Short‐term feeding of fermentable dietary fibres influences the gut microbiota composition and metabolic activity in rats

This study investigated the effects of dietary fibres on gut bacterial abundance and metabolic activity in rats fed short‐term. Faecal samples from rats fed for 7 days showed differences in the effects of dietary fibres on gut bacterial populations. Broccoli fibre, inulin, potato fibre and potato resistant starch significantly increased the faecal Bacteroides‐Prevotella‐Porphyromonas group compared with cellulose. Growth of pathogenic bacteria such as Clostridium perfringens, Escherichia coli and Enterococcus spp. was decreased significantly in rats fed barley β‐glucan, citrus pectin, inulin and broccoli fibre diets. An increase in Bifidobacterium spp. and butyric acid levels, the so‐called bifidogenic and butyrogenic effects, was observed in rats fed inulin and potato fibre diets. Organic acid concentrations and polysaccharide contents in the rat faeces confirm the fermentability of dietary fibres in the gut. This study demonstrates the positive effects of plant‐sourced dietary fibres on gut microbiota composition and metabolic activity.     

Diet-induced changes in alginate- and laminaran-fermenting bacterial levels in the caecal contents of rats

Brown algae contain soluble polysaccharides, such as alginic acid, fucoidan and laminaran. To assess the induction of dietary fiber-fermenting bacteria in the intestine, rats were fed diet containing no dietary fiber (control) or 2% w/w of the polysaccharides for 2 weeks. The levels of dietary fiber-fermenting bacteria in caecal contents were determined using decimal dilution culture containing 1% w/v of the fibers. Caecal microbiota in the rats was analyzed using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). In the culture method, 4–9 log viable cells/g caecal content of alginate-fermenting bacteria was detected in rats fed alginate, while this was not detected in rats fed the control diet. Although laminaran-fermenting bacteria were detected in control rats (4–9 log viable cells/g), the level observed in rats fed laminaran was 8 or 9 log viable cells/g. On the other hand, fucoidan-fermenting bacteria were not detected in rats fed fucoidan. DGGE analysis showed laminaran administration increased the diversity of bacterial bands. Clostridium spp. and Parabacteroides distasonis were detected as typical species in rats fed alginate and laminaran. The results indicate that the intake of soluble fermentable fibers in edible brown algae can alter the intestinal microbiota and its fermentation capacity.     

Effects of two contrasting dietary fibres on starch digestion,short‐chain fatty acid production and transit time in rats

Dietary fibres may cause dietary starch to escape digestion in the small intestine and enter the large intestine. If this results from the dietary fibres reducing the gastrointestinal transit time, those dietary fibres that reduce this the most would be expected to cause the most starch to escape digestion. We tested in rats the relative abilities of two contrasting dietary fibres, apple pectin (a soluble dietary fibre) and wheat straw (an insoluble, lignified dietary fibre), to reduce the whole gut transit time and to cause dietary starch to escape digestion. We provided male Wistar rats with a control, modified AIN‐76™ diet containing 20% fat but no dietary fibre, and with this diet containing 10% dietary fibre; the dietary fibre replaced the equivalent weight of starch in the control diet. Both dietary fibres, but particularly wheat straw, reduced the transit time compared with the fibre‐free control diet. Pectin, but not wheat straw, resulted in substantial amounts of starch in the caecal contents. This effect may result from the pectin increasing the viscosity of the digesta or causing it to gel. Large amounts of short‐chain fatty acids were found only in the caeca of rats provided with pectin. © 2000 Society of Chemical Industry     

Influence of assay conditions on the in vitro hindgut digestibility of dry matter

In vitro assays have been developed to predict dry matter digestibility (DMD) in the human colon, but there is little information on the effect of assay variables. The effect of altering pH, duration of incubation, presence of shaking during incubation and the concentration of faecal inoculum or digestive enzymes on DMD was investigated for three in vitro hindgut digestibility assays. Three mixed human diets varying in the type and ratio of soluble and insoluble dietary fibre were used as substrates. The pH, duration of incubation and the concentration of inoculum relative to substrate significantly (P > 0.05) affected predicted DMD for the two in vitro methods employing faecal inocula. The method using synthetic enzymes showed little sensitivity to alteration of assay variables and gave highly variable results and for this reason was not pursued further. Shaking did not affect (P > 0.05) digestibility for any method or diet. The different methods led to large differences in predicted hindgut DMD within each of the three diets. In vitro hindgut digestibility assay variables need to be optimised and the predicted DMD data validated against in vivo data.     

