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PREBIOTIC EFFECTS OF INULIN AND ACACIA GUM (REVIEW)
Abstract
Prebiotics have great potential as agents to improve or maintain a balanced intestinal microflora to enhance health and wellbeing. They are non-digestible (by the host) food ingredients that have a beneficial effect through their selective metabolism in the intestinal tract. Key to this is the specificity of microbial changes.Thanks to the methodological and fundamental research of microbiologists, enormous progress has been made in understanding the gut microbiota. A large number of human intervention studies have been performed that have demonstrated that dietary consumption of certain food products can result in statistically significant changes in the composition of the gut microbiota in line with the prebiotic concept. The concept prebiotics is to enhance the growth of beneficial bacteria in the lower intestine. There is much interest in increasing the numbers and activities of beneficial bacteria (Bifidobacteria) in the large gut, preferably at the expense of more harmfulbacteria. The focus of this review has been to point out the prebiotic effects (bifidogenic effects) of acacia gum and inulin. Some effects attributed to selected prebiotics have been proved by clinical trials, while others have been acquired on the basis of in vitro tests.
A catalytic methodology for the effective synthesis of pyrazolopyrazole derivatives using a combination of hydrolyzed Arabic gum-g-polyacrylonitrile/ZnFe2O4 (Hyd AG-g-PAN/ZnFe2O4) catalyst, malononitrile, and aromatic aldehyde, hydrazine hydrate, and ethyl acetoacetate is described. This protocol relies on the use of environment-friendly heterogeneous catalyst based on zinc ferrite magnetic particles in combination with Arabic gum (AG) as the backbone, N, N methylene bisacrylamide (MBA) as a crosslinking agent, ammonium persulfate (APS) as an initiator, and alkaline solution for hydrolyzation. This bio-based catalyst with a soft three-dimensional cross-linked framework contains distinct acidic and basic sites and could be applied as a powerful catalyst for the one-pot synthesis of pyranopyrazoles derivatives. Using an external magnet, the superparamagnetic nanocomposite could be easily separated. Furthermore, the catalyst can well be utilized at least six times in subsequent reaction cycles before losing its activity. FT-IR, EDX, TGA, FESEM, VSM, and XRD methods were used to characterize the produced catalyst. Taking 0.01 g of catalyst at 80°C in a green solvent of water/ethanol, the greatest output of dihydropyrano [2,3-c] pyrazole was 96% in 15 minutes. A simple technique, short reaction time, high yield, and the catalyst's reusability and stability are just a few of the study's advantages.
The health benefits of dietary fiber have long been appreciated. Higher intakes of dietary fiber are linked to less cardiovascular disease and fiber plays a role in gut health, with many effective laxatives actually isolated fiber sources. Higher intakes of fiber are linked to lower body weights. Only polysaccharides were included in dietary fiber originally, but more recent definitions have included oligosaccharides as dietary fiber, not based on their chemical measurement as dietary fiber by the accepted total dietary fiber (TDF) method, but on their physiological effects. Inulin, fructo-oligosaccharides, and other oligosaccharides are included as fiber in food labels in the US. Additionally, oligosaccharides are the best known "prebiotics", "a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-bring and health." To date, all known and suspected prebiotics are carbohydrate compounds, primarily oligosaccharides, known to resist digestion in the human small intestine and reach the colon where they are fermented by the gut microflora. Studies have provided evidence that inulin and oligofructose (OF), lactulose, and resistant starch (RS) meet all aspects of the definition, including the stimulation of Bifidobacterium, a beneficial bacterial genus. Other isolated carbohydrates and carbohydrate-containing foods, including galactooligosaccharides (GOS), transgalactooligosaccharides (TOS), polydextrose, wheat dextrin, acacia gum, psyllium, banana, whole grain wheat, and whole grain corn also have prebiotic effects.
Oligofructose and inulin are naturally occurring indigestible carbohydrates. In vitro they selectively stimulate the growth of species of Bifidobacterium, a genus of bacteria considered beneficial to health. This study was designed to determine their effects on the large bowel microflora and colonic function in vivo.
Eight subjects participated in a 45-day study during which they ate controlled diets. For the middle 15 days, 15 g.day-1 oligofructose was substituted for 15 g.day-1 sucrose. Four of these subjects went on to a further period with 15 g.day-1 inulin. Bowel habit, transit time, stool composition, breath H2 and CH4, and the predominant genera of colonic bacteria were measured.
