Eva Arrigoni

Resistant starch and ''the butyrate revolution''

Abstract Early epidemiological studies indicated that populations that consume a high proportion of non-starch polysaccharide (NSP) dietary fibre (DF) in their daily diet suffer less from gastrointestinal diseases, in particular colorectal cancers, than populations that consume diets that are high in fat and protein but low in NSP fibre. In this respect, diet, by increasing the amount of vegetables and NSP DFs, has been suggested to contribute as much as 25–35% to risk reduction for colorectal cancer. A reduction of fat intake may further reduce the risk by 15–25%. Based on these observations, DFs and substances that are part of the fibre complex such as antioxidants, flavonoids, sulphur containing compounds and folate have been proposed as potentially protective agents against colon cancer. However, results from controlled prospective studies in which beta-carotene and vitamin E or isolated dietary fibres were given to high risk groups showed disappointing results. There are recent indications that the regular consumption of certain subclasses of highly fermentable dietary fibre sources result in gut associated immune and flora modulation as well as a significant production of short chain fatty acids. In vitro studies as well as animal studies indicate that in particular propionate and butyrate have the potential to support the maintenance of a healthy gut and to reduce risk factors that are involved in the development of gut inflammation as well as colorectal cancer. A suggestion put forward is that beneficial effects may be obtained in particular by the consumption of resistant starch (RS) because of the high yield of butyrate and propionate when fermented. These SCFA are the prime substrates for the energy metabolism in the colonocyte and they act as growth factors to the healthy epithelium. In normal cells butyrate has been shown to induce proliferation at the crypt base, enhancing a healthy tissue turnover and maintenance. In inflamed mucosa butyrate stimulates the regeneration of the diseased lining of the gut. In neoplastic cells butyrate inhibits proliferation at the crypt surface, the site of potential tumour development. Moreover, models of experimental carcinogenesis in animals have shown the potential to modify a number of metabolic actions and steps in the cell cycle in a way that early events in the cascade of cancer development may be counteracted while stages of progression may be slowed down. The present review highlights a number of these aspects and describes the metabolic and functional properties of RS and butyrate.

Influence of different types of thermal treatment on the chemical composition and physical properties of wheat bran

The purpose of the present investigation was to submit commercially available wheat bran to various thermal treatments and to measure the resulting effects on the functional properties. Water uptake, water-binding capacity, rheological behaviour in the Farinograph and oil absorption of boiled, steam-cooked, autoclaved, roast, micronised and extruded bran were determined. The water uptake of the modified samples was increased, compared with that of the untreated bran. Only boiling affected the water-binding capacity significantly. The largest effects of the thermal modifications were rheological changes as observed in the Farinograph. Doughs, consisting of 80% patent flour and 20% wheat bran, showed a diminished maximum resistance and a prolonged mixing time compared with a standard dough with long patent flour. Wet heat treatments altered the surface of the wheat bran, resulting in a change in the oil absorption capacity.

Mind the gap—deficits in our knowledge of aspects impacting the bioavailability of phytochemicals and their metabolites—a position paper focusing on carotenoids and polyphenols

Various secondary plant metabolites or phytochemicals, including polyphenols and carotenoids, have been associated with a variety of health benefits, such as reduced incidence of type 2 diabetes, cardiovascular diseases, and several types of cancer, most likely due to their involvement in ameliorating inflammation and oxidative stress. However, discrepancies exist between their putative effects when comparing observational and intervention studies, especially when using pure compounds. These discrepancies may in part be explained by differences in intake levels and their bioavailability. Prior to exerting their bioactivity, these compounds must be made bioavailable, and considerable differences may arise due to their matrix release, changes during digestion, uptake, metabolism, and biodistribution, even before considering dose‐ and host‐related factors. Though many insights have been gained on factors affecting secondary plant metabolite bioavailability, many gaps still exist in our knowledge. In this position paper, we highlight several major gaps in our understanding of phytochemical bioavailability, including effects of food processing, changes during digestion, involvement of cellular transporters in influx/efflux through the gastrointestinal epithelium, changes during colonic fermentation, and their phase I and phase II metabolism following absorption.