Effects of early dietary intervention with a fermentable fibre on colonic microbiota activity and mucin gene expression in newly weaned rats

Colonic microbiota composition and metabolic processes were investigated after modifying the diet immediately post-weaning in rats. Three-week old Sprague–Dawley rats were fed cellulose or inulin diet for 0 day (d), 7 d or 14 d. Real-time PCR quantification showed significantly higher colonic Bifidobacterium spp. in rats fed inulin on d7 and d14. Inulin was effective in increasing the total bacteria, Bacteroides-Prevotella-Porphyromonas group and Faecalibacterium prausnitzii, while decreasing Lactobacillus spp. Higher concentrations of short-chain fatty acids (SCFAs: acetic, butyric and propionic acids), lactic acid and succinic acid were observed in inulin-fed rats. Inulin ingestion altered colonic mucin (MUC)-3 gene expression, and increased the colon crypt depth with more goblet cells per crypt. Significant positive correlations between SCFAs concentrations and MUC3 expression were observed. Dietary supplementation with inulin altered microbiota composition, and their fermentation end-products may have aided in modifying mucin gene expression and morphology in the colon of young rats.     

Zinc bioavailability in different beans as affected by cultivar type and cooking conditions

Zinc bioavailability was studied in five cultivars of beans (Phaseolus vulgaris, L): white (Ouro Branco), black (Diamante Negro), and brown (BRS Radiante, Pérola and Talismã) cooked with or without soaking water. The cooked bean flours or ZnCO₃ were added to the test or control diets to provide 15 mg Zn/kg diet and were fed to weaning Wistar male rats for 42 days. Blood and femur were collected for analyses of plasma and erythrocyte Zn, bone weight and bone/dietary mineral ratio. Zinc bioavailability of Ouro Branco bean cooked with soaking water was higher than the other cultivars and similar to the control diet. Talismã without soaking water showed the lowest values for most of the parameters analyzed. Zinc bioavailability was not affected neither by the cooking process itself nor by the contents of phytate, tannins and dietary fiber, but it varied according to the bean cultivar and the phytate × calcium:zinc molar ratio.     

The advantage of using extrusion processing for increasing dietary fibre level in gluten-free products

Gluten-free products generally are not enriched/fortified and frequently are made from refined flour and/or starch. Such products have been found to provide lower amounts of total dietary fibre than their enriched/fortified gluten-containing counterparts.The objective of this study was to increase the level of total dietary fibre in gluten-free products by using extrusion technology and by incorporating a number of different fruits and vegetables, such as apple, beetroot, carrot, cranberry and gluten-free Teff flour cereal. The materials were added at the level of 30% into the gluten-free balanced formulation (control) made from rice flour, potato starch, corn starch, milk powder and soya flour. Different process conditions, such as water feed rate 12%, solid feed rate 15–25 kg/h, screw speed 200–350 rpm, barrel temperatures: 80 °C at feed entry and 80–150 °C at die exit were used. Pressure, material temperature and torque were monitored during extrusion runs. The relationships and interactions between raw ingredients, extrusion processing parameters and resulting extrudate nutritional and textural properties were investigated.The results of this study clearly show that extrusion technology has the potential to increase the levels of total dietary fibre in gluten-free products made from vegetables, fruits and gluten-free cereals.     