Both oligofructose and inulin significantly increased bifidobacteria from 8.8 to 9.5 log10 g stool-1 and 9.2 to 10.1 log10 g stool-1, respectively, whereas bacteroides, clostridia, and fusobacteria decreased when subjects were fed oligofructose, and gram-positive cocci decreased when subjects were fed inulin. Total bacterial counts were unchanged. Fecal wet and dry matter, nitrogen, and energy excretion increased with both substrates, as did breath H2. Little change in fecal short-chain fatty acids and breath CH4 was observed.
A 15-g.day-1 dietary addition of oligofructose or inulin led to Bifidobacterium becoming the numerically predominant genus in feces. Thus, small changes in diet can alter the balance of colonic bacteria towards a potentially healthier microflora.
Inulin and oligofructose belong to a class of carbohydrates known as fructans. The main sources of inulin and oligofructose that are used in the food industry are chicory and Jerusalem artichoke. Inulin and oligofructose are considered as functional food ingredients since they affect the physiological and biochemical processes in rats and human beings, resulting in better health and reduction in the risk of many diseases. Experimental studies have shown their use as bifidogenic agents, stimulating the immune system of the body, decreasing the pathogenic bacteria in the intestine, relieving constipation, decreasing the risk of osteoporosis by increasing mineral absorption, especially of calcium, reducing the risk of atherosclerosis by lowering the synthesis of triglycerides and fatty acids in the liver and decreasing their level in serum. These fructans modulate the hormonal level of insulin and glucagon, thereby regulating carbohydrate and lipid metabolism by lowering the blood glucose levels; they are also effective in lowering the blood urea and uric acid levels, thereby maintaining the nitrogen balance. Inulin and oligofructose also reduce the incidence of colon cancer. The biochemical basis of these beneficial effects of inulin and oligofructose have been discussed. Oligofructose are non cariogenic as they are not used by Streptococcus mutans to form acids and insoluble glucans that are the main culprits in dental caries. Because of the large number of health promoting functions of inulin and oligofructose, these have wide applications in various types of foods like confectionery, fruit preparations, milk desserts, yogurt and fresh cheese, baked goods, chocolate, ice cream and sauces. Inulin can also be used for the preparation of fructose syrups.
Specific carbohydrates, i.e. prebiotics such as fructo-oligosaccharide (FOS), are not digested in the small intestine but fermented in the colon. Besides beneficial health effects of an enhanced bifidobacteria population, intestinal gas production resulting from fermentation can induce abdominal symptoms. Partial replacement with slowly fermented acacia gum may attenuate side effects. The aim was to compare the effects of FOS with those of a prebiotic mixture (50 % FOS and 50 % acacia gum; BLEND) and a rapidly absorbed carbohydrate (maltodextrin) on general intestinal wellbeing, abdominal comfort and anorectal sensory function. Twenty volunteers (eight male and twelve female; age 20-37 years) completed this double-blind, randomised study with two cycles of a 2-week run-in phase (10 g maltodextrin) followed by 5 weeks of 10 g FOS or BLEND once daily, separated by a 4-week wash-out interval. Abdominal symptoms and general wellbeing were documented by telephone interview or Internet twice weekly. Rectal sensations were assessed by a visual analogue scale during a rectal barostat test after FOS and BLEND treatment. Both FOS and BLEND induced more side effects than maltodextrin. Belching was more pronounced under FOS compared with BLEND (P = 0.09 for females; P = 0.01 for males), and for self-reported general wellbeing strong sex differences were reported (P = 0.002). Urgency scores during rectal barostat were higher with FOS than BLEND (P = 0.01). Faced with a growing range of supplemented food products, consumers may benefit from prebiotic mixtures which cause fewer abdominal side effects. Sex differences must be taken in consideration when food supplements are used.
The present study was undertaken to determine the prebiotic efficacy of gum arabic upon consumption by man for up to 4 weeks and, if any, to establish the dose-effect relationship. Human healthy volunteers consumed various daily doses (5, 10, 20, 40 g) of gum arabic (EmulGold) in water for up to 4 weeks. Daily consumption of water was taken as the negative control and that of 10 g inulin as the positive control. At 0, 1, 2 and 4 weeks quantification of bacterial numbers in stool samples was performed via real time-PCR techniques and questionnaires were filled in to account for potential drawbacks. The genera of Bifidobacteria and Lactobacilli were taken as potentially beneficial bacteria and those of Bacteroides, Clostridium difficile and Enterococci as potentially non-beneficial, this distinction was dependent on the issue of these numbers being or becoming out of balance in the host. Compared with the negative control the numbers of Bifidobacteria and Lactobacilli 4 weeks after consumption were significantly higher for gum arabic: the optimal dose being around 10 g. Moreover, at this dose the numbers of Bifidobacteria, Lactobacilli and Bacteroides were significantly higher for gum arabic than for inulin. No significant drawback was encountered during the study. It is concluded that gum arabic establishes prebiotic efficacy, at least as good as inulin. The optimal daily dose was found to be 10 g.
