak amylase to produce a series of oligosaccharides, from which isomaltulose was separated. In 1954, Gross et al. precipitated neocosose from it.
Later, it was found that fructooligosaccharides naturally existed in various plants (see Table 2), and were also found in daily foods such as bananas, garlic, honey, onions, brown sugar, asparagus roots, artichokes and wheat. In 1990, NET (national environmental inspection agency) evaluated the content of fructooligosaccharides in some foods, and estimated the daily consumption of fructooligosaccharides according to the content of these foods and people's daily consumption (see table 3), in which the annual consumption per capita comes from the data published by the food safety evaluation system of the Environmental Protection Agency (EPA), and the moisture content comes from the annual consumption of adults weighing 58.9kg. Based on these data, it was calculated that.
I. Chemical Structure of Fructooligosaccharides
Fructooligosaccharides
Fructooligosaccharide (FOS), also known as fructooligosaccharide or sucrose oligosaccharide, has the molecular formula of G-F-Fn, n = 1 ~ 3 (where G is glucose group and F is fructosyl group), and is prepared from sucrose and 1 ~ 3 fructosyl groups through β 2, 1 bond. Their molecular formulas and relative molecular weights are shown in table 1.
Bacon and Edelman, Blanchard and Albon independently found that invertase not only has hydrolysis function, but also has transfer function in 1950. When sucrose is hydrolyzed, different amounts of glucose and fructose will be produced. In addition, some oligosaccharides are produced. The structures of these oligosaccharides have been further determined and named as fructotriose oligosaccharides. In 1952, Huali et al. used yeast invertase to act on sucrose, and obtained sucrose for the first time. The following year, Bacon and Bell acted on sucrose with peak amylase to produce a series of oligosaccharides, from which isomaltulose was separated. In 1954, Gross et al. precipitated neocosose from it.
Later, it was found that fructooligosaccharides naturally existed in various plants (see Table 2), and were also found in daily foods such as bananas, garlic, honey, onions, brown sugar, asparagus roots, artichokes and wheat. In 1990, NET (national environmental inspection agency) evaluated the content of fructooligosaccharides in some foods, and estimated the daily consumption of fructooligosaccharides according to the content of these foods and people's daily consumption (see table 3), in which the annual consumption per capita comes from the data published by the food safety evaluation system of the Environmental Protection Agency (EPA), and the moisture content comes from the annual consumption of adults weighing 58.9kg. Based on these data, it was calculated that.
I. Chemical Structure of Fructooligosaccharides
5. Heat resistance
The thermal stability of fructooligosaccharides is quite good, and it is stable when heated to 140℃ under neutral conditions, as shown in Figure 6.
6, the relationship between acidity and thermal stability
Fructooligosaccharides have good thermal stability in neutral or near-neutral environment. When it is in an acidic environment with a pH below 4, it depends on the temperature. It is easy to decompose at high temperature and has little effect at low temperature. Its thermal stability and stability in yogurt are shown in Figure 7 and Table 5 respectively.
Note: Guangming brand yogurt, storage temperature 4℃.
7. Preservation stability
The stability of 12% fructooligosaccharide under acidic conditions of -25℃ to 40℃ for 3 months is shown in Figure 8. As can be seen from the figure, 12% syrup is also very stable at 20℃, pH3 and pH4 for 3 months.
3. Evaluation of functional characteristics of fructooligosaccharides
Studies have shown that fructooligosaccharides have different digestive processes and metabolic pathways from ordinary sugar, and have many physiological functions.
(a) Digestive and metabolic characteristics
Fructooligosaccharides can not be decomposed by various digestive enzymes after entering the human digestive system through the oral cavity, so they can not be absorbed through the stomach and small intestine and enter the large intestine almost unaffected. Fructooligosaccharides can be selectively utilized by beneficial bacteria such as Bifidobacterium and Lactobacillus in large intestine, so that they can multiply rapidly and massively. At the same time, bifidobacteria ferment fructooligosaccharides, and some of them are converted into short-chain fatty acids and a small amount of gas. Among them, about 40% of fructooligosaccharides are secreted by bacteria, 65,438+00% are converted into CO2, H2, CH4 and other gases, and nearly 50% are converted into acetic acid, propionic acid, butyric acid and lactic acid. Some short-chain fatty acids are absorbed by colonic mucosa, and then enter the liver, where they are further metabolized into energy that can be absorbed by consumers, but their energy value is very low, accounting for only 1/3 of sucrose energy.