Soluble polysaccharides from flaxseed kernel as a new source of dietary fibres: Extraction and physicochemical characterization

Flaxseed (Linum usitatissimum L.) is rich in soluble and insoluble dietary fibres. Recent study in our research group discovered that the kernel of flaxseed contained about 20% (w/w) of dietary fibres, which has not been reported before. Scanning electron microscope (SEM) images revealed that flaxseed kernel dietary fibres (FKDF) are mostly in the supporting structure of the cell walls. To study the structure and physicochemical properties of FKDF, a modified sequential extraction and fractionation procedure was utilised, and five separate FKDF fractions were obtained as flaxseed kernel (FK) water-extracted polysaccharides (FK-WP), FK EDTA-extracted polysaccharides (FK-EP), FK Na₂CO₃-extracted polysaccharides (FK-NP), FK 1 M KOH-extracted polysaccharides (FK-KPI), and FK 4 M KOH-extracted polysaccharides (FK-KPII). FKDF fractions were all water-soluble. The average molecular weight of FK-WP was 486 kDa, FK-EP 593 kDa, FK-NP 704 kDa, FK-KPI 770 kDa, and FK-KPII 1660 kDa. Monosaccharide compositions were different among FKDF fractions; alkaline solution extracted FKDF fractions had relatively higher percentage of arabinose, but relatively lower content of glucose compared with FK-WP and FK-EP. All FKDF fractions had the ability to lower the surface tension of water, among which FK-KPI exhibited the best surface activity. Rheological properties showed that FKDF fractions had low viscosity and 2% (w/v) FKDF water solution exhibited viscoelastic behaviour at 25 °C. Those findings could benefit the related food industries for providing healthier and more value-added flaxseed products.     

Jaboticaba Pomace Powder Obtained as a Co-product of Juice Extraction: A Comparative Study of Powder Obtained from Peel and Whole Fruit

This study presents the evaluation of an emergent co-product generated during the production of jaboticaba juice by steam drag: the jaboticaba pomace. A comparison of physicochemical, technological and morphological properties of the jaboticaba powders obtained from the pomace, from the whole fruit and from the peel was performed. All the powder samples underwent the same processing: freeze-drying, milling and sieving. The powders appeared reddish, with an average diameter of approximately 64.83–103.51 μm and pH values of 3.45–3.74, water activity of 0.3133–0.3270, water holding capacity of 2.63–4.28 g H₂O/g and oil holding capacity of 2.79–2.98 g oil/g. Differential scanning calorimetry analysis showed that the endothermic peak temperature was 158.9–164.4 °C. Proximate composition analysis showed a large amount of total dietary fibre and insoluble dietary fibre in jaboticaba pomace (20.54 and 16.42 g/100 g, respectively), while jaboticaba peel had a good amount of soluble dietary fibre (10.72 g/100 g). Jaboticaba pomace had a large quantity of phenolic compounds (43.39 mg GAE/g d.w.), especially monomeric anthocyanin (3.92 mg cyanidin-3-glucoside/g d.w.), compared to the whole fruit. Jaboticaba pomace is valuable due to its high phenolic content (2.5 times higher than the whole fruit) and total dietary fibre content (2.2 times higher than the whole fruit). The results obtained in this study reinforce the idea that this co-product could be re-used in the development of functional ingredients and show that the industrialisation of these materials is one possible alternative for food diversification. Pomace powder could be added to many types of foods, such as cereals, snacks, drink mixes, and breads, or could be used for pharmaceuticals, such as slow-release antioxidants in packaging films.     

Influence of dietary vitamin C and selenium,alone and in combination,on the composition and oxidative stability of meat of broilers

Information on the combined effect of dietary vitamin C and Se on the composition and oxidative stability of meat of broilers is not available in the literature. In the present experiment, male broiler chickens were fed a maize–wheat–soya diet supplemented with vitamin C at 280 and 560 mg/kg of diet, and Se (sodium selenite or selenised yeast; Se) at 0.3 mg/kg for 5 weeks. After slaughter, samples of thigh meat were analysed. The supplementation of diets with vitamin C or Se increased the protein concentration of the meat at the expense of fat. Vitamin C supplementation increased the vitamin C content of the meat in a dose-dependent manner and decreased the vitamin A concentration in the meat of broilers fed diets with sodium selenite or without a Se supplement. In the meat of the broilers that were fed these diets, the vitamin C decreased the lipid oxidation in meat that was stored for 5 days. No sparing effect of vitamin C was apparent on the amount of vitamin E in the meat. Selenised yeast was more effective in the enrichment of meat with Se than was selenite. Both Se sources increased the activity of glutathione peroxidase and the oxidative stability of the meat.     

