In Vitro Fermentation of Various Food Fiber Fractions

Abstract

Dietary fiber fractions (DFF) were fermented in vitro with human fecal inocula to study fiber fermentability and production of short-chain fatty acids (SCFA). Amylolytic and proteolytic enzyme treatment using the Association of Official Analytical Chemists enzymatic-gravimetric procedure reduced processed food fiber products to DFF by removing gastric enzyme-digestible (nonresistant) components. Total 24-h SCFA production from DFF decreased in the following order: fig > oat = soy > pea > apple > corn = wheat > pear. SCFA production was proportional to the fermentability of these fibers. Fermentation of DFF from fruits such as pear, apple, and fig produced low amounts of butyrate. In contrast, less acetate and more propionate and butyrate were produced by fermentation of oat and soy DFF. Major fiber constituents, resistant starch (RS), β-glucan, and pectin were also fermented. RS, isolated from starch, produced acetate more slowly than the starch. β-Glucan produced propionate and butyrate in higher amounts than did pectin, starch, and RS. This study demonstrates that the fermentability of DFF and the production of SCFA differ among food products. In vitro fermentation of DFF is useful in estimating SCFA production in the human colon. Keywords: Dietary fiber fractions; fermentation; short-chain fatty acids

Dietary supplementation with β-glucan enriched oat bran increases faecal concentration of carboxylic acids in healthy subjects

“…Different types of indigestible carbohydrates give rise to different amounts and patterns of CAs during colonic fermentation, and it may therefore be possible to regulate the CA formation by diet. The CAs formed may depend on for example the monomeric composition of the carbohydrates, the type of linkages between the carbohydrate monomers, their solubility and their molecular weight (Berggren et al, 1993;Casterline et al, 1997;Bird et al, 2000;Karppinen et al, 2000;Henningsson et al, 2002Henningsson et al, , 2003Nilsson and Nyman, 2005). Studies examining CA formation have mainly been conducted in vitro by using human faecal inocula, or in vivo using animal models.…”

Short-chain fatty acid formation at fermentation of indigestible carbohydrates

“…Although the relative proportion of the organic end products from fermentation may vary, acetate is the major anion. Pectin is aparticularly good source for acetic acid (48,49), whilst arabinogalactan and guar gum are the poorest sources (48,50,51). By contrast, arabinogalactan and guar gum have been shown to give high amounts of propionic acid.…”

“…Butyric acid production varies over a wide range. Starches have been shown to give high proportions of butyric acid in vitro (49,50,52). In humans it has been demonstrated that administration of an a-amylase inhibitor, acarbose, to subjects resulted in enhanced butyric acid in faeces, measured either as concentration or as percentage of total SCFAs (53).…”

“…A prolongation of the adaptation (6 w) did not have any further effect on butyric acid proportion. P-glucans and raffinose are other substrates that have been shown to give high amounts of butyric acid upon fermentation (48,49,52).…”

Influence of the type of indigestible carbohydrate on plasma and urine short-chain fatty acid profiles in healthy human volunteers

“…The amount of substrate reaching the colon may have been similar in both occasions; however, the profile of enriched SCFA in plasma differed depending on the test meal administered. On the basis of several studies suggesting that RS is a good source for butyrate production (Weaver et al, 1992;Casterline et al, 1997;De Schrijver et al, 1999;Brouns et al, 2002), we assumed a higher colonic 13 C-butyrate production after the barley kernel meal than after the porridge meal. Nevertheless, plasma 13 C-butyrate concentrations were rather similar after both meals.…”