Interest in consumption of prebiotics and probiotics to improve human gastrointestinal health is increasing. Consumption of beneficial probiotic bacteria combined with oligosaccharides may enhance colonic bacterial composition and improve internal health. The objectives of this article are to review existing literature concerning the effect of synbiotic foods on the composition and activity of the colonic microbiota, and efficiency of functional attributes of synbiotic foods in formulation and development of new dairy products.
The objective of the present study was to determine whether acacia gum (GUM) is a prebiotic fibre and to evaluate its intestinal tolerance in healthy subjects. The effects of increasing doses of GUM were compared to those of sucrose (SUC) on stool output, concentration of the main bacterial populations in stools, and occurrence and severity of intestinal symptoms (flatulence, bloating, abdominal cramps, diarrhoea). Ingestion of GUM 10 and 15 g/day for 10 days increased total lactic acid-producing bacteria and bifidobacteria counts in stools, without affecting total anaerobe and aerobe counts. The magnitude of this selective effect was greater in subjects with a low initial faecal concentration of bifidobacteria. Faecal digestibility of GUM was around 95% and its caloric value was estimated to range between 5.5 and 7.7 kJ/g. In addition, stool weight increased 30% because of greater faecal water content. Digestive tolerance of GUM was high and not statistically different from that of SUC up to a daily dose of 30 g. Above this dose, the main complaint was excessive flatulence. However, the mean degree of severity remained mild (<1), even at doses >50 g/day. Other intestinal events were rarely reported. Thus GUM is a very well tolerated dietary fibre with bifidogenic properties believed to benefit intestinal health.
The bifidogenic effect of inulin and oligofructose is now well established in various studies, not only in adult participants but also in other age groups. This bifidogenic shift in the composition of the colonic microbiota is likely the basis for the impact of these prebiotic compounds on various parameters of colonic function. Mainly from animal and in vitro studies and also from some human trials, there are indications, for instance, that inulin-type fructans may reduce the production of potentially toxic metabolites and may induce important immune-mediated effects. This review discusses how these changes in the composition and activity of the colonic microbiota may affect gut health in healthy people, including in those who may experience some form of gastrointestinal discomfort.
Polysaccharides with structures resembling components of dietary fiber were fermented by a number of species of anaerobic bacteria from the human colon. Some strains also fermented glycoprotein mucins. The strains that fermented the widest range of polysaccharide substrates were in the two genera Bacteroides and Bifidobacterium. Polysaccharide degrading enzymes from several Bacteroides species have been studied, and in most cases the enzyme activities were cell bound rather than extracellular. In all cases, the polysaccharide degrading enzymes were inducible rather than constitutive. Thus the metabolic activity of the flora could be altered considerably by the amount and type of fiber in the diet, even though the composition of the flora itself remained unchanged. The products of enzyme action included monosaccharides and oligosaccharides of varying chain lengths.
1. Gum arabic is a water-soluble polysaccharide resistant to human gut enzymes and thus can be described as dietary fibre.
2. Using a most-probable-number technique, estimates were made of total anaerobes and of gum-arabic fermenters in the faeces of a volunteer during a contro1 period and during addition of 10 g gum arabic/d to the diet. Using an enrichment technique, the principal bacteria able to utilize gum arabic as the only carbohydrate source were isolated and characterized.
3. Faecal samples were analysed for undegraded gum arabic and, following acid-hydrolysis, for total sugars.
4. The proportion of the faecal flora able to degrade the gum arabic polymer rose from an initial level of 6.5% to more than 50% during gum-arabic ingestion, and subsequently returned to the control level after ingestion ceased. The principal gum-arabic fermenters were species of Bucteroides and Bifdobucterium .
5. Undegraded gum arabic was not detected in any faecal sample nor were there significant differences in the level of total sugars in acid-hydrolysed faeces between gum arabic and control periods.
6. The results presented indicate a direct and rapid change in faecal flora in response to a specific change in the diet of a human volunteer.