The potential of cholecalciferol and 25-hydroxyvitamin D3 enriched diets in laying hens,to improve egg vitamin D content and antioxidant availability

Sixty Hy-line brown hens were randomly assigned to four barns (n = 4) to investigate the effects of cholecalciferol (vitamin D₃) versus 25-hydroxyvitamin D₃ (25-OH-D₃) enriched diets on egg vitamin D concentration, antioxidant activity and egg quality parameters. Experimental design was a 4 × 4 Latin square consisting of 4 experimental treatments and 4 experimental periods. The treatments were (1) 1500 IU of vitamin D₃ (2) 3000 IU of vitamin D₃ (3) 1500 IU of vitamin D₃ and 37.5 μg of 25-OH-D₃ (4) 75 μg of 25-OH-D₃ per kg of feed. Hens offered 75 μg of 25-OH-D₃ had a higher (P < 0.05) total vitamin D egg yolk content (5.06 μg/egg), and antioxidant activity compared to other dietary treatments. The results demonstrates that the enrichment of hen diets with 25-OH-D₃ may be a useful approach and may contribute between 25 and 33% towards total vitamin D daily requirements while also improving antioxidant status of eggs.Industrial relevanceVitamin D deficiency is now regarded as a major issue in northern Europe and has been described as a pandemic. A growing interest in vitamin D food fortification in northern Europe to satisfy the current dietary intake recommendations has been observed. The use of a bio-addition approach for increasing vitamin D intake through biofortification of livestock feeds attracts attention. Enrichment of the hen's diet with vitamin D may also supply additional benefits of increasing antioxidant activity. This increase in antioxidant activity may have the ability to increase food quality and extend the shelf life. This study explores the effect of vitamin D enriched diets fed to laying hens on vitamin D egg yolk content and antioxidant activity in the egg. These enriched diets could demonstrate that enrichment of hen diets with 25-hyroxvitamin D₃ may be a useful approach for tackling low vitamin D intakes and improving antioxidant capacity of eggs.     

Addition of seaweed (Laminaria digitata) extracts containing laminarin and fucoidan to porcine diets: Influence on the quality and shelf-life of fresh pork

A seaweed extract containing laminarin (L) and fucoidan (F) (L/F) was manufactured from brown seaweed (Laminaria digitata) in spray-dried (L/F-SD) and wet (L/F-WS) forms. The effect of supplementation of pig diets with L/F-SD and L/F-WS (L, 500 mg/kg feed; F, 420 mg/kg feed) for 21 days pre-slaughter, on quality indices of fresh M. longissimus dorsi (LD) steaks was examined. Susceptibility of porcine liver, heart, kidney and lung tissue homogenates to iron-induced (1 mM FeSO₄) lipid oxidation was also investigated. Dietary supplementation with L/F did not increase plasma total antioxidant status (TAS). In LD steaks stored in modified atmosphere packs (80% O₂:20% CO₂) (MAP) for up to 15 days at 4 °C, muscle pH, surface colour (CIE ‘L*’ lightness, ‘a*’ redness and ‘b*’ yellowness values) and microbiology (psychrotrophic and mesophilic counts, log CFU/g pork) were unaffected by dietary L/F. In general, levels of lipid oxidation (TBARS, mg MDA (malondialdehyde)/kg pork) followed the order: C > LF-SD > L/F-WS. A statistically significant reduction in lipid oxidation (P < 0.05) was observed in LD steaks from 75% of pigs (n = 6) fed with L/F-WS compared to controls. Iron-induced lipid oxidation increased in liver, heart, kidney and lung tissue homogenates over the 24 h storage period and dietary L/F-WS reduced lipid oxidation to the greatest extent in liver tissue homogenates. Results demonstrate potential for the incorporation of marine-derived bioactive antioxidant components into muscle foods via the animal's diet.     