Fructooligosaccharides have the following two characteristics during digestion:
On the one hand, it is a kind of indigestible sugar with the same characteristics as water-soluble dietary fiber. According to the blood sugar load test of several healthy people and diabetic patients, the blood sugar value and insulin value did not increase after taking fructooligosaccharides for 3 hours, thus determining the indigestibility of fructooligosaccharides. By the end of 1998, the Japanese Ministry of Health and Welfare had approved 108 kinds of health foods in more than seven years, among which 77 kinds claimed to use indigestible oligosaccharides and dietary fiber to maintain gastrointestinal function, accounting for 7 1.3% of the total number of health foods. It can be seen that fructooligosaccharides, as health food, have a high status in advanced developed countries.
On the other hand, in the large intestine, it can promote the reproduction and growth of a few beneficial bacteria such as Bifidobacterium, and at the same time significantly inhibit the reproduction of harmful bacteria, thus realizing the biphasic regulation of human microecology. Fructooligosaccharide is a typical bifidus factor in natural functional foods that are not easy to digest, which completely meets the standards of prebiotics (substances that can improve the composition and quantity of dominant bacteria in the intestine and are beneficial to the health of the host).
1998165438+10/5 at the international symposium on health food held by the Ministry of Health in Beijing, Dr. Fergus M. Clydesdale pointed out that Robert Fred put forward a quite new concept of "prebiotics" in 1995. Because of the selective and suitable substrate, these bacteria have reproductive advantages over other bacteria, so the composition of colon microbial flora has changed greatly after people eat food containing prebiotics.
(2) Physiological function
Fructooligosaccharides, as a representative of prebiotics, have the physiological function of regulating the two-phase microecological balance.
On June 8th, 1992, Japan Health Food Association made a comprehensive evaluation on the physiological function of fructooligosaccharides produced by Meiji Sugar Company in Japan. 1On September 29th, 995, the Japanese Ministry of Health and Welfare officially approved fructooligosaccharides produced by Meiji Sugar Company of Japan as specific health food, and confirmed that fructooligosaccharides "have the functions of' regulating intestinal tract, improving intestinal flora, improving stool properties and inhibiting harmful substances in intestinal tract'".
1997 10, Health Food Evaluation Committee of China Ministry of Health, through the human body test of Bifidobacterium fructooligosaccharide, it is proved that this product has the ability of "inhibiting the reproduction of pathogenic bacteria, removing harmful substances in intestinal tract, reducing blood lipid and enhancing immunity". The superior physiological functions of fructooligosaccharides are mainly manifested in the following aspects:
1, improving the function of intestinal flora
Bifidobacterium was first isolated from the feces of healthy breast-fed infants in 1899 by Dr. Tissier of Pasteur Institute in France. After more than 30 years of research, researchers in Japan and other European countries have gradually discovered the beneficial effects of Bifidobacterium on human body, which has become one of the signs to measure the health status and evaluate the functional food to improve the gastrointestinal flora. Fructooligosaccharides can proliferate Bifidobacterium and Lactobacillus, but inhibit or not proliferate Clostridium perfringens, that is, Escherichia coli or enterococcus and Bacteroides do not proliferate or the proliferation range is lower than that of Bifidobacterium or Lactobacillus, so it can be considered that it has a certain function of regulating gastrointestinal flora.
After ingesting functional fructooligosaccharides, the number of bifidobacteria in the intestine can increase by hundreds of times. Bifidobacterium can not only inhibit the reproduction of bacteria, but also reduce or even completely eliminate spoilage bacteria such as Clostridium. When amino acids are segmented, spoilage bacteria will produce harmful substances such as ammonia, amine, hydrogen sulfide, indole and phenol, which is one of the many reasons that cause harm to human health. Fructooligosaccharides can effectively promote the reproduction of Bifidobacterium. Bifidobacterium not only does not produce harmful substances, but also produces organic acids such as acetic acid and lactic acid after metabolism, which can reduce intestinal pH, improve endogenous lysozyme activity and inhibit the reproduction of pathogenic bacteria or spoilage bacteria such as Escherichia coli and Clostridium. In addition, Bifidobacterium can also produce vitamins, such as vitamin B 1, vitamin B2, vitamin B6, folic acid, etc., which play a role in maintaining human health.
2, low sweetness, low calorie
The sweetness of fructooligosaccharides is only 65,438+0/3 of that of sucrose, and it is not decomposed by α-amylase, sucrose invertase and maltase in human body, so it can not be used as energy and will not increase blood sugar. Each gram of fructooligosaccharides contains only 6.3KJ of calories, so it is very suitable for diabetics and obese people.
3. Reduce blood lipids
A large number of human experiments have confirmed that the intake of fructooligosaccharides can reduce the serum cholesterol level. Taking 6 ~ 12g fructooligosaccharides every day for 2 weeks to 3 months can reduce serum total cholesterol by 20 ~ 50mg/dl. Lactic bacteria, including Bifidobacterium and its fermented dairy products, can reduce the level of serum total cholesterol and increase the proportion of high-density lipoprotein cholesterol in female serum.