In vitro digestibility and colonic fermentability of aleurone isolated from wheat bran

Two aleurone preparations, isolated from wheat bran, with different levels of tissue purity, were compared to the wheat bran starting material. Chemical composition, in vitro digestibility and in vitro fermentability were investigated and microscopy was used to visualize morphological changes. Arabinoxylans constituted the main part of the dietary fibre fraction. However, the degree of branching was found to be lower in arabinoxylans from aleurone than in that from original bran. Due to the high fibre content, in vitro digestibility was rather low but digestible compounds were largely eliminated. In vitro fermentability using fresh human faecal material turned out to be higher in aleurone than in wheat bran. Moreover, the degree of purity of the aleurone preparations influenced the amount of fermentation products. Proportions of the main short chain fatty acids were very similar in all samples, with ratios of propionate and butyrate slightly above average compared to other dietary fibre sources. Arabinoxylans from aleurone were virtually completely degraded within 8 h, whereas with wheat bran, substantial amounts were still present after 24 h. Moreover, increasing arabinose:xylose ratios during fermentation suggested a better fermentability of arabinoxylans with a lower branching degree. Microscopic investigations confirmed the better fermentability of aleurone compared to wheat bran. In addition, a specific breakdown pattern of aleurone cell walls could be observed.

Changes in the pectic substances of apples during development and postharvest ripening: Part 2: Analysis of the pectic fractions

Pectic material was extracted from the alcohol-insoluble residues of apples during growth on the tree and at different stages of ripening during postharvest storage. Three pectic fractions, soluble in the chelating agent trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA) in cold dilute sodium carbonate and in sodium carbonate at room temperature, were isolated. The galacturonic acid, neutral sugar and starch content of the fractions were determined as well as the degrees of methyl esterification and acetylation of the CDTA-soluble fraction. In addition, the molecular weight distribution was examined by gel filtration chromatography. The high galacturonic acid content of the CDTA-soluble fraction was consistent with the polysaccharide being essentially linear and originating in the middle lamella. The sodium carbonate-soluble pectin had a higher rhamnose to galacturonic acid ratio, indicating that it was more highly branched. Galactose and arabinose residues were lost in the polymers from all three fractions during ripening, with the greatest loss occurring from the sodium carbonate-soluble fractions. At the same time, the pectins became less polydisperse and shifted towards higher molecular weights. It seems that during development there is a dynamic turnover with new pectic polymers, which contain fewer neutral sugars, but are of high molecular weight, appearing in the middle lamella and primary cell wall.

Chemical composition and physical properties of modified dietary fibre sources

Abstract The influence of thermal treatments on the chemical composition and the physical properties of yellow pea hulls, apple pomace and depectinised apple pomace were determined. The chemical composition of yellow pea hulls and apple pomace was altered only slightly. With depectinised apple pomace, however, the heat treatments led to a significant loss of the total dietary fibre (TDF) content. Water uptake, water binding capacity, rheological behaviour in the farinograph and oil absorption were determined before and after boiling, autoclaving and extrusion cooking. The physical properties of all samples were considerably affected by the thermal modifications. Whilst in cooked dietary fibre samples the water uptake, the water binding capacity and the oil absorption was always enhanced, the influence of autoclaving and extrusion cooking on the physical properties depended very much on the dietary fibre source. Yellow pea hulls showed unchanged or slightly increased values, while the results for the two apple pomace preparations were lower compared with the untreated samples. The differences in the farinogramsiwere less obvious since the dietary fibre content in the dough mixtures was only in the range of 10–20%.