Prediction of fatty acid composition using a NIRS fibre optics probe at two different locations of ham subcutaneous fat

NIR technology was used to analyze the fatty acid composition of fat tissue from conjugated linoleic acid fed pigs by direct application of a fibre optics probe on two different locations of subcutaneous fat. One hundred and fifty-three pigs were fed three different diets and the fatty acid profile of subcutaneous fat from Gluteus medius was analyzed using gas chromatography and FT-NIR in a longitudinal and transversal cut. Spectra were acquired using a Bruker Optics Matrix-F duplex spectrometer equipped with a fibre optics probe (IN-268-2). Total saturated, monounsaturated and polyunsaturated together as well as oleic and stearic fatty acids were predicted accurately (R² > 0.70), myristic, and linoleic fatty acids were predicted with lower accuracy (0.60 < R² < 0.70), while palmitic, asclepic and α-linolenic fatty acids were poorly predicted (R² < 0.60). Results indicated that NIR technology has potential as a rapid tool to discriminate carcasses from animals fed diets with different fatty acid composition by a direct measurement on the fat from the ham.     

Consumption of highly processed foods: Effects on bioavailability and status of zinc and copper in adolescents

The effects of consuming diets with different Maillard reaction products (MRP) content on zinc and copper bioavailability and status were examined. In a 2-week randomised 2-period crossover trial, 18 male adolescents consumed two diets, named white diet (WD) and brown diet (BD), which were poor and rich in MRP, respectively. A 3-day balance was performed at the end of each period and fasting blood samples were collected. Zinc bioavailability did not vary significantly between the diets (%WD: 21.0 ± 5.0, %BD: 15.1 ± 5.1), but BD consumption increased copper faecal excretion (~ 1.8-fold) and significantly decreased its bioavailability (~ 3.0-fold). Biochemical parameters related to zinc metabolism remained unaltered whereas copper in serum and erythrocytes significantly decreased after consumption of the BD (72.47 ± 2.42 μg/dl and 0.93 ± 0.01 μg/ml in serum and erythrocytes with WD compared to 65.87 ± 3.11 μg/dl and 0.84 ±0.02 μg/ml with BD). The present results suggest that the high presence of MRP in the diet does not affect zinc but negatively affects copper bioavailability. As both minerals are essential trace elements involved in adolescents' growth and development, possible long-term effects of excessive MRP intake during adolescence warrant attention.     

Some effects of fibre and starch on the determination of protein quality

An assessment was carried out of the effects of an increase in the amount of fibre, as cellulose, and of a replacement of maize starch by potato starch in diets containing egg albumen as the sole protein, on the determination of true digestibility (TD) and biological value (BV). An increase in the fibre content of the diet at the expense of maize starch led to a rise in both fascal and urinary N excretion, with diets containing either 20 or 80 g egg albumen kg^?1. However, the response of the rats to increasing fibre concentration in the diet was different for the two levels of protein probably due to differences in dry matter intake (DMI). It was found that the conventional method of estimating metabolic faecal nitrogen (MFN) was not adequate for diets of decreasing digestibility; TD decreased by 0.35% for a rise of 1% cellulose in the diet. A more accurate method of estimating MFN was derived from a relationship between the N in the faeces and the digestibility of the diet. The increase in urinary N excretion led to a decrease of 0.41% in BV for a 1% rise in the cellulose concentration of the diet. It appears, therefore, that the ratio of digestible to indigestible matter in the diet affects the determination of protein quality. The replacement of maize starch by potato starch in the diet caused an increase in faecal N excretion and a decrease in urinary N excretion until a level of 200 g potato starch kg^-1 was reached. This affected the determination of TD and BV accordingly. An increase in the size of the caecum of the rats fed potato starch indicated that increased fermentation may have resulted in production of additional bacterial cells to be excreted in the faeces. Thus, both the amount of fibre and the type of starch in the diet affect the determination of protein quality.     