The decrease of serum cholesterol level is considered to be the result of the change of intestinal microbial flora balance. In vitro experiments also showed that 12 strains of Lactobacillus acidophilus in human intestine could absorb cholesterol, and Lactobacillus acidophilus could inhibit the absorption of cholesterol by small intestinal wall. The ability of Bifidobacterium to metabolize nicotinic acid is also related to the decrease of serum cholesterol level. Bifidobacterium can control the newly formed low density lipoprotein receptor by inhibiting activated T cells in human body, thus reducing serum cholesterol. The experimental results in mice show that Bifidobacterium can control the synthesis of cholesterol by affecting the activity of β-hydroxy-β-methylglutaryl-CoA reductase, thus reducing the serum cholesterol content.
4, moistening the intestines and relaxing the bowels
Commonly used substances with laxative effect include dietary fiber, sugar alcohol, microecological agents and so on. Dietary fiber can not be absorbed by human body, but it can be partially decomposed and fermented by intestinal flora to produce organic acids, reduce intestinal pH value and stimulate intestinal mucosal peristalsis. The food residue formed by undigested dietary fiber can change the characteristics of feces, stimulate colon movement and promote defecation. In addition, water-soluble dietary fiber can be used by bacteria and can keep moisture in feces.
Fructooligosaccharides can not be digested and absorbed in human body, and belong to low molecular weight water-soluble dietary fiber, so they can be used to dilute feces and relieve constipation. Its physiological function is completely derived from its unique fermentation characteristics (Bifidobacterium proliferation characteristics). Fructooligosaccharide is superior to dietary fiber in that its daily demand is small and it will not cause diarrhea within the recommended amount. It has certain sweetness and good sweetness characteristics, is easily soluble in water, does not increase the viscosity of the product, has stable physical properties, and is easy to be added to processed foods and beverages.
5, enhance immunity
A large number of animal experiments show that Bifidobacterium can play an anti-cancer role by breeding in the intestine. This anti-cancer effect is attributed to the cells, cell wall components and extracellular secretions of Bifidobacterium, which improves the immunity of the body. For example, sterile mice fed with Bifidobacterium colonization single factor live longer than untreated sterile mice. Fructooligosaccharides have the function of relaxing bowels, can inhibit intestinal spoilage bacteria, significantly reduce spoilage products and discharge them in time, thus reducing the occurrence of colorectal cancer.
6. Prevention of dental caries
Functional fructooligosaccharides generally have no adverse effects on teeth. Dental caries are mainly caused by oral microorganisms, especially Streptococcus mutans, which use sucrose to produce acids, especially lactic acid and water-insoluble β -glucan Functional fructooligosaccharides can not be the substrate of the above oral microorganisms, and there is no bacterial agglutination, so it will not cause dental caries.
7. Promote the absorption of minerals
Studies have shown that fructooligosaccharides have the ability to intercept mineral elements such as calcium, magnesium, iron and zinc. Fructooligosaccharides cannot be decomposed by digestive enzymes. After reaching the large intestine, fructooligosaccharides are fermented and decomposed by Bifidobacterium, releasing mineral ions. As we all know, the second half of the digestive tract, such as cecum and colon, is an important place to absorb mineral elements. In addition, short-chain fatty acids produced by fermentation of fructooligosaccharides by Bifidobacterium reduce intestinal pH, and in acidic environment, the dissolution rate of many minerals increases, which is beneficial to absorption. Because short-chain fatty acids can stimulate the growth of colon membrane cells and improve the absorption capacity of minerals.
Fourth, safety.
As mentioned above, fructooligosaccharides have functional characteristics beneficial to human body. As a health food or food ingredient, its safety to human body is the key factor for its acceptance and wide use. 65438-0982 The Central Research Institute of Meiji Sugar Company of Japan conducted acute toxicity test, subacute toxicity test and diarrhea test on the safety of fructooligosaccharides. The results showed that fructooligosaccharides were safe as food and food ingredients. In addition, there are many in vivo and in vitro experiments to evaluate the potential toxicity of fructooligosaccharides to animals and humans. The results show that fructooligosaccharides have no side effects, and the only known effect is that eating a large amount of fructooligosaccharides (more than 5% in mouse food) will lead to stool thinning or diarrhea.
Therefore, in Japan, fructooligosaccharides are regarded as a food, not a food additive, and are widely used in many foods, forming a very considerable daily consumption. In Taiwan Province Province, milk, soft drinks and biscuits containing fructooligosaccharides are very common in the health food market. In addition, fructooligosaccharides are also used as feed additives for animals and poultry in America and Japan.
In China, a number of safety toxicological tests of domestic fructooligosaccharides completed by scientific research institutions designated by the Ministry of Health show that fructooligosaccharides are safe and nontoxic. Aspergillus Niger is generally used to produce fructooligosaccharides by enzymatic method, which is a kind of food safety strain. Fructooligosaccharides, as health food or food ingredients, were added to AD calcium milk, lactic acid drinks and wine, and obtained the health food certificate issued by the Ministry of Health.