Fermentability of Oat and Wheat Fractions Enriched in β-Glucan Using Human Fecal Inoculation

ABSTRACT Fermentation by human fecal bacteria of fractions of wheat bran prepared by preprocessing technology were examined and compared with a β-glucan-rich oat bran and a purified β-glucan (OG). The wheat fractions were essentially a beeswing bran (WBA), mainly insoluble dietary fiber, and an aleurone-rich fraction (WBB) containing more soluble fiber and some β-glucan (2.7%). The oat bran (OB) had more endosperm and was very rich in β-glucan (21.8%). Predigestion of WBB and OB to mimic the upper gastrointestinal (GI) tract gave digested wheat bran fraction B (WBBD) and digested oat bran (OBD), respectively. These predigested fractions were fermented in a batch technique using fresh human feces under anaerobic conditions. Changes in pH, total gas and hydrogen production, short chain fatty acids (SCFA), and both soluble and insoluble β-glucan and other polysaccharide components, as determined from analysis of monosaccharide residues, were monitored. Fractions showed increasing fermentation in the order WB...

Human gut microbiota does not ferment erythritol.

Erythritol, a naturally occurring polyol, is gaining attention as a bulk sweetener for human nutrition. Industrially, it is produced from glucose by fermentation. From various studies it is known to be non-cariogenic. Moreover, it is rapidly absorbed in the small intestine and quantitatively excreted in the urine. Only about 10 % enters the colon. Earlier in vitro experiments showed that erythritol remained unfermented for a fermentation period of 12 h. In order to investigate whether fresh human intestinal microbiota is able to adapt its enzyme activities to erythritol, a 24 h lasting fermentation was carried out under well-standardised in vitro conditions. For comparison maltitol, lactulose and blank (faecal inoculum only) were incubated as well. Fermentation patterns were established by following total gas production, hydrogen accumulation, changes in pH value, SCFA production and substrate degradation. Taking all fermentation parameters into account, erythritol turned out to be completely resistant to bacterial attack within 24 h, thus excluding an adaptation within that period. Since under in vivo conditions more easily fermentable substrates enter the colon continuously, it seems very unlikely that erythritol will be fermented in vivo.

In vitro fermentability of a commercial wheat germ preparation and its impact on the growth of bifidobacteria

Abstract The wheat germ product Biogerm® was enzymatically digested and subjected to small scale in vitro fermentations with fresh human faeces under anaerobic conditions. Raftiline® and lactulose served each as a control substrate in parallel fermentations. Total gas and short chain fatty acid (SCFA) production from Biogerm® was found to be slower within the first few hours compared to the control substrates, but reached similar end values after 24 h. Moreover, the SCFA pattern of Biogerm® was characterised by high propionate proportions. In order to investigate the effect of Biogerm® on the growth of bifidobacteria, total bacteria and bifidobacteria were enumerated by in situ hybridisation techniques. The wheat germ preparation increased the proportion of bifidobacteria from 15 up to 24% of total bacteria in the faecal matter. Conclusively, Biogerm® has an impact on the growth of bifidobacteria in an in vitro environment containing the human faecal microflora.

Rapid high performance screening method using UHPLC-MS to quantify 12 polyphenol compounds in fresh apples

A rapid screening method for quantifying different polyphenol compounds in fresh apples using UHPLC-MS was developed. Apples were frozen and ground to a fine powder, which was extracted with methanol containing 1% formic acid. The resulting supernatant was used directly for total polyphenol determination with the Folin–Ciocalteu reagent and after dilution and filtration for UHPLC-MS analysis. Quantification of individual polyphenols was achieved with an external standard calibration. Four different apple cultivars were analysed with both methods. Braeburn contained the lowest amount of polyphenols (calculated as sum of polyphenols by UHPLC-MS) followed by Gala Galaxy and Golden Reinders with average amounts while Fuji contained the highest concentrations ranging from 24.2 to 50.0 mg per 100 g of edible fresh matter. Total polyphenol content by the Folin-Ciocalteu method showed the same trend, but was 3–4 times higher. Using the rapid high performance screening method the 12 most important polyphenols of apples (catechin, epicatechin, procyanidin B1 and B2, chlorogenic acid, coumaroylquinic acid, phloridzin, phloretin-xyloglucoside, quercetin-galactoside/-glucoside, rutin, quercetin rhamnoside) were quantified.