Hypocholesterolemic effect of dietary evening primrose (Oenothera paradoxa) cake extract in rats

The objective of this study was to determine the effects of dietary evening primrose cake extract (E) on the lipid indices and lipid peroxidation products in growing rats fed cholesterol-free standard diet (S) or diets enriched with 1% cholesterol (C). All animals were divided into five groups of 10 and were fed during 4 weeks experimental diets: group (Gr) 1–standard diet (S); Gr 2–S diet supplemented with 1% E (S+1%E); Gr 3–with 1% C (S+1%C); Gr 4–S+1%C+0.5%E and Gr 5–S+1%C+1%E. Dietary E significantly decreased plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) but did not change the high density lipoprotein cholesterol (HDL-C) either in rats fed cholesterol-free or enriched-in-cholesterol diets. Plasma TC were 98.7, 81.3, 144.6, 114.5 and 99.1 mg 100 ml⁻¹, whereas LDL-C values were 19.4, 7.6, 77.2, 43.6 and 27.6 mg 100 ml⁻¹ in Groups 1–5, respectively. Supplementation of diet with E significantly elevated triglyceride and phospholipid concentrations in the liver; also 1% E with C (S+1%C+1%E) caused significant TC accumulation in the liver and elevated malondialdehyde concentrations in plasma and erythrocytes. In conclusion, this study demonstrates, for the first time, that evening primrose cake extract (E) possesses strong hypocholesterolemic action. Its antioxidative properties, especially in animals loaded with dietary cholesterol, are less clear and need further studies..     

Supplementation of Copper as Copper Sulfate or Copper Proteinate for Growing Calves Fed Forages Containing Molybdenum

Holstein calves (age > 12 wk old) were assigned to dietary treatments of 1) no supplemental copper, 2) copper proteinate, or 3) copper sulfate. The copper supplements were incorporated into premixes and added to a pelleted concentrate. The concentrates were fed at 1.8 kg per head per d and contained 5, 19, or 19 ppm copper and .6 ppm molybdenum by analysis. All calves were fed a grass hay free-choice, which contained 1 ppm copper and 5 ppm molybdenum. Ratios of copper to molybdenum were .9, 2.8, and 2.8 for diets 1, 2, and 3, respectively. Copper concentrations in plasma were significantly greater at wk 12 in calves fed copper proteinate than control or calves supplemented with copper sulfate. Liver copper also was higher at wk 12 in calves fed copper proteinate. Final body weights, plasma zinc, plasma iron, hemoglobin, and hematocrit were not affected by treatment. Bioavailability of dietary copper from copper proteinate was greater than from copper sulfate for calves fed diets containing molybdenum.     

Effect of pH and level of concentrate in the diet on the production of biohydrogenation intermediates in a dual-flow continuous culture

Milk fat depression in cows fed high-grain diets has been related to an increase in the concentration of trans-10 C_18:1 and trans-10,cis-12 conjugated linoleic acid (CLA) in milk. These fatty acids (FA) are produced as a result of the alteration in rumen biohydrogenation of dietary unsaturated FA. Because a reduction in ruminal pH is usually observed when high-concentrate diets are fed, the main cause that determines the alteration in the biohydrogenation pathways is not clear. The effect of pH (6.4 vs. 5.6) and dietary forage to concentrate ratios (F:C; 70:30 F:C vs. 30:70 F:C) on rumen microbial fermentation, effluent FA profile, and DNA concentration of bacteria involved in lipolysis and biohydrogenation processes were investigated in a continuous culture trial. The dual-flow continuous culture consisted of 2 periods of 8 d (5 d for adaptation and 3 d for sampling), with a 2 × 2 factorial arrangement of treatments. Samples from solid and liquid mixed effluents were taken for determination of total N, ammonia-N, and volatile fatty acid concentrations, and the remainder of the sample was lyophilized. Dry samples were analyzed for dry matter, ash, neutral and acid detergent fiber, FA, and purine contents. The pH 5.6 reduced organic matter and fiber digestibility, ammonia-N concentration and flow, and crude protein degradation, and increased nonammonia and dietary N flows. The pH 5.6 decreased the flow of C_18:0, trans-11 C_18:1 and cis-9, trans-11 CLA, and increased the flow of trans-10 C_18:1, C_18:2n-6, C_18:3n-3, trans-11,cis-15 C_18:2 and trans-10,cis-12 CLA in the 1 h after feeding effluent. The pH 5.6 reduced Anaerovibrio lipolytica (32.7 vs. 72.1 pg/10 ng of total DNA) and Butyrivibrio fibrisolvens vaccenic acid subgroup (588 vs. 1,394 pg/10 ng of total DNA) DNA concentrations. The high-concentrate diet increased organic matter and fiber digestibility, nonammonia and bacterial N flows, and reduced ammonia-N concentration and flow. The high-concentrate diet reduced trans-11 C_18:1 and trans-10 C_18:1, and increased C_18:2n-6, C_18:3n-3 and trans-10,cis-12 CLA proportions in the 1 h after feeding effluent. The increase observed in trans-10,cis-12 CLA proportion in the 1 h after feeding effluent due to the high-concentrate diet was smaller that that observed at pH 5.6. Results indicate that the pH is the main cause of the accumulation of trans-10 C_18:1 and trans-10, cis-12 CLA in the effluent, but the trans-10,cis-12 CLA proportion can be also affected by high levels of concentrate in the diet.     