Because the human gut microbiota can play a major role in host health, there is currently some interest in the manipulation of the composition of the gut flora towards a potentially more remedial community. Attempts have been made to increase bacterial groups such as Bifidobacterium and Lactobacillus that are perceived as exerting health-promoting properties. Probiotics, defined as microbial food supplements that beneficially affect the host by improving its intestinal microbial balance, have been used to change the composition of colonic microbiota. However, such changes may be transient, and the implantation of exogenous bacteria therefore becomes limited. In contrast, prebiotics are nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacterial species already resident in the colon, and thus attempt to improve host health. Intake of prebiotics can significantly modulate the colonic microbiota by increasing the number of specific bacteria and thus changing the composition of the microbiota. Nondigestible oligosaccharides in general, and fructooligosaccharides in particular, are prebiotics. They have been shown to stimulate the growth of endogenous bifidobacteria, which, after a short feeding period, become predominant in human feces. Moreover, these prebiotics modulate lipid metabolism, most likely via fermentation products. By combining the rationale of pro- and prebiotics, the concept of synbiotics is proposed to characterize some colonic foods with interesting nutritional properties that make these compounds candidates for classification as health-enhancing functional food ingredients.
Chemostat cultures of human faecal bacteria were used to determine the bifidogenic effect of oligofructose, a fermentable carbohydrate found in a number of plants. In single stage continuous culture, oligofructose preferentially enriched for bifidobacteria, in comparison to sucrose and inulin. This stimulatory effect was enhanced at a high dilution rate, high substrate concentration and low pH. These parameters are likely to approximate to those that occur in the proximal colon. Studies with a three-stage continuous culture model of the large intestine confirmed the bifidogenic effect of oligofructose. These in vitro data indicate that an increase in the concentration of fructose-based oligosaccharides in the diet may alter the balance of the gut microflora towards bifidobacteria, a purported health-promoting genus.
Inulin and oligofructose are a significant part of the daily diet of most of the world's population. Daily intakes for the U.S. and Europe have been estimated at up to 10 g, specifically 1-4 g for the 97th percentile in the U.S. Because both inulin and oligofructose are macroingredients, it is difficult to apply classical toxicology tests. Although some high dose animal tests have been performed, none have revealed any toxic effects. The safety of inulin and oligofructose for use in foods was evaluated by many legal authorities worldwide. As a result, both inulin and oligofructose are accepted in most countries as food ingredients that can be used without restrictions in food formulations. In the U.S., a panel of experts performed a generally accepted as safe (GRAS) Self-Affirmation Evaluation in 1992 and concluded similarly. At high doses, increased flatulence and osmotic pressure can cause intestinal discomfort. These doses vary widely from person to person and also depend on the type of food in which inulin or oligofructose is incorporated. With regard to labeling, both inulin and oligofructose are gradually being accepted as "dietary fibers" in most countries around the world. The mention of their "bifidogenic effect" on food labels has also been legally accepted in several countries.
Prebiotics are non-digestible food ingredients that target certain components within the microbiota of the human large intestine. Efficient prebiotics need to have a specific fermentation therein and thereby have the ability to alter the faecal microflora composition towards a more 'beneficial' community structure. This should occur by the stimulation of benign or potentially health promoting genera but not the harmful groups. Because of their positive attributes bifidobacteria and lactobacilli are the most frequent target organisms. Both inulin and oligofructose have been demonstrated to be effective prebiotics. This has been shown through both in vitro and in vivo assessments in different laboratories. Because of their recognised prebiotic properties, principally the selective stimulation of colonic bifidobacteria, both inulin and oligofructose are increasingly used in new food product developments. Examples include drinks, yoghurts, biscuits and table spreads. Because of the recognised inhibitory effects that bifidobacteria can exert against gut pathogens, one of the most important aspects of prebiotic ingestion is fortification of the gut flora to resist acute infections.
A prebiotic is "a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-being and health." Today, only 2 dietary nondigestible oligosaccharides fulfill all the criteria for prebiotic classification. The daily dose of the prebiotic is not a determinant of the prebiotic effect, which is mainly influenced by the number of bifidobacteria/g in feces before supplementation of the diet with the prebiotic begins. The ingested prebiotic stimulates the whole indigenous population of bifidobacteria to growth, and the larger that population, the larger is the number of new bacterial cells appearing in feces. The "dose argument" is thus not supported by the scientific data: it is misleading for consumers and should not be allowed. A prebiotic index is proposed, defined as "the increase in the absolute number of bifidobacteria expressed divided by the daily dose of prebiotic ingested."
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