The application and development direction of verb (abbreviation of verb) products
With the improvement of people's living standards, functional food additives are widely used. Fructooligosaccharide has been widely used in food and other fields because of its excellent physiological activity and health care function. As a component of health food, it can be added to almost all beverages and foods that allow sweetness, thus improving the value of the original food. Many patents report the application of fructooligosaccharides in food and medicine, such as as salmonella inhibitor, low-calorie food and drink, anemia improver and so on. It should be noted that foods with strong acidity (pH < 3 or yeast in some dough can hydrolyze fructooligosaccharides under certain conditions, so be very careful when using fructooligosaccharides in these foods.
Application of (1) in food and health products
Fructooligosaccharides are pure and moderate in sweetness, good in moisture retention and easy to process, and can be widely used in various foods. In Japan, where fructooligosaccharides are widely praised, since 1990, Meiji Company of Japan first introduced fructooligosaccharides to the market, the output of1990 exceeded 4,000 t, and the number of foods added with fructooligosaccharides increased from more than 200 in 1992 to more than 530. For example:
Dairy products: milk drinks, yogurt, lactic acid bacteria drinks, milk powder, etc.
Drinks: coffee, tea drinks, refreshing drinks, soybean milk, alcohol, etc.
Candy and pastry: candy, biscuits, bread, fast food, Japanese and western snacks, jelly, pudding, etc.
Others: health food, processed meat products, processed aquatic products, pickles, tofu, etc.
In China, fructooligosaccharides can not only be sold as health food alone, but also be added to processed foods such as dairy products, candy, jelly, bread, beverages, vinegar, wine and other ingredients, and can also be made into drugs to improve intestinal function. For example, if it is added to more than 50 kinds of foods such as Sanyuan high-bioactivity yogurt, Long Dan Bifidobacterium fresh milk, Sanlu Bifidobacterium milk powder in infant stage, Wahaha calcium milk lactic acid beverage, bamboo leaf green wine and Xizhilang Jianchang jelly, most of them have obtained the health food certificate issued by the Ministry of Health, and bamboo leaf green health wine has also won the national scientific and technological progress award.
(2) Application in animal feed
Fructooligosaccharides can also be used in the field of animal husbandry production. Feeding experiment was carried out by adding fructooligosaccharides to piglet feed. Newly weaned piglets are prone to gastrointestinal indigestion or diarrhea, slow growth and little weight gain. At this time, compared the feed with fructooligosaccharides and the feed without fructooligosaccharides, it was found that the incidence of dysentery was significantly reduced. The amount of ammonia is less than110 of ammonia without fructooligosaccharides, and the odor of p-cresol and feces is also significantly reduced. Fructooligosaccharides have similar effects when used in fish feed, weaned calf feed and dog feed. In June, 2000, the Animal College of Zhejiang University developed a new special feed for bifidus factors-"Diarrhea-free feed", which successfully completed the animal molecular nutrition experiment. Experiments show that FOS can prevent diarrhea and dysentery symptoms of weaned poultry and livestock, and has a positive effect on preventing death, slow growth and stunting caused by FOS.
In 1998, Yin, Nakamura of Japan and others completed the experiment of FOS intake in piglets and calves. Conclusion: Adding 0.375% fructooligosaccharide can enhance the effective absorption of digestive tract of sows, thus shortening the days of estrus again after delivery from 20 days to 1 1 day, increasing the litter size and avoiding the side effects of drug aphrodisiac.
At the beginning of February, 2002, Chengdu Giant Panda Research Base fed a sick giant panda "Lily" with fructooligosaccharides for 20 consecutive days. As a result, the panda's symptoms such as "sticky flow", abdominal pain, anorexia and loose stool have been effectively curbed, and its physical and mental health has been improved, and its appetite and weight have increased significantly. Professor Li Guanghan, director of Chengdu Giant Panda Research Base, said that it will be promising to use FOS to promote the adjustment of various endangered wild rare animals after the balance of micro-ecology in the field changes to the imbalance of artificial reproduction.
Fructooligosaccharide has a broad application prospect in the world because of its pure and refreshing sweetness, various excellent physiological activities, health care functions and good processing characteristics. Consumption data show that with the increase of consumers' interest in low-calorie foods, the consumption of fructooligosaccharides in the market will continue to increase. Although fructooligosaccharides can not replace the wide application of sucrose, they are almost substitutes for sucrose as far as fructooligosaccharides themselves are concerned. In addition, high-purity fructooligosaccharides are also the first choice for diabetic patients, so high-purity fructooligosaccharides also have broad development prospects in China.