In vitro starch digestion kinetics of diets varying in resistant starch and arabinoxylan compared with in vivo portal appearance of glucose in pigs

The current study was undertaken to investigate the relationship between the in vitro starch digestion kinetics and the in vivo portal glucose appearance in pigs used as models for humans. In vivo data were obtained from a previous study where the portal glucose appearance was obtained from six catheterised pigs equipped with permanent catheters in an artery and the portal vein and with a flow probe attached to the portal vein for monitoring the blood flow rate. Three experimental diets were studied — a low dietary fibre (DF), western-style diet (WSD) and two high-DF diets containing resistant starch (RSD) or arabinoxylan (AXD). A modified Englyst-assay involving gradual glucose hydrolysis over a time frame of 6 h was used in vitro. The in vitro starch digestion kinetics was modelled using a mechanistic growth model (R² > 0.995), whereas the in vivo data were better described by a sigmoid Gompertz model (R² > 0.997). The estimated plateau values were higher in vitro than in vivo but the diets were similarly ranked; ~ 95% for AXD and WSD and 81.8% for RSD in vitro and ~ 86% and 76.6% for the same diets in vivo. The rate of glucose release in vitro was much faster than the portal glucose appearance in vivo (0.0347–0.0705 versus 0.0136–0.0197% starch/min) with the starch in RSD being the most slowly degradable. This difference was most likely an effect of gastric retention. In conclusion, the in vitro method ranked the three diets in a similar relative manner as in vivo but the rate of glucose release was much faster in vitro than in vivo. It was only when the starch structure set the limit for the starch hydrolysis, however, that similar relative results were obtained.     

Effects of a black rice extract (Oryza sativa L. indica) on cholesterol levels and plasma lipid parameters in Wistar Kyoto rats

This study was designed to evaluate the efficacy of an anthocyanin pigmented rice (e.g. black rice) to mitigate the onset of hypercholesterolemia in rats-fed atherogenic diets. Male Wistar (n = 10/group) rats were fed with atherogenic diets containing 0.5% cholesterol in the presence and in the absence of bile salt (e.g. 0.05% cholic acid) along with a standardized black rice extract (BRE) (e.g. 3%, w/w). All animals were individually housed in stainless steel cages and fed with the experimental diets during a 12-h period for 10 weeks. Body weights of rats were measured every week of the experiment. After 10 weeks fed on experimental diets, rats were sacrificed and plasma total cholesterol, HDL and LDL cholesterol and triacylglycerols were measured immediately. The total cholesterol (TC) content in the liver, heart and aorta, and the concentration of triacylglycerol (TAG) were measured after lipid extraction using Folch method. Rats fed with 0.5% cholesterol containing diets which also included bile salt exhibited a considerably more severe hypercholesterolemia than counterparts fed diets containing only 0.5% cholesterol. The inclusion of the BRE in diets significantly (p < 0.05) decreased the level of TC, LDL–TC and TAG in plasma of rats-fed control diets that either contained or were absent in bile salt (p < 0.05). There were no differences in HDL-level. Liver crude lipids and total cholesterol levels were also significantly (p < 0.05) decreased in experimental groups relative to the control group in both experiments. Thus, supplementation of atherogenic experimental diets with BRE effectively decreased lipid levels in hypercholesterolemic rats. In lieu of the mixture of bioactive components present in BRE, it is possible that more than one mechanism underlying this reduction in lipids